Multimodal and Multistimuli 4D-Printed Magnetic Composite Liquid Crystal Elastomer Actuators

 

Liquid crystal elastomer (LCE)-based soft actuators are being studied for their significant shape-changing abilities when they are exposed to heat or light. Nevertheless, their relatively slow response compared with soft magnetic materials limits their application possibilities. Integration of magnetic responsiveness with LCEs has been previously attempted; however, the LCE response is typically jeopardized in high volumes of magnetic microparticles (MMPs). Here, a multistimuli, magnetically active LCE (MLCE), capable of producing programmable and multi-modal actuation, is presented. The MLCE, composed of MMPs within an LCE matrix, is generated through extrusion-based 4D printing that enables digital control of mesogen orientation even at a 1:1 (LCE:MMPs) weight ratio, a challenging task to accomplish with other methods. The printed actuators can significantly deform when thermally actuated as well as exhibit fast response to magnetic fields. When combining thermal and magnetic stimuli, modes of actuation inaccessible with only one input are achieved. For instance, the actuator is reconfigured into various states by using the heat-mediated LCE response, followed by subsequent magnetic addressing. The multistimuli capabilities of the MLCE composite expand its applicability where common LCE actuators face limitations in speed and precision. To illustrate, a beam-steering device developed by using these materials is presented.