Deterministic microfluidic ratchet

Kevin Loutherback, Jason Puchalla, Robert H. Austin, James C. Sturm

Research output: Contribution to journalArticlepeer-review

95 Scopus citations


We present a deterministic, nonthermal ratchet where the trajectory of particles in a certain size range is not reversible when the sign of the pressure gradient is reversed at a low Reynolds number. This effect is produced by employing triangular rather than the conventional circular posts in an array that selectively displaces particles transported through the array. The ratchet irreversibly moves particles of a certain size range in a direction orthogonal to an oscillating flow, with no net displacement of the fluid itself. The underlying mechanism of this ratchet is shown to be connected to irreversible particle-post interactions and the asymmetric fluid velocity distribution through the gap between the triangular posts. Diffusion plays no role in this ratchet, and hence the device parameters presented here can be scaled up to high rates of flow, of clear importance in separation technologies.

Original languageEnglish (US)
Article number045301
JournalPhysical review letters
Issue number4
StatePublished - Jan 26 2009

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy


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