Oscillatory motion of a self-propelled object determined by the mass transport path

Oscillatory self-propulsion can be achieved under nonequilibrium conditions. In the case of a camphor boat, the periods of oscillatory motion were determined by the lateral (two-dimensional) transport length of camphor molecules at the solid plastic/water interface. However, the control of self-propulsion by different mass transport paths has not yet been explored. We observed new fluidic behaviors in the oscillatory motion of self-propelled objects. The period of oscillatory motion was determined by the mass transport path of the energy source molecules depending on the room temperature, T_r, and the temperature gradient, ΔT (= T_b - T_r, where T_b denotes the temperature at the bottom of the water chamber). We found that the oscillation period was determined by three types of mass transport paths for camphor molecules: lateral, downward, and complex. This study suggests that the three-dimensional transport path of energy source molecules can control the periods of oscillatory motion.