Chemical Engineering Journal, Vol.360, 562-568, 2019
Hydrodynamic control of droplet breakup, immobilization, and coalescence for a multiplex microfluidic static droplet array
Droplet manipulation is an essential technique in droplet-based microfluidics for a versatile assay platform. To improve the assay reliability, the droplet manipulation error should be minimized. Here, we study the droplet behavior for multiplex microfluidic static droplet array (mu SDA) formation, including breakup, immobilization, and coalescence. Hydrodynamic resistance control is the basic principle of droplet manipulation for mu SDA formation. We show the relationship between droplet dynamics and microfluidic channel design using dimensionless parameters, including capillary number, droplet extension, and the channel resistance ratio. In addition, we identify the critical factor between droplet breakup and non-breakup conditions as a function of the capillary number and initial droplet extension. This critical factor can also be varied by changing the hydrodynamic resistance ratio and entrance geometries of the trap chamber. We show that by using an optimized microfluidic design and optimized flow conditions, an error-free 100 multiplex mu SDA is formed through combinatorial coalesce of the droplets via microvalve operation. Our results provide an immediately applicable microfluidic design and a direct guide for device operation parameters as physical properties of samples to improve assay reliability.