Size-Dependant Separation of Multiple Particles in Spiral Microchannels

This work describes continuous separation of a multi-particle mixture in a simple spiral microchannel. The approach uses the concept of inertial microfluidics and takes advantage of the inertial lift forces coupled with rotational Dean drag to cause neutrally-buoyant particles to focus in a single equilibrium position near the inner channel wall. This position is strongly dependent on particle diameter. A 5-loop low-aspect-ratio Archimedean spiral microchannel with dimensions of 500 µmx100 µm (WxH) and 1 cm initial radius of curvature was used to demonstrate for the first time simultaneously focusing and separation of four particles. The polystyrene particles (7.32 µm, 10 µm, 15 µm, 20 µm in diameter) were selected for this work since they are compatible to the size of blood cells. The device exhibited a 80~90% separation efficiency, which is comparable to that of other microfluidic separation systems. The primary advantage of this passive technique is that it uses simple planar geometry and provides higher sample throughput. As a result of these advantages, it can be implemented on a lab-on-a-chip device for hematology and clinical application.