Tuning the nanopore diameter using ALD

Working on deep deep nano holes and tubes for a long time (DRAM) and for a lab growing nanowires I found this an interesting paper on how ALD can be used to tune the nanopore diameter. Nanopore (NP) technologies have been researched the last 10 years or so. According to the paper "The next major breakthrough" of this technology will depend on :

• the fundamental understanding of the dynamical processes that govern macromolecules translocation through NP
• the availability of methods that allow routine fabrication of nanoscale materials. 

Particles, holes, tubes, wires, pores, ..., transistors etc. - what else could you do nano?

Influence of nanopore surface charge and magnesium ion on polyadenosine translocation

Mathilde Lepoitevin, Pierre Eugène Coulon, Mikhael Bechelany, Julien Cambedouzou, Jean-Marc Janot and Sebastien Balme
Mathilde Lepoitevin et al 2015 Nanotechnology 26 144001
doi:10.1088/0957-4484/26/14/144001

We investigate the influence of a nanopore surface state and the addition of Mg2+ on poly-adenosine translocation. To do so, two kinds of nanopores with a low aspect ratio (diameter ~3–5 nm, length 30 nm) were tailored: the first one with a negative charge surface and the second one uncharged. It was shown that the velocity and the energy barrier strongly depend on the nanopore surface. Typically if the nanopore and polyA exhibit a similar charge, the macromolecule velocity increases and its global energy barrier of entrance in the nanopore decreases, as opposed to the non-charged nanopore. Moreover, the addition of a divalent chelating cation induces an increase of energy barrier of entrance, as expected. However, for a negative nanopore, this effect is counterbalanced by the inversion of the surface charge induced by the adsorption of divalent cations.

Cartoon to illustrate polyA translocation through NP and the electrolyte distribution. (a) Native -NP at NaCl 150 mM (b) native-NP at NaCl 500 mM and (c) TMS-NP at NaCl 150 mM.

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