Flexible and Stretchable Capacitive Sensors with Different Microstructures

• Published in: Advanced materials (Weinheim) 2021-08, Vol.33 (34), p.e2008267-n/a
• Main Authors: Qin, Jing, Yin, Li‐Juan, Hao, Ya‐Nan, Zhong, Shao‐Long, Zhang, Dong‐Li, Bi, Ke, Zhang, Yong‐Xin, Zhao, Yu, Dang, Zhi‐Min
• Format: Article
• Language: English
• Subjects: Animals; Biosensing Techniques - instrumentation; capacitive sensors; Electric Capacitance; Electric Impedance; Equipment Design; geometric design; Humans; Materials science; microstructures; Monitoring, Ambulatory - instrumentation; Polymers; Pressure; Pressure sensors; Robotics; sensitivity; Sensors; Skin; stretchable materials; Temperature; Textiles; User-Computer Interface; Wearable Electronic Devices
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202008267

Recently, sensors that can imitate human skin have received extensive attention. Capacitive sensors have a simple structure, low loss, no temperature drift, and other excellent properties, and can be applied in the fields of robotics, human–machine interactions, medical care, and health monitoring. Polymer matrices are commonly employed in flexible capacitive sensors because of their high flexibility. However, their volume is almost unchanged when pressure is applied, and they are inherently viscoelastic. These shortcomings severely lead to high hysteresis and limit the improvement in sensitivity. Therefore, considerable efforts have been applied to improve the sensing performance by designing different microstructures of materials. Herein, two types of sensors based on the applied forces are discussed, including pressure sensors and strain sensors. Currently, five types of microstructures are commonly used in pressure sensors, while four are used in strain sensors. The advantages, disadvantages, and practical values of the different structures are systematically elaborated. Finally, future perspectives of microstructures for capacitive sensors are discussed, with the aim of providing a guide for designing advanced flexible and stretchable capacitive sensors via ingenious human‐made microstructures. The advantages, disadvantages, and practical applications of several popular microstructures that are widely employed in capacitive sensors are summarized. A microstructured dielectric layer or electrode can improve sensor sensitivity, reduce hysteresis, and endow the rigid electronic device with excellent elastic stretchability, which is an essential part of next‐generation wearable devices and soft robots.