Abstract
We present a fluidic device that shows ratchet-like characteristics for particle transport at low Reynolds. The ratchet consists of a two-dimensional saw-tooth channel, within which a laminar flow is generated by imposing a longitudinal pressure gradient. Particle trajectories are calculated by solving the continuity and Navier–Stokes equations for the fluid flow and the equations for particle transport in both flow directions. The ratchet-like effect is connected with a large asymmetry in the mean transit time, with regard to flow direction, due to particle motion within zones of low flow velocity near the asymmetric wall profile. We show how to obtain ratchet of particles with select Stokes under given flow conditions by adjusting the geometry of the ratchet channel.
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Notes
A parabolic profile is achieved within the first segment of the channel at a distance of ≈\(l/5\) from the entrance of the smooth segment, i.e. prior to the launch position of the particles. Thus, we perform the simulations of this work by taking, for simplicity, a parabolic flow profile at the inlet boundary.
The governing differential equations are discretized in a computational mesh and numerically solved here using FLUENT 6 [Fluent Inc., FLUENT 6.1, 6.2 User’s Guide (2003, 2005)].
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Acknowledgments
We acknowledge Antônio J. C. Sampaio for discussions and helpful comments. We also thank Josué Mendes Filho for stimulating remarks. This research was supported by CAPES, CNPq, FUNCAP and FINEP (Brazilian agencies), and CNPq/FUNCAP Pronex grant.
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Cisne, R.L.C., Vasconcelos, T.F., Parteli, E.J.R. et al. Particle transport in flow through a ratchet-like channel. Microfluid Nanofluid 10, 543–550 (2011). https://doi.org/10.1007/s10404-010-0688-y
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DOI: https://doi.org/10.1007/s10404-010-0688-y