Hydrodynamic Trapping of Particles in an Expansion‐Contraction Microfluidic Device

Manipulation and sorting of particles utilizing microfluidic phenomena have been a hot spot in recent years. Here, we present numerical investigations on particle trapping techniques by using intrinsic hydrodynamic effects in an expansion‐contraction microfluidic device. One emphasis is on the underlying fluid dynamical mechanisms causing cross‐streamlines migration of the particles in shear and vortical flows. The results show us that the expansion‐contraction geometric structure is beneficial to particle trapping according to its size. Particle Reynolds number and aspect ratio of the channel will influence the trapping efficiency greatly because the force balance between inertial lift and vortex drag forces is the intrinsic reason. Especially, obvious inline particles contribution presented when the particle Reynolds number being unit. In addition, we selected three particle sizes (2, 7, and 15 μm) to examine the trapping efficiency.