Autonomous motion of droplet powered by chemical potential and by photon-flux

Living organisms maintain their lives through the dissipation of chemical energy under isothermal conditions. They transduce chemical energy into macroscopic motion with high efficiency, but the mechanism is not fully understood yet. By considering experimental model systems together with experimental results reported for the molecular machinery, it would be possible to attain an essential understanding of mechanism on the chemo-mechanical energy transduction in living organisms. In the present paper, we introduce several simple experimental systems where spontaneous motion of a droplet is induced by chemical energy gradient or by photon flux.