Efficient coalescence of microdroplet in the cross-focused microchannel with symmetrical chamber

A cross-focused microchannel with symmetrical chamber is constructed to improve coalescence efficiency of droplets. The flow behavior of droplets and time scale are investigated experimentally. Results show that the flow patterns could be divided into four regimes: long droplet, multiple coalescence, double coalescence and non-coalescence. Moreover, the evolutions of deformation value and rotation angle of droplets are studied to understand the mechanism of droplets coalescence. Asynchronous coalescence could appear in this configuration on account of the existence of stagnancy time. The dimensionless liquid drainage time declines exponentially with the dimensionless velocity of continuous phase. The present configuration allows droplets to coalesce asynchronously, which greatly expands applicable operation region and accordingly facilitates the controllability of droplets coalescence.