Comparative analysis of lateral and vertical microfluidic parallelization for high-throughput microdroplet generation

Abstract

The breakup of confined liquid threads in microfluidic flow-focusing geometries is governed by the interplay between interfacial tension, viscous stresses, and hydrodynamic resistance, which becomes increasingly complex in parallelized systems operated at high throughput. While parallelization is widely used to increase microdroplet generation rates, the role of architecture in regulating droplet breakup dynamics and inter-channel uniformity remains insufficiently understood. Here, we systematically compare microdroplet formation in lateral and vertical parallel flow-focusing architectures using glass microfluidic devices. By constructing flow regime maps and performing quantitative scaling analyses, we show that the two architectures exhibit markedly different droplet breakup behaviors, characterized by distinct scaling exponents for droplet size and generation frequency. These differences reflect geometry-dependent physical mechanisms governing the balance between interfacial tension, shear stress, and flow resistance during droplet formation. Furthermore, we demonstrate that geometric coupling in parallelized flow-focusing systems imposes contrasting constraints on flow redistribution among channels, leading to different limits in microdroplet size uniformity and attainable generation frequency. The lateral architecture supports robust and uniform droplet breakup over a broad operational window, whereas the vertical architecture enables higher-frequency droplet generation but with increased sensitivity to flow imbalance. Together, these results establish a geometry–hydrodynamics framework linking device architecture to droplet breakup regimes and scaling behavior, providing predictive design principles and new fundamental insight into interfacial dynamics in parallelized microfluidic systems.