MXene/VO@PMMA Composite Film Multi-responsive Actuator with Amphibious Motion.

This work introduces a novel composite film actuator with dual actuation mechanisms, responsive to four distinct stimuli, and featuring infrared stealth as well as amphibious locomotion capabilities. By encapsulating nanoscale VO phase-change materials with PMMA and coating them onto a thin film of micrometer-scale TiCT MXene, the composite film achieves efficient photothermal conversion, high electrical conductivity, and humidity-responsive actuation. The composite film is integrated into millirobots capable of crawling, grasping, oscillating, and achieving unrestricted movement on water surfaces. These millirobots demonstrate rapid response, high stability, and outstanding performance in both terrestrial and aquatic environments, with a 90° angular change in 3 s, a crawling speed of 10 mm min on land, and a swimming speed of 174 mm min in water. Additionally, this work proposes a novel actuation mechanism based on the moisture absorption and contraction properties of MXene, further expanding the application potential of millirobots. These advancements enable the millirobots to navigate confined spaces and transport sensitive items without being detected by infrared sensors. This work represents a substantial leap forward in soft robotics and materials science, paving the way for further exploration of advanced composite materials tailored for complex applications.