Plasmonic and nanopore sensors have separately received much attention for achieving single‐molecule precision. A plasmonic “hotspot” confines and enhances optical excitation at the nanometer length scale sufficient to optically detect surface–analyte interactions. A nanopore biosensor actively funnels and threads analytes through a molecular‐scale aperture, wherein they are interrogated by electrical or optical means. Recently, solid‐state plasmonic and nanopore structures have been integrated within monolithic devices that address fundamental challenges in each of the individual sensing methods and offer complimentary improvements in overall single‐molecule sensitivity, detection rates, dwell time and scalability. Here, the physical phenomena and sensing principles of plasmonic and nanopore sensing are summarized to highlight the novel complementarity in dovetailing these techniques for vastly improved single‐molecule sensing. A literature review of recent plasmonic nanopore devices is then presented to delineate methods for solid‐state fabrication of a range of hybrid device formats, evaluate the progress and challenges in the detection of unlabeled and labeled analyte, and assess the impact and utility of localized plasmonic heating. Finally, future directions and applications inspired by the present state of the art are discussed.

Solid-state nanopores (ssNPs) are extremely versatile single-molecule sensors and their potential have been established in numerous biomedical applications. However, the fabrication of ssNPs remains the main bottleneck to their widespread use. Herein, we introduce a rapid and localizable ssNPs fabrication method based on feedback-controlled optical etching. We show that a focused blue laser beam irreversibly etches silicon nitride (SiNx) membranes in solution. Furthermore, photoluminescence (PL) emitted from the SiNx is used to monitor the etching process in real-time, hence permitting rate adjustment. Transmission electron microscopy (TEM) images of the etched area reveal an inverted Gaussian thickness profile, corresponding to the intensity point spread function of the laser beam. Continued laser exposure leads to the opening of a nanopore, which can be controlled to reproducibly fabricate nanopores of different sizes. The optically-formed ssNPs exhibit electrical noise on par with TEM-drilled pores, and translocate DNA and proteins readily. Notably, due to the localized thinning, the laser-drilled ssNPs exhibit highly suppressed background PL and improved spatial resolution. Given the total control over the nanopore position, this easily implemented method is ideally suited for electro-optical sensing and opens up the possibility of fabricating large nanopore arrays in situ.

Herein, we introduce synchronous, real-time, electro-optical monitoring of nanopore formation by DB. Using the same principle as sub-diffraction microscopy, our nanopore localization platform based on wide-field microscopy and calcium indicators provides nanoscale sensitivity. This enables us to establish critical limitations of the fabrication process and improve its reliability. In particular, we find that under certain conditions, multiple nanopores may form and that nanopores may preferentially localize at the membrane junction, either of which potentially render nanopore sensing ineffective. As the breakdown parameters of silicon materials are highly manufacturer-specific, we anticipate that our visualization platform will enable users to easily optimize DB fabrication according to specific needs. Furthermore, our technique furthers the applicability of DB to more complicated architectures, such as membranes with selectively thinned regions and plasmonic nanowells.

The ability to quickly and reliably fabricate nanoscale pore arrays in ultrathin membranes such as silicon nitride (Si x N) is extremely important for the growing field of nanopore biosensing. Laser-based etching of thin Si x N membranes immersed in aqueous solutions has recently been demonstrated as a method to produce stable functional pores. Herein, the principal mechanism governing material etching and pore formation using light is investigated. It is found that the process is extremely sensitive to the relative content of Si over N atoms in the amorphous membrane, produced by chemical vapor deposition. Commonly, Si x N membranes are made to be Si-rich to increase their mechanical stability, which substantially reduces the material's bandgap and increases the density of Si-dangling bonds. Hence, even minimal batchto-batch variation may lead to remarkably different etch rates. It is shown that higher Si content results in orders of magnitude faster etching rates. This rate is further accelerated in an alkaline environment allowing on-demand controlled nanopore formation in about 10 s time even at low laser radiation intensities. These results highlight that photoactivation of the Si x N by the incident beam is critical to the chemical etching process and can be used to readily produce nanopore arrays at any specific location.

Solid-state nanopore sensing of ultralong genomic DNA molecules has remained challenging, as the DNA must be controllably delivered by its leading end for efficient entry into the nanopore. Herein, we introduce a nanopore sensor device designed for electro-optical detection and sorting of ultralong (300+ kilobase pair) genomic DNA. The fluidic device, fabricated in-silicon and anodically bonded to glass, uses pressure-induced flow and an embedded pillar array for controllable DNA stretching and delivery. Extremely low concentrations (50 fM) and sample volumes (∼1 μL) of DNA can be processed. The low height profile of the device permits high numerical aperture, high magnification imaging of DNA molecules, which remain in focus over extended distances. We demonstrate selective DNA sorting based on sequence-specific nick translation labeling and imaging at high camera frame rates. Nanopores are fabricated directly in the assembled device by laser etching. We show that uncoiling and stretching of the ultralong DNA molecules permits efficient nanopore capture and threading, which is simultaneously and synchronously imaged and electrically measured. Furthermore, our technique provides key insights into the translocation behavior of ultralong DNA and promotes the development of all-in-one micro/nanofluidic platforms for nanopore sensing of biomolecules.