On-chip gelation of temporally controlled alginate microdroplets

This paper presents a simple and robust microfluidic device that allows on-chip gelation and temporal control of alginate droplets in a continuous oil phase to enhance hydrogel recovery and collection rate. The additional control flow including calcified oleic acid leads to adjust droplet interval and gelation of the alginate droplet simultaneously through microtunnel structures. The gelated alginate microbeads were successfully gathered at the outlet with sufficient droplet interval. Furthermore, the droplet interval in the droplet-generating channel was flexibly modulated by adjusting the control flow rate under the fixed flow rate of droplet-generating flow. This approach is applicable to droplet synchronization for facilitating many droplet-based microfluidic applications.