Ultrastretchable, Highly Conductive, Rapid Self-Recovery, and Antiswelling Hydrogels as Multifunctional Wearable Electronic Devices

Abstract

The development of wearable electronic devices requires stretchable, highly conductive, self-recovery, and ideally environmentally resistant sensors. Hydrogels are ideal candidates for fabricating flexible sensors due to their stretchability and unique ionic conduction pathways. However, the intrinsic incompatibility of the conductive and elastic networks in hydrogels and the high hydrophilicity of the hydrogel network led to difficulties in obtaining hydrogels with strong mechanical properties, high conductivity, rapid self-recovery ability, and antiswelling properties. Based on the single-core multidentate coordination strategy, single-core multidentate coordinated chitosan/poly(acrylic acid)/Al3+ (CPAL) hydrogels were prepared with Al3+ as a metal coordination center and the amino group of chitosan (CS) and the carboxyl group of poly(acrylic acid) (PAA) as coordination atoms. The obtained hydrogels exhibit excellent tensile stress/strain: 1.11 ± 0.04 MPa/2472.79 ± 99.27%, rapid self-recovery capability (mechanical properties were fully recovered in 10 min), antifatigue property, good conductivity (1.09 ± 0.02 S/m), and antiswelling property. Furthermore, flexible sensors based on CPAL hydrogels demonstrated multiplex mode sensing. It was worth noting that the flexible devices based on CPAL hydrogel could not only use Morse code table to realize mechanical-information visualization but also detect the human condition in multiple dimensions, including temperature, electromyographic (EMG), and electrocardiogram (ECG). In this work, we reported a single-core multidentate coordination strategy that provided a pathway for fabricating the ideal hydrogel-based flexible sensors, showing great potential for wearable electronic devices.