Electrodrying in nanopores: from fundamentals to iontronic and memristive applications

TL;DR

This paper introduces electrodrying, a novel method to control nanopore conductance using voltage to dry hydrophobic pores, enabling memristive behavior and potential applications in neuromorphic and iontronic devices.

Contribution

It presents the concept of electrodrying, combining analytical modeling, simulations, and experiments to demonstrate bidirectional conductance control and memristor-like properties in nanopores.

Findings

Electrodrying induces hysteresis and negative differential resistance in nanopores.

The phenomenon enables memristor behavior with potential neuromorphic applications.

Experimental validation on engineered nanopores supports the theoretical predictions.

Abstract

Iontronics is a burgeoning paradigm that employs ions in solution as information carriers for sensing and computing, e.g., in neuromorphic devices. The fundamentally different working principle as compared to electronics requires novel approaches and concepts to control the impedance of nanoscale fluidic circuit elements, such as nanopores. For instance, previous research has focused on voltage-induced pore wetting as a means to trigger conduction in nanopores. The present study explores the opposite counter-intuitive mechanism: using voltage to dry hydrophobic nanopores and, therefore, to turn off conduction. This "electrodrying" concept affords exquisite, bidirectional control over the conductance of nanopores additionally showing hysteresis in the current-voltage curve that is the fingerprint of memristors. Using an analytical model and free-energy molecular dynamics simulations, we explain the physical mechanism underlying electrodrying and provide clear design criteria for solid-state and biological nanopores with bidirectional control over conductance. The electrical behaviour of electrodrying nanopores shows two unique features: i) the hysteresis loop is shifted from the origin, accounting for the fifth, previously unreported memristor type and ii) negative differential resistance is observed over a broad voltage range in which the non-conductive state is favoured by electrodrying. These properties are demonstrated in a short-term memory task and in an iontronic oscillator circuit to showcase their potential in neuromorphic applications and iontronic devices. Finally, we validate our predictions through experiments on engineered dipolar hydrophobic CytK nanopores, whose voltage-dependent conductance substantiates the electrodrying concept.