UC San Diego

Microdroplet formation by way of microfluidics has attracted great interest in the previous decade. This dissertation details the design, fabrication, development, and use of a low-cost lab-on-a-chip active on-demand microdroplet generator and cell encapsulation system. This system incorporates microfluidics, optics, and electronics into a single system where you can create tune-able microdroplets with precision and in isolation from other unwanted droplets.

The polydimethylsiloxane (PDMS) microfluidic on-demand microdroplet generator system creates a microdroplet by overcoming the interfacial tension of an aqueous immiscible fluid in stable laminar flow with an oil-based continuous fluid by way of hydrodynamic forces created in the continuous fluid from a millisecond-scale impulse originating from a PZT-based acoustic actuator. The system created offers a significant increase in speed over existing tuneable on-demand microdroplet generators as well as increased flexibility in fluid velocities in the system.

Additional optics to detect the location and velocities of fluorescently-labeled 15um beads, representing cells, are used in conjunction with the developed system to successfully capture beads in droplets as they flow through microfluidic cavities with single-bead purity much higher than Poisson-statistic-bound systems employed today.

The development of tuneable and programmable microdroplet generators and accurate single-cell encapsulation can be of great use to many emerging biological assays, techniques, and applications such as droplet digital PCR (ddPCR), single-cell incubators, and drug discovery.