Multifactorial Regulation Mechanisms of Negative Differential Resistance in Macropores.

The negative differential resistance (NDR) effect provides nonlinear control over ionic current and has important potential in ion sensing and information storage. A multiphys-ics numerical model is established using COMSOL Multiphysics 6.3, coupling the Poisson-Nernst-Planck and Navier-Stokes equations to investigate the effects of solution concentration gradient, pore length, pore diameter, and surface charge density on NDR effect. The results indicate that the NDR effect occurs only in the negative voltage range, where concentration gradient diffusion competes with electric field driven migration. The characteristic voltage window stabilizes between -0.2 V and -0.5 V, and the total current reaches a local extremum near -0.2 V. Electromigration dominates in this range and sup-presses Cl- ion diffusion, while K+ transport is less affected, resulting in decreased total ionic current. Under baseline conditions, the total current decreases by 26.19%, from -0.42 nA to -0.31 nA. Increasing the concentration gradient, shortening the pore length, enlarging the pore diameter, and reducing the surface charge density enhance local vortices or maintain Cl- diffusion pathways, thereby strengthening NDR characteristics. This study reveals the regulation mechanisms of NDR effect by solution conditions, macropore structures, and surface properties, providing theoretical guidance for tunable ionic current devices.