Controllable microfluidics through active droplets

Precise, localized flow control in microfluidic devices remains a difficult challenge. In this paper we demonstrate, theoretically, how active droplets might be harnessed to overcome this challenge. Active droplets are produced along the microchannel wall via stimulation of a responsive hydrogel, and the ensuing phoretic slip flows drive transport and mixing in the microfluidic device. We find optimal transport times for particles traversing the channel, and show that, by switching between two droplet configurations, chaotic mixing can be achieved.