A Novel Droplet\nSieving Method Using an Array Protrusion\nMicrochannel and Separation Mechanism

A novel droplet separation method\nwas proposed by using\nan array\nprotrusion microchannel, which could divert droplets of different\nsizes into designated branch channels. The performance and mechanism\nof droplet sieving were investigated. In this work, three distinct\nflow patterns were obtained: partial sieving, complete sieving, and\nmain drop loss regimes. The influences of droplet length and operation\nconditions on the sieving efficiency were studied systematically.\nIt was found that, in the partial sieving flow pattern, the increase\nof small droplet diameter is not conducive to sieving, and there exists\na critical diameter of the small droplet for complete sieving under\na constant main droplet size, which relies primarily on the array\nprotrusion height. The operating range of the complete sieving flow\npattern extends when increasing the main droplet size, and the critical\ncapillary number for evolving into the main droplet loss flow pattern\nrises. The sieving efficiency increases with the flow rate of the\ncontinuous phase in the regulating channel while decreasing with that\nin the main channel.