ABSTRACT
Solid-state nanopores are emerging as a valuable tool for the detection and characterization of individual biomolecules. Central to their success is the realization of fabrication strategies that are both rapid and flexible in their ability to achieve diverse device dimensions. In this paper, we demonstrate the membrane thickness dependence of solid-state nanopore formation with a focused helium ion beam. We vary membrane thickness in situ and show that the rate of pore expansion follows a reproducible trend under all investigated membrane conditions. We show that this trend shifts to lower ion dose for thin membranes in a manner that can be described quantitatively, allowing devices of arbitrary dimension to be realized. Finally, we demonstrate that thin, small-diameter nanopores formed with our approach can be utilized for high signal-to-noise ratio resistive pulse sensing of DNA.
Subject(s)
Conductometry/instrumentation , DNA/analysis , Helium , Membranes, Artificial , Nanoparticles/ultrastructure , Nanopores/ultrastructure , Silicon Compounds/chemistry , DNA/genetics , Equipment Design , Equipment Failure Analysis , Heavy Ions , Materials Testing , Nanoparticles/chemistry , Nanoparticles/radiation effects , Silicon Compounds/radiation effects , Surface Properties/radiation effectsABSTRACT
While conventional solid-state nanopore measurements utilize ionic current, there is a growing interest in alternative sensing paradigms, including optical detection. However, a limiting factor in the application of optical schemes in particular is the inherent background fluorescence created by the solid-state membrane itself, which can interfere with the desired signal and place restrictions on the fluorophores that can be employed. An ideal device would incorporate a localized reduction in membrane fluorescence using a method that can be integrated easily with the nanopore fabrication process. Here, we demonstrate that in addition to forming nanopores and nanopore arrays, a focused helium ion beam can be used to reduce the fluorescence of a conventional silicon nitride membrane controllably. The reduction in background produces low-fluorescence devices that can be used for optical detection of double-strand DNA, as well as for conventional resistive pulse sensing. This approach is used to identify the translocation of short single-strand DNA through individual nanopores within an array, creating potential for a massively-parallel detection scheme.
