Microfluidic production of endoskeleton droplets with controlled size and shape.

Oil-in-water emulsion droplets, containing an elastic endoskeleton that holds the droplets in various non-spherical shapes, are formed by crystallizing a portion of the oil phase into a network of wax crystals. Such structures have recently been found to provide enhanced active ingredient delivery and shape-changing responsiveness, but robust methods of producing such droplets are needed that enable control of droplet size and shape. A continuous microfluidic flow is used here to produce endoskeleton droplets whose size is controlled by fluid flow rate and whose shape is varied between spheres, ellipsoids, and rods by control of exit temperature. A wide range of anisotropic shapes is produced using a single flow channel geometry by allowing the endoskeleton droplet to relax its deformation by varying degrees in response to fluid interfacial tension. Flexible production of shaped endoskeleton droplets will expand their application in enhanced delivery, deposition testing, and additive manufacturing processes.