Multi-stimuli responsive bionic actuators constructed by linear liquid crystal polymers

Liquid crystal polymers (LCPs) combine the entropic elasticity of polymers with the orderness of LC mesogens, demonstrating outstanding performance across diverse applications, particularly in bionic actuators. In contrast to the organisms that enable multi-stimuli responsibility, most LCP actuators reported thus far exhibit responsiveness to only a single stimulus, hence the fabrication of multi-stimuli responsive LCPs is of pronounced significance. Here, a novel multi-stimuli responsive LCP is developed by integrating ring-opening metathesis polymerization (ROMP) and post-polymerization modification (PPM), which exhibits reversible responsiveness to humidity, light, and pH. By spray-coating the stretched polypropylene with LCP, the bilayer actuator loads exceed 20 times its weight upon exposure to light irradiation and moisture, showcasing exceptional output force. Furthermore, in response to the change in pH and humidity, the actuator exhibits behaviors akin to natural flowers, including blooming, closing, and color-changing. The strategy combining ROMP and PPM has proven to be a versatile strategy for the synthesis of multifunctional LCPs, offering transformative potential for the development of advanced bionic actuators and soft robotic systems.