Dynamic Response of Ionic Current in Conical Nanopores

TL;DR

This study uses time-dependent simulations to analyze how various parameters influence the dynamic ionic current response in conical nanopores, providing insights for designing nanofluidic devices like memristors and ionic switches.

Contribution

It reveals the response time mechanisms of ionic current in conical nanopores and how they are affected by nanopore parameters and external conditions, advancing nanofluidic device design.

Findings

Response time is longer during ion enrichment formation.

Surface charge density and pore length significantly affect response time.

Voltage and bulk concentration also influence the dynamic response.

Abstract

Ionic current rectification (ICR) of charged conical nanopores has various applications in fields including nanofluidics, bio-sensing, and energy conversion, whose function is closely related to the dynamic response of nanopores. The occurrence of ICR originates from the ion enrichment and depletion in conical pores, whose formation is found to be affected by the scanning rate of voltages. Here, through time-dependent simulations, we investigate the variation of ion current under electric fields and the dynamic formation of ion enrichment and depletion, which can reflect the response time of conical nanopores. The response time of nanopores when ion enrichment forms i.e. at the on state is significantly longer than that with the formation of ion depletion i.e. at the off state. Our simulation results reveal the regulation of response time by different nanopore parameters including the surface charge density, pore length, tip, and base radius, as well as the applied conditions such as the voltage and bulk concentration. The response time of nanopores is closely related to the surface charge density, pore length, voltage, and bulk concentration. Our uncovered dynamic response mechanism of the ionic current can guide the design of nanofluidic devices with conical nanopores, including memristors, ionic switches, and rectifiers.