Towards the characterization of chemiosmotic flow of ionic liquids in charged nanochannels

Abstract

This study investigates the flow characteristics of a semi-diluted NaCMC–KCl aqueous solution in a charged nanochannel. A numerical model, consistent with ion transport mechanisms, is developed to analyze chemiosmotic flow under the influence of electrokinetic effects. The modeling framework employs a finite element-based approach to solve the governing equations and validate the theoretical predictions. We looked into how the bulk polyelectrolyte concentration, salt concentration in the left-side reservoir, and nanochannel height affect the mobile ions' space charge density, induced axial electric field, local viscosity, local and average flow velocity, and convective current. The findings show that the modulation of the degree of electrical-double layer (EDL) overlap with an increase in polyelectrolyte bulk concentration allows for an increase in mobile ion space charge density. The results of this analysis suggest that the concentrations of salt and polyelectrolyte have a significant impact on the local viscosity. The local viscosity increases with the increase in polyelectrolyte concentration and decreases with augmented left-side reservoir salt concentration. Furthermore, higher left-side reservoir salt concentrations result in an augmented convective current, while higher polyelectrolyte bulk concentrations lead to reduction of the same. Interestingly, modulation of the degree of EDL overlap with varied nanochannel heights yields non-intuitive flow patterns. In light of this, we established the critical bulk polyelectrolyte and left-side reservoir concentrations beyond which flow reversal occurs at greater nanochannel heights. The findings of this analysis are deemed pertinent to the development of state-of-the-art nanofluidic devices, largely used for chemiosmotic flow actuation of polyelectrolyte solutions.