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The detection of surface electromyography (sEMG) signals on the skin has attracted increasing attention because of its ability to monitor muscle conditions in a noninvasive manner and thus possesses great application potential to assess athletic status and training efficiency in real time or to evaluate postoperative muscle rehabilitation conveniently. Here, a flexible wireless sEMG monitoring system that consists of a stretchable sEMG epidermal patch and a flexible printed circuit board to provide real‐time evaluation of muscle strength and fatigue is reported. The epidermal patch is designed to have good stretchability and permeability and optimized to ensure a low contact impedance with the skin and minimized background noise for sEMG signal acquisition with high fidelity. Six commonly used time‐domain and two frequency‐domain features extracted from sEMG signals are systematically analyzed, and a strategy for feature selection and pattern identification is proposed that eventually enables the real‐time assessment of muscle strength and fatigue by using an integrated system in a wearable form. [ABSTRACT FROM AUTHOR]

The piezophototronic effect is known as a three-way coupling between piezoelectric polarization, semiconductor property, and optical excitation in piezoelectric semiconductor materials to modify their energy band structures by strain-induced piezoelectric polarization charges, and thus to tune/control their optoelectronic processes of charge carrier generation, separation, recombination, and transport. In this work, the temperature dependence of the piezophototronic effect in wurtzite-structured CdS nanowires is investigated from 77 to 300 K. The piezophototronic effect is enhanced by over 550% under lower temperature due to the increased effective piezoelectric polarization surface/interface charges resulting from the reduced screening effect by decreased mobile charge carriers in CdS nanowires. Optoelectronic performances of CdS nanowires are systematically investigated under various light illuminations, strains, and temperatures. By analyzing the corresponding band diagrams, the piezophototronic effect is found to dominate the transport and separation processes of charge carriers. This study presents in-depth fundamental understanding about the piezophototronic effect and provides guidance for its future applications in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Single-electrode triboelectric nanogenerators (SETENGs) significantly expand the application of triboelectric nanogenerators in various circumstances, such as touch-pad technologies. In this work, a theoretical model of SETENGs is presented with in-depth interpretation and analysis of their working principle. Electrostatic shield effect from the primary electrode is the main consideration in the design of such SETENGs. On the basis of this analysis, the impacts of two important structural parameters, that is, the electrode gap distance and the area size, on the output performance are theoretically investigated. An optimized electrode gap distance and an optimized area size are observed to provide a maximum transit output power. Parallel connection of multiple SETENGs with micro-scale size and relatively larger spacing should be utilized as the scaling-up strategy. The discussion of the basic working principle and the influence of structural parameters on the whole performance of the device can serve as an important guidance for rational design of the device structure towards the optimum output in specific applications. [ABSTRACT FROM AUTHOR]

Degradable Electronics: Wafer-Scale High-Yield Manufacturing of Degradable Electronics for Environmental Monitoring (Adv. Funct. In article number 1905518, Youfan Hu and co-workers develop a wafer-scale high-yield manufacturing process for degradable electronics with a degradable system for real-time environmental monitoring. High device yields, high-uniformity, and great performance are achieved simultaneously, which provide new opportunities for degradable electronics for next-generation ecofriendly sensing platforms for the coming Internet of Things era. [Extracted from the article]

Degradable electronics that dissolve or disintegrate in the environment after completing target functions are highly desirable due to great capabilities to eliminate the disposal, retrieval, and recycling of electronic waste worldwide. Constructing electronic systems on water‐soluble substrates via transfer printing technology has emerged as a promising approach toward this goal. However, the current approach suffers from low yields and thus hinders the complexity and scale of the obtained system in practical applications. Here, a wafer‐scale manufacturing process is proposed for degradable systems with high yields. As a demonstration, chips based on carbon nanotube thin films are 100% successfully transferred to water‐soluble substrates with an average device yield of 96.6%. Great uniformity is also obtained in the transferred thin‐film transistors (TFTs) and integrated circuits with a minimum standard deviation of 55 and 60 mV in the threshold voltage of TFTs and switching threshold voltage of inverters, respectively. System‐level demonstration of real‐time environmental monitoring is implemented in a simulated ecosystem together with a degradation demonstration under artificial rain. With its combined great performance, processing robustness, and high yields, this technology provides new opportunities for batch manufacturing of degradable electronics and next‐generation ecofriendly sensing platforms for the coming Internet of Things era. [ABSTRACT FROM AUTHOR]

By introducing stretchability and/or deformability to planar electronics, devices can conformably attach to 3D curved surfaces with minimal invasiveness, which is of great interest for next‐generation wearables in clinical and biological applications. Here, a feasible route is demonstrated to generate deformable 3D structures as a robust platform to construct electronic systems by utilizing silver nanowires/parylene hybrid films in a way analogous to the art of kirigami. The hybrid films exhibit outstanding electrical conductivity along with decent optical transparency, flexibility, and long‐term stability. These merits enable these films to work as electrodes for electrocardiogram recording with comparable accuracy to a commercial counterpart, and to fabricate a 7‐GHz monopole antenna with good omni‐directionality and a peak gain of 1.35 dBi. More importantly, a general scheme for constructing 3D deformable electronic systems is presented, including unique patterning procedures and rational cut designs inspired by kirigami. As an example, deformable transparent humidity sensors are fabricated to work on elbows and finger joints for sweating monitoring. The strategy demonstrated here for 3D deformable system construction is versatile and holds great promise for future advanced health monitoring at diverse and complex epidermal surfaces. 3D deformable electronic systems are constructed by utilizing silver nanowires/parylene hybrid films in a way similar to the art of kirigami. This combines unique patterning procedures and rational cut designs, providing a general platform for physiological signal monitoring on curved biological surface. A deformable transparent humidity sensor for sweating monitoring on the elbow and finger joint is demonstrated. [ABSTRACT FROM AUTHOR]

In article number 1801070, Youfan Hu and co‐workers construct 3D deformable electronic systems for physiological monitoring on curved surfaces by utilizing silver nanowires/parylene hybrid films in a way inspired by kirigami. Unique patterning procedures and rational cut designs are combined to transform planar electronic systems into a tunable 3D form. As an example, a deformable transparent humidity sensor for sweat monitoring was demonstrated on an elbow and finger joint. [ABSTRACT FROM AUTHOR]