Effects of the electric field distribution on microchip valving performance

Valving characteristics on microfluidic devices were controlled through man ipulation of the electric field strengths during both the sample loading an d dispensing steps. Three sample loading profiles for the constant volume v alve (pinched injection) in conjunction with four dispensing schemes were i nvestigated to study valving performance. The sample confinement profiles f or the sample loading step consisted of a weakly pinched sample, a medium p inched sample, and a strongly pinched sample. Four dispensing schemes varie d the electric field strengths in the sample and sample waste channels rela tive to the analysis channel to control the volume of the sample dispensed from the valve. The axial extent of the sample plug decreased as the electr ic field strengths in the sample and sample waste channels were raised rela tive to the analysis channel. In addition, a trade-off existed between samp le plug length and sensitivity.