A Double-Layer CNTs/PVA Hydrogel with High Stretchability and Compressibility for Human Motion Detection
Kun Huang, Yufeng Wu, Junchen Liu, Geng Chang, Xuchao Pan, Xiaodi Weng, Unit 96911 of PLA, Beijing, 100010, China, Yonggang Wang, Ming Lei
Abstract
With the development of technology and the improvement of living standards, hydrogel-based strain sensors have attracted more attention. However, the fabrication of hydrogel strain sensors with desirable mechanical and piezoresistive properties is still challenging. Herein, a double-layer flexible hydrogel sensor is presented, which is made of carbon nanotubes (CNTs) and polyvinyl alcohol (PVA) with high stretchability up to 415% strain and super compressibility to 92% strain, and considerable electrical conductivity (1.11 S m -1 ). The hydrogel sensors show great linearity throughout the detection range, excellent durability, and stable relative resistance change ( 0 ) during 1000 loading-unloading cycles. These excellent properties are attributed to a new double-layer structural design, i.e. a thin conductive sensor layer of CNTs/PVA deposited on a pure strong PVA substrate. Combined with fast response time (508 ms at stretch and 139 ms at compression) and biocompatibility, this new sensor offers great potential as a wearable sensor for epidermal sensing applications such as detecting the bending of human joints, swallowing, breathing, etc. Besides, the CNTs/PVA hydrogel can operate electronic screens due to its internal ions, and even use mechanical signals to modulate light signals. All of these demonstrate the great advantages of the CNTs/PVA hydrogels as strain sensors.