Ultrasensitive Molecular Detection at Subpicomolar Concentrations by the Diffraction Pattern Imaging with Plasmonic Metasurfaces and Convex Holographic Gratings

Abstract

Compact and cost‐effective optical devices for highly sensitive detection of trace molecules are significant in many applications, including healthcare, pollutant monitoring and explosive detection. Nanophotonic metasurface‐based sensors have been intensively attracting attentions for molecular detection. However, conventional methods often involve spectroscopic characterizations that require bulky, expensive and sophisticated spectrometers. Here, a novel ultrasensitive sensor of plasmonic metasurfaces is designed and fabricated for the detection of trace molecules. The sensor features a convex holographic grating, of which the first‐order diffraction pattern of a disposable metasurface is recorded by a monochrome camera.The diffraction pattern changes with the molecules attached to the metasurface, realizing label‐free and spectrometer‐free molecular detection by imaging and analyzing of the diffraction pattern. By integrating the sensor with a microfluidic setup, the quantitative characterization of rabbit anti‐human Immunoglobulin G (IgG) and human IgG biomolecular interactions is demonstrated with an excellent limit of detection (LOD) of 0.6 p m . Moreover, both the metasurface and holographic grating are obtained through vacuum‐free solution‐processed fabrications, minimizing the manufacturing cost of the sensor. A prototype of the imaging‐based sensor, consisting of a white light‐emitting diode (LED) and a consumer‐level imaging sensor is achieved to demonstrate the potential for on‐site detection.

Refractometric Imaging and Biodetection Empowered by Nanophotonics

“…Recently, a further simplified system configuration was demonstrated by the convex holographic grating consisting of Cu nanograting attached to a spherical lens. [ 176 ] The calibrated sensitivity reaches ≈4600 pixel RIU −1 using this facile imaging approach and a real‐time assay of IgG/anti‐IgG suggests a LOD down to 0.1 ng mL −1 (Figure 13f,g).…”

“…Inset: Zoomed-in view of g) at the linear regime with a linear fit. Reproduced with permission [176]. Copyright 2022, Wiley-VCH.…”

Trends of Biosensing: Plasmonics through Miniaturization and Quantum Sensing

“…SARS-CoV-2 was detected with high sensitivity and specificity, which enabled the distinction of the pandemic virus from the influenza virus (panel iii) [30] . Most grating-based couplers use the phase method [31] or the combination of the sensing and imaging capabilities of guided-mode resonance devices, in which the grated substrate is embedded into a microfluidic chip.…”

Cost‐Effective Nanophotonic Metasurfaces with Spatially Gradient Structures for Ultrasensitive Imaging‐Based Refractometric Sensing

“…For example, an imaging-based spectrometer-free refractometric detection for real-time onsite biomolecular sensing with more compactness and higher sensitivity can be achieved by converting the spectra of nanophotonic metasurfaces into intensity images. [26][27][28] The key challenges in imaging-based refractometric sensing using nanophotonic metasurfaces [29][30][31][32] are imaging-based sensing scheme miniaturization, and metasurface fabrication cost reduction. To address these challenges, metasurfaces fabricated through a novel cost-efficient process for ultrasensitive imaging-based refractive index sensing are in need.…”