A Microfluidic Strategy for Controllable Generation of Water‐in‐Water Droplets as Biocompatible Microcarriers

Droplet microfluidics has been widely applied in functional microparticles fabricating, tissue engineering, and drug screening due to its high throughput and great controllability. However, most of the current droplet microfluidics are dependent on water-in-oil (W/O) systems, which involve organic reagents, thus limiting their broader biological applications. In this work, a new microfluidic strategy is described for controllable and high-throughput generation of monodispersed water-in-water (W/W) droplets. Solutions of polyethylene glycol and dextran are used as continuous and dispersed phases, respectively, without any organic reagents or surfactants. The size of W/W droplets can be precisely adjusted by changing the flow rate of dispersed and continuous phases and the valve switch cycle. In addition, uniform cell-laden microgels are fabricated by introducing the alginate component and rat pancreatic islet (β-TC6) cell suspension to the dispersed phase. The encapsulated islet cells retain high viability and the function of insulin secretion after cultivation for 7 days. The high-throughput droplet microfluidic system with high biocompatibility is stable, controllable, and flexible, which can boost various chemical and biological applications, such as bio-oriented microparticles synthesizing, microcarriers fabricating, tissue engineering, etc.