Soft robots with different movement capabilities based on photo-responsive multilayer poly(N-isopropylacrylamide) and...

Soft robots based on stimulus-responsive hydrogels can utilize external stimuli to achieve controllable actuation and perception. Multilayer hydrogel materials can be used to develop stimulus-responsive soft robots with high complexity and stability. In this work, hydrogels with different properties are synthesized by adjusting the component ratio of the poly(N-isopropylacrylamide) (PNIPAM) prepolymer solution. Multilayer hydrogel structures with good mechanical properties and temperature response characteristics are fabricated by using photopolymerization 3D printing technology. In addition, PNIPAM hydrogels are combined with multi-walled carbon nanotubes (MWCNTs) by impregnation to form a composite hydrogel with excellent photo-responsiveness. We put forward the hydrogel structural dynamic model and control equation, unveiled the driving principle and design method of the robot, and determined the key parameters for adjusting dynamics. Inspired by the deformation of frogs, we have designed three bionic miniature soft robots based on multilayer hydrogel structures. They exhibit distinct movement patterns: the tadpole robot achieves an average swimming speed of 0.48 mm/s through tail-wagging motion, the legged tadpole robot reaches a swimming speed of 1 mm/s via leg-kicking propulsion, and the frog robot jumps to a height of 14 mm under visible light stimulation. This work is of great significance for developing hydrogel-based bionic robots, providing valuable insights into the design of visible light-driven robotic systems.