Electrochemically-actuated mercury valve for flow rate and direction control: design, characterization, and applications

An electrochemically actuated mercury column was configured to function as a valve for controlling both flow rate and flow direction. The valving mechanism relies on a glass piston, which is placed on top of a mercury column, to open or block a capillary flow channel. The glass piston is actuated by the movement of the mercury column, and is based on an electrochemically induced change in the surface tension at the mercury-electrolyte interface. The position of the piston can be controlled by applying different voltages to the mercury electrode, which changes the surface tension of mercury, and hence the relative height of the mercury column in each of the two arms of a U-shaped tube. The extent of the piston displacement opens, closes, or partially opens the flow channel, thereby altering fluid flow rate. This paper presents the valving concept, and demonstrates its application in controlling both the rate and direction of fluid flow and in flow injection analyses.