title: Continuous and size-dependent sorting of emulsion droplets using hydrodynamics in pinched microchannels.
abstract: In this report, a microfluidic system is presented for continuous and size-dependent separation of droplets utilizing microscale hydrodynamics. The separation scheme is based on laminar-flow focusing and spreading in a pinched microchannel, referred to as "pinched flow fractionation (PFF)", which was previously developed for the size-dependent separation of solid particles, such as polymer microparticles or cells. By simply introducing emulsion and the continuous phase into a microchannel, continuous separation could be achieved without using complicated operations or devices. We first examined whether this scheme could be applied for droplets, by using a pinched microchannel with one outlet, and observed the behaviors of monodisperse droplets generated at the upstream T-junction. Analysis via high-speed imaging revealed that the length of the pinched segment is critical for precise separation of droplets. Then, separation of a polydisperse oil-in-water emulsion that was prepared previously was demonstrated using a microfluidic device equipped with multiple outlets. These results showed the ability of the presented system to sort or select specific-sized droplets easily and accurately, which would be difficult to achieve using normal-scale schemes, such as centrifugation or filtration.
authors.affiliation: Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka, Japan.
authors.forename: Hirosuke
authors.initials: H
authors.lastname: Maenaka
authors.forename: Masumi
authors.initials: M
authors.lastname: Yamada
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yasuda
authors.forename: Minoru
authors.initials: M
authors.lastname: Seki
mesh_terms: D004655:Emulsions / Q000737:chemistry; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods*; D014867:Water / Q000737:chemistry*
chemical_list: D004655:Emulsions; D014867:Water