Conductivity-based detection techniques in nanofluidic devices

Abstract

This review covers conductivity detection in fabricated nanochannels and nanopores. Improvements in nanoscale sensing are a direct result of advances in fabrication techniques, which produce devices with channels and pores with reproducible dimensions and in a variety of materials. Analytes of interest are detected by measuring changes in conductance as the analyte accumulates in the channel or passes transiently through the pore. These detection methods take advantage of phenomena enhanced at the nanoscale, such as ion current rectification, surface conductance, and dimensions comparable to the analytes of interest. The end result is the development of sensing technologies for a broad range of analytes, e.g., ions, small molecules, proteins, nucleic acids, and particles.

Through a Window, Brightly: A Review of Selected Nanofabricated Thin-Film Platforms for Spectroscopy, Imaging, and Detection

“…24,113,[217][218][219][220][221] Passage of an analyte through the nanopore can generate a perturbation in the measured current that arises from physical displacement of solution ions by the analyte and from more complex interactions between charges in solution and on the surface of the analyte and nanopore. 24,28,52,[221][222][223] It is convenient to generically refer to the current perturbations as ''blockages,'' although analyte properties and sensing conditions may lead even to current enhancements. 221 With suitable nanopore and experimental design, the measured current perturbation generates a signal from a single molecule at a time that can be used for chemical identification or profiling.…”

“…The insulating, impermeable SiN x thus acts as a physical barrier and as a support for the channel through which ions and molecules can pass under the influence of an electric field or other suitable driving force. [21][22][23][24][25][26][27][28][29][211][212][213][214][215][216] The most common sensing configuration is the so-called resistive-pulse sensing mode (Fig. 10).…”

“…The use of silicon nitride windows in creating sample cells and chambers has become increasingly prevalent, as has their use as sample supports; their use as a platform to host structural elements such as nanofluidic channels is a relatively new area of application and investigation. [16][17][18][19][20][21][22][23][24][25][26][27][28][29] Two particularly compelling uses of thin-film windows are shown in Fig. 1 and Fig.…”

“…[21][22][23][24][25][26][27][28][29] Extension of this single pore design to many pores allows the same thin-film platform to function as a high-throughput filter, with implications also for nanoplasmonics. 60,61 There are excellent reviews focusing on these two particular implementations alone, [21][22][23][24][25][26][27][28][29]38,40 and a recent book chapter reviewing both in a unifying context of nanofluidics. 20 We hope the present review will encourage an appreciation of the breadth of application of even an ostensibly prosaic free-standing thin-film structure across a host of spectroscopy, microscopy, and sensing techniques.…”

“…[17][18][19] Thin films with suitable properties and structures can also be used in a more active role in experimental studies: a $10 nm diameter channel through a < 100 nm thick thin film-a so-called nanopore-is the basis for a wide range of single molecule sensing and manipulation methods that emerge from the passage of a molecule into, or through, the nanofluidic channel. [20][21][22][23][24][25][26][27][28][29] Figure 1 offers two illustrations to illuminate the rich scope of experimental configurations and possibilities using just these two platforms. We will frame our discussion of the interplay between thin-film design-composition and structureand application by using these two quite different implementations: a sample cell with thin-film windows bracketing a nanofluidic channel; and a nanopore single molecule sensor platform where the robust thin film supports a nanofluidic through-channel.…”