Impacts of the temperature-dependent properties on ion transport behavior in soft nanochannels

Abstract

The influence of the temperature- and concentration-dependent properties, derived from the gradients of temperature and concentration, on the ionic selectivity, ionic current rectification, Joule heating, and viscosity dissipation in conical soft nanochannels was numerically investigated. Both co-current an counter-current modes of operation, in terms of implementing temperature- and concentration gradients, were considered. Since it was assumed that the nanochannel is coated with a dense polyelectrolyte layer, the ionic partitioning effect was also considered. Through adopting a numerical approach, Poisson–Nernst–Planck, Navier–Stokes, and energy equations were solved at steady-state conditions by considering different values of permittivity, diffusivity, and viscosity for the PEL and the electrolyte. The most important result of this study is that under an applied voltage, by increasing the temperature and concentration ratios, the Joule heating increased. For instance, at counter-current mode, by increasing the concentration ratio from 1 to 100, the Joule heating increased from 1 nW to 3.5 nW. It was also realized that upon applying an external voltage of Vapp = − 5 V, the Joule heating reaches a value of 130 nW. As such, it was concluded that the lack of control in the generation of Joule heating would harm the transport behavior of ionic species within soft nanochannels.