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Liu, Junjie, Nan Hu, Yao Xie, Peng Wang, Jingxiang Chen, and Qianhua Kan. "Polyacrylic Acid Hydrogel Coating for Underwater Adhesion: Preparation and Characterization." Gels 9, no. 8 (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, and Wei-Chen Huang. "Fabrication of Soft Tissue Scaffold-Mimicked Microelectrode Arrays Using Enzyme-Mediated Transfer Printing." Micromachines 12, no. 9 (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, and Gilda A. Barabino. "In Vitro Evaluation of the Influence of Substrate Mechanics on Matrix-Assisted Human Chondrocyte Transplantation." Journal of Functional Biomaterials 11, no. 1 (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, and 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, no. 23 (2018): 3859–64. http://dx.doi.org/10.1039/c8tb01042k.
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Bordbar-Khiabani, Aydin, Ilijana Kovrlija, Janis Locs, Dagnija Loca, and Michael Gasik. "Octacalcium Phosphate-Laden Hydrogels on 3D-Printed Titanium Biomaterials Improve Corrosion Resistance in Simulated Biological Media." International Journal of Molecular Sciences 24, no. 17 (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, and Juan Rodríguez-Hernández. "Micrometric Wrinkled Patterns Spontaneously Formed on Hydrogel Thin Films via Argon Plasma Exposure." Molecules 24, no. 4 (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, et al. "Thin hydrogel coatings formation catalyzed by immobilized enzyme horseradish peroxidase." MRS Advances 5, no. 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, and Donghee Son. "Stretchable Gold Nanomembrane Electrode with Ionic Hydrogel Skin-Adhesive Properties." Polymers 15, no. 18 (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, and Yuanjin Zhao. "Bioinspired programmable wettability arrays for droplets manipulation." Proceedings of the National Academy of Sciences 117, no. 9 (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, and 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 (March 2016): 91–102. http://dx.doi.org/10.1016/j.engfracmech.2015.12.029.
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Cristallini, Caterina, Serena Danti, Bahareh Azimi, et al. "Multifunctional Coatings for Robotic Implanted Device." International Journal of Molecular Sciences 20, no. 20 (2019): 5126. http://dx.doi.org/10.3390/ijms20205126.
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The objective of this study was the preparation and physico-chemical, mechanical, biological, and functional characterization of a multifunctional coating for an innovative, fully implantable device. The multifunctional coating was designed to have three fundamental properties: adhesion to device, close mechanical resemblance to human soft tissues, and control of the inflammatory response and tissue repair process. This aim was fulfilled by preparing a multilayered coating based on three components: a hydrophilic primer to allow device adhesion, a poly(vinyl alcohol) hydrogel layer to provide good mechanical compliance with the human tissue, and a layer of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) fibers. The use of biopolymer fibers offered the potential for a long-term interface able to modulate the release of an anti-inflammatory drug (dexamethasone), thus contrasting acute and chronic inflammation response following device implantation. Two copolymers, poly(vinyl acetate-acrylic acid) and poly(vinyl alcohol-acrylic acid), were synthetized and characterized using thermal analysis (DSC, TGA), Fourier transform infrared spectroscopy (FT-IR chemical imaging), in vitro cell viability, and an adhesion test. The resulting hydrogels were biocompatible, biostable, mechanically compatible with soft tissues, and able to incorporate and release the drug. Finally, the multifunctional coating showed a good adhesion to titanium substrate, no in vitro cytotoxicity, and a prolonged and controlled drug release.
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Gevrek, Tugce Nihal, Aysun Degirmenci, Rana Sanyal, and Amitav Sanyal. "Multifunctional and Transformable ‘Clickable’ Hydrogel Coatings on Titanium Surfaces: From Protein Immobilization to Cellular Attachment." Polymers 12, no. 6 (2020): 1211. http://dx.doi.org/10.3390/polym12061211.
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Multifunctionalizable hydrogel coatings on titanium interfaces are useful in a wide range of biomedical applications utilizing titanium-based materials. In this study, furan-protected maleimide groups containing multi-clickable biocompatible hydrogel layers are fabricated on a titanium surface. Upon thermal treatment, the masked maleimide groups within the hydrogel are converted to thiol-reactive maleimide groups. The thiol-reactive maleimide group allows facile functionalization of these hydrogels through the thiol-maleimide nucleophilic addition and Diels–Alder cycloaddition reactions, under mild conditions. Additionally, the strained alkene unit in the furan-protected maleimide moiety undergoes radical thiol-ene reaction, as well as the inverse-electron-demand Diels–Alder reaction with tetrazine containing molecules. Taking advantage of photo-initiated thiol-ene ‘click’ reactions, we demonstrate spatially controlled immobilization of the fluorescent dye thiol-containing boron dipyrromethene (BODIPY-SH). Lastly, we establish that the extent of functionalization on hydrogels can be controlled by attachment of biotin-benzyl-tetrazine, followed by immobilization of TRITC-labelled ExtrAvidin. Being versatile and practical, we believe that the described multifunctional and transformable ‘clickable’ hydrogels on titanium-based substrates described here can find applications in areas involving modification of the interface with bioactive entities.
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Matsumae, Takashi, Hitoshi Umezawa, Yuichi Kurashima, and Hideki Takagi. "(Invited, Digital Presentation) Low-Temperature Direct Bonding of Wide-Bandgap Semiconductor Substrates." ECS Meeting Abstracts MA2023-01, no. 32 (2023): 1830. http://dx.doi.org/10.1149/ma2023-01321830mtgabs.
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Low-temperature direct bonding technique of semiconductor substrates has been developed to integrate dissimilar materials (e.g. Si, Ge, III-V) regardless of lattice and thermal expansion mismatches. Among the direct bonding techniques, a hydrophilic bonding method, which initiates a dehydration reaction between OH-terminated substrates, is commonly used because wafer-scale bonding can be fabricated under atmospheric conditions. Recently, our research group achieved direct bonding of wide-gap materials, including SiC, GaN, β-Ga2O3, and diamond substrates, by using this bonding method. The hydrophilic bonding of Si wafers has been practically applied for the fabrication of silicon-on-insulator substrates. In the bonding process, the Si substrates are typically irradiated with reactive ion etching using oxygen plasma, which efficiently generates OH groups on the surface. By contacting the substrates under atmospheric conditions, the activated surfaces can adhere to each other by hydrogen bonds across the OH groups. The annealing at ~200 °C causes the dehydration reaction and forms atomic bonds between the substrates, as shown in the following equation. Si-OH + HO-Si → Si-O-Si +H2O The bonding process generates a sub-10-nm-thick SiOx layer at the bonding interface, which limits thermal and electrical conductance between the bonding substrates. Our research group demonstrated that the diamond substrates can be bonded with other semiconductor substrates (e.g. Si, InP, β-Ga2O3) by the hydrophilic bonding method. The pre-bonding treatment using oxygen plasma is not suitable for the diamond surface because it is easily etched by the strong oxidizing treatment. Meanwhile, the mild oxidizing treatment using H2SO4/H2O2 (i.e. piranha solution) and NH3/H2O2 (i.e. SC1) mixtures enables OH termination of the diamond substrate without a significant increase in the surface roughness. Figure A shows the photograph of the diamond substrate bonded on the Si substrate. At the Si/diamond and InP/diamond bonding interfaces, ~3-nm-thick SiOx and InPOx layers were observed by an electron microscope, respectively, as displayed in Figure B. These oxide layers were formed by the oxidizing treatment at the pre-bonding step. However, when β-Ga2O3 and diamond substrates were bonded, such an oxide intermediate layer was not observed at the bonding interface. This is because diamond never develops the oxide layer and β-Ga2O3 is an oxide material. As shown in Figure C, we achieved the direct bonding of monocrystalline β-Ga2O3 and diamond substrates with an amorphous intermediate layer thinner than 1 nm. As the intermediate layer was atomically thin, efficient electrical and thermal conductance across β-Ga2O3/diamond substrates was possible, as plotted in Figure D. Qiushi Kang et al. demonstrated that the hydrophilic bonding of the SiC substrate is possible by using oxygen plasma. This treatment develops the ~4-nm-thick SiOx layer on the SiC substrate, which possibly became a thermal and electrical barrier at the bonding interface. However, our research group revealed that the SiC substrate dipped into HF acid can form direct bonding with an atomically thin intermediate layer. It is known that the SiC surface is OH terminated after the removal of the native oxide layer by HF acid, unlike the Si substrate. We revealed that the HF-dipped SiC substrate can form direct bonding with the O2-plasma-activated β-Ga2O3 substrate through an intermediate layer as thin as 1 nm. as displayed in Figure E. About the GaN substrate, we have demonstrated that hydrophilic bonding with the Si substrate is possible using oxygen and nitrogen plasma activations. In addition, the GaN substrate dipped into H2SO4/H2O2 and NH3/H2O2 mixtures can also form direct bonding. The thickness of the GaOx layer at the GaN/Si bonding interface was approximately 1 nm. We believe the low-temperature direct bonding technique will contribute to future wide-bandgap semiconductor devices because it is possible to achieve efficient electrical and thermal conduction across dissimilar materials. Figure 1
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Lee, Jae Kyoo, Hyun Soo Han, Settasit Chaikasetsin, et al. "Condensing water vapor to droplets generates hydrogen peroxide." Proceedings of the National Academy of Sciences 117, no. 49 (2020): 30934–41. http://dx.doi.org/10.1073/pnas.2020158117.
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It was previously shown [J. K. Leeet al.,Proc. Natl. Acad. Sci. U.S.A., 116, 19294–19298 (2019)] that hydrogen peroxide (H2O2) is spontaneously produced in micrometer-sized water droplets (microdroplets), which are generated by atomizing bulk water using nebulization without the application of an external electric field. Here we report that H2O2is spontaneously produced in water microdroplets formed by dropwise condensation of water vapor on low-temperature substrates. Because peroxide formation is induced by a strong electric field formed at the water–air interface of microdroplets, no catalysts or external electrical bias, as well as precursor chemicals, are necessary. Time-course observations of the H2O2production in condensate microdroplets showed that H2O2was generated from microdroplets with sizes typically less than ∼10 µm. The spontaneous production of H2O2was commonly observed on various different substrates, including silicon, plastic, glass, and metal. Studies with substrates with different surface conditions showed that the nucleation and the growth processes of condensate water microdroplets govern H2O2generation. We also found that the H2O2production yield strongly depends on environmental conditions, including relative humidity and substrate temperature. These results show that the production of H2O2occurs in water microdroplets formed by not only atomizing bulk water but also condensing water vapor, suggesting that spontaneous water oxidation to form H2O2from water microdroplets is a general phenomenon. These findings provide innovative opportunities for green chemistry at heterogeneous interfaces, self-cleaning of surfaces, and safe and effective disinfection. They also may have important implications for prebiotic chemistry.
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Kurimoto, T., Yuichiro Kuroki, Kanji Yasui, Masasuke Takata, and Tadashi Akahane. "Characteristics of SiC Heteroepitaxial Growth on Si by Hot-Mesh Chemical Vapor Deposition." Advanced Materials Research 11-12 (February 2006): 265–68. http://dx.doi.org/10.4028/www.scientific.net/amr.11-12.265.
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The heteroepitaxial growth of 3C-SiC films on Si(100) substrates by the hot-mesh chemical vapor deposition (HM-CVD) method using monomethylsilane as a source gas was investigated. From the results of X-ray diffraction spectra, 3C-SiC crystal was epitaxially grown on Si substrates at substrate temperatures above 750°C. The SiC/Si interface was observed by cross-sectional scanning electron microscopy, and was confirmed to be void-free and smooth. The density of hydrogen radicals supplied to the substrate surface during the growth was also estimated measuring the optical absorbance change of tungsten phosphate glass plates. From the dependence of the growth rate on substrate temperature, the mechanism of SiC film growth by HM-CVD was considered.
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Chen, Jiayao, Jing Li, Lirong Xu, Wei Hong, Yuzhao Yang, and Xudong Chen. "The Glass-Transition Temperature of Supported PMMA Thin Films with Hydrogen Bond/Plasmonic Interface." Polymers 11, no. 4 (2019): 601. http://dx.doi.org/10.3390/polym11040601.
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The interfacial effect is one of the significant factors in the glass-transition temperature (Tg) of the polymeric thin film system, competing against the free surface effect. Herein, the Tgs of poly (methyl methacrylate) (PMMA) films with different thicknesses and substrates are studied by fluorescence measurements, focusing on the influence of interfacial effects on the Tgs. The strong interaction between PMMA and quartz substrate leads to increased Tgs with the decreased thickness of the film. The plasmonic silver substrate causes enhanced fluorescence intensity near the interface, resulting in the delayed reduction of the Tgs with the increasing film thickness. Moreover, as a proof of the interface-dependent Tgs, hydrogen bonds of PMMA/quartz and molecules orientation of PMMA/silver are explored by the Raman spectroscopy, and the interfacial interaction energy is calculated by the molecular dynamics simulation. In this study, we probe the inter-relationship between the interfacial interactions arising from the different substrates and the Tg behavior of polymer thin films.
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Rudmann, Linda, Juan S. Ordonez, Hans Zappe, and Thomas Stieglitz. "Hermetic Electrical Feedthroughs Based on the Diffusion of Platinum into Silicon." International Symposium on Microelectronics 2014, no. 1 (2014): 000729–34. http://dx.doi.org/10.4071/isom-wp45.
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Within this paper a novel approach for the development of hermetic electrical feedthroughs is introduced. So far, every vertical feedthrough induces at the feedthroughs' interfaces possible paths for water to leak across the hermetic barrier into the hermetic package. The presented approach is based on the diffusion of platinum into silicon, locally changing the electrical behavior of the substrate due to the induced impurities. This method avoids destroying the bulk material, in this case silicon, preserving the hermetic barrier environment. Different n-type silicon substrates were investigated for their usability through various diffusion experiments under two gas atmospheres: Argon/hydrogen and pure nitrogen. A significant change in silicon behavior could be shown for one of the used substrates. The current flowing through the bulk could be decreased by a factor of around 12 for an argon/hydrogen atmosphere and by around 10 for pure nitrogen. The current directly correlates with a local increase of the substrates' resistance, demonstrating the possibility of adapting the electrical properties of a substrate to create insulating areas within a conductive substrate.
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Chin, Che-Lun, Lu-Jan Huang, Zheng-Xian Lu, Wei-Chun Weng, and Ling Chao. "Using the Water Absorption Ability of Dried Hydrogels to Form Hydrogel-Supported Lipid Bilayers." Gels 9, no. 9 (2023): 751. http://dx.doi.org/10.3390/gels9090751.
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The formation of supported lipid bilayers (SLBs) on hydrogels can act as a biocompatible anti-fouling interface. However, generating continuous and mobile SLBs on materials other than conventional glass or mica remains a significant challenge. The interaction between lipid membrane vesicles and a typical hydrogel is usually insufficient to induce membrane vesicle rupture and form a planar lipid membrane. In this study, we demonstrate that the water absorption ability of a dried polyacrylamide (PAAm) hydrogel could serve as a driving force to facilitate the formation of the hydrogel–SLBs. The absorption driving force vanishes after the hydrogels are fully hydrated, leaving no extra interaction hindering lipid lateral mobility in the formed SLBs. Our fluorescence recovery after photobleaching (FRAP) results show that SLBs only form on hydrogels with adequate absorption abilities. Moreover, we discovered that exposure to oxygen during drying could lead to the formation of an oxidized crust on the PAAm hydrogel surface, impeding SLB formation. Therefore, minimizing oxygen exposure during drying is crucial to achieving high-quality hydrogel surfaces for SLB formation. This water absorption method enables the straightforward fabrication of hydrogel–SLBs without the need for additional substrates or charges, thereby expanding their potential applications.
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De Obaldia, Elida, Pablo Tirado, Jesús Alcantar, Jorge Montes, and Orlando Auciello. "Photoluminescence in Raman Scattering: Effects of HfO2 Template Layer on Ultrananocrystalline Diamond (UNCD) Films Grown on Stainless Steel Substrates." KnE Engineering 3, no. 1 (2018): 263. http://dx.doi.org/10.18502/keg.v3i1.1441.
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The growth of polycrystalline diamond films can play an important role in industry if they can be grown on industrially used materials like aluminum (Al) or stainless steel (SS). A critical issue related to the growth of ultrananocrystalline diamond (UNCD) thin films on metals like SS, in a Hydrogen rich environment like the one present during growth of UNCD films, is the diffusion of Hydrogen (H) into the SS substrate, as it has been observed in prior research, which results in hydride formation in the SS that induce brittleness in the SS substrate. Several interface layers have been proposed described to avoid the H diffusion into the SS. However, HfO2 has not been explored. The work reported here was focused on investigating the growth of UNCD films on commercially available SS substrates by using an interface layer of HfO2, which was found to be a good diffusion barrier for H to inhibit penetration into the SS substrate. The samples where characterized with SEM and Raman spectroscopy. A photoluminescence (PL) effect, observed in the Raman scattering analysis, is present in all the samples. The PL effect may be due to the interaction of the UNCD / HfO2 interface. and the SS substrate rather than UNCD film alone. The novel result from the experiments described here, is the fact that it is possible to grow UNCD films on unseeded HfO2 layers on SS substrates.Keywords: Poly-crystalline diamond, photoluminescence, UNCD, Stainless Steel, Hafnium Dioxide
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Tanaka, Shingo, Noboru Taguchi, Tomoki Akita, Fuminobu Hori, and Masanori Kohyama. "First-Principles Calculations of Pd/Au(100) Interfaces with Adsorbates." Solid State Phenomena 139 (April 2008): 47–52. http://dx.doi.org/10.4028/www.scientific.net/ssp.139.47.
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Atomic and electronic structures of H-adsorbed Pd overlayers on Au(100) substrates have been studied by first-principles calculations. The geometric strain effects change the electronic structure and local reactivity of the surface. The lattice strained Pd overlayers on Au surfaces have larger adsorption energies for atomic hydrogen than the unstrained Pd slabs. Adsorption energies for several adsorption sites on the models with different numbers of Pd overlayers have been analyzed from the viewpoints of strains and H-Pd and H-substrate interactions.
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Moreau, David, Caroline Chauvet, François Etienne, François P. Rannou, and Laurent Corté. "Hydrogel films and coatings by swelling-induced gelation." Proceedings of the National Academy of Sciences 113, no. 47 (2016): 13295–300. http://dx.doi.org/10.1073/pnas.1609603113.
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Hydrogel films used as membranes or coatings are essential components of devices interfaced with biological systems. Their design is greatly challenged by the need to find mild synthesis and processing conditions that preserve their biocompatibility and the integrity of encapsulated compounds. Here, we report an approach to produce hydrogel films spontaneously in aqueous polymer solutions. This method uses the solvent depletion created at the surface of swelling polymer substrates to induce the gelation of a thin layer of polymer solution. Using a biocompatible polymer that self-assembles at high concentration [poly(vinyl alcohol)], hydrogel films were produced within minutes to hours with thicknesses ranging from tens to hundreds of micrometers. A simple model and numerical simulations of mass transport during swelling capture the experiments and predict how film growth depends on the solution composition, substrate geometry, and swelling properties. The versatility of the approach was verified with a variety of swelling substrates and hydrogel-forming solutions. We also demonstrate the potential of this technique by incorporating other solutes such as inorganic particles to fabricate ceramic-hydrogel coatings for bone anchoring and cells to fabricate cell-laden membranes for cell culture or tissue engineering.
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Qu, Jianzhou, Zhou Yu, and Alexander Urban. "The Mechanism of Hydrogen Evolution Reaction at the Buried Interface of Silica-Coated Electrocatalysts." ECS Meeting Abstracts MA2023-01, no. 36 (2023): 2104. http://dx.doi.org/10.1149/ma2023-01362104mtgabs.
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Semipermeable oxide coatings can protect electrocatalysts in harsh environments without reducing the catalytic performance (Labrador, Esposito et al. ACS Catal. 8, 2018, 1767–1778), making them attractive for direct seawater electrolysis. We recently showed that the buried SiO2/Pt interface of silica-coated platinum electrocatalysts is environment-dependent and changes with the pH value of the electrolyte and the electrode potential (Qu and Urban, ACS Appl. Mater. Interfaces 12, 2020, 52125–52135). Here, we discuss the impact of silica membrane coatings on the hydrogen evolution reaction (HER) mechanism at the interface with different transition-metal surfaces. Stable configurations of the buried SiO2/TM interface at HER conditions were determined using density-functional theory (DFT) calculations. Computed Pourbaix diagrams for different transition-metal substrates show the pH and potential dependence of reaction intermediates and the hydrogen coverage on the metal surface. Our results indicate that the HER mechanism at the buried SiO2/catalyst interfaces may involve the silica membrane. Hence, besides the protective quality of silica membranes, this also points to the possibility of designing synergistic membrane-coated electrocatalysts that surpass the bare surfaces of earth-abundant transition metals in terms of catalytic performance (stability, activity, and/or selectivity).
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Rai, Amrita, Johann P. Klare, Patrick Y. A. Reinke, et al. "Structural and Biochemical Characterization of a Dye-Decolorizing Peroxidase from Dictyostelium discoideum." International Journal of Molecular Sciences 22, no. 12 (2021): 6265. http://dx.doi.org/10.3390/ijms22126265.
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A novel cytoplasmic dye-decolorizing peroxidase from Dictyostelium discoideum was investigated that oxidizes anthraquinone dyes, lignin model compounds, and general peroxidase substrates such as ABTS efficiently. Unlike related enzymes, an aspartate residue replaces the first glycine of the conserved GXXDG motif in Dictyostelium DyPA. In solution, Dictyostelium DyPA exists as a stable dimer with the side chain of Asp146 contributing to the stabilization of the dimer interface by extending the hydrogen bond network connecting two monomers. To gain mechanistic insights, we solved the Dictyostelium DyPA structures in the absence of substrate as well as in the presence of potassium cyanide and veratryl alcohol to 1.7, 1.85, and 1.6 Å resolution, respectively. The active site of Dictyostelium DyPA has a hexa-coordinated heme iron with a histidine residue at the proximal axial position and either an activated oxygen or CN− molecule at the distal axial position. Asp149 is in an optimal conformation to accept a proton from H2O2 during the formation of compound I. Two potential distal solvent channels and a conserved shallow pocket leading to the heme molecule were found in Dictyostelium DyPA. Further, we identified two substrate-binding pockets per monomer in Dictyostelium DyPA at the dimer interface. Long-range electron transfer pathways associated with a hydrogen-bonding network that connects the substrate-binding sites with the heme moiety are described.
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Han, Chenhui, Johannes Zenner, Jacob Johny, Nicolas Kaeffer, Alexis Bordet, and Walter Leitner. "Electrocatalytic hydrogenation of alkenes with Pd/carbon nanotubes at an oil–water interface." Nature Catalysis 5, no. 12 (2022): 1110–19. http://dx.doi.org/10.1038/s41929-022-00882-4.
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AbstractElectrocatalytic hydrogenation (ECH) produces high-value chemicals from unsaturated organics using water as a hydrogen source. However, ECH is limited by the low solubility of substrates when operated under aqueous conditions, by electrical losses when performed in organic electrolytes and, in general, by low faradaic efficiency and fastidious work-up. Here, we show that a Pickering emulsion compartmenting organic substrates and aqueous electrolytes in different phases enables efficient ECH at the interface. We designed a construct comprising Pd nanoparticles immobilized on positively charged carbon nanotubes that localizes at the interface to act as both emulsion stabilizer and electrocatalyst. Applied to the ECH of styrene, the system delivers ethylbenzene at high faradaic efficiency (95.0%) and mass specific current density (–148.1 mA $${{{\mathrm{mg}}}}_{{{{\mathrm{Pd}}}}}^{ - 1}$$ mg Pd − 1 ). The system combines good substrate solubility, high conductivity and simplified product isolation, and has proved applicable to the conversion of various alkenes. This strategy may thus provide alternative solutions to the ECH of substrates with low water solubility, such as bio-oil and bio-crude.
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Pickrell, D. J., W. Zhu, A. R. Badzian, R. E. Newnham, and R. Messier. "Near-interface characterization of diamond films on silica and silicon." Journal of Materials Research 6, no. 6 (1991): 1264–77. http://dx.doi.org/10.1557/jmr.1991.1264.
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The near-interface structure of diamond films grown from a methane and hydrogen gas mixture by microwave plasma enhanced chemical vapor deposition has been studied. Freestanding diamond films grown on both silica and silicon at two different methane concentrations were analyzed by scanning and transmission electron microscopies, electron diffraction, Raman spectroscopy, and secondary ion mass spectroscopy. It was found that the substrate chemistry greatly influenced the nature of the carbon initially deposited on the substrate surface. Diamond formed large flat contact areas on silicon, whereas on silica a particulate type of intermediate layer formed first because of the chemical reactions occurring on and/or with the surface. It was found that the phase content of the films was greatly affected by the methane concentration in hydrogen. At the low (1.0% or less) methane concentrations in hydrogen, phase pure diamond formed; while at the high (5.0%) methane concentration in hydrogen, graphite and disordered carbon were codeposited along with diamond during the early growth stages. Silicon carbide was detected at the diamond interfaces which appeared in discrete areas on silica as opposed to a rather continuous layer as is believed to form on silicon.
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Савин, А. В. "Стационарные состояния односторонне гидрированных листов графена, расположенных на плоских подложках". Физика твердого тела 62, № 3 (2020): 502. http://dx.doi.org/10.21883/ftt.2020.03.49019.560.
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The stationary states of graphene sheets partially hydrogenated on one side and lying on flat substrates are examined. It is shown that such sheets can have stable flat and various scrolled structures. The maximum density of hydrogenation at which the flat structure remains energetically the most favorable depends monotonously on the value of the adhesion of the sheet with the substrate. The stronger is the energy of interaction with the substrate, the higher is the maximum possible density of sheet hydrogenation. The dimensionless maximum density of hydrogenation is p=0.12 for the substrate with the surface of crystal ice, for graphite p=0.21, for silicon carbide p=0.28 and p=0.48 for nickel. The simulation allows us to conclude that the maximum hydrogenation of a graphene sheet (one hydrogen atom per two carbon atoms) and the production of a graphone sheet from it can be achieved only by placing the sheet on the surface of crystalline nickel.
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Hens, Philip, Julian Müller, Erdmann Spiecker, and Peter J. Wellmann. "Defect Structures at the Silicon/3C-SiC Interface." Materials Science Forum 717-720 (May 2012): 423–26. http://dx.doi.org/10.4028/www.scientific.net/msf.717-720.423.
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In all heteroepitaxial systems the interface between substrate and layer is a crucial point. In this work SEM and TEM studies on the interface between silicon substrate and cubic silicon carbide (3C-SiC) layers obtained by chemical vapor deposition (CVD) are presented. A clear connection between process parameters, like the design of substrate cleaning, and the heating ramp, and resulting defect structures at the substrate-layer interface could be found. Whereas the process step of etching in hot hydrogen for oxide removal is crucial for avoiding the generation of closed voids of type 2, the design of the temperature ramp up to growth temperature during carbonization influences the interface roughness. Here a fast ramp helps to obtain a flat interface.
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Mishyn, Vladyslav, David Hickey, and Sofiene Abdellaoui. "NAD-Regenerating Biocathode Applied to Electroenzymatic Conversion of Lignin." ECS Meeting Abstracts MA2023-02, no. 27 (2023): 1431. http://dx.doi.org/10.1149/ma2023-02271431mtgabs.
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Non-renewable and limited fossil resources (i.e. petroleum, coal, and natural gas) have been used over the last years for the production of energy, commodity chemicals, and polymer materials. Nonetheless, the extraction and consumption of these resources leads to deleterious and irreversible environmental impacts. As a sustainable alternative, lignin, one of the major components of lignocellulosic biomass, represents the most promising renewable raw material to produce aromatic-based chemicals and high value-added products. However, the use of lignin as a source of valuable molecules similar to the petroleum-derived chemicals is hindered due to its recalcitrance and structural heterogeneity. Biological approaches have been studied to develop selective and ecofriendly pathways for lignin valorization. It has been reported that some microorganisms can cleave selectively β-ether bonds representing more than a half of lignin bonding pattern.[1] The etherolytic pathway of the soil probacterium Sphingobium paucimobilis, which involves NAD-dependent dehydrogenases and β-etherases, has been well characterized for this purpose.[2] Here we focus on the design of a bioanode combining NAD-regenerating properties and the immobilization of lignin degrading enzymatic cascade to cleave such bonds. We explored the possibility of combing in situ electrochemical regeneration of NAD+ cofactor with a surface immobilized biocatalysts on a single interface. First, we have demonstrated that the electrodes based on multiwalled carbon nanotubes modified with toluidine blue are capable to regenerate NAD+ cofactor at low potential from its reduced form. This process is essential for dehydrogenases activities. Secondly, we used cross-linked hydrogel of pyrene-modified linear poly(ethyleneimine) to entrap the enzymes on the electrode surface.[3] The obtained bioanode modified with NAD-regenerating catalyst and the multi-enzymatic cascade of Lig enzymes was tested in the presence of guaiacylglycerol-β-guaiacylether (GGE), a lignin dimer substrate with β-ether bond, to produce γ-hydroxypropiovanillone (HPV). We believe that such electrochemical systems employing the enzymatic cascade acting like a metabolic funnel with the simultaneous regeneration of the cofactor would permit to refine the heterogeneous mixture of aromatics from lignin depolymerization products into a uniform distribution of value-added compounds. [1] Renewable Sustainable Energy Rev., 2022, 157, 112025. [2] Catal. Sci. Technol., 2016,6, 2195-2205. [3] Chem. Sci., 2018,9, 5172-5177. Figure 1
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Chiou, W. A., M. S. Wong, F. R. Chen, D. X. Li, R. P. H. Chang, and M. Meshii. "Techniques in preparing TEM specimens of diamond thin films." Proceedings, annual meeting, Electron Microscopy Society of America 47 (August 6, 1989): 716–17. http://dx.doi.org/10.1017/s0424820100155554.
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Diamond, with its unique combination of optical, physical, mechanical, and electrical properties, has provided a superior potential for industrial and military applications. It has caught the attention of a growing number of researchers over the past decade. The recent development of low-pressure vapor deposition of diamond film has greatly increased the prospects for the practical utilization of diamond. To use a diamond film, the nature of the interface between diamond film and substrate must be understood. This paper presents three different techniques in preparing diamond thin films specimens for TEM study of the interfacial structure between diamond and substrate as well as the internal structure of diamond crystals.Diamond crystallites and films produced by radio frequency (RF) and microwave (MW) plasma enhanced chemical vapor deposition (PECVD) techniques were deposited on Si (100), polycrystalline Mo, and Cu substrates (925°C) at 40 mbar, with 0.5% methane and 0.2% oxygen in hydrogen gas at a total flow rate of 200 seem for MWPECVD and 2000 seem for RFPECVD. To examine the internal and interfacial structures of the diamond film on different substrates, three techniques were employed: (1) the chemical etching technique, which removes substrates then the substrate-free diamond film was supported on a Cu grid, (2) the conventional epoxy-embedding technique for cross-section study, and (3) the direct deposition of diamond crystallites on metal grids.
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Rogne, Per, Marie Rosselin, Christin Grundström, Christian Hedberg, Uwe H. Sauer, and Magnus Wolf-Watz. "Molecular mechanism of ATP versus GTP selectivity of adenylate kinase." Proceedings of the National Academy of Sciences 115, no. 12 (2018): 3012–17. http://dx.doi.org/10.1073/pnas.1721508115.
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Enzymatic substrate selectivity is critical for the precise control of metabolic pathways. In cases where chemically related substrates are present inside cells, robust mechanisms of substrate selectivity are required. Here, we report the mechanism utilized for catalytic ATP versus GTP selectivity during adenylate kinase (Adk) -mediated phosphorylation of AMP. Using NMR spectroscopy we found that while Adk adopts a catalytically competent and closed structural state in complex with ATP, the enzyme is arrested in a catalytically inhibited and open state in complex with GTP. X-ray crystallography experiments revealed that the interaction interfaces supporting ATP and GTP recognition, in part, are mediated by coinciding residues. The mechanism provides an atomic view on how the cellular GTP pool is protected from Adk turnover, which is important because GTP has many specialized cellular functions. In further support of this mechanism, a structure–function analysis enabled by synthesis of ATP analogs suggests that a hydrogen bond between the adenine moiety and the backbone of the enzyme is vital for ATP selectivity. The importance of the hydrogen bond for substrate selectivity is likely general given the conservation of its location and orientation across the family of eukaryotic protein kinases.
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Aizawa, Tatsuhiko, Yasuo Saito, Hideharu Hasegawa, and Kenji Wasa. "Fabrication of Optimally Micro-Textured Copper Substrates by Plasma Printing for Plastic Mold Packaging." International Journal of Automation Technology 14, no. 2 (2020): 200–207. http://dx.doi.org/10.20965/ijat.2020.p0200.
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Micro-embossing using plasma printed micro-punch was proposed to form micro-groove textures into the copper substrate for plastic packaging of hollowed GaN HEMT-chips. In particular, the micro-groove network on the copper substrate was optimized to attain uniform stress distribution with maximum stress level being as low as possible. Three-dimensional finite element analysis was employed to investigate the optimum micro-grooving texture-topology and to attain the uniform stress distribution on the joined interface between the plastic mold and the textured copper substrate. Thereafter, plasma printing was utilized to fabricate the micro-punch for micro-embossing of the micro-grooving network into the copper substrate as a designed optimum micro-texture. This plasma printing mainly consisted of three steps. Two-dimensional micro-pattern was screen-printed onto the AISI316 die surface as a negative pattern of the optimum CAD data. The screen-printed die was plasma nitrided at 673 K for 14.4 ks at 70 Pa under the hydrogen-nitrogen mixture for selective nitrogen supersaturation onto the unprinted die surfaces. A micro-punch was developed by mechanically removing the printed parts of die material. Then, fine computer numerical control (CNC) stamping was used to yield the micro-embossed copper substrate specimens. Twelve micro-textured substrates were molded into packaged specimens by plastic molding. Finally, gross leak testing was employed to evaluate the integrity of the joined interface. The takt time required to yield the micro-grooved copper substrate by the present method was compared to the picosecond laser micro-grooving; the former showed high productivity based on this parameter.
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Yin, Simin, Shun Liu, Yongfeng Yuan, Shaoyi Guo, and Zhaohui Ren. "Octahedral Shaped PbTiO3-TiO2 Nanocomposites for High-Efficiency Photocatalytic Hydrogen Production." Nanomaterials 11, no. 9 (2021): 2295. http://dx.doi.org/10.3390/nano11092295.
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In this work, octahedral shaped PbTiO3-TiO2 nanocomposites have been synthesized by a facile hydrothermal method, where perovskite ferroelectric PbTiO3 nanooctahedra were employed as substrate. The microstructures of the composites were investigated systemically by using XRD, SEM, TEM and UV-Vis spectroscopy. It was revealed that anantase TiO2 nanocrystals with a size of about 5 nm are dispersed on the surface of the {111} facets of the nanooctahedron crystals. Photocatalytic hydrogen production of the nanocomposites has been evaluated in a methanol alcohol-water solution under UV light enhanced irradiation. The H2 evolution rate of the nanocomposites increased with an increased loading of TiO2 on the nanooctahedra. The highest H2 evolution rate was 630.51 μmol/h with the highest concentration of TiO2 prepared with 2 mL tetrabutyl titanate, which was about 36 times higher than that of the octahedron substrate. The enhanced photocatalytic reactivity of the nanocomposites is possibly ascribed to the UV light absorption of the nanooctahedral substrates, efficient separation of photo-generated carriers via the interface and the reaction on the surface of the TiO2 nanocrystals.
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Arendse, Christopher J., Theophillus F. G. Muller, Franscious R. Cummings, and Clive J. Oliphant. "Oxidation Reduction in Nanocrystalline Silicon Grown by Hydrogen-Profiling Technique." Journal of Nano Research 41 (May 2016): 9–17. http://dx.doi.org/10.4028/www.scientific.net/jnanor.41.9.
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The deposition of a compact amorphous silicon/nano-crystalline silicon material is demonstrated by hot-wire chemical vapour deposition using a sequential hydrogen profiling technique at low hydrogen dilutions. Nano-crystallite nucleation occurs at the substrate interface that develops into a uniform, porous crystalline structure as the growth progresses. A further reduction in the H-dilution results in the onset of a dense amorphous silicon layer. The average crystalline volume fraction and nano-crystallite size in the sample bulk amounts to 30% and 6 nm, respectively, as probed by Raman spectroscopy using the 647 nm excitation. The change in hydrogen dilution is accompanied by a graded hydrogen concentration depth-profile, where the hydrogen concentration decreases as the growth progresses. The level of post-deposition oxidation is considerably reduced, as inferred from infrared spectroscopy. The presence of oxygen is mainly confined to the substrate interface as a result of thermal oxidation during thin film growth.
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Priestley, Rodney D., Manish K. Mundra, Nina J. Barnett, Linda J. Broadbelt, and John M. Torkelson. "Effects of Nanoscale Confinement and Interfaces on the Glass Transition Temperatures of a Series of Poly(n-methacrylate) Films." Australian Journal of Chemistry 60, no. 10 (2007): 765. http://dx.doi.org/10.1071/ch07234.
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We use fluorescence from dye-labelled polymer to measure the glass transition temperatures (Tgs) across single-layer films and near surfaces and silica interfaces in bilayer films for a series of poly(n-methacrylate)s. With nanoscale confinement, the average Tg across a film supported on silica increases for poly(methyl methacrylate) (PMMA), decreases for poly(ethyl methacrylate) (PEMA) and poly(propyl methacrylate), and is nearly invariant for poly(iso-butyl methacrylate) (PIBMA). These trends are consistent with the relative strengths of local perturbations to Tg caused by surfaces and substrates as measured in bilayer films. The substrate effect, which increases Tg via hydrogen-bonding interactions between the polymer and hydroxyl groups on the silica surface, is stronger than the free-surface effect in PMMA. The free-surface effect, which reduces Tg via a reduction in the required cooperativity of the glass transition dynamics, is stronger than the substrate effect in PEMA. The substrate and free-surface effects have similar strengths in perturbing the local Tg in PIBMA, resulting in a net cancellation of effects when measurements are made across single-layer films.
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Nehate, Shraddha Dhanraj, Ashwin Kumar Saikumar, and Kalpathy B. Sundaram. "Influence of Substrate Temperature on Electrical and Optical Properties of Hydrogenated Boron Carbide Thin Films Deposited by RF Sputtering." Coatings 11, no. 2 (2021): 196. http://dx.doi.org/10.3390/coatings11020196.
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Amorphous hydrogenated boron carbide films were deposited on silicon and glass substrates using radio frequency sputtering. The substrate temperature was varied from room temperature to 300 °C. The substrate temperature during deposition was found to have significant effects on the electrical and optical properties of the deposited films. X-ray photoelectron spectroscopy (XPS) revealed an increase in sp2-bonded carbon in the films with increasing substrate temperature. Reflection electron energy loss spectroscopy (REELS) was performed in order to detect the presence of hydrogen in the films. Metal-insulator-metal (MIM) structure was developed using Al and hydrogenated boron carbide to measure dielectric value and resistivity. Deposited films exhibited lower dielectric values than pure boron carbide films. With higher substrate deposition temperature, a decreasing trend in dielectric value and resistivity of the films was observed. For different substrate temperatures, the dielectric value of films ranged from 6.5–3.5, and optical bandgap values were between 2.25–2.6 eV.
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Kovach, Ildiko M. "Proton Bridging in Catalysis by and Inhibition of Serine Proteases of the Blood Cascade System." Life 11, no. 5 (2021): 396. http://dx.doi.org/10.3390/life11050396.
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Inquiries into the participation of short hydrogen bonds in stabilizing transition states and intermediate states in the thrombin, factor Xa, plasmin and activated protein C–catalyzed reactions revealed that specific binding of effectors at Sn, n = 1–4 and S’n, n = 1–3 and at remote exosites elicit complex patterns of hydrogen bonding and involve water networks. The methods employed that yielded these discoveries include; (1) kinetics, especially partial or full kinetic deuterium solvent isotope effects with short cognate substrates and also with the natural substrates, (2) kinetic and structural probes, particularly low-field high-resolution nuclear magnetic resonance (1H NMR), of mechanism-based inhibitors and substrate-mimic peptide inhibitors. Short hydrogen bonds form at the transition states of the catalytic reactions at the active site of the enzymes as they do with mechanism-based covalent inhibitors of thrombin. The emergence of short hydrogen bonds at the binding interface of effectors and thrombin at remote exosites has recently gained recognition. Herein, I describe our contribution, a confirmation of this discovery, by low-field 1H NMR. The principal conclusion of this review is that proton sharing at distances below the sum of van der Waals radii of the hydrogen and both donor and acceptor atoms contribute to the remarkable catalytic prowess of serine proteases of the blood clotting system and other enzymes that employ acid-base catalysis. Proton bridges also play a role in tight binding in proteins and at exosites, i.e., allosteric sites, of enzymes.
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Zeng, Zhenhua. "(Invited) Toward Rigorous Modeling of Metal-Metal, Metal-Oxide and Oxide-Oxide Interfaces for the Electrochemical Oxygen Cycle." ECS Meeting Abstracts MA2023-01, no. 45 (2023): 2476. http://dx.doi.org/10.1149/ma2023-01452476mtgabs.
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To achieve Net-Zero Emissions by 2050, hydrogen and hydrogen fuel cells will play a significant role in powering vehicles. In this presentation, I will show, through first-principles-based modeling, how to achieve rigorous modeling of solid-solid interface for the hydrogen and oxygen evolution reactions in electrolysis and the oxygen reduction reaction in fuel cells; and how the fundamental understanding paves the way toward developing both model electrocatalysts and industrial electrocatalysts with significantly improved performance. Specifically, I will introduce the following three topics. [1] metal-metal interfaces: strain evolution and strain tuning of epitaxial, stepped and free-standing platinum group metals for the oxygen reduction reaction in fuel cells.(1) [2] metal-oxide interfaces: stability and activity of monolayer oxide/Pt interface toward improving the hydrogen evolution reaction in alkaline conditions.(2) [3] oxide-oxide interfaces: self-consistent modeling of active phases, reaction centers, and catalytic mechanisms of Ni- and Co-based layered double hydroxides for the oxygen evolution reaction.(3, 4) L. Wang, Z. Zeng, W. Gao, T. Maxson, D. Raciti, M. Giroux, X. Pan, C. Wang, J. Greeley, Tunable intrinsic strain in two-dimensional transition metal electrocatalysts. Science 363, 870-874 (2019). Z. Zeng, K.-C. Chang, J. Kubal, N. M. Markovic, J. Greeley, Stabilization of ultrathin (hydroxy)oxide films on transition metal substrates for electrochemical energy conversion. Nature Energy 2, 17070 (2017). F. Dionigi, Z. Zeng, I. Sinev, T. Merzdorf, S. Deshpande, M. B. Lopez, S. Kunze, I. Zegkinoglou, H. Sarodnik, D. Fan, A. Bergmann, J. Drnec, J. F. d. Araujo, M. Gliech, D. Teschner, J. Zhu, W.-X. Li, J. Greeley, B. R. Cuenya, P. Strasser, In-situ structure and catalytic mechanism of NiFe and CoFe layered double hydroxides during oxygen evolution. Nature Communications 11, 2522 (2020). F. Dionigi, J. Zhu, Z. Zeng, T. Merzdorf, H. Sarodnik, M. Gliech, L. Pan, W.-X. Li, J. Greeley, P. Strasser, Intrinsic Electrocatalytic Activity for Oxygen Evolution of Crystalline 3d-Transition Metal Layered Double Hydroxides. Angew. Chem., Int. Ed. 60, 14446-14457 (2021). Figure 1
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Zhang, Hui, Han Qin Liang, Yong Jie Yan, Yan Liu, Xue Jian Liu, and Zheng Ren Huang. "Wetting Behaviors of Pure Nickel and Nickel-Based Alloys on Sintered ZrB2-SiC Ceramics." Key Engineering Materials 655 (July 2015): 72–77. http://dx.doi.org/10.4028/www.scientific.net/kem.655.72.
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The wetting and spreading behaviors of pure nickel and nickel based alloys on sintered ZrB2-SiC ceramics and their interfacial microstructures were investigated in this presentation. The nickel-based alloys were mainly the commercial nickel-molybdenum-chromium products. The wetting and spreading properties were observed by a real-time thermal optical measurement system under flowing argon-5%hydrogen atmosphere. As temperature increased, the pure nickel cylinder sample on ZrB2-SiC substrate had few changes before 1228°C except for the thermal expansion in size. After that, liquid phase formed and spread gradually on the ceramic substrate. The contact angle was about 15o after holding 15min at 1600°C. Therefore, pure nickel could contact sintered ZrB2-SiC ceramics well. Meanwhile, the introduction of molybdenum and/or chromium in the pure nickel was beneficial for the wetting of nickel on sintered ZrB2-SiC ceramics. The contact angles of Ni-28Mo and Ni-16Mo-23Cr alloys on sintered ZrB2-SiC ceramics after 1600°C/15min were 13o and 2o, respectively. In addition, the temperatures of the liquid drop formed rose obviously in contrast to the pure nickel. The SEM images indicated that the interfacial microstructures of Ni-based alloys on sintered ZrB2-SiC ceramic substrates were uniform and the dissolved boundaries showed that they had a good bonding. However, some cracks were found in the Ni/ZrB2-SiC system for their high thermal mismatch. On the other hand, the Ni-Mo (-Cr)/ZrB2-SiC interface had few defections and evident elemental diffusion between the ceramic substrates and the alloys were found at the interface.
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Tamura, Motonori. "Hydrogen Permeation of Multi-Layered-Coatings." Advanced Materials Research 1152 (April 2019): 9–18. http://dx.doi.org/10.4028/www.scientific.net/amr.1152.9.
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Using a substrate of AISI 316L austenitic stainless steel, which is used for components in high-pressure hydrogen systems, the hydrogen barrier properties of samples with single-layer coatings of TiC, TiN, and TiAlN as well as a multi-layered coating of TiAlN and TiMoN were evaluated. The ion plating method was used, and coating thicknesses of 2.0–2.6 μm were obtained. Hydrogen permeation tests were carried out under a differential hydrogen pressure of 400 kPa and at a temperature between 573 and 773 K, and the quantities of hydrogen that permeated the samples were measured. This study aimed at elucidating the relationship between the microstructures of the coatings and the hydrogen permeation properties. Coatings of TiC, TiN, TiAlN, and TiAlN/TiMoN facilitated reductions of the hydrogen permeabilities to 1/100 or less of that of the uncoated substrate. The samples coated with TiN and TiC that developed columnar crystals vertical to the substrate exhibited higher hydrogen permeabilities. The experiment confirmed that the coatings composed of fine crystal grains were highly effective as hydrogen barriers, and that this barrier property became even more efficient if multiple layers of the coatings were applied. The crystal grain boundaries of the coating and interfaces of each film in a multi-layered coating may serve as hydrogen trapping sites. We speculate that fine crystal structures with multiple crystal grain boundaries and multi-layered coating interfaces will contribute to the development of hydrogen barriers.
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Li, Hua Long, Jianlong Lin, and Jerzy A. Szpunar. "Software for Simulation of Oxidation Processes." Defect and Diffusion Forum 237-240 (April 2005): 189–94. http://dx.doi.org/10.4028/www.scientific.net/ddf.237-240.189.
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A methodology for discrete simulation has been developed that incorporates many structural characteristics of polycrystalline material properties, such as: texture, grain boundaries, microstructure, phase composition, chemical composition, stored energy, and residual stresses. The computer models that have been developed to study oxidation processes are based on a quantitative description of the oxide and substrate structure. That description allows for the simulation of the transport of metal and oxygen ions along interfaces and bulk portions of material and the formation of oxide structure. The proposed model can help researchers and engineers to understand the physical mechanism of oxidation in order to predict material behavior and optimize material processing and properties. In this paper, the results on the simulation of the oxidation process are presented on different substrates of Zr-Nb alloys, which are used for the manufacturing the pressure tubes used in the CANDU nuclear reactors. The effects of substrate texture, microstructure, grain boundaries, and beta phase distribution on oxidation kinetics and hydrogen permeation are demonstrated.
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Yi, Bo, Tianjie Li, Boguang Yang, et al. "Surface hydrophobization of hydrogels via interface dynamics-induced network reconfiguration." Nature Communications 15, no. 1 (2024). http://dx.doi.org/10.1038/s41467-023-44646-5.
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AbstractEffective and easy regulation of hydrogel surface properties without changing the overall chemical composition is important for their diverse applications but remains challenging to achieve. We report a generalizable strategy to reconfigure hydrogel surface networks based on hydrogel–substrate interface dynamics for manipulation of hydrogel surface wettability and bioadhesion. We show that the grafting of hydrophobic yet flexible polymeric chains on mold substrates can significantly elevate the content of hydrophobic polymer backbones and reduce the presence of polar groups in hydrogel surface networks, thereby transforming the otherwise hydrophilic hydrogel surface into a hydrophobic surface. Experimental results show that the grafted highly dynamic hydrophobic chains achieved with optimal grafting density, chain length, and chain structure are critical for such substantial hydrogel surface network reconfiguration. Molecular dynamics simulations further reveal the atomistic details of the hydrogel network reconfiguration induced by the dynamic interface interactions. The hydrogels prepared using our strategy show substantially enhanced bioadhesion and transdermal delivery compared with the hydrogels of the same chemical composition but fabricated via the conventional method. Our findings provide important insights into the dynamic hydrogel–substrate interactions and are instrumental to the preparation of hydrogels with custom surface properties.
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Ren, Xingrong, Jiayi Zhang, Fan Yang, Hong Xu, Gaoyang Guo, and Yunbing Wang. "Enzyme‐Immobilized Surface‐Catalyzed Cross‐Linking: Creating Multifunctional Double Network Hydrogel Coatings on Diverse Substrates." Advanced Functional Materials, March 7, 2024. http://dx.doi.org/10.1002/adfm.202312465.
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AbstractHydrogel coatings, with natural tissue‐like mechanical and biological compatibility, demonstrate promise for bulk material applications. However, existing coating methods lack efficiency and control, especially when dealing with complex geometries, diverse substrate materials, and varying sizes. In this study, an enzyme‐immobilized surface‐catalyzed cross‐link approach is proposed for the growth of hydrogel coatings on multiple substrates, accommodating various materials and shapes. The hydrogel coating is formed through the catalytic action of interface‐immobilized enzymes, which induce the crosslinking of hyaluronic acid, and its mechanical properties are further enhanced by introducing a secondary polyacrylamide network. This approach enables the controlled growth of conformal double network hydrogel coatings with a desired thickness on a wide range of substrate surfaces and devices. Notably, the hydrogel coating exhibits remarkable lubricity and anti‐thrombotic properties, especially desire for medical intervention devices. This advancement offers a universal route to impart biocompatible soft interfaces to bulk materials or devices.
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Yu, Han, Qiaohong Xiao, Guilin Qi, et al. "A Hydrogen Bonds-Crosslinked Hydrogels With Self-Healing and Adhesive Properties for Hemostatic." Frontiers in Bioengineering and Biotechnology 10 (April 14, 2022). http://dx.doi.org/10.3389/fbioe.2022.855013.
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Hydrogels with adhesive properties have the potential for rapid haemostasis and wound healing in uncontrolled non-pressurized surface bleeding. Herein, a typical hydrogen bond-crosslinked hydrogel with the above functions was constructed by directly mixing solutions of humic acid (HA) and polyvinylpyrrolidone (PVP), in which the HA worked as a crosslinking agent to form hydrogen bonds with the PVP. By altering the concentration of HA, a cluster of stable and uniform hydrogels were prepared within 10 s. The dynamic and reversible nature of the hydrogen bonds gave the HA/PVP complex (HPC) hydrogels injectability and good flexibility, as well as a self-healing ability. Moreover, the numerous functional groups in the hydrogels enhanced the cohesion strength and interaction on the interface between the hydrogel and the substrate, endowing them with good adhesion properties. The unique chemical composition and cross-linking mechanism gave the HPC hydrogel good biocompatibility. Taking advantage of all these features, the HPC hydrogels obtained in this work were broadly applied as haemostatic agents and showed a good therapeutic effect. This work might lead to an improvement in the development of multifunctional non-covalent hydrogels for application to biomaterials.
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Wen, Zhixuan, Teng Zhou, Qian Xu, et al. "Functional hydrogel-plastic hybrids inspired by the structural characteristics of mussels." NPG Asia Materials 15, no. 1 (2023). http://dx.doi.org/10.1038/s41427-023-00491-y.
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AbstractShellfish with rigid shells prevent damage to their delicate internal cores, and their soft bonding muscles drive the opening and closing of the shells. This synergism of rigid and soft materials provides shellfish with unique environmental adaptation. Inspired by the structural characteristics of mussels, a riveting layer was introduced into hydrogel-plastic hybrids for bonding hydrogel networks and plastic substrates. The bonding strength of the hydrogel on the polypropylene (PP) substrate was approximately 1.52 MPa, and the interface toughness reached 1450 J m−2. Furthermore, the integration of plastics and microscale hydrogels, as well as abscised or prefabricated hydrogels, could also be fabricated through the same process. By using this strategy, a hydrogel-plastic hybrid-based device with temperature responsiveness and scratch resistance was fabricated and could mimic the basic activities of mussels. This work improves the functional materials used in programmable engineering systems and could facilitate the construction of intelligent robots.
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Perez, Edward, Linda G. Cima, David Miller, and Edward W. Merrill. "Bilayer Composite Hydrogels for Corneal Prostheses." MRS Proceedings 252 (1991). http://dx.doi.org/10.1557/proc-252-375.
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ABSTRACTA two-layer composite material composed of a thin-layer of corneal tissue and a synthetic polyethylene oxide (PEO) hydrogel is described. The material is designed to provide a suitable substrate for corneal epithelial cell growth while maintaining the desirable characteristics of hydrogels, i.e. clarity, flexibility, and ability to allow diffusive flow of nutrients. The gels are synthesized via electron irradiation induced crosslinking of an aqueous solution of PEO onto a thin layer of collagenous tissue substrate. light microscopic studies indicate that the interface between the corneal tissue and PEO gel appears well adherent with no gaps in the interface. SEM studies of the material surface show an architecture similar to that of normal corneal tissue. Surface analytical techniques were used to identify amino-acids covalently bound to the gel at the gel/collagen interface after the proteinaceous material was removed. ESCA survey scans identified the presence of nitrogen on exposed gel/collagen interfaces and amino acid labelling confirmed the presence of amino acids. ATR-IR studies identifed increased absorption for the gel collagen interfaces at 1640 cm− 1 and 1540 cm−1 indicative of bound amino acids.
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Macalester, William, Asme Boussahel, Rafael O. Moreno-Tortolero, et al. "A 3D In-vitro model of the human dentine interface shows long-range osteoinduction from the dentine surface." International Journal of Oral Science 16, no. 1 (2024). http://dx.doi.org/10.1038/s41368-024-00298-9.
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AbstractEmerging regenerative cell therapies for alveolar bone loss have begun to explore the use of cell laden hydrogels for minimally invasive surgery to treat small and spatially complex maxilla-oral defects. However, the oral cavity presents a unique and challenging environment for in vivo bone tissue engineering, exhibiting both hard and soft periodontal tissue as well as acting as key biocenosis for many distinct microbial communities that interact with both the external environment and internal body systems, which will impact on cell fate and subsequent treatment efficacy. Herein, we design and bioprint a facile 3D in vitro model of a human dentine interface to probe the effect of the dentine surface on human mesenchymal stem cells (hMSCs) encapsulated in a microporous hydrogel bioink. We demonstrate that the dentine substrate induces osteogenic differentiation of encapsulated hMSCs, and that both dentine and β-tricalcium phosphate substrates stimulate extracellular matrix production and maturation at the gel-media interface, which is distal to the gel-substrate interface. Our findings demonstrate the potential for long-range effects on stem cells by mineralized surfaces during bone tissue engineering and provide a framework for the rapid development of 3D dentine-bone interface models.
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Li, Min, Honglang Lu, Menghan Pi, et al. "Water‐Induced Phase Separation for Anti‐Swelling Hydrogel Adhesives in Underwater Soft Electronics." Advanced Science, September 26, 2023. http://dx.doi.org/10.1002/advs.202304780.
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AbstractThe development of hydrogel‐based underwater electronics has gained significant attention due to their flexibility and portability compared to conventional rigid devices. However, common hydrogels face challenges such as swelling and poor underwater adhesion, limiting their practicality in water environments. Here, a water‐induced phase separation strategy to fabricate hydrogels with enhanced anti‐swelling properties and underwater adhesion is presented. By leveraging the contrasting affinity of different polymer chains to water, a phase‐separated structure with rich hydrophobic and dilute hydrophilic polymer phases is achieved. This dual‐phase structure, meticulously characterized from the macroscopic to the nanoscale, confers the hydrogel network with augmented retractive elastic forces and facilitates efficient water drainage at the gel‐substrate interface. As a result, the hydrogel exhibits remarkable swelling resistance and long‐lasting adhesion to diverse substrates. Additionally, the integration of carboxylic multiwalled carbon nanotubes into the hydrogel system preserves its anti‐swelling and adhesion properties while imparting superior conductivity. The conductive phase‐separated hydrogel exhibited great potential in diverse underwater applications, including sensing, communication, and energy harvesting. This study elucidates a facile strategy for designing anti‐swelling underwater adhesives by leveraging the ambient solvent effect, which is expected to offer some insights for the development of next‐generation adhesive soft materials tailored for aqueous environments.
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Yongsunthon, Ruchirej, David E. Baker, Wendy A. Baker, et al. "A Cell's Perspective of its Culture Surface." MRS Proceedings 1060 (2007). http://dx.doi.org/10.1557/proc-1060-ll08-06.
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ABSTRACTAtomic Force Microscopy (AFM) was employed to probe the internal structure of living HepG2/C3A cells grown on various commercially-available substrates. In order to understand the driving mechanisms behind the different cell morphologies, the surface properties of these substrates was characterized with AFM and related techniques. The roughness of a 10μm×10μm region of a series of substrates was determined and found to be independent of both coating and culture media, with the exception of thick hydrogel-like coatings. Probing with functionalized tips could not distinguish relative degrees of hydrophobicity under cell culture media, presumably because Debye shielding masks the substrate surfaces. Force spectroscopy was performed on the surfaces to determine exposed surface proteins/polymers intrinsic to the substrate and adsorbed from culture media. Preliminary investigation of cell-mediated substrate reconstruction suggests that the cells secrete large (1000kDa) polymeric molecules at the substrate interface.
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Belyaeva, Liubov, Cyril Ludwig, Yu‐Cheng Lai, Chia‐Ching Chou, and Chih‐Jen Shih. "Uniform, Strain‐Free, Large‐Scale Graphene and h‐BN Monolayers Enabled by Hydrogel Substrates." Small, October 22, 2023. http://dx.doi.org/10.1002/smll.202307054.
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AbstractTranslation of the unique properties of 2D monolayers from non‐scalable micron‐sized samples to macroscopic scale is a longstanding challenge obstructed by the substrate‐induced strains, interface nonuniformities, and sample‐to‐sample variations inherent to the scalable fabrication methods. So far, the most successful strategies to reduce strain in graphene are the reduction of the interface roughness and lattice mismatch by using hexagonal boron nitride (h‐BN), with the drawback of limited uniformity and applicability to other 2D monolayers, and liquid water, which is not compatible with electronic devices. This work demonstrates a new class of substrates based on hydrogels that overcome these limitations and excel h‐BN and water substrates at strain relaxation enabling superiorly uniform and reproducible centimeter‐sized sheets of unstrained monolayers. The ultimate strain relaxation and uniformity are rationalized by the extreme structural adaptability of the hydrogel surface owing to its high liquid content and low Young's modulus, and are universal to all 2D materials irrespective of their crystalline structure. Such platforms can be integrated into field effect transistors and demonstrate enhanced charge carrier mobilities in graphene. These results present a universal strategy for attaining uniform and strain‐free sheets of 2D materials and underline the opportunities enabled by interfacing them with soft matter.
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Chen, Qin, Xinyue Zhang, Siyu Liu, et al. "Cartilage-bone inspired the construction of soft-hard composite material with excellent interfacial binding performance and low friction for artificial joints." Friction, July 16, 2022. http://dx.doi.org/10.1007/s40544-022-0645-2.
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AbstractInspired by the cartilage-bone structure in natural joints, soft-hard integrated materials have received extensive attention, which are the most promising candidates for artificial joints due to their combination of excellent load-bearing properties and lubricating properties. The latest progress showed that the combination of hydrogel and titanium alloy can realize a bionic natural joint lubrication system on the surface of titanium alloy. However, obtaining a tough interface between the hydrogel (soft and wet) and the titanium substrate (hard and dry) is still a great challenge. Here, we designed a “soft (hydrogel)-hard (Ti6Al4V)” integrated material with outstanding combination, which simulates the structure and function of cartilage-bone in the natural joint. The load-bearing properties, binding performance, and tribological behaviors for different forms of the soft-hard integrated materials were investigated. The results showed that the hydrogel layer and Ti6Al4V substrate possess ultra-high interfacial toughness (3,900 J/m2). In addition, the combination of the hydrogel layer and Ti6Al4V substrate provided a good lubrication system to endow the “soft (hydrogel)-hard (Ti6Al4V)” integrated material with high load-bearing and excellent tribological properties. Therefore, this study provided an effective strategy for prolonging the service life of Ti6Al4V in the biomedical field.