Abstract
For nanopore sensing of various-sized molecules with high sensitivity, the size of the nanopore should be adjusted according to the size of each target molecule. For solid-state nanopores, a simple and inexpensive nanopore fabrication method utilizing dielectric breakdown of a membrane is widely used. This method is suitable for fabricating a small nanopore. However, it suffers two serious problems when attempting to fabricate a large nanopore: the generation of multiple nanopores and the non-opening failure of a nanopore. In this study, we found that nanopore fabrication by dielectric breakdown of a SiN membrane under high-pH conditions (pH ≥ 11.3) could overcome these two problems and enabled the formation of a single large nanopore up to 40 nm in diameter within one minute. Moreover, the ionic-current blockades derived from streptavidin-labelled and non-labelled DNA passing through the fabricated nanopore were clearly distinguished. The current blockades caused by streptavidin-labelled DNA could be identified even when its concentration is 1% of the total DNA.
Highlights
Nanopores have been widely used in recent years as a highly sensitive microscope that can observe various biomolecules in an aqueous solution
We report a method that enables the fabrication of a single large nanopore in a thick membrane by controlled breakdown (CBD) without the need for optics
SiN membranes with thicknesses of 20 nm were mainly used for the dielectric breakdown experiments
Summary
Nanopores have been widely used in recent years as a highly sensitive microscope that can observe various biomolecules in an aqueous solution. With the application of a high constant voltage to a membrane and termination of the voltage when the current between the electrodes reaches a predetermined cut-off value, a nanopore can be created in a membrane This method is called controlled breakdown (CBD)[35,36,39], which enables the fabrication of a small nanopore down to 1 nm in diameter. This problem seems to be solved if the time of the nanopore widening process, compared to the time to the first dielectric breakdown, can be sufficiently shortened In this context, a thicker membrane is expected to be suitable for the fabrication of a single large nanopore. The fabrication of a single large nanopore by CBD has been very difficult
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