title: Recirculation of nanoliter volumes within microfluidic channels.
abstract: A microfluidic device is described, capable of recirculating nanoliter volumes in restricted microchannel segments. The device consists of a PDMS microfluidic structure, reversibly sealed to a glass substrate with integrated platinum electrodes. The integrated electrodes generate electroosmotic flow locally, which results in a cycling flow in the channel segment between the two electrodes in case one channel exit is closed (dead-end channel). This cycling flow is a consequence of the counterbalancing hydrodynamic pressure against the electroosmotically generated flow. Acid-base indicators were employed to study the formation of H(+) and OH(-) at both the in-channel electrodes. The formation of acid can locally change the zeta-potential of the channel wall, which will affect the flow profile. Using this method, small analyte volumes can be mixed for prolonged times within well-defined channel segments and/or exposed to in-channel sensor surfaces.
authors.affiliation: Biochip Group, MESA+ Research Institute, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.
authors.forename: Rob G H
authors.initials: RG
authors.lastname: Lammertink
authors.forename: Stefan
authors.initials: S
authors.lastname: Schlautmann
authors.forename: Geert A J
authors.initials: GA
authors.lastname: Besselink
authors.forename: Richard B M
authors.initials: RB
authors.lastname: Schasfoort