Photo-responsive doped cholesteric liquid crystals

Nanomachines of the future will require molecular-scale motors that can perform work and collectively induce controlled motion of much larger objects. We have designed a synthetic, light-driven molecular motor that is embedded in a liquid-crystal film and can rotate objects placed on the film that exceed the size of the motor molecule by a factor of 10,000. The changes in shape of the motor during the rotary steps cause a remarkable rotational reorganization of the liquid-crystal film and its surface relief, which ultimately causes the rotation of submillimetre-sized particles on the film.

The design of molecular systems in which controlled linear and rotary motion can be achieved under the influence of an external signal is a major endeavor toward future nanoscale machinery. In this Account we describe the development of molecular switches and the discoveries that culminated in the first light-driven molecular motor. Various chiral optical molecular switches and their use as trigger elements to control organization and functions will be discussed. The construction of the first and second generation molecular motors is presented.