On-demand micro encapsulation utilizing on-chip synthesis of semi-permeable alginate-PLL capsules

This paper presents an on-demand, multi-step synthesis scheme that is capable of forming semi-permeable microcapsules on an integrated microfluidic chip. Three-layered PDMS devices with pneumatically actuated diaphragm-valves constructed on specially designed fluidic-channels are utilized to realize the encapsulation process. In the prototype demonstration, Na-alginate droplets are metered, trapped, and then drawn into CaCl₂ droplets, while they react and form solid Ca-alginate microcapsules on the interfaces. In addition, entrapment and transfer of the resulting capsules can also be performed on the same microfluidic chip to further process Ca-alginate into semi-permeable alginate-PLL. As such, the demonstrated on-chip synthesis scheme could potentially fulfill the real-time controllability on micro-encapsulation, which is desired for a variety of biological and medical applications.