Programmable and multi-stimuli responsive hydrogel actuator mediated by nanocellulose with intrinsic self-sensing...

Stimuli-responsive hydrogels demonstrate tremendous potential in soft robotics and flexible wearable electronics owing to their response capability when exposed to external stimuli. Nevertheless, the development of a multi-stimuli responsive, remotely actuated, programmable hydrogel with intrinsic self-sensing properties remains a significant challenge. Herein, a near-infrared (NIR) light/thermal/magnetic multi-responsive hydrogel actuator based on delignified wood (DW) embedded Fe₃O₄/liquid metal/(2,2,6,6-tetramethylpiperidin-1-yl)oxyl-oxidized cellulose nanofiber-poly(N-isopropylacrylamide) (Fe₃O₄/LM/TOCN-PNIPAM) hydrogel is fabricated. TOCNs facilitate both homogeneous dispersion of functional fillers and robust interfacial binding between the hydrogel and DW. The anisotropic structure of DW endows the hydrogel actuator with programmable shape-morphing capability. The hydrogel actuator with bending velocity of 300° s^-1 under thermal activation and 7.5° s^-1 under NIR light stimulation can be used as a soft gripper for object manipulation. In addition, the light/magnetic responsive hydrogel actuators with electrical conductivity (3.7 S m^-1) possess precise remote controllability and can be used as intelligent switches. When driven remotely by NIR light and magnetic field, the conductive hydrogel can generate corresponding electrical signals, thereby providing real-time feedback on its own movement. This integrated material system, combining multi-responsive actuation with real-time sensory, establishes a new paradigm for developing next-generation intelligent soft robotics with self-regulatory control.