Highly stretchable, transparent and conductive double-network ionic hydrogels for strain and pressure sensors with ultrahigh sensitivity

作者：Yu, Jie; Wang, Ming; Dang, Chao; Zhang, Cunzhi; Feng, Xiao; Chen, Guixian; Huang, Zhongyuan; Qi, Haisong; Liu, Hongchen^*; Kang, Jian

来源：Journal of Materials Chemistry C, 2021, 9(10): 3635-3641.

DOI：10.1039/d0tc05242f

Ionic conductive hydrogels have attracted much attention in artificial electronic skins and wearable strain sensors. However, most of the hydrogel-based sensors exhibit poor mechanical properties and limited sensitivity. Herein, a highly stretchable and transparent ionic conductive hydrogel was fabricated by one-step polymerization to assemble sensors based on the dynamic crosslinked network, which consists of long polyacrylamide (PAM) chains as a skeleton and dialdehyde beta-cyclodextrin (O-beta-CD) cross-linked gelatin (Gel) as a sacrificial network. Dynamic chemical and physical cross-linking can endow the hydrogel with remarkable stretchability (>1200%) and good self-recovery properties. The excellent ionic conductivity (53.3 mS cm(-1)) was realized mainly due to the integration of sodium chloride (NaCl). Notably, the hydrogel exhibits ultrahigh strain/pressure sensitivity (GF are 4.58 and 0.56 kPa(-1), respectively), a broad working range (0-1200%, and 0-250 kPa), and appealing repeatability (output signal remains almost constant over 500 cyclic tensile and compression tests), which can be used as a wearable sensor to monitor human motions including a variety of joint movements, and even subtle motions such as pulse and speaking. Therefore, the hydrogels have great potential to be further developed in human health monitoring, human-machine interaction, and skin-like electronics in the future.