Shaping and Locomotion of Soft Robots Using Filament Actuators Made from Liquid Crystal Elastomer–Carbon Nanotube Composites

Abstract

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.

Amine‐Acrylate Liquid Single Crystal Elastomers Reinforced by Hydrogen Bonding

“…Given that the alignment techniques conducted at smaller scales were nonetheless demanded for action versatility, an increasingly popular 3D printing approach [32][33][34][35][36][37] based on shear alignment of LC was also investigated. As previously mentioned, the processing window for oligomers as "liquid ink" could endure for as long as 1 h. When the viscous LC oligomer was extruded out of the syringe equipped with a mechanical piston, molecular rearrangement by the shear flow would yield a reasonably well-aligned LC filament as indicated by its transparency.…”

NIR–vis–UV Light‐Responsive High Stress‐Generating Polymer Actuators with a Reduced Creep Rate

“…The resulting stress-generating actuators are fast (<0.8 s) and can be repeatedly and reversibly driven with NIR, blue, and UV lights. The maximum specific actuation stress (35)(36)(37)(38)(39)(40)) was achieved at a draw ratio of 70. The stable photoinduced stress with reduced stress relaxation was obtained due to the reduced chain slip in the plastic region of ultradrawn composite films.…”

Innervated, Self‐Sensing Liquid Crystal Elastomer Actuators with Closed Loop Control

“…Liquid crystal elastomers (LCEs) are soft active materials that are being widely developed for soft robotics, [ 1–5 ] actuators, [ 6–9 ] and shape shifting architectures. [ 10–12 ] They are composed of a crosslinked polymer network that contains rigid mesogens, which actuate when heated above their nematic‐to‐isotropic transition temperature ( T NI ), [ 13,14 ] exposed to light, [ 15–17 ] or chemical gradients.…”