The concept of entropic rectifier facing experiments

TL;DR

This paper experimentally investigates how entropic barriers in confined media can induce ionic current rectification, demonstrating that ion size and cycle frequency influence the rectification effect consistent with entropic ratchet theory.

Contribution

It provides experimental evidence for entropic ratchet mechanisms in ionic transport through neutral conical nanopores, highlighting the role of ion size and frequency.

Findings

Ionic current rectification depends on ion size and cycle frequency.

Rectification observed is consistent with entropic ratchet mechanism.

Experimental validation of theoretical predictions about entropic barriers.

Abstract

The transport of molecules in confined media is subject to entropic barriers. So theoretically, asymmetry of the confinement length may lead to molecular ratchets with entropy as the only driving force for the biased transport. We address experimentally this question by performing alternative ionic current measurements on electrolytes confined in neutral conical nanopores. In case anions and cations widely differ in size, we show that rectification of ionic current can be obtained that depends on ions size and cycle frequency, consistently with the entropic ratchet mechanism.