A Reinforced Light-Responsive Hydrogel for Soft Robotics Actuation

Light-responsive hydrogels are intelligent materials that respond to external light stimuli. When exposed to light, they shrink by releasing water, enabling non-invasive, cost-effective, and remotely controllable actuation. Their adaptability to light parameters such as intensity, direction, wavelength, and irradiation time makes these materials ideal for developing soft robotic actuators. However, hydrogel-based actuators face several challenges due to poor mechanical properties, complex fabrication, and biocompatibility concerns. To address these limitations, this study presents a light-driven 3D-printed elastomer/hydrogel composite actuator. The soft photo-actuator combines TangoPlus, a flexible 3D printing material, with a poly(N-isopropylacrylamide) (PNIPAM) hydrogel copolymerized with the photochromic molecule spiropyran. The study's key contributions include an investigation into prototypes that demonstrate enhanced mechanical integrity, where hydrogel thickness and curing time are shown to affect the actuator's shrinkage response in a predictable manner. Furthermore, a proof-of-concept of a 3D gripping mechanism is proposed to demonstrate the actuator's potential applicability.