Plasmonic Pixel Biosensor Based on Grazing Angle Illumination and Computational Imaging

Surface plasmon resonance (SPR) has been adapted for analyzing biomolecular interactions in real time as a label-free technology. However, SPR instruments, which are usually bulky and expensive, require specialized optical components for exciting surface plasmons and detecting spectral signals, and the technique has yet to evolve into a more affordable and accessible analytic tool. In this paper, we demonstrate a plasmonic sensing device integrated with plasmonic pixels for exciting surface plasmons and displaying spectral information. The plasmonic pixels based on continuous nanostructured metallic thin films establish a direct relationship between nanostructure patterns and plasmon resonances in the visible and near-infrared spectrum range. Steep dispersion of Fano resonances induced by incident light from a grazing angle transduces plasmonic spectral responses into a unique two-dimensional image. Spectral information extracted from the plasmonic pixels exhibits an asymmetric Fano resonance behavior with sharp intensity peaks and the full width half maxima (FWHM) down to 10 nm. The relative brightness of the plasmonic pixels allows naked human eyes to detect the formation of a biomolecule monolayer. Most importantly, subnanometer spectral information can be extracted from the plasmonic pixel images and computed to analyze dynamics of chemical and biomolecular binding events in real time. We envision that these nanostructure plasmonic pixel biosensors can provide a compact and low-cost analytic platform to meet the emerging demands, particularly in portable, mobile, and wearable devices for label-free detection and point-of-care diagnostics.