No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Localized 3-D Functionalization of Bionanoreceptors on High-Density Micropillar Arrays via Electrowetting
Abstract
In this work, we introduce an electrowetting-assisted 3-D biofabrication process allowing both complete and localized functionalization of bionanoreceptors onto densely arranged 3-D microstructures. Integration of biomaterials with three-dimensional (3-D) microdevice components offers exciting opportunities for communities developing miniature bioelectronics with enhanced performances and advanced modes of operation. However, most biological materials are stable only in properly conditioned aqueous solutions, thus the water-repellent properties exhibited by densely arranged micro-/nano- structures (widely known as the Cassie-Baxter state) represent a significant challenge to biomaterial integration. Here, we first investigate such potential limitations using cysteine-modified Tobacco mosaic virus (TMV1cys) as a model bionanoreceptor and a set of Au-coated Si-micropillar arrays (µPAs) of varying densities. Further, we introduce a novel biofabrication system adopting electrowetting principles for the controlled localization of TMV1cys bionanoreptors on densely arraged µPAs. Contact angle analysis and SEM characterizations provide clear evidence to indicate structural hydrophobicity as a key limiting factor for 3-D biofunctionalization, and for electrowetting as an effective method to overcome this limitation. The successful 3-D biofabrication is confirmed using SEM and fluorescence microscopy that show spatially controlled and uniform assemblies of TMV1cys on µPAs. The increased density of TMV1cys per device foot-print produces a 7-fold increase in fluorescence intensity attributed to the µPAs when compared to similar assemblies on planar substrates. Combined, this work demonstrates the potential of electrowetting as a unique enabling solution for the controlled and efficient biofabrication of 3-D patterned micro/nano domains.
... In our recent report, we have provided experimental evidence to highlight the potential limitation using cysteine-modified Tobacco mosaic virus (TMV1cys) and Au-coated Si micropillar array (μPA) electrodes. In addition, the electrowetting principle -which controls surface wettability with applied electric potential -has been introduced as an enabling technique for uniform and localized immobilization of the bionanoreceptors on densely-arranged μPA electrodes [14], [15]. ...
... (1) Figure 1d plots both theoretically expected (derived from Cassie-Baxter equation (Eq. 1) with θ0=65º, and ϕs calculated from the pillar geometry) and experimentally acquired contact angles (θ*) indicating that the hydrophobicity of the μPAs decreases with an increase in SAR. The disparity between the two can be attributed to the gentle pressure applied when loading the droplet onto the μPAs via syringe tips and hydrophilic surface (Au) inducing liquid pinning onto the pillar tips [14]. Such wetting state is only valid when there is no external disruption force due to the hydrophilicity of the Au surface. ...
... The electrowetting voltage was continuously applied during the printing process by seamlessly integrating the function generator to the metallic -nozzle and -printing bed without hindering the printing operation. Based on our previous work, a sinusoidal voltage signal of 1.2 Vrms at 10 kHz was applied to induce uniform and localized wetting of the TMV1cys ink into the μPAs [14]. All processes were conducted at room temperature with ambient humidity. ...
... [62] Given the known stability of TMV in a range of aqueous environmental conditions, many additional works have demonstrated techniques to pattern and align TMV particles by controlling the solid (device substrate) À liquid (TMV solution) interfacial properties. [54,63] Capillary forces in microfluidic channels or glass tubes have been utilized to autonomously deliver the TMV particles to pre-defined patterns [64] or to align the anisotropic particles at the liquid meniscus formed at the solid-liquid-air interface, [65] (Figure 1C,D, respectively). The latter approach leveraging the self-alignment of TMV particles at the liquid meniscus allowed long range coatings of TMV-based nanowires, demonstrating an innovative strategy for directional arrangement of the anisotropic nanoparticles. ...
... [59,66] Recent work has highlighted the limited structural wetting property as a major bottleneck in biomaterial integration with high density 3-D micro/nano structures. [63] This has been overcome by applying an electrowetting technique which selectively introduces TMV solution into targeted 3-D structures by electrically modulating surface wettability ( Figure 1E). The simple technique potentially allows uniform and selective immobilization of TMV on any 3-D substrate for enhancing biomaterial-integrated devices and systems. ...
Viruses are unique biological agents that infect living host cells through molecular delivery of a genomic cargo. Over the past two decades advancements in genetic engineering and bioconjugation technologies have allowed the unprecedented use of these “unfriendly” biological molecules, as nanoscopic platforms for the advancement of an array of nanotechnology applications. This mini‐review focuses on providing a brief summary of key demonstrations leveraging the versatile characteristics of Tobacco mosaic virus (TMV) for molecular assembly and bio‐device integration. A comprehensive discussion of genetic and chemical modification strategies along with potential limiting factors that impact the assembly of these macromolecules is presented to provide useful insights for adapting TMV as a potentially universal platform towards developing advanced nanomaterials. Additional discussions on biofabrication techniques developed in parallel to enable immobilization, alignment, and patterning of TMV‐based functional particles on solid surfaces will highlight technological innovations that can be widely adapted for creating nanoscopic device components using these engineered biomacromolecules. Further exploitation in the design of molecular specificity and assembly mechanisms and the development of highly controllable and scalable TMV‐device integration strategies will expand the library of nanoscale engineering tools that can be used for the further development of virus‐based nanotechnology platforms.
... In turn, plant viral adapter scaffolds may be immobilized efficiently on different types of sensor surfaces. Various deposition techniques for viruses and VLPs to bare and pre-treated technical surfaces have been optimized, including adsorption, spin-and convective coating, intermediate selforganization at liquid/liquid interfaces Zhang et al., 2018), electrokinetics such as electrophoresis and dielectrophoresis (Lapizco-Encinas and Rito-Palomares, 2007;Bittner et al., 2013), electrowetting (Chu et al., 2018b) or microfluidics (Zang et al., 2017). They can be applied to viral nanoparticles before or after their loading with target recognition elements to yield receptor layers of high surface densities, which may increase sensor sensitivity substantially in comparison to conventional layouts. ...
Coronavirus disease 2019 (COVID-19) is a novel human infectious disease provoked by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Currently, no specific vaccines or drugs against COVID-19 are available. Therefore, early diagnosis and treatment are essential in order to slow the virus spread and to contain the disease outbreak. Hence, new diagnostic tests and devices for virus detection in clinical samples that are faster, more accurate and reliable, easier and cost-efficient than existing ones are needed. Due to the small sizes, fast response time, label-free operation without the need for expensive and time-consuming labeling steps, the possibility of real-time and multiplexed measurements, robustness and portability (point-of-care and on-site testing), biosensors based on semiconductor field-effect devices (FEDs) are one of the most attractive platforms for an electrical detection of charged biomolecules and bioparticles by their intrinsic charge. In this review, recent advances and key developments in the field of label-free detection of viruses (including plant viruses) with various types of FEDs are presented. In recent years, however, certain plant viruses have also attracted additional interest for biosensor layouts: Their repetitive protein subunits arranged at nanometric spacing can be employed for coupling functional molecules. If used as adapters on sensor chip surfaces, they allow an efficient immobilization of analyte-specific recognition and detector elements such as antibodies and enzymes at highest surface densities. The display on plant viral bionanoparticles may also lead to long-time stabilization of sensor molecules upon repeated uses and has the potential to increase sensor performance substantially, compared to conventional layouts. This has been demonstrated in different proof-of-concept biosensor devices. Therefore, richly available plant viral particles, non-pathogenic for animals or humans, might gain novel importance if applied in receptor layers of FEDs. These perspectives are explained and discussed with regard to future detection strategies for COVID-19 and related viral diseases.
... After thermal curing or light curing, the polymerbased microstructures can be obtained and the shape of the fabricated microstructures were mainly determined by the structural design of the molds. For user-defined microstructure fabrication, this process is usually quite time-consuming and cost expensive to design and manufacture the molds, and thus limits the application of this method for polymerbased microstructure fabrication [10]. The 3D printing process enables the construction of microstructures with considerable flexibility in morphology, and can be divided into two groups: extrusion-based and projection-based 3D printing. ...
Polymer-based substrate with patterned microstructures has been widely utilized for the development of cell chip in tissue engineering and/or flexible sensors in robotics. The key challenge is to fabricate the polymer-based substrate with the localized patterned microstructures. In this study, we presented a method to fabricate localized microstructures by standing surface acoustic wave (SSAW) and user-defined waveguides. To investigate the working mechanism, we developed a 3D numerical model to analyze the induced acoustic pressure distribution and final generated microstructures. Results demonstrated that the utilized waveguide could localize the acoustic pressure field in a specified region within the prepared photosensitive fluid film based on Rayleigh’s radiation theory and capillary wave motion. By adjusting the SSAW driven modes and using different shaped waveguides, both numerical modeling and experimental tests showed that the localized microstructures can form on the liquid film and then successfully fabricated using ultraviolet (UV) solidification. Therefore, our developed method by using the SSAW and waveguide provides a promising alternative process to fabricate the polymer-based microstructure with localized patterns, and the fabricated polymer-based microstructures could be used for the development of flexible sensors, actuator, and/or soft robotics in future applications.
... In this work, we have incorporated a sequential biomolecular assembly into a recently developed electro-bioprinting (EBP) technique [7] to demonstrate a "print-assembly" approach as a highly scalable, efficient, and customizable manufacturing method for assembling functional biomacromolecules. The EBP, originally developed by our group to achieve uniform biomolecule functionalization on 3-D transducers, also allows scalable loading of biomolecules onto 3-D electrode surfaces by varying the micropillar array (μPA) density. ...
... As biofilm formation on surfaces is driven by bacterial adherence followed by inter-molecular communication, a promising strategy for mitigating surface fouling events has been the development of non-adherent, superhydrophobic surface coatings displaying micro/nanoscale surface structures that could potentially help disrupt bacterial adherence or communication [10]. In our recent work, we have developed a 3-D electro-bioprinting (3-D EBP) technique that allows assembly of hierarchical surface topology with high scalability by combining the bottom-up assembly of biological nanoscaffolds (BNS), cysteine-modified Tobacco mosaic virus (TMV1cys), with top-down fabricated microstructures [11]. In an effort to leverage this manufacturing capability for studying the potential relationships between hydrophobic 3-D micro-/nano-scale surface topologies and biofilm growth, this work has focused on developing hydrophobic coating strategies over TMV-templated nanostructures and characterizing their performance in mitigating biofilm growth. ...
Eukaryotic cells possess the remarkable ability to sense and respond to mechanical cues from their extracellular environment, a phenomenon known as mechanobiology, which is crucial for the proper functioning of biological systems. Micropillars have emerged as a prominent tool for quantifying cellular forces and have demonstrated versatility beyond force measurement, including the modulation of the extracellular environment and the facilitation of mechano‐stimulation. In this comprehensive review, innovative strategies in micropillars’ design, fabrication, characterization, and biosensing applications are explored. The review begins with a foundational overview of micropillar‐based cell mechanobiology studies to provide a complete understanding, and then it delves into novel methodologies within each domain. The latter part of the review unveils innovative micropillars’ applications beyond mechanobiology, such as their use in enhancing biosensing surfaces and as upstream fluid manipulators for biosensors. Finally, in this review, future research directions are discussed and the current limitations of these techniques are outlined. Despite the extensive exploration of micropillar applications, a significant gap remains between research advancements and the practical implementation of micropillars in point‐of‐care diagnostics. Bridging this gap is crucial for translating laboratory innovations into real‐world medical and diagnostic tools.
Electrowetting-on-dielectric (EWOD) technology has been considered as a promising candidate for digital microfluidic (DMF) applications due to its outstanding flexibility and integrability. The dielectric layer with a hydrophobic surface is the key element of an EWOD device, determining its driving voltage, reliability, and lifetime. Hereby, inspired by the ionic-liquid-filled structuring polymer with high capacitance independent on thickness, namely ion gel (IG), we develop a polymer (P)-ion gel-amorphous fluoropolymer, namely, PIGAF, composite film as a replaceable hydrophobic dielectric layer for fabrication of a high-efficiency and stable EWOD-DMF device at relatively low voltage. The results show that the proposed EWOD devices using the PIGAF-based dielectric layer can achieve a large contact angle (θ) change of ∼50° and excellent reversibility with a contact angle hysteresis of ≤5° at a relatively low voltage of 30 Vrms. More importantly, the EWOD actuation voltage did not change obviously with the PIGAF film thickness in the range of several to tens of microns, enabling the thickness of the film to be adjusted according to the demand within a certain range while keeping the actuation voltage low. An EWOD-DMF device can be prepared by simply stacking a PIGAF film onto a PCB board, demonstrating stable droplet actuation (motion) at 30 Vrms and 1 kHz as well as a maximum moving velocity of 69 mm/s at 140 Vrms and 1 kHz. The PIGAF film was highly stable and reliable, maintaining excellent EWOD performance after multiple droplet manipulations (≥50 cycles) or long-term storage of 1 year. The proposed EWOD-DMF device has been demonstrated for digital chemical reactions and biomedical sensing applications.
Polymer-based substrate with region-selective microstructures are crucial for many biomedical applications. Here, we explored a novel method based on standing surface acoustic waves (SSAWs) for the fabrication of localized polymer-based microstructures via a predefined waveguide. By exciting the SSAWs, the generated acoustic pressure field can be controlled in a pre-determined region of the fluid surface through controlling the size and shape of the waveguide geometry. Based on the capillary wave motion, the generated acoustic pressure field can excite micro-wavy patterned structures on the surface. Then, using ultraviolet (UV) solidification, the polymer-based substrates with region-selective patterned microstructures can be successfully fabricated. Both finite element modelling and experimental studies demonstrated that the polymer substrate with different region-selective microstructures can be achieved by selecting the pairs of interdigital transducers (IDTs) and shapes of the predefined waveguides. The results showed that the proposed method is effective for fabricating polymer-based substrate with region-selective microstructures and may have potential in cell-laden chips for tissue engineering, cell-cell interactions, and other biomedical applications.
Biosensors are extensively employed for diagnosing a broad array of diseases and disorders in clinical settings worldwide. The implementation of biosensors at the point-of-care (POC), such as at primary clinics or the bedside, faces impediments because they may require highly trained personnel, have long assay times, large sizes, and high instrumental cost. Thus, there exists a need to develop inexpensive, reliable, user-friendly, and compact biosensing systems at the POC. Biosensors incorporated with photonic crystal (PC) structures hold promise to address many of the aforementioned challenges facing the development of new POC diagnostics. Currently, PC-based biosensors have been employed for detecting a variety of biotargets, such as cells, pathogens, proteins, antibodies, and nucleic acids, with high efficiency and selectivity. In this review, we provide a broad overview of PCs by explaining their structures, fabrication techniques, and sensing principles. Furthermore, we discuss recent applications of PC-based biosensors incorporated with emerging technologies, including telemedicine, flexible and wearable sensing, smart materials and metamaterials. Finally, we discuss current challenges associated with existing biosensors, and provide an outlook for PC-based biosensors and their promise at the POC.
Phenanthriplatin, cis-[Pt(NH3)2Cl(phenanthridine)](NO3), is a cationic monofunctional DNA-binding platinum(II) anticancer drug candidate with unusual potency and cellular response profiles. Its in vivo efficacy has not yet been demonstrated, highlighting the need for a delivery system. Here we report tobacco mosaic virus (TMV) as a delivery system for phenanthriplatin. TMV forms hollow nanotubes with a polyanionic interior surface; capitalizing on this native structure, we developed a one-step phenanthriplatin loading protocol. Phenanthriplatin release from the carrier is induced in acidic environments. This delivery system, designated PhenPt-TMV, exhibits matched efficacy in a cancer cell panel compared to free phenanthriplatin. In vivo tumor delivery and efficacy was confirmed using a mouse model of triple negative breast cancer. Tumors treated with PhenPt-TMV were 4x smaller than tumors treated with free phenanthriplatin or cisplatin, due to increased accumulation of phenanthriplatin within the tumor tissue. The biology-derived TMV delivery system may facilitate translation of phenanthriplatin into the clinic.
Micro-contact printing, μCP, is a well-established soft-lithography technique for printing biomolecules. μCP uses stamps made of Poly(dimethylsiloxane), PDMS, made by replicating a microstructured silicon master fabricated by semiconductor manufacturing processes. One of the problems of the μCP is the difficult control of the printing process, which, because of the high compressibility of PDMS, is very sensitive to minute changes in the applied pressure. This over-sensitive response leads to frequent and/or uncontrollable collapse of the stamps with high aspect ratios, thus decreasing the printing accuracy and reproducibility. Here we present a straightforward methodology of designing and fabricating PDMS structures with an architecture which uses the collapse of the stamp to reduce, rather than enlarge the variability of the printing. The PDMS stamp, organized as an array of pyramidal micro-posts, whose ceiling collapses when pressed on a flat surface, replicates the structure of the silicon master fabricated by anisotropic wet etching. Upon application of pressure, depending on the size of, and the pitch between, the PDMS pyramids, an air gap is formed surrounding either the entire array, or individual posts. The printing technology, which also exhibits a remarkably low background noise for fluorescence detection, may find applications when the clear demarcation of the shapes of protein patterns and the distance between them are critical, such as microarrays and studies of cell patterning.
Electronic supplementary material
The online version of this article (doi:10.1007/s10544-016-0036-4) contains supplementary material, which is available to authorized users.
Tobacco mosaic virus (TMV) is a robust nanotubular nucleoprotein scaffold increasingly employed for the high density presentation of functional molecules such as peptides, fluorescent dyes, and antibodies. We report on its use as advantageous carrier for sensor enzymes. A TMV mutant with a cysteine residue exposed on every coat protein (CP) subunit (TMVCys) enabled the coupling of bifunctional maleimide-polyethylene glycol (PEG)-biotin linkers (TMVCys/Bio). Its surface was equipped with two streptavidin [SA]-conjugated enzymes: glucose oxidase ([SA]-GOx) and horseradish peroxidase ([SA]-HRP). At least 50% of the CPs were decorated with a linker molecule, and all thereof with active enzymes. Upon use as adapter scaffolds in conventional “high-binding” microtiter plates, TMV sticks allowed the immobilization of up to 45-fold higher catalytic activities than control samples with the same input of enzymes. Moreover, they increased storage stability and reusability in relation to enzymes applied directly to microtiter plate wells. The functionalized TMV adsorbed to solid supports showed a homogeneous distribution of the conjugated enzymes and structural integrity of the nanorods upon transmission electron and atomic force microscopy. The high surface-increase and steric accessibility of the viral scaffolds in combination with the biochemical environment provided by the plant viral coat may explain the beneficial effects. TMV can, thus, serve as a favorable multivalent nanoscale platform for the ordered presentation of bioactive proteins.
The statics and dynamics of electrowetting on pillar-arrayed surfaces at nanoscale are studied by using molecular dynamics simulations. Under a gradually increased electric field, the droplet is pushed by the electromechanical force to spread, and goes through the Cassie state, Cassie-to-Wenzel wetting transition and Wenzel state, which can be characterized by the electrowetting number at microscale ηm. The expansion of liquid is direction-dependent influenced by the surface topology. A positive voltage is induced in the bulk droplet, while a negative one is induced in the liquid confined in the pillars, which makes the liquid hard to spread and be further polarized. Based on the molecular kinetic theory and the wetting states, theoretical models are proposed to comprehend the physical mechanisms in the statics and dynamics of electrowetting, and are validated by our simulations. Our findings may help to understand the electrowetting on microtextured surfaces and assist the future design of engineered surfaces in practical applications.
New microproducts need the utilization of a diversity of materials and have complicated three-dimensional (3D) microstructures with high aspect ratios. To date, many micromanufacturing processes have been developed but specific class of such processes are applicable for fabrication of functional and true 3D microcomponents/assemblies. The aptitude to process a broad range of materials and the ability to fabricate functional and geometrically complicated 3D microstructures provides the additive manufacturing (AM) processes some profits over traditional methods, such as lithography-based or micromachining approaches investigated widely in the past. In this paper, 3D micro-AM processes have been classified into three main groups, including scalable micro-AM systems, 3D direct writing, and hybrid processes, and the key processes have been reviewed comprehensively. Principle and recent progress of each 3D micro-AM process has been described, and the advantages and disadvantages of each process have been presented.
A thin film sensor for the detection of volatile organic compounds (VOC) was fabricated by deposition of oligo-aniline grafted tobacco mosaic virus (TMV) onto a glass substrate. The oligo-aniline motifs were conjugated onto the TMV surface by a traditional diazonium coupling reaction to tyrosine residues followed by Cu(I) catalyzed alkyne-azidecycloaddition (CuAAC) reaction. The modified TMV was easily fabricated into a thin film by directly drop coating onto a glass substrate. Upon integration of the glass substrate into a prototypical device, the virus-based thin film exhibited good sensitivity and selectivity toward ethanol and methanol vapour.
Electrowetting has become one of the most widely used tools for manipulating tiny amounts of liquids on surfaces. Applications range from 'lab-on-a-chip' devices to adjustable lenses and new kinds of electronic displays. In the present article, we review the recent progress in this rapidly growing field including both fundamental and applied aspects. We compare the various approaches used to derive the basic electrowetting equation, which has been shown to be very reliable as long as the applied voltage is not too high. We discuss in detail the origin of the electrostatic forces that induce both contact angle reduction and the motion of entire droplets. We examine the limitations of the electrowetting equation and present a variety of recent extensions to the theory that account for distortions of the liquid surface due to local electric fields, for the finite penetration depth of electric fields into the liquid, as well as for finite conductivity effects in the presence of AC voltage. The most prominent failure of the electrowetting equation, namely the saturation of the contact angle at high voltage, is discussed in a separate section. Recent work in this direction indicates that a variety of distinct physical effects---rather than a unique one---are responsible for the saturation phenomenon, depending on experimental details. In the presence of suitable electrode patterns or topographic structures on the substrate surface, variations of the contact angle can give rise not only to continuous changes of the droplet shape, but also to discontinuous morphological transitions between distinct liquid morphologies. The dynamics of electrowetting are discussed briefly. Finally, we give an overview of recent work aimed at commercial applications, in particular in the fields of adjustable lenses, display technology, fibre optics, and biotechnology-related microfluidic devices.
A superhydrophobic surface is a surface with a water contact angle close to or higher than 150°. In this feature article, we review the historical and present research on superhydrophobic surfaces, including the characterization of superhydrophobicity, different ways to fabricate rough surfaces, and low-surface-energy modifications on inorganic and organic rough surfaces. It is the combination of surface roughness and low-surface-energy modification that leads to superhydrophobicity. Notably, research on superhydrophobic surfaces has not only fundamental interest but various possible functional applications in micro- and nano-materials and devices.
The meniscus between two immiscible liquids can be used as an optical lens. A change in curvature of this meniscus by electrowetting leads to a change in focal distance. It is demonstrated that two liquids in a tube form a self-centered lens with a high optical quality. The motion of the lens during a focusing action was studied by observation through the transparent tube wall. Finally, a miniature achromatic camera module was designed and constructed based on this adjustable lens, showing that it is excellently suited for use in portable applications.
The realization of next-generation portable electronics and integrated microsystems is directly linked with the development of robust batteries with high energy and power density. Three-dimensional micro- and nanostructured electrodes enhance energy and power through higher surface area and thinner active materials, respectively. Here, we present a novel approach for the fabrication of hierarchical electrodes that combine benefits of both length scales. The electrodes consist of self-assembled, virus-templated nanostructures conformally coating three-dimensional micropillars. Active battery material (V(2)O(5)) is deposited using atomic layer deposition on the hierarchical micro/nanonetwork. Electrochemical characterization of these electrodes indicates a 3-fold increase in energy density compared to nanostructures alone, in agreement with the surface area increase, while maintaining the high power characteristics of nanomaterials. Investigation of capacity scaling for varying active material thickness reveals underlying limitations in nanostructured electrodes and highlights the importance of our method in controlling both energy and power density with structural hierarchy.
The use of paper as a material for various device applications (such as microfluidics and energy storage) is very attractive given its flexibility, versatility, and low cost. Here we demonstrate that electrowetting (EW) devices can be readily fabricated on paper substrates. Several categories of paper have been investigated for this purpose, with the surface coating, roughness, thickness, and water uptake, among the most important properties. The critical parameter for EW devices is the water contact angle (CA) change with applied voltage. EW devices on paper exhibit characteristics very close to those of conventional EW devices on glass substrates. This includes a large CA change in oil ambient (90-95°), negligible hysteresis (∼2°), and fast switching times of ∼20 ms. These results indicate the promise of low-cost paper-based EW devices for video rate flexible e-paper on paper.
Advances in microarray technology enable massive parallel mining of biological data, with biological chips providing hybridization-based expression monitoring, polymorphism detection and genotyping on a genomic scale. Microarrays containing sequences representative of all human genes may soon permit the expression analysis of the entire human genome in a single reaction. These 'genome chips' will provide unprecedented access to key areas of human health, including disease prognosis and diagnosis, drug discovery, toxicology, aging, and mental illness. Microarray technology is rapidly becoming a central platform for functional genomics.
Dip-pen nanolithography was used to construct arrays of proteins with 100- to 350-nanometer features. These nanoarrays exhibit
almost no detectable nonspecific binding of proteins to their passivated portions even in complex mixtures of proteins, and
therefore provide the opportunity to study a variety of surface-mediated biological recognition processes. For example, reactions
involving the protein features and antigens in complex solutions can be screened easily by atomic force microscopy. As further
proof-of-concept, these arrays were used to study cellular adhesion at the submicrometer scale.
Understanding the complementary roles of surface energy and roughness on natural nonwetting surfaces has led to the development of a number of biomimetic superhydrophobic surfaces, which exhibit apparent contact angles with water greater than 150 degrees and low contact angle hysteresis. However, superoleophobic surfaces-those that display contact angles greater than 150 degrees with organic liquids having appreciably lower surface tensions than that of water-are extremely rare. Calculations suggest that creating such a surface would require a surface energy lower than that of any known material. We show how a third factor, re-entrant surface curvature, in conjunction with chemical composition and roughened texture, can be used to design surfaces that display extreme resistance to wetting from a number of liquids with low surface tension, including alkanes such as decane and octane.
Three-dimesional hierarchical electrodes exhibiting multi-dimensional geometries provide exceptional advantages for advanced energy storage performance. In this work, we report the fabrication and characterization of biotemplated hierarchical-Ni/NiO electrodes enabled by thermal oxidation of electroless Ni-coated Tobacco mosaic viruses (TMVs) self-assembled on Au-coated Si micropillar arrays. Uniform NiO formation on the metallized TMV nanoscaffolds is characterized by XPS and STEM-EELS analysis and the electrochemical performance was characterized in 2 M KOH solution. The hierarchical-Ni/NiO show a 3.3 and 32.6 times increase in areal capacity (81.4 μAh cm⁻²) compared to solely nanostructured (24.3 μAh cm⁻²) and planar electrodes (2.5 μAh cm⁻²), respectively. The NiO electrodes show interesting capacity increase phenomenon during the initial activation cycles. Based on our experimental analysis, it is attributed to both an increase in active surface area/mesoporosity and NiO content during the initial charge/discharge cycles, and the increase has dependence on electrode geometry. The hierarhical-Ni/NiO electrode exhibit excellent cycle stability up to 1500 charge/discharge cycles at 2 mA cm⁻² with no capacity fading. Based on the results, the hierarchical-Ni/NiO is a promising candidate for advanced electrochemical energy storage devices.
Following the development of microfluidic systems, there has been a high tendency towards developing lab-on-a-chip devices for biochemical applications. A great deal of effort has been devoted to improve and advance these devices with the goal of performing complete sets of biochemical assays on the device and possibly developing portable platforms for point of care applications. Among the different microfluidic systems used for such a purpose, digital microfluidics (DMF) shows high flexibility and capability of performing multiplex and parallel biochemical operations, and hence, has been considered as a suitable candidate for lab-on-a-chip applications. In this review, we discuss the most recent advances in the DMF platforms, and evaluate the feasibility of developing multifunctional packages for performing complete sets of processes of biochemical assays, particularly for point-of-care applications. The progress in the development of DMF systems is reviewed from eight different aspects, including device fabrication, basic fluidic operations, automation, manipulation of biological samples, advanced operations, detection, biological applications, and finally, packaging and portability of the DMF devices. Success in developing the lab-on-a-chip DMF devices will be concluded based on the advances achieved in each of these aspects.
This paper presents a comprehensive study of the self-assembly dynamics and the biosensing efficacy of Tobacco mosaic virus-like particle (TMV VLP) sensing probes using an impedimetric microsensor platform. TMV VLPs are high surface area macromolecules with nanorod structures constructed from helical arrangements of thousands of identical coat proteins. Genetically modified TMV VLPs express both surface attachment-promoting cysteine residues and FLAG-tag antibody binding peptides on their coat protein outer surfaces, making them selective biosensing probes with self-assembly capability on sensors. The VLP self-assembly dynamics were studied by the continuous monitoring of impedance changes at 100 Hz using interdigitated impedimetric microsensors. Electrical impedance spectroscopy revealed VLP saturation on impedance sensor surface with the coverage of 68% in self-assembly process. The VLP-functionalized impedance sensors responded to 12 ng/ml to 1.2 μg/ml of target anti-FLAG IgG antibodies in the subsequent enzyme-linked immunosorbent assays (ELISA), and yielded 18–35% total impedance increases, respectively. The detection limit of the target antibody is 9.1 ng/ml using the VLP-based impedimetric microsensor. These results highlight the significant potential of genetically modified VLPs as selective nanostructured probes for autonomous sensor functionalization and enhanced biosensing.
Virus particles and proteins are excellent examples of naturally occurring structures with well-defined nanoscale architectures, for example, cages and tubes. These structures can be employed in a bottom-up assembly strategy to fabricate repetitive patterns of hybrid organic–inorganic materials. In this paper, we review methods of assembly that make use of protein and virus scaffolds to fabricate patterned nanostructures with very high spatial control. We chose (apo)ferritin and tobacco mosaic virus (TMV) as model examples that have already been applied successfully in nanobiotechnology. Their interior space and their exterior surfaces can be mineralized with inorganic layers or nanoparticles. Furthermore, their native assembly abilities can be exploited to generate periodic architectures for integration in electrical and magnetic devices. We introduce the state of the art and describe recent advances in biomineralization techniques, patterning and device production with (apo)ferritin and TMV.
Enzymatic biofuel cells are bioelectronic devices that utilize oxidoreductase enzymes to catalyze the conversion of chemical energy into electrical energy. This review details the advancements in the field of enzymatic biofuel cells over the last 30 years. These advancements include strategies for improving operational stability and electrochemical performance, as well as device fabrication for a variety of applications, including implantable biofuel cells and self-powered sensors. It also discusses the current scientific and engineering challenges in the field that will need to be addressed in the future for commercial viability of the technology.
Copyright © 2015 Elsevier B.V. All rights reserved.
We have developed a novel platform comprising a three-dimensional micropillar sensor array that can be encapsulated with high-k dielectric material for applications in capacitive neural sensing. The present device incorporates over 3,800 micropillar electrodes, grouped into 60 independent sensor clusters (for compatibility with existing electronics), spread over an area of 750 μm2. Each sensor cluster site consists of an 8x8 array of micropillars, interconnected by a lead to an output pad of the device. Individual 3D pillars are 3 μm in diameter with a height of 8 μm. Our experience suggests that such microstructured probes can achieve more intimate contact with the surface of neural tissue and enhance the quality of neuronal recordings. Impedance spectroscopy at 1 kHz measured average magnitude and phase shift of 710 W and 17°, respectively, for a single sensor site. These values confirm that our process allows robust fabrication of highly conductive 3D microelectrodes. The device showed good consistency across all 60 Pt electrode clusters during initial characterization and when interfaced with retinal tissue. Such a device was then encapsulated with a layer of HfO2 by atomic layer deposition. Subsequent impedance spectroscopy showed a shift in impedance and phase towards capacitive behavior. The results shown here demonstrate high-density, three-dimensional microfabrication technology that can be applied to the development of advanced capacitive sensor arrays for neural tissue.
A high performance three-dimensional (3D) electrochemical immunosensor was developed for sensitive detection of the tumor biomarker, carcinoembryonic antigen (CEA). Monolithic and macroporous graphene foam grown by chemical vapor deposition (CVD) served as the scaffold of the free-standing 3D electrode. Immuno-recognition interface was fabricated via simple and non-covalent immobilization of antibody using lectin-mediated strategy. Briefly, the well-known lectin macromolecule (concanavalin A, Con A) monolayer was functionalized on 3D graphene (3D-G) using in-situ polymerized polydopamine as the linker. Then the widely used horseradish peroxidase (HRP)-labeled antibody (anti-CEA) in immunoassays was efficiently immobilized to demonstrate the recognition interface via the biospecific affinity of lectin with sugarprotein. The 3D immunosensor is able to detect CEA with a wide linear range (0.1-750.0ngml(-1)), low detection limit (~90pgml(-1) at a signal-to-noise ratio of 3), and short incubation time (30min). Furthermore, this biosensor was used for the detection of the CEA level in real serum samples.
Copyright © 2014 Elsevier B.V. All rights reserved.
A three-dimensional (3D) microarray of a gold modified electrode with a nanoporous surface was successfully fabricated in this work. The special gold micro/nanostructure possessed an extremely high surface area (ca. 20 times its geometrical area), as well as highly stable and easily chemically modified properties, which could distinctly increase the binding sites for biological probes, facilitate the diffusion profile and enhance the electron transfer. Owing to these advantages, an ultrasensitive biosensor was designed on the porous microarray of the gold modified electrode (PMGE), which realized the simultaneous assay of cancer biomarkers of angiogenin (Ang) and thrombin (Tob). Under optimal experimental conditions, an impressively ultralow detection limit of 0.07 pM for Ang (a linear range from 0.2 pM to 10 nM) and a limit of 20 fM for Tob (a linear range from 50 fM to 5 nM) were obtained. Besides, the fabricated biosensor showed an excellent stability, good reproducibility and a high selectivity towards other biological proteins, which also exhibited promising potential for the application in a real serum sample analysis. Such a micro/nanostructure of gold could have widespread applications in biological sensing and quantitative biochemical analysis.
Teflon AF®, an amorphous copolymer of polytetrafluoroethylene (PTFE) with 2,2-bis(triflouromethyl)-4,5-difluoro-1, 3-dioxole, has been receiving widespread attention in the opto-electronics industries and elsewhere for its superior optical and dielectric properties. The objective of the present study was to investigate surface parameters that may be required for the application of thin films of Teflon AF® in the fields of biomaterials and bioelectronics. Using standard microelectronics procedures, micro-patterned thin films of Teflon-AF® were fabricated, and their surface properties monitored and optimized with the aid of highly surface sensitive spectrometric techniques. Finally, their capability to inhibit or bio-pattern cell adhesion was tested with various neural cell lines.
High-density ferritin nanopatterning - the protein and core complex - on a silicon substrate was achieved using nanometric patterns of amino-group modification. These patterns were made through a combination of EB lithography and vapor-phase deposition of 3-aminopropyltriethoxysilane (APTES). An appropriate buffer solution, with respect to pH and Debye length, suppressed ferritin adsorption on the SiO2 underlayer while ferritins were adsorbed with high density on a nanometer-size APTES layer. We obtained 50-nm patterned ferritins by using a solution with a 1000-nm Debye length (pH 7.0); with this solution, the attractive ferritin-APTES interaction seemed to be strong enough to overcome the repulsive ferritin-SiO2 interaction.
This study explores how surface morphology affects the dynamics of contact line depinning of an evaporating sessile droplet on micropillared superhydrophobic surfaces. The result shows that neither a liquid-solid contact area nor an apparent contact line is a critical physical parameter to determine the depinning force. The configuration of a contact line on a superhydrophobic surface is multimodal, composed of both two phases (liquid and air) and three phases (liquid, solid, and air). The multimodal state is dynamically altered when a droplet recedes. The maximal three-phase contact line attainable along the actual droplet boundary is found to be a direct and linear parameter that decides the depinning force on the superhydrophobic surface.
Well-ordered arrays of pits were prepared on gallium arsenide and silicon wafers using a finely focused ion beam (FFIB). The defect pits on gallium arsenide, examined with tapping mode scanning force microscopy (TM-SFM), had a rim diameter of 60 nm and were spaced 185 nm apart. TM-SFM images showed that human serum albumin (HSA) adsorption was highly specific to the inner portion of the rims of the pits on gallium arsenide, while there was no specific adsorption to the rims of pits on silica. This study demonstrates that a controlled spatial distribution of adsorbed proteins can be achieved on a nanometer scale and that the choice of material is of importance. Moreover, surface features such as pits and lines produced by FFIB can serve as a guide to easily reposition the TM-SFM probe tip at a specific location on the surface to within a few nanometers after temporary removal of the sample from the microscope.
The potential of aptamers as ligand binding molecule has opened new avenues in the development of biosensors for cancer oncoproteins. In this paper, a label-free detection strategy using signaling aptamer/protein binding complex for platelet-derived growth factor (PDGF-BB) oncoprotein detection is reported. The detection mechanism is based on the release of fluorophore (TOTO intercalating dye) from the target binding aptamer's stem structure when it captures PDGF. Amino-terminated three-dimensional carbon microarrays fabricated by pyrolyzing patterned photoresist were used as a detection platform. The sensor showed near linear relationship between the relative fluorescence difference and protein concentration even in the sub-nanomolar range with an excellent detection limit of 5pmol. This detection strategy is promising in a wide range of applications in the detection of cancer biomarkers and other proteins.
The development of nanostructured nickel–zinc microbatteries utilizing the Tobacco mosaic virus (TMV) is presented in this paper. The TMV is a high aspect ratio cylindrical plant virus which has been used to increase the active electrode area in MEMS-fabricated batteries. Genetically modifying the virus to display multiple metal binding sites allows for electroless nickel deposition and self-assembly of these nanostructures onto gold surfaces. This work focuses on integrating the TMV deposition and coating process into standard MEMS fabrication techniques as well as characterizing nickel–zinc microbatteries based on this technology. Using a microfluidic packaging scheme, devices with and without TMV structures have been characterized. The TMV modified devices demonstrated charge–discharge operation up to 30 cycles reaching a capacity of 4.45 µAh cm −2 and exhibited a six-fold increase in capacity during the initial cycle compared to planar electrode geometries. The effect of the electrode gap has been investigated, and a two-fold increase in capacity is observed for an approximately equivalent decrease in electrode spacing.
Electrowetting on micro-patterned layers of SU-8 photoresist with an amorphous Teflon® coating has been observed. The cosine of the contact angle is shown to be proportional to the square of the applied voltage for increasing bias. However, this does not apply below 40 V and we suggest that this may be explained in terms of penetration of fluid into the pattern of the surface. Assuming that the initial application of a bias voltage converts the drop from Cassie-Baxter to Wenzel regime, we have used this as a technique to estimate the roughness factor of the surface.
The last century witnessed spectacular advances in both microelectronics and biotechnology yet there was little synergy between the two. A challenge to their integration is that biological and electronic systems are constructed using divergent fabrication paradigms. Biology fabricates bottom-up with labile components, while microelectronic devices are fabricated top-down using methods that are 'bio-incompatible'. Biofabrication--the use of biological materials and mechanisms for construction--offers the opportunity to span these fabrication paradigms by providing convergent approaches for building the bio-device interface. Integral to biofabrication are stimuli-responsive materials (e.g. film-forming polysaccharides) that allow directed assembly under near physiological conditions in response to device-imposed signals. Biomolecular engineering, through recombinant technology, allows biological components to be endowed with information for assembly (e.g. encoded in a protein's amino acid sequence). Finally, self-assembly and enzymatic assembly provide the mechanisms for construction over a hierarchy of length scales. Here, we review recent advances in the use of biofabrication to build the bio-device interface. We anticipate that the biofabrication toolbox will expand over the next decade as more researchers enlist the unique construction capabilities of biology. Further, we look forward to observing the application of this toolbox to create devices that can better diagnose disease, detect pathogens and discover drugs. Finally, we expect that biofabrication will enable the effective interfacing of biology with electronics to create implantable devices for personalized and regenerative medicine.
Large biomolecules are attractive templates for the synthesis of metal1-7 and inorganic8-10 compound nanostructures. The well-defined chemical and structural heterogeneity of the biotemplates can be exploited for the precise control of the size and shape of the formed nanostructures. Here, we demonstrate that the central channel of the tobacco mosaic virus (TMV) can be used as a template to synthesize nickel and cobalt nanowires only a few atoms in diameter, with lengths up to the micrometer range.
The possibility of effective control of the wetting properties of a nanostructured surface consisting of arrays of amorphous carbon nanoparticles capped on carbon nanotubes using the electrowetting technique is demonstrated. By analyzing the electrowetting curves with an equivalent circuit model of the solid/liquid interface, the long-standing problem of control and monitoring of the transition between the "slippy" Cassie state and the "sticky" Wenzel states is resolved. The unique structural properties of the custom-designed nanocomposites with precisely tailored surface energy without using any commonly utilized low-surface-energy (e.g., polymer) conformal coatings enable easy identification of the occurrence of such transition from the optical contrast on the nanostructured surfaces. This approach to precise control of the wetting mode transitions is generic and has an outstanding potential to enable the stable superhydrophobic capability of nanostructured surfaces for numerous applications, such as low-friction microfluidics and self-cleaning.
Teflon AF, an amorphous copolymer of polytetrafluoroethylene (PTFE) with 2,2-bis(triflouromethyl)-4,5-difluoro-1, 3-dioxole, has been receiving widespread attention in the opto-electronics industries and elsewhere for its superior optical and dielectric properties. The objective of the present study was to investigate surface parameters that may be required for the application of thin films of Teflon AF in the fields of biomaterials and bioelectronics. Using standard microelectronics procedures, micro-patterned thin films of Teflon-AF were fabricated, and their surface properties monitored and optimized with the aid of highly surface sensitive spectrometric techniques. Finally, their capability to inhibit or bio-pattern cell adhesion was tested with various neural cell lines.
It is well known that the roughness of a hydrophobic solid enhances its hydrophobicity. The contact angle of water on such flat solids is typically of the order of 100 to 120 degrees, but reaches values as high as 160 to 175 degrees if they are rough or microtextured. This result is remarkable because such behaviour cannot be generated by surface chemistry alone. Two distinct hypotheses are classically proposed to explain this effect. On one hand, roughness increases the surface area of the solid, which geometrically enhances hydrophobicity (Wenzel model). On the other hand, air can remain trapped below the drop, which also leads to a superhydrophobic behaviour, because the drop sits partially on air (Cassie model). However, it is shown here that both situations are very different from their adhesive properties, because Wenzel drops are found to be highly pinned. In addition, irreversible transitions can be induced between Cassie and Wenzel states, with a loss of the anti-adhesive properties generally associated with superhydrophobicity.
In this work, for the first time, a dynamic electrical control of the wetting behavior of liquids on nanostructured surfaces, which spans the entire possible range from the superhydrophobic behavior to nearly complete wetting, has been demonstrated. Moreover, this kind of dynamic control was obtained at voltages as low as 22 V. We have demonstrated that the liquid droplet on a nanostructured surface exhibits sharp transitions between three possible wetting states as a function of applied voltage and liquid surface tension. We have examined experimentally and theoretically the nature of these transitions. The reported results provide novel methods of manipulating liquids at the microscale.
Electrowetting (EW) is a powerful tool to control fluid motion at the microscale and has promising applications in the field of microfluidics. The present work analyzes the influence of an electrowetting voltage in determining and altering the state of a static droplet resting on a rough surface. An energy-minimization-based modeling approach is used to analyze the influence of interfacial energies, surface roughness parameters, and electric fields in determining the apparent contact angle of a droplet in the Cassie and Wenzel states under the influence of an EW voltage. The energy-minimization-based approach is also used to analyze the Cassie-Wenzel transition under the influence of an EW voltage and estimate the energy barrier to transition. The results obtained show that EW is a powerful tool to alter the relative stabilities of the Cassie and Wenzel states and enable dynamic control of droplet morphology on rough surfaces. The versatility and generalized nature of the present modeling approach is highlighted by application to the prediction of the contact angle of a droplet on an electrowetted rough surface consisting of a dielectric layer of nonuniform thickness.
Micro- and nanoscale protein patterns have been produced via a new contact printing method using a nanoimprint lithography apparatus. The main novelty of the technique is the use of poly(methyl methacrylate) (PMMA) instead of the commonly used poly(dimethylsiloxane) (PDMS) stamps. This avoids printing problems due to roof collapse, which limits the usable aspect ratio in microcontact printing to 10:1. The rigidity of the PMMA allows protein patterning using stamps with very high aspect ratios, up to 300 in this case. Conformal contact between the stamp and the substrate is achieved because of the homogeneous pressure applied via the nanoimprint lithography instrument, and it has allowed us to print lines of protein approximately 150 nm wide, at a 400 nm period. This technique, therefore, provides an excellent method for the direct printing of high-density sub-micrometer scale patterns, or, alternatively, micro-/nanopatterns spaced at large distances. The controlled production of these protein patterns is a key factor in biomedical applications such as cell-surface interaction experiments and tissue engineering.
High area nickel and cobalt surfaces were assembled using modified Tobacco mosaic virus (TMV) templates. Rod-shaped TMV templates (300 x 18 nm) engineered to encode unique cysteine residues were self-assembled onto gold patterned surfaces in a vertically oriented fashion, producing a >10-fold increase in surface area. Electroless deposition of ionic metals onto surface-assembled virus templates produced uniform metal coatings up to 40 nm in thickness. Within a nickel-zinc battery system, the incorporation of virus-assembled electrode surfaces more than doubled the total electrode capacity. When combined, these findings demonstrate that surface-assembled virus templates provide a robust platform for the fabrication of oriented high surface area materials.
A Review on 3D Micro-Additive Manufacturing Technologies
- Rev Soc
- H Seitz
- S Yang
- X Zhang
- F Shi
- J Niu
Soc. Rev. 2017, 46, 366.
(16) Vaezi, M.; Seitz, H.; Yang, S. A Review on 3D Micro-Additive
Manufacturing Technologies. Int. J. Adv. Manuf. Technol. 2013, 67 (5−
8), 1721−1754.
(17) Zhang, X.; Shi, F.; Niu, J.; Jiang, Y.; Wang, Z. Superhydrophobic
Surfaces: From Structural Control to Functional Application. J. Mater.
Designing Superoleophobic Surfaces Electrowetting-Based Control of Static Droplet States on Rough Surfaces Statics and Dynamics of Electrowetting on Pillar-Arrayed Surfaces at the Nanoscale Mosaic VirusTemplated Hierarchical Ni/NiO with High Electrochemical Charge Storage Performances
- G C Rutledge
- G H Mckinley
- R E Cohen
- V Bahadur
- S V Garimella
- Y.-P Zhao
- Q Yuan
- S Chu
- K Gerasopoulos
- R Ghodssi
- M Mccarthy
- E Royston
- J Culver
Rutledge, G. C.; McKinley, G. H.; Cohen, R. E. Designing
Superoleophobic Surfaces. Science 2007, 318 (5856), 1618−1622.
(19) Bahadur, V.; Garimella, S. V. Electrowetting-Based Control of
Static Droplet States on Rough Surfaces. Langmuir 2007, 23 (9),
4918−4924.
(20) Zhao, Y.-P.; Yuan, Q. Statics and Dynamics of Electrowetting on
Pillar-Arrayed Surfaces at the Nanoscale. Nanoscale 2015, 7 (6),
2561−2567.
(21) Lafuma, A.; Quéré,QuéréQuéré, D. Superhydrophobic States. Nat. Mater.
2003, 2 (7), 457−460.
(22) Chu, S.; Gerasopoulos, K.; Ghodssi, R. Tobacco Mosaic VirusTemplated Hierarchical Ni/NiO with High Electrochemical Charge
Storage Performances. Electrochim. Acta 2016, 220, 184.
(23) Gerasopoulos, K.; McCarthy, M.; Royston, E.; N Culver, J.;
Electrowetting: From Basics to Applications Variable-Focus Liquid Lens for Miniature Cameras Electrowetting on Paper for Electronic Paper Display A Review of Digital Microfluidics as Portable Platforms for Lab-on a-Chip Applications
- C Wang
- J Culver
- R Ghodssi
- F Mugele
- J.-C Baret
- S Kuiper
- B H W Hendriks
- D Y Kim
- A J Steckl
- T N Krupenkin
- J A L Taylor
- C R Evans
- N J Shirtcliffe
- G Mchale
Wang, C.; Culver, J.; Ghodssi, R. Hierarchical Three-Dimensional
Microbattery Electrodes Combining Bottom-up Self-Assembly and
Top-down Micromachining. ACS Nano 2012, 6 (7), 6422−6432.
(26) Mugele, F.; Baret, J.-C. Electrowetting: From Basics to
Applications. J. Phys.: Condens. Matter 2005, 17 (28), R705−R774.
(27) Kuiper, S.; Hendriks, B. H. W. Variable-Focus Liquid Lens for
Miniature Cameras. Appl. Phys. Lett. 2004, 85 (7), 1128−1130.
(28) Kim, D. Y.; Steckl, A. J. Electrowetting on Paper for Electronic
Paper Display. ACS Appl. Mater. Interfaces 2010, 2 (11), 3318−3323.
(29) Samiei, E.; Tabrizian, M.; Hoorfar, M. A Review of Digital
Microfluidics as Portable Platforms for Lab-on a-Chip Applications.
Lab Chip 2016, 16, 2376−2396.
(30) Krupenkin, T. N.; Taylor, J. A.; Schneider, T. M.; Yang, S. From
Rolling Ball to Complete Wetting: The Dynamic Tuning of Liquids on
Nanostructured Surfaces. Langmuir 2004, 20 (10), 3824−3827.
(31) Herbertson, D. L.; Evans, C. R.; Shirtcliffe, N. J.; Mchale, G.;
- A Lafuma
- D Queŕe
- Superhydrophobic
- States
Lafuma, A.; Queŕe, D. Superhydrophobic States. Nat. Mater.
2003, 2 (7), 457−460.