Advancements in microfluidic droplet generation: methods and insights

Droplet microfluidics, a subset of microfluidics, focuses on the controlled generation, manipulation, and transport of micro- to femto-scale droplets. In the last three decades, this technology has become essential in high-throughput applications across biological and chemical analyses, enabling advances in areas such as cell encapsulation, drug screening, digital PCR, and protein crystallization along with applications in chemical mixing, chemical kinetics and chromatography. This review systematically classifies droplet generation methods into classical and contemporary techniques to discuss the technological evolution in droplet generation practice, and further subdivision into passive and active methods based on their operational principles. The paper further discusses about centrifugal microfluidic platform and its applications. Furthermore, the review briefly discusses recent trends in closed-loop feedback based droplet generation methods. By comparing the strengths, limitations, and applications of these techniques, this review provides information on the selection of droplet generation methods for specific applications and highlights potential directions for future research and technological development.