Harnessing the power of light with photomechanical materials

Abstract

We study the mechanisms of the photomechanical response of dye-doped polymers and liquid crystal elastomers by characterizing the stress/strain response function to modulated light of a variety of material compositions with the specific goal of optimizing the photomechanical response Figure of Merit (FOM), which quantifies the efficiency with which light energy is converted to mechanical work. We discuss experiments that vary the parameters, which define the FOM to study the underlying mechanisms. Large and dramatic length changes and bending angles are commonly observed in materials with a small Young’s modulus even when the light-induced stress is small. However, useful devices require large forces, which may not always lead to large displacements in stiff materials. We use the concept of a photomorphon, the smallest photomechanical material element, to guide in the design of the most efficient materials and describe the photomechanical analog of the optical transistor.