Stacking nematic elastomers for artificial muscle applications

Abstract

Nematic liquid crystal elastomers are thermally actuated to produce macroscopic, anisotropic shape changes. Uniaxial contraction and extension of liquid crystal elastomers can be achieved by cycling the temperature of the material through the nematic to isotropic phase transition. In this report, a new approach is introduced by layering liquid crystal elastomer films to create thermally actuated stacks. A heating element and thermally conductive grease embedded between elastomer films provide a means for rapid internal heat application and distribution when a current is passed through the heating element, thus providing contractile force production in a minimal amount of time. Upon voltage application, stacks composed of two 100 μm-thick films and a single heating element produce 18% strain between contracted and relaxed states. In addition, the stacked elastomer films are capable of producing 10% contraction within 1 s and the blocked stress of the thermally actuated stacked films is calculated to be 130 kPa. The stacking approach provides new opportunities to use liquid crystal elastomers in applications requiring forces greater than those capable of being produced by single elastomer films.