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In developing solid-state nanopore sensors for single molecule detection, comprehensive evaluation of the nanopore quality is important. Existing studies typically rely on comparing the noise root mean square or power spectrum density values. Nanopores exhibiting lower noise values are generally considered superior. This evaluation is valid when the single molecule signal remains consistent. However, the signal can vary, as it is strongly related to the solid-state nanopore size, which is hard to control during fabrication consistently. This work emphasized the need to report the baseline current for evaluating solid-state nanopore sensors. The baseline current offers insight into several experimental conditions, particularly the nanopore size. Our experiments show that a nanopore sensor with more noise is not necessarily worse when considering the signal-to-noise ratio (SNR), particularly when the pore size is smaller. Our findings suggest that relying only on noise comparisons can lead to inaccurate evaluations of solid-state nanopore sensors, considering the inherent variability in fabrication and testing setups among labs and measurements. We propose that future studies should include reporting baseline current and sensing conditions. Additionally, using SNR as a primary evaluation tool for nanopore sensors could provide a more comprehensive understanding of their performance.
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Sapphire-Supported Nanopores for Low-Noise DNA Sensing
Solid-state nanopore sensors have broad applications from single-molecule biosensing to diagnostics and sequencing. Prevalent nanopore sensors are fabricated on silicon (Si) substrates through micromachining, however, the high capacitive noise resulting from Si conductivity has seriously limited both their sensing accuracy and recording speed. A new approach is proposed here for forming nanopore membranes on insulating sapphire wafers by anisotropic wet etching of sapphire through micro-patterned triangular masks. Reproducible formation of small membranes with an average dimension of ~10 μm are demonstrated. For validation, a sapphire-supported (SaS) nanopore chip, with a 100 times larger membrane area than silicon-supported (SiS) nanopore, showed 130 times smaller capacitance (10 pF) and ~2.5 times smaller rootmean-square (RMS) noise current (~20 pA over 100 kHz bandwidth). Tested with 1k bp double-stranded DNA, the SaS nanopore enabled sensing at microsecond speed with a signal-to-noise ratio of 21, compared to 11 from a SiS nanopore. This SaS nanopore presents a manufacturable platform feasible for biosensing as well as a wide variety of MEMS applications.
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- PAR ID:
- 10253026
- Date Published:
- Journal Name:
- 2021 IEEE 34th International Conference on Micro Electro Mechanical Systems (MEMS)
- Page Range / eLocation ID:
- 354 to 357
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/MEMS51782.2021.9375372
