Printing of self-healable gelatin conductors engineered for improving physical and electrical functions: Exploring potential application in soft actuators and sensors

Abstract

Significant efforts have been devoted to developing dielectric elastomer actuators owing to their mechanical flexibilities, silent operation, and muscle-like performances. However, it still remains a challenge to demonstrate the actuators that maintain function when subjected to damage because most soft materials constituting such devices are vulnerable to mechanical stresses during repeated operation. Here, self-healable electrodes suitable for dielectric elastomer actuators were prepared from an eco-friendly gelatin-based composite including conductive ions and hydrogen bonds. Electrohydrodynamic printing was used to reproducibly fabricate a custom-made electrode with desired geometry. The printed gelatin-based electrodes were attached onto elastomers to fabricate dielectric elastomer actuators. The devices exhibited good actuator operation and, owing to the self-healing capability of the gelatin-based electrodes, almost fully recovered their performances with an efficiency of up to 96.8% even after the electrodes were damaged. Furthermore, the potential application of the gelatin-based electrode was explored by using them as a strain sensor; this sensor showed a sensitive dependence of electrical resistance on external joint movements. We believe this work provides a useful guideline for designing self-healable conductive composites that can be effectively used to make printed actuators and sensors endowed with good ionic conductivity and useful mechanical properties.