Soft robots, with their agile locomotion and responsiveness to environment, have attracted great interest in recent years. Liquid crystal elastomers (LCEs), known for their reversible and anisotropic deformation, are promising candidates as embedded intelligent actuators in soft robots. So far, most studies on LCEs have focused on achieving complex deformation in thin films over centimeter‐scale areas with relatively small specific energy densities. Herein, using an extrusion process, meter‐long LCE composite filaments that are responsive to both infrared light and electrical fields are fabricated. In the composite filaments, a small quantity of cellulose nanocrystals (CNCs) is incorporated to facilitate the alignment of liquid crystal molecules along the long axis of the filament. Up to 2 wt% carbon nanotubes (CNTs) is introduced into a LCE matrix without aggregation, which in turn greatly improves the mechanical property of filaments and their actuation speed, where the Young's modulus along the long axis reaches 40 MPa, the electrothermal response time is within 10 s. The maximum work capacity is 38 J kg−1 with 2 wt% CNT loading. Finally, shape transformation and locomotion in several soft robotics systems achieved by the dual‐responsive LCE/CNT composite filament actuators are demonstrated.
Liquid crystal elastomers (LCEs), owing to their intrinsic anisotropic property and capability of generating programmable complex morphologies under heat, have been widely used for applications ranging from soft robotics, photonic devices, cell culture, to tissue engineering. To fulfill the applications under various circumstances, high actuation efficiency, high mechanical strength, large heat and electrical conductivity, or responses to multiple stimuli are required. Therefore, design and fabrication of LCE composites are a promising strategy to enhanced physical properties and offer additional stimuli responses to the LCEs such as light, electric, and magnetic fields. In this review, we focus on recent advances in LCE composites, where LCEs are defined as anisotropic elastomeric materials in a broader context. Classic LCE composites with metallic nanoparticles, magnetic particles, liquid metal, carbon nanotubes, graphene and its derivative, and carbon black, and LCE composites from cellulose nanocrystals within the polymer network where cellulose can provide the unique liquid crystal anisotropy will be discussed. We conclude with the challenges and future research opportunities.
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