(69a) Hydrodynamic Resistance of a Train of Confined Droplets

Microfluidic devices have become increasingly popular in the fields of science and engineering due to their ease of fabrication. These devices have significant potential for a wide range of applications including biomedical diagnostics and biosensing. Many of these applications involve the transportation, sorting and storage of droplets. When a single-phase fluid flows in a confined channel, there is a resistance to flow. Two-phase fluid flow, which includes droplets, introduces even more resistance to flow, known as hydrodynamic resistance of the droplets. The hydrodynamic resistance of droplet is the main key factor that controls the behavior of the droplets in a channel. Researchers have tried to determine the parameters that may affect the hydrodynamic resistance of droplets in a microfluidic channel. However, their studies have limited domain of parameters. The purpose of this study is to measure the hydrodynamics resistance of droplet over a wider range of parameters, which include capillary number, drop size, intra-drop spacing, viscosity ratio and surface tension between the inner and outer phase. We measure the resistance of the droplet using a microfluidic comparator; it directly compares a reference channel with known resistance to a parallel test channel containing droplets of unknown resistance. These water-in-oil droplets are generated upstream from the comparator using a cross-junction where droplet size and spacing can be easily controlled.  Quantifying the resistance of droplet can help researchers better design their microfluidic devices for droplet trafficking, sorting or trapping.