Ethanol stimuli-responsive toughening PNIPAM/PVA self-healing hydrogel thermal actuator

Abstract

Inspired by the stimuli-responsive ability of biological, a variety of hydrogel have been prepared by stimulus, showing great application value in actuators, soft robots, etc. However, it is still challenging to prepare a toughness hydrogel by the way of stimuli-responsive. Herein, we constructed a novel dual-network structure PNIPAM/PVA hydrogel using reversible molecular configuration conversion of PNIPAM chains. Under the stimulus of ethanol, the elastic modulus of PNIPAM/PVA hydrogel can be increased by 47 times (5 times the change of the modulus of sea cucumbers’ tissue) and the stress can be six times of the original. The dynamic borate ester bond formed by the cross-linking of PVA and borax in the hydrogel enables rapid self-healing (η > 99%) within three minutes without external stimulus in the natural environment. In addition, PNIPAM/PVA hydrogels also showed outstanding underwater reversible thermokinetic properties (>25°) based on the hydrophilic/hydrophobic conversion of PNIPAM under thermal stimulation. The successful preparation of ethanol stimulus-enhancing self-healing PNIPAM/PVA hydrogel actuators, provides a new idea for the development of the soft underwater robots.