Selective in Situ Dynamic Motion Stay and Recover Under Single Nir Light in Soft Actuator by Triggered Shape-Memory and Phase Transition of Hydrogel

Abstract

Inspired by nature, hydrogel actuators are important for designing soft robots and become one of the most essential components of intelligent research. However, classical actuation method, such as Near-Infrared (NIR) light stimulates the actuator to complete the motions then it automatically recovers original state when the light is off, cannot provide continuous in situ dynamic motion stay and recovery under one NIR light. In this study, a novel network-polycaprolactone (Net-PCL)-poly N-isopropylacrylamide (PNIPAM) hydrogel actuator (Net-PCL-Gel) is proposed through a layer-by-layer stacking technology, leading to the co-existence of Net-PCL with photoinduced shape memory capability and PNIPAM hydrogel segments showing de-swelling/swelling phase transition. Owing to the shape memory property of Net-PCL, the Net-PCL-Gel exhibits in situ dynamic bending and recovering stay behavior in response to NIR irradiation with the active force of PNIPAM. Different from the conventional hydrogel system, the Net-PCL-Gel also displayed remarkable decryption performance in information reading and hiding, while retaining excellent accuracy and stability. Due to its simplicity, this strategy shows great potential for the biomimetic operation of soft grippers and multifunctional actuators.

Keywords: Dynamic in situ actuation, information decryption, single stimulus-response, hydrogel actuators, soft materials