Hydraulic parallel design for microfluidic ultraviscous droplets

Over the past decades, droplet microfluidic designs have been developed to simultaneously achieve monodisperse particles and high production rates. However, most of these advancements are targeting a low viscous fluid (viscosity about 10^-2–10^-3 Pa·s) so that microfluidic designs are oriented to increase the channel numbers. This study designs and presents a droplet microfluidic device that can generate uniform droplets of an ultraviscous fluid (viscosity about 3.5 Pa·s). To emulsify an ultraviscous fluid into a uniform and high-throughput droplet, it is necessary to increase the channel numbers and control the channel resistance of the dispersed phase. In this work, the microfluidic devices were divided into 16, 32, and 64 specific designed T-junctions each from one single inlet, and divided junctions were connected into a single post-flow of the continuous phase. At 64 junctions of the microfluidic device, it can emulsify the ultraviscous fluid into ~ 330,000 droplets per hour. The generated droplet has a 2~3% coefficient of variation (CV) at a diameter of about 100μm. In addition, on the account of the fully 2-dimensional branched design, just one soft lithography experiment is enough to fabricate the microfluidic chip which is especially favorable to newcomers.