Strategic obstacle placement reduces drop breakup probability in emulsion flow

Droplet microfluidics has enabled a wide range of high throughput applications such as digital polymerase chain reaction (dPCR) and antibiotic screening. However, few studies have attempted to increase the throughput of the drop interrogation process. Here we investigate the effect of an obstacle on the throughput of drops flowing as a 2D monolayer concentrated emulsion flowing in a linearly converging channel into a constriction, a common geometry for drop content interrogation. Drop-drop interactions near the constriction entrance can lead to breakup of these drops at high flow rates, setting an upper limit for drop interrogation throughput. Previously, strategic placement of a circular post near a narrow exit can reduce conflict between interactions among living organisms or particles. Inspired by such works, we placed a circular post near the constriction entrance in order to reduce catastrophic drop-drop interactions that lead to drop breakup. Notably, when placed at appropriate location, the obstacle reduced the drop breakup fraction by up to 90%, thereby enabling a 12-fold increase in drop interrogation rate. Strategic obstacle placement is therefore an attractive strategy for increasing droplet microfluidic application throughput.