Multi-stimulus responsive shape memory polyurea incorporating stress-mismatching structure for soft actuators and reversible deployable structures

Shape memory polymer (SMP) has demonstrated practical applications, including aerospace structures, medical devices, and flexible electronics. The programmability and controllability provide essential convenience for many device applications. Imperfectly, once a programmed temporary shape is deployed into a permanent shape, it cannot recover to the programmed shape without being reprogrammed. Here, through differential thermal expansion material synergistic design constructing stress-mismatching structure. The bilayer actuator is constructed, featuring excellent mechanical strength and toughness, responsive to light, humidity and electric field. The multi-dimensional cross layer of carbon material and intrinsic humidity response of shape memory polyurea (SMPU) is an active layer and PET is a passive layer. The bilayer actuator bends 140 degrees within 5 s under 30 V voltage and recovers quickly within 20 s. Controlling the angle of light, the wheeled robot could crawl back and forth 20 cm, also achieving the bionic actuators, and deployable structures with an automatic roll-unfold.