  Liquid crystal elastomers are rubbers with liquid crystal order. They
contract along their nematic director when heated or illuminated. The shape
changes are large and occur in a relatively narrow temperature interval, or at
low illumination, around the nematic-isotropic transition. We present a
conceptual design of a mechanical, turbine-based engine using photo-active
liquid crystal elastomers to extract mechanical work from light. Its efficiency
is estimated to be 40%.
