Ringlike Migration of a Droplet Propelled by an Omnidirectional Thermal Gradient.

The interfacial phenomenon associated with the ringlike motion of a liquid droplet subjected to an omnidirectional thermal gradient is investigated. An experimentally verified model is proposed for estimating the droplet migration velocity. It is shown that the unbalanced interfacial tension acting on the liquid in the radial direction provides the necessary propulsion for the migration, whereas the internal force acting on the adjoining liquid contributes to the equilibrium condition in the circumferential direction. This study puts forward the understanding of the interfacial spreading phenomenon, the knowledge of which is important in applications where liquid lubricants are encountered with directionally unstable thermal gradients.