RADIUS-DEPENDENT INHIBITION AND ACTIVATION OF CHEMICAL OSCILLATIONS IN SMALL DROPLETS

The oscillatory dynamics in droplets of the ferroin-catalyzed Belousov -Zhabotinsky solution is investigated. Due to a diffusive influx of mo lecular oxygen from a surrounding hydrophobic phase, droplets experien ce an increase in oscillation period with decreasing drop radius. If t he radius is smaller than approximately 1.5 mm, no oscillations are ob served. The phase of oscillations showed a radial dependence that give s rise to nontransient phase waves propagating from the center outward . In the absence of oxygen, the period decreases slightly with decreas ing drop radii. A simple geometrical analysis qualitatively explains t he main experimental observations. The analysis stems from an approach that relates the efficiency of inhibition to the surface-to-volume ra tio of droplets.