Abstract
In inertial microfluidics lift forces cause a particle to migrate across streamlines to specific positions in the cross section of a microchannel. We control the rotational motion of a particle and demonstrate that this allows to manipulate the lift-force profile and thereby the particle's equilibrium positions. We perform two-dimensional simulation studies using the method of multi-particle collision dynamics. Particles with unconstrained rotational motion occupy stable equilibrium positions in both halfs of the channel while the center is unstable. When an external torque is applied to the particle, two equilibrium positions annihilate by passing a saddle-node bifurcation and only one stable fixpoint remains so that all particles move to one side of the channel. In contrast, non-rotating particles accumulate in the center and are pushed into one half of the channel when the angular velocity is fixed to a non-zero value.
Highlights
The transport of particles in a fluid is a recurring problem on very different length scales
When an external torque is applied to the particle, two equilibrium positions annihilate by passing a saddle-node bifurcation and only one stable fixpoint remains so that all particles move to one side of the channel
In particular for biomedical applications a large number of microfluidic devices using inertial migration has been proposed in recent years [1,2,3,4,5,6,7]
Summary
The transport of particles in a fluid is a recurring problem on very different length scales. In particular for biomedical applications a large number of microfluidic devices using inertial migration has been proposed in recent years [1,2,3,4,5,6,7]. The devices are carefully designed for controlling the motion of the dispersed colloidal particles They use a combination of special shapes for the microchannel cross sections and the action of inertial lift forces to tailor the equilibrium positions of the particles at the channel outlet [5, 6]. In this article we investigate how the controlled rotational motion of a colloidal particle influences the liftforce profile and thereby the equilibrium positions in the channel cross section.
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