Redox-Magnetohydrodynamics for Microfluidic Control: Remote from Active Electrodes and Their Diffusion Layers
by Scrape, P. G.; Gerner, M. D.; Weston, M. C.; Fritsch, I.
Localized, directed microfluidic flow in bulk solution, far from diffusion layers at active electrodes, was induced by redox-magnetohydrodynamics (MHD) using a magnet smaller than the distance between the electrodes to tune the flow. This "remote MHD" indicates that redox species are required only at active electrodes to sustain a faradaic current, not in the bulk where microfluidic control is desired. Thus, complete separation of redox species from sample and analyte, which can be achieved by ion-conducting barriers or electrode surface modifications, will boldly expand applications of redox-MHD in micro total analysis systems. Flow was effected in a model solution of ferricyanide/ferrocyanide and potassium chloride, between two sets of electrodes located 17.5 mm apart on a chip. A stack of two permanent magnets, 6-mm wide (one-third of the interelectrode distance), was positioned under the chip between electrodes, and a 30 mu A electronic current was applied to the electrodes. The resulting ionic current led to a MHD force causing fluid flow of <= 16.9 mu m/s above the magnet, determined by video microscopy of 10-mu m latex-polystyrene microbeads and particle image velocimetry software. Calculations indicate that MHD is the major source of the observed flow, although the magnetic field gradient may affect the flow profile.
- Journal
- Journal of the Electrochemical Society
- Volume
- 160
- Issue
- 6
- Year
- 2013
- Start Page
- H338-H343
- URL
- https://dx.doi.org/10.1149/2.076306jes
- ISBN/ISSN
- 1945-7111; 0013-4651
- DOI
- 10.1149/2.076306jes