Many biological materials derive function from spatial and hierarchical control of structure and composition. This structure is particularly critical at the interfaces between rigid and compliant tissues, such as tendon and bone. Programmable control of shape, modulus and other properties is needed to better interface relatively simple synthetic materials with complex natural tissues. Liquid crystal elastomers are well known to exhibit anisotropic mechanical properties and have been widely studied for the coupling of the nematic director to mechanics. This coupling results in unique behaviors such as soft elasticity and actuation. However until recently, nearly all of these materials have been aligned uniaxially. By directing the self-assembly of liquid crystal elastomers, the highly anisotropic mechanical properties, including thermally induced shape change and elastic modulus, exhibited by these materials can be designed in 2D (<b>Figure</b>). These materials can be designed to reversibly change shape with over 50% strain in response heat or solvent. In this work, we leverage recent results in surface-aligned liquid crystal elastomers to demonstrate that mixtures of liquid crystal monomers can be used to spatially align anisotropic microparticles, yielding multifunctional composites. The effect of aligned fillers, such as silicon carbide whiskers, on shape change and modulus is explored. Furthermore strategies to enable liquid crystalline hydrogels that change shape in response to changes in physiological conditions will be described. These liquid crystal elastomer composites provide a strategy towards mimicking the multifunctionality of highly complex biological materials. It is expected that these active, designed monoliths may be leveraged in applications such as coatings for implantable devices.

Liquid crystal elastomer composites with aligned, anisotropic fillers as multifunctional actuators

251st National Meeting (2016)

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