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 mech anism relies on a glass piston, which is placed on top of a mercury column, to open or block a capillary how channel. The glass piston is actuated by the movement of the mercury column, and is based on an electrochemically in duced change in the surface tension at the mercury-electrolyte interface. T he 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 p artially opens the flow channel, thereby altering fluid flow rate. This pap er presents the valving concept, and demonstrates its application in contro lling both the rate and direction of fluid flow and in flow injection analy ses. (C) 2001 Elsevier Science B.V. All rights reserved.