Nanocellulose Incorporated Liquid Crystal Elastomers as Soft Actuators

Liquid crystal elastomers (LCEs) are potential soft actuators that exhibit spontaneous reversible shape transformation with a substantial dimensional change. High strength, multiple controls over actuation, and faster response times are key parameters for the successful practical application of LCEs. In this work, we explored the influence of cellulose nanocrystals (CNCs) as fillers in LCEs to improve their strength without compromising the elasticity and liquid crystal properties. This study demonstrated that incorporating a certain amount of CNCs into LCEs can produce a soft actuator composite having high mechanical strength, a multi stimuli response (thermal and light-induced thermal actuation), and the ability to lift heavy objects. Five different wt %'s of CNCs (0.01–0.05 wt %) having an aspect ratio of ∼3.6 were incorporated during the preparation of the elastomer to obtain the composites. The impact of the CNCs on the mechanical, actuation, and weight-lifting properties of the composites was studied. All of the composite films displayed LC properties and good thermal stability. Despite the presence of CNCs, all of the composite films showed good thermal actuation. Among the composite films, the LCE containing 0.02 wt % displayed a maximum ultimate stress of 1.99 MPa and a total elongation of 62.9%. This film displayed a shrinkage of 23% during heating. By using an incandescent bulb source for light-induced thermal actuation, the film was able to lift 300 g of weight, which is 1288 times its initial weight. We highlight that the LCE-CNCs composite film (0.02 wt %) has excellent mechanical stability, shape memory properties, and weight-lifting capability that can be beneficial for artificial muscles and soft robotics.