Berlin 2012 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 39: Wetting, Micro and nanofluidics II

CPP 39.5: Vortrag

Freitag, 30. März 2012, 10:45–11:00, C 243

Inertial Lift Forces and Probability Distributions in InertialMicrofluidics — •Christopher Prohm, Michael Gierlak, and Holger Stark — Institut für Theoretische Physik, Technische Universität Berlin, D-10623 Berlin, Germany

At intermediate Reynolds numbers, particles in a microfluidic channel organize themselves at a fixed distance from the channel axis and its walls[1]. This effect can be described in terms of an effective lift force acting on the particles. Devices utilizing this inertial focusing for particle separation have recently been demonstrated[2,3].

Here, we study a spherical particle in a pressure driven flow through a microchannel at intermediate Reynolds numbers. We employ multi-particle collision dynamics[4] (MPCD) to simulate the particle motion coupled to a viscous fluid which is described by the full Navier-Stokes equation. MPCD is a mesoscale simulation technique and has successfully been applied to colloidal dynamics in previous studies.

We determine lift forces and resulting single particle probability distributions in steady state and analyze their dependence on particle radius and Reynolds number. To connect lift forces and distributions, we propose a Smoluchowski equation, where the point particle exhibits a drift motion due to the lift force. We show that this effective picture and the simulations are in good agreement.

[1] Segré and Silberberg, Nature, 189, 209 – 210 (1961).

[2] Hur et al., Lab Chip, 10, 274 – 280 (2009).

[3] Di Carlo et al., PNAS, 104, 18892 – 18897 (2007).

[4] Kapral et al., Adv. Chem. Phys., 140, 89 – 146 (2008).