All-aqueous water-in-water droplet microfluidics

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Nature of Proposed Research: Microfluidic systems that generate droplets of water surrounded by oil (so-called, water-in-oil droplets) have been used for more than a decade to produce monodisperse droplets, and realize important applications such as drug particle synthesis, single cell analysis, and cellular delivery. However, one of the fundamental challenges associated with water-in-oil droplets in biological applications is the need for extensive post-processing of the droplets due to the toxicity of the oil phase, which makes an oil-free, biocompatible droplet microfluidic technology highly desirable. An alternative fluid system for oil-free droplet microfluidics is an aqueous two-phase system (ATPS), which forms due to the mixture of high concentrations of at least two incompatible polymer solutions. The two water-based liquids in an ATPS are separated by an interface, similar to that observed between water and oil, albeit with much lower interfacial tension. My group showed for the first time, in 2016, that passively generating water-in-water droplets in microfluidics is achievable by using weak hydrostatic pressure as the driving force, and that such water-in-water droplets in microfluidics can be used to both encapsulate and controllably release cells in an all-biocompatible environment. These results enabled a new microfluidic platform that utilizes water-in-water as opposed to water-in-oil droplets for biotechnological applications. This NSERC Discovery program is advancing the water-in-water droplet microfluidics platform by 1) increasing functionality, 2) improving performance, and 3) realizing bio-applications. Specifically, this program is working towards adding the functionalities of water-in-water droplet sorting by content, and achieving double-emulsions of water-in-water-in-water droplets. Furthermore, this program is focusing on orders-of-magnitude improvements in droplet generation throughput, to help realize clinical applications of the technology. Finally, this program is developing the water-in-water droplets for applications in drug delivery and in vitro modeling of in vivo cellular phase separation processes. Anticipated Outcomes: The research supported by this grant is expanding the emerging paradigm of water-in-water droplet microfluidics that my group helped initiate in recent years. Upon maturation, this water-in-water droplet microfluidics platform will transform biotechnological applications, such as all-biocompatible drug delivery particle formation, and cellular encapsulation for cellular therapy, leading to improved health outcomes, and advancing the biotechnology industry in Canada. The fundamental fluid mechanics questions that we address will profoundly impact the microfluidics community. Highly qualified personnel (HQP) trained in this program will possess a unique skillset in lab-on-a-chip device design and development that makes them suitable for many career paths in Canada's biotechnology sector.