Particle Inertial Focusing in Spiral Channel of Tapered Cross-Section

Inertial microfluidic technology is widely used for microparticle manipulation (e.g., particle/cell separation and focusing). This paper proposes a novel spiral channel of the tapered cross-section to realize the high-efficiency separation of microbeads of different sizes. The spiral channel is bonded to a thin PDMS (Polydimethylsiloxane) membrane to create the tapered cross-section, and air pressure is applied to deform the membrane. The inertial focusing performance of the channel is investigated by using polystyrene fluorescent microbeads of different diameters. The experimental results show that 15 μm microbeads experience strong inertial lift force and migrate to the inner wall, while 6 μm microbeads are influenced by the dominating Dean vortex and move to the outer wall, resulting in successful separation of two microbeads. The unique advantage of the tapered channel is that the distance between the large and small microbeads can be regulated by the working pressure, and a big gap of ~ 305 μm is achieved under the working pressure of 30 kPa. We hold the opinion that the proposed microfluidic device will provide insights for high-efficiency cell separation and enrichment.