Thermocapillary dipole in a Hele Shaw configuration

We present a theoretical and experimental study of thermocapillary flow in a Hele-Shaw cell containing a circular opening in the upper surface, and subjected to a linear temperature gradient. Under the assumption of shallowness (i.e. the depth of the reservoir is much smaller than its radius) we obtain a solution corresponding to a doublet flow (dipole) in the Hele-Shaw cell, providing good qualitative agreement with experimental results. We demonstrate how a superposition of dipoles can be applied for two-dimensional flow patterning, and how a confined dipole can act as a thermocapillary motor for driving liquids in microfluidic circuits. In addition, we show how the principles behind the thermocapillary dipole can be applied in order to drive thermocapillary surface swimmers on fluid-liquid interfaces