The electrokinetic flow resistance (electroviscous effect) in steady state, pressure-driven liquid flow in a slit-like microfluidic contraction at low Reynolds number is predicted using a finite volume numerical method. A uniform charge density is assumed on the channel walls and the liquid is taken to be a symmetric 1:1 electrolyte. Predictions of the apparent viscosity are shown to be well described by a simple theory that calculates the pressure drop along the channel by adding the pressure losses in the inlet, contraction and outlet sections (based on the classical electrokinetic flow solution in a uniform slit) to the entry and exit losses due to the contraction. These entry and exit losses are approximated using the low Reynolds number analytical solution for a slit orifice without electrokinetic effects
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