Multifunctional Skin‐Inspired Flexible Sensor Systems for Wearable Electronics

Abstract

Skin‐inspired wearable devices hold great potentials in the next generation of smart portable electronics owing to their intriguing applications in healthcare monitoring, soft robotics, artificial intelligence, and human–machine interfaces. Despite tremendous research efforts dedicated to judiciously tailoring wearable devices in terms of their thickness, portability, flexibility, bendability as well as stretchability, the emerging Internet of Things demand the skin‐interfaced flexible systems to be endowed with additional functionalities with the capability of mimicking skin‐like perception and beyond. This review covers and highlights the latest advances of burgeoning multifunctional wearable electronics, primarily including versatile multimodal sensor systems, self‐healing material‐based devices, and self‐powered flexible sensors. To render the penetration of human‐interactive devices into global markets and households, economical manufacturing techniques are crucial to achieve large‐scale flexible systems with high‐throughput capability. The booming innovations in this research field will push the scientific community forward and benefit human beings in the near future.

Cyber–Physiochemical Interfaces

“…Materials are the basis for constructing CPI system with multilayer stretchable functional units . Researchers have turned to designing materials with compatible mechanical properties via various approaches such as molecular and geometry design, nanomaterial network manipulation, and hydrogel‐based electrodes . Molecular design is a bottom‐up approach, where both elastic and rigid units are rationally designed to dynamically tune the mechanical properties (Figure b) .…”

Multifunctional Electronic Skin Based on Perovskite Intermediate Gels

“…Additional functionalities, such as chemical, optical, or electrical sensing capabilities, are also considered to be incorporated, which can imitate better or even surmount the perceptive capabilities of human skin. In order to reach this ambitious goal, the further study of e‐skin devices is encouraged to be transited from “unitary functional e‐skin” to “multifunctional e‐skin.”14–17 Herein, for the first time, we reported a novel flexible and stretchable multifunctional e‐skin sensors using a Sn‐based perovskite intermediate gel (PIGel) as the sensing material. In addition, the advantage of low‐cost and facile fabrication processes of the sensing material make the PIGel e‐skin sensor very attractive for the future commercial application.…”

“…Researchers successfully relate ion migration with the resistive switching phenomenon and OIHPs have been extensively studied in the resistive switching memory device 29,30. In the case of e‐skin, resistive strain sensors are a kind of very common detector to perceive external environmental conditions and various conductive materials (such as CNT, silver nanowire, gold nanowires, conducting polymers) are used as sensing materials 13–17,31. Recently, the concept of ionic e‐skin sensor was proposed.…”

“…[29,30] In the case of e-skin, resistive strain sensors are a kind of very common detector to perceive external environmental conditions and various conductive materials (such as CNT, silver nanowire, gold nanowires, conducting polymers) are used as sensing materials. [13][14][15][16][17]31] Recently, the concept of ionic e-skin sensor was proposed. Ionogels have been successfully applied to e-skins owing to their excellent ionic transport property, which makes it possible to utilize the ion migration in perovskite materials for e-skin application.…”

“…In order to reach this ambitious goal, the further study of e-skin devices is encouraged to be transited from "unitary functional e-skin" to "multifunctional e-skin." [14][15][16][17] Herein, for the first time, we reported a novel flexible and stretchable multifunctional e-skin sensors using a Sn-based perovskite intermediate gel (PIGel) as the sensing material. In addition, the advantage of low-cost and facile fabrication processes of the sensing material make the PIGel e-skin sensor very attractive for the future commercial application.Organic-inorganic hybrid perovskite materials (OIHPs) are a type of inexpensive, solution processable, and versatile materials, which are usually composed of organic cations (methylammonium or formamidinium ion, MA + or FA + ), metal cations (e.g., Pb 2+ , Sn 2+ , Ge 2+ , Cd 2+ , Bi 3+ , or Sn 4+ ) and halogen anions (e.g., Cl − , Br − , I − ).…”