Minimizing the number of voltage sources and fluid reservoirs for electrokinetic valving in microfluidic devices

A microchip gated valve is demonstrated that uses a single voltage source a nd three fluid reservoirs. The fluidic valve is a cross intersection, and t he channels are dimensioned to perform the appropriate voltage division, si mplifying the voltage control hardware. A single voltage source is applied directly to the sample reservoir and through a high-voltage relay to the bu ffer reservoir, and the waste reservoir is grounded. The volume of sample d ispensed is determined by the duration that the high-voltage relay is open. Volumetric reproducibility is demonstrated to be <0.5% relative standard d eviation for volumes of greater than or equal to 20 pL. The valve is tested for the minimum applied voltage necessary for leakage-free operation, i.e. , sample diffusing from the cross intersection into the analysis channel. M oreover, appropriate channel dimensions are used to minimize the number of fluid reservoirs allowing effluent from the analysis and waste channels to be combined into a single reservoir.