Self-motion of a camphoric acid boat sensitive to the chemical environment

As a simple example of an autonomous motor, the characteristic patterns in the self-motion of a camphoric acid boat depending on the chemical environment were investigated at the air/aqueous interface. The uniform motion of a camphoric acid boat changed to intermittent motion and its period increased depending on the concentration of phosphate ions. The nature of the self-motion changed reversibly with the addition of chemical stimuli to the air/aqueous interface. The camphoric acid layer adsorbed on a mica surface was observed by atomic force microscopy (AFM) to investigate how the microscopic state of the camphoric acid layer varied with pH. The nature of the self-motion was reproduced by a numerical calculation in relation to the surface tension, which depends on the surface concentration of the camphoric acid layer.