Separation of dispersed microparticle from whole blood using three-dimensional helical tubular microfluidics

Purification of blood from microparticles while maintaining its suitability for autotransfusion provides a revolutionary support for advanced healthcare through circulatory system of blood flows. However, there is a great challenge in the separation of particles from blood physically with high efficiency. Here, we proved a novel approach for whole blood treatment of microparticle separation utilizing a three-dimensional microfluidic chip with helical structures of tubular channels. The chips with helical structures characterized by spiral diameters and pitches are fabricated with flexible silicon-based tubes with different inner diameters in which photolithography is not required. By controlling Reynolds and Dean numbers to generate appropriate stable Dean flow along the tubular channels, microparticles with diameters from 15 to 30 μm are separated directly from untreated whole blood with about 10% blood loss, and the free-hemoglobin concentration after separation remains in a safe level for further clinical transfusion. Two distinct patterns of particle accumulation in the cross section of microtubes are observed. It is also interesting to find that different from many practices that lyse red blood cells before particle or cell sorting, the intensive cell-particle interactions in whole blood facilitate particle focusing to regions closer to channel walls than in pure liquid without red blood cells. This label-free particle separation method, based on hydrodynamical interactions among the particles and deformable blood cells in stable Dean vortexes of helical tubular microfluidic chips, not only paves the way for innovative healthcare using functional microparticles but also enlightens the sorting of nucleated cells separation from whole blood biophysically.