Adhesion Strength Enhancement of Butyl Rubber and Aluminum Using Nanoscale Self-Assembled Monolayers of Various Silane Coupling Agents for Vibration Damping Plates.

In this paper, we enhance the adhesion strength of butyl rubber-based vibrational damping plates using nanoscale self-assembled monolayers of various silane coupling agents. The silane coupling agents used to chemically modify the plate's aluminum surface include 3-aminopropyltriethoxysilane (APTES), (3-glycidyloxypropyl) triethoxysilane (GPTES), 3-mercaptopropyltrimethoxysilane (MPTMS), and 3-(triethoxysilyl)propyl isocyanate (ICPTES). The modified surfaces were analyzed using Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS), and the enhancement in adhesion strength between the rubber and aluminum was estimated through T-Peel tests.

Intrinsically Stretchable Floating Gate Memory Transistors for Data Storage of Electronic Skin Devices.

To propel electronic skin (e-skin) to the next level by integrating artificial intelligence features with advanced sensory capabilities, it is imperative to develop stretchable memory device technology. A stretchable memory device for e-skin must offer, in particular, long-term data storage while ensuring the security of personal information under any type of deformation. However, despite the significance of these needs, technology related to stretchable memory devices remains in its infancy.

Autonomous self-healing supramolecular polymer transistors for skin electronics.

Skin-like field-effect transistors are key elements of bio-integrated devices for future user-interactive electronic-skin applications. Despite recent rapid developments in skin-like stretchable transistors, imparting self-healing ability while maintaining necessary electrical performance to these transistors remains a challenge. Herein, we describe a stretchable polymer transistor capable of autonomous self-healing.

Kinetically controlled metal-elastomer nanophases for environmentally resilient stretchable electronics.

Nanophase mixtures, leveraging the complementary strengths of each component, are vital for composites to overcome limitations posed by single elemental materials. Among these, metal-elastomer nanophases are particularly important, holding various practical applications for stretchable electronics. However, the methodology and understanding of nanophase mixing metals and elastomers are limited due to difficulties in blending caused by thermodynamic incompatibility.

Near-Infrared Transparent Transition-Metal-Doped Indium Oxide Thin-Film Heater for LiDAR.

The evolving need for all-weather light detection and ranging (LiDAR) sensors and cameras for autonomous vehicles, remote sensing surveillance, and space exploration has spurred the development of transparent heaters. While LiDAR photon sources have shifted from the visible to the near-infrared (NIR) range, the use of transparent conductive oxides (TCOs) for heaters leads to significant optical losses due to their high plasmonic absorption and reflection in the NIR range. Although different TCO compositions can be employed to preserve transparency and electrical conductivity in this range, the choice of dopants, their concentrations, and the underlying mechanisms remain largely unknown.

Kirigami Photopiezo Catalysts for Self-Sustainable Environment Remediation.

Photo(electro)-piezo catalysis has emerged as one of the most effective strategies for sustainable environmental remediation. While various (nano)materials have been investigated for enhancing the intrinsic properties related to the interfacial band structure, increasing the efficiency by integration of materials with rational design for stress-strain applications has not yet been considered. Herein, we introduce kirigami strain engineering to photopiezo catalysts for enhancing efficiency by increasing the magnitude of applied strain and density of bends.

Subaqueous 3D stem cell spheroid levitation culture using anti-gravity bioreactor based on sound wave superposition.

Background: Recently, various studies have revealed that 3D cell spheroids have several advantages over 2D cells in stem cell culture. However, conventional 3D spheroid culture methods have some disadvantages and limitations such as time required for spheroid formation and complexity of the experimental process. Here, we used acoustic levitation as cell culture platform to overcome the limitation of conventional 3D culture methods.

Subaqueous free-standing 3D cell culture system for ultrafast cell compaction, mechano-inductive immune control, and improving therapeutic angiogenesis.

Conventional 3D cell culture methods require a comprehensive complement in labor-intensive and time-consuming processes along with in vivo circumstantial mimicking. Here, we describe a subaqueous free-standing 3D cell culture (FS) device that can induce the omnidirectional environment and generate ultrafast human adipose-derived stem cells (hADSCs) that efficiently aggregate with compaction using acoustic pressure. The cell culture conditions were optimized using the FS device and identified the underlying molecular mechanisms.

Piezocatalytic 2D WS Nanosheets for Ultrasound-Triggered and Mitochondria-Targeted Piezodynamic Cancer Therapy Synergized with Energy Metabolism-Targeted Chemotherapy.

Piezoelectric nanomaterials that can generate reactive oxygen species (ROS) by piezoelectric polarization under an external mechanical force have emerged as an effective platform for cancer therapy. In this study, piezoelectric 2D WS nanosheets are functionalized with mitochondria-targeting triphenylphosphonium (TPP) for ultrasound (US)-triggered, mitochondria-targeted piezodynamic cancer therapy. In addition, a glycolysis inhibitor (FX11) that can inhibit cellular energy metabolism is loaded into TPP- and poly(ethylene glycol) (PEG)-conjugated WS nanosheet (TPEG-WS ) to potentiate its therapeutic efficacy.

Mechanically robust stretchable semiconductor metallization for skin-inspired organic transistors.

Despite recent remarkable advances in stretchable organic thin-film field-effect transistors (OTFTs), the development of stretchable metallization remains a challenge. Here, we report a highly stretchable and robust metallization on an elastomeric semiconductor film based on metal-elastic semiconductor intermixing. We found that vaporized silver (Ag) atom with higher diffusivity than other noble metals (Au and Cu) forms a continuous intermixing layer during thermal evaporation, enabling highly stretchable metallization.

Highly sensitive breath sensor based on sonochemically synthesized cobalt-doped zinc oxide spherical beads.

In this study, we introduce cobalt (Co)-doped zinc oxide (ZnO) spherical beads (SBs), synthesized using a sonochemical process, and their utilization for an acetone sensor that can be applied to an exhalation diagnostic device. The sonochemically synthezied Co-doped ZnO SBs were polycrystalline phases with sizes of several hundred nanometers formed by the aggregation of ZnO nanocrystals. As the Co doping concentration increased, the amount of substitutionally doped Co in the ZnO nanocrystals increased, and we observed that the fraction of Co in the Co-doped ZnO SBs increased while the fraction of oxygen vacancies decreased.

Antioxidant Triggered Metallic 1T' Phase Transformations of Chemically Exfoliated Tungsten Disulfide (WS ) Nanosheets.

Developing facile methods for inducing phase transformation between metallic and semiconducting 2D transition metal dichalcogenide (TMDC) materials is crucial toward leveraging their use in cutting-edge energy devices. Herein, 2H-to-1T' phase transformations in chemically exfoliated Tungsten Disulfide (WS ) nanosheet films, triggered by antioxidants toward highly conductive 2D TMDC electrode materials, are introduced. It is found that antioxidants cause residual LiO compounds to reduce to Li metal, subsequently inducing 1T' phase transformations in layered WS nanosheets, resulting in significantly enhanced conductivity across the overall films.

Self-Assembled 2D Networks of Metal Oxide Nanomaterials Enabling Sub-ppm Level Breathalyzers.

For extremely sensitive acetone sensors, here, we introduced an alcohol-assisted surfactant-free Langmuir-Blodgett process to rapidly assemble a single-layered two-dimensional (2D) network as a suitable percolation strategy of metal oxide semiconductor nanomaterials. The single-layered 2D network formation mechanism was investigated using zinc oxide (ZnO) nanobeads (NBs). Furthermore, the correlation between the response of the gas sensor and the average percolation number of the ZnO NBs, controlled by multi-stacking the 2D network, was investigated.

Phase-dependent gas sensitivity of MoS chemical sensors investigated with phase-locked MoS.

In the present study, phase-dependent gas sensitivities of MoS chemical sensors were examined. While 1T-phase MoS (1T-MoS) has shown better chemical sensitivity than has 2H-phase MoS (2H-MoS), the instability of the 1T phase has been hindering applications of 1T-MoS as chemical sensors. Here, the chemical sensitivity of MoS locked in its 1T phase by using a ZnO phase lock was investigated.

Optical Tunneling Mediated Sub-Skin-Depth High Emissivity Tungsten Radiators.

Tailoring the spectrum of thermal radiation at high temperatures is a central issue in the study of thermal radiation harnessed energy resources. Although bulk metals with periodic cavities incorporated into their surfaces provide high emissivity, they require a complicated micron metal etch, thereby precluding reliable, continuous operation. Here, we report thermally stable, highly emissive, ultrathin (<20 nm) tungsten (W) radiators that were prepared in a scalable and cost-effective route.

Scratch to sensitize: scratch-induced sensitivity enhancement in semiconductor thin-film sensors.

Semiconductor gas sensors are advantageous in miniaturization and can be used in a wide range of applications, yet consume large power due to high operating temperature. Here we demonstrated the ability of nanoscale scratches produced with mechanical abrasion to enhance the chemical sensitivity of thin-film-type semiconductor sensors. Well-aligned arrays of scratches parallel to the electrical current direction between the source and drain electrodes were made, using typical polishing machines with diamond suspensions, on semiconductor thin films produced with various deposition methods such as atomic layer deposition (ALD), sputtering, and the sol-gel technique.

A Disposable Photovoltaic Patch Controlling Cellular Microenvironment for Wound Healing.

Electrical stimulation (ES) is known to affect the wound healing process by modulating skin cell behaviors. However, the conventional clinical devices that can generate ES for promoting wound healing require patient hospitalization due to large-scale of the extracorporeal devices. Herein, we introduce a disposable photovoltaic patch that can be applied to skin wound sites to control cellular microenvironment for promoting wound healing by generating ES.

Microstructured void gratings for outcoupling deep-trap guided modes.

Breaking the total internal reflection far above a critical angle (i.e., outcoupling deep-trap guided modes) can dramatically improve existing light-emitting devices.

Graphene as a thin-film catalyst booster: graphene-catalyst interface plays a critical role.

Due to its extreme thinness, graphene can transmit some surface properties of its underlying substrate, a phenomenon referred to as graphene transparency. Here we demonstrate the application of the transparency of graphene as a protector of thin-film catalysts and a booster of their catalytic efficiency. The photocatalytic degradation of dye molecules by ZnO thin films was chosen as a model system.

Therapeutic Angiogenesis via Solar Cell-Facilitated Electrical Stimulation.

Cell therapy has been suggested as a treatment modality for ischemic diseases, but the poor survival and engraftment of implanted cells limit its therapeutic efficacy. To overcome such limitation, we used electrical stimulation (ES) derived from a wearable solar cell for inducing angiogenesis in ischemic tissue. ES enhanced the secretion of angiogenic growth factors and the migration of mesenchymal stem cells (MSCs), myoblasts, endothelial progenitor cells, and endothelial cells in vitro.

Stretchable Piezoelectric Substrate Providing Pulsatile Mechanoelectric Cues for Cardiomyogenic Differentiation of Mesenchymal Stem Cells.

Ex vivo induction of cardiomyogenic differentiation of mesenchymal stem cells (MSCs) before implantation would potentiate therapeutic efficacy of stem cell therapies for ischemic heart diseases because MSCs rarely undergo cardiomyogenic differentiation following implantation. In cardiac microenvironments, electric pulse and cyclic mechanical strain are sequentially produced. However, no study has applied the pulsatile mechanoelectric cues (PMEC) to stimulate cardiomyogenic differentiation of MSCs ex vivo.

Lattice Transparency of Graphene.

Here, we demonstrated the transparency of graphene to the atomic arrangement of a substrate surface, i.e., the "lattice transparency" of graphene, by using hydrothermally grown ZnO nanorods as a model system.

"Atomic Force Masking" Induced Formation of Effective Hot Spots along Grain Boundaries of Metal Thin Films.

We present an interesting phenomenon, "atomic force masking", which is the deposition of a few-nanometer-thick gold film on ultrathin low-molecular-weight (LMW) polydimethylsiloxane (PDMS) engineered on a polycrystalline gold thin film, and demonstrated the formation of hot spot based on SERS. The essential principle of this atomic force masking phenomenon is that an LMW PDMS layer on a single crystalline grain of gold thin film would repel gold atoms approaching this region during a second cycle of evaporation, whereas new nucleation and growth of gold atoms would occur on LMW PDMS deposited on grain boundary regions. The nanostructure formed by the atomic force masking, denoted here as "hot spots on grain boundaries" (HOGs), which is consistent with finite-difference time-domain (FDTD) simulation, and the mechanism of atomic force masking were investigated by carrying out systematic experiments, and density functional theory (DFT) calculations were made to carefully explain the related fundamental physics.

Inorganic Nano Light-Emitting Transistor: p-Type Porous Silicon Nanowire/n-Type ZnO Nanofilm.

An inorganic nano light-emitting transistor (INLET) consisting of p-type porous Si nanowires (PoSiNWs) and an n-type ZnO nanofilm was integrated on a heavily doped p-type Si substrate with a thermally grown SiO2 layer. To verify that modulation of the Fermi level of the PoSiNWs is key for switchable light emitting, I-V and electroluminescent characteristics of the INLET are investigated as a function of gate bias (V g ). As the V g is changed from 0 V to -20 V, the current level and light-emission intensity in the orange-red range increase by three and two times, respectively, with a forward bias of 20 V in the p-n junction, compared to those at a V g of 0 V.

Simple Interface Engineering of Graphene Transistors with Hydrophobizing Stamps.

We demonstrate a simple surface engineering method for fabricating graphene transistors by using hydrophobizing stamps. By simply contact-printing hydrophobizing stamp that is made with polydimethylsiloxane (PDMS) on a standard silicon substrate for a certain contact-time, it was possible to control the contact angle of the substrate and electrical characteristics of the graphene transistors supported on the substrate. Moreover, graphene transistors supported on the engineered silicon substrate showed improved performances, including an increase in carrier mobility and loss of hysteresis.