Article

Enhanced mechanical properties of self-polymerized polydopamine-coated recycled PLA filament used in 3D printing

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Abstract

Dopamine readily adsorbs onto almost all kinds of surfaces and develops cohesive strength through self-polymerization; hence, aqueous solutions of dopamine can be used as adhesives. These properties were used to prevent the degradation in the mechanical properties of recycled PLA fabricated by 3D printer. The mechanical properties of 3D printed PLA play a critical role in determining its applications. To reduce the manufacturing cost as well as environmental pollutants, recycling of 3D printed materials has attracted many attentions. However, recycling of polymeric materials causes the degradation of the mechanical properties. Our study is aimed at advancing the current knowledge on the adhesion behavior of polydopamine coatings on PLA pellets used in 3D printing process. Polydopamine was synthesized by oxidative polymerization and used to coat PLA specimens. The adhesion behavior and mechanical properties of the 3D printed specimens were evaluated by tensile tests. It was found that the mechanical properties of recycled specimen with polydopamine coating have been improved. Microstructural and chemical characterization of the coated specimens was carried out using FE-SEM, FTIR, and XPS analyses.

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... Acrylonitrile butadiene styrene (ABS), nylon, polycarbonate (PC), high density polyethylene (HDPE), high impact polystyrene (PS) and polylactic acid (PLA), polyethylene terephthalate (PET) fi laments are used for the development of products in fashion industry such as clothes, jewelry, shoes, etc. The most popular fi lament materials among them are ABS, PLA and PET [57,58]. ...
... More CO2 emissions occur. It is more brittle than ABS and more fl exible than nylon [57,58,59,60]. The glass transition temperature of PLA is 60 o C. The temperature to be used for 3 d printing with PLA is 210 o C. At higher temperature, it begins to deteriorate [58]. ...
... ABS is a derivative of petroleum, and it is considered toxic. So it is not environmentally friendly like PLA [57]. However, the glass transition temperature is much higher. ...
Article
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With the development of recent technologies, novel design strategies possibilities increase day by day. 3D printing technologies, which are also known as the additive manufacturing, are announced as the technology of today as well as the future. The aim of this study is to review current literature in terms of the types of 3D printers, the raw materials, the manufacturing processes, and design examples. It is also aimed to highlight some of the well-known brands and designers in the fashion industry which employed the 3D printers to develop their fashionable structures. The main advantage of the 3D printing technologies is to ease of the creating own design without needing help. Everyone can now be their own designer and manufacturer with this technology, thanks to 3D printers, and in a few hours, they can produce the product anywhere within the preferred color and model.
... As a 3D printing technology, fused deposition modeling (FDM) is commonly applied to fabricate complex and customized structures with high efficiency and low cost. It has been extensively used in prototyping and product manufacturing for many applications such as automatization, construction, biological engineering, and furniture Zhao et al. 2018;Oladapo et al. 2020;Zeng et al. 2020). However, the raw material for FDM is limited to thermoplastics, including acrylonitrile butadiene styrene (ABS), nylon, polycarbonate, polyethylene, and polylactic acid (PLA) (Le Duigou et al. 2016). ...
... Therefore, 3D printed PLA has been applied for tissue engineering Oladapo et al. 2020), electronics (Spinelli et al. 2019), thermal and sound absorbing materials (Papon and Haque 2018), and construction (Hinchcliffe et al. 2016;Ghaffar et al. 2018). In addition, 3Dprinted PLA products can be recycled and reprinted to fabricate structures, which have comparable properties with the one before recycling (Tian et al. 2017;Zhao et al. 2018). ...
Article
To efficiently and economically utilize a wood-plastic biocomposite, an eco-friendly biocomposite was prepared using modified poplar fiber and polylactic acid (PLA) via 3D printing technology for the first time. First, the effects of poplar fiber (0, 1, 3, 5, 7, and 9%) on the mechanical and rheological properties of the printed biocomposites were investigated. Subsequently, the printing parameters, including printing temperature, speed, and layer thickness, were optimized to obtain the biocomposite with superior properties. Finally, four printing orientations were applied to the biocomposite based on the optimized printing parameters to study the effect of filament orientation on the properties of the biocomposite. Favorable printability and mechanical properties of the biocomposite were obtained at 5% poplar fiber. The optimal printing temperature of 220 °C, speed of 40 mm/s, and layer thickness of 0.2 mm were obtained to produce the desired mechanical properties of the biocomposite with the printing orientation in a longitudinal stripe. However, the printing parameters should be chosen according to the applications, where different physical and mechanical properties are needed to achieve efficient and economical utilization of the biocomposites.
... Additive can be a chain extender or an organic peroxide, which react with the PLA residues giving rise to crosslinking, branching or chain extension reactions [78]. To improve the mechanical properties of recycled PLA, Zhao et al. proposed to use polydopamine (PDA) as adhesion promotor [79]. Mechanical properties of recycled PDA/PLA filaments obtained from extruded PDA coated PLA pellets and recycled PLA are summarized in the Table 6. ...
... Mechanical properties of recycled PLA and Recycled PDA/PLA filaments[79]. ...
... According to previous studies, vanadium can catalyze dopamine oxidation [33]. The mechanism of polydopamine formation is shown in scheme 1 [34]. In situ formation of polydopamine was observed in the presence of nanoscale 1. ...
... Additionally, the optical properties of compound 1 were investigated and Scheme 1. The mechanism of polydopamine formation [34]. the green fluorescence of nanoscale 1 upon a 365 nm excitation can be assigned to π(O)→d(V) charge transfer transitions. Nanoparticles of 1 have shown to be an efficient nano-catalyst for dopamine oxidation and polydopamine formation. ...
... The broad DTG curve confirms a large distribution of the molecular weight of the macromolecules. According to what is systematically described in the literature, this result is attributed to the mechanical recycling process, where the applied shredding forces lead to the break of the chemical bonds of the main polymeric chain [34]. This action provokes a broader distribution of polymeric chain sizes and, consequently, a larger distribution of molecular weights. ...
... With the increase in recycling cycles, the average molecular weight tends to decrease due to chain scission [34]. Concerning PMMA and HIPS, they present one single stage of degradation between 285 and 400°C and 370-485°C, respectively. ...
Article
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Mouthguards are polymeric devices recommended to be used by athletes to help prevent orofacial injuries. Some of the problems described by the athletes when using the mouthguards can be addressed by producing customized devices with thinner walls by additive processing techniques. In the present work, new polymeric materials for this application, such as poly(lactic acid) (rPLA) recycled from food packaging, poly(methyl methacrylate) (PMMA), high impact polystyrene (HIPS), and thermoplastic polyurethane (TPU), are proposed for the preparation of protective mouthguards, in alternative to the ethylene-vinyl acetate (EVA) copolymer, the current gold standard. Specimens were printed with two different thicknesses (2 mm and 4 mm) to study their influence on the final properties of the printed samples. The characterization included chemical, thermal, surface, and mechanical aspects of commercially acquired polymeric filaments and printed components. All the studied materials showed a decrease in the impact strength with increasing specimen thickness, except for TPU due to its highest deformation capacity. Compared with EVA, TPU has a similar energy absorption, while the other polymers presented higher values.
... This tested sample is milled again [48]. If the material requires any modification, in the primary case, an additional component and a binder, such as silicone oil, are added to the mixed material, followed by extrusion [52]. Polypropylene (PP), polyvinyl chloride (PVC), high-and low-density polyethylene (HDPE, LDPE), polystyrene (PS), polyethylene terephthalate (PET), and the "other" category, mostly acrylonitrile-butadiene-styrene (ABS) and polycarbonate (PC), are now being recycled globally. ...
... This tested sample is milled again [48]. If the material requires any modification, in the primary case, an additional component and a binder, such as silicone oil, are added to the mixed material, followed by extrusion [52]. ...
Article
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The rise of the COVID-19 outbreak has made handling plastic waste much more difficult. Our superior, hyper-hygienic way of life has changed our behavioural patterns, such as the use of PPE (Personal Protective Equipment), the increased desire for plastic-packaged food and commodities, and the use of disposable utensils, as a result of the fear of transmission. The constraints and inefficiencies of our current waste management system, in dealing with our growing reliance on plastic, could worsen its mismanagement and leakage into the environment, causing a new environmental crisis. A sustainable, systemic, and hierarchical plastic management plan, which clearly outlines the respective responsibilities as well as the socioeconomic and environmental implications of these actions, is required to tackle the problem of plastic pollution. It will necessitate action strategies tailored to individual types of plastic waste and country demand, as well as increased support from policymakers and the general public. The situation of biomedical plastic wastes during the COVID-19 epidemic is alarming. In addition, treatment of plastic waste, sterilisation, incineration, and alternative technologies for transforming bio-plastic waste into value-added products were discussed, elaborately. Our review would help to promote sustainable technologies to manage plastic waste, which can only be achieved with a change in behaviour among individuals and society, which might help to safeguard against going from one disaster to another in the coming days.
... However, the largest part of the research on the possibility of using plastics for 3D printing is the natural origin of PLA. The influence of multiple material recycling was studied (Zenkiewicz et al. 2009;Anderson 2017), as well as the possibility of introducing an additional strengthening component (Pillin et al. 2008;Gkartzou et al. 2017;Zhao et al. 2018b). Based on the available research, a general scheme of waste recycling for 3D printing was created (Fig. 2). ...
... The PDA coated polymer is thermal-stable up to 200°C. It possesses higher tensile strength and strain at break, and its surface exhibits higher adhesion than uncoated PLA (Zhao et al. 2018b). Anderson (2017) proposed direct recycling of the utilized PLA filament through its ground up and re-extrusion into 3D printing filament. ...
Article
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In recent times, the issue of plastic recycling has become one of the leading issues of environmental protection and waste management. Polymer materials have been found an application in many areas of daily life and industry. Along with their extended use, the problem of plastic wastes appeared because, after withdrawal from use, they became persistent and noxious wastes. The possibility of reusing polymeric materials gives a possibility of valorization-a second life-and enables effective waste utilization to obtain consumable products. The 3D printing market is a well-growing sector. Printable filaments can be made from a variety of thermoplastic materials, including those from recycling. This paper focuses on a review of the available literature on the production of filaments for 3D printers from recycled polymers as the alternative to present approach of central selective collection of plastics. The possibility of recycling of basic thermoplastic materials and the impact of processing on their physicochemical and mechanical properties were verified (Lanzotti et al. 2019). In addition, commercially available filaments produced from recycled materials and devices which allow self-production of filaments to 3D printing from plastic waste were reviewed.
... In addition, adding reinforcing materials, extruding 3D printed PLA waste into filaments and coating it with dopamine, as shown in Figure 9b, is also an effective way to enhance the mechanical properties of recycled PLA. Experiments have proved that the PLA waste coated by dopamine can effectively improve the tensile properties of PLA waste through chemical bonding, and it can be applied to the injection molding process [56]. ...
... They not only use waste products for 3D printing but also recycled waste from 3D printed products [59]. [56]; (c), (d) recycling printing process of waste PC material and the energy consumption of waste PC compared with ABS [59]; (e) distribution of fillers inside PETG [57]; (f) on the left is the second printing of the commercial PETG filament, and the right side shows the second printing of the prepared PETG blended filament [57]. ...
Article
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3D printing technology is a versatile technology. The waste of 3D printed plastic products is a matter of concern because of its impact on the circular economy. In this paper, we discuss the current status and problems of 3D printing, different methods of 3D printing, and applications of 3D printing. This paper focuses on the recycling and degradation of different 3D printing materials. The degradation, although it can be done without pollution, has restrictions on the type of material and time. Degradation using ionic liquids can yield pure monomers but is only applicable to esters. The reprocessing recycling methods can re-utilize the excellent properties of 3D printed materials many times but are limited by the number of repetitions of 3D printed materials. Although each has its drawbacks, the great potential of the recycling of 3D printed waste plastics is successfully demonstrated with examples. Various recycling approaches provide the additional possibility of utilizing 3D printing waste to achieve more efficient circular application.
... 4,5 Fortunately, the rise of economically competitive distributed manufacturing with three-dimensional (3D) printers [6][7][8][9][10] offers the potential to manufacture products close to consumers and even in their own homes with reduced environmental impacts. 11,12 The development of the opensource waste plastic extruder that produces filament for 3D printing (recyclebot) 13 offers the potential for distributed recycling 14 with an improved environmental 11,[15][16][17] as well as economic performance. 18 Due to the introduction of the open-source self-replicating rapid prototyper (RepRap), [19][20][21] the dominant technology of 3D printing is fused filament fabrication (FFF) using polylactic acid (PLA). ...
... 14,[23][24][25][26] However, PLA degrades with each cycle through the print/grind/extrude to filament/print loop. 14,23,27 This issue can be partially controlled by adding virgin PLA to recycled PLA, 14,23 coatings, 17 or carbon fiber reinforcement. 28 In addition, material extrusion 3D printers that can print directly from pellets of plastic have been developed [29][30][31][32][33] and commercialized (e.g., David, Erecto-Struder, Giga-botX, Cheetah Pro, Part Daddy). ...
Article
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Fused filament fabrication (FFF) is the most common and widespread additive manufacturing (AM) technique, but it requires the formation of filament. Fused granular fabrication (FGF), where plastic granules are directly three-dimensional (3D) printed, has become a promising technique for the AM technology. FGF could be a key driver to promote further greening of distributed recycling thanks to the reduced melt solidification steps and elimination of the filament extruder system. However, only large-scale FGF systems have been tested for technical and economic viability of recycling plastic materials. The objective of this work is to evaluate the performance of the FFF and FGF techniques in terms of technical and economical dimensions at the desktop 3D printing scale. Recycled and virgin polylactic acid material was studied by using five different types of recycling feedstocks: commercial filament, pellets, distributed filament, distributed pellets, and shredded waste. The results showed that the mechanical properties from the FGF technique using same configurations showed no statistical differences to FFF samples. Nevertheless, the granulometry could have an influence on the reproducibility of the samples, which explains that the critical factor in this technology is to assure the material input in the feeding system. In addition, FGF costs per kg of material were reduced to less than 1 €/kg compared with more than 20 €/kg for commercial recycled filament. These results are encouraging to foster FGF printer diffusion among heavy users of 3D printers because of reducing the cost associated to the filament fabrication while ensuring the technical quality. This indicates the possibility of a new type of 3D printing recycled plastic waste that is more likely to drive a circular economy and distributed recycling.
... The interface between the fibers and the matrix was not investigated in this research, but different additives or surface treatments, such as acid oxidation and plasma treatment, can be used to improve the bonding interface and processing. Zhao et al. [33] have found that the tensile strength of the PLA filament improves approx. 15% by coating the surface of the recycled PLA with bio-inspired polydopamine (PDA). ...
Article
In recent years, the growing interest in the development of 3D printing has focused more specifically on the utilization of eco-friendly, biodegradable and recycled materials. This paper presents the effect of the addition of cellulose filler on the tensile properties of filaments used in 3D printing. Cellulose-filled thermoplastic composite filaments were extruded from virgin polylactic acid (PLA), recycled acrylonitrile butadiene styrene (ABS), polystyrene (PS), and polyvinylchloride (PVC), and the effect of cellulose filler on the tensile properties of composite filaments was measured. The results revealed that the tensile properties of recycled thermoplastic filaments weakened remarkably whereas the tensile properties of the filament made of virgin PLA slightly improved. However, despite the differences in the results, it was found that cellulose-filled thermoplastic composite filaments can be produced as feedstock used in 3D printing.
... Mechanical properties of PLA printed parts have been inspected as discussed in studies [9][10] [11]. However, an in-depth analysis of wear resistance of PLA based 3D printed parts has not been discussed widely in literature. ...
... The selected filaments (ABS, PLA, and HIPS) are well-known commercial polymers that are used in 3D FDM printing and are recognized for their superior stability and printability. Moreover, most of these polymers are biocompatible (Micó-Vicent et al., 2019;Mazzanti et al., 2019;Ou-Yang et al., 2018) and have previously been used for pharmaceutical purposes (Jamróz et al., 2020;Zhao et al., 2018). In this study, the thermal analysis of the filaments (Table 1) confirmed their favorable characteristics for pharmaceutical use: all polymers presented less than 1.5% of mass loss at printing temperature as well as low water content (approximately 0.5%). ...
Article
The present study aimed to analyze how the printing process affects the final state of a printed pharmaceutical product and to establish prediction models for post-printing characteristics according to basic printing settings. To do this, a database was constructed through analysis of products elaborated with a distinct printing framework. The polymers acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), and high-impact polystyrene (HIPS) were tested in a statistically-based experiment to define the most critical printing factors for mass, mass variation, printing time, and porosity. Then, a predictive model equation was established and challenged to determine two different medical prescriptions. The factors of size scale, printlet format, and print temperature influenced printlet mass, while the printing time was impacted by size scale, printing speed, and layer height. Finally, increased printing speed leads to more porous printlets. The prescript-printed tablets showed average mass, mass variations, and porosity close to theoretical values for all filaments, which supports the adequacy of the optimized design of experiments for tablet production. Hence, printing settings can be preselected according to the desired product’s characteristics, resulting in tablets produced with higher precision than usually achieved by compounding pharmacies.
... Fuda Ning et al. [14] and Aleksandar B Stefaniak et al. [15] explored in the carbon reinforced and nanopolymer particles. Xing Guan Zhao et al. [16] demonstrated the recycling of PLA filament with polydopamine coated. ...
Article
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3D printing is one of the emerging technologies in the manufacturing sector, and polymer materials play a vital role in the raw material of the additive manufacturing sector. This research explores reducing the production time by testing and analyzing the microstructure of the different polylactic acid (PLA) filament polymer samples. For this purpose, 15 pieces of ASTM (American society for testing and materials) D638 tensile samples with polylactic acid (PLA) filaments have been used exclusively with five different sets of modified process parameters in slicing software of 3D printing technology. The results of this research reveal the best PLA filament FDM production method in terms of time, mechanical strength, and FESEM analysis comparing all the results.
... For the fused filament fabrication (FFF), the literature reports the fine recyclability of printed parts, filaments and the production of novel materials containing virgin and recycled materials in blends like Low-density Polyethylene (LDPE), High-density Polyethylene (HDPE), Polyethylene (PE), Polypropylene (PP) [27][28][29][30][31], Nylon [32,33] or even recycled tires [34]. Regarding the recycling of Polylactic Acid (PLA) filaments, research was focused more on obtaining a further insight into the mechanical properties of 3D-printed parts and showed that there is a slight reduction in the mechanical properties of 3D-printed parts using recycled materials in comparison with the ones using virgin materials [35][36][37][38][39]. ...
Article
Full-text available
Sustainability in additive manufacturing refers mainly to the recycling rate of polymers and composites used in fused filament fabrication (FFF), which nowadays are rapidly increasing in volume and value. Recycling of such materials is mostly a thermomechanical process that modifies their overall mechanical behavior. The present research work focuses on the acrylonitrile-butadiene-styrene (ABS) polymer, which is the second most popular material used in FFF-3D printing. In order to investigate the effect of the recycling courses on the mechanical response of the ABS polymer, an experimental simulation of the recycling process that isolates the thermomechanical treatment from other parameters (i.e., contamination, ageing, etc.) has been performed. To quantify the effect of repeated recycling processes on the mechanic response of the ABS polymer, a wide variety of mechanical tests were conducted on FFF-printed specimens. Regarding this, standard tensile, compression, flexion, impact and micro-hardness tests were performed per recycle repetition. The findings prove that the mechanical response of the recycled ABS polymer is generally improved over the recycling repetitions for a certain number of repetitions. An optimum overall mechanical behavior is found between the third and the fifth repetition, indicating a significant positive impact of the ABS polymer recycling, besides the environmental one.
... 8 Mechanical properties of PLA are degraded by recycling, so, for retaining the mechanical properties, the polydopamine coating was used. 9 Polycaprolactum reinforced with natural fibres (like agricultural and food processing waste) reduces the material cost and enhances its mechanical properties. Polycaprolactum reinforced with almond skin is used for packaging purpose and becomes good environmental friendly material. ...
Preprint
The almond skin powder is one of the biodegradable and biocompatible food wastes that can be used as reinforcement in polylactic acid (PLA) for preparation of biomedical scaf-folds/implants (for high mechanical performance) by fused filament fabrication. The present study deals with the melt processing of almond skin powder as reinforcement from 0 wt% to 5 wt% in the PLA matrix by twin-screw extrusion process. The results of the study suggested that reinforcing the almond skin powder as 2.5 wt% in the PLA matrix mechanically strengthens the feedstock filaments but the increase in the proportion up to 5 wt% reduces the mechanical strength to a significant level. A similar trend has been observed in differential scanning calorimeter observations for thermal stability analysis. As regard to the rheological property is concerned, the melt flow index shows a significant reduction with reinforcement of almond skin powder in PLA. The results are also supported by photomicrographic analysis (for surface properties) and Taguchi-based optimization of twin-screw extrusion process parameters (for multifactor optimization).
... In recent years, PDA has been most commonly used for biomaterials modification due to its optimal cell adhesion behaviors [36]. In addition, PDA is also an excellent adherence promoter that can greatly improve the interface binding force of dECM and biomaterials, thereby preventing their segregation that might affect the regeneration of nerves [37]. ...
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The nervous system is the part of our body that plays critical roles in the coordination of actions and sensory information as well as communication between different body parts through electrical signal transmissions. Current studies have shown that patients are likely to experience a functional loss if they have to go through a nerve repair for >15 mm lesion. The ideal treatment methodology is autologous nerve transplant, but numerous problems lie in this treatment method, such as lack of harvesting sites. Therefore, researchers are attempting to fabricate alternatives for nerve regeneration, and nerve conduit is one of the potential alternatives for nerve regeneration. In this study, we fabricated polyurethane/polydopamine/extracellular matrix (PU/PDA/ECM) nerve conduits using digital light processing (DLP) technology and assessed for its physical properties, biodegradability, cytocompatibility, neural related growth factor, and proteins secretion and expression and its potential in allowing cellular adhesion and proliferation. It was reported that PU/PDA/ECM nerve conduits were more hydrophilic and allowed enhanced cellular adhesion, proliferation, expression, and secretion of neural-related proteins (collagen I and laminin) and also enhanced expression of neurogenic proteins, such as nestin and microtubule-associated protein 2 (MAP2). In addition, PU/PDA/ECM nerve conduits were reported to be non-cytotoxic, had sustained biodegradability, and had similar physical characteristics as PU conduits. Therefore, we believed that PU/PDA/ECM nerve conduits could be a potential candidate for future nerve-related research or clinical applications.
... When considering more remanufacturing cycles, though, Cruz Sanchez et al. [37] showed that neat PLA is very prone to material degradation, as the tensile strength of 3D-printed samples deteriorated by approximately 40% after only five remanufacturing cycles. Although plenty of studies have recently investigated the processability of complex recycled regional postconsumer waste by FFF and have even recommended the use of so-called RecycleBots [38][39][40], such as blends of polyethylene [39,[41][42][43][44][45], polypropylene (PP) [44,[46][47][48][49][50], polyethylene terephthalate (PET) [49][50][51], acrylonitrile butadiene styrene (ABS) [49,52], poly(lactic acid) (PLA) [49,53], polystyrene (PS) [50], polyvinyl alcohol (PVA) [54], or polyamide (PA) [55], the effect of multiple AM and filament extrusion sequences on the processability of materials more complex than the standard FFF material PLA, which is known to be susceptible to thermal degradation [9], has not yet been studied. Moreover, neither the positive effect of thermal stabilizers on retaining mechanical strength [56] nor the degradation of a filler-matrix interface with increasing re-extrusion cycles [57] has been confirmed for advanced composites used in FFF. ...
Article
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Due to a lack of long-term experience with burgeoning material extrusion-based additive manufacturing technology, also known as fused filament fabrication (FFF), considerable amounts of expensive material will continue to be wasted until a defect-free 3D-printed component can be finalized. In order to lead this advanced manufacturing technique toward cleaner production and to save costs, this study addresses the ability to remanufacture a wide range of commercially available filaments. Most of them either tend to degrade by chain scission or crosslinking. Only polypropylene (PP)-based filaments appear to be particularly thermally stable and therefore suitable for multiple remanufacturing sequences. As the extrusion step exerts the largest influence on the material in terms of temperature and shear load, this study focused on the morphological, rheological, thermal, processing, tensile, and impact properties of a promising PP composite in the course of multiple consecutive extrusions as well as the impact of additional heat stabilizers. Even after 15 consecutive filament extrusions, the stabilized additively manufactured PP composite revealed an unaltered morphology and therefore the same tensile and impact strength as the initial material. As the viscosity of the material of the 15th extrusion was nearly identical to that of the 1st extrusion sequence, the processability both in terms of extrusion and FFF was outstanding, despite the tremendous amount of shear and thermal stress that was undergone. The present work provides key insights into one possible step toward more sustainable production through FFF.
... Recently, biomimetic hydroxyapatite (HA) has attracted scientists for its biomedical applications due to lack of limited supply, immune rejection, trauma, among other factors, which are observed in autograft or allograft sources [1,2]. Among a broad range of bioactive polymers, mussel-inspired dopamine is well known for its ability to support biomineralization after polymerization under an alkaline condition [3]. ...
Article
In this study, mussel-inspired polydopamine nanospheres (∼400nm) were synthesized via spontaneous oxidative polymerization of dopamine hydrochloride. The creation of bioactive template provided an opportunity for the biomimetic formation of hydroxyapatite layers through soaking of polymeric samples in 10 × -simulated body fluid (10 × -SBF) solution and heating microwave radiation. According to the results, microwave irradiation supported the rapid and homogeneous formation of HA on the surface of bioinspired spheres, and synthesized HA showed nearest Ca/P ratio to biological HA. In addition, Fourier transform infrared spectrum, X-ray diffraction, and atomic force microscopy tests confirmed the effectiveness of microwave rays on biomimetic mineralization. Biocompatibility of the constructs and improving cellular spreading on the HA-coated species indicated their potential for biomedical applications.
... focused the research on the mechanical properties of polyethylene terephthalate (PETG). Melenka, Cheung, Schofield, Dawson, and Carey (2016), Tian, Liu, Yang, Wang, and Li (2016), Weng, Wang, Senthil, and Wu (2016), Zou et al. (2016), Ferreira, Amatte, Dutra, and Bürger (2017),Alaimo, Marconi, Costato, and Auricchio (2017),Spiridon and Tanase (2018),and Zhao, Hwang, Lee, T. Kim, and N. Kim (2018) investigated tensile behaviour of the printed materials. ...
Article
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Additive manufacturing and modern printing technologies using polymeric materials extend the limits of industrial production and encourage applying 3D printing technique in many fields. An item of any shape and size limited only by the printing pad of particular equipment can be reproduced from a variety of materials. Polymers is the object of this research. It is known that mechanical properties of the printed elements are closely related with the manufacturing technology and vary significantly depending on the chosen production parameters such as printing temperature, velocity, and infill density. Depending on the purpose, a particular type of polymer can be used in structural analysis. This work considers mechanical properties of four thermoplastic polymeric materials widely used for prototyping: polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), high impact polystyrene (HIPS), and polyethylene terephthalate (PETG). The study is focused on two fundamental mechanical characteristics, tensile strength and modulus of elasticity, of the printed material. Dumbbell-shaped samples were made of the PLA, ABS, HIPS and PETG polymers using 3D printing technique with the same filling density (≈ 20%) of the entry level. The tensile tests were carried out in Laboratory of Innovative Building Structures at Vilnius Gediminas Technical University. The predominant effect of the printing direction on the mechanical properties of the printed materials was demonstrated in this study. The corresponding experimental characteristics are presented in the manuscript. Santrauka Modernūs gamybos procesai ir spausdinimo technologijos, naudojant polimerines medžiagas, plečia pramoninės gamybos ribas bei skatina taikyti 3D spausdinimo technologijas daugelyje sričių. Tokios technologijos leidžia gaminti bet kokios formos elementus iš įvairių medžiagų, o jų dydį lemia tik naudojamos spausdinimo įrangos galimybės. Pagrindinis šio tyrimo objektas – polimerinės medžiagos. Spausdintų elementų iš polimerinių medžiagų mechaninės savybės glaudžiai siejamos su gamybos technologija ir gali stipriai varijuoti keičiant gamybos proceso parametrus – spausdinimo temperatūrą, greitį, užpildo tankį. Polimero tipas kartu su jo mechaninėmis savybėmis parenkamas atsižvelgiant į konstrukcinį uždavinį. Šiame darbe nagrinėjamos plačiai prototipų gamyboje taikomų termoplastinių polimerinių medžiagų – polietileno rūgšties (PLA), akrilonitrilo butadieno stireno (ABS), polistireno (HIPS) ir polietileno tereftalato (PETG) – mechaninės savybės. Tyrime dėmesys skiriamas dviem pagrindinėms mechaninėms medžiagų charakteristikoms – tempiamajam stipriui ir tamprumo moduliui. Taikant 3D spausdinimo technologiją buvo pagaminti kaulo formos bandiniai iš PLA, ABS, HIPS ir PETG medžiagų. Bandinių užpildo tankis siekė ≈ 20 % paviršiaus spausdinimo sluoksnio tankio. Elementų tempimo bandymai atlikti Inovatyvių statybinių konstrukcijų laboratorijoje Vilniaus Gedimino technikos universitete. Šiame tyrime buvo parodyta spausdinimo krypties įtaka spausdintų medžiagų mechaninėms savybėms. Taip pat pateiktos eksperimentiškai nustatytos polimerinių medžiagų mechaninės savybės.
... Once the DA is oxidized to form PDA, its configuration becomes cross-linked at the phenyl sites. 40 It is noted that despite earlier studies indicated that the exact molecular configuration of PDA is still under debate, our synthetic conditions of low DA concentration and the use of Tris buffer solution suggest the PDA to adopt an eumelanin-type (polyindole) model, whose configuration is depicted in Fig. 1. [41][42][43] During the mixing of DA and PEG, the ether group from PEG is able to react with the catechol group from DA via hydrogen bonding. Subsequently, upon the polymerization of DA to form PDA, the resulting PDA/PEG mixture is consisted of PDA aggregates distributed uniformly with PEG nearby. ...
Article
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We explore dopamine (DA) and its mixtures with polyethylene glycol (PEG) or polyethylenimine (PEI) as an adhesion layer for bonding between Cu and SiO 2 . The DA is oxidized to form polydopamine (PDA) which deposits as aggregates on SiO 2 surface with notable surface roughness. After mixing with PEG or PEI, the morphology of PDA aggregates is altered considerably. Electroless Cu deposition in a mild alkaline bath is employed to deposit Cu atop the adhesion layer. The Cu films reveal an fcc lattice with (111) preferred orientation and their thickness was around 650 nm. From measurements of four-point probe, breaking strength, and tape-peeling tests, the PDA/PEG mixture reveals impressive performance serving as a strong adhesive for robust Cu bonding. We attribute the unique adhesive ability of PDA/PEG to the hydrogen bonds established between the catechol and amine groups of DA with PEG that renders desirable film formation on the SiO 2 surface for optimized interaction between Cu and SiO 2 .
... It was shown that not only was the interlayer bonding improved but also the stability of the printing process. Another relevant method found in the literature is the use of adhesion promoter, as polydopamine (PDA) that was successfully used in the 3D printing process of PLA [36]. In particular, PLA pellets were coated with PDA prior to extrusion, resulting in a 10% increase in tensile strength compared to untreated PLA. ...
Article
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3D printed neat thermoplastic polymers (TPs) and continuous fiber-reinforced thermoplastic composites (CFRTPCs) by fused filament fabrication (FFF) are becoming attractive materials for numerous applications. However, the structure of these materials exhibits interfaces at different scales, engendering non-optimal mechanical properties. The first part of the review presents a description of these interfaces and highlights the different strategies to improve interfacial bonding. The actual knowledge on the structural aspects of the thermoplastic matrix is also summarized in this contribution with a focus on crystallization and orientation. The research to be tackled to further improve the structural properties of the 3D printed materials is identified. The second part of the review provides an overview of structural health monitoring technologies relying on the use of fiber Bragg grating sensors, strain gauge sensors and self-sensing. After a brief discussion on these three technologies, the needed research to further stimulate the development of FFF is identified. Finally, in the third part of this contribution the technology landscape of FFF processes for CFRTPCs is provided, including the future trends.
... However, sometimes, the use of a fully recycled material might not be possible due to the loss of mechanical properties. In this case, it is possible to use a blend of neat and recycled materials [44]. PLA recycled with five consecutive extrusion cycles was used to prepare the nanocomposite with graphene nanoplatelets. ...
Article
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End-of-life options for plastics include recycling and energy recovery (incineration). Taking into account the polymeric waste, recycling is the intentional action that is aimed at reducing the amount of waste deposited in landfills by industrial use of this waste to obtain raw materials and energy. The incineration of waste leads to recovery of the energy only. Recycling methods divide on mechanical (reuse of waste as a full-valuable raw material for further processing), chemical (feedstock recycling), and organic (composting and anaerobic digestion). The type of recycling is selected in terms of the polymeric material, origin of the waste, possible toxicity of the waste, and its flammability. The (bio)degradable polymers show the suitability for every recycling methods. But recycling method should be used in such a form that it is economically justified in a given case. Organic recycling in a circular economy is considered to be the most appropriate technology for the disposal of compostable waste. It is addressed for plastics capable for industrial composting such as cellulose films, starch blends, and polyesters. The biological treatment of organic waste leads also to a decrease of landfills and thereby reducing methane emissions from them. If we add to their biodegradability the absence of toxicity, we have a biotechnological product of great industrial interest. The paper presents the overview on end-of-life options useful for the (bio)degradable polymers. The principles of the circular economy and its today development were also discussed.
... Only one work was identified in the included article selection which applied an additive for upgrade without any other complementary modification route. To enhance recycled PLA properties for 3D printing, Zhao et al. [63] studied the adhesion behavior of Polydopamine (PDA) coatings on PLA pellets. PLA pellets were immersed in an aqueous solution of dopamine with controlled pH. ...
Article
In a world going through a plastic waste management catastrophe with serious environmental, health, social and economic consequences, the ideal step forward would be the creation of circular flows of material which allow for the materials to remain in the value-chain for as long as possible and completing multiple lifecycles. In the case of thermoplastics, a new recycling route is emerging, made possible by Material Extrusion additive manufacturing (MEX): distributed recycling. However, similar to what happens with mainstream recycling of these materials, the thermo-mechanical processes involved, as well as other factors such as exposure to UV-light, result in waste streams with degraded properties. This way, the possible range of applications and functionality of the polymers is reduced along with number of viable lifecycles. On this scope, the application of methods to control and modify the properties of the polymers, enhancing them or compensating for the degradation in a distributed recycling context, becomes important. Not only is this an emerging, less explored recycling route with great potential to complement the existing ones, but it also presents its own set of challenges and advantages to be explored. In this work, a systematic search methodology is followed to conduct a literature review on which the current practices on the modification and control of properties of parts produced from recycled or reprocessed thermoplastics through MEX are assessed. Research gaps and opportunities are presented from the discussion of the results.
... It is noteworthy that the reduction in mechanical properties for RPLA is more intense rather than VPLA. As reported, the reduction in the molecular weight of PLA after successive recycling cycles degraded the mechanical properties of this material [28]. The heat exposure during injection molding processing on the sample preparations has led to poor molecular bonding and chain scission reactions of the polymer chain. ...
Article
Due to serious environmental pollution which is derived from petroleum-based plastic wastes, poly(lactic acid) (PLA) has been seen as a potential bioplastic to overcome the problem. It has been predicted that the usage and disposal of PLA will continuously increase in the coming years. Recycling is one of the realistic ways to minimize resources and waste management. This work intended to investigate the degradation or mechanical properties of virgin PLA (VPLA) and recycled PLA (RPLA) aged in outdoor weathering and immersed in seawater and river water. The results demonstrated that the reduction in mechanical properties was most dominant in river water, which was aged for 150 days. The findings demonstrated that the reduction in mechanical properties was higher in RPLA than VPLA. Scanning electron microscopy images showed the formation of gullies on the fracture surface of samples aged in seawater and river water. No significant differences in thermal properties were observed in RPLA and VPLA after aging in outdoor weathering. Nevertheless, a marginal decrease in the glass transition temperature (Tg), melting temperature (Tm), and degradation temperature was observed after aging in seawater and river water. The findings could help in elucidating the degradation on mechanical and thermal properties of VPLA and RPLA. The results also revealed great significance for expanding the application of VPLA and RPLA in various environments.
... The effect of thermal and mechanical degradation during mechanical recycling of plastics is different according to the (bio)degradable polymer. It is possible to use a blend of neat and recycled materials (Zhao et al., 2018). In this way the recovered (bio) degradable plastics from the sorting plants could be added to virgin one as a raw material for further production. ...
Article
In order to mitigate the social and ecological impacts of post-consumer plastic made of conventional petrochemical polymers, the market of (bio)degradable plastics have recently become more widespread. Although (bio)degradable plastics could be an environmentally friendly substitute of petrochemical ones, the consequences of their presence in the waste management system and in the environment (if not correctly disposed) are not always positive and plastic pollution is not automatically solved. Consequently, this work aims to review how plastic (bio)degradability affects the municipal solid waste management cycle. To this end, the state-of-the-art of the intrinsic (bio)degradability of conventional and unconventional petrochemical and bio-based polymers has been discussed, focusing on the environment related to the waste management system. Then, the focus was on strategies to improve polymer (bio)degradability: different types of eco-design and pre-treatment approach for plastics has been investigated, differently from other works that focused only on specific topics. The information gathered was used to discuss three typical disposal/treatment routes for plastic waste. Despite many of the proposed materials in eco-design have increased the plastics (bio)degradability and pre-treatments have showed interesting results, these achievements are not always positive in the current MSW management system. The effect on mechanical recycling is negative in several cases but the enhanced (bio)degradability can help the treatment with organic waste. On the other hand, the current waste treatment facility is not capable to manage this waste, leading to the incineration the most promising options. In this way, the consumption of raw materials will persist even by using (bio)degradable plastics, which strength the doubt if the solution of plastic pollution leads really on these materials. The review also highlighted the need for further research on this topic that is currently limited by the still scarce amount of (bio)degradable plastics in input to full-scale waste treatment plants.
... In the presence of PBO, the recycled polymer partially recovers its tensile properties, as observed by the increases in both tensile modulus (+13%) and tensile strength (+121%), when compared with rPLA. Figure 5 presents the stress-strain curves for all the formulations of each recycling chain that highlight the fragile behavior of the material demonstrated by the absence of plastic deformation. The brittle nature of this grade of PLA represents the major constrain for the development of a multi-processing approach based on FFF, since the feedstock material for this technology has to be flexible enough in order to be continuously pushed by the machine towards the print head [45]. Moreover, the tendency for the recovery of the tensile properties after chain extension is evident in the rPLA+PBO curve, which is in agreement with several reports from the literature [23,46,47]. ...
Article
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As additive manufacturing (AM) technologies have been gaining popularity in the plastic processing sector, it has become a major concern to establish closed-loop recycling strategies to maximize the value of the materials processed, therefore enhancing their sustainability. However, there are challenges to overcome related to the performance of recycled materials since, after mechanical recycling, the molecular degradation of thermoplastics shifts their performance and processability. In this work, it was hypothesized that the incorporation of a chain extender (CE) during the reprocessing would allow us to overcome these drawbacks. To attest this conjecture, the influence of 1,3-Bis(4,5-dihydro-2-oxazolyl)benzene (PBO), used as a CE, on mechanical, thermal, and rheological properties of polilactic acid (PLA) was studied. Furthermore, a closed-loop recycling system based on Fused Filament Fabrication (FFF) was attempted, consisting of the material preparation, filament extrusion, production of 3D components, and mechanical recycling steps. PBO partially recovered the recycled PLA mechanical performance, reflected by an increase in both tensile modulus (+13%) and tensile strength (+121%), when compared with recycled PLA without PBO. Printability tests were conducted, with the material’s brittle behavior being the major constraint for successfully establishing a closed-loop recycling scheme for FFF applications.
... Polydopamine (PDA) is one of the ideal choices as an adherence promoter to prevent segregation of dECM and substrates, and it can also be used to improve the interface binding strength of dECM and substrates [18]. Dopamine (DA) is a small molecule which is able to mimic the adhesive protein of marine mussels. ...
Article
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Although autologous nerve grafting remains the gold standard treatment for peripheral nerve injuries, alternative methods such as development of nerve guidance conduits have since emerged and evolved to counter the many disadvantages of nerve grafting. However, the efficacy and viability of current nerve conduits remain unclear in clinical trials. Here, we focused on a novel decellularized extracellular matrix (dECM) and polydopamine (PDA)-coated 3D-printed poly(ε-caprolactone) (PCL)-based conduits, whereby the PDA surface modification acts as an attachment platform for further dECM attachment. We demonstrated that dECM/PDA-coated PCL conduits possessed higher mechanical properties when compared to human or animal nerves. Such modifications were proved to affect cell behaviors. Cellular behaviors and neuronal differentiation of Schwann cells were assessed to determine for the efficacies of the conduits. There were some cell-specific neuronal markers, such as Nestin, neuron-specific class III beta-tubulin (TUJ-1), and microtubule-associated protein 2 (MAP2) analyzed by enzyme-linked immunosorbent assay, and Nestin expressions were found to be 0.65-fold up-regulated, while TUJ1 expressions were 2.3-fold up-regulated and MAP2 expressions were 2.5-fold up-regulated when compared to Ctl. The methodology of PDA coating employed in this study can be used as a simple model to immobilize dECM onto PCL conduits, and the results showed that dECM/PDA-coated PCL conduits can as a practical and clinically viable tool for promoting regenerative outcomes in larger peripheral nerve defects.
... Another advantage is the minimization of the waste or even causing no waste. Possibility of using recycled filaments have also taken attraction due to environmental and cost considerations [4,5]. ...
Article
Parts produced by FDM (fused deposition modelling) technique, where polymer filaments are used, are anisotropic and their properties vary depending on the printing parameters, one of which is raster angle. In this study, the effects of this parameter on the tensile and the surface roughness properties were investigated. It was determined that the ultimate tensile strength (UTS) decreased with increasing raster angle; hence, 0° raster angle where tensile loading direction is parallel to the raster yielded the highest strength. Besides ±45° raster angle resulted the most ductile behaviour with the highest fracture strains. Fracture occurred due to raster failure for 0° raster angle but for 90° raster angle, it was due to the failure of the interlayer raster bonds. In the case of ±45°, both of the failure mechanisms were effective. Surface roughness values increased up to 7 µm when measurement was perpendicular to the raster and dropped below 1 µm when it was parallel to the raster.
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This project is related to the design, fabrication and characterization of scaffold structures of different structure Using Polylactic Acid (PLA) filament, the micro bone structures are manufactured by Fused Deposition Modeling (FDM). Such morphology is chosen for its good strength, high porosity leading to good nutrient and waste diffusion, and favorable mechanical properties. Load vs Displacement values are obtained by taking compression tests for each as an overall outcome of the research, microstructure with better mechanical properties to replace the damaged bone tissues is identified.
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Biopolymers such as polydopamine and polyserotonin are effective corrosion inhibitors for the acidic-induced corrosion of steel. Despite the excellent corrosion inhibition activity of these compounds, they are not cost-effective and readily available in a large scale. In this study, for the first time, a cheap and easy methodology was followed for obtaining the modified Nettle extract including the oxidized/dimerized bio-active products such as serotonin and histamine. The Nettle extract (NTE) and oxidized Nettle extract components (ONTE) were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), UV-visible spectroscopy, and thermal gravimetric analysis (TGA). The NTE was oxidized under the alkaline condition at an ambient temperature. Finally, 600 ppm NTE and ONTE were separately added to 1 mol L⁻¹ HCl solution to reduce the steel corrosion rate. The corrosion inhibition activity of the utilized inhibitors was assessed by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) techniques. The surface features were examined by SEM, atomic force microscope (AFM), and water contact angle test. The obtained results displayed that the ONTE inhibitor resulted in the higher inhibition efficiency than the NTE. The maximum inhibition efficiency, i.e. 93.40%, was obtained in the case of the acidic solution inhibited by 600 ppm ONTE after 1.5 h. Results of the polarization test and surface analyses proved the ONTE inhibitor components adsorption on the active metal sites, especially on the anodic areas. In studying of effects of temperature on the corrosion rate of mild steel the positive effect of ONTE on the mild steel corrosion mitigation was noticed. It was shown that the adsorption of the inhibitor on the metal surface obeyed the Langmuir isotherm in both physisorption and chemisorption forms.
Article
Due to an increase in the number of applications for 3D printers, the use of thermoplastic resins such as acrylonitrile butadiene styrene (ABS) and poly lactic acid (PLA), which are typical filament materials for fused filament fabrication (FFF) type 3D printers, has also increased significantly. This trend has produced an interest in recycled filaments, both to reduce the manufacturing cost of fabricated products and to lower greenhouse gas emissions. Also, this recycling system is very useful to make functional filament such as highly conducting or high strength filament by combining carbon nanotube or polydopamine during recycling process. This study presents the design procedures of system for making recycled filaments for 3D printers from waste polymer. The system integrates four main parts for recycling filament: a shredder, which crushes polymer waste into small pieces; an extruder, which extrudes filament from the crushed pieces; a sensing and control component, which regulates the diameter of the extruded filament via a closed-loop control system, and a spooler. Additionally, the dimensional accuracy, the mechanical strength of pristine, and recycled filaments were investigated and compared.
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Application of additive manufacturing techniques (3D printing) for mass-customized products has boomed in the recent years. In pharmaceutical industry and research, the interest has grown particularly with the future scenario of more personalized medicinal products. Understanding a broad range of material properties and process behavior of the drug-excipient combinations is necessary for successful 3D printing of dosage forms. This commentary reviews recent 3D printing studies by fused deposition modeling (FDM) technique in pharmaceutical sciences, extending into the fields of polymer processing and rapid prototyping, where more in-depth studies on the feedstock material properties, modeling and simulation of the FDM process have been performed. A case study of a model oral dosage form from custom-prepared indomethacin-polycaprolactone feedstock filament was used as an example in the pharmaceutical context. The printability was assessed in the different process steps: preparation of customized filaments for FDM, filament feeding, deposition, and solidification. These were linked with the rheological, thermal, and mechanical properties and their characterization, relevant for understanding the printability of drug products by FDM.
Chapter
Three-dimensional (3D) printing or additive manufacturing is a technology that has drastically developed in recent years for numerous industrial applications. Among the 3D printing methods, fused deposition modeling requires filaments to generate 3D objects. Currently, the polymers used in this technology are synthetic ones derived from nonrenewable resources such as petroleum. Green polymers (including natural polymers) are a sustainable alternative as they are biodegradable/recyclable, nontoxic, and abundant. However, their implementation in 3D printing remains a challenge. This chapter is focused on the most popular and promising biodegradable polymers from biomass produced by microorganisms or derived from biotechnology for applications of fused deposition modeling. Their thermal, rheological, and mechanical properties are also discussed in detail.
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A novel phenolic resin (phenolic containing diphenyl oxide [named by MPF]) was synthesized and blended with poly(ethylene oxide) (PEO). In modified PEO, the shear‐thinning behavior appears and shortage modulus (G′) deviates from classic terminal behavior. Compared with PEO, there is an increase in the nucleation rate and a decrease in the growth rate of spherulites in modified PEO. A small amount of MPF plays a role of the nucleating agent of PEO. The addition of MPF into PEO makes the glass transition temperature (Tg) and thermal decomposition temperature (Td5%) of PEO higher. When the content of MPF is 2%, the Td5% of MPF/PEO is 346°C, which is much higher than that of pure PEO (240°C). When the content of MPF is 50%, Tg of PEO is up to 26°C, which is 90°C higher than that of pure PEO.
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Healing of bone fractures highly depends on the biocompatibility, stability in biological conditions, biodegradability, technical functionality, and shelf‐life of biomaterials. Metallic biomaterials offer excellent mechanical properties and biocompatibility. However, metallic bone implants result in stress shielding, release of toxic ions, excessive wear, and corrosion. Polymer materials are being explored for bone implants due to their light‐weight, biocompatibility, biodegradability, and absence of stress shielding. In the new era, additive manufacturing (AM) is being preferred due to its capability of fabricating customer specific implants with minimum material wastage. However, AM based polymer implants lack in mechanical strength and biological properties. Surface modification of polymeric substrates using coatings and incorporation of bioadditives have been regarded as alternatives for improvement of mechanical and biological properties. This review discusses about various coating techniques and gives an overview about coatings and bioadditives that can be used for enhancement of properties. From the review, it is evident that reinforcement of hydroxyapatite to polylactic acid resulted in prevention of crack growth during shape recovery cycles which can be used for self‐fitting implants. Coatings have been successful in enhancing hydrophilicity, mechanical properties, anti‐biofouling, antibacterial and anti‐coagulative properties, adhesion, proliferation, and differentiation of cells on the coated surface. This review also discusses the challenges that need to be overcome for progression in this field. Surface modification of polymeric substrates using coatings and incorporation of bioadditives has been regarded as alternatives for improvement of mechanical and biological properties. This review discusses about various coating techniques and gives an overview about coatings and bioadditives that can be used for enhancement of properties. This review also discusses the challenges that need to be overcome for progression in this field.
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Polymer 3D printing has motivated researchers toward the use of this technology for the maintenance and repair of heritage structures. This results in the exploration of different thermoplastic composites as smart materials having properties like programmable features (one-way, two-way), sensing, etc. Also, the excessive use of thermoplastics in various fields has resulted in plastic solid waste management issues. Several studies have been reported on plastic solid waste management with 3D printing. But hitherto little has been reported on the use of heritage site debris as reinforcement in the thermoplastic matrix for addressing issues of plastic solid waste management as well as for inducing controlled 4D capabilities; for better maintenance and repair of the heritage site with shorter maintenance and repair time. The present study is focused on secondary (2˚) recycling of polyvinylidene fluoride thermoplastic material by reinforcing limestone (CaCO 3 of 220 mesh size as per American Foundry Society (AFS)) collected as debris from heritage site for 3D printing applications followed by an analysis of its possible 4D capabilities. Different compositions/proportions of polyvinylidene fluoride–limestone were explored for acceptable rheological (melt flow index and viscosity), thermal (based on differential scanning calorimetry), mechanical (based on universal testing machine), and spectroscopic properties (based on attenuated total reflection-Fourier transformed infrared and photoluminescence). Piezoelectric property analysis of 3D printable composition/proportion and shape-memory effect of each composition/proportion was performed to investigate the 4D characteristics of the proposed composite. The results of the study suggest that polyvinylidene fluoride–6% limestone is a better composition/ proportion with acceptable rheological, thermal, and mechanical properties (melt flow index 2.429 g/10 min, viscosity 12742.9 Pa-s, thermal heat capacity 31.66 Jg ⁻¹ , and Young's modulus 286.56 MPa) for selected heritage structures. For 4D capabilities, piezoelectric coefficient (D 33 21.79 pC/N) and shape recovery (44.31%) have been ascertained for the best composition/ proportion selected. Further morphological analysis has been reported to support the test results.
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This article reports the experimental investigations for tensile, compressive and morphological properties of 3D printed functional prototypes composed of polylactic acid (PLA) reinforced with poly ether ketone ketone (PEKK), hydroxyapatite (HAp) and chitosan (CS). The PLA-PEKK-HAp-CS composite has wide applications as scaffolds in orthopaedics and clinical dentistry. The tensile and compressive specimens were printed (as per ASTM D638 type IV and ASTM D695) with in-house prepared feedstock filament on commercial fused deposition modelling setup by following Taguchi-based design of experiment. The results are also supported by hardness data and photomicrographs.
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Drug-eluting stent (DES) is a widely used treatment to treat atherosclerosis with the incorporation of drugs within/coated on stents. Everolimus is one of the utilised anti-proliferative drugs in developing commercialised DES. However, long-term implantation of DES has contributed to late-stent thrombosis due to rapid release of drug. Therefore, a method such as chemical cross-linking intermediate layer should be adopted in the coating development to sustain the release of drugs. In this work, everolimus was immobilised on polymeric scaffolds of poly(l-lactic acid)/poly(d-lactic acid) (PLLA/PDLA) using a polydopamine (PDA) intermediate layer for possible application in DES development. PDA is known for its stability of cross-linking bonds which is beneficial to sustain drug release. In this study, the PLLA/PDLA scaffolds were grafted with the PDA intermediate layer and immobilised with different everolimus concentrations (0.01, 0.05 and 0.10 mM). The ability of PDA to covalently immobilise everolimus was demonstrated through ATR-FTIR, XPS, SEM, AFM, wettability and everolimus quantification. While the sustain release of everolimus was verified through the analyses of drug release and coating stability. The everolimus was successfully immobilised on the PDA layer through O–N and C–O covalent linkages. The flowery-structured everolimus was observed with lower wettability and higher roughness on the greater concentration of everolimus. A sustainable drug release profile was acquired following the zero-order release profile for the 0.05 mM and 0.10 mM everolimus concentrations. The higher everolimus concentration produced greater contribution on the coating stability. These results indicate the capability of PDA to mediate the everolimus immobilisation for sustainable drug release, which is a potential approach in resolving the complication of current DES.
Article
Three‐dimensional (3D) printing is an additive manufacturing (AM) technology that has developed rapidly in the past decades due to its advantages, such as freedom of design, mass customization, waste minimization and the ability to manufacture complex structures, as well as fast prototyping. Various materials have been used in 3D printing, including metals, polymers, ceramics, concrete and their composites. The polymer's easy processing makes it stands out among many materials. As a thermoplastic polymer, polylactic acid (PLA) received much attentions as an effective biomedical material due to its proven biodegradation and biocompatibility. This review briefly summarizes the development of 3D printing technology and introduces various applications of 3D printed PLA and their composites in orthopedics. Furthermore, the current limitations and future opportunities in 3D printing are also discussed to help guide the 3D printing development and improve 3D printing strategies in orthopedic. This article is protected by copyright. All rights reserved.
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Polylactic acid (PLA) is a biodegradable polymer, which has been widely investigated for use in biomedical and packaging applications due to its excellent biodegradability, biocompatibility, non-toxicity, low cost, good stability, and thermal processability. In this work, PLA was functionalized to improve the membrane’s hydrophilicity and impart antimicrobial activity by simultaneously depositing polydopamine (PDA) and chelating Cu ²⁺ metal ions on the membrane surface. Pristine PLA films were modified via one-pot dip coating method using dopamine-copper (II) solution at different coating times (6, 12, 24 h). FTIR analysis confirmed the deposition of PDA on the modified membranes (PLA/PDA/Cu) as indicated by the presence of catechol and amine moieties on the samples. TGA results revealed the degradation of the same functional groups on PLA/PDA/Cu. The hydropilicity of PLA was significantly reduced upon coating with PDA as indicated by the decrease in the membrane’s contact angle from 96.5 ± 5.3° to 56.2 ± 4.7°. SEM images and EDS results clearly showed that copper particles were deposited on the PLA/PDA/Cu membranes (atomic % ~ up to 0.88) and coating with PDA did not alter the porous structure of the pristine PLA film. Results also demonstrated that the concentration of copper immobilized on the modified membranes increased with longer coating; thus, offering a way of tailoring the metal concentration on the membrane for its specific use. PLA/PDA/Cu membranes showed antibacterial property against the B. subtilis , which could be attributed to the chelation of Cu ²⁺ ions with the catechol moiety of the PDA coating.
Article
The almond skin powder is one of the biodegradable and biocompatible food wastes that can be used as reinforcement in polylactic acid (PLA) for preparation of biomedical scaffolds/implants (for high mechanical performance) by fused filament fabrication. The present study deals with the melt processing of almond skin powder as reinforcement from 0 wt% to 5 wt% in the PLA matrix by twin-screw extrusion process. The results of the study suggested that reinforcing the almond skin powder as 2.5 wt% in the PLA matrix mechanically strengthens the feedstock filaments but the increase in the proportion up to 5 wt% reduces the mechanical strength to a significant level. A similar trend has been observed in differential scanning calorimeter observations for thermal stability analysis. As regard to the rheological property is concerned, the melt flow index shows a significant reduction with reinforcement of almond skin powder in PLA. The results are also supported by photomicrographic analysis (for surface properties) and Taguchi-based optimization of twin-screw extrusion process parameters (for multifactor optimization).
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Tissue engineering is a promising approach to restore or replace a damaged temporomandibular joint (TMJ) disc. However, constructing a scaffold that can mimic biomechanical and biological properties of the natural TMJ disc remains a challenge. In this study, three-dimensional (3D) printing technology was used to fabricate polycaprolactone (PCL)/polyurethane (PU) scaffolds and PU scaffolds to imitate the region-specific biomechanical properties of the TMJ disc. The scaffolds were coated with polydopamine (PDA) and combined with a decellularized matrix (dECM). Then, rat costal chondrocytes and mouse L929 fibroblasts, respectively, were suspended on the composite scaffolds and the biological functions of the cells were studied. The properties of the scaffolds were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), contact angle analysis, and biomechanical testing. To verify the biocompatibility of the scaffolds, the viability, proliferation, and extracellular matrix (ECM) production of the cells seeded on the scaffolds were assessed by LIVE/DEAD staining, Cell Counting Kit-8 assay, biochemical content analysis, immunofluorescence staining, and qRT-PCR. The functionalized hybrid scaffolds were then implanted into the subcutaneous space of nude mice for 6 weeks, and the regenerated tissue was evaluated by histological staining. The biomechanical properties of PCL/PU and PU scaffolds were comparable to that of the central and peripheral zones, respectively, of a native human TMJ disc. The PDA-coated scaffolds displayed superior biomechanical, structural, and functional properties, creating a favorable microenvironment for cell survival, proliferation, ECM production, and tissue regeneration. In conclusion, 3D-printed polymer scaffolds coated with PDA and combined with dECM hydrogel were found to be a promising substitute for TMJ disc tissue engineering.
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In this study, we investigated the influence of isothermal treatment of poly(lactic acid) (PLA) 3D printed samples at different crystallization temperatures. In this case, we analyzed the effect of each crystallization temperature on spherulites formation in printed PLA, affecting the final mechanical properties of pieces. For such, the thermomechanical properties, morphological structure, and crystallization kinetics were analyzed before and after thermal treatment. The 3D printed samples were heat treated at 80°C, 90°C, 100°C, 110°C, and 119°C. With annealing, we observed an improvement in the mechanical PLA properties; however, the exothermic crystallization peak was different for the samples. Pieces before annealing were found to have a low crystallinity index (Ic) of 2%–7%, and the pieces after annealing presented a considerable Ic (27%–34%). Annealing temperatures of 100°C, 110°C, and 119°C produced the fastest crystallization kinetics, while annealing temperatures of 80°C and 90°C resulted in the lowest crystallization kinetics for complete crystallization. After annealing, improvement in the flexural strength (34%–47%) and Young's modulus (26%–51%) for all annealed pieces occurred. The appropriate condition was observed at 100°C, which was the onset temperature of crystallization, owing to the combination of the shorter time of crystallization with the increased mechanical properties.
Article
3D printing is considered a disruptive technology and it continues to expand the design space boundaries for prototypes and final products. Sustainability is one of the major objectives for manufacturing, and the use of recycled materials is becoming a relevant sustainability strategy, particularly for improving material resource efficiency. This paper evaluates the suitability of substituting virgin polylactic acid (PLA) for recycled PLA. It describes an experimental plan divided into three phases to evaluate the specimens’ tensile strength. The results showed that recycled PLA could be used thanks to a similar tensile strength, even though this is slightly lower than that of the virgin material. In addition, the infill density and the orientation parameters played a major role in the response. As the infill density approaches 100%, both the maximum load and tensile strength increase sharply. However, when using an infill density of 40%, on average, the specimen resists 58.07% of the maximum load. In addition, because of the anisotropy, the horizontal orientation allowed attaining a higher tensile strength while the vertical orientation provided a lower value. These are relevant insights for prescriptions of the 3D-printing parameters guaranteeing minimum tensile strength in prototyping.
Article
Polydopamine (PDA) films at the air - water interface can be easily obtained in slightly alkaline dopamine solutions using 02 dissolved in water as an oxidant but their insufficient stability limits their applications. In this work PDA films at the water surface were obtained by polymerization of dopamine hydrochloride (DA) by the enzyme laccase in a slightly acidic environment at a constant concentration of enzyme and DA concentrations in the range from 0.1 to 10 g/l. The dynamic surface elasticity, effective surface tension, film thickness and refractive index were measured as function of time to characterize the main steps of film formation. The obtained results show that laccase accelerates the polymerization process, decreases the required DA concentration for film formation, and insight from Brewster angle microscopy shows that laccase increases the resistance of the films to mechanical deformation. The dynamic surface elasticity of the obtained films is about seven times higher than the highest values for either pure PDA or pure laccase films. Laccase is inferred not only to provide crosslinking of the polymer but is also incorporated in the film resulting in its higher stability. The kinetic dependences of the surface properties allow the main steps of film formation to be distinguished: nucleation of polymer domains in a rapidly-formed protein film, coexistence of the protein and polymer domains, and their transformation into a highly dense composite film with encapsulated protein. Insight from atomic force microscopy images of films transferred to mica show that PDA fills in the gaps of spherical laccase aggregates when the DA concentration is increased and the film becomes less rough. The inclusion of laccase in PDA films significantly increases their stability.
Article
Osteosarcoma (OS) is the most prevalent primary malignancy of bone. Inhibition of OS recurrence and subsequent bone formation after surgery remains a challenge for decades. Innovative biomaterials with the dual function of tumor therapy and bone regeneration have emerged as a promising strategy for OS treatment. We developed a bioactive nanoparticle (MDA-NPs) composed of magnesium oxide nanoparticle (M-NPs) core and 2-Aminoethyl methacrylate (2-AM) grafted polydopamine (PDAM) shell. The phosphonate modified methacrylamide chitosan (CMP) and polyacrylamide (PAM) were prepared to form a pre-gel, and then a series of MDA-NPs nanocomposite with 0 mg/mL, 0.5mg/mL, 2.5mg/mL, 5mg/mL, and 10 mg/mL were incorporated and coded as [email protected], 0.5NP/[email protected], 2.5NP/[email protected], respectively. We found that 5NP/[email protected] hydrogel showed a balanced photothermal effect, mechanical property, and osteogenesis for MDA-NPs can be used as a co-crosslinker, photothermal agent, and Mg²⁺ reservoir. Human OS cells (143B) could be efficiently inhibited by 5NP/[email protected] hydrogel with near-infrared (NIR) laser irradiation, achieving complete suppression of tumor recurrence in vitro and in vivo. The released Mg²⁺ efficiently promotes the osteogenic activities of mouse embryo osteoblast precursor cells (MC3T3-E1) and 5NP/[email protected] hydrogels exhibit highly effective bone repair performance in a critical cranial defect rat model. In conclusion, the 5NP/[email protected] hydrogel demonstrated excellent dual functions of suppressing OS recurrence and repairing bone defects. This novel multifunctional bioactive hydrogel provides an encouraging idea of synergistic postoperative treatment of OS.
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Substrates that are simultaneously thin, strong, optically transparent, and biocompatible have diverse applications in a range of fundamental and applied fields. While nature-derived materials offer advantages of sustainability and inherent biocompatibility compared to synthetic polymers, their brittleness and swelling, as well as surface charge and chemical functionalization non-conducive to cell growth, can hinder widespread application. In this work, we discuss the fabrication and systematic characterization of polydopamine-coated chitosan thin films. Chitosan is a widely used, partially deacetylated form of chitin, derived from crustaceans and arthropods. Polydopamine (PDA) is derived from chemistries mimicking mussel foot adhesive proteins. A facile dip-coating process of thin and flexible, uncrosslinked chitosan films in aqueous dopamine solutions leads to dramatic changes in physical and chemical properties. We show how the PDA forms time-dependent assemblies on the film surfaces, affecting surface roughness, hydrophilicity, and mechanical strength. Coating the surface for even a few seconds provides functional changes to the films. Our results shows that the optimal coating time is on the order of few hours, whereby the films are optically transparent with excellent extensibility and Young’s modulus, while further coating reduces the benefits of this surface coating. These materials are biocompatible, serving as substrates for cell adhesion and growth while maintaining good viability. Overall, these findings give insight to the effects of PDA assembly on surfaces, and illustrate how a simple, quick, and robust bioinspired coating process can prime substrates for biomedical applications such as tissue engineering, biosensing, and wound healing.
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The use of 3D printing technology has enabled the development of low-cost and versatile electrochemical sensors. Commercial conductive filaments have been widely used due to their easiness of acquisition ready for application, and the possibility of surface modification. Generally, these filaments are composed of polymers and conductive material. However, it can present different compositions according to the manufacturing, which includes other additives and impurities. Iron has been reported as one of these impurities in conductive filaments based on polylactic acid and graphene. In this case, we have explored the presence of iron species for the electrochemical synthesis of stable nanoparticles of Prussian blue on 3D printed graphene electrodes. Prussian blue was used for the catalyst and electro-oxidation of L-cysteine amino acid, which is a biomarker related to several health problems and neurodegenerative diseases, such as Alzheimer's and Parkinson's. An arrangement of all 3D printed electrodes was used and presented comparable results to a conventional electrodes array. Also, the proposed sensors have shown good sensitivity, selectivity in presence of other amino acids, repeatability, and intra-day reproducibility for L-cysteine detection, compared to other 3D printed sensors obtained at different ages. The detection of L-cysteine was performed in spiked human blood serum samples, demonstrating no significant matrix interference.
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Poly(lactic acid) (PLA) is an environmentally friendly material, but the hydrophobicity and poor hemocompatibility of PLA impede its application as hemodialysis membranes. In this study, aiming to improve the hemocompatibility of PLA membranes, dopamine-g-carboxylated graphene oxide (DA-g-GOCOOH) was synthesized and then immobilized on PLA membranes via a mussel-inspired adhesion method. The effect of carboxyl content of graphene oxide on hemocompatibility was also investigated. Attenuated total reflectance Fourier transform infrared spectra (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analysis confirmed that DA-g-GOCOOH was successfully immobilized on the PLA membranes. The significant improvement of hydrophilicity and electronegativity of the PLA membranes effectively alleviated the surface adhesion of platelets, prolonged the recalcification time and reduced the hemolysis ratio to less than 0.3%. Moreover, the DA-g-GOCOOH modified PLA membrane showed excellent dialysis performance, especially for the clearance of middle molecule toxin, which was up to 24%. The DA-g-GOCOOH immobilized layers were relatively stable after incubating in water. The present work demonstrated a potential way to improve the hemocompatibility of PLA membranes for hemodialysis.
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A separator plays a crucial role in ensuring the safety in lithium-ion batteries (LIBs). However, commercial separators are mainly based on microporous polyolefin membranes, which possess serious safety risks, such as their thermal stabilities. Although many efforts have been made to solve these problems, they cannot yet fully ensure the safety of the batteries, especially in large-scale applications. Herein, we report a rational design of separator with substantially enhanced thermal features. We report how, by a simple dip-coating process, polydopamine (PDA) formed an overall-covered self-supporting film, both on the ceramic layer and on the pristine polyolefin separator, which made the ceramic layer and polyolefin separator appear as a single aspect and furthermore, this layer amended the film-forming properties of the separator. Combining the function of the ceramic and PDA, the developed composite-modified separator displays substantially enhanced thermal and mechanical stability, with no visual thermal shrink and can maintain its mechanical strength up to 230 °C when the polyethylene separator acts as the pristine separator.
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Three-dimensional scanning serves a large variety of uses. It can be utilized to generate objects for, after possible modification, 3D printing. It can facilitate reverse engineering, replication of artifacts to allow interaction without risking cultural heirlooms and the creation of replacement bespoke parts. The technology can also be used to capture imagery for creating holograms, it can support applications requiring human body imaging (e.g., medical, sports performance, garment creation, security) and it can be used to import real-world objects into computer games and other simulations. This paper presents the design of a 3D scanner that was designed and constructed at the University of North Dakota to create 3D models for printing and numerous other uses. It discusses multiple prospective uses for the unit and technology. It also provides an overview of future directions of the project, such as 3D video capture.
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With the aggressive cost reductions for 3-D printing made available by the open-source self-replicating rapid prototypers (RepRaps) the economic advantage of custom distributed manufacturing has become substantial. In addition, the number of free designs is growing exponentially and the development and commercialization of the recyclebot (plastic extruders that fabricate 3-D printing filament from recycled or virgin materials) have greatly improved the material selection available for prosumer 3-D printer operators. These trends indicate that more individuals will manufacturer their own polymer products, however, there is a risk that an even larger fraction of polymer waste will not be recycled because it has not been coded. The current limited resin identification code available in the U.S. similarly restricts closing the loop on less popular polymers, which could hamper the environmental impact benefits of distributed manufacturing. This paper provides a solution for this challenge by (1) developing a recycling code model based off of the resin identification codes developed in China that is capable of expansion as more complex 3-D printing materials are introduced, (2) creating OpenSCAD scripts based on (1) to be used to print resin identification codes into products, (3) demonstrating the use of this functionality in a selection of products and polymer materials, and (4) outlining the software and policy tools necessary to make this application possible for widespread adoption. Overall the results showed that a far larger resin code identification system can be adopted in the U.S. to expand distributed recycling of polymers and manufacturing of plastic-based 3-D printed products.
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We report a versatile approach for the design of substrate-independent low-fouling surfaces via mussel-inspired immobilisation of zwitterionic peptides. Using mussel-inspired polydopamine (PDA) coatings, zwitterionic glutamic acid- and lysine-based peptides were immobilised on various substrates, including noble metals, metal oxides, polymers, and semiconductors. The variation of surface chemistry and surface wettability upon surface treatment was monitored with X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. Following peptide immobilisation, the surfaces became more hydrophilic due to the strong surface hydration compared with PDA-coated surfaces. The peptide-functionalised surfaces showed resistance to human blood serum adsorption and also effectively prevented the adhesion of gram-negative and gram-positive bacteria (i.e., Escherichia coli and Staphylococcus epidermidis) and mammalian cells (i.e., NIH 3T3 mouse embryonic fibroblast cells). The versatility of mussel-inspired chemistry combined with the unique biological nature and tunability of peptides allows for the design of low-fouling surfaces, making this a promising coating technique for various applications.
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Polymeric microparticles are promising adjuvants and they exhibit various physicochemical characteristics that can regulate the immune response, including hydrodynamic size, morphology, and surface properties, among others. Surface hydrophobicity is also a key microparticle characteristic, but how it affects microparticle adjuvanticity remains unknown. To study the correlation between microparticle hydrophobicity and adjuvanticity in-depth, we prepared poly(d,l-lactic acid) (PLA)-, poly(d,l-lactic-co-glycolic acid) (PLGA)-, and poly(monomethoxypolyethylene glycol-co-d,l-lactide) (mPEG-PLA, PELA)-based microparticles by premix membrane emulsification, which were similar in size and morphology but differed in surface hydrophobicity. We then systematically evaluated their ability to induce immune responses in vitro and in vivo. Increased surface hydrophobicity on PLA-based microparticles greatly promoted antigen internalization into dendritic cells (DCs) as well as MHC II and CD86 expression on DCs in vitro. Similarly, in vivo studies showed that increased microparticle surface hydrophobicity significantly elevated cytokine secretion levels by splenocytes harvested from vaccinated mice. Adhesion force measurements confirmed that increased surface hydrophobicity enhanced the physical interaction between microparticles and cell membranes, a condition favorable for promoting microparticle internalization into cells. Taken together, these results indicated that microparticle hydrophobicity is an important factor that determines the magnitude of immune responses elicited by vaccination with different particulate systems.
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Boron nitride nanotubes (BNNTs) are excellent nanofillers to enhance the mechanical and thermal properties of polymer nanocomposites. Despite the rapid progress in the effective syntheses of BNNTs, the ease of processability and solubility are major roadblocks for their widespread applications. The present work reports for the first time: a facile and environment-friendly green approach for aqueous bioinspired functionalization of boron nitride nanotubes through the use of dopamine, a synthetic mimic of mussel adhesive proteins. This approach is based on the affinity of the amino group of dopamine molecules for the boron atoms in BNNTs and π–π interactions as well as van der Waals interactions between the BNNTs network and dopamine molecules. Functionalization of the boron nitride nanotubes was evidently found to be associated with the existing π–π bonding and van der Waals interactions at the BNNT surfaces, involving the aromatic core structures of the dopamine molecules based on various characterizations. The resultant functionalized BNNTs are highly dispersible in water and a number of solvents. Polymer nanocomposites were prepared using pristine and dopamine functionalized BNNTs as reinforcement in a poly(vinyl difluoroethylene) matrix and tested for the thermal and mechanical properties. The functionalized BNNT reinforced polymer nanocomposites exhibit superior properties as compared to nanocomposites based on pristine BNNTs. This comprehensive study indicates that dopamine functionalized BNNTs are promising materials for various applications and are expected to form the basis of a new class of chemically reactive nanostructures.
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Herein, for the first time, the electrochemiluminescent sensor based on Ru(bpy)(3) (2+)-modified electrode using dopamine as an adhesive was successfully developed. After halloysite nanotube slurry was cast on a glassy carbon electrode and dried, an alkaline dopamine solution was added on the electrode surface. Initially, polydopamine belts with dimensions of tens to hundreds of nanometers formed via oxidization of the dopamine by ambient oxygen. As the incubation time increased, the nanobelts became broader and then united with each other to form a polydopamine film. The halloysite nanotubes were embedded within the polydopamine film. The above electrode was soaked in Ru(bpy)(3) (2+) aqueous solution to adsorb Ru(bpy)(3) (2+) into the active sites of the halloysite nanotubes via cation-exchange procedure. Through this simple procedure, a Ru(bpy)(3) (2+)-modified electrode was obtained using only 6.25 microg Ru(bpy)(3) (2+), 15.0 microg dopamine, and 9.0 microg halloysite nanotubes. The electrochemistry and electrochemiluminescence (ECL) of the modified electrode was investigated using tripropylamine (TPA) and nitrilotriacetic acid (NTA) as co-reactants. The different ECL behaviors of the modified electrode using NTA and TPA as well as the contact angle measurements reflected the hydrophilic character of the electrode. The results indicate that halloysite nanotubes have a high loading capacity for Ru(bpy)(3) (2+) and that dopamine is suitable for the preparation of modified electrodes.
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We report a method to form multifunctional polymer coatings through simple dip-coating of objects in an aqueous solution of dopamine. Inspired by the composition of adhesive proteins in mussels, we used dopamine self-polymerization to form thin, surface-adherent polydopamine films onto a wide range of inorganic and organic materials, including noble metals, oxides, polymers, semiconductors, and ceramics. Secondary reactions can be used to create a variety of ad-layers, including self-assembled monolayers through deposition of long-chain molecular building blocks, metal films by electroless metallization, and bioinert and bioactive surfaces via grafting of macromolecules.
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The aim of this paper is to analyze the performance of a RepRap 3D printer liquefier by studying its thermal behavior, focusing on the convective heat dissipation developed along the liquefier body during the 3D printing process of a workpiece. More specifically, this work tackles with the influence of the airflow generated by a fan coupled to the extruder, on the heat transfer mechanisms during the printing process. The airflow is thus taken as the variable of study. The temperature at the top of the liquefier body, where a low temperature is desirable for the correct preservation of the 3D printer components, is analyzed to assess the results for the different printing conditions.For the development of this study, a finite elements model was used to determine the theoretical temperature profile of the liquefier in a steady state working regime. This mathematical model was then validated with experimental data registered with four thermocouples fixed on the tested extruder. The data was taken for different airflows, finding a relation between printing parameters and resulting temperature profile. The liquefier used for experimental data acquisition was the BCNozzle model, designed by the BCN3D Technologies of the Polytechnic University of Catalonia.Determining the correct working parameters is necessary to optimize the fused filament fabrication process on which 3D printing is based, ensuring a suitable temperature distribution along the liquefier body. This would allow a correct position of the melting front along the liquefier channel, and at the same time, a non-excessive temperature at its top, next to the feeding mechanism. This is the relevance of this study, through which a model is obtained to analyze the heat transfer mechanisms, applicable for other working regimes and other extruders based on the same working principles.
Chapter
The plastic industry, like other sectors, also seeks to minimize waste production. For this, rationalization systems have been developed or systems for immediate recovery and immediate recycling after grinding in front of the press. The chapter mentions the use of industrial packaging which is reusable a number of times before being repaired and finally recycled. This application required the development of standards which optimize the loading of transport and the transport of empty containers. Plastic waste can be recycled in different ways and it is legitimate to try to establish a hierarchy between the various processes. The chapter proposes to use the criterion of entropy creation. The impact of waste on the environment is not negligible, but it does not, by a long way, hold the first place. Plastics are especially landfilled in mixture with other garbage. Recycling therefore remains an important activity to provide in the coming years.
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Most desktop 3D printers designed for the consumer market utilize a plastic filament extrusion and deposition process to fabricate solid objects. Previous research has shown that the operation of extrusion-based desktop 3D printers can emit large numbers of ultrafine particles (UFPs: particles less than 100 nm) and some hazardous volatile organic compounds (VOCs), although very few filament and printer combinations have been tested to date. Here we quantify emissions of UFPs and speciated VOCs from five commercially available desktop 3D printers utilizing up to nine different filaments using controlled experiments in a test chamber. Median estimates of time-varying UFP emission rates ranged from ~108 to ~1011 #/min across all tested combinations, varying primarily by filament material and, to a lesser extent, bed temperature. The individual VOCs emitted in the largest quantities included caprolactam from nylon-based and imitation wood and brick filaments (ranging from ~2 to ~180 μg/min), styrene from acrylonitrile butadiene styrene (ABS) and high-impact polystyrene (HIPS) filaments (~10 to ~110 μg/min), and lactide from polylactic acid (PLA) filaments (~4 to ~5 μg/min). Results from a screening analysis of the potential exposures to these products in a typical small office environment suggest caution should be used when operating many of the printer and filament combinations in enclosed or poorly ventilated spaces or without the aid of a combined gas and particle filtration system.
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Membrane fouling and chlorine degradation are two of the major challenges the reverse osmosis (RO) membrane industry is facing in recent years. In the present study, a commercial aromatic polyamide RO membrane (XLE-400, DOW Co., Ltd.) was modified via surface coating of polydopamine (PDA) followed by the grafting of polyethylenimine (PEI). The successful modification was confirmed by X-ray photoelectron spectroscopy (XPS). Membrane surface properties were characterized through scanning electron microscopy (SEM), atomic force microscopy (AFM), zeta potential and contact angle. The results showed that modification enhanced the surface hydrophilicity, moved the surface charge towards the positive side and made the surface slightly rougher without damaging the surface peak-and-valley substrate. The influence of modification on the permselectivity of the membrane was also examined. The modified membrane had a higher salt rejection and a slightly lesser water flux than the unmodified membrane. Furthermore, the chlorination, fouling and simulated biofouling experiments were done. The results showed that, due to the abundant presence of grafted amino groups coming from PEI, the modified membrane exhibited higher chlorine resistance, anti-fouling and antibacterial properties.
Article
In this study, we introduce a method for large-area and substrate-independent synthesis of the big-inner-diameter carbon nanotube (BIDI-CNT) thin films by utilizing polydopamine (PDA) as carbon source and ZnO nanorods (NRs) as sacrificing template for the first time. ZnO NRs with hexagonal morphology were coated with PDA films via the ammonium persulfate-induced polymerization of dopamine at neutral pH for avoiding the degradation of amphoteric ZnO at alkaline pH needed by the conventional oxygen-induced polymerization of dopamine. After carbonization in N2 atmosphere at 500 °C followed by ZnO removal, the hollow BIDI-CNTs with tuned wall thickness and hexagonal morphology were obtained. In addition, the obtained BIDI-CNTs were found to be N-doped. Furthermore, on the base of the outstanding substrate-independent growth properties of both ZnO NRs and PDA, the large area thin films of the N-doped BIDI-CNTs could be synthesized on various solid substrates, for instance, Al2O3, gold, fluorine-doped tin oxide-coated glass, platinum, silicon, mica, and quartz.
Article
3D printing is a versatile technique to generate large quantities of a wide variety of shapes and sizes of polymer. The aim of this study is to develop functionalized 3D printed poly(lactic acid) (PLA) scaffolds and use a mussel-inspired surface coating to regulate cell adhesion, proliferation and differentiation of human adipose-derived stem cells (hADSCs). We prepared PLA 3D scaffolds coated with polydopamine (PDA). The chemical composition and surface properties of PDA/PLA were characterized by XPS. PDA/PLA modulated hADSCs' responses in several ways. Firstly, adhesion and proliferation, and cell cycle of hADSCs cultured on PDA/PLA were significantly enhanced relative to those on PLA. In addition, the collagen I secreted from cells was increased and promoted cell attachment and cell cycle progression were depended on the PDA content. In osteogenesis assay, the ALP activity and osteocalcin of hADSCs cultured on PDA/PLA were significantly higher than seen in those cultured on pure PLA scaffolds. Moreover, hADSCs cultured on PDA/PLA showed up-regulation of the ang-1 and vWF proteins associated with angiogenic differentiation. Our results demonstrate that the bio-inspired coating synthetic PLA polymer can be used as a simple technique to render the surfaces of synthetic scaffolds active, thus enabling them to direct the specific responses of hADSCs. Copyright © 2015 Elsevier B.V. All rights reserved.
Article
Mussel-inspired catecholamine polymers (poly(dopamine) and poly(norepinephrine)) were coated on the surface of carbon and glass fibers in order to increase the interfacial shear strength between fibers and polymer matrix, and consequently the interlaminar shear strength of fiber-reinforced composites. By utilizing adhesive characteristic of the catecholamine polymer, fiber-reinforced composites can become mechanically stronger than conventional composites. Since the catecholamine polymer is easily constructed on the surface by the simultaneous polymerization of its monomer under a weak basic circumstance, it can be readily coated on micro-fibers by a simple dipping process without any complex chemical treatments. Also, catecholamines can increase the surface free energy of micro-fibers and therefore, can give better wettability to epoxy resin. Therefore, catecholamine polymers can be used as versatile and effective surface modifiers for both carbon and glass fibers. Here, catecholamine-coated carbon and glass fibers exhibited higher interfacial shear strength (37 and 27% increases, respectively) and their plain woven composites showed improved interlaminar shear strength (13 and 9% increases, respectively) compared to non-coated fibers and composites.
Article
Inspired by the bio-adhesive ability of the marine mussel, a simple, versatile, effective and green synthesis strategy was developed to prepare dense, phase-pure and reproducible zeolite molecular sieve membranes by using polydopamine (PDA) as a novel covalent linker. Through the formation of strong non-covalent and covalent chemical bonds, zeolite LTA nutrients can be attracted and bound to the support surface, thus promoting the nucleation and seeding-free growth of uniform, well-intergrown and phase-pure zeolite membranes. The zeolite LTA membranes prepared on PDA-modified Al2O3 disks were evaluated in single gas permeation and mixed gas separation. It is found that the zeolite LTA membranes prepared on PDA-modified support showed higher gas separation selectivities. At 373 K and 1 bar, the mixture separation factors of H2/CO2, H2/N2, H2/CH4, and H2/C3H8 are 7.8, 7.2, 6.6 and 18.3, which by far exceed the corresponding Knudsen coefficients. Furthermore, in comparison with the previously proposed chemical modification methods, the modification procedure by PDA is done under a mild environment (simple immersion in buffered aqueous solution of DPA at room temperature), thus it is helpful to prepare zeolite membranes at a large-scale and reduce the costs of the membrane manufacturing.
Article
The growth of desktop 3-D printers is driving an interest in recycled 3-D printer filament to reduce costs of distributed production. Life cycle analysis studies were performed on the recycling of high density polyethylene into filament suitable for additive layer manufacturing with 3-D printers. The conventional centralized recycling system for high population density and low population density rural locations was compared to the proposed in home, distributed recycling system. This system would involve shredding and then producing filament with an open-source plastic extruder from post-consumer plastics and then printing the extruded filament into usable, value-added parts and products with 3-D printers such as the open-source self replicating rapid prototyper, or RepRap. The embodied energy and carbon dioxide emissions were calculated for high density polyethylene recycling using SimaPro 7.2 and the database EcoInvent v2.0. The results showed that distributed recycling uses less embodied energy than the best-case scenario used for centralized recycling. For centralized recycling in a low-density population case study involving substantial embodied energy use for transportation and collection these savings for distributed recycling were found to extend to over 80%. If the distributed process is applied to the U.S. high density polyethylene currently recycled, more than 100 million MJ of energy could be conserved per annum along with the concomitant significant reductions in greenhouse gas emissions. It is concluded that with the open-source 3-D printing network expanding rapidly the potential for widespread adoption of in-home recycling of post-consumer plastic represents a novel path to a future of distributed manufacturing appropriate for both the developed and developing world with lower environmental impacts than the current system.
Article
Bio-based poly (lactic acid) membrane with asymmetric porous structure was developed for hemodialysis via phase inversion for the first time. Heparin was immobilized to PLA membrane surface through the strong adhesion ability of dopamine, as confirmed by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) respectively. The morphologies variations of PLA membranes induced by dopamine coating and heparin immobilization were analyzed by scanning electron microscope (SEM) and atomic force microscopy (AFM). Hydrophilicity and permeability of PLA membranes before and after modification were characterized. Particularly, platelet adsorption, plasma recalcification time and hemolysis ratio were executed to evaluate the blood compatibility of PLA membranes decorated by heparin. The in vitro results demonstrated that surface heparinization improved the hemocompatibility of PLA membrane, suppressed the adhesion of platelet, extended plasma recalcilication time, and also decreased hemolysis ratio. The dialysis simulation experiments including urea and lysozyme clearance as well as bovine serum albumin (BSA) rejection were implemented to determine the dialysis performances. The results showed that 79% of urea and 18% of lysozyme were cleaned and over 90% of BSA was retained. This study disclosed a window of opportunity to produce novel hemodialysis membranes using bio-based materials. (C) 2013 Elsevier B.V. All rights reserved
Article
We report the effect of filler modification on the properties of polylactide (PLA)-based nanocomposites, where graphene oxide (GO) nanosheets and polyhedral oligomeric silsesquioxane (POSS) nanocages are employed as nanofillers. The organically treated nanofillers are termed as GO-functionalized and POSS-functionalized. The synthesis of the nanocomposites was carried out via in situ ring-opening polymerization of lactic acid (LA). The following four naocomposite systems were prepared, characterized, and compared to achieve a better understanding of structure-property relationship (1) PLA/GO-functionalized, (2) PLA/POSS-functionalized, (3) PLA/physical mixture of GO-functionalized and POSS-functionalized, and (4) PLA/GO-graft-POSS (with eight hydroxyl groups). As revealed by the thermal and mechanical (nanoindendation) characterization, that the nanocomposites having a combination of GO and POSS as nanofiller, either as physical mixture of GO-functionalized and POSS-functionalized or as GO-graft-POSS, is far more superior as compared with the nanocomposites having individually dispersed nanofillers in the PLA matrix. Observed enhancement is attributing to the synergistic effect of the nanofillers as well as better dispersion of the modified-fillers in the matrix. POLYM. COMPOS., 35:118–126, 2014. © 2013 Society of Plastics Engineers
Article
In this work, dopamine was introduced as a modifier for the surface treatment of ramie fiber. The interfacial crystallization of Poly (butylene succinate) (PBS) on the surface of treated fiber was investigated using polarized light microscope (PLM). It was found that raw ramie fiber has almost no nucleation ability on the crystallization of PBS. However, a beautiful transcrystalline (TC) structure could be successfully induced at the surface of treated fiber, which indicates a significantly improved nucleation ability of dopamine on PBS crystallization. Even more importantly, it was found that the interfacial shear strength between PBS and the treated fiber was very much improved due to the formation of transcrystalline structure. In order to further investigate the role of dopamine on interfacial enhancement, PBS/treated ramie fiber (10 wt%) composites were prepared by compression molding under the same condition with PLM. The tensile test showed that the tensile strength of composites with TC structure was increased by 30% when crystallized for 4 min than that of composites with an amorphous layer when crystallized for 0 min. This result suggested again that the interfacial enhancement was indeed due to the interfacial crystallization. Our work demonstrates that dopamine could be a green and novel surface modifier for natural fiber, and control of interfacial crystallization could be an efficient way for the interfacial enhancement between matrix and fillers.
Article
To improve the thermal stability and mechanical properties of PLA, crosslinking was introduced via chemical treatment of the melt by adding small amounts of crosslinking agent triallyl isocyanurate (TAIC) and dicumyl peroxide (DCP). A series of crosslinked PLA materials with different gel fraction and crosslink density were prepared. The crosslinked PLA samples were characterized by fourier transform infra-red spectrometry (FTIR). The thermal and mechanical properties of samples were also investigated by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), tensile testing and dynamic mechanical analysis (DMA). The results showed that the crosslinking of PLA started at a low content of either TAIC or DCP, resulting in a decrease of crystallinity and a significant improvement of the thermal degradation initiation and completion temperatures, which indicated better thermal stability than neat PLA. Crosslinking was also responsible for the improved tensile modulus and tensile strength.
Article
Polylactic acid (PLA) has now become an economically viable commodity plastic in many industries. This raises the question of recyclability of industrial production waste and some packaging wastes as well. The evolution of rheological and mechanical properties of polymer with the number of recycling cycles up to seven was investigated. For PLA, only the tensile modulus remains constant with the thermo-mechanical cycles. In contrast, stress and strain at break, rheological factors and the modulus and hardness probed by nanoindentation decrease for PLA. This dramatic effect is ascribed to a large decrease in the molecular weight due to several different complex degradation processes which are discussed. The effect of two stabilizers is also assessed.
Article
Current interest in melanin films derived from the autoxidation of dopamine stems from their use as a universal adhesion layer. Here we report chemical and physical characterization of polydopamine films deposited on gold surfaces from stirred basic solutions at times ranging from 2 min to 60 min, with a focus on times ≤ 10 min. Data from Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and electrochemical methods suggest the presence of starting (dopamine) and intermediate (C=N containing tautomers of quinone and indole) species in the polydopamine films at all deposition times. A uniform overlayer analysis of the XPS data indicates that film thickness increased linearly at short deposition times of ≦ 10 min. At deposition times ≥ 10 minutes, the films appeared largely continuous with surface roughness ≈ ≤ 2 nm, as determined by AFM. Pin-hole free films, as determined by anionic redox probe measurements, required deposition times of 60 minutes or greater.
Article
The influence of processing conditions during melt extrusion on the degradation of poly(L-lactide) (PLLA) has been investigated. PLLA polymer was processed by melt extrusion in a double screw extruder at 210 and 240°C. For each extrusion temperature, two screw rotation speeds, 20 and 120 rpm, were used. To investigate the influence of moisture on the thermal degradation during processing, the PLLA granules were dried at 100°C for 5 h and then either extruded directly or conditioned at 65% RH, 20°C for 24 h prior to extrusion. The results show that a decrease in molecular weight measured as number-average (Mn) molecular weight occurs for all combinations of process parameters used. At processing temperature of 210°C, the change in molecular weight for the dry granules was shown to be dependent on the residence time (i.e., screw rotation speed) in the melt. By changing the screw rotation speed from 120 to 20 rpm at 210°C, Mn decreased from 33,600 to 30,200 g/mol. When the processing temperature was increased to 240°C, the dry granules showed an Mn of 25,600 and 13,600 g/mol when extruded at 120 and 20 rpm, respectively. Mn for the conditioned specimens extruded at 210°C was 18,400 g/mol when processed at 120 rpm and 12,300 g/mol at 20 rpm. When processed at 240°C, 20 rpm, Mn is independent of whether the granules were dry or moist prior to extrusion. It is probably due to the fact that the degradation at 240°C is so extensive that the presence of moisture in the polymer does not contribute further to the degradation process. The stress and strain at break decreased due to degradation and were dependent on the molecular weight of the samples. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2128–2135, 2001
Article
The tensile strength and thermal stability of polylactide (PLA) were significantly improved through chemical crosslinking. However, it became much more rigid and brittle. To obtain a material with good thermal stability and enhanced ability to plastic deformation, chemical crosslinked PLA with 0.5 wt % triallyl isocyanurate and 0.5 wt % dicumyl peroxide was blended with different contents of dioctyl phthalate (DOP). The advantage of using DOP is that it does not crystallize, has low glass transition temperature, and is miscible with PLA. The morphology and the thermal and mechanical properties of the crosslinked PLA and the blends of crosslinked PLA with various contents of DOP were investigated by means of scanning electron microscope, differential scanning calorimetry, tensile test, and dynamic mechanical analysis. The rheological properties of samples were also explored by using a capillary rheometer. The results showed that the DOP was an effective plasticizer for the chemical crosslinked PLA, resulting in a significantly decreased Tg, lower yield stress, and improved elongation at break. The plasticization effect was enhanced by adding higher DOP content. In addition, the DOP enhanced the crystallinity of crosslinked PLA, and all the crosslinked samples showed better heat stability than neat PLA. The apparent viscosity of the blends decreased with the increase of DOP content and a phase separation occurred when the content of DOP exceeded 12.5 wt %. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1136–1145, 2009
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Surface enhanced Raman scattering (SERS) and FTIR were used for the vibrational characterization of the sepia melanin pigment extracted from the cuttlefish or Sepia officinalis, a material used in works of art from at least the late 18th century. The heterogeneous polymeric nature of the pigment, together with its fluorescent background, makes its identification by normal Raman spectroscopy difficult. In the present study, SERS and FTIR spectra of sepia were obtained. SERS proved to be suitable to characterize this complex material in micro-samples because of its sensitivity, ability to quench fluorescence, and minimal preparation required. For the SERS measurements, different substrates were tested in contact with the sepia pigment. It was found that a sodium borohydride reduced silver colloid gave the best performance, particularly when applied as a drop on top of a solid sepia sample, and subsequently dried. A larger enhancement was observed in the SERS spectrum of the sepia sample extracted in the laboratory, when compared to the more pure commercial sample, consistently with the higher metal binding capacity of less pure sepia melanin reported by other authors. The FTIR and SERS frequencies observed were found to be consistent with those reported in the literature for closely related compounds, such as indole, pyrrole and substituted pyrroles, and were assigned by comparison with them and with other published data for functional groups in organic chemistry.
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Science MIMIC-king nature: Hydrophilic conversion of superhydrophobic surfaces can be easily achieved through a bioinspired approach to produce an alternating superhydrophobic-hydrophilic surface by using established soft-lithographic techniques, such as micromolding in capillaries (MIMIC). The resulting patterned surface showed high water adhesion properties as well as superhydrophobic properties.