Ratcheted Electrophoresis of Aqueous Droplets

Rapid droplet transport within microfluidic devices enables parallelization and applications ranging from medical diagnostics to particle synthesis. Typically, high-speed droplet manipulation is achieved passively via pressure driven flows. Active manipulation of droplets (e.g., digital microfluidics) can provide more precise control of droplet position but often at reduced speeds and increased complexity. By contrast, contact charge electrophoresis (CCEP) within ratcheted microfluidic channels can enable the rapid transport of aqueous drops using a simple DC voltage. Here, we demonstrate ratcheted CCEP of microfluidic droplets and discuss heuristics for designing ratcheted droplet transporters within microfluidic devices. We highlight opportunities for CCEP in powering other types of droplet-based unit operations such as drop generation, merging, and sorting.