Electrokinetic flow in parallel channels: Circuit modelling for microfluidics and membranes

The ‘ion current model’ (ICM), a one-dimensional electrokinetic circuit model that incorporates ion charge conservation at circuit nodes, is extended to describe channels connected in parallel. If the number of parallel channels is M, then the ICM has M − 1 degrees of freedom, which means that the rates of fluid and ion transport within the parallel channels need not be distributed equally (even if the channels are identical). Using two-dimensional computational fluid dynamics (CFD) simulations of a simple network containing two parallel channels, we show that in a physical system the conductances (and hence, the flow behaviour) within each parallel channel are influenced by asymmetries within the system, including concentration polarisation. This observation suggests that by tuning channel arrangement, dimensions, and surface chemistry to achieve specific asymmetries, novel devices could be created for specific applications.