Large-Area Virus Coated Ultrathin Colorimetric Sensors with a Highly Lossy Resonant Promoter for Enhanced Chromaticity

Abstract

Acclimatable colors in response to environmental stimuli, which are naturally endowed with some living things, can provide an opportunity for humans to recognize hazardous substances without taking empirical risks. Despite efforts to create artificial responsive colors, realistic applications in everyday life require an immediate/distinct colorimetric realization with wide chromatic selectivity. A dynamically responsive virus (M-13 phage)-based changeable coloring strategy is presented with a highly lossy resonant promoter (HLRP). An ultrathin M-13 phage layer for rapid response to external stimuli displays colorimetric behavior, even in its subtle swelling with strong resonances on HLRP, which is modeled using the complex effective refractive index. Optimal designs of HLRP for several material combinations allow selective chromatic responsivity from the corresponding wide color palette without modification of the dynamic responsive layer. As a practical demonstration, the spatially designed colorimetric indicator, which is insensitive/sensitive to external stimuli, provides an intuitive perception of environmental changes with hidden/revealed patterns. Furthermore, the proposed colorimetric sensor is tested by exposure to various volatile organic chemicals and endocrine disrupting chemicals for versatile detectability, and is fabricated in a wafer-scale sample for large-area scalability.

Keywords: bacteriophages; colorimetric sensors; endocrine disrupting chemicals; thin‐film coloration; volatile organic compounds.

Figure 1

a) Schematic illustration of colorimetric sensor with corresponding Ge thickness and relative humidity with M‐13 phage coating. b) SEM image showing phage‐coated porous Ge layer of cross‐sectional (left) and top view SEM image (right). Scale bar is 100 nm. c) Schematic showing highly lossy resonant promoter (HLRP) for resonance enhancement. d) Color images of colorimetric sensor corresponding to different humidity levels. e) Absorption intensity distributions of phage‐coated HLRP, Si, and Au, respectively. f) AFM images and thickness level profiling showing bundle size change by humidity conditions. Scale bar is 5 µm. g) Schematic illustration of resonant enhanced color reflection mechanism with phage layer swelling and reflectance spectra showing enhanced absorption and dip shift. h) Schematic of spin‐coating method and sample images onto 2‐inch wafer before (top) and after (bottom) phage spin‐coating. Scale bar is 1 cm.

Figure 2

a) Contour map of the calculated reflectance versus complex refractive index at a specific wavelength (λ _c = 500 nm), along with a schematic of the composition of each separated HLRP layer. b) Color saturation of each reflectance spectrum having different dip reflectances (R _dip) (λ _dip = 500 nm). c) Reflectance contour with dynamic change of coating layer on the HLRP of Au/Ge (P _r 75%, t _Ge = 60 nm). d) RGB color representations and corresponding color differences (ΔE) with different coating layers on 2D surface of complex refractive index. e) Complex refractive index coordinate, which contains resonant area for various materials. As P _r increases, the complex refractive index of HLRP converges to the resonant area. f) Chromaticity plots for sRGB gamut (white line) on CIE coordinates, indicating the colors of phage‐coated HLRP for various material and thickness combinations. g) Color palette of several material and thickness combinations with dynamic change (t _coat 60–200 nm).

Figure 3

a) Schematic illustration showing colorimetric sensing optimization process according to phage dilution and absorbing layer (P _r‐Ge) thickness with reflectance spectra measurements. b) Degree of hue angle change of various conditions from (a). c) Schematic illustration of colorimetric sensor display with visualization process insensitive/sensitive color difference. d) Regional design of insensitive/sensitive area with different chromatic response (top); color difference (ΔE) of insensitive/sensitive area (bottom). e) Color images of colorimetric sensor display in different states (before/after phage coating, and humidity indicating state, respectively). Scale bar is 1 cm. f) Reproducibility test result and g) response/recovery time measurement result by repeated exposure to RH 20% and 70%.

Figure 4

a) Schematic illustration of genetically engineered M‐13 phage and engineered sequences (top). Schematic of multicolorimetric sensor array (MCSA) with four engineered phage coating layer (WT, 3A, 4E, and 3W) on HLRP (bottom) under volatile organic compounds (VOCs) (acetone, isopropyl alcohol, diethyl ether, and benzene) and endocrine disrupting chemicals (EDCs) (diisobutyl phthalate (DiBP) and di‐n‐butyl phthalate (DnBP)) b) Fingerprint patterns obtained by color difference of MCSA with varying chemical substance and concentration change. c) Color palette based on ΔRGB intensity with varying chemical substance and concentration change. Hierarchical cluster analysis (HCA) of d) VOCs and e) EDCs/benzene in accordance with different concentrations.