Self-oscillating Gel Accelerated while Sensing the Shape of an Aqueous Surface.

The reciprocating motion of a self-oscillating square gel induced by the Belousov-Zhabotinsky (BZ) reaction was investigated on an aqueous surface. The chemical wave propagated from the side at which the oxidation of the Ru catalyst in the gel started. As the chemical wave propagated, the gel moved in either the opposite (mode I) or the same (mode II) direction as the chemical wave propagation. The gel then went back as the Ru catalyst in the gel was slowly reduced. We examined the relationship between the modes of motion (mode I or II) and the shape of the aqueous BZ solution surface. The mode selection was discussed in relation to the contact angle around the gel which was changed by the BZ reaction, i.e., the lateral imbalance of surface tension and the capillary interaction.