ELECTROKINETIC ENERGY CONVERSION AT LOW IONIC STRENGTH: NANOSCALE TOPOGRAPHY AND SURFACE CONDUCTION

This work reports experimental and theoretical results on how nanoscale surface topography influences electrokinetic energy conversion across a broad range of ionic strengths (0.01 to 10 mM) for aqueous solutions of 1:1 electrolytes in slit micro/nanochannels with hydrophilic and hydrophobic surfaces. At very low ionic strengths, below 1 mM, where the bulk electrical conductivity of the electrolyte solution is minimal, surface conductivity increases due to nontrivial interfacial transport phenomena and becomes a dominant factor determining the mechanical-to-electrical energy conversion efficiency. The increase in surface conductance can significantly hinder the performance of different electrokinetic micro/nanofluidic devices operating at low electrolyte concentrations. These results offer new insights into electrokinetic flow on different surfaces and suggest practical strategies for controlling or mitigating surface conductivity. This work thus advances our understanding of electrokinetic flows and paves the way for optimizing the design of micro/nanofluidic devices for applications in sustainable and green energy conversion and storage.