Characteristic self-motion of a camphor boat sensitive to ester vapor

As a simple example of an autonomous motor, the self-motion of a camphor boat on water with changes in chemical stimuli was investigated. The nature of the self-motion of a camphor boat changed characteristically with the addition of ester vapor (methyl n-butyrate) to a circular water chamber. Thus, continuous motion changed to oscillatory motion, and its period increased depending on the location between an ester droplet and the chamber, L. The surface tension in the water chamber was measured to clarify how the velocity of the self-motion changed with L. The nature of the self-motion is discussed in relation to the surface tension as the driving force. We believe that the present results may be useful for realizing artificial chemotaxis systems under nonlinear and isothermal conditions.