Electroviscous flow through nanofluidic junctions

The steady-state electroviscous (pressure-driven) flow of an aqueous solution of potassium chloride through a nanofluidic borosilicate glass junction is modelled using a finite volume approach. Electric-field propagation through the glass section of the junction is included in the analysis. Channel half-widths of 20-70 nm and salt concentrations of 10-6-10-1 M are considered. Two types of common nano/microfluidic flow through the junction are analysed: a separating flow and a mixing flow. The hydrodynamic (pressure) and electrokinetic (electric potential) resistances of the junction are quantified in terms of equivalent lengths. For both flows, the hydrodynamic equivalent length of a 90° junction is found to be between ∼0.85 and ∼1.05 channel half-widths, while the electrokinetic equivalent length varies from ∼0.3 to ∼0.6 channel half-widths. Decreasing the junction angle decreases the equivalent lengths of the junction.