High-Performance Conductive Hydrogel Prepared by an Electrohydrodynamic Printing Method for Strain Sensors and Self-Powered Triboelectric Nanogenerator

A conductive hydrogel is widely used in flexible electronics, strain sensors, and energy harvesting. However, poor mechanical property, low sensitivity, and slow response time limit their application in strain sensors and triboelectric nanogenerators (TENG). In order to address these issues, using polyacrylamide (PAM), cellulose nanofibers (CNF), and MXene composites as preparation materials, an electrohydrodynamic (EHD) printing method assisted in-situ photopolymerization is proposed to fabricate a PAM/CNF/MXene (PCM) conductive hydrogel. MXene in the precursor solution of the hydrogel is orderly arranged under the influence of electrostatic field force, thereby forming a stable conductive channel of MXene. Compared with the traditional preparation technology, the conductivity of hydrogels fabricated through this method is improved by 58%. Hydrogen bond is formed between CNF and PAM, which improves the mechanical properties of hydrogels. MXene can form interpenetrating networks with the PAM/CNF hydrogel, providing conductive channels for the hydrogel and improving its mechanical properties and sensing performance. The structure with interpenetrating networks endows PCM hydrogel with outstanding mechanical properties (550% tensile strain). Strain sensors based on PCM hydrogel exhibits eminent sensitivity (6.73 gauge factor), rapid response/recovery time (100/110 ms), and broad detection range (1% ∼ 550%). CM-TENG shows excellent electric output performance (67.5 V open circuit voltage at 100% strain). In addition, the strain sensor based on PCM hydrogel is applied to human motion monitoring and information transmission, and the self-powered PCM-TENG flexible sensor is used for writing recognition. The conductive hydrogel has broad application prospects in flexible sensors, information transmission, and self-powered supply.