Fabricating arrays of nanopores self-aligned with on-chip nanostructures
The fabrication of solid-state nanopores has typically been a time-consuming process that requires expensive equipment and trained operators. This process slowed the development of nanopore devices and limited their commercial viability. This is particularly true for nanopores that are integrated with complementary nanostructures.
Recently, a highly accessible technique called controlled breakdown (CBD) has been developed to fabricate solid-state nanopores. This method relies on applying a large electric field (0.4-1V/nm) across a membrane via electrolyte solutions to induce dielectric breakdown and nanopore formation. However, in its most used form, this technique can only create a single nanopore at a random location in the membrane and therefore cannot be used to create nanopore arrays or integrate nanopores with complementary nanostructures.
Researchers at the University of Oxford have extended the CBD protocol to enable the fabrication of nanopore arrays and self-align these nanopores with complementary nanostructures. This was demonstrated by applying the electric field between an on-chip electrode and an electrolyte solution in contact with the other side of the membrane. Performing this process using different on-chip electrodes enabled to keep the tense consistent independent fabrication of multiple nanopores in the membrane (one pore in each electrode).
The researchers have further extended this technique by passing a current through a metal nanoconstriction simultaneous to performing CBD. Passing a current through the metal nanoconstriction resulted in localised Joule heating of the membrane at the narrowest part of the constriction which confines nanopore formation to this region. This enabled the fabrication of nanopores precisely self-aligned with complementary nanostructures.
This method opens up routes for the easy fabrication of arrays of nanopores integrated with complementary nanostructures such as field-effect sensors, tunneling nanogaps, and plasmonic nanostructures. These complementary nanostructures can provide alternate detection modalities to ionic current based sensing typically used for nanopore sensing.
These alternate detection modalities can provide:
- increased device bandwidth,
- higher device densities, and;
- sensitivity to additional molecular properties.
Applications for such nanopore devices are diverse and range from DNA sequencing to informational polymer data storage and ultrasensitive analyte detection for diagnostics and disease monitoring.
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