Bimodal photothermal-driven self-sustained oscillator based on MXene structure

Soft robots capable of autonomous, continuous, fast, and adjustable motion speeds under constant external stimuli have great potential in environmental, industrial, military, and medical fields. Aiming at the difficulties of existing self-oscillators, including small oscillation range, difficulty of achieving non-reciprocal motion, and the slow forward speed of the resulting self-sustained soft robots. In this paper, a sunlight-driven self-oscillator based on MXene is prepared. By employing a bimorph structure and thermal regulation process, the self-oscillator exhibits two distinct oscillation modes: 'elastic' and 'plastic' deformation. These modes can be modulated within the same film by varying the light power. A broader amplitude range (3.6–302.3°, 3.3 times that of the existing studies) is achieved by attaching a load to the film's end to enhance the inertial force of movement. Non-reciprocal motion in both modes and stable oscillations in sunlight are achieved. Finally, a light-driven sailboat model is developed. The sailboat can achieve autonomous light-forward motion with a speed of up to 12.8 body length per minute (2.1 times that of existing studies), with its propulsion mechanism further explained through numerical simulation results. This research provides new strategies for constructing fast and large-amplitude self-oscillators and demonstrates the potential for applications in speed-adjustable autonomous forward devices.