A novel nanopore fabrication method is reported by thermally pulling a glass tube in a two step process. The principle is based on the physical footprint of the phase change of the paraffin sealed inside the glass tube to form a nanocavity in the broken terminal during the second step of the pulling process. A nanopore with minimum diameter of 40nm is fabricated after rubbing the terminal to make the channel through it. IgG molecules are used to test whether the nanopore can discriminate biomolecules. A transient current change from increasing to decreasing was observed when IgG molecules passed through the nanopore in pure water, suggesting that the IgG has a Y-shaped structure. This is in agreement with the known IgG structure. Experiments also uncovered that the train pulse signals due to the translocation of the biomolecules are sensitive to salt solutions. It was found that the negative amplitude of the pulse signal can be screened while the IgG molecules are mixed with a low KCL concentration solution. When changing from low to high salt concentrations we observed an inversion of the peak orientation. This is attributed to the competing conductance contribution to the ionic currents from the charges carried by the IgG molecules themselves and the exclusive ions blocked by the IgG molecules, suggesting that the salt ions in the solution may hide the true biomolecule structure.
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