First-come-first-store microfluidic device of droplets using hydrophobic passive microvalves

Abstract

Slug flow is segmented droplets where internal convection occurs. The internal convection is useful for efficient mixing of their contents when they are used as microreactors. The segmentation is also useful for recording of temporal changes in biological samples such as cells and animals. However, methods to store the droplets separately, which are necessary for precise chemical analysis, are not well developed. Methods with simple structures and controls are required for storing many droplets in the first-come-first-store manner. Passive microvalves allow for prearranged flow without any controls using simple microstructures. To store the droplets one-by-one for precise analysis, we designed an automatic microfluidic device using hydrophobic passive microvalves. The valves are based on capillary forces and have different burst pressures. Using this device, each droplet was automatically stored in a different reservoir.