title: Microfluidic pumping by micromolar salt concentrations.
abstract: An ion-exchange-resin-based microfluidic pump is introduced that utilizes trace amounts of ions to generate fluid flows. We show experimentally that our pump operates in almost deionized water for periods exceeding 24 h and induces fluid flows of μm s-1over hundreds of μm. This flow displays a far-field, power-law decay which is characteristic of two-dimensional (2D) flow when the system is strongly confined and of three-dimensional (3D) flow when it is not. Using theory and numerical calculations we demonstrate that our observations are consistent with electroosmotic pumping driven by μmol L-1ion concentrations in the sample cell that serve as 'fuel' to the pump. Our study thus reveals that trace amounts of charge carriers can produce surprisingly strong fluid flows; an insight that should benefit the design of a new class of microfluidic pumps that operate at very low fuel concentrations.
authors.affiliation: Institut für Physik, Johannes Gutenberg Universität Mainz, 55128 Mainz, Germany.
authors.forename: Ran
authors.identifier: http://orcid.org/0000-0001-7791-3914
authors.initials: R
authors.lastname: Niu
authors.affiliation: Institute for Computational Physics, Universität Stuttgart, Allmandring 3, 70569 Stuttgart, Germany.
authors.forename: Patrick
authors.initials: P
authors.lastname: Kreissl
authors.affiliation: SUPA, School of Physics and Astronomy, University of Edinburgh, JCMB Kings Buildings, Edinburgh EH9 3FD, UK. j.degraaf@ed.ac.uk.
authors.forename: Aidan T
authors.initials: AT
authors.lastname: Brown
authors.affiliation: Institute for Computational Physics, Universität Stuttgart, Allmandring 3, 70569 Stuttgart, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Rempfer
authors.affiliation: Institut für Physik, Johannes Gutenberg Universität Mainz, 55128 Mainz, Germany.
authors.forename: Denis
authors.initials: D
authors.lastname: Botin
authors.affiliation: Institute for Computational Physics, Universität Stuttgart, Allmandring 3, 70569 Stuttgart, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Holm
authors.affiliation: Institut für Physik, Johannes Gutenberg Universität Mainz, 55128 Mainz, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Palberg
authors.affiliation: SUPA, School of Physics and Astronomy, University of Edinburgh, JCMB Kings Buildings, Edinburgh EH9 3FD, UK. j.degraaf@ed.ac.uk.
authors.forename: Joost
authors.identifier: http://orcid.org/0000-0002-8781-7368
authors.initials: J
authors.lastname: de Graaf