Inertial Separation of Microscale and Submicron Particles on Microfluidic Devices

The separation and enrichment of micron and submicron particles without causing excessive shear stress to biologically relevant particles are becoming increasingly important in diagnostics. Inertial microfluidics allows for the passive and continuous separation of micron and submicron particles based on their diameter and the principles of flow. In 1961, Segré and Silberberg demonstrated that a uniform suspension of millimeter-sized particles in Poiseuille flow focused into an annulus within a straight pipe. This demonstration indicated that the previously neglected, but significant inertial effects led to neutrally buoyant particles migrating laterally across streamlines. In addition, secondary Dean flows can be generated by the centrifugal forces imposed on parabolic flows traveling through curves or regions with an abrupt change in cross-sectional area. Consequently, secondary Dean forces combined with shear gradient and wall interaction lift forces permit inertial separations in much shorter channels. With the aid of computational fluid dynamic simulations, we design microchannels with non-linear geometries that combine inertial effects, centrifugal forces, and diffusive transport to enrich and separate biologically relevant particles.