A Soft Actuator with Simultaneous Ultra-High Actuation Strain and Power Density Under Human-Safe Stimuli.

Abstract

Diverse soft robotic applications, such as wearable devices, haptic interfaces, artificial muscles, and biomedical systems, require soft actuators to simultaneously deliver large actuation strain (>40%) and high power density (>323 W kg^-1) in response to mild, human-safe stimuli. However, no existing soft actuator system has successfully met these combined requirements. To address this critical gap, body-temperature-responsive liquid crystalline elastomer (LCE) films are designed with a thickness direction orientation gradient achieved through macromolecular engineering of lightly crosslinked gels during the initial stage of network formation. Using ultrahigh stretch ratios to 2000% and with controlled entropic recovery, the degree of molecular orientation through the film thickness can be established. As a result, the fully crosslinked monodomain LC soft actuator simultaneously provides a high actuation strain of 88% and a high power density of 1960 W kg^-1 under body-temperature stimulation, a level of performance unmatched by existing actuators sensitive to mild stimuli. Device-level demonstrations, including a rotary soft robot and an intelligent safety switch, highlight the actuator's versatility and potential for real-world integration in next-generation soft robotic systems.