Microfluidic platforms for size-based cell sorting

We report on the design, fabrication, and test results of a set of microfluidic devices with channels designed to promote fluidic hydrodynamic forces to sort and separate cells based on cell sizes. A set of 14 devices were made from polydimethylsiloxane (PDMS) molded from photolithographically patterned SU-8. The spiral fluidic channels with specific numbers of turns, widths, and outer diameters were designed with branches at strategic locations along the length to divert separated particles into collection chambers. A mixture of polystyrene particles of two different diameters (7 and 20 μm) was used as the test solution to determine the sorting efficiencies. Theoretical analyses of the designed performance were based on previously published equations and were found to be within practical agreement. The optimized performance was consistently close to 90% capture and isolation efficiencies from a mixture of up to 1:100,000 of 20-μm-to-7-μm particles at a flow rate of 4.0 mL·min-1.