Particle manipulation by geometry-induced secondary flow in double-layered microchannels with groove arrays

Inertial microfluidic particle manipulation technology, which can manipulate the target particle entirely relying on the microchannel characteristic geometry and intrinsic hydrodynamic effects, has attracted great attention due to the fascinating advantages such as high-throughput, simplicity, precise manipulation and low cost. As a passive microfluidic technology, inertial microfluidics can precisely focus, separate or trap particles in the continuous and high-throughput manner without the extra requirement of external field for functionalities, and is very promising for a wide range of industrial, biomedical and clinical applications. In the regime of inertial microfluidics, both the non-negligible inertia and viscosity of fluid introduce two important inertial effects, including the inertial migration and the secondary flow. The inertial migration in the straight microchannel normally contributes to multiple equilibrium positions, which causes the difficulty of efficient particle focusing and separation. It is found that the secondary flow can remedy this congenital deficiency through its hydrodynamic effects, and has been widely adopted to reduce the number of the equilibrium position and greatly improve the particle manipulation performance in inertial microfluidic devices...