An Electrically Actuated Soft Artificial Muscle Based on a High-Performance Flexible Electrothermal Film and Liquid-Crystal Elastomer

Liquid-crystal elastomer (LCE)-based soft robots and devices via an electrothermal effect under a low driving voltage have attracted a great deal of attention for their ability on generating larger stress, reversible deformation, and versatile actuation modes. However, electrothermal materials integrated with LCE easily induce the uncertainty of a soft actuator due to the non-uniformity on temperature distribution, inconstant resistance in the deformation process, and slow responsivity after voltage on/off. In this paper, a low-voltage-actuated soft artificial muscle based on LCE and a flexible electrothermal film is presented. At 6.5 V, a saturation temperature of 189 °C can be reached with a heating rate of 21 °C/s, which allows the soft artificial muscle quick and significant contraction and is suitable for untethered operation. Meanwhile, uniform temperature distribution and stable resistance of the flexible electrothermal film in the deformation process are obtained, leading to a work density of 9.97 kJ/m³, an actuating stress of 0.46 MPa, and controllable deformation of the soft artificial muscle. Finally, programmable low-voltage-controlled soft artificial muscles are fabricated by tailoring the flexible electrothermal film or designing structured heating pattern, including a prototype of soft finger-like gripper for transporting small objects, which clearly demonstrates the potential of low-voltage-actuated soft artificial muscles in soft robotics applications.