The generation of convective flow by a chemical wave was studied experimentally on a mm-sized droplet of Belousov-Zhabotinsky ͑BZ͒ reaction medium. A propagating chemical wave causes a transient increase in interfacial tension, and this local change in interfacial tension induces convection. The observed flow profile was reproduced with a numerical simulation by introducing the transient increase in interfacial tension to a modified Navier-Stokes equation coupled with a chemical kinetic equation; a modified Oregonator. We also observed the periodic motion of a BZ droplet floating on an oil phase. Such periodic motion is attributed to the rhythmic change in interfacial tension. The observed periodic convective motion coupled with a chemical reaction is discussed in relation to chemo-mechanical energy transduction under isothermal conditions.

The spatiotemporal chemical structure in the Belousov−Zhabotinsky (BZ) reaction was studied using spherical beads of ion-exchange resin doped with ferroin by changing the size of the beads. Above an upper critical size (ca. 0.8 mm in diameter), chemical waves emerge and propagate on the surface of a bead by forming a target or spiral pattern. Below a lower critical size (ca. 0.62 mm in diameter), uniform global oscillation over the entire bead is observed; i.e., no traveling wave is observed. Between these upper and lower critical sizes, the reaction is bistable with regard to the two different modes, i.e., uniform oscillation and a traveling wave. This experimental trend is discussed in terms of competition between the growth rate and diffusion rate of the activator.

We examined chemical oscillations in the Belousov−Zhabotinsky (BZ) reaction with spherical ion-exchange resin beads (radius:  0.1−0.4 mm) loaded with a cationic catalyst, ferroin, in which no traveling wave appears and the oscillation is synchronized over individual beads. The period of the oscillation increases with a decrease in the size of the beads. Based on a theoretical consideration of the effect of the diffusion of active species through the surface of the bead reactor into the bulk aqueous solution, the following relationship was deduced:  f/[H2SO4]γ ∝ (1 − η/R) where f is the frequency (Hz) of the oscillation, R is the radius (mm) of the beads, [H2SO4] is the concentration (mol/dm3) of sulfuric acid, andγ and η are constants. This relationship was consistent with experimental results with values of γ = 1.4 and η = 7.4 × 10-4.