Non-Spherical Hollow Microgels with Uniform Sizes and Tunable Shapes from Microfluidic-Assisted Approach

We conducted microfluidic technique to generate uniform double emulsion droplets with alginate aqueous solution forming the shell phase. Size and shell thickness of the droplets can be tailored by changing the property of each fluid and flow ratio of the fluids. The viscoelastic ionic cross-linkable emulsion droplets (e.g., sodium alginate aqueous droplets) could experience a deformation process when dropping down into a viscous gelation bath containing Ba(Ac)(2) or Ca(Ac)(2). The deformed non-spherical structures of the droplets can be fixed by ionic cross-linking of the alginate during the dropping down process, triggering the formation of hollow microgels with varied shapes in the viscous gelation bath. By manipulating the concentration of sodium alginate in the aqueous solution, viscosity of the gelation bath, and properties of the core fluids, microgels or hollow microgels with varied shapes (e.g., tear-like, rod-like and pepper-like shapes) can be systemically generated. We show that functional species (quantum dots and/or fluorescence dyes) can be successfully encapsulated into the microgels, demonstrating the potential applications of the non-spherical microgels in the area of bioimaging, drug delivery and release, barcoding, single cell analysis and cell culture.