Experimental and numerical investigation on a simple droplet coalescence design in microchannels

Abstract

A simple, low-cost and reliable method for the formation of temperature-induced droplet coalescence is proposed and demonstrated experimentally and numerically. The formation process consists of two steps: (1) the formation of water-in-oil droplets at the flow-focusing junction and (2) the formation of temperature-induced droplet coalescence in the merging chamber by a resistive heater. Since the droplets flows from directly from the first step to the second step in the microchannel without any disturbance, problems such as droplet breakup, leakage and contamination can be avoided. The merging process of two neighboring droplets was investigated by adjusting the applied voltage, flow rate ratio between water and oil and total flowrate. In the simulation, the flow in the process of droplet coalescence is simulated using the Finite Volume Method, and the interface is captured using the Level Set Method. The presented technique could be used for merging and mixing in droplet-based lab-on-a-chip platforms.