Low-temperature 3D-printing conductive hydrogel based sensing materials for highly sensitive soft strain sensors

Abstract

A highly sensitive conductive hydrogel sensing material and its soft strain sensor were successfully developed by combining low-temperature 3D printing technology with in-situ reduction of silver particles on polyvinyl alcohol-carboxymethyl cellulose (PVA-CMC) hydrogel matrix surfaces. Excellent mechanical strength and diverse structural forms were exhibited by the low-temperature 3D printed PVA-CMC hydrogel matrix. After conductive functionalization, high sensitivity characteristics were achieved by the conductive hydrogel via sensing mechanisms, which were primarily based on the microcracks in the silver particle layer and the unfolding tunneling effect of soft hydrogel layers. Various human physiological signals such as pulse, as well as subtle loads like airflow and water droplets, can be effectively monitored. A distinct and unique polynomial functional relationship with applied loads was demonstrated by the resistance changes of the conductive hydrogel. When the conductive hydrogel was utilized as a sensing material in array form within a resistance acquisition and display system, the magnitude and position of various load forms can be accurately displayed in real-time. The error between the actual load measured by the conductive hydrogel and the theoretical value was found to be only 0.008 N. An effective solution for developing highly sensitive and stable conductive hydrogel-based strain sensors for micro-strain applications was provided by this work, while the development and practical application of conductive hydrogel-based flexible strain sensors can be promoted by the customization advantages of low-temperature 3D printing.