Pressure drop analysis for the droplet break-up flow in a locally constrictive microchannel

Abstract

Locally constrictive microchannels are effective components to implement droplet break-up in microfluidic processes. We herein report an experimental study of droplet break-up flow based on pressure drop analysis. The time varying pressure drops were recorded by a self-assembled experimental platform with measurement accuracy of 1 Pa, and the variations of those pressure drops were in accord with the fluctuations of capillary pressure. Fourier transform was then employed to analyze the droplet break-up behaviors and confirm the numbers of daughter droplets instead of traditional microscopic imaging method. With the guidance of the pressure drop analysis, the effects of crucial factors such as surfactant concentration, fluid flow rate, and fluid viscosity on droplet break-up were investigated. The additional hydrostatic energy cost for droplet stretching and deformation in the constriction was finally discussed in contrast to the increase of interfacial energy, which were both confirmed on the level of 10−8 J/droplet.