Ionic Memcapacitive Effects in Nanopores

TL;DR

This study demonstrates that nanopores in ionic solutions exhibit memcapacitive behavior with hysteresis and negative capacitance under periodic electric fields, due to ionic polarizability and transport mechanisms, with potential applications in DNA sequencing and neuroscience.

Contribution

The paper introduces a microscopic model explaining memcapacitive effects in nanopores, supported by molecular dynamics simulations, and proposes experimental tests and biological implications.

Findings

Nanopores act as memcapacitors with hysteresis under AC electric fields.

Negative and diverging capacitance observed as a function of voltage.

Ionic transport through nanopores may contribute to biological memory mechanisms.

Abstract

Using molecular dynamics simulations, we show that, when subject to a periodic external electric field, a nanopore in ionic solution acts as a capacitor with memory (memcapacitor) at various frequencies and strengths of the electric field. Most importantly, the hysteresis loop of this memcapacitor shows both negative and diverging capacitance as a function of the voltage. The origin of this effect stems from the slow polarizability of the ionic solution due to the finite mobility of ions in water. We develop a microscopic quantitative model which captures the main features we observe in the simulations and suggest experimental tests of our predictions. We also suggest a possible memory mechanism due to the transport of ions through the nanopore itself, which may be observed at small frequencies. These effects may be important in both DNA sequencing proposals using nanopores and possibly in the dynamics of action potentials in neurons.