Ultra-Soft Organogel Artificial Muscles Exhibiting High Power Density, Large Stroke, Fast Response and Long-Term Durability in Air.

Abstract

Polymeric gel-based artificial muscles exhibiting tissue-matched Young's modulus (10 Pa-1 MPa) promise to be core components in future soft machines with inherently safe human-machine interactions. However, the ability to simultaneously generate fast, large, high-power, and long-lasting actuation in the open-air environment, has yet been demonstrated in this class of ultra-soft materials. Herein, to overcome this hurdle, the design and synthesis of a twisted and coiled liquid crystalline glycerol-organogel (TCLCG) is reported. Such material with a low Young's modulus of 133 kPa can surpass the actuation performance of skeletal muscles in a variety of aspects, including actuation strain (66%), actuation rate (275% s^-1 ), power density (438 kW m^-3 ), and work capacity (105 kJ m^-3 ). Notably, its power density is 14 times higher than the record of state-of-the-art polymeric gels. No actuation performance degradation is detected in the TCLCG even after air exposure for 7 days, owing to the excellent water retention ability enabled by glycerol as co-solvent with water. Using TCLCG, mobile soft robots with extraordinary maneuverability in unstructured environments are successfully demonstrated, including a crawler showing fast bidirectional locomotion (0.50 mm s^-1 ) in a small-confined space, and a roller that can escape after deep burying in sand.