An Axisymmetric Flow‐Focusing Microfluidic Device

An axisymmetric flow-focusing microfluidic device (AFFD) is described. The AFFD (see Figure, top) produces micrometer-sized (50–300 μm) polymer-coated droplets (see Figure, bottom) with narrow size distributions (< 5 %). The axisymmetric geometry confines droplets to the central axis of the channel and prevents them from being sheared or damaged at the channel walls. The device is used to prepare aqueous droplets encapsulated in nylon-6,6 membranes by carrying out interfacial polymerization reactions in situ.