Spontaneous motion observed in highly sensitive surface relief formation system

Surface relief gratings formed on a liquid-crystalline azobenzene polymer film known as a highly sensitive system were investigated to obtain deeper insights into polymer migration on the micrometer scale. A surface relief formation was induced with incoherent nonpolarized patterned blue-light using a photomask instead of interference patterns of a coherent laser. Spontaneous lateral migration was observed under the edge of the grating photomask at room temperature even after terminating light irradiation. It was found that interfacial tension and the living cis form of azobenzene are essential for inducing spontaneous motion.