Bioinspired fractal nanochannels for high-performance salinity gradient energy conversion

Bioinspired nanofluidic systems have shown a promising application in ion transport tuning and energy conversion. Here, we have numerically investigated the ionic current rectification behavior and power generation via bioinspired fractal nanochannels. Fractal nanochannels can present a strong ionic current rectification effect due to the asymmetric distribution of the electrical double layer overlapping induced by the fractal geometry. At a concentration of 200 mM, the ionic current rectification factor in the trifurcated nanochannel is almost improved by 100%, compared to that in the bifurcated nanochannel. Moreover, ionic current can rectify at much higher salt concentrations in trifurcated nanochannel. Fractal nanochannels can considerably improve the power density and energy conversion efficiency for enhanced osmotic current, diffusive voltage and ion selectivity originating from considerably improved electrical double layer overlapping degree. At a concentration ratio of 1000-fold, compared to the straight nanochannel, the power densities of the bifurcated and trifurcated nanochannels are, respectively, improved by 153% and 357% while the energy conversion efficiency are augmented by 147% and 336%. Furthermore, the salt dependent ion transportation and power generation via the furcated nanochannels are also discussed. This paper may contribute to designing appropriate artificial nano-fluidic systems for efficient ion transport tuning and energy conversion.