A Double-layer Carbon Nanotubes/Polyvinyl Alcohol Hydrogel with High Stretchability and Compressibility for Human Motion Detection

Kun Huang,1

Yufeng Wu,1

Junchen Liu,1

Geng Chang,2

Xuchao Pan,2,*Email

Xiaodi Weng,3,*Email

Yonggang Wang1

Ming Lei1,*Email

1State Key Laboratory of Information Photonics and Optical Communications, School of Science, Beijing University of Posts and Telecommunications, Beijing 100876, China

2Ministerial Key Laboratory of ZNDY, Nanjing University of Science &Technology, Nanjing, 210094, China

3Unit 96911 of PLA, Beijing, 100010, China

Abstract

With the development of technology and the improvement of living standards, hydrogel-based strain sensors have attracted more attention. However, 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 supercompressibility 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 (RR0 ) 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 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.

A Double-layer Carbon Nanotubes/Polyvinyl Alcohol Hydrogel with High Stretchability and Compressibility for Human Motion Detection