An unrecognized force in inertial microfluidics

Abstract

Describing effects of small but finite inertia on suspended particles is a fundamental fluid dynamical problem that has never been solved in full generality. Modern microfluidics has turned this academic problem into a practical challenge through the use of high-frequency oscillatory flows, perhaps the most efficient way to take advantage of inertial effects at low Reynolds numbers, to precisely manipulate particles, cells and vesicles without the need for charges or chemistry. The theoretical understanding of flow forces on particles has so far hinged on the pioneering work of Maxey and Riley (MR in the following), almost 40 years ago. We demonstrate here theoretically and computationally that oscillatory flows exert previously unexplained, significant and persistent forces, that these emerge from a combination of particle inertia and spatial flow variation, and that they can be quantitatively predicted through a generalization of MR.

References in corpus (2)

• Effect of weak fluid inertia upon Jeffery orbits
• Size-dependent particle migration and trapping in 3D microbubble streaming flows

Cited by in corpus (5)

• Second-order inertial forces and torques on a sphere in a viscous steady linear flow
• Multi-curvature viscous streaming: flow topology and particle manipulation
• Wave-averaged motion of small particles in surface gravity waves: effect of particle shape on orientation, drift, and dispersion
• Principles of hydrodynamic particle manipulation in internal Stokes flow
• Controlled particle displacement by hydrodynamic obstacle interaction in non-inertial flows