Transparent programmable actuators based on MXene polymer composites: An approach to amphibious camouflage robots

Transparent actuators have significant potential in invisible and camouflage robots. However, traditional transparent actuators are typically unprogrammable and used in a single environment (on-land or in-water), which limits their working abilities in complex environments. Herein, we propose transparent actuators and robots that integrate amphibious actuations, programmable motions, self-healing function and camouflage function together. The actuator is composed of MXene polymer composites, including bone glue, gelatin, MXene (BGGM) and polyethylene terephthalate (PET). The transmittance of BGGM/PET actuator is >80 % at 600 nm wavelength, exhibiting high transparency. On one hand, the actuator shows a light-driven bending deformation on land due to the photothermal effect. Synergistic combination of the self-healing of BGGM and the shape-fixing of PET allows the spatial-programming of actuator to demonstrate light-driven complex deformations. On the other hand, the actuator can be driven by Marangoni effect on water by using BGGM composite as fuels. Adding functional modules enables the spatial-temporal programming of the actuator, so the actuator can showcase time-varying trajectories. Finally, we demonstrate a transparent swimming robot with dual-actuation modes and a transparent actuator that conveys invisible information stealthily while moving through a complex maze on water. This research offers a promising approach to camouflage amphibious robots.