Bi-Directional Deformation, Stiffness-Tunable, and Electrically Controlled Soft Actuators Based on LCEs 4D Printing

Abstract

The integration of 3D printing with smart materials in 4D printing technology has attracted extensive research attention due to its capability of endowing static printed structures with dynamic behaviors and actions that evolve over time. One such promising smart material is liquid crystal elastomers (LCEs), which offer excellent reversible actuation performance and programmable anisotropy. However, the field of LCEs-based 4D printing faces challenges in achieving sufficient mechanical performance due to their low elastic modulus, which hinders their ability to handle tasks requiring relatively high load-bearing capacity. Moreover, there are also challenges related to their complex actuation environments, which further restrict the applications based on LCEs. In this work, we propose a paradigm for designing and manufacturing electrically-controlled soft actuators capable of reversible deformation and adjustable stiffness. Specifically, we integrate LCEs with continuous fiber-reinforced polymer composites (CFRP) and elastomeric materials into a multilayer sandwich structure. By combining CFRP, we significantly enhance the stiffness of the actuators without compromising their flexibility and adaptability. Furthermore, the inclusion of continuous carbon fibers (CCF) enables electrical control of the actuators. Finally, by incorporating pre-stretched elastomeric materials, we fabricate an electrically-controlled actuator with excellent mechanical performance and reversible actuation capabilities. As a demonstration, we create an intelligent soft gripper with outstanding mechanical performance and reversible actuation, exhibiting high load-bearing capacity and shape adaptability.