To make particles flow more efficiently, put an obstacle in their way

A bottleneck limits the effectiveness of microfluidic chips. Reaction-containing droplets can collide, break up, and foul experiments. ‘It’s a traffic problem, like several lanes of cars trying to squeeze through a tollbooth,’ says a mechanical engineering professor. Placing ‘traffic circles’ in the flow path causes droplets to line up in an orderly fashion so they can zoom through the system with far fewer collisions.