Self-regulated photoresponsive heterogeneous PNIPAM hydrogel actuators†

Abstract

Self-regulated actuators harness material intelligence to enable complex deformations and dynamics, representing a significant advancement in automated soft robotics. However, investigations on self-regulated soft actuators, particularly those using simplified actuation modules, such as a unidirectional light beam, remain limited. Here, we present a design paradigm for self-regulated actuators based on poly(N-isopropylacrylamide) (PNIPAM) heterogeneous hydrogels, where self-regulated deformations are actuated using a fixed near-infrared laser. By utilizing the different responsiveness of PNIPAM hydrogels and those integrated with reduced graphene oxide (rGO), we have developed three heterogeneous hydrogel configurations: up–down, side-by-side, and hybrid types. These designs enable complex biomimetic deformations in soft hydrogel actuators, resembling a bending finger or a flexible industrial manipulator, all actuated using a single fixed-laser source. These proposed heterogeneous designs and actuation strategies leverage material intelligence to create soft actuators with enhanced autonomy, paving the way for soft automation, adaptive systems, and biomedical applications.