Microfluidic-based droplet merging device with a non-contact droplet pairing method

In this study, we present a simple, novel microfluidic device for merging two different droplets in parallel using only fluid flow control. By utilizing the deformability characteristic of a droplet in a pressure-driven shear flow, a unique Laplace trap with a multi-step “trapping-releasing- non-contact pairing-destabilization-contact” droplet merging mechanism was developed. Using a device comprising an array of these Laplace traps, parallel merging of two droplets was successfully performed within a short time variation (n = 55, mean = 5.7 s, SD ±4.3 s).