For cholesteric and chiral smectic liquid crystals a rotation of the helical superstructure can be induced for suitable boundary conditions for external fields such as temperature gradients and electric fields: the Lehmann effect. Here we predict that the inverse effect can lead to a pump for particles and ions on a length scale of microns: When a spatial pattern such as a phase winding pattern or a spiral is generated, for example, for a freely suspended smectic ${\mathrm{C}}^{*}$ film, a concentration current arises. We also point out that this concentration current is, under suitable experimental conditions, accompanied by a heat current and/or an electric current. Similar effects are expected for cholesterics, smectic ${\mathrm{F}}^{*}$ and ${\mathrm{I}}^{*}$ as well as for Langmuir monolayers, since all of these systems share the property of macroscopic chirality.

• Received 20 November 2007

DOI:https://doi.org/10.1103/PhysRevE.78.021703