(79d) Controlling the Energy Landscape of Actuators through Independent Stimuli.

Over millennia of evolution nature has mastered the ability to control complex energy landscapes enabling cells or proteins to continuously modulate and change their activity based on the input of multiple independent stimuli. Emulating such materials particularly for soft-material actuators promises high degree of functionality while minimizing the number of required inputs.

Synthetically however most materials used – such as liquid crystal elastomers (LCEs) – are based on binary systems where one input results in one specific output with orthogonality providing more complex systems. In LCEs actuation is based on a single-phase transition providing the amplification of a molecular reorientation to a macroscopic shape change. This limits complex motion to be based on careful control of alignment or introduction of patternable input-output systems. Achieving continuous dynamic mechanical response maps to a combination of stimuli within a single material system would vastly widen the synthetic design space.

Here we present a liquid crystal elastomer system with multiple ordered phases. By introducing order to order transitions this system accesses molecular control over position and orientation of molecules. By externally interacting with the phase space, we can travers a three-dimensional energy landscape through two independent stimuli. Using this system in magnetically aligned photoresponsive micropillar actuators we can control both directionality and extent of motion by combining light and heat. This system then can be further adjusted by controlling alignment, mechanical properties and geometry of both material and stimuli. This concept adds another dimension to design actuators promising applications needing multifunctional outputs, environmentally adaptive systems and life-like materials.