Polymer solutions and solids that contain light-sensitive molecules can undergo photo-contraction, whereby light energy is converted into mechanical energy. Here we show that a single film of a liquid-crystal network containing an azobenzene chromophore can be repeatedly and precisely bent along any chosen direction by using linearly polarized light. This striking photomechanical effect results from a photoselective volume contraction and may be useful in the development of high-speed actuators for microscale or nanoscale applications, for example in micro-robots in medicine or optical microtweezers. We prepared the films by thermal polymerization of a liquid-crystal monomer (molecule 1 in Fig. 1a) and a diacrylate crosslinker (molecule 2) (9:1, mol/mol), both of which possess azobenzene moieties. Figure 1b shows a sequence of frames indicating how such a film can be bent along a precisely controlled direction by irradiation with linearly polarized light (for movies, see supplementary information).
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