Effect of Electro-Osmotic Flow on Energy Conversion on Superhydrophobic Surfaces

TL;DR

This paper investigates how superhydrophobic surfaces influence electro-osmotic flow and energy conversion, revealing significant reverse flow effects, potential for saturation in power output, and promising efficiency in micro-energy harvesting applications.

Contribution

It provides analytical and numerical analysis showing the impact of superhydrophobic geometries on electro-osmotic flow and energy conversion, highlighting saturation effects and realistic efficiency potentials.

Findings

Reverse electro-osmotic flow is significant in superhydrophobic geometries.

Saturation in power and efficiency occurs at high surface charge densities.

Microstructured superhydrophobic devices can achieve efficiencies comparable to nanostructured systems.

Abstract

It has been suggested that superhydrophobic surfaces, due to the presence of a no-shear zone, can greatly enhance transport of surface charges, leading to a considerable increase in the streaming potential. This could find potential use in micro-energy harvesting devices. In this paper, we show using analytical and numerical methods, that when a streaming potential is generated in such superhydrophobic geometries, the reverse electro-osmotic flow and hence current generated by this, is significant. A decrease in streaming potential compared to what was earlier predicted is expected. We also show that, due to the electro-osmotic streaming-current, a saturation in both the power extracted and efficiency of energy conversion is achieved in such systems for large values of the free surface charge densities. Nevertheless, under realistic conditions, such microstructured devices with superhydrophobic surfaces have the potential to even reach energy conversion efficiencies only achieved in nanostructured devices so far.