Marangoni flow in micro-channels

A novel electrochemical method for driving fluids in micro-channels is presented. The principle is based upon the onset of Marangoni flow along the interface between an aqueous solution (mobile phase) and an organic electrolyte polymer gel coated on the inner walls of the microchannel. The gradient of surface tension responsible for the fluid motion arises from local changes in the surface charge. The excess charge is determined by the ionisation of surfactant species at the gel coating \ aqueous electrolyte interface which is effectively dependent on the Galvani potential difference. Potential differences of less than a volt between two closely spaced silver band electrodes along the microchannel can generate zones of high and low surface tension, promoting the motion of the aqueous electrolyte. (C) 1999 Elsevier Science S.A. All rights reserved.