Electromigration Current Rectification in a Cylindrical Nanopore Due to Asymmetric Concentration Polarization

Abstract

We present experimental measurements of electromigration current through a single cylindrical nanopore. A single cylindrical nanopore with 175 nm diameter was fabricated in silicon in series with two micropores with 2 and 100 microm diameters. Thick electrical double layers (EDLs) (kappa a approximately 1) exhibit current rectification due to asymmetric concentration polarization while thinner EDLs show nearly symmetric conductance. After the electric field is turned off, electrical current is measured and observed due to redistribution of ions in the concentration polarization layer.

Extended space charge in concentration polarization

“…This effect is specifically ESC related, and it should be clearly distinguished from anomalous current voltage characteristics and rectification effects at and in nanopores due to geometrical asymmetries [37], inhomogeneous fixed charge distribution [38], field focusing, or asymmetric CP [39][40][41]. Until the discovery of the Non-Equilibrium Electrokinetic Effects of the Second Kind, AR remained the only known macroscopic 'footprint' of ESC in CP.…”

Towards biomolecule-based information processing using engineered nanopores

“…A related concept that has been recently used for biomolecular detection is current rectification [40,80,94,13,90,11,97,49]. Many of the major aspects of current rectification and biosensing are summarised in the review of Siwy and Howorka [79].…”

“…Nanoscale pores and pore arrays can be produced in silicon, silicon oxide and silicon nitride membranes by focused-ion beam (FIB) [4,27] or electron beam (E-beam) [36] milling, or lithography and etch techniques [40,65,19,12,39]. Combinations of beam lithography and etching are also used [32,75].…”

What makes a nano-channel? A limiting-current criterion

“…They occur when the salt concentration at the polarized interface tends to zero, which leads to a strong increase in the electrical resistance and makes the passage of larger currents impossible. Although the concentration polarization phenomena at nano-/microinterfaces have already been described in the nanofluidic literature on numerous occasions (Datta et al 2006;Dhopeshwarkar et al 2008;Hlushkou et al 2008;Huang and Yang 2008a, b;Hughes et al 2008;Jin et al 2007;Jin and Aluru 2011;Jung et al 2009;Kelly et al 2009;Kim et al 2007Kim et al , 2010aMani et al 2009;Plecis et al 2008;Postler et al 2008;Zangle et al 2009), such a natural consequence of them as limiting current has been evoked just a couple of times (Dydek et al 2011;Kim et al 2007;Liu et al 2010;Nikonenko et al 2010;Yaroshchuk et al 2005) and mostly in general terms. The only exceptions are Yaroshchuk et al (2005) and the very recent Dydek et al (2011).…”