Influence of temperature gradients on charge transport in asymmetric nanochannels

Abstract

Charge selective asymmetric nanochannels are used for a variety of applications, such as nanofluidic sensing devices and energy conversion applications. In this paper, we numerically investigate the influence of an applied temperature difference over tapered nanochannels on the resulting charge transport and flow behavior. Using a temperature-dependent formulation of the coupled Poisson-Nernst-Planck and Navier-Stokes equations, various nanochannel geometries are investigated. Temperature has a large influence on the total ion transport, as the diffusivity of ions and viscosity of the solution are strongly affected by temperature. We find that the selectivity of the nanochannels is enhanced with increasing asymmetry ratios, while the total current is reduced at higher asymmetry cases. Most interestingly, we find that applying a temperature gradient along the electric field and along the asymmetry direction of the nanochannel enhances the selectivity of the tapered channels even further, while a temperature gradient countering the electric field reduces the selectivity of the nanochannel. Current rectification is enhanced in asymmetric nanochannels if a temperature gradient is applied, independent of the direction of the temperature difference. However, the degree of rectification is dependent on the direction of the temperature gradient with respect to the channel geometry and the electric field direction. The enhanced selectivity of nanochannels due to applied temperature gradients could result in more efficient operation in energy harvesting or desalination applications, motivating experimental investigations.

Ionic thermal up-diffusion in nanofluidic salinity-gradient energy harvesting

“…The relation of the temperature and the surface-charge density is fairly complex. Therefore, the assumption of constant surface-charge density is employed here [ 41 , 42 ]. Performances with varied surface-charge densities are analysed in the Supporting Information.…”

Electrodiffusioosmosis induced negative differential resistance in micro-to-millimeter size pores through a graphene/copper membrane

“…In the case of the nanopore, the overlapped electric double layer 13,14,17 , and in the case of meso (few 100s of nm) and sub-micron pore, the EOF is the root of the ICR mechanism 16 , 20 . The parameters responsible for ICR are the pore dimension 26 , surface charge density 17,20,21 , ionic solution composition (monovalent or multivalent ions) 27,29 , concentration gradient 30,31 , and external forces (pressure or temperature) 11,18,32,33 .…”

Thermoelectric effect and temperature-gradient-driven electrokinetic flow of electrolyte solutions in charged nanocapillaries

“…Additionally, Researchers also pay attention to effects of temperature gradient on the classic electrokinetic transport in micro/nanochannels. For example, the temperature gradient was found to have a substantial effect on the flow rate of pressure-driven electrokinetic flow in a microchannel [16], the ion selectivity of nanochannels [17,18] and the performance of nanofluidic reverse electro-dialysis system [19,20]. In nanochannels or nanopores, there exists another category of non-isothermal electrokinetic transport process driven by the temperature gradient alone (being referred to as the temperature-gradient-driven electrokinetic transport in this paper), which is the focus of this paper.…”