Temperature-regulated surface charge manipulates ionic current rectification in tapered nanofluidic channel

Diverse ionic current rectification methods for nanofluidic chips have recently emerged. Herein, we theoretically demonstrate that by applying a temperature gradient to the aqueous solution, the ionic rectification property of a tapered nanochannel can be manipulated by applying temperature gradients from the tip to base and vice versa. Our modeling results reveal that the rectification ratio can be significantly enhanced by applying a temperature increment from the base to tip, whereas the rectification ratio is significantly suppressed by applying a reverse temperature gradient. In addition to the solution temperature, we also investigated the influence of bulk ionic strength and tip height on the rectification ratio, thereby providing overlapping and non-overlapping regimes of electrical double layers. We demonstrate that the rectification behavior of a tapered nanochannel is determined by the overlapping regime of the electrical double layer at the tip of the nanochannel. Moreover, we propose a semi-analytical solution that can capture numerical results with the same order of magnitude. We expect that the modeling results of this contribution can provide a direction for understanding ionic transport across geometrically and thermally asymmetrical media, which could find applications from energy conversion to logical nanofluidic chip components.