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Flexible materials with sufficient mechanical endurance under bending or folding is essential for flexible electronic devices. Conventional rigid materials such as metals and ceramics are mostly brittle so that their properties can deteriorate under a certain amount of strain. In order to utilize high-performance, but brittle conventional materials in flexible electronics, we propose a novel flexible substrate structure with a low-modulus interlayer. The low-modulus interlayer reduces the surface strain, where active electronic components are placed. The bending results with indium tin oxide (ITO) show that a critical bending radius, where the conductivity starts to deteriorate, can be reduced by more than 80% by utilizing the low-modulus layer. We demonstrate that even rigid electrodes can be used in flexible devices by manipulating the structure of flexible substrate.

Flexible and skin-attachable vibration sensors have been studied for use as wearable voice-recognition electronics. However, the development of vibration sensors to recognize the human voice accurately with a flat frequency response, a high sensitivity, and a flexible/conformable form factor has proved a major challenge. Here, we present an ultrathin, conformable, and vibration-responsive electronic skin that detects skin acceleration, which is highly and linearly correlated with voice pressure. This device consists of a crosslinked ultrathin polymer film and a hole-patterned diaphragm structure, and senses voices quantitatively with an outstanding sensitivity of 5.5 V Pa −1 over the voice frequency range. Moreover, this ultrathin device (<5 μm) exhibits superior skin conformity, which enables exact voice recognition because it eliminates vibrational distortion on rough and curved skin surfaces. Our device is suitable for several promising voice-recognition applications, such as security authentication, remote control systems and vocal healthcare. Though skin-attachable vibration sensors are promising for voice recognition applications, current technologies do not meet key performance requirements. Here, the authors report a flexible skin-attachable sensor with high sensitivity and flat frequency response over the vocal frequency range.

Superhydrophobic surfaces (SHS), with their exceptional water‐repellent properties, have attracted great interest due to their versatile applications. The robustness of SHS has emerged as an essential issue for practical applications, as SHS are directly exposed to various harsh environments, such as continuous raindrop impact, corrosive media, and extreme temperatures. Polyimide (PI) is an ideal candidate for robust SHS due to its superior mechanical, thermal, and chemical properties. However, the low processability of PI in surface microstructuring has limited its application in SHS. In this study, a high‐yield and cost‐effective fabrication method for constructing high‐aspect‐ratio PI microstructures has been developed by controlling the template surface treatment, precursor molecular weight, and vacuum process. This approach achieves an exceptional yield rate of 99.8% and an aspect ratio of 10.7, enabling the construction of various microstructures. The SHS is demonstrated by fabricating microstructures on PI surfaces using the proposed method. The PI SHS exhibits a water contact angle of up to 162° and a roll‐off angle of less than 9°. The water repellency withstands 100 tape peeling tests and remains stable after continuous exposure to temperatures up to 250 °C and various chemical reagents for 60 days, which presents excellent robustness against environmental factors. This study presents robust polyimide superhydrophobic surfaces with excellent mechanical durability, thermal stability, and chemical stability. A high‐yield and cost‐effective method to fabricate high‐aspect‐ratio polyimide surface microstructures is developed by controlling the template surface treatment, precursor molecular weight, and vacuum process time. The proposed method is applied for the realization of robust superhydrophobic surfaces.

Dysphagia, a swallowing disorder, requires continuous monitoring of throat-related events to obtain comprehensive insights into the patient’s pharyngeal and laryngeal functions. However, conventional assessments were performed by medical professionals in clinical settings, limiting persistent monitoring. We demonstrate feasibility of a ubiquitous monitoring system for autonomously detecting throat-related events utilizing a soft skin-attachable throat vibration sensor (STVS). The STVS accurately records throat vibrations without interference from surrounding noise, enabling measurement of subtle sounds such as swallowing. Out of the continuous data stream, we automatically classify events of interest using an ensemble-based deep learning model. The proposed model integrates multiple deep neural networks based on multi-modal acoustic features of throat-related events to enhance robustness and accuracy of classification. The performance of our model outperforms previous studies with a classification accuracy of 95.96%. These results show the potential of wearable solutions for improving dysphagia management and patient outcomes outside of clinical environments.

A novel detachment method is presented for flexible substrates from glass carrier wafers using a CO2 point laser. In a conventional laser lift‐off process, laser‐induced illumination and thermal stress degrade device performance. In this approach, a point laser is applied on the edge of the flexible substrate, where electrical components do not exist, and thus, no performance degradation occurs during the laser process. In addition, the carrier surface properties are modified to control the adhesion force between the flexible substrate and the glass carrier. A spin‐on‐dielectric layer (SOD) is utilized, and Ar ion bombardment is performed on SOD. The point laser detachment method is demonstrated in flexible thin‐film transistors, and no change is observed in the electrical characteristics before and after detachment from the carrier wafer. CO2 point laser is applied to a flexible substrate attached on a carrier wafer for a gentle detachment without laser‐induced stress. Surface properties on the carrier are precisely controlled to modify the adhesion. When the adhesion is optimized, flexible electronic devices can be gently detached from the carrier without any performance degradation.

Analog in‐memory computing, leveraging resistive switching cross‐point devices known as resistive processing units (RPUs), offers substantial improvements in the performance and energy efficiency of deep neural network (DNN) training. Among the promising candidates for RPU devices, the capacitor‐based synaptic circuit stands out due to its near‐ideal switching characteristics. However, despite its potential, challenges such as large cell areas and retention issues remain to be addressed. In this work, we study the three‐transistors‐one‐capacitor synaptic cell design, aiming to enhance computing performance and scalability. Through comprehensive device‐level modeling and system‐level simulation, assessment is done on how the transistor characteristics influence DNN training accuracy and reveal critical design strategies. A novel cell design methodology that optimizes computing performance while minimizing cell area is proposed, thereby enhancing scalability. Additionally, development guidelines for cell components are provided, identifying oxide‐based semiconductors as a promising channel material for transistors. This research contributes valuable insights for the development of future analog DNN training accelerators using capacitor‐based synaptic cell, with a focus on addressing the current limitations and maximizing efficiency. This work explores the three‐transistors‐one‐capacitor synaptic cell design for analog in‐memory computing, focusing on improving performance and scalability in deep neural network (DNN) training. By optimizing transistor characteristics and proposing a novel cell design, challenges such as large cell areas and retention issues are addressed. Oxide‐based semiconductors are identified as promising materials, offering pathways for more efficient DNN accelerators.

The physical structure of an organic solid is strongly affected by the surface of the underlying substrate. Controlling this interface is an important issue to improve device performance in the organic electronics community. Here we report an approach that utilizes an organic heterointerface to improve the crystallinity and control the morphology of an organic thin film. Pentacene is used as an active layer above, and m -bis(triphenylsilyl)benzene is used as the bottom layer. Sequential evaporations of these materials result in extraordinary morphology with far fewer grain boundaries and myriad nanometre-sized pores. These peculiar structures are formed by difference in molecular interactions between the organic layers and the substrate surface. The pentacene film exhibits high mobility up to 6.3 cm 2  V −1  s −1 , and the pore-rich structure improves the sensitivity of organic-transistor-based chemical sensors. Our approach opens a new way for the fabrication of nanostructured semiconducting layers towards high-performance organic electronics. High-performance organic electronics require minimal grain boundaries in an organic semiconductor active layer. Here, Kang et al. report the growth of pentacene thin films in a macroporous structure with improved crystallinity, which is guided by a chemically heterogeneous, rubber-like substrate.

The middle cerebral artery occlusion (MCAO) model is widely used to study stroke pathobiology. Dexmedetomidine (DEX) has demonstrated neuroprotective effects in ischemic brain models. Previous studies have shown that nuclear factor erythroid 2-related factor 2 (Nrf2) expression changes in the parietal cortex, which is supplied by the middle cerebral artery, after ischemic injury. While Nrf2 is known to regulate brain-derived neurotropic factor (BDNF) expression, its role in MCAO conditions has not been fully explored. This study aimed to investigate the effects of DEX on Nrf2 and BDNF expression in the parietal cortex following MCAO. Mice were subjected to MCAO by inserting a silicone-coated suture into the common carotid artery. After 30 min, the suture was withdrawn to induce ischemia/reperfusion (IR) injury. Cortical brain tissues were harvested three days post-injury. Western blot analysis was performed to measure BDNF protein expression. The expression levels of the messenger ribonucleic acid (mRNA) Nrf2, pro-apoptotic protein (Bax), and anti-apoptotic protein (Bcl-2) were analyzed using quantitative real-time polymerase chain reaction. The mRNA level of Nrf2 was significantly higher in the DEX group than in the MCAO group after three days of MCAO. BDNF protein expression (15 kDa) was also higher in the DEX group than in the MCAO group. Furthermore, Bax mRNA was lower, while Bcl-2 mRNA was higher in the DEX group than in the MCAO group. DEX treatment up-regulated Nrf2 expression, which was associated with increased BDNF expression three days after MCAO.

Flexible Electronics In article number 2202337, Hyuk Park, Yoonyoung Chung, and colleagues use a roll‐to‐roll process to fabricate electronic devices on a flexible substrate. Point laser beams are applied along the edge of each device, and they are gently detached from the applied edge by a tensile force generated by the roll curvature. After the laser illumination, the devices are entirely separated from the carrier.

A novel detachment method is presented for flexible substrates from glass carrier wafers using a CO 2 point laser. In a conventional laser lift‐off process, laser‐induced illumination and thermal stress degrade device performance. In this approach, a point laser is applied on the edge of the flexible substrate, where electrical components do not exist, and thus, no performance degradation occurs during the laser process. In addition, the carrier surface properties are modified to control the adhesion force between the flexible substrate and the glass carrier. A spin‐on‐dielectric layer (SOD) is utilized, and Ar ion bombardment is performed on SOD. The point laser detachment method is demonstrated in flexible thin‐film transistors, and no change is observed in the electrical characteristics before and after detachment from the carrier wafer.