Step emulsification device for high-throughput droplet generation for biomedical application

Microfluidics is the science and technology devoted to manipulating small amounts of fluids (typically in the pico- and nanoliter ranges), through channels of sizes on the order of 10−100 um. Over the past two decades, microfluidics has contributed to the introduction of the so called Lab-on-a-Chip, i.e. the integration of chemical and biological processes through their miniaturization in compact devices. Nowadays, one particularly influential area within microfluidics is droplet microfluidics, in which two immiscible fluids, usually an aqueous phase and an oil phase, are brought together at specially designed channel junctions to generate controlled emulsions. For biological applications, the emulsions consist of water-in-oil droplets stabilized by surfactants. Each droplet acts as an isolated microreactor, allowing the stable separation of chemicals, biomolecules and cells, while simultaneously reducing reagent consumption and enabling higher-throughput experimentation compared to bulk methods. Nonetheless, droplet-based microfluidics is still limited in scaling up droplet production to satisfy the demands of biotechnological and biomedical applications: current systems typically achieve generation rates of 12–15 kHz, whereas these fields often require throughput values on the order of several MHz. Among the droplet generation methods commonly employed for this purpose, step emulsification represents a promising solution, as it enables the production of highly monodisperse droplets with significantly lower material consumption compared to other techniques. This Master’s Thesis aims to provide the first exploratory study on step emulsification conducted at the Department of Physics and Astronomy in the University of Padua. The research involves the design and fabrication of a microfluidic device using multiple microfabrication techniques, including photolithography, 3D printing and soft lithography. Device performance is then characterized by quantifying the average diameter of the generated droplets and the production rate under controlled flow conditions.