A new method of analysing electro-osmosis using FET models

Abstract 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 current adjustments. Current has been observed to reach a maximum at some point after the application of a voltage, and to decrease thereafter. The cause for this seems to lie in the movement of impurity particles, so-called electrophoresis. By controlling this movement, it is possible to increase flow rates. Analyses of the problem in the past have included studies into transfer characteristics, mutual conductance and amplification. In contrast to this earlier work, the authors have experimented with placing a gate electrode between the upper and lower electrodes in order to approach the whole reaction 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 change in the drain current. If the displaced particles are regarded in a similar 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 investigate associated transfer characteristics. It was found that the insertion of the gate allowed a greater liquid flow rate to be obtained than would be possible with more traditional methods.