Temperature-induced migration of a bubble in a soft microcavity

We perform studies of pancake-like shaped bubbles submitted to a temperature gradient in a micrometric height Hele-Shaw cell. We show that under the experimental conditions, usually found in microfluidic devices, the temperature-induced dilation of the cavity overcomes the thermocapillary convection due to surface tension variation, effectively driving the bubble toward the cold side of the cavity. The bubble velocity is experimentally characterized as a function of the bubble radius, the temperature gradient, and the initial Hele-Shaw cell thickness. We propose a theoretical prediction of the bubble velocity, based on the analytical resolution of the hydrodynamical problem. The equations set closure is ensured by the pressure value near the bubble and by the dissipation in the moving meniscus.