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Artykuły w czasopismach na temat "Hydrogel/substrate interface"
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Liu, Junjie, Nan Hu, Yao Xie, Peng Wang, Jingxiang Chen i Qianhua Kan. "Polyacrylic Acid Hydrogel Coating for Underwater Adhesion: Preparation and Characterization". Gels 9, nr 8 (29.07.2023): 616. http://dx.doi.org/10.3390/gels9080616.
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Underwater adhesion involves bonding substrates in aqueous environments or wet surfaces, with applications in wound dressing, underwater repairs, and underwater soft robotics. In this study, we investigate the underwater adhesion properties of a polyacrylic acid hydrogel coated substrate. The underwater adhesion is facilitated through hydrogen bonds formed at the interface. Our experimental results, obtained through probe-pull tests, demonstrate that the underwater adhesion is rapid and remains unaffected by contact pressure and pH levels ranging from 2.5 to 7.0. However, it shows a slight increase with a larger adhesion area. Additionally, we simulate the debonding process and observe that the high-stress region originates from the outermost bonding region and propagates towards the center, spanning the thickness of the target substrate. Furthermore, we showcase the potential of using the underwater adhesive hydrogel coating to achieve in-situ underwater bonding between a flexible electronic demonstration device and a hydrogel contact lens. This work highlights the advantages of employing hydrogel coatings in underwater adhesion applications and serves as inspiration for the advancement of underwater adhesive hydrogel coatings capable of interacting with a wide range of substrates through diverse chemical and physical interactions at the interface.
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Lin, Yue-Xian, Shu-Han Li i Wei-Chen Huang. "Fabrication of Soft Tissue Scaffold-Mimicked Microelectrode Arrays Using Enzyme-Mediated Transfer Printing". Micromachines 12, nr 9 (31.08.2021): 1057. http://dx.doi.org/10.3390/mi12091057.
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Hydrogels are the ideal materials in the development of implanted bioactive neural interfaces because of the nerve tissue-mimicked physical and biological properties that can enhance neural interfacing compatibility. However, the integration of hydrogels and rigid/dehydrated electronic microstructure is challenging due to the non-reliable interfacial bonding, whereas hydrogels are not compatible with most conditions required for the micromachined fabrication process. Herein, we propose a new enzyme-mediated transfer printing process to design an adhesive biological hydrogel neural interface. The donor substrate was fabricated via photo-crosslinking of gelatin methacryloyl (GelMA) containing various conductive nanoparticles (NPs), including Ag nanowires (NWs), Pt NWs, and PEDOT:PSS, to form a stretchable conductive bioelectrode, called NP-doped GelMA. On the other hand, a receiver substrate composed of microbial transglutaminase-incorporated gelatin (mTG-Gln) enabled simultaneous temporally controlled gelation and covalent bond-enhanced adhesion to achieve one-step transfer printing of the prefabricated NP-doped GelMA features. The integrated hydrogel microelectrode arrays (MEA) were adhesive, and mechanically/structurally bio-compliant with stable conductivity. The devices were structurally stable in moisture to support the growth of neuronal cells. Despite that the introduction of AgNW and PEDOT:PSS NPs in the hydrogels needed further study to avoid cell toxicity, the PtNW-doped GelMA exhibited a comparable live cell density. This Gln-based MEA is expected to be the next-generation bioactive neural interface.
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Yang, Yueh-Hsun Kevin, Courtney R. Ogando i Gilda A. Barabino. "In Vitro Evaluation of the Influence of Substrate Mechanics on Matrix-Assisted Human Chondrocyte Transplantation". Journal of Functional Biomaterials 11, nr 1 (18.01.2020): 5. http://dx.doi.org/10.3390/jfb11010005.
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Matrix-assisted chondrocyte transplantation (MACT) is of great interest for the treatment of patients with cartilage lesions. However, the roles of the matrix properties in modulating cartilage tissue integration during MACT recovery have not been fully understood. The objective of this study was to uncover the effects of substrate mechanics on the integration of implanted chondrocyte-laden hydrogels with native cartilage tissues. To this end, agarose hydrogels with Young’s moduli ranging from 0.49 kPa (0.5%, w/v) to 23.08 kPa (10%) were prepared and incorporated into an in vitro human cartilage explant model. The hydrogel-cartilage composites were cultivated for up to 12 weeks and harvested for evaluation via scanning electron microscopy, histology, and a push-through test. Our results demonstrated that integration strength at the hydrogel-cartilage interface in the 1.0% (0.93 kPa) and 2.5% (3.30 kPa) agarose groups significantly increased over time, whereas hydrogels with higher stiffness (>8.78 kPa) led to poor integration with articular cartilage. Extensive sprouting of extracellular matrix in the interfacial regions was only observed in the 0.5% to 2.5% agarose groups. Collectively, our findings suggest that while neocartilage development and its integration with native cartilage are modulated by substrate elasticity, an optimal Young’s modulus (3.30 kPa) possessed by agarose hydrogels is identified such that superior quality of tissue integration is achieved without compromising tissue properties of implanted constructs.
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Zhao, Zhitong, Weiwei Gao i Hao Bai. "A mineral layer as an effective binder to achieve strong bonding between a hydrogel and a solid titanium substrate". Journal of Materials Chemistry B 6, nr 23 (2018): 3859–64. http://dx.doi.org/10.1039/c8tb01042k.
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Bordbar-Khiabani, Aydin, Ilijana Kovrlija, Janis Locs, Dagnija Loca i Michael Gasik. "Octacalcium Phosphate-Laden Hydrogels on 3D-Printed Titanium Biomaterials Improve Corrosion Resistance in Simulated Biological Media". International Journal of Molecular Sciences 24, nr 17 (24.08.2023): 13135. http://dx.doi.org/10.3390/ijms241713135.
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The inflammatory-associated corrosion of metallic dental and orthopedic implants causes significant complications, which may result in the implant’s failure. The corrosion resistance can be improved with coatings and surface treatments, but at the same time, it might affect the ability of metallic implants to undergo proper osteointegration. In this work, alginate hydrogels with and without octacalcium phosphate (OCP) were made on 3D-printed (patterned) titanium alloys (Ti Group 2 and Ti-Al-V Group 23) to enhance their anticorrosion properties in simulated normal, inflammatory, and severe inflammatory conditions in vitro. Alginate (Alg) and OCP-laden alginate (Alg/OCP) hydrogels were manufactured on the surface of 3D-printed Ti substrates and were characterized with wettability analysis, XRD, and FTIR. The electrochemical characterization of the samples was carried out with open circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). It was observed that the hydrophilicity of Alg/OCP coatings was higher than that of pure Alg and that OCP phase crystallinity was increased when samples were subjected to simulated biological media. The corrosion resistance of uncoated and coated samples was lower in inflammatory and severe inflammatory environments vs. normal media, but the hydrogel coatings on 3D-printed Ti layers moved the corrosion potential towards more nobler values, reducing the corrosion current density in all simulated solutions. These measurements revealed that OCP particles in the Alg hydrogel matrix noticeably increased the electrical charge transfer resistance at the substrate and coating interface more than with Alg hydrogel alone.
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González-Henríquez, Carmen M., Diego F. Veliz-Silva, Mauricio A. Sarabia-Vallejos, Adolfo del Campo-García i Juan Rodríguez-Hernández. "Micrometric Wrinkled Patterns Spontaneously Formed on Hydrogel Thin Films via Argon Plasma Exposure". Molecules 24, nr 4 (19.02.2019): 751. http://dx.doi.org/10.3390/molecules24040751.
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The generation of microstructured patterns on the surface of a specific polymeric material could radically improve their performance in a particular application. Most of the interactions with the environment occur at the material interface; therefore, increasing the exposed active surface considerably improves their range of application. In this article, a simple and reliable protocol to form spontaneous wrinkled patterns using a hydrogel layer is reported. For this purpose, we took advantage of the doctor blade technique in order to generate homogenous films over solid substrates with controlled thickness and large coverage. The hydrogel wrinkle formation involves a prepolymerization step which produces oligomers leading to a solution with increased viscosity, enough for doctor blade deposition. Subsequently, the material was exposed to vacuum and plasma to trigger wrinkled pattern formation. Finally, a UV-polymerization treatment was applied to fix the undulations on top. Interestingly, the experimental parameters allowed us to finely tune the wrinkle characteristics (period, amplitude, and orientation). For this study, two main aspects were explored. The first one is related to the role of the substrate functionalization on the wrinkle formation. The second study correlates the deswelling time and its relationship with the dimensions and distribution of the wrinkle pattern. In the first batch, four different 3-(trimethoxysilyl)propyl methacrylate (TSM) concentrations were used to functionalize the substrate in order to enhance the adhesion between hydrogel film and the substrate. The wrinkles formed were characterized in terms of wrinkle amplitude, wavelength, pattern roughness, and surface Young modulus, by using AFM in imaging and force spectroscopy modes. Moreover, the chemical composition of the hydrogel film cross-section and the effect of the plasma treatment were analyzed with confocal Raman spectroscopy. These results demonstrated that an oxidized layer was formed on top of the hydrogel films due to the exposure to an argon plasma.
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Wischke, Christian, Marlin Kersting, Alexander Welle, Liudmila Lysyakova, Steffen Braune, Karl Kratz, Friedrich Jung, Matthias Franzreb i Andreas Lendlein. "Thin hydrogel coatings formation catalyzed by immobilized enzyme horseradish peroxidase". MRS Advances 5, nr 14-15 (2020): 773–83. http://dx.doi.org/10.1557/adv.2020.218.
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ABSTRACTEnzymes can be a renewable source of catalytic agents and thus be interesting for sustainable approaches to create and modify functional materials. Here, thin hydrogel layers were prepared as thin coatings on hard substrates by immobilized horseradish peroxidase. Hydrophilic 4-arm star shaped telechelics from oligo(ethylene glycol) bearing on average 55% end groups derived from aromatic amino acids served as monomers and enzymatic substrates. Shifts of the contact angle from 84° to 62° for the wetting process and of zeta potential towards the neutral range illustrated an alteration of physicochemical properties of the model surfaces by a hydrophilic shielding. Time-of-flight secondary ion mass spectrometry (ToF-SIMS), quartz crystal microbalance and atomic force microscopy (AFM) experiments enabled the qualitative and quantitative proof of hydrogel deposition at the interface with thicknesses in the medium nanometer size range. Conceptually, as the immobilized enzyme becomes entrapped in the hydrogel and the crosslinking mechanism bases on a radical reaction after enzymatic activation of the monomers with a limited diffusivity and lifetime, the formed network material can be assumed to be inhomogeneous on the molecular level. On the macroscale, however, relative homogeneity of the coating was observed via ToF-SIMS and AFM mapping. As an exemplary functional evaluation in view of bioanalytical applications, the thrombogenicity of the coating was studied in static tests with human blood from several donors. In the future, this “coating-from” approach may be explored for cell culture substrate coatings, for protein/biofilm repellence in technical applications, or in bioanalytical devices.
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Lee, Hyelim, Jaepyo Jang, Jaebeom Lee, Mikyung Shin, Jung Seung Lee i Donghee Son. "Stretchable Gold Nanomembrane Electrode with Ionic Hydrogel Skin-Adhesive Properties". Polymers 15, nr 18 (21.09.2023): 3852. http://dx.doi.org/10.3390/polym15183852.
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Skin has a dynamic surface and offers essential information through biological signals originating from internal organs, blood vessels, and muscles. Soft and stretchable bioelectronics can be used in wearable machines for long-term stability and to continuously obtain distinct bio-signals in conjunction with repeated expansion and contraction with physical activities. While monitoring bio-signals, the electrode and skin must be firmly attached for high signal quality. Furthermore, the signal-to-noise ratio (SNR) should be high enough, and accordingly, the ionic conductivity of an adhesive hydrogel needs to be improved. Here, we used a chitosan-alginate-chitosan (CAC) triple hydrogel layer as an interface between the electrodes and the skin to enhance ionic conductivity and skin adhesiveness and to minimize the mechanical mismatch. For development, thermoplastic elastomer Styrene-Ethylene-Butylene-Styrene (SEBS) dissolved in toluene was used as a substrate, and gold nanomembranes were thermally evaporated on SEBS. Subsequently, CAC triple layers were drop-casted onto the gold surface one by one and dried successively. Lastly, to demonstrate the performance of our electrodes, a human electrocardiogram signal was monitored. The electrodes coupled with our CAC triple hydrogel layer showed high SNR with clear PQRST peaks.
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Sun, Lingyu, Feika Bian, Yu Wang, Yuetong Wang, Xiaoxuan Zhang i Yuanjin Zhao. "Bioinspired programmable wettability arrays for droplets manipulation". Proceedings of the National Academy of Sciences 117, nr 9 (18.02.2020): 4527–32. http://dx.doi.org/10.1073/pnas.1921281117.
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The manipulation of liquid droplets demonstrates great importance in various areas from laboratory research to our daily life. Here, inspired by the unique microstructure of plant stomata, we present a surface with programmable wettability arrays for droplets manipulation. The substrate film of this surface is constructed by using a coaxial capillary microfluidics to emulsify and pack graphene oxide (GO) hybridN-isopropylacrylamide (NIPAM) hydrogel solution into silica nanoparticles-dispersed ethoxylated trimethylolpropane triacrylate (ETPTA) phase. Because of the distribution of the silica nanoparticles on the ETPTA interface, the outer surface of the film could achieve favorable hydrophobic property under selective fluorosilane decoration. Owing to the outstanding photothermal energy transformation property of the GO, the encapsulated hydrophilic hydrogel arrays could shrink back into the holes to expose their hydrophobic surface with near-infrared (NIR) irradiation; this imparts the composite film with remotely switchable surface droplet adhesion status. Based on this phenomenon, we have demonstrated controllable droplet sliding on programmable wettability pathways, together with effective droplet transfer for printing with mask integration, which remains difficult to realize by existing techniques.
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Guo, Jiaxin, Jun Luo i Zhongmin Xiao. "On the opening profile and near tip fields of an interface crack between a polymeric hydrogel and a rigid substrate". Engineering Fracture Mechanics 153 (marzec 2016): 91–102. http://dx.doi.org/10.1016/j.engfracmech.2015.12.029.
Pełny tekst źródłaKsiążki na temat "Hydrogel/substrate interface"
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Lin, Nian, i Sebastian Stepanow. Designing low-dimensional nanostructures at surfaces by supramolecular chemistry. Redaktorzy A. V. Narlikar i Y. Y. Fu. Oxford University Press, 2017. http://dx.doi.org/10.1093/oxfordhb/9780199533046.013.10.
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This article describes the use of supramolecular chemistry to design low-dimensional nanostructures at surfaces. In particular, it discusses the design strategies of two types of low-dimensional supramolecular nanostructures: structures stabilized by hydrogen bonds and structures stabilized by metal-ligand co-ordination interactions. After providing an overview of hydrogen-bond systems such as 0D discrete clusters, 1D chains, and 2D open networks and close-packed arrays, the article considers metal-co-ordination systems. It also presents experimental results showing that both hydrogen bonds and metal co-ordination offer protocols to achieve unique nanostructured systems on 2D surfaces or interfaces. Noting that the conventional 3D supramolecular self-assembly has generated a vast number of nanostructures revealing high complexity and functionality, the article suggests that 2D approaches can be applied to substrates with different symmetries as well as physical and chemical properties.
Części książek na temat "Hydrogel/substrate interface"
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Washio, Jumpei, Yoko Sakuma, Yuko Shimada i Nobuhiro Takahashi. "Hydrogen-sulfide production from various substrates by oral Veillonella and effects of lactate on the production". W Interface Oral Health Science 2009, 250–51. Tokyo: Springer Japan, 2010. http://dx.doi.org/10.1007/978-4-431-99644-6_66.
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Sligar, Stephen G., i Clifford R. Robinson. "Osmotic and Hydrostatic Pressure as Tools to Study Molecular Recognition". W High Pressure Effects in Molecular Biophysics and Enzymology. Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195097221.003.0026.
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The question of molecular recognition is a central paradigm of molecular biology, playing central roles in most, if not all, cellular processes. Failed recognition events have been implicated in numerous disease states, ranging from flawed control of gene regulation and cellular proliferation to defects in specific metabolic activities. Historically, questions of molecular recognition have been approached through organic synthesis and through actual structural studies of biomolecular complexes. Fundamental insight into the mechanisms of molecular recognition can be realized through the use of broad interdisciplinary tools and techniques. In particular, the use of recombinant DNA technology in concert with hydrostatic and osmotic pressure methodologies have proven to be ideal for understanding the fundamental mechanisms of recognition. In our presentation, we will focus on recent results from our laboratory that examine three major classes of recognition events in biological systems: 1. Protein-protein recognition: here we seek to define the role of specific surface interactions; electrostatic, hydrogen bonding, and hydrophobic free energies provided through surface complimentarity, which define the specificity and affinity in the formation of complexes between the metalloproteins involved in electron transfer events in cytochrome P-450-dependent oxygenase catalysis and in the assembly of tetrameric hemoglobin. 2. Protein—small molecule recognition: here we seek to ascertain how the same fundamental forces of electrostatics, hydrogen bonding, and the hand-glove fit of a substrate into the active site of an enzyme can give rise to the observed high degree of control of regio- and stereo-specificity in catalysis and in the interfadal interactions of proteins at electrode interfaces. 3. Protein nucleic acid recognition: here again the same fundamental forces control recognition processes, but in this case we will focus on our exciting, recent discovery of a role for solvent water in mediating recognition between protein and nucleic acid components. Representative systems in the binding/ catalytic class of restriction endonucleases and recombinases will be discussed. In all cases, the use of pressure as a variable has provided unique understanding for the molecular details of these processes. Pressure, both hydrostatic and osmotic, has proven to be an enabling experimental technique in understanding the mechanistic origins of molecular recognition events.
Streszczenia konferencji na temat "Hydrogel/substrate interface"
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Sarles, Stephen A., i Donald J. Leo. "Encapsulated Interface Bilayers for Durable Biomolecular Materials". W ASME 2010 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2010. http://dx.doi.org/10.1115/smasis2010-3752.
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This paper introduces the concept of hydrogel encapsulated interface bilayers as a novel approach for creating durable encapsulated biomolecular materials. The regulated attachment method (RAM) is used to form encapsulated interface bilayers from lipid-encased aqueous volumes contained in a deformable supporting substrate. Physically-encapsulated interface bilayers exhibit increased durability and portability over droplet interface bilayedrs and RAM enables the in situ bilayer formation without the need to dispense and arrange individual droplets. The results presented in this paper demonstrate that poly(ethylene glycol) dimethacrylate monomers (PEG-DMA, Mw = 1000), a photopolymerizable hydrogel monomer, and Irgacure 2959 photoinitiator can be incorporated into the aqueous phase in order to form hydrogel encapsulated interface bilayers. Following bilayer formation, exposure to an ultraviolet (UV) light initiates photopolymerization of the polymer on both sides of the bilayer, creating interface bilayers between solid aqueous phases. Electrical recordings of bilayer formation in the liquid state confirm that interface bilayers formed from photopolymerizable aqueous solutions have both high electrical resistances > 1GΩ necessary for observing transmembrane protein gating and survive the UV curing procedure required to polymerize the hydrogel. Photopolymerization for 60 seconds using a 1W hand held UV spot cure light produced water-swollen solids on both sides of the membrane. Hydrogel encapsulated interface bilayers last for hours to days and retain the fluidity necessary for delivering alamethicin proteins to the interface.
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Sarles, Stephen A., Kevin L. Garrison, Taylor T. Young i Donald J. Leo. "Formation and Encapsulation of Biomolecular Arrays for Developing Arrays of Membrane-Based Artificial Hair Cell Sensors". W ASME 2011 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2011. http://dx.doi.org/10.1115/smasis2011-5095.
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Recent research in our group has shown that artificial cell membranes formed at the base of a hair-like structure can be used to sense air flow in a manner similar to the mechanotransduction processes found in mammalian hair cells. Our previous work demonstrated that a single artificial hair cell can be formed in an open substrate. However, that study also motivated the need to develop fully-encapsulated devices that feature arrays of hair-cells. Since the transduction element in this concept is an artificial cell membrane, or lipid bilayer, this work investigates two parallel substrate designs for providing encapsulation and a method for forming arrays of bilayers. In one effort, a flexible substrate with internal compartments for hosting the biomolecules and mating cap are constructed and experimentally characterized. The regulated attachment method (RAM) is used to form interface bilayers within the sealed device. Capacitance measurements of the sealed interface bilayer show that the sealing cap slightly compresses the bottom insert and reduces the size of the enclosed bilayer. Single channel measurements of alamethicin peptides further verify that the sealed device, which is also leak-proof under water, can be used to detect the insertion and gating activity of transmembrane proteins in the membrane. The second effort pursued herein is the fabrication and initial testing of a method to form arrays of interface bilayers by using anchored hydrogel pads that support curved aqueous lenses in oil. In this fashion, the configuration of the array does not require manipulating droplets, but instead depends on the arrangement of the built-in gels used to support the aqueous lenses. As with RAM, mechanical force is used to promote contact of adjacent aqueous lenses held in the flexible substrate. Initial tests show that gel-supported lenses can be used for forming multiple lipid bilayers within the device and that these interfaces can be interrogated individually or collectively using an electrode switching circuit.
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Tamaddoni, Nima, i Andy Sarles. "Fabrication and Characterization of a Membrane Based Hair Cell Sensor That Features Soft Hydrogel Materials". W ASME 2012 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/smasis2012-8067.
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One of the most common sensory structures in nature is the hair cell. Examples of hair cells include the inner and outer hair cells in the inner ears of vertebrates, external sensory hairs on the legs of spiders, and neuromasts found along the lateral lines of fish. Recent work by Sarles and Leo demonstrated that self-assembly methods could be used to construct a membrane-based hair cell that responds to a physical disturbance of the hair. An artificial cell membrane (or lipid bilayer) formed at the interface of two lipid-encased hydrogel volumes, serves as the transduction element in the device. In this study, a revised sensor embodiment is presented in which the hair is fixed at its base by the encapsulating polymeric substrate. In addition, a highly elastic, photo-polymerizable aqueous gel (PEGDA, 6000g/mole) is used to further increase the resiliency of the hair and to provide a compliant cushion for the bilayer. These changes yield a considerably more durable hair cell sensor. We perform a series of experimental tests to characterize the transduction element (i.e. the bilayer) and the sensing current produced by free vibration of the hair, and we study the directional sensitivity of this hair cell embodiment by perturbing the hair in three directions. These tests demonstrate that the magnitude of the sensing current (30–300pA) is significantly affected by direction of perturbation, where the largest signals result from motion of the hair in a direction perpendicular to the plane of the bilayer.
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Edgerton, Alex, Joseph Najem i Donald Leo. "A Hydrogel-Based Droplet Interface Lipid Bilayer Network". W ASME 2014 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/smasis2014-7580.
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In this work, we present a process for the fabrication of meso-scale hydrogel-based lipid bilayer arrays. The hydrogels support lipid monolayers at an oil-water interface, and when brought together, form stable bilayers. The substrates are formed using 3D printed molds and include built-in, customizable circuits patterned with silver paint. The system can be adapted to varying network sizes and circuit designs, and new arrays are fabricated quickly and inexpensively using common laboratory techniques. An enclosed 3×3 array with 3 mm spacing between neighboring hydrogels and electrodes to individually examine each bilayer has been created using this method. An alternative test setup was also developed to better observe the formation of bilayers in a small array. Using this setup, two bilayers were formed simultaneously, demonstrating the feasibility of this type of system and providing valuable information for expanding and improving the enclosed network. Many of the design concepts presented here can be adapted for use at smaller scales using microfabrication techniques.
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Yoshii, I., K. Hama i K. Hashimoto. "Role of Hydrogen at Poly-Si/SiO2 Interface in Trap Generation by Substrate Hot-Electron Injection". W 30th International Reliability Physics Symposium. IEEE, 1992. http://dx.doi.org/10.1109/irps.1992.363288.
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Yoshii, I., K. Hama i K. Hashimoto. "Role of hydrogen at poly-Si/SiO/sub 2/ interface in trap generation by substrate hot-electron injection". W 30th Annual Proceedings Reliability Physics 1992. IEEE, 1992. http://dx.doi.org/10.1109/relphy.1992.187638.
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Lin, Shih-Chang, Fangang Tseng i Ching-Chang Chieng. "Numerical Simulation of Protein Stamping Process Driven by Capillary Force". W ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-33070.
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“Microstamping” is one of patterning techniques [1] developed to deliver thousands of samples in parallel onto a surface for use in biosensors and medical diagnostics and the inexpensive production of micropatterned arrays of active proteins is of interest. Successful print of these protein island arrays includes conformal contact between an inked patterned stamp and the surface of a substrate and the full control over the amount and distribution of protein solution transferred from the impregnated stamps. In most common design, stamper is made of a solid material and proper inking method is required. Martin et al [2] have created a microstamper constructed by forming the hydrogel in sequence within the narrow ends of machine-pulled capillary tubes. This paper studies the protein-filling (inking)/stamping/printing process by numerical computations for a proposed Array-Stamper Chip with embedded microchannels. (Fig. 1) The array chip consists of thousands of microchannels with their own stampers to deliver thousands of fixed size/shape liquid samples to a bottom chip by capillary force simultaneously. The transfer process and physics are analyzed by solving first principle equations, i.e. conservation laws of mass, momentum. Due to the symmetry design of the array chip, the analysis is performed for a representative stamp only (Fig. 1b). Stable and robust numerical approaches as volume-of-Fluid (VOF) method [3] for two phase homogenous flow model and the interface tracking technique in cooperation with Continuum Surface tension Force (CSF) Model [4] are employed to determine the shape of liquid/gas interface as well as the fluid flowing pattern. Figure 2 shows the entire protein transfer during stamping/printing process, the Stamper Chip is moved toward/touch/away bio reaction chip starting at a distance of 50 μm away. The process consists of (a) The liquid fluid forms a meniscus and tends to reach out at the tip of the microchannel from the Stamping Chip (Fig. 2a), (b) The droplet meniscus is formed and the Stamper Chip starts to be moved toward the bottom chip (Fig. 2b), (c) The Stamper Chip is touched down and then is pulled up from the Bio-Reaction Chip, the liquid flows horizontally via the horizontal microchannels (Fig. 2c) and reaches the bottom chip, (d) part of the liquid is pushed upward and formed a small waist (Fig. 2d), (e) The Stamper Chip is moved further upwards with liquid slug of narrower waist (Fig. 2e), and (f) Stamper Chip is back to the original position with part of liquid broken at some point and left on the Bio-reaction Chip successfully. The controlling of the spot size left on bio-chip can be manipulated by physical properties of the filling protein, the inner/outer diameter of the microchannel, moving speed of the Stamper Chip, and the hydrophilic nature of the outer edge surface of the stamper. Two sets of physical properties are employed for computations (1) protein of low concentration with physical properties as water (2) 2mg/ml BSA concentration according to Fig. 3. Degree of hydrophilic nature with different liquid/gas/solid contact angle on stamper edge surface AB and the stamping speed do play significant role on the printing spot formation and size as shown in Table 1. Figure 4 shows that the size of printing size decreases with outer diameter of the microchannel. The detailed flowing process illustrate that the formations of the printing spot are resulted from forces interactions between the capillary flow formation process and stamper moving speed. In summary, numerical simulations not only give the suggestions for the array-stamper design with precise control of printing spot but also provide the physics and detailed information of the spot formation.
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Porterfield, Malcolm, i Diana Borca-Tasciuc. "Molecular Dynamics Simulation of Ultra-Fast Phase Transition in Water Nanofilms". W ASME 2020 Heat Transfer Summer Conference collocated with the ASME 2020 Fluids Engineering Division Summer Meeting and the ASME 2020 18th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/ht2020-9073.
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Abstract Molecular dynamics simulations are used to explore explosive boiling of thin water films on a gold substrate. In particular, water films of 2.5, 1.6 and 0.7 nanometer thickness were examined. Three different surface wettabilities with contact angles of 11, 47 and 110 degrees were simulated along with substrate temperatures of 400K, 600K, 800K and 1000K. The 11 degree contact angle was obtained using a Morse interaction potential between the water film and the gold substrate while the 47 and 110 degree contact angles were obtained via a Lennard-Jones potential. Evaporation was the first mode of phase change observed in all cases and explosive boiling did not occur until the substrate reached a temperature of 800K. When explosive boiling was present for all three contact angles, it was consistently shown to occur first for the surface with a 47 degree contact angle, contrary to the expectation that it would occur first on the substrate with an 11 degree contact angle. These results suggest that explosive boiling onset is strongly dependent on the particularities of the interaction potential. For instance, the Morse potential used to model the surface described by an 11 degree contact angle, is a softer potential as compared with Lennard-Jones, but has more interaction sites per molecule — two hydrogen atoms and one oxygen atom vs one oxygen atom. Thus, although the water film reaches a higher temperature with the Morse potential, explosive boiling onset is delayed as more interaction sites have to be disrupted. These results suggest that both the interaction strength and the number of atoms interacting at the interface must be considered when investigating trends of explosive boiling with surface wettability.
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Underwood, John H., Robert H. Carter, Edward Troiano i Anthony P. Parker. "Mechanics Design Models for Advanced Pressure Vessels: Autofrettage With Higher Strength Steel; Steel Liner - Composite Jacket Configurations; Alternative Thermal Barrier Coatings". W ASME 2010 Pressure Vessels and Piping Division/K-PVP Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/pvp2010-25006.
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Solid mechanics models are described of mechanical and thermal stresses in 1000–1400 MPa yield strength, autofrettaged, steel pressure vessels. Modeling results describe idealized advanced vessel configurations with improved resistance to mechanical damage from internal pressure and thermal damage from transient internal heating. [i] Calculations of autofrettage hoop residual stresses are based on the classic Hill elastic-plastic results for thick-wall tubes, with modifications to account for the Bauschinger-reduced compressive strength of the tube steel near the bore. [ii] Stresses in metal liner - composite jacket tubes are calculated using the Parker layered-tube model, which gives applied and residual elastic stresses for two-layer tubes with specified properties and interference between layers. [iii] Transient thermal stresses in bore barrier coatings are calculated using the finite difference methods of Witherell, describing one-dimensional, convection-conduction heat flow, focusing on near-bore temperatures using time-dependent combustion gas temperatures and convection coefficient data from interior ballistic codes. Temperatures are obtained for various thicknesses of metallic and ceramic coatings on steel substrate, using temperature-dependent conductivity and diffusivity data for the coatings and substrate. In-situ verification of calculated temperature profiles is done by comparing with metallographic observation of depths of the steel phase transformation and the known characteristic transformation temperature. When the transient shear stress near the interface exceeds the reduced elevated-temperature strength of the interface, coating segments are modeled to be lost by shear failure, which in turn would lead to rapid hot-gas erosion of the steel substrate. Results of the model calculations are used to identify potential improvements in advanced pressure vessels, using idealized configurations as examples. [i] Autofrettage of higher strength steel vessels shows significant increase in both yield pressure and fatigue life, but poorer resistance to both hydrogen cracking and yield-before-break final failure, compared to traditional lower strength designs of equivalent weight. [ii] Vessels with steel liner and either high strength carbon/epoxy or unidirectional Al2O3/Al jacket and high liner-jacket interference show similar fatigue life to that of all-steel designs of equivalent weight. However radial compressive crushing of composite materials in transverse orientation limits composite jacketed vessels to lower applied pressure than all-steel designs. [iii] Metal thermal barrier coatings generally suffer from compressive yielding at elevated temperatures near the bore, leading to tensile residual stress, cracking, and erosion failure. The higher hot strength of a Si3N4 ceramic provides significant improvement in yielding and cracking resistance and thus erosion resistance, compared with metal coatings subjected to the same thermal conditions.
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Han, Jeahyeong, Daniel Joe, Rich I. Masel i Mark A. Shannon. "AFM Verification of CFn Surface Treatment Effect and Its Correlation to Stiction Reduction in Microvalves". W ASME 2008 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/detc2008-49842.
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The purpose of this paper is to show AFM verification of adhesion reduction between valve seat/membrane interfaces by surface coatings from a C4F8/Ar plasma in an ICP DRIE. Our check valves utilize a polyimide (PI, Polyimide 5878G, HD Microsystem) membrane on a Si/SiO2 valve seat. These valves form a seal between a polished Si/SiO2 substrate and a smooth polymer membrane. PI absorbs moisture up to 3.4% wt per volume, and the SiO2 surface also has an affinity to water. The smooth PI membrane touches the SiO2 surface, giving rise to relatively strong van der Waals adhesion. Under humid conditions, hydrogen-bonded stiction can occur at the interface between the PI and SiO2 during the drying step. The C4F8/Ar plasma coating is utilized for the actual device in order to lower the interface adhesion between Si/SiO2 and PI film. The opening pressures of devices with/without CFn film are measured. The valves without non-stiction coating did not open with inlet pressures up to 210 KPa. With a non-stiction coating, the valves showed an initial opening pressure of 32.5±11 KPa. AFM pull-off measurements using nano-sized tips and micro sized tips are performed to quantify the effect of the CFn film-treated surface between solid-solid surface pairs. The original surface pair for the microvalve membrane and seat surface is Si/SiO2 and PI film. The CFn film treatment is possible on one or both sides of the surfaces. AFM pull-off testing has been performed to measure the work of adhesion between four possible surface combinations, including SiO2/PI, CFn/PI, CFn/SiO2, and CFn/CFn. The work of adhesion of the surface pairs is obtained using the Johnson-Kendall-Roberts (JKR) theory. Two types of AFM probes were used, a regular nano-sized AFM probe and a one micron particle AFM probe. The work of adhesions obtained for the pairs above are 257.6±37.1, 59.4±29.2, 89.6±18.2, and 41.0±8.2 [mJ/m2] from regular tips, and 159.48±4.0, 41.9±2.0, 65.7±12.2, and 37.4±3.7 [mJ/m2] from the particle tips. The CFn film treatment reduced the adhesion energy up to 84% for the regular AFM tip results, and up to 76.7% from the particle AFM tip results. The static contact angle of CFn film with respect to de-ionized water is 116.4 ± 0.9°. The surface coatings from a C4F8/Ar plasma in an ICP DRIE can reduce the contact adhesion forces and capillary forces during the fabrication process preventing stiction.