Electroosmotic flow profile distortion due to Laplace pressures at the end reservoirs

Abstract

The build-up of pressure-driven backflows is a known drawback to electroosmotic plug flow. We have studied the characteristic time constant of these pressure gradients build-up as a function of various geometrical variables of the problem through μPIV measurements. Previous models based on hydrostatic pressure difference (syphoning) cannot explain the dynamics of our experimental results. We have developed a model that relates these pressure-driven backflows to Laplace pressures, due to changes in the interface radii of curvature at the reservoirs. This model leads to an equation which was solved both numerically and, after linearisation, analytically. The characteristic time constants obtained show much better agreement with experimental data. Therefore, this model allows for predicting the time during which an acceptable electroosmotic flow profile will last for a given microchannel?reservoir design.