Microfluidic Droplet Generation Enabled by a Pressure Barrier Mechanism

Microfluidic droplet generation enables the rapid and efficient production of large quantities of droplets to be used in various fields such as medical science and biology. While polydisperse droplets are inherent in bulk emulsion production, which can be potentially used for combinatorial experimentation in addition to monodisperse droplets, microfluidic chip platforms offer superior control for post‐processing applications and are better suited for integration within miniaturized systems. In this study, we present a simple yet robust method for generating droplet aggregation, which could be used for applications where the polydisperse droplets are advantageous in the context of microfluidics. This approach offers a significantly shorter timescale (in a fraction of a second) compared to existing methods in the literature. The generated droplets rely on the hydrodynamic instability of an aqueous interface within the framework of the pressure barrier principle. This approach requires adjustments to geometry and surface wettability properties, resulting in a distinct mode of droplet generation. This approach not only leads to a platform for the water‐in‐air microfluidics systems but also facilitates the integration of water‐in‐oil emulsion into microfluidic devices as a subsequent step. It was also observed that the polydisperse droplets are only generated in Glass‐PDMS chips, not PDMS‐PDMS chips, and the main channel height should be critically narrow (below 10 μm in our method) to allow the system to generate droplets. The generated droplets have diameters between 1 and 7 μm, with the majority concentrated in the 2–3 μm size band.