Hyperchromatic structural color for perceptually enhanced sensing by the naked eye

Abstract

Colorimetric sensors offer the prospect for on-demand sensing diagnostics in simple and low-cost form factors, enabling rapid spatiotemporal inspection by digital cameras or the naked eye. However, realizing strong dynamic color variations in response to small changes in sample properties has remained a considerable challenge, which is often pursued through the use of highly responsive materials under broadband illumination. In this work, we demonstrate a general colorimetric sensing technique that overcomes the performance limitations of existing chromatic and luminance-based sensing techniques. Our approach combines structural color optical filters as sensing elements alongside a multichromatic laser illuminant. We experimentally demonstrate our approach in the context of label-free biosensing and achieve ultrasensitive and perceptually enhanced chromatic color changes in response to refractive index changes and small molecule surface attachment. Using structurally enabled chromaticity variations, the human eye is able to resolve ∼0.1-nm spectral shifts with low-quality factor (e.g., Q ∼ 15) structural filters. This enables spatially resolved biosensing in large area (approximately centimeters squared) lithography-free sensing films with a naked eye limit of detection of ∼3 pg/mm2, lower than industry standard sensors based on surface plasmon resonance that require spectral or angular interrogation. This work highlights the key roles played by both the choice of illuminant and design of structural color filter, and it offers a promising pathway for colorimetric devices to meet the strong demand for high-performance, rapid, and portable (or point-of-care) diagnostic sensors in applications spanning from biomedicine to environmental/structural monitoring.

Printed Nanochain‐Based Colorimetric Assay for Quantitative Virus Detection

“…While the concentration of silica nanoparticles reduces to 0.001 mg mL À1 ,f ewer silica nanoparticles bind to the nanochains showing as light shift in the visible light range.T o evaluate the color transduction sensitivity for detecting nanoparticles,w ec alculate the perceived color difference (DE2000) of each nanochain after binding silica nanoparticles,according to the International Commission on Illumination (CIE) 2000 standardized color differencing formula (Figure 2f). [27] Ther esult shows that the nanochain with size of 300 nm exhibits the maximum sensitivity of color transduction after detecting two concentrations of silica nanoparticles,w hose color changes from magenta to green and blue.Furthermore,wealso calculate chromaticity trajectories of nanochains in response to different concentrations of silica nanoparticles,a ss hown in Figure S9. This method allows for visualizable detection of nanoparticles at the ng mL À1 range, which is commensurable with the detection limit of viral particles.…”

“…Compared with the baseline-like response to sample of the normal subject, the image intensity of nanochains linearly increases after incubating the samples from patients.C orresponding optical images of each binding event are shown in Figure 4c.S trikingly,t he color transition of nanochains enhances the green and blue intensity while simultaneously decreases the red intensity,which is easy to be discriminated by human vision. [27] Furthermore,w ed emonstrate the capacity of the nanochain assay for real-time monitoring the virus load in practical field. Figure 4d shows that the near-field enhancement of nanochains is highly dependent on the virus load.…”

Roadmap on Universal Photonic Biosensors for Real-Time Detection of Emerging Pathogens

“…These requirements increase the photonic sensor systems complexity and cost, often making them prohibitive for point-of-care bio-sensing applications. Some of these challenges can be overcome either in the interferometric photonic biosensors engineered to operate in the intensity readout mode or by using the diffractive-type biosensors (Figure 2f) that measure the reflected intensity changes at fixed wavelengths and angles [73][74][75][76][77][78]. The diffractive sensors illustrated in Figure 2f are 2-dimensional PhC stuctures [54].…”

Fano Resonant Optical coatings platform for Full Gamut and High Purity Structural Colors

“…Several structural coloring schemes have been previously introduced including multilayer lms 5 , thin lm nanocavities 6 , plasmonic nanostructures 1 , dielectric nanostructures 7 , and photonic crystals 8 with applications in decoration 9 , colorimetric sensing 10 , data storage 11 , anticounterfeiting 12 , display technologies 13 , colorful photovoltaic cells 14 , among others 15 . An ideal structural coloring platform should span a wide color gamut, producing colors with high and controllable purity-how monochromatic or pure the color is-and brightness -the relative intensity of the re ected color-and allowing control over the colors' angle dependence.…”