How the dielectric effect regulates energy conversion of nanofluidic pores

Abstract

Electrokinetic energy conversion of electro-osmotic flow through charged nanoscale pores has attracted growing interest due to its promising potential in sustainable energy harvesting. This work focuses on dielectric regulation of energy conversion efficiency of electro-osmotic flow. To accurately describe the dielectric effect, we employ an energetic variational approach to develop a modified Poisson–Nernst–Planck–Navier–Stokes (mPNP-NS) framework that self-consistently incorporates ionic Born self-energy and inhomogeneous dielectrics due to the hydrophobicity of the pore wall. Lubrication–approximation analysis reveals that the leading-order solution to the mPNP-NS model satisfies the well-known Onsager reciprocal relations between fluxes and driving forces. Systematic numerical investigations demonstrate that tailored dielectric regulation can effectively enhance energy conversion efficiency through more favorable alignment between net ionic charge and large fluid velocity. Numerical studies also reveal a profound interplay between the dielectric profile, pore sizes, surface charge density, and bulk electrolyte concentration and their subtle synergistic impact on energy conversion efficiency. These findings highlight dielectric regulation as a new interfacial mechanism for boosting energy conversion efficiency and provide valuable insights on material selection and surface engineering for high-performance electrokinetic devices.