Self-assembly of coated microdroplets at the sudden expansion of a microchannel

Abstract We report observations of the self-assembly coated droplets into regular clusters at sudden expansion a microfluidic channel. A double emulsion consisting train microdroplets was created upstream channel expansion, so that inter-drop distance, droplet length, velocity and coating thickness could be varied by imposing different inlet pressures, albeit not independently. Provided enlarged remains sufficiently confined to prohibit propagation in file, can assemble sequentially linear expansion. Droplets join cluster via coalescence their film with group ahead. This occurs when approach each other within critical distance enabled hydrodynamic interactions train. Clusters comprising finite number are obtained because reconfiguration assembly during increases following droplet. Decreasing size up maximum value beyond which continuous form. Formalising these simple model reveals any possible but they occur for increasingly narrow ranges parameter values. Our experimental suggests background fluctuations limit discrete practice. method offers robust alternative flow focusing encapsulating multiple cores single potential build more complex colloidal building blocks de-confining clusters.