Bipotentiostatic Control Unlocks Flashing Ratchet Features in Ion Pumps

TL;DR

This paper demonstrates the first experimental realization of bipotentiostatic control in ion pumps, enabling flashing ratchet features that improve ion separation capabilities through frequency-dependent current reversal and tunable asymmetry.

Contribution

It introduces a novel bipotentiostat-driven approach to achieve flashing ratchet behavior in ion pumps, enhancing control and performance over previous methods.

Findings

Achieved frequency-dependent current reversal in ion pumps.

Enhanced device performance by an order of magnitude.

Enabled tuning of asymmetry through potential offset.

Abstract

The selective separation of same-charge ions is a longstanding challenge in resource recovery, battery recycling, and water treatment. Theoretical studies have shown that ratchet-based ion pumps (RBIPs) can separate ions with the same charge and valance by driving them in opposite directions according to their diffusion coefficients. This process relies on frequency dependent current reversal, a unique feature of ratchets in which the particle current direction is inverted with the input signal frequency. Previous experimental demonstrations of RBIPs achieved ion pumping against electrostatic forces and water deionization, but lacked frequency-dependent current reversal and control of the asymmetry of the device. Here, we report the first experimental realization of these key functionalities by driving RBIPs with a bipotentiostat. Complementary input signals applied to RBIP contacts unlock a flashing ratchet-like behavior, and enhances the device performance by an order of magnitude compared to the prior floating-drive approach. The enhanced control of the electrostatic potential at the RBIP surfaces leads to frequency dependent current reversals, and the addition of a potential offset to the input signal enables tuning the amplitude asymmetry of the device. This flashing ratchet functionality provides a significant step towards the realization of ratchet driven selective ion separation systems.