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In the electrochemical CO 2 reduction reaction (CO 2 RR), Cu alloy electrocatalysts can control the CO 2 RR selectivity by modulating the intermediate binding energy. Here, we report the thermodynamic-based Cu-Sn bimetallic phase control in heterogeneous catalysts for selective CO 2 conversion. Starting from the thermodynamic understanding about Cu-Sn bimetallic compounds, we established the specific processing window for Cu-Sn bimetallic phase control. To modulate the Cu-Sn bimetallic phases, we controlled the oxygen partial pressure (pO 2 ) during the calcination of electrospun Cu and Sn ions-incorporated nanofibers (NFs). This resulted in the formation of CuO-SnO 2 NFs (full oxidation), Cu-SnO 2 NFs (selective reduction), Cu 3 Sn/CNFs, Cu 41 Sn 11 /CNFs, and Cu 6 Sn 5 /CNFs (full reduction). In the CO 2 RR, CuO-SnO 2 NFs exhibited formate (HCOO - ) production and Cu-SnO 2 NFs showed carbon monoxide (CO) production with the faradaic efficiency (FE) of 65.3% at -0.99 V ( vs. RHE) and 59.1% at -0.89 V ( vs. RHE) respectively. Cu-rich Cu 41 Sn 11 /CNFs and Cu 3 Sn/CNFs enhanced the methane (CH 4 ) production with the FE of 39.1% at -1.36 V ( vs. RHE) and 34.7% at -1.50 V ( vs. RHE). However, Sn-rich Cu 6 Sn 5 /CNFs produced HCOO - with the FE of 58.6% at -2.31 V ( vs. RHE). This study suggests the methodology for bimetallic catalyst design and steering the CO 2 RR pathway by controlling the active sites of Cu-Sn alloys.

Fabricating nanoscale metal carbides is a great challenge due to them having higher Gibbs free energy of formation (Δ G° ) values than other metal compounds; additionally, these carbides have harsh calcination conditions, in which metal oxidation is preferred in the atmosphere. Herein, we report oxocarbon-mediated calcination for the predictive synthesis of nanoscale metal carbides. The thermochemical oxocarbon equilibrium of CO-CO 2 reactions was utilized to control the selective redox reactions in multiatomic systems of Mo-C-O, contributing to the phase-forming and structuring of Mo compounds. By harnessing the thermodynamically predicted processing window, we controlled a wide range of Mo phases (MoO 2 , α-MoC 1- x , and β-Mo 2 C) and nanostructures (nanoparticle, spike, stain, and core/shell) in the Mo compounds/C nanofibers. By inducing simultaneous reactions of C-O (selective C combustion) and Mo-C (Mo carbide formation) in the nanofibers, Mo diffusion was controlled in C nanofibers, acting as a template for the nucleation and growth of Mo carbides and resulting in precise control of the phases and structures of Mo compounds. The formation mechanism of nanostructured Mo carbides was elucidated according to the CO fractions of CO-CO 2 calcination. Moreover, tungsten (W) and niobium (Nb) carbides/C nanofibers have been successfully synthesized by CO-CO 2 calcination. We constructed the thermodynamic map for the predictive synthesis of transition metal carbides to provide universal guideline via thermochemical oxocarbon equilibrium. We revealed that our thermochemical oxocarbon-mediated gas-solid reaction enabled the structure and phase control of nanoscale transition metal compounds to optimize the material-property relationship accordingly.

Purpose: Lithotomy position has been widely used in the various urologic surgery. Occasionally sensory and motor problems of the lower extremities are occurred due to the lithotomy position and these deficits may be related with sciatic nerve injury (SNI). Inflammatory process is a factor to induce functional impairment after SNI. Therefore, we evaluated the role of adenosine A2A receptor agonists, polydeoxyribonucleotide (PDRN) showing anti-inflammatory effect on locomotor function following SNI in rats., Methods: Sciatic nerve was compressed with surgical clips for 1 minute after exposing of right sciatic nerve. After 3 days of SNI, PDRN (2, 4, and 8 mg/kg) was applied to the damaged area of sciatic nerve once daily for 10 days. Walking track analysis was conducted for locomotor function and plantar test was performed for thermal pain sensitivity. Level of cyclic adenosine-3´,5´-monophosphate (cAMP) were measured using enzyme-linked immunosorbent assay. Western blot analysis was performed for tumor necrosis factor (TNF)-α, interleukin (IL)-1β, cAMP response element binding protein (CREP), vascular endothelial growth factor (VEGF). Immunofluorescence for neurofilament was also conducted., Results: Locomotor function was decreased and thermal pain sensitivity was increased by SNI. SNI enhanced proinflammatory cytokines' production, such as TNF-α and IL-1β, while suppressed CREP phosphorylation and cAMP level. SNI also reduced the expression of VEGF and neurofilaments. However, treatment with PDRN inhibited proinflammatory cytokines' production and upregulated CREP phosphorylation and cAMP expression. PDRN also enhanced the expression of VEGF and neurofilaments. As a result, PDRN improved locomotor function and alleviated thermal hyperalgesia after SNI., Conclusion: PDRN has shown potential to be used as an effective treatment for neuropathic pain.

Bioelectronic devices that offer real-time measurements, biological signal processing, and continuous monitoring while maintaining stable performance are in high demand. The materials used in organic electrochemical transistors (OECTs) demonstrate high transconductance (GM) and excellent biocompatibility, making them suitable for bioelectronics in a biological environment. However, ion migration in OECTs induces a delayed response time and low cut-off frequency, and the adverse biological environment causes OECT durability problems. Herein, we present OECTs with a faster response time and improved durability, made possible by using a nanofiber mat channel of a conventional OECT structure. Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)/polyacrylamide (PAAm) nanofiber mat channel OECTs are fabricated and subjected to various durability tests for the first time based on continuous measurements and mechanical stability assessments. The results indicate that the nanofiber mat channel OECTs have a faster response time and longer life spans compared to those of film channel OECTs. The improvements can be attributed to the increased surface area and fibrous structure of the nanofiber mat channel. Furthermore, the hydrogel helps to maintain the structure of the nanofiber, facilitates material exchange, and eliminates the need for a crosslinker.

The importance of developing a hardmask with excellent performance, and physical and chemical properties to utilize in long-term etching is spotlighted due to the acceleration of development in high-density semiconductors. To develop such a hardmask, amorphous carbon hardmasks doped with various concentrations of N were fabricated with a DC magnetron sputtering system using varying inert gas (Ar to N 2 ) ratios. In contrast to the expectation that doped nitrogen would block the permeation of fluorine and improve the etch resistance, as the nitrogen concentration increased, the selectivity of the doped amorphous carbon films decreased. To understand this degradation with increasing nitrogen concentration, systematic X-ray photoelectron spectroscopy (XPS), radial distribution function (RDF), and X-ray reflectometry (XRR) analyses were conducted. In this study, we found that as the amount of nitrogen increased, the density of the film decreased, and the amount of pyridinic and pyrrolic nitrogen bonds with low formation energy increased. In contrast, based on time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis of etched nitrogen-doped amorphous carbon films, the penetration depth of fluorine ions from the etchant decreased as the amount of nitrogen increased. Therefore, in order to develop an excellent hardmask using amorphous carbon, it is important to increase the density of the film and the nitrogen concentration in the film while lowering the ratio of pyrrolic N to pyridinic N, i.e. , increasing the ratio of graphitic N., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

With recent rapid increases in Cu resistivity, RC delay has become an important issue again. Co, which has a low electron mean free path, is being studied as beyond Cu metal and is expected to minimize this increase in resistivity. However, extrinsic time-dependent dielectric breakdown has been reported for Co interconnects. Therefore, it is necessary to apply a diffusion barrier, such as the Ta/TaN system, to increase interconnect lifetimes. In addition, an ultrathin diffusion barrier should be formed to occupy as little area as possible. This study provides a thermodynamic design for a self-forming barrier that provides reliability with Co interconnects. Since Cr, Mn, Sn, and Zn dopants exhibited surface diffusion or interfacial stable phases, the model constituted an effective alloy design. In the Co-Cr alloy, Cr diffused into the dielectric interface and reacted with oxygen to provide a self-forming diffusion barrier comprising Cr 2 O 3 . In a breakdown voltage test, the Co-Cr alloy showed a breakdown voltage more than 200% higher than that of pure Co. The 1.2 nm ultrathin Cr 2 O 3 self-forming barrier will replace the current bilayer barrier system and contribute greatly to lowering the RC delay. It will realize high-performance Co interconnects with robust reliability in the future., (© 2022. The Author(s).)

A novel combination of machine learning algorithms is proposed for the differentiation of distinct spectra in a large electron energy loss spectroscopy spectrum image (EELS-SI) dataset. For clustering of the EEL spectra including similar fine structures in an efficient space, linear and nonlinear dimensionality reduction methods are used to project the EEL spectra onto a low-dimensional space. Then, a density-based clustering algorithm is applied to distinguish the meaningful data clusters. By applying this strategy to various experimental EELS-SI datasets, differentiation of several groups of EEL spectra representing specific fine structures was achieved. It is possible to investigate particular fine structures by averaging all of the spectra in each cluster. Also, the spatial distributions of each cluster in the scanning regions can be observed, which enables investigation of the locations of different fine structures in materials. This method does not require any prior knowledge, i.e., it is a data-driven analysis; therefore, it can be applied to any hyperspectral image., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Polymorph conversion of transition metal dichalcogenides (TMDs) offers intriguing material phenomena that can be applied for tuning the intrinsic properties of 2D materials. In general, group VIB TMDs can have thermodynamically stable 2H phases and metastable 1T/T' phases. Herein, we report key principles to apply carbon monoxide (CO)-based gas-solid reactions for a universal polymorph conversion of group VIB TMDs without forming undesirable compounds. We found that the process conditions are strongly dependent on the reaction chemical potential of cations in the TMDs, which can be predicted by thermodynamic calculations, and that polymorphic conversion is triggered by S vacancy (V S ) formation. Furthermore, we conducted DFT calculations for the reaction barriers of V S formation and S diffusion to reveal the polymorph conversion mechanism of WS 2 and compared it with that of MoS 2 . We believe that phase engineering 2D materials via thermodynamically designed gas-solid reactions could be functionally used to achieve defect-related nanomaterials.

The electrochemical CO 2 reduction reaction (CO 2 RR), which converts CO 2 into value-added feedstocks and renewable fuels, has been increasingly studied as a next-generation energy and environmental solution. Here, we report that single-atom metal sites distributed around active materials can enhance the CO 2 RR performance by controlling the Lewis acidity-based local CO 2 concentration. By utilizing the oxidation Gibbs free energy difference between silver (Ag), zinc (Zn), and carbon (C), we can produce Ag nanoparticle-embedded carbon nanofibers (CNFs) where Zn is atomically dispersed by a one-pot, self-forming thermal calcination process. The CO 2 RR performance of AgZn-CNF was investigated by a flow cell with a gas diffusion electrode (GDE). Compared to Ag-CNFs without Zn species (53% at -0.85 V vs. RHE), the faradaic efficiency (FE) of carbon monoxide (CO) was approximately 20% higher in AgZn-CNF (75% at -0.82 V vs. RHE) with 1 M KOH electrolyte., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Electronic skins (e-skins)-electronic sensors mechanically compliant to human skin-have long been developed as an ideal electronic platform for noninvasive human health monitoring. For reliable physical health monitoring, the interface between the e-skin and human skin must be conformal and intact consistently. However, conventional e-skins cannot perfectly permeate sweat in normal day-to-day activities, resulting in degradation of the intimate interface over time and impeding stable physical sensing. Here, we present a sweat pore-inspired perforated e-skin that can effectively suppress sweat accumulation and allow inorganic sensors to obtain physical health information without malfunctioning. The auxetic dumbbell through-hole patterns in perforated e-skins lead to synergistic effects on physical properties including mechanical reliability, conformability, areal mass density, and adhesion to the skin. The perforated e-skin allows one to laminate onto the skin with consistent homeostasis, enabling multiple inorganic sensors on the skin to reliably monitor the wearer's health over a period of weeks., (Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).)

For steady electroconversion to value-added chemical products with high efficiency, electrocatalyst reconstruction during electrochemical reactions is a critical issue in catalyst design strategies. Here, we report a reconstruction-immunized catalyst system in which Cu nanoparticles are protected by a quasi-graphitic C shell. This C shell epitaxially grew on Cu with quasi-graphitic bonding via a gas-solid reaction governed by the CO (g) - CO 2 (g) - C (s) equilibrium. The quasi-graphitic C shell-coated Cu was stable during the CO 2 reduction reaction and provided a platform for rational material design. C 2+ product selectivity could be additionally improved by doping p-block elements. These elements modulated the electronic structure of the Cu surface and its binding properties, which can affect the intermediate binding and CO dimerization barrier. B-modified Cu attained a 68.1% Faradaic efficiency for C 2 H 4 at -0.55 V (vs RHE) and a C 2 H 4 cathodic power conversion efficiency of 44.0%. In the case of N-modified Cu, an improved C 2+ selectivity of 82.3% at a partial current density of 329.2 mA/cm 2 was acquired. Quasi-graphitic C shells, which enable surface stabilization and inner element doping, can realize stable CO 2 -to-C 2 H 4 conversion over 180 h and allow practical application of electrocatalysts for renewable energy conversion.

Organic neuromorphic computing/sensing platforms are a promising concept for local monitoring and processing of biological signals in real time. Neuromorphic devices and sensors with low conductance for low power consumption and high conductance for low-impedance sensing are desired. However, it has been a struggle to find materials and fabrication methods that satisfy both of these properties simultaneously in a single substrate. Here, nanofiber channels with a self-formed ion-blocking layer are fabricated to create organic electrochemical transistors (OECTs) that can be tailored to achieve low-power neuromorphic computing and fast-response sensing by transferring different amounts of electrospun nanofibers to each device. With their nanofiber architecture, the OECTs exhibit a low switching energy of 113 fJ and operate within a wide bandwidth (cut-off frequency of 13.5 kHz), opening a new paradigm for energy-efficient neuromorphic computing/sensing platforms in a biological environment without the leakage of personal information., Competing Interests: The authors declare no conflict of interest., (© 2021 The Authors. Advanced Science published by Wiley‐VCH GmbH.)

Biodegradable electronics are disposable green devices whose constituents decompose into harmless byproducts, leaving no residual waste and minimally invasive medical implants requiring no removal surgery. Stretchable and flexible form factors are essential in biointegrated electronic applications for conformal integration with soft and expandable skins, tissues, and organs. Here a fully biodegradable MgZnCa metallic glass (MG) film is proposed for intrinsically stretchable electrodes with a high yield limit exploiting the advantages of amorphous phases with no crystalline defects. The irregular dissolution behavior of this amorphous alloy regarding electrical conductivity and morphology is investigated in aqueous solutions with different ion species. The MgZnCa MG nanofilm shows high elastic strain (≈2.6% in the nano-tensile test) and offers enhanced stretchability (≈115% when combined with serpentine geometry). The fatigue resistance in repeatable stretching also improves owing to the wide range of the elastic strain limit. Electronic components including the capacitor, inductor, diode, and transistor using the MgZnCa MG electrode support its integrability to transient electronic devices. The biodegradable triboelectric nanogenerator of MgZnCa MG operates stably over 50 000 cycles and its fatigue resistant applications in mechanical energy harvesting are verified. In vitro cell toxicity and in vivo inflammation tests demonstrate the biocompatibility in biointegrated use., Competing Interests: The authors declare no conflict of interest., (© 2021 The Authors. Advanced Science published by Wiley‐VCH GmbH.)

The oxygen evolution reaction (OER) is the key reaction in water splitting systems, but compared with the hydrogen evolution reaction (HER), the OER exhibits slow reaction kinetics. In this work, boron doping into nickel-iron layered double hydroxide (NiFe LDH) was evaluated for the enhancement of OER electrocatalytic activity. To fabricate boron-doped NiFe LDH (B:NiFe LDH), gaseous boronization, a gas-solid reaction between boron gas and NiFe LDH, was conducted at a relatively low temperature. Subsequently, catalyst activation was performed through electrochemical oxidation for maximization of boron doping and improved OER performance. As a result, it was possible to obtain a remarkably reduced overpotential of 229 mV at 10 mA cm -2 compared to that of pristine NiFe LDH (315 mV) due to the effect of facile charge-transfer resistance by boron doping and improved active sites by electrochemical oxidation., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

In response to the extensive utilization of ionic circuits, including in iontronics and wearable devices, a new method for fabricating a hydrogel-based ionic circuit on a polydimethylsiloxane (PDMS) microchip is reported. Prolonged UV/ozone oxidation combined with proper surface functionalizations and a novel microchip bonding method using thiol-epoxy click reaction enable the robust attachment of the photopolymerized hydrogel to the microchannel surface for eventual operation in electrolytes as an ionic circuit. The stretchable ionic diode constructed on the PDMS microchip shows a superior rectification ratio even under tensile stress and long-term storage stability. Furthermore, the combination of the ionic circuit and unique material properties of PDMS allows us to maximize the versatility and diversify the functionalities of the iontronic device, as demonstrated in a pressure-driven ionic switch and chip-integrated ionic regulator. Its iontronic signal transmission mimicking the excitatory and inhibitory synapses also evinces the potential of the hydrogel-based iontronics on the PDMS microchip as developed toward an aqueous neuromimetic information processor while opening up new opportunities for various bioinspired applications.

In this research, we report the rapid and reliable formation of high-performance nanoscale bilayer oxide dielectrics on silicon substrates via low-temperature deep ultraviolet (DUV) photoactivation. The optical analysis of sol-gel aluminum oxide films prepared at various concentrations reveals the processable film thickness with DUV photoactivation and its possible generalization to the formation of various metal oxide films on silicon substrates. The physicochemical and electrical characterizations confirm that DUV photoactivation accelerates the efficient formation of a highly dense aluminum oxide and aluminum silicate bilayer (17 nm) on heavily doped silicon at 150 °C within 5 min owing to the efficient thermal conduction on silicon, resulting in excellent dielectric properties in terms of low leakage current (∼10 -8 A/cm 2 at 1.0 MV/cm) and high areal capacitance (∼0.4 μF/cm 2 at 100 kHz) with narrow statistical distributions. Additionally, the sol-gel bilayer oxide dielectrics are successfully combined with a sol-gel indium-gallium-zinc oxide semiconductor via two successive DUV photoactivation cycles, leading to the efficient fabrication of solution-processed oxide thin-film transistors on silicon substrates with an operational voltage below 0.5 V. We expect that in combination with large-area printing, the bilayer oxide dielectrics are beneficial for large-area solution-based oxide electronics on silicon substrates, while DUV photoactivation can be applied to various types of solution-processed functional metal oxides such as phase-transition memories, ferroelectrics, photocatalysts, charge-transporting interlayers and passivation layers, etc. on silicon substrates.

The structural transformations of graphene defects have been extensively researched through aberration-corrected transmission electron microscopy (AC-TEM) and theoretical calculations. For a long time, a core concept in understanding the structural evolution of graphene defects has been the Stone-Thrower-Wales (STW)-type bond rotation. In this study, we show that undercoordinated atoms induce bond formation and breaking, with much lower energy barriers than the STW-type bond rotation. We refer to them as mediator atoms due to their mediating role in the breaking and forming of bonds. Here, we report the direct observation of mediator atoms in graphene defect structures using AC-TEM and annular dark-field scanning TEM (ADF-STEM) and explain their catalytic role by tight-binding molecular dynamics (TBMD) simulations and image simulations based on density functional theory (DFT) calculations. The study of mediator atoms will pave a new way for understanding not only defect transformation but also the growth mechanisms in two-dimensional materials., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution License 4.0 (CC BY).)

This study starts from the counterintuitive question of how we can render conventional stiff, nonstretchable, and even brittle materials sufficiently conformable to fully wrap curved surfaces, such as spheres, without failure. Here, we extend the geometrical design method of computational origami to wrapping. Our computational wrapping approach provides a robust and reliable method for fabricating conformal devices for arbitrary curved surfaces with a computationally designed nonpolyhedral developable net. This computer-aided design transforms two-dimensional (2D)-based materials, such as Si wafers and steel sheets, into various targeted conformal structures that can fully wrap desired 3D structures without fracture or severe plastic deformation. We further demonstrate that our computational wrapping approach enables a design platform that can transform conventional nonstretchable 2D-based devices, such as electroluminescent lighting and flexible batteries, into conformal 3D curved devices., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).)

To develop highly reliable flexible electronics, mechanical reliability during mechanical deformation such as repeated bending is an important issue. Bending test methodologies to estimate long-term reliability during repeated mechanical deformation are attracting substantial interest from related researchers and industry insiders. In this study, four representative bending test methodologies for testing flexible electronics are introduced: free arc bending test, variable radius bending test, sliding plate test, and variable angle test. Correct name and characteristics of each method are also explained. Furthermore, electrical reliability of Cu film on polymer substrate samples was investigated in each bending test method through in situ monitoring of electrical resistance. With different bending test methodologies, different electrical resistance changes were observed. Fatigue damages occurred at different areas. Obtained electrical reliability and failure modes were analyzed by observing crack morphologies.

Both high activity and mass production potential are important for bifunctional electrocatalysts for overall water splitting. Catalytic activity enhancement was demonstrated through the formation of CoS 2 nanoparticles with mono-phase and extremely porous structures. To fabricate porous structures at the nanometer scale, Co-based metal-organic frameworks (MOFs), namely a cobalt Prussian blue analogue (Co-PBA, Co 3 [Co(CN) 6 ] 2 ), was used as a porous template for the CoS 2 . Then, controlled sulfurization annealing converted the Co-PBA to mono-phase CoS 2 nanoparticles with ~ 4 nm pores, resulting in a large surface area of 915.6 m 2  g -1 . The electrocatalysts had high activity for overall water splitting, and the overpotentials of the oxygen evolution reaction and hydrogen evolution reaction under the operating conditions were 298 mV and -196 mV, respectively, at 10 mA cm -2 .

Controlled phase conversion in polymorphic transition metal dichalcogenides (TMDs) provides a new synthetic route for realizing tunable nanomaterials. Most conversion methods from the stable 2H to metastable 1T phase are limited to kinetically slow cation insertion into atomically thin layered TMDs for charge transfer from intercalated ions. Here, we report that anion extraction by the selective reaction between carbon monoxide (CO) and chalcogen atoms enables predictive and scalable TMD polymorph control. Sulfur vacancy, induced by anion extraction, is a key factor in molybdenum disulfide (MoS 2 ) polymorph conversion without cation insertion. Thermodynamic MoS 2 -CO-CO 2 ternary phase diagram offers a processing window for efficient sulfur vacancy formation with precisely controlled MoS 2 structures from single layer to multilayer. To utilize our efficient phase conversion, we synthesize vertically stacked 1T-MoS 2 layers in carbon nanofibers, which exhibit highly efficient hydrogen evolution reaction catalytic activity. Anion extraction induces the polymorph conversion of tungsten disulfide (WS 2 ) from 2H to 1T. This reveals that our method can be utilized as a general polymorph control platform. The versatility of the gas-solid reaction-based polymorphic control will enable the engineering of metastable phases in 2D TMDs for further applications.

While cracks are usually considered detrimental, crack generation can be harnessed for various applications, for example in ceramic materials, via directing crack propagation and crack opening. Here, we find that electron beam irradiation prompts a crack suppression phenomenon in a copper (Cu) thin film on a polyimide substrate, allowing for the control of crack formation in terms of both location and shape. Under tensile strain, cracks form on the unirradiated region of the Cu film whereas cracks are prevented on the irradiated region. We attribute this to the enhancement of the adhesion at the Cu-polyimide interface by electrons transmitted through the Cu film. Finally, we selectively form conductive regions in a Cu film on a polyimide substrate under tension and fabricate a strain-responsive organic light-emitting device.

As the technology of flexible electronics has remarkably advanced, the long-term reliability of flexible devices has attracted much attention, as it is an important factor for such devices in reaching real commercial viability. To guarantee the bending fatigue lifetime, the exact evaluation of bending strain and the change in electrical resistance is required. In this study, we investigated the bending strains of Cu thin films on flexible polyimide substrates with different thicknesses using monolayer and bilayer bending models and monitored the electrical resistance of the metal electrode during a bending fatigue test. For a thin metal electrode, the bending strain and fatigue lifetime were similar regardless of substrate thickness, but for a thick metal film, the fatigue lifetime was changed by different bending strains in the metal electrode according to substrate thickness. To obtain the exact bending strain distribution, we conducted a finite-element simulation and compared the bending strains of thin and thick metal structures. For thick metal electrodes, the real bending strain obtained from a bilayer model or simulation showed values much different from those from a simple monolayer model. This study can provide useful guidelines for developing highly reliable flexible electronics.

As biological signals are mainly based on ion transport, the differences in signal carriers have become a major issue for the intimate communication between electrical devices and biological areas. In this respect, an ionic device which can directly interpret ionic signals from biological systems needs to be designed. Particularly, it is also required to amplify the ionic signals for effective signal processing, since the amount of ions acquired from biological systems is very small. Here, we report the signal amplification in ionic systems as well as sensing through the modified design of polyelectrolyte hydrogel-based ionic diodes. By designing an open-junction structure, ionic signals from the external environment can be directly transmitted to an ionic diode. Moreover, the minute ionic signals injected into the devices can also be amplified to a large amount of ions. The signal transduction mechanism of the ion-to-ion amplification is suggested and clearly verified by revealing the generation of breakdown ionic currents during an ion injection. Subsequently, various methods for enhancing the amplification are suggested., Competing Interests: The authors declare no conflict of interest.

Amorphous oxide semiconductor (AOS)-based Schottky diodes have been utilized for selectors in crossbar array memories to improve cell-to-cell uniformity with a low-temperature process. However, thermal instability at interfaces between the AOSs and metal electrodes can be a critical issue for the implementation of reliable Schottky diodes. Under post-fabrication annealing, an excessive redox reaction at the ohmic interface can affect the bulk region of the AOSs, inducing an electrical breakdown of the device. Additionally, structural relaxation (SR) of the AOSs can increase the doping concentration at the Schottky interface, which results in a degradation of the rectifying performance. Here, we improved the thermal stability at AOS/metal interfaces by regulating the oxygen vacancy (V O ) concentration at both sides of the contact. For a stable quasi-ohmic contact, a Cu-Mn alloy was introduced instead of a single component reactive metal. As Mn only takes up O in amorphous In-Ga-Zn-O (a-IGZO), excessive V O generation in bulk region of a-IGZO can be prevented. At the Schottky interfaces, the barrier characteristics were not degraded by thermal annealing as the Ga concentration in a-IGZO increased. Ga not only reduces the inherent V O concentration but also retards SR, thereby suppressing tunneling conduction and enhancing the thermal stability of devices.

Melanin is major cause of dark skin, which is regarded as social status in eastern Asia. As a result, researchers in cosmetic industries are developing skin whitening agents. Melanin can be decolorized by many oxidative enzymes. Laccase (CueO) from Escherichia coli and dye-decolorizing peroxidase (DyP) from Bacillus subtilis were merged with the dockerin domain of endoglucanase B from Clostridium cellulovorans. Scaffoldin has great potential to exert structural benefits that enable complementary enzyme effects. The carbohydrate binding module (CBM) in scaffoldin was replaced with the melanin binding peptide (MBP) to increase melanin binding and thereby enhance melanin degradation. The modified scaffoldin exhibits a nearly 64% increase in specific binding to melanin over that of the native scaffoldin. Laccase was used to degrade melanin via the production of hydrogen peroxide, which produced synergistic activity with peroxidase. The activity of the optimized complex was approximately 6.4-fold greater than that of laccase alone. This enzyme complex can also reduce the number of melanin granules in corneocytes. Based on these results, a recombinant enzyme complex is suitable for use in melanin degradation by next generation whitening agents in the skin cosmetics industry., (Copyright © 2019 Elsevier B.V. All rights reserved.)

According to the recent growth in interest of human-friendly devices, soft conductors, which are conductive materials with an inherent compliance, must have a low electrical strain sensitivity under large deformation conditions, environmental stability in water, and reliability even for complex and repeated deformation, as well as nontoxic characteristics. In this study, we fabricated a poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)/polyacrylamide nanoweb that satisfies all of the above requirements through a web microstructure with entangled conductive nanofibers. Since the web structure can be deformed through structural alignment, the conductive path is stably maintained during deformation, which makes it highly conductive, electrically stable, and electrically strain insensitive. The tangled nanofibers are composed of PEDOT:PSS as a conductive component and polyacrylamide as a binding material, so it is nontoxic and has the soft properties of the material itself, which can withstand large deformations. Additionally, the material has a good electrical stability against repeated deformation so that the resistance increased by only 13% after a 50% strain was repeated 1000 times. Notably, electrical instabilities such as noise and hysteresis were not evident during the repeated deformations. Finally, the nanoweb has excellent swelling resistance and maintains its mechanical and electrical characteristics in water.

Taurine is a biologically and physiologically valuable food additive. However, commercial taurine production mainly relies on environmentally harmful chemical synthesis. Herein, for the first time in bacteria, we attempted to produce taurine in metabolically engineered Corynebacterium glutamicum. The taurine-producing strain was developed by introducing cs, cdo1, and csad genes. Interestingly, while the control strain could not produce taurine, the engineered strains successfully produced taurine via the newly introduced metabolic pathway. Furthermore, we investigated the effect of a deletion strain of the transcriptional repressor McbR gene on taurine production. As a result, sulfur accumulation and l-cysteine biosynthesis were reinforced by the McbR deletion strain, which further increased the taurine production by 2.3-fold. Taurine production of the final engineered strain Tau11 was higher than in other previously reported strains. This study demonstrated a potential approach for eco-friendly biosynthesis as an alternative to the chemical synthesis of a food additive.

Zn-porphyrin is a promising organic photosensitizer in various fields including solar cells, interface and biomedical research, but the biosynthesis study has been limited, probably due to the difficulty of understanding complex biosynthesis pathways. In this study, we developed a Corynebacterium glutamicum platform strain for the biosynthesis of Zn-coproporphyrin III (Zn-CP III), in which the heme biosynthesis pathway was efficiently upregulated. The pathway was activated and reinforced by strong promoter-induced expression of hemA M (encoding mutated glutamyl-tRNA reductase) and hemL (encoding glutamate-1-semialdehyde aminotransferase) genes. This engineered strain produced 33.54 ± 3.44 mg/l of Zn-CP III, while the control strain produced none. For efficient global regulation of the complex pathway, the dtxR gene encoding the transcriptional regulator diphtheria toxin repressor (DtxR) was first overexpressed in C. glutamicum with hemA M and hemL genes, and its combinatorial expression was improved by using effective genetic tools. This engineered strain biosynthesized 68.31 ± 2.15 mg/l of Zn-CP III. Finally, fed-batch fermentation allowed for the production of 132.09 mg/l of Zn-CP III. This titer represents the highest in bacterial production of Zn-CP III reported to date, to our knowledge. This study demonstrates that engineered C. glutamicum can be a robust biotechnological model for the production of photosensitizer Zn-porphyrin.

Precise control of the oxidation state of transition-metal oxides, such as copper, is important for high selectivity of CO 2 reduction in an aqueous condition to compete with the reduction of water. The phase of copper oxide nanofibers was controlled by predictive synthesis, which controls the nanoscale gas-solid reaction by considering thermodynamics and kinetics. The driving force of the phase transformation between the different oxidation states of copper oxide is calculated by comparing the Gibbs free energy of each of the oxidation states. From the calculation, the kinetically processable window for the fabrication of Cu 2 O in which monophase Cu 2 O can be fabricated in a reasonable reaction time scale is discovered. Herein, we report the monophase Cu 2 O nanofiber photocathode, which photoelectrochemically converted CO 2 into methanol with over 90% selectivity in an aqueous electrolyte, and a hierarchical structure is developed to optimize the photoactivity and stability of the electrode. Our work suggests a rational design of the calcination strategy for precisely controlling the oxidation states of transition metals that can be applied to various applications in which the phase of the materials plays an important role.

Expansin act by loosening hydrogen bonds in densely packed polysaccharides. This work characterizes the biological functions of expansin in the gelling and degradation of algal polysaccharides. In this study, the bacterial expansin BpEX from Bacillus pumilus was fused with the dockerin module of a cellulosome system for assembly with agarolytic complexes. The assembly of chimeric expansin caused an indicative enhancement in agarase activity. The enzymatic activities on agar substrate and natural biomass were 3.7-fold and 3.3-fold higher respectively than that of agarase as a single enzyme. To validate the effect on the agar degradation, the regulation potential of parameters related to gel rheology by bacterial expansin was experimentally investigated to indicate that the bacterial expansin lowered the gelling temperature and viscosity of agar. Thus, these results demonstrated the possibility of advancing more efficient strategies for utilizing agar as oligo sugar source in the biorefinery field that uses marine biomass as feedstocks.

In the practice of converting red algae biomass into biofuel or valuable biomaterials, the critical step is the decomposition process of the agarose to give fermentable monomeric sugars. In this study, we selected three enzymes such as agarase, carrageenase and neoagarobiose hydrolase to inducible the simultaneous hydrolysis of the major substrates such as agar and carrageenan constituting the pretreated red algae, and expressed the chimeric enzymes and formed a complexes through optimization of addition ratio. As a result, hydrolysis by enzyme complexes showed a maximum sugar release of 679 mg L -1 with 67.9% saccharification yield from G. verrucosa natural substrate. The difference in the reducing sugar by the enzyme complexes was 3.6-fold higher than that of the monomer enzyme (cAgaB yield 188.6 mg L -1 ). The synergistic effect of producing sugars from red algae biomass through these enzyme complexes can be a very important biological tools aimed at bioenergy production., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

p-Type SnO thin films were deposited on a Si substrate by a cosputtering process using ceramic SnO and metal Sn targets at room temperature without adding oxygen. By varying the dc sputtering power applied to the Sn target while maintaining a constant radio frequency power to the SnO target, the Sn/O ratio varied from 56:44 to 74:26 at the as-deposited state. After thermal annealing at 180 °C for 25 min under air atmosphere using a microwave annealing system, the films were crystallized into tetragonal SnO when the Sn/O ratio increased from 44:56 to 57:43. Notably, the metallic Sn remained when the Sn/O ratio was higher than 55:45 at an annealed state. When the ratio was lower than 55:45 at the annealed state, the incorporated Sn fully oxidized to SnO, making the films useful p-type semiconductors, whereas the films became metallic conductors at higher Sn/O ratios. At the Sn/O ratio of 55:45 at the annealed state, the film showed the highest Hall mobility of 8.8 cm 2 V -1 s -1 and a hole concentration of 5.4 × 10 18 cm -3 . Interestingly, the electrical conduction behavior showed trap-mediated hopping when the Sn metal was cosputtered, whereas the single SnO film showed regular band conduction behavior. The residual stress effect could interpret such property variation originated from the sputtering power and postoxidation-induced volumetric effects. This report makes a critical contribution to the in-depth understanding of the composition-structure-property relationship of this technically important thin film material.

Despite the high theoretical specific capacity of Si, commercial Li-ion batteries (LIBs) based on Si are still not feasible because of unsatisfactory cycling stability. Herein, amorphous Si (a-Si)-coated nanocrystalline Si (nc-Si) formed by versatile radio frequency (RF) sputtering systems is proposed as a promising anode material for LIBs. Compared to uncoated nc-Si (retention of 0.6% and Coulombic efficiency (CE) of 79.7%), the a-Si-coated nc-Si (nc-Si@a-Si) anodes show greatly improved cycling retention (C 50th /C first ) of ∼50% and a first CE of 86.6%. From the ex situ investigation with electrochemical impedance spectroscopy (EIS) and cracked morphology during cycling, the a-Si layer was found to be highly effective at protecting the surface of the nc-Si from the formation of solid-state electrolyte interphases (SEI) and to dissipate the mechanical stress upon de/lithiation due to the high fracture toughness.

Saccharomyces cerevisiae is used for edible purposes, such as human food or as an animal feed supplement. Fatty acids are also beneficial as feed supplements, but S. cerevisiae produces small amounts of fatty acids. In this study, we enhanced fatty acid production of S. cerevisiae by overexpressing acetyl-CoA carboxylase, thioesterase, and malic enzyme associated with fatty acid metabolism. The enhanced strain pAMT showed 2.4-fold higher fatty acids than the wild-type strain. To further increase the fatty acids, various nitrogen sources were analyzed and calcium nitrate was selected as an optimal nitrogen source for fatty acid production. By concentration optimization, 672 mg/L of fatty acids was produced, which was 4.7-fold higher than wild-type strain. These results complement the low level fatty acid production and make it possible to obtain the benefits of fatty acids as an animal feed supplement while, simultaneously, maintaining the advantages of S. cerevisiae.

Dimethyl itaconate is an important raw material for copolymerization, but it is not synthesized from itaconic acid by organisms. Moreover, Corynebacterium glutamicum is used as an important industrial host for the production of organic acids, but it does not metabolize itaconic acid. Therefore, the biosynthetic route toward dimethyl itaconate from itaconic acid is highly needed. In this study, a biological procedure for dimethyl itaconate production is developed from rice wine waste-derived itaconic acid using the engineered C. glutamicum strain. The first step is to investigate the effect of the co-overexpression of the codon-optimized cis-aconitic acid decarboxylase (CadA*) and a transcriptional regulator of genes involved in acetic acid metabolism (RamA) on itaconic acid production. The second step is to convert itaconic acid into dimethyl itaconate by lipase-catalyzed esterification. The CadA* and RamA-overexpressing CG4 strain increases the itaconic acid concentration under N-starvation with glucose and acetic acid compared with the concentration produced in the base mCGXII medium with glucose. Furthermore, the rice wine waste-derived itaconic acid is successfully converted into dimethyl itaconate using lipase from Rhizomucor miehei and a methanol substrate. This study is the first trial for bio-based production of dimethyl itaconate from rice wine waste-derived itaconic acid., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Vapor phase carbon (C)-reduction-based syntheses of C nanotubes and graphene, which are highly functional solid C nanomaterials, have received extensive attention in the field of materials science. This study suggests a revolutionary method for precisely controlling the C structures by oxidizing solid C nanomaterials into gaseous products in the opposite manner of the conventional approach. This gaseous nanocarving enables the modulation of inherent metal assembly in metal/C hybrid nanomaterials because of the promoted C oxidation at the metal/C interface, which produces inner pores inside C nanomaterials. This phenomenon is revealed by investigating the aspects of structure formation with selective C oxidation in the metal/C nanofibers, and density functional theory calculation. Interestingly, the tendency of C oxidation and calculated oxygen binding energy at the metal surface plane is coincident with the order Co > Ni > Cu > Pt. The customizable control of the structural factors of metal/C nanomaterials through thermodynamic-calculation-derived processing parameters is reported for the first time in this work. This approach can open a new class of gas-solid reaction-based synthetic routes that dramatically broaden the structure-design range of metal/C hybrid nanomaterials. It represents an advancement toward overcoming the limitations of intrinsic activities in various applications., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

l-Cysteine is a valuable sulfur-containing amino acid widely used as a nutrition supplement in industrial food production, agriculture, and animal feed. However, this amino acid is mostly produced by acid hydrolysis and extraction from human or animal hairs. In this study, we constructed recombinant Corynebacterium glutamicum strains that overexpress combinatorial genes for l-cysteine production. The aims of this work were to investigate the effect of the combined overexpression of serine acetyltransferase (CysE), O-acetylserine sulfhydrylase (CysK), and the transcriptional regulator CysR on l-cysteine production. The CysR-overexpressing strain accumulated approximately 2.7-fold more intracellular sulfide than the control strain (empty pMT-tac vector). Moreover, in the resulting CysEKR recombinant strain, combinatorial overexpression of genes involved in l-cysteine production successfully enhanced its production by approximately 3.0-fold relative to that in the control strain. This study demonstrates a biotechnological model for the production of animal feed supplements such as l-cysteine using metabolically engineered C. glutamicum.

Vertical stacking and lateral growth of molybdenum disulfide (MoS 2 ) are controlled with remarkable precision, and MoS 2 nanotubes are directly converted from nanofibers. Predictive synthesis is enabled by identifying the specific thermodynamic region where the Boudouard reaction becomes favored. It reveals how the chemical potential of each species in the MoSCO system can predict phase behaviors., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Low-temperature-processed perovskite solar cells (PSCs), especially those fabricated on flexible substrates, exhibit device performance that is worse than that of high-temperature-processed PSCs. One of the main reasons for the inferior performance of low-temperature-processed PSCs is the loss of photogenerated electrons in the electron collection layer (ECL) or related interfaces, i.e., indium tin oxide/ECL and ECL/perovskite. Here, we report that tailoring of the energy level and electron transporting ability in oxide ECLs using Zn2SnO4 nanoparticles and quantum dots notably minimizes the loss of photogenerated electrons in the low-temperature-fabricated flexible PSC. The proposed ECL with methylammonium lead halide [MAPb(I0.9Br0.1)3] leads to fabrication of significantly improved flexible PSCs with steady-state power conversion efficiency of 16.0% under AM 1.5G illumination of 100 mW cm(-2) intensity. These results provide an effective method for fabricating high-performance, low-temperature solution-processed flexible PSCs.

We devised anodized aluminium oxide (AAO) frame-supported polyelectrolytic ion-exchange membranes for the application of electrical power generation systems where salinity differences are present. A series of polyelectrolytic AAO membranes (PAMs) were fabricated as a function of concentration of monomers and cross-linkers. Of the ion-selective PAMs as made, the membranes from the most concentrated monomers and cross-linkers, C-PAM100 and A-PAM100, showed the highest area resistances and permselectivities (the resistances were 4.9 and 2.9 Ω · cm(2), the permseletivities for C-PAM100 and A-PAM100 were 99 and 89%, respectively). The measured resistances and permselectivities allowed the power density to be estimated for C-PAM100 and A-PAM100, 3.5 W/m(2), and experimentally obtained power density using a reverse electrodialysis (RED) stack was 17.3 mW/m(2). In addition, we investigated the influence of an AAO framework on a membrane resistance by comparing the PAMs with polyelectrolyte-stuffed capillaries, revealing that the resistance of the PAM has plenty of potential to be further reduced by optimizing the AAO pore spaces.

Unlabelled: Understanding the mechanism of the strain-dependent conductivity change in polymers in stretched conditions is important. We observed a strain-induced growth of the conductive regions of, Pedot: PSS films, induced by a coalescence of conductive PEDOT-rich cores. This growth due to coalescence leads to a gradual decrease in the electrical resistivity up to 95%, independent of the thickness of the, Pedot: PSS films. The primary mechanism for the evolution of the PEDOT-rich cores proceeds by the cores growing larger as they consuming relatively smaller cores. This process is caused by a strain-induced local rearrangement of PEDOT segments in the vicinity of PSS shells around the cores and also changes the chemical environment in PEDOT, induced by the electron-withdrawing effects around the PEDOT chains. The strain-induced growth mechanism is beneficial to understanding the phenomenon of polymeric chain rearrangement in mechanical deformation and to modulating the electrical conductivity for practical applications.

Organogel-based stretchable electronic conductors exhibit electrical conduction even under a large stretching deformation of 300% without electrochemical reactions at DC voltages. The resistance change with stretching is almost strain-insensitive up to 50% strain and it remains at each deformation up to 1000 fatigue cycle. The polymeric conductive paths of, Pedot: PSS are well preserved during the mechanical deformation., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The novel discovery of a current-induced transition from insulator to metal in the crystalline phase of Ge2Sb2Te5 and GeSb4Te7 have been studied by means of a model using line-patterned samples. The resistivity of cubic phase Ge-Sb-Te compound was reduced by an electrical current (~1 MA/cm(2)), and the final resistivity was determined based on the stress current density, regardless of the initial resistivity and temperature, which indicates that the conductivity of Ge-Sb-Te compound can be modulated by an electrical current. The minimum resistivity of Ge-Sb-Te materials can be achieved at high kinetic rates by applying an electrical current, and the material properties change from insulating to metallic behavior without a phase transition. The current-induced metal transition is more effective in GeSb4Te7 than Ge2Sb2Te5, which depends on the intrinsic vacancy of materials. Electromigration, which is the migration of atoms induced by a momentum transfer from charge carriers, can easily promote the rearrangement of vacancies in the cubic phase of Ge-Sb-Te compound. This behavior differs significantly from thermal annealing, which accompanies a phase transition to the hexagonal phase. This result suggests a new pathway for modulating the electrical conductivity and material properties of chalcogenide materials by applying an electrical current.

Achilles tendinopathy is a common degenerative condition without a definitive treatment. An adequate chronic animal model of Achilles tendinopathy has not yet been developed. The purpose of this study was to evaluate the individual and combined effects of dry needling and treadmill running on the Achilles tendon of rats. Percutaneous dry needling, designed to physically replicate microrupture of collagen fibers in overloaded tendons, was performed on the right Achilles tendon of 80 Sprague-Dawley rats. The rats were randomly divided into two groups: a treadmill group, which included rats that underwent daily uphill treadmill running (n = 40), and a cage group, which included rats that could move freely within their cages (n = 40). At the end of weeks 1 and 4, 20 rats from each group were sacrificed, and bilateral Achilles tendons were collected. The harvested tendons were subjected to mechanical testing and histological analysis. Dry needling induced histological and mechanical changes in the Achilles tendons at week 1, and the changes persisted at week 4. The needled Achilles tendons of the treadmill group tended to show more severe histological and mechanical changes than those of the cage group, although these differences were not statistically significant. Dry needling combined with free cage activity or treadmill running produced tendinopathy-like changes in rat Achilles tendons up to 4 weeks after injury. Dry needling is an easy procedure with a short induction period and a high success rate, suggesting it may have relevance in the design of an Achilles tendinopathy model.

Deformation behavior of the Ag nanowire flexible transparent electrode under bending strain is studied and results in a novel approach for highly reliable Ag nanowire network with mechanically welded junctions. Bending fatigue tests up to 500,000 cycles are used to evaluate the in situ resistance change while imposing fixed, uniform bending strain. In the initial stages of bending cycles, the thermally annealed Ag nanowire networks show a reduction in fractional resistance followed by a transient and steady-state increase at later stages of cycling. SEM analysis reveals that the initial reduction in resistance is caused by mechanical welding as a result of applied bending strain, and the increase in resistance at later stages of cycling is determined to be due to the failure at the thermally locked-in junctions. Based on the observations from this study, a new methodology for highly reliable Ag nanowire network is proposed: formation of Ag nanowire networks with no prior thermal annealing but localized junction formation through simple application of mechanical bending strain. The non-annealed, mechanically welded Ag nanowire network shows significantly enhanced cyclic reliability with essentially 0% increase in resistance due to effective formation of localized wire-to-wire contact., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Graphene-induced abnormal grain growth of Cu with a grain size of more than 1 mm(2) was observed on Cu-Ag alloy foil, and this phenomenon occurred only with graphene synthesis and only on the Cu-Ag alloy among various types of Cu foils.