Swimmers at liquid/air interfaces have drawn enormous attention because of their potential applications. Described herein is one novel light-driven swimmer based on ab imorph composite structure of ap hotoresponsive liquidcrystalline polymer network and ac ommercially available polyimide (Kapton). The motion of the swimmer can be controlled by photoirradiation. The bilayer-structured film shows quickly photoinduced bending towards the Kapton side upon exposure to UV light, and recovers immediately after removal of light. When placed on aliquid surface,the swimmer propels itself continually though rhythmic beating the liquid like ad olphin moving forward with its tail fin. Besides,l ightpowered rotation of the swimmer is successfully achieved by simply changing the length-width ratio and the irradiation site, mimicking the function of adolphinspectoral fin. Combining the forward movement and rotation motion together,o ndemand directional control of the photo-driven swimmer can be readily obtained at room temperature,showing promise for miniaturized units for transportation.

A programmable and biomimetic bilayer actuator enabled by a photo-liquefiable azobenzene derivative.

A series of photomechanical fibers was fabricated with a thermal drawing method by using liquid-crystalline random copolymers containing azobenzene and biphenyl groups in side chain. After being post-cross-linked under mild conditions, these fibers showed photoinduced bending motion away from the light source even though homogeneous alignment of mesogens was observed along the drawing direction. This abnormal photoinduced deformation of the obtained fibers is far different from previously reported light-directed motions about liquid-crystalline fiber and film materials. The interesting photomechanical deformation can be ascribed to the surface volume expansion caused by photoisomerization of azobenzene moieties. Then the photoinduced bending behaviors of these fibers containing different azobenzene concentrations and cross-linking densities were systematically investigated, suggesting that the location of photoresponsive azobenzene played an important role in deciding their photomechanical behaviors. This provides one convenient way of controlling over the photoinduced bending direction through the location of light-active moieties in side chain or cross-linker. In addition, irradiation of visible light accelerated the recovery of bent fibers. These fibers possess quick response, large deformation, and good thermal stability, indicating their promising applications for smart devices and energy conversion devices.