Surface tension and frictional resistance of thermocapillary pumping in a closed microchannel

This article investigates heat transfer and microfluidic forces on an enclosed droplet with thermocapillary pumping in a closed-ended microchannel. Numerical and theoretical formulations are developed to predict the droplet motion. Heat transfer through a silicon substrate to the droplet interface generates a thermocapillary force at the receding edge of the droplet. This thermocapillary force increases rapidly during a heating period, but decreases after the droplet moves past a thermal bridge. In the numerical formulation, a new pressure/velocity coupling is developed for the moving droplet/air interface. Close agreement between theoretical and predicted results of droplet displacement provides useful validation of the new formulations.