Electrokinetic ion rectification coupled with surface charge and thermal dependence in the conical nanochannel

Abstract

With the further development of nanotechnology, electrokinetic ion rectification (ICR) is receiving increasing attention. Since the chemical equilibrium boundary is more suitable for expressing the wall charging characteristics and the coincidence of asymmetric temperature with ICR, we first propose an ICR ion transport model that couples the chemical equilibrium boundary with asymmetric temperature. In this work, ICR under different electrical boundary conditions is studied. The effects of membrane thermal conductivity, solution pH, and geometric conditions on the rectification performance are further explored in combination with surface charge and temperature dependence. The results show that the rectification ratio of the constant σ model and constant ζ model has a significant deviation compared to the multi-ion model, and the electrical boundary conditions can be simplified by changing the external conditions. By controlling the thermal conductivity of the membrane, the distribution of temperature difference within the reservoir or nanochannel can be determined, which affects the enrichment or depletion of ions in the nanochannel and ultimately achieves the goal of optimizing the rectification ratio. The optimal ICR ratio can be obtained by adjusting pH, and optimizing geometric conditions can significantly improve rectification performance. These studies provide helpful information for ion transport control and optimization of micro/nanofluid devices.