Patterned electroconvection under AC and DC voltages with strong unipolar charge injection

Abstract

The phenomenon of electroconvection has attracted attention because it has the potential to improve ion transport on polarized surfaces, reducing the plateau region of limiting current. Previous observations for DC voltages indicate that patterned surfaces or unipolar charge injection significantly enhance ion transport through electroconvection. However, creating and maintaining the convection cells crucial for electroconvection is challenging under AC voltages due to the alternating direction of the electric field, which can cause instabilities. In this article, we explore how electroconvection can be induced using a patterned membrane and strong unipolar charge injection with both DC and AC voltages. We use a flow simulation with a specialized adaptive time-stepping algorithm to simulate electroconvection and find the best pattern ratio (R) for achieving the highest time-averaged current density. The system’s performance is assessed at different injection levels and mobility parameters across various frequencies. We compare patterned surfaces with homogeneous membranes. Our demonstration shows that an asymmetric patterned membrane with alternating cation-selective and ion-collector membranes can effectively alleviate the limitations posed by AC voltages to a significant extent. These findings contribute to optimizing ion transport under AC conditions, offering valuable insights for applications in biomedicine, micro/nanofluidics, and electrochemical systems, including DNA diagnostics, lab-on-a-chip devices, supercapacitors, and batteries where precise control of ion transport is essential.