Microchannel-based Droplet Generation Using Multiphase Flow: A Review

Microfluidics is a multidisciplinary field that allows for precise control of fluids at a micrometer scale, with the goal of generating encapsulated structures or droplets for specific purposes. However, producing monodispersed droplets remains a challenge, making it necessary for researchers to investigate optimal microchannel geometries and parameters for controlling droplet size. Channel-based geometries, including T-junction, flow-focusing, co-flowing, membrane, and step emulsification, are the most commonly used geometries, each with its own advantages and weaknesses. This literature review aims to highlight assessment methods of microfluidic device performance and physical phenomenon in droplet generation for each channel-based geometry, including recent findings by researchers. Output parameters such as microchannel geometries, flow patterns, and flow regime maps with interpretations can be used to evaluate the optimum input for generating droplets that are suitable for a certain application. With the COVID-19 pandemic affecting the world, there is an opportunity to use microfluidic devices to study SARS-CoV-2 and develop post-pandemic therapeutics. The next challenge in microfluidic device development is producing high-throughput double emulsion droplets with monodispersed size using optimum input parameters to satisfy the drug delivery purpose.