Sapphire-Supported Nanopores for Low-Noise DNA Sensing

Silicon-supported (SiS) solid-state nanopores have broad applications in single-molecule biosensing and diagnostics, but their high capacitive noise has seriously limited both their sensing accuracy and recording speed. Nanopores on insulating glass have demonstrated reduced capacitance and noise, but it remains challenging to bulk-etch amorphous glass to create membranes reproducibly and uniformly. Here a new approach is reported to form triangular sapphire-supported (SaS) nanopore membranes by batch-processing-compatible anisotropic wet etching of sapphire, with membrane dimension demonstrated from ~200 um to 5 um. A SaS nanopore in 68 um-wide silicon nitride membrane has 130 times smaller capacitance (10 pF) compared to a SiS nanopore (~4 um SiN membrane, ~1.3 nF), despite a 100 times larger membrane. It has a current noise of 18 pA over 100 kHz bandwidth, much smaller than that from our SiS nanopore (46 pA) and comparable with the best reported low-noise nanopores. Further, the SaS nanopore displays a higher signal-to-noise ratio (SNR, 21 versus 11 for SiS nanopore) in DNA sensing, although the SNR can be further improved using thinner membranes and smaller pores. The SaS nanopore presents a simple platform in both fabrication and structure that is particularly suitable for low-noise and high-speed molecular diagnostics.