Electrokinetic energy conversion via nanochannel roughness engineering

Electrokinetic energy conversion in nanochannels is a promising technology for sustainable energy harvesting. However, the impact of surface roughness on power generation remains underexplored. In this study, we developed models of pressure-driven nanochannel flow featuring inward/outward semicircular surface roughness to study the roughness effects on fluid dynamics, ion distribution, and energy conversion. The study shows that inward roughness increases resistance, diminishes velocity, and leads to localized ion accumulation, whereas outward roughness exerts minor disruption on flow, and ions accumulate in the rough structure. Inward roughness leads to a more pronounced decrease in output power, but the impact of roughness on efficiency is relatively small. Reducing the channel length can narrow the output power gap between the two rough channels and the smooth channel. Under identical roughness parameters, the combination of small roughness height and a large number of roughness elements enables higher output performance. Furthermore, within the same range of roughness height ratio variation, expanding the channel radius yields significantly better performance improvements than adjusting roughness parameters, which can increase the power of inward and outward rough channels by 22-fold and 15-fold, respectively. This study elucidates the mechanism by which roughness orientation governs nanofluidic power generation, providing insights for optimizing channel design and improving energy conversion efficiency.