Stretchable and self-healing carboxymethyl cellulose/polyacrylic acid conductive hydrogels for monitoring human motions and electrophysiological signals

Abstract

Stretchable conductive hydrogels have attracted great attention in flexible electronics. Nevertheless, conductive hydrogels would suffer from an inevitable damage during use, significantly reducing the reliability and limiting the practicability. Herein, stretchable and self-healing conductive hydrogels are designed form carboxymethyl cellulose (CMC), polyacrylic acid (PAA), and Fe³⁺, which are applied for monitoring human motions and electrophysiological signals. The plentiful H-bonding and metal coordination endow the conductive hydrogels with good mechanical (fracture strain: 917 %; fracture stress: 202 kPa; toughness: 1.1 MJ m⁻³) and self-healing properties. After self-healing, the fracture stress is almost fully recovered, the fracture strain is restored to 72 %, and the conductivity is reestablished to 98 %. The conductive hydrogels show good fatigue resistance during cyclic tensile and compressive loading-unloading tests. Furthermore, the mechanical deformation would lead to the resistance change of the hydrogel to realize the electrical signal record. So, the hydrogel was assembled into a flexible wearable sensor that has good electrical conductivity (0.779 S m⁻¹), fast responsiveness (response time: 300 ms; recovery time: 200 ms) and high sensitivity (gauge factor (GF) = 7.99, 400–650 %). This work demonstrates a simple and efficient strategy for developing stretchable and self-healing conductive hydrogels in healthcare monitoring and flexible electronics.