Centro de Tecnologia da Informação Renato Archer
  • Campinas, Estado de Sao Paulo, Brazil
Recent publications
Introduction Tracheal fistula (TF) treatments may involve temporary orthosis and further ablative procedures, which can lead to infection. Thus, TF requires other therapy alternatives development. The hypothesis of this work was to demonstrate the feasibility of a tissue-engineered alternative for small TF in a preclinical model. Also, its association with suture filaments enriched with adipose tissue-derived mesenchymal stromal stem cells (AT-MSCs) was assessed to determine whether it could optimize the regenerative process. Methods Poly (L-Lactic acid) (PLLA) membranes were manufactured by electrospinning and had morphology analyzed by scanning electron microscopy. AT-MSCs were cultured in these scaffolds and in vitro assays were performed (cytotoxicity, cellular adhesion, and viability). Subsequently, these cellular constructs were implanted in an animal small TF model. The association with suture filaments containing attached AT-MSCs was present in one animal group. After 30 d, animals were sacrificed and regenerative potential was evaluated, mainly related to the extracellular matrix remodeling, by performing histopathological (Hematoxylin-Eosin and trichrome Masson) and immunohistochemistry (Collagen I/II/III, matrix metalloproteinases–2, matrix metalloproteinases–9, vascular endothelial growth factor, and interleukin-10) analyses. Results PLLA membranes presented porous fibers, randomly oriented. In vitro assays results showed that AT-MSCs attached were viable and maintained an active metabolism. Swine implanted with AT-MSCs attached to membranes and suture filaments showed aligned collagen fibers and a better regenerative progress in 30 d. Conclusions PLLA membranes with AT-MSCs attached were useful to the extracellular matrix restoration and have a high potential for small TF treatment. Also, their association with suture filaments enriched with AT-MSCs was advantageous.
Several techniques, such as additive manufacturing, have been used for the manufacture of polymer-ceramic composite scaffolds for bone tissue engineering. A new extruder head recently developed for improving the manufacturing process is an experimental 3D printer Fab@CTI that enables the use of ceramic powders in the processing of composite materials or polymer blends. Still, the manufacturing process needs improvement to promotes the dispersion of ceramic particles in the polymer matrix. This article addresses the manufacture of scaffolds by 3D printing from mixtures of poly(ε-caprolactone) (PCL) and a glass powder of same composition of 45S5Bioglass®, labeled as synthesized bioglass (SBG), according to two different methods that investigated the efficiency of the new extruder head. The first one is a single extrusion process in a Fab@CTI 3D printer, and the other consists in the pre-processing of the PCL-SBG mixture in a mono-screw extruder with a Maddock ® element, followed by direct extrusion in the experimental Fab@CTI 3D printer. The morphological characterization of the extruded samples by SEM showed an architecture of 0o/90o interconnected struts and suitable porosity for bone tissue engineering applications. Scaffolds fabricated by two methods shows compressive modulus ranging from 54.4 ± 14.2 MPa to 155.9 ± 20.4 MPa, results that are compatible to use in bone tissue engineering. Cytotoxicity assays showed non-toxic effects and viability for in vitro MG-63 cell proliferation. Alizarin Red staining test showed calcium deposition in all scaffolds, which suggests PCL/SBG composites promising candidates for use in bone tissue engineering. Results of cell morphology suggest more cell growth and adhesion for scaffolds fabricated using the pre-processing in a mono-screw extruder.
Web technologies provide resources for the intensive use of colors in web pages. They are a core element in the design of interactive interfaces and are essential in the perception and understanding of information. However, color intensive design on the web affects the accessibility for users with color vision deficiency (CVD), who face difficulties in recognizing or distinguishing colors. CVD users may experience limitations and barriers in exploring web pages, even for simple tasks. Interface adaptation techniques may deal with several CVD visualization issues. Nevertheless, different situations and individual preferences turn choosing the most suitable recoloring technique into a complex task. Existing proposals in the literature fail in not considering various pathology types and individual preferences. This article defines a framework and techniques for the development of adaptive interfaces that facilitate the interaction of CVD people with web systems. The proposed research develops the FAIBOUD framework, which uses ontologies as artifacts for representing knowledge about CVD types, recoloring algorithms, and users’ access contexts and preferences. The FAIBOUD includes algorithms to support an adaptation decision process, which selects the most suited adaptation technique according to CVD type and access context. Our solution allows for the determination and automatic application of the best recoloring techniques to adapt interfaces for CVD users. Our experimental evaluation was conducted with fifteen CVD users. The results obtained from several illustrative scenarios demonstrate the benefits and enhancement of web interface accessibility based on our adaptive approach.
Herein, we report the synthesis and characterization of two Pt(II) coordination compounds, the new platinum(II)[N,N′-bis(salicylidene)-3,4-diaminobenzophenone)] ([Pt(sal-3,4-ben)]) and the already well-known platinum(II)[N,N′-bis(salicylidene)-o-phenylenediamine] ([Pt(salophen)]), along with their application as guests in a poly [9,9-dioctylfluorenyl-2,7-diyl] (PFO) conjugated polymer in all-solution processed single-layer white organic light-emitting diodes. Completely different performances were achieved: 2.2% and 15.3% of external quantum efficiencies; 2.8 cd A−1 and 12.1 cd A−1 of current efficiencies; and 3103 cd m−2 and 6224 cd m−2 of luminance for the [Pt(salophen)] and [Pt(sal-3,4-ben)] complexes, respectively. The Commission Internationale de l’Eclairage (CIE 1931) chromaticity color coordinates are (0.33, 0.33) for both 0.1% mol/mol Pt(II):PFO composites at between approximately 3.2 and 8 V. The optoelectronic properties of doped and neat PFO films have been investigated, using steady-state and time-resolved photoluminescence. Theoretical calculations at the level of relativistic density functional theory explained these results, based on the presence of the Pt(II) central ion’s phosphorescence emission, considering spin-orbit coupling relationships. The overall results are explained, taking into account the active layer morphological properties, along with the device’s electric balance and the emitter’s efficiencies, according to deep-trap space-charge models. Considering the very simple structure of the device and the ease of synthesis of such compounds, the developed framework can offer a good trade-off for solution-deposited white organic light-emitting diodes (WOLEDs), with further applications in the field of lighting and signage.
Lattice structures are porous materials with interconnected porosity and non-stochastic pore distribution that present unique properties. Recently, additive manufacturing (AM) has driven attention to the production of lattice structures since it provides a direct-from-CAD production, tailoring their mechanical properties by controlling their unit cell type, pore size, strut size, and porosity. However, the mechanical behavior of these structures is yet to be understood, as surface post-processing is needed for the biomedical application (ASTM F3335) and manufacturing deviations and defects imply different results from the CAD projected models. In this work, three different types of Ti-6Al-4 V ELI lattice structures were projected and produced by powder bed fusion AM technique. The surface structures were cleaned using pickling, and as-built and pickled structures were compared using scanning electron microscopy (SEM), optical microscopy (OM), and Archimedes’ principle. Mechanical compressive tests were conducted on the surface-cleaned lattice structures, and fractured surfaces were analyzed by SEM. Finally, finite element analysis (FEA) was made to understand the stress distribution during compression. The results show that pickling is successful in removing adhered powder particles from lattice structures’ outer and inner surfaces, as it also reduces surface roughness and defects, which may act as stress raisers. The compressive tests along with fracture analysis show that fracture behavior cannot be predicted using Maxwell’s criterion in 3D and FEA can be a better tool to predict fracture behavior. These results show that classifications of lattice structures made by AM in stretch or bending-based need further research.
The various methods for microwave processing of materials exhibit numerous advantages, such as short processing times, high yield, expanded reaction conditions, high reproducibility, and high purity of products. Microwave-assisted synthesis strategies have been widely adopted for the preparation of high-performance graphene-based materials for supercapacitor electrodes. Metal oxides, mixed metal oxides, metal hydroxides, layered double hydroxides, carbon nanotubes and conducting polymers are some of the main materials which have been added to graphene derivatives for advanced composite/hybrid electrodes. This review article first provides a brief introduction and an overview of microwave heating and its advantages for processing graphene-based electrode materials. After that, a systematic survey of recently published research on microwave irradiation-assisted processing is presented, focusing on: (i) transformation of graphite/ graphite oxide into graphene/graphene oxide by exfoliation and reduction; (ii) formation of graphene derivatives in various liquid and gaseous media; (iii) modification of graphene derivatives with various metal oxides/hydroxides, carbon nanotubes, and conducting polymers for use in supercapacitors. Major challenges and future perspectives for microwave-assisted processing of graphene-based materials for cutting-edge supercapacitor electrode applications are also summarized in the conclusion.
Ceramic composites based on (Ce, Y)-TZP/Al2O3 system have great potential for applications as dental implants due to their unusually great balance between good mechanical properties and resistance to hydrothermal degradation. Surface roughness plays an important role in controlling these properties, but few studies have investigated the relationship between cytocompatibility and surface roughness, at levels considered moderate and low, comparable to titanium implants. In this work, bending strength, hydrothermal degradation and biological evaluation of a ceramic composite based on (Ce,Y)-TZP/Al2O3 system were investigated as a function of surface roughness. Compacted samples were sintered at 1500 °C - 2h and then submitted to different surface treatments: Group 1 composed of samples with smooth surfaces, Group 2 and Group 3 composed of rough surfaces (grinded with 15 μm or 45 μm diamond sandpaper, respectively. Samples were characterized by X-ray diffraction, scanning electron microscopy, contact angle and optical profilometry and then subjected to hydrothermal degradation tests in autoclave (134 °C - 2 bar) using artificial saliva. The Piston-on-three-balls (P–3B) testing was used to determine flexural strength. To assess indirect cytotoxicity, samples were immersed in the culture medium for NIH-3T3 cells for 72 hours. Furthermore, cell adhesion and proliferation were investigated using MG63 cells (human osteosarcoma) after 3, 7, 14, and 21 days of culture. Cytotoxicity, adhesion, and cell proliferation were examined by the Methyl Tetrazolium salt (MTS) and Alizarin Red, using a confocal laser microscope. The results indicated that the materials have high resistance to degradation. Furthermore, the (Ce,Y)-TZP/Al2O3 composites are not cytotoxic. The flexural strength of the composites was 913 ± 103 MPa in samples presenting original (smooth) surface, however, a reduction in the order of 17% was observed in samples containing rough surfaces. The rougher samples show the best cellular adhesion and proliferation, leading to the formation of a mineralized matrix after 21 days. These results clearly suggest that the new (Ce,Y)-TZP/Al2O3 brand is strong and highly biocompatible and warrants further study.
The worldwide network of computers moves a huge amount of electronic information and, therefore, it has become an integral part of our daily lives. The most diverse types of companies, such as hospitals, banks, stock exchanges, educational institutions, and power generation industries use this network to efficiently operate their processes, which range from collecting, processing, storing, and sharing large amounts of digital information. As more digital information is collected and shared, protecting that information becomes even more essential for national security and economic stability. Information security is the ongoing effort to protect these networked systems and all data from unauthorized or harmful use. As an individual, we have a responsibility to protect our identity, our data, and our computing devices. At the corporate level, it is everyone’s responsibility to protect the company’s reputation, data, and customers. As a state, national security and the well-being of citizens are at stake. Therefore, consolidating data and privacy competencies, integrating available technologies, can contribute to the better implementation, operation, and maintenance of compliance and privacy programs in organizations. In addition to being up-to-date with new technologies, ensuring that information security management methods and infrastructure are essential for a free society that has its privacy rights guaranteed.
Parameterization of geometries for g-code compiling arises as an attractive option to control 3D printers. Based on the geometry of the object to be fabricated, and the construction platform, or the container where de material will be deposited, tool-paths can be obtained and compiled in the g-code format. This last includes the tool-path coordinates and all the process parameters. Thus, without the need for CAD(Computer-Aided Design) software or slicers, it is possible to obtain g-code files quickly. This article reports the development of a g-code compiler software called BioScaffolds PG V2.0.; it is compatible with open-source desktop 3D printers and is oriented to be used in the 3D bioprinting field by material extrusion processes. The software was programmed using the VB.NET language and enables the scaffolds fabrication in the construction platform, inside Petri dishes, or in cell culture plates. The deposition process was also parameterized; it is calculated as a function of the tool-path and considers the mass conservation according to the printing head geometry. The graphical user interface allows easily set the process and geometrical parameters to generate a g-code file. As validated through CAM (Computer-Aided Manufacturing) simulations and hydrogel samples fabrication, the parameterized g-codes were successfully compiled. First, the hydrogel-based ink was formulated and rheologically characterized. Then, it was used to test the software in a desktop 3D printer. Once validated, the ink was used to formulate a bioink to perform a 3D bioprinting validation. The in vitro qualitative and quantitative assays were performed using Incucyte live-cell analysis up to 4 days of culture. The results showed cellular proliferation in the printed samples, which is a promising in vitro result. Then, considering that open-source 3D printers are widely used for bioprinting, this free software could help to expand and automate applications in this field.
Considering the advantages of additive manufacturing processes regarding flexibility and the possibility of producing metallic components with characteristics similar to those obtained by conventional routes, electron beam melting (EBM) has been increasingly employed and its influencing factors have been investigated. Despite its benefits, further machining operations are still necessary to provide tight dimensional and geometric tolerances, as well as proper surface finish. In this context, this work aims to determine the influence of building orientation (vertical and horizontal) on the microstructure and machinability of Ti–6Al–4V produced by EBM process and to compare the results to those obtained with the same material produced by a conventional/commercial route. For this, workpieces were characterized by an analysis of their microstructure and mechanical properties. Moreover, surface characteristics and process forces were measured in turning experiments with different cutting speeds and feeds. Although surface roughness and cutting force have not been influenced by the distinct material characteristics, higher feed and radial forces could be associated with a lower percentage of β-phase. Furthermore, considering the absence of thermal effects in hardness and tensile tests, a smaller grain size led to increased values of microhardness and tensile strength.
Usability is a key factor to well-succeeded software development. Usability assessment is crucial in the web systems development process, especially for those aimed at distance education. With the massive use of e-learning and Learning Management Systems in the educational field, it is necessary to research and propose innovative methods and techniques for evaluating the usability of these systems. This article describes the proposal and application of a new method focused on the accessibility evaluation of e-learning systems, based on the users’ profile associated with a broad set of criteria and metrics. By applying the method, the assessment results are synthesized in an indicator that represents the system’s usability level. A case study with Moodle platform was conducted, and the results point to the feasibility, limitations, and future evolution of the method.
Osteoconductive scaffolds are required to stimulate and enhance the regenerative potential of cells in bone tissue engineering applications. Additive manufacturing (AM), popularly known as 3D printing, has been widely used to fabricate these porous structures. In this study, bioceramic scaffolds based on highly bioactive glass-ceramic (Biosilicate®) were developed and characterized using a hydrogel as sacrificial ink for material extrusion 3D printing. A paste containing Biosilicate as solid filler was developed from a sacrificial ink whose formulation is based on poly(ethylene glycol) (PEG-400) with 7.5% (w/w) Laponite® nanoclay as rheological modifier. Initially, the rheological behaviors of the sacrificial ink (PL) and of the ceramic paste with 70% (v/v) Biosilicate (PL-BioS) were evaluated. Viscosity of the PL increased with addition of Biosilicate, showing a shear-thinning behavior appropriate to material extrusion 3D printing. After that, samples were 3D printed and dried at 20 and 50 °C. The dimensional characteristics of the samples were evaluated and compared, and showed that drying at 20 °C resulted in lower degree of shrinkage and mass loss before sintering. Preliminary heating stage microscopy tests were performed to define the sintering parameters, and then the scaffolds were sintered at 900 °C for 5 h at a heating rate of 1 °C/min. The sintered scaffolds were analyzed by FTIR, XRD, and SEM. These characterizations showed that the PL was eliminated from the structure with no significant change in scaffold composition, which remained intact after this process, and that the residual Laponite improved scaffold strength with formation of micropores internally to the filaments. An in vitro biological study confirmed the nontoxic behavior of the developed scaffolds on NHI-3T3 fibroblast-like cells, showing suitable cell adhesion, growth and proliferation on their surface, which are associated with good osteoconductive properties. In conclusion, the use of PL gels combined with Biosilicate is promising for ceramic ink formulation, considering that shear-thinning materials facilitate the 3D printing process. Moreover, preliminary mechanical and biological results reveal the potential of the sintered scaffolds for use in bone tissue engineering.
Amongst the different perovskites being investigated for application in solar cells, one of the most frequently scrutinized is methylammonium lead iodide CH3NH3PbI3 (or MAPbI3), which is usually obtained by the reaction of lead iodide (PbI2) with methylammonium iodide (MAI). Although this perovskite has been extensively studied and utilized in the manufacture of high-efficiency solar cells, its formation chemistry is still not well understood. Reliable experimental determination of the activation energy between PbI2 and MAI has been difficult due to the rapid reaction at room temperature. In this work, we determined the activation energy by adopting the Arrhenius equation. This was possible by controlling the reaction using MAI vapor, instead of liquid solution. This procedure allowed the reaction to be carried out at temperatures of up to 150 °C. The formation of MAPbI3 films was obtained by a two-step process: deposition of thin PbI2 film by thermal evaporation and subsequent conversion into perovskite by exposure to MAI vapor. The conversion of PbI2 to MAPbI3 as a function of temperature was probed by X-ray diffraction. An activation energy of 0.12 ± 0.02 eV was obtained. This low value explains the ease of MAPbI3 formation at low temperatures, and partially explains its instability in environmental conditions.
To meet the demands of the market and society, the development of structured polymeric materials for application in the medical field is constantly increasing. Over the last decades, metallic silver nanoparticles have been explored due to their antimicrobial action. Here, we aimed to incorporate metallic silver nanoparticles into polymeric pieces obtained by additive manufacture via a chemical route involving silver nitrate and sodium borohydride. Polyamide 12 membranes were obtained by selective laser sintering, which was followed by washing, pretreatment, and functionalization with the alkoxides tetraethylorthosilicate and 3-aminopropyl tetraethoxysilane. For nanoparticle preparation and incorporation, a chemical route was tested under different conditions. The samples were characterized by techniques, such as X-ray diffraction, ultraviolet-visible spectroscopy, and infrared vibrational spectroscopy. Nanoparticle formation and incorporation into the polyamide 12 membranes were demonstrated by the absorbance band at 420 nm, which indicated that the particles measured between 10 and 50 nm in size; by the X-ray diffraction peaks at 2θ = 38, 44, and 64°, which are typical of crystalline silver; and by vibrational spectroscopy, which evidenced that the nanoparticles interacted with the polyamide 12 nitrogen groups. Polyamide 12 membranes containing metallic silver nanoparticles have promising biomedical applications as antimicrobial wound dressings associated with drug carriers.
Transformers can produce gases dissolved in oil that can cause damage to their structures, and preventing failures caused by these gases is a goal to be reached. There is a demand for wireless sensors to monitor those gases. Alongside its development, there is a growing interest in new energy sources enabling these technologies. Triboelectric nanogenerators can gather energy from the environment, such as mechanical energy from vibrations, and convert it into electricity from the contact of two dielectric materials. In this work, the authors propose the study of a low-cost and straightforward triboelectric nanogenerator (TENG) based on ZnO nanorods as a positive dielectric material, with PDMS:GO composites at different concentrations as the negative dielectric material. All the studies were carried out in a wide frequency range varying from 45 to 250 Hz. Additionally, an analysis of the addition of a steel spring into the TENG to improve the device’s generating output is shown. A power density of 246 mV m−2 and 4 V of the output voltage was obtained using a PDMS:GO 4% (w/w) composite and a steel spring. A correlation between the “mass-spring” system and the better performance of the triboelectric device is presented. Further, vibration frequencies in several external points of the transformer walls and the device’s performance in these frequencies are shown, and the results gathered from this data are discussed.
The lack of higher performance energy storage has been widely acknowledged as a major factor hindering further developments in transportation, portable and wearable electronic devices, among other key applications. Although supercapacitors (SCs) have been known for more than fifty years, only recently these devices have been considered as promising candidates to fulfil this significant technology gap. Developments in nanotechnology and manufacturing techniques applied to high-performance advanced electrode materials have accelerated progress in this fast-moving field. In this comprehensive overview article, we systematically survey the current state of art on fabrication and the corresponding electrochemical performance of electrode materials for SCs. The text covers novel carbon nanomaterials having different dimensions, such as 0D-carbon quantum dots, 1D-carbon nanostructures (carbon nanotubes, carbon nanofibers, carbon nano yarns and their composites) as well as 2D-carbon materials (graphene, doped-graphene, graphene derivatives and their composites). Emerging fabrication technologies are also addressed, including conventional SCs, as well as asymmetric, flexible, micro, stretchable and wearable devices. Additionally, the drawbacks for each class of electrode material, the major challenges facing the current technologies, and some of the promising research directions in this field have also been discussed.
The development of blood-interacting surfaces is critical to fabricate biomaterials for medical use, such as prostheses, implants, biosensors, and membranes. For instance, thrombosis is one of the leading clinical problems when polymer-based materials interact with blood. To overcome this limitation is necessary to develop strategies that limit platelets adhesion and activation. In this work, hyaluronan (HA)/chitosan (Chi) based-films, recently reported in the literature as platforms for tumor cell capture, were developed and, subsequently, functionalized with sulfated chitosan (ChiS) using a layer-by-layer technique. ChiS, when compared to native Chi, presents the unique abilities to confer anti-thrombogenic properties, to reduce protein adsorption, and also to limit calcification. Film physicochemical characterization was carried out using FTIR and XPS for chemical composition assessment, AFM for the surface morphology, and contact angle for hydrophilicity evaluation. The deposition of ChiS monolayer promoted a decrease in both roughness and hydrophilicity of the HA/Chi films. In addition, the appearance of sulfur in the chemical composition of ChiS-functionalized films confirmed the film modification. Biological assay indicated that the incorporation of sulfated groups limited platelet adhesion, mainly because a significant reduction of platelets adhesion to ChiS-functionalized films was observed compared to HA/Chi films. On balance, this work provides a new insight for the development of novel antithrombogenic biomaterials, opening up new possibilities for devising blood-interaction surfaces.
Laser-based methodologies for synthesis, reduction, modification and assembly of graphene-based materials are highly demanded for energy-related electrodes and devices for portable electronics. Laser technologies for graphene synthesis and modification exhibit several advantages when compared to alternative methods. They are fast, low-cost and energy saving, allowing selective heating and programmable processing, with controlled manipulation over the main experimental parameters. In this review, we summarize the most recent studies on laser-assisted synthesis of graphene-based materials, as well as their modification and application as electrodes for supercapacitor and battery applications. After a brief introduction to the physical properties of graphene and a discussion of the different types of laser processing operations, the practical uses of laser techniques for the fabrication of electrode materials are discussed in detail. Finally, the review is concluded with a brief discussion of some of the outstanding problems and possible directions for research in the area of laser-based graphene materials for energy storage devices.
YAG: Ce3+ phosphor/silicone composites are widely used in solid-state lighting as a light converter to achieve white lighting. However, because of high thermal resistance and low thermal stability, the luminous performance of YAG: Ce3+ phosphor/silicone composite deteriorates rapidly when excited by high-power-density blue-laser. To explore the potential of blue laser-excited YAG: Ce3+ phosphor/silicone composites, the luminous performances under different blue laser power conditions were characterized by both the reflective and transmissive excitations using a self-built three-integrating-sphere system. Furthermore, the Monte-Carlo Ray-tracing simulation was used to illustrate the light-transmission and energy conversion mechanism in the phosphor/silicone composites. The results showed that: (1) The YAG: Ce3+ phosphor/silicone composite could be excited by the 0.292W laser light with the peak wavelength of 445nm, excessive laser power will cause phosphor thermal quenching and silicone carbonization. (2) The luminous flux of the composite under both the reflective and transmissive excitations gradually increased with the increase of phosphor concentration; correspondingly, the color coordinate moved to the yellow region, and the Correlated Color Temperature (CCT) gradually decreased. (3) The simulation results indicated that under the same phosphor concentration, the luminous flux obtained by reflection excitation was largely higher than that by the transmission excitation, as the light re-conversion and strong back-scattering were occurred in the reflective and transmissive laser excitation respectively.
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170 members
Rodrigo Rezende
  • 3D Technologies
T. Mazon
  • DMI - Divisão de Mostradores da Informação
Clenio F. Salviano
  • Divisão de Melhoria de Processo de Software
Ana Guerra
  • DSSI-Divisão de segurança e sistemas da informacao
Rodovia Dom Pedro I (SP-65), Km 143,6 - Amarais, 13069-901, Campinas, Estado de Sao Paulo, Brazil
Head of institution
Center for Information Technology Renato Archer - CTI