Droplet-Microfluidic Device for the Characterization of Perfluorinated Emulsions

Microfluidics is being used throughout academia and industry today to perform large numbers of experiments with extremely small volumes of fluids. By doing this, those that study microfluidics hope to raise through-put, lower cost and limit the environmental impact of scientific research.2 Complementing the increased use of microfluidics, the use of perfluorinated emulsions in the field of droplet-based microfluidics is also experiencing large growth.3 However, many of the products available today are either proprietary and/or poorly understood. While some chemical structures are known, some of the most scientifically intriguing perfluorinated oils and surfactants do not have their chemical structures or characteristics available to the public research community. During the course of our senior design project, we isolated one particular perfluorinated oil and surfactant mixture and performed a number of tests on the stability of the emulsions over a variety of different biologically relevant variables. To achieve this, we were required to design multiple iterations of droplet-microfluidic chips to create the simplest emulsions for study. The resulting designs gave us an excellent platform to study not only our emulsion system, but many future emulsions systems in a novel manner. We proved its efficacy by using the system to show great variance in the stability and surface energy of different pH droplets in QX100 perfluorinated oil with surfactant as well as a characterizable change in stability when changing the concentration of phosphate and media constituents in the droplets. Finally, we further analyzed the emulsion with the help of Dr. Gerald Fuller’s coalescence lab in Stanford University’s chemical engineering department and observed changes in the viscoelastic nature of aqueous-perfluorinated oil interfaces over a variety of biologically relevant conditions. Though much was accomplished, there is still a need to further characterize both more aqueous conditions and more perfluorinated systems to truly shed light on the field. Additionally, more detailed viscoelastic analysis needs to be performed on these new conditions and oil-surfactant mixtures as well as a thorough pendant-drop style surface tension experiment on all experiments performed