Control of spatio temporal mode-switching at a membrane or an interface under nonequilibrium condition

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As a simple example of an autonomous motor, the self-motion of a camphor boat on water with changes in chemical stimuli was investigated. For example, 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 distance 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.As for another system, the propagation of chemical waves in the photosensitive Belousov-Zhabotinsky (BZ) reaction was investigated using an excitable field in the shape of a circular ring or figure "8" which was drawn by computer software and then projected on a film soaked with BZ solution using a liquid-crystal projector. For a chemical wave in a circular reaction field, the shape of the chemical wave was investigated depending on the ratio of the inner and outer radii. When two chemical waves were generated on a field shaped like a figure "8" (one chemical wave in each circle) as the initial condition, the location of the collision of the waves either was constant or alternated depending on the degree of overlap of the two circular rings. These experimental results were analyzed based on a geometrical discussion and theoretically reproduced based on a reaction-diffusion equation using a modified Oregonator model. The photosensitive BZ reaction may be useful for creating spatio-temporal patterns depending on the geometric arrangement of excitable fields.