A new method of analysing electro-osmosis using FET models

To reduce volumes of liquid or slurry waste, it may be necessary to extract water, and the best way to achieve this in practice is often by flow curre nt adjustments. Current has been observed to reach a maximum at some point after the application of a voltage, and to decrease thereafter. The cause f or this seems to lie in the movement of impurity particles, so-called elect rophoresis. By controlling this movement, it is possible to increase flow r ates. Analyses of the problem in the past have included studies into transf er characteristics, mutual conductance and amplification. In contrast to th is earlier work, the authors have experimented with placing a gate electrod e between the upper and lower electrodes in order to approach the whole rea ction in the manner of a field effect transistor (FET) problem. It is well known that varying the gate voltage in a FET leads to a corresponding chang e in the drain current. If the displaced particles are regarded in a simila r way to electrons, the same method of analysis can be used in the case of electro-osmosis. In the experiment reported, this method was used to invest igate associated transfer characteristics. It was found that the insertion of the gate allowed a greater liquid Row rate to be obtained than would be possible with more traditional methods. (C) 2001 Published by Elsevier Scie nce B.V.