Use of tunable nanopore blockade rates to investigate colloidal dispersions

TL;DR

This study demonstrates how tunable nanopores can be used to investigate colloidal dispersions by analyzing ionic current blockade rates, which depend on particle properties and applied conditions, with potential for detailed pore geometry control.

Contribution

The paper introduces a novel application of elastomeric nanopores for studying colloidal particles through blockade rate analysis, integrating mechanical tuning and microscopy visualization.

Findings

Blockade rate linearly depends on pressure and concentration.

Transport modeled accurately with Nernst-Planck theory.

Pore geometry changes with strain and affects ionic current.

Abstract

Tunable nanopores in elastomeric membranes have been used to study the dependence of ionic current blockade rate on the concentration and electrophoretic mobility of particles in aqueous suspensions. A range of nanoparticle sizes, materials and surface functionalities has been tested. Using pressure-driven flow through a pore, the blockade rate for 100 nm carboxylated polystyrene particles was found to be linearly proportional to both transmembrane pressure (controlled between 0 and 1.8 kPa) and particle concentration (between 7 x 10^8 and 4.5 x 10^10 mL^-1). This result can be accurately modelled using Nernst-Planck transport theory. Using only an applied potential across a pore, the blockade rates for carboxylic acid and amine coated 500 nm and 200 nm silica particles were found to correspond to changes in their mobility as a function of the solution pH. Scanning electron microscopy and confocal microscopy have been used to visualise changes in the tunable nanopore geometry in three dimensions as a function of applied mechanical strain. The pores observed were conical in shape, and changes in pore size were consistent with ionic current measurements. A zone of inelastic deformation adjacent to the pore has been identified as critical in the tuning process.