Joule Heating Effects on Transport-Induced-Charge Phenomena in an Ultrathin Nanopore.

Zhixuan Wang,Amer Alizadeh,Hirofumi Daiguji,Soumyadeep Paul,Wei-Lun Hsu,Shuntaro Tsuchiya

doi:10.3390/mi11121041

Abstract

Transport-induced-charge (TIC) phenomena, in which the concentration imbalance between cations and anions occurs when more than two chemical potential gradients coexist within an ultrathin dimension, entail numerous nanofluidic systems. Evidence has indicated that the presence of TIC produces a nonlinear response of electroosmotic flow to the applied voltage, resulting in complex fluid behavior. In this study, we theoretically investigate thermal effects due to Joule heating on TIC phenomena in an ultrathin nanopore by computational fluid dynamics simulation. Our modeling results show that the rise of local temperature inside the nanopore significantly enhances TIC effects and thus has a significant influence on electroosmotic behavior. A local maximum of the solution conductivity occurs near the entrance of the nanopore at the high salt concentration end, resulting in a reversal of TIC across the nanopore. The Joule heating effects increase the reversal of TIC with the synergy of the negatively charged nanopore, and they also enhance the electroosmotic flow regardless of whether the nanopore is charged. These theoretical observations will improve our knowledge of nonclassical electrokinetic phenomena for flow control in nanopore systems.

Highlights

Ultrathin nanopores are artificial apertures of nanoscale dimensions on sub-100 nm inorganic membranes [1]
The results indicated that the TIC EOF is dominant at the high applied electric potential difference (∼ 1 V) compared with the conventional electroosmotic flow originating from the electrical double layer (EDL) (EDL EOF)
Joule heating effects on TIC phenomena in an ultrathin nanopore have been investigated by numerical simulation

Summary

Introduction

Ultrathin nanopores are artificial apertures of nanoscale dimensions on sub-100 nm inorganic membranes [1]. To further pursue the improved performance and accuracy of these applications, it is vital to examine the ion and flow behaviors in ultrathin nanopores from a fundamental perspective When these nanopores are immersed in an electrolyte solution, the positively/negatively charged surface results in the selectivity of ions that renders higher penetration of anions/cations over their counterparts, as long as an electric potential difference is present across the membrane. As the membrane becomes considerably thin, the interaction between the strong electric field and the steep concentration gradient promotes local ion separation, resulting in a net space charge outside the electrical double layer (EDL) This phenomenon, known as transport-induced-charge (TIC) effects [7], disturbs the ionic distributions in the nanopores and considerably influences the electroosmotic behavior. The impact of TIC on the electroosmosis behavior is evaluated, which may enrich our understanding of complex electrokinetic phenomena in ultrathin nanopores

Computational Modeling

Mechanism of TIC Phenomena

Effects of Joule Heating on Electroosmotic Flow Due to the Presence of TIC

Findings

Conclusions