TEM study of locally coated nanopore fabricated by ion-beam-induced deposition in a thin membrane

Controllable Shrinking Fabrication of Solid-State Nanopores

Nanopores have attracted widespread attention in DNA sequencing and protein or biomarker detection, owning to the single-molecule-scale detection accuracy. Despite the most use of naturally biological nanopores before, solid-state nanopores are widely developed with strong robustness, controllable sizes and geometries, a wide range of materials available, as well as flexible manufacturing. Therefore, various techniques typically based on focused ion beam or electron beam have been explored to drill nanopores directly on free-standing nanofilms. To further reduce and sculpt the pore size and shape for nano or sub-nano space-time sensing precision, various controllable shrinking technologies have been employed. Correspondingly, high-energy-beam-induced contraction with direct visual feedback represents the most widely used. The ability to change the pore diameter was attributed to surface tension induced original material migration into the nanopore center or new material deposition on the nanopore surface. This paper reviews typical solid-state nanopore shrinkage technologies, based on the careful summary of their principles and characteristics in particularly size and morphology changes. Furthermore, the advantages and disadvantages of different methods have also been compared completely. Finally, this review concludes with an optimistic outlook on the future of solid-state nanopores.

Fabrication and characterization of solid-state nanopore arrays for high-throughput DNA sequencing

We report the fabrication and characterization of uniformly sized nanopore arrays, integrated into an optical detection system for high-throughput DNA sequencing applications. Nanopore arrays were fabricated using focused ion beam milling, followed by TiO(2) coating using atomic layer deposition. The TiO(2) layer decreases the initial pore diameter down to the sub-10 nm range, compatible with the requirements for nanopore-based sequencing using optical readout. We find that the TiO(2) layers produce a lower photoluminescence background as compared with the more widely used Al(2)O(3) coatings. The functionality of the nanopore array was demonstrated by the simultaneous optical detection of DNA-quantum dot conjugates, which were electro-kinetically driven through the nanopores. Our optical scheme employs total internal reflection fluorescence microscopy to illuminate a wide area of the TiO(2)-coated membrane. A highly parallel system for observing DNA capture events in a uniformly sized 6 × 6 nanopore array was experimentally realized.

SEM-induced shrinking of solid-state nanopores for single molecule detection

We have investigated the mechanism by which the diameter of solid-state nanopores is reduced by a scanning electron microscope. The process depends on beam parameters such as the accelerating voltage and electron flux and does not involve simple electron-beam-induced deposition of hydrocarbon contaminants. Instead, it is an energy-dependent process that involves material flow along the surface of the nanopore membrane. We also show that pores fabricated in this manner can detect double stranded DNA.