High-throughput-generating water-in-water droplet for monodisperse biocompatible particle synthesis

Water-in-water (W/W) droplets are biocompatible vessels for bioanalysis and biomolecules delivery. Due to the ultralow interfacial tension, the stable generation of W/W droplets still faces some challenges. In this paper, we present a robust and high-throughput microfluidic platform to fabricate W/W droplets without requiring external perturbation. Using the assembled evaporation pump, W/W droplets are generated uniformly and stably for nearly 1 h. The molecular weights, concentrations, and flow rates were changed to regulate the droplet size in the range of 44–93 μm. The production of droplets is scaled up by parallelizing eight droplet-formation units on a 3-D microdevice, and the variable coefficient of droplet size in all units reaches 3.2%. Using these W/W droplets as microreactors, monodispersed hydrogel particles are synthesized by either UV light or calcium ions, and recovered conveniently without cumbersome post-processing. The established method is simple, robust and suitable for various aqueous two-phase systems, displaying its potential in biocompatible carrier synthesis.