Light-driven Crawling of Molecular Crystals via Phase-dependent Transient Elastic Lattice Deformation.

The light-driven crawling of a molecular crystal that can form three phases, (alpha, beta, and gamma) is presented. Laser irradiation of the molecular crystal can generate phase-dependent transient elastic lattice deformation. The resulting elastic lattice deformation that follows scanning irradiation of a laser can actuate the different phases of molecular crystal to move with different velocity and direction. Because the gamma phase has a large Young's modulus (ca. 26 GPa), a force of 0.1 mu N can be generated under one laser spot. The generated force is sufficient to actuate the gamma-formed molecular crystals in a wide dimensional range to move longitudinally at a velocity of about 60 mu m min(-1), which is two orders of magnitude faster than the alpha and beta phases.