title: Use of tunable nanopore blockade rates to investigate colloidal dispersions.
abstract: Tunable nanopores fabricated 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 (between 0 and 1.8 kPa) and particle concentration (between 7 × 10(8) and 4.5 × 10(10) ml( - 1)). This result can be accurately modelled using Nernst-Planck transport theory, enabling measurement of particle concentrations. Using only an applied potential across a pore, the blockade rates for carboxylic acid and amine coated 500 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 visualize changes in the tunable nanopore geometry in three dimensions as a function of applied mechanical strain. The pores 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 important in the tuning process.
authors.affiliation: The MacDiarmid Institute of Advanced Materials and Nanotechnology, Industrial Research Limited, PO Box 31310, Lower Hutt 5040, New Zealand. g.willmott@irl.cri.nz
authors.forename: G R
authors.initials: GR
authors.lastname: Willmott
authors.forename: R
authors.initials: R
authors.lastname: Vogel
authors.forename: S S C
authors.initials: SS
authors.lastname: Yu
authors.forename: L G
authors.initials: LG
authors.lastname: Groenewegen
authors.forename: G S
authors.initials: GS
authors.lastname: Roberts
authors.forename: D
authors.initials: D
authors.lastname: Kozak
authors.forename: W
authors.initials: W
authors.lastname: Anderson
authors.forename: M
authors.initials: M
authors.lastname: Trau
mesh_terms: D003102:Colloids / Q000737:chemistry*; D003460:Crystallization / Q000379:methods*; D004586:Electrophoresis / Q000379:methods*; D008422:Materials Testing / Q000379:methods; D008567:Membranes, Artificial; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D016062:Porosity; D011312:Pressure; D013499:Surface Properties
chemical_list: D003102:Colloids; D008567:Membranes, Artificial