Microfluidic Device for Continuous Particle Separation Using Hydrodynamic Filtration

A size-dependent particle separation (classification) is one of the most important procedures in biochemical, environmental, or medical analyses and their applications. However, the smaller particle size or the smaller size difference makes the particle classification difficult. The Lab-on-a-Chip concept have encouraged the miniaturization of various separation or selection methods for small particles, including polymer beads, cells, and macromolecules. Microfluidic devices have a potential to facilitate rapid and precise particle manipulation, due to accurately fabricated structures close to particle sizes, in micrometer or sub-micrometer dimensions. In our previous study, a new scheme for particle sorting, pinched flow fractionation (PFF), and that for separating and concentrating particles, hydrodynamic filtration (HDF), utilizing microfluidic devices have been proposed. In the latter method, simple introduction of particle suspension enables both size-dependent separation and concentration, simultaneously. However, the inevitable contamination of small particles into the concentrated large-particle fraction decreases the separation efficiency. In this paper, the improved separation efficiency by employing flow splitting and recombining will be demonstrated, and the application of this method to blood cell separation. This microfluidic separation system will be useful due to its simplicity and accuracy.