Light-induced displacement of a microbead through the thermal expansion of liquid crystals

We found the displacement of a microbead by the oblique irradiation of UV light in pure 4-cyano-4'-pentylbiphenyl (5CB) without photo-responsive molecules. This system is very simple and a complicated experimental setup is not necessary. The displacement is observed in the nematic state of 5CB and not in the isotropic state. The distance of the displacement was proportional to the intensity of the UV light. After the irradiation was stopped, the microbead started to return to the original position. These phenomena are attributed to the thermal expansion of 5CB induced by the photo-thermal effect of polyimide coated on the glass substrate.