Research ArticleAPPLIED SCIENCES AND ENGINEERING

An optical authentication system based on imaging of excitation-selected lanthanide luminescence

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Science Advances  26 Jan 2018:
Vol. 4, no. 1, e1701384
DOI: 10.1126/sciadv.1701384
  • Fig. 1 PUFs made from lanthanide(III)-doped zeolites in polymer thin films.

    PUFs are random patterns, made from three different optically active taggants immobilized in a polymer thin film on a substrate and imaged using 30 pixels × 30 pixels. (A) The pattern can be read by resolving two, four, or seven optical responses. (B) The maximum encoding capacity of the pattern scales with the number of possible responses and the number of pixels read. (C) A cartoon representation of the same pattern read using two (binary), four (RGB+K), and seven (RGB-CMYK) responses. (D) Maximum encoding capacity as a function of the number of pixels used. (E) A random pattern made in a stochastic process by casting a solution of lanthanide-doped LTA zeolites and a polymer matrix onto a glass substrate (zeolite image from http://eng.thesaurus.rusnano.com/wiki/article1965).

  • Fig. 2 Light emission and absorption are equal when it comes to resolving random patterns of lanthanide(III)-doped zeolites.

    (A and B) The emission (A) and the excitation (B) spectra resulting from lanthanide centered emission from zeolites doped with Eu3+ (red), Tb3+ (green), and Dy3+ (blue) ions. Both emission and excitation information can be used to resolve the binary optical response (taggant is absent or present in a pixel) from a random pattern of doped zeolites in a polymer film into four channels (RGB+K).

  • Fig. 3 Emission-resolved images of zeolites doped with europium(III), terbium(III), and dysprosium(III) ions.

    (A) Emission spectra of Eu3+-, Tb3+-, and Dy3+-doped zeolites recorded upon 465-, 488-, or 450-nm excitation, respectively, from a single pixel with the CCD-based spectrometer system using 6.4- to 7.2-μW excitation power and 20-s integration time. (B) The corresponding confocal fluorescence image of Eu3+-, Tb3+-, and Dy3+-doped zeolites (10 μm × 10 μm, 50 pixels × 50 pixels, and 1- to 2-s integration time). Intensities in Tb3+ and Dy3+ images are multiplied by the factor indicated.

  • Fig. 4 Comparing emission- and excitation-resolved images of zeolites doped with europium(III), terbium(III), and dysprosium(III) ions.

    The three excitation wavelengths (R, 465 nm; G, 488 nm; and B, 450 nm) were first used separately and then simultaneously (R + G + B) to identify each taggant. (A) Emission-resolved images of a mixture of Eu3+-, Tb3+-, and Dy3+-doped zeolites (30 μm × 30 μm, 60 pixels × 60 pixels, 1-s integration time per pixel, and 6.4- to 7.2-μW excitation power). (B) Excitation-resolved APD-based intensity images (20-ms integration time per pixel and 0.5- to 0.6-μW excitation power) of the same region.

  • Fig. 5 Converting the read physical key into a digital key using either four or seven responses.

    The digitization process of excitation-selected (R, 465; G, 488; and B, 450 nm) images of one physical key made from a mixture of Eu3+-, Tb3+-, and Dy3+-doped zeolites in PVA (30 μm × 30 μm, 60 pixels × 60 pixels, and 20-ms integration time). (A) Noise-reduced images. (B) Digitized images in the RGB-CMYK scheme. (C) The digital key formed using the RGB+K scheme without colocalization and the RGB-CMYK scheme with colocalization. In the digital key, the colors correspond to Eu3+ (R = [100]), Tb3+ (G = [010]), Dy3+ (B = [001]), Tb3+ and Dy3+ (C = [011]), Eu3+ + Tb3+ (Y = [110]), Eu3+ + Dy3+ (M = [101]), and empty (K = [000]).

  • Fig. 6 An optical authentication system based on imaging of excitation-selected lanthanide luminescence used as an anticounterfeiting system.

    A product is authenticated using a physical key and readers at critical points in the supply chain. The physical key is read, digitized (second to fourth read) (B to D), and matched to the digital key (first read) (A) that was stored in the cloud by the manufacturer. Counterfeit products can enter at all points in the supply chain but will be eliminated by trusted retailers (green arrow). Counterfeits may be introduced directly to the end user (red arrow), who then must authenticate the product using a personal reader [fifth read (E) or random pattern (F)] or consult a trusted retailer.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/1/e1701384/DC1

    Validation of the physical key

    Excitation-selected imaging

    The chosen physical key

    Reading

    Digitization

    Encoding capacity

    Authentication

    Data management

    fig. S1. Cartoon of the optical setup.

    fig. S2. Absorption spectra.

    fig. S3. Emission spectra measured with a confocal microscope and a CCD-based spectrometer.

    fig. S4. Detailed emission spectra of Dy3+-doped zeolites.

    fig. S5. Spectrally resolved excitation-selected images measured with CCD for Dy3+-doped zeolite.

    fig. S6. Spectrally resolved excitation-selected images measured with CCD for Eu3+-doped zeolite.

    fig. S7. Spectrally resolved excitation-selected images measured with CCD for Tb3+-doped zeolite.

    fig. S8. CCD images of a mixture of Dy3+-, Eu3+-, and Tb3+-doped zeolites.

    fig. S9. Confocal luminescence images of a mixture of Eu3+-, Tb3+-, and Dy3+-doped zeolites using a CCD detector.

    fig. S10. Transmission electron microscopy image of Tb3+-doped zeolite.

    fig. S11. Confocal luminescence images of a mixture of Eu3+-, Tb3+-, and Dy3+-doped zeolites using an APD detector.

    fig. S12. Emission spectra measured with a confocal microscope and a CCD-based spectrometer (using SP3 filter in the emission path).

    fig. S13. Emission spectra in logarithmic scale (same data as in fig. S12), measured with a confocal microscope and a CCD-based spectrometer (using SP3 filter in the emission path).

    fig. S14. Cross-talk characterization.

    fig. S15. Detailed explanation of the digitization process with key M3Z2A as example.

    fig. S16. Confocal luminescence images of a mixture of Eu3+-, Tb3+-, and Dy3+-doped zeolites.

    fig. S17. Confocal luminescence images of a mixture of Eu3+-, Tb3+-, and Dy3+-doped zeolites.

    fig. S18. Confocal luminescence images of a mixture of Eu3+- and Tb3+-doped zeolites.

    fig. S19. Confocal luminescence images of a mixture of Eu3+- and Tb3+-doped zeolites.

    fig. S20. RGB images of zeolites doped with Eu3+, Tb3+, Dy3+, and nothing.

    fig. S21. RGB images of co-stained zeolites.

    fig. S22. The influence of multicolor, taggant size, image resolution, and taggant density on encoding capacity.

    fig. S23. Illustration of model keys (12- × 12-pixel big squares) for different variables when changing different variables.

    fig. S24. Defining an acceptance threshold from criteria 1 (checking all the pixels).

    fig. S25. Criteria 2 analysis.

    fig. S26. Authentication protocol using verification according to criteria 1 and criteria 2.

    fig. S27. Demonstration on how the verification criteria 2 works.

    fig. S28. Performance of the reader according to criteria 2.

    fig. S29. Verification figures from key M3Z2A according to criteria 2.

    fig. S30. Epi-illumination bright-field images of anticounterfeiting tags.

    fig. S31. Photostability of Eu@LTA and Tb@LTA compared to fluorescein.

    table S1. Matrix of binary combinations of Eu3+, Tb3+, and Dy3+ for zeolite loading.

    table S2. Cross-talk from the spectra in fig. S12 without background subtraction.

    table S3. Cross-talk from the spectra in fig. S12 with background subtraction.

    table S4. Cross-talk matrix derived from total intensities of images in fig. S14 without background subtraction.

    table S5. Cross-talk matrix derived from total intensities of images in fig. S14 with background subtraction.

    table S6. Description of two possible reader configurations used to digitize the physical keys.

    table S7. Encoding capacity of all the measured keys and of ideal keys with the same physical zeolite size, same scan resolution, higher scan size, and nominal zeolite density.

    table S8. Probability of a random key code guessing any database code when using criteria 1.

    table S9. Criteria 1 and 2 performance with sparsely populated keys.

    table S10. Summary of the performance of authenticity of criteria 1 and 2 in fig. S26.

    table S11. Performance of the reader assessed with match criteria 2.

    table S12. Strength of the key upon variation of digitization parameters.

    table S13. File sizes of two different types of images as an example of typical file size.

  • Supplementary Materials

    This PDF file includes:

    • Validation of the physical key
    • Excitation-selected imaging
    • The chosen physical key
    • Reading
    • Digitization
    • Encoding capacity
    • Authentication
    • Data management
    • fig. S1. Cartoon of the optical setup.
    • fig. S2. Absorption spectra.
    • fig. S3. Emission spectra measured with a confocal microscope and a CCD-based spectrometer.
    • fig. S4. Detailed emission spectra of Dy3+-doped zeolites.
    • fig. S5. Spectrally resolved excitation-selected images measured with CCD for Dy3+-doped zeolite.
    • fig. S6. Spectrally resolved excitation-selected images measured with CCD for Eu3+-doped zeolite.
    • fig. S7. Spectrally resolved excitation-selected images measured with CCD for Tb3+-doped zeolite.
    • fig. S8. CCD images of a mixture of Dy3+-, Eu3+-, and Tb3+-doped zeolites.
    • fig. S9. Confocal luminescence images of a mixture of Eu3+-, TB3+-, and Dy3+-doped zeolites using a CCD detector.
    • fig. S10. Transmission electron microscopy image of Tb3+-doped zeolite.
    • fig. S11. Confocal luminescence images of a mixture of Eu3+-, TB3+-, and Dy3+-doped zeolites using an APD detector.
    • fig. S12. Emission spectra measured with a confocal microscope and a CCD-based spectrometer (using SP3 filter in the emission path).
    • fig. S13. Emission spectra in logarithmic scale (same data as in fig. S12), measured with a confocal microscope and a CCD-based spectrometer (using SP3 filter in the emission path).
    • fig. S14. Cross-talk characterization.
    • fig. S15. Detailed explanation of the digitization process with key M3Z2A as example.
    • fig. S16. Confocal luminescence images of a mixture of Eu3+-, Tb3+-, and Dy3+-doped zeolites.
    • fig. S17. Confocal luminescence images of a mixture of Eu3+-, Tb3+-, and Dy3+-doped zeolites.
    • fig. S18. Confocal luminescence images of a mixture of Eu3+- and Tb3+-doped zeolites.
    • fig. S19. Confocal luminescence images of a mixture of Eu3+- and Tb3+-doped zeolites.
    • fig. S20. RGB image of zeolites doped with EU3+, TB3+, Dy3+, and nothing.
    • fig. S21. RGB images of co-stained zeolites.
    • fig. S22. The influence of multicolor, taggant size, image resolution, and taggant density on encoding capacity.
    • fig. S23. Illustration of model keys (12- × 12-pixel big squares) for different variables when changing different variables.
    • fig. S24. Defining an acceptance threshold from criteria 1 (checking all the pixels).
    • fig. S25. Criteria 2 analysis.
    • fig. S26. Authentication protocol using verification according to criteria 1 and criteria 2.
    • fig. S27. Demonstration on how the verification criteria 2 works.
    • fig. S28. Performance of the reader according to criteria 2.
    • fig. S29. Verification figures from key M3Z2A according to criteria 2.
    • fig. S30. Epi-illumination bright-field images of anticounterfeiting tags.
    • fig. S31. Photostability of Eu@LTA and Tb@LTA compared to fluorescein.
    • table S1. Matrix of binary combinations of Eu3+, Tb3+, and Dy3+ for zeolite loading.
    • table S2. Cross-talk from the spectra in fig. S12 without background subtraction.
    • table S3. Cross-talk from the spectra in fig. S12 with background subtraction.
    • table S4. Cross-talk matrix derived from total intensities of images in fig. S14 without background subtraction.
    • table S5. Cross-talk matrix derived from total intensities of images in fig. S14 with background subtraction.
    • table S6. Description of two possible reader configurations used to digitize the physical keys.
    • table S7. Encoding capacity of all the measured keys and of ideal keys with the same physical zeolite size, same scan resolution, higher scan size, and nominal zeolite density.
    • table S8. Probability of a random key code guessing any database code when using criteria 1.
    • table S9. Criteria 1 and 2 performance with sparsely populated keys.
    • table S10. Summary of the performance of authenticity of criteria 1 and 2 in fig. S26.
    • table S11. Performance of the reader assessed with match criteria 2.
    • table S12. Strength of the key upon variation of digitization parameters.
    • table S13. File sizes of two different types of images as an example of typical file size.

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