Change in the mode of spontaneous motion of an alcohol droplet caused by a temperature change

Abstract

An alcohol (pentanol) droplet exhibits spontaneous motion on an aqueous solution, driven by a solutal Marangoni effect. We found that the mode of such droplet motion changes depending on the temperature of the aqueous phase. When the temperature of the aqueous phase is 20°C, a droplet with a volume of 1 μl exhibits vectorial motion, whereas when the temperature is 25°C, the droplet exhibits irregular motion. We discuss the mode change in relation to the solubility of pentanol in water.