Skin-inspired electronics:emerging semiconductor devices and systems

Current electronics are driven by advanced microfabrication for fast and efficient information processing.In spite of high performance,these wafer-based devices are rigid,non-degradable,and unable to autonomous repair.Skin-inspired electronics have emerged as a new class of devices and systems for next-generation flexible and wearable electronics.The technology gains inspiration from the structures,properties,and sensing mechanisms of the skin,which may find a broad range of applications in cutting-edge fields such as healthcare monitoring,human-machine interface,and soft robotics/prostheses.Practical demands have fueled the development of electronic materials with skin-like properties in terms of stretchability,self-healing capability,and biodegradability.These materials provide the basis for functional sensors with innovative and biomimetic designs.Further system-level integrations and optimizations enable new forms of electronics for real-world applications.This review summarizes recent advancements in this active area and speculates on future directions.

Healthcare electronic skin devices

Electronic skin(e-skin),a kind of flexible sensor arrays and system that mimic the properties and sensing functions of human skin,represents a new paradigm of sensing and control(Fig.1).The noun of'skin electronics'made its debut in the Sensitive Skin Workshop organized jointly by the National Science Foundation and Defense Advanced Research Projects Agency of USA in October 1999 in Arlington.

Multi‐vital on‐skin optoelectronic biosensor for assessing regional tissue hemodynamics

Evaluation of the oxygen‐mediated effects of clinical and daily activities demands an on‐skin device that can track multi‐vital regional tissue hemodynamics simultaneously.For example,peripheral arterial disease(PAD)is the third most prevalent cardiovascular disease,but the means of diagnosing and monitoring this disease are limited because the affected area is usually in the non‐pulsatile area away from the heart.Herein,we report on an ultrathin and ultralight multi‐vital near‐infrared optoelectronic biosensor for the diagnosis and rehabilitation monitoring of regional tissue hemodynamics,which is suitable for mounting on the skin for long‐term measurement.The device can simultaneously detect tissue oxygen saturation,heart rate,arterial blood oxygen,and tissue perfusion and shows potential for various hypoxia monitoring applications.Moreover,the tissue hemodynamics detected by this device showed a highly accordance with the ankle‐brachial index and CT angiography obtained by traditional clinical methods.Therefore,our design was able to accurately diagnose and effectively evaluate PAD patients before and after surgery.The on‐skin optoelectronic biosensor shows potential in biological oxygen‐mediated behavior evaluation,injury‐state monitoring,PAD clinical diagnosis optimization,and after surgery care.

Advanced synaptic devices and their applications in biomimetic sensory neural system

Human nervous system,which is composed of neuron and synapse networks,is capable of processing information in a plastic,dataparallel,fault-tolerant,and energy-efficient approach.Inspired by the ingenious working mechanism of this miraculous biological data processing system,scientists have been devoting great efforts to ar-tificial neural systems based on synaptic devices in recent decades.The continuous development of bioinspired sensors and synaptic devices in recent years have made it possible that artificial sensory neural systems are capable of capturing and processing stimuli informa-tion in real time.The progress of biomimetic sensory neural systems could provide new methods for next-generation humanoid robotics,human-machine interfaces,and other frontier applications.Herein,this review summarized the recent progress of synaptic devices and biomimetic sensory neural systems.Additionally,the opportunities and remaining challenges in the further development of biomimetic sensory neural systems were also outlined.

A scalable sulfuration of WS2 to improve cyclability and capability of lithium-ion batteries

Two-dimensional transition-metal dichalcogenides （WS2 and SnS2） have recently joined the family of energy storage materials （for lithium-ion batteries and supercapacitors） as a result of their favorable ion intercalation. So far, challenges in the synthesis of phase-pure WS2, restacking between WS2 nanosheets, low electronic conductivity, and the brittle nature of WS2, severely limit its use Li-ion battery application. Herein, we develop a facile low temperature solution sulfuration process to improve battery performance dramatically. The sulfuration process is demonstrated to be effective in converting WO3 impurities to WS2, and in repairing the sulfur vacancies, to improve cyclability and rate capability. Lithium-ion battery measurements demonstrate that the stable capacity of the WS2 anode could be enhanced by 48.4% via sulfuration reprocessing, i.e., from 381.7 to 566.8 rnAh/g at a relatively high current density of 0.8 A/g after 50 cycles. We further show that the sulfuration process can be readily extended to other dichalcogenides, and may provide a class of versatile electrode materials for lithium-ion batteries with improved electrochemical characteristics.