Implantable QR code subcutaneous microchip using photoacoustic and ultrasound microscopy for secure and convenient individual identification and authentication

Abstract

Individual identification and authentication techniques are merged into many aspects of human life with various applications, including access control, payment or banking transfer, and healthcare. Yet conventional identification and authentication methods such as passwords, biometrics, tokens, and smart cards suffer from inconvenience and/or insecurity. Here, inspired by quick response (QR) code and implantable microdevices, implantable and minimally-invasive QR code subcutaneous microchips (QRC-SMs) are proposed to be an effective approach to carry useful and private information, thus enabling individual identification and authentication. Two types of QRC-SMs, QRC-SMs with "hole" and "flat" elements and QRC-SMs with "titanium-coated" and "non-coated" elements, are designed and fabricated to store personal information. Corresponding ultrasound microscopy and photoacoustic microscopy are used for imaging the QR code pattern underneath skin, and open-source artificial intelligence algorithm is applied for QR code detection and recognition. Ex vivo experiments under tissue and in vivo experiments with QRC-SMs implanted in live mice have been performed, demonstrating successful information retrieval from implanted QRC-SMs. QRC-SMs are hidden subcutaneously and invisible to the eyes. They cannot be forgotten, misplaced or lost, and can always be ready for timely medical identification, access control, and payment or banking transfer. Hence, QRC-SMs provide promising routes towards private, secure, and convenient individual identification and authentication.

Keywords: Acoustic-resolution photoacoustic microscopy; Implantable devices; Individual identification and authentication; Quick response code; Ultrasound microscopy.

Fig. 1

Working principles of QRC-SM. A) QRC-SM with “hole” and “flat” elements coupled with USM for identification and authentication. B) QRC-SM with “Ti-coated” and “non-coated” elements coupled with AR-PAM for identification and authentication. Note that QRC-SMs are hidden subcutaneously and invisible to the eyes. UST, ultrasound transducer; US, ultrasound; PA, photoacoustic.

Fig. 2

Design, fabrication, and initial characterization of QRC-SM. A) Conventional QR code image with “black” and “white” elements. B) to D) QRC-SM with “hole” or “flat” elements for USM: (B) 3D schematic (top view), (C) 3D schematic (tilted view), and (D) Zoomed-in view from the red box in (C) showing the feature size of the QRC-SM and the “hole” or “flat” elements. E) to G) QRC-SM with “Ti-coated” and “non-coated” elements for AR-PAM: (E) 3D schematic (top view), (F) 3D schematic (tilted view), and (G) Zoomed-in view from the red box in (F) showing the feature size of the QRC-SM and the “Ti-coated” or “non-coated” elements. H) Measured depth resolving capability of USM. I) Resolution calibration of USM. J) Resolution calibration of AR-PAM. K) Front view of the two types of QRC-SMs laid side by side on a finger, with the one with “Ti-coated” and “non-coated” elements on the left, and the one with “hole” and “flat” elements on the right. L) Side view of the two types of QRC-SMs on a finger.

Fig. 3

Ex vivo imaging of a QRC-SM with “hole” and “flat” elements. A) Illustration of the 3D structure of a QRC-SM with “hole” and “flat” elements (Pattern No. 3), and the color map of the depth profile measured by a step profiler. B) USM image of a bare QRC-SM (Pattern No. 3). C) B-mode image corresponding to the dashed blue line in (B). D) USM image of a QRC-SM (Pattern No. 3) covered by a 2.3-mm-thick layer of chicken breast tissue. Scale bars, 500 µm.

Fig. 4

In vivo experiments of a QRC-SM with “hole” and “flat” elements. A) Photograph showing the process of implanting a QRC-SM into a nude mouse. B) 3D schematic of implanting a QRC-SM underneath mouse skin. C) A nude mouse with an implanted QRC-SM such that the QR code patterns are hidden underneath the mouse skin. D) USM image of the QRC-SM implanted into the nude mouse. E) Workflow of the CVQR algorithm for retrieving the information from depth-encoded image of a QRC-SM. F) Depth-encoded image as input. G) Output after CNN-based detection and super resolution. H) Output after binarization. I) Final output. Scale bar, 500 µm.

Fig. 5

Ex vivo imaging of a QRC-SM with “Ti-coated” and “non-coated” elements. A) AR-PAM image of a bare QRC-SM (Pattern No. 1). B) B-mode image corresponding to the dashed red line in (A). C) AR-PAM image of a QRC-SM (Pattern No. 1) covered by a 2.3-mm-thick layer of chicken breast tissue. Scale bars, 500 µm.

Fig. 6

In vivo experiments of a QRC-SM with “Ti-coated” and “non-coated” elements. A) Photograph showing the process of implanting a QRC-SM into a nude mouse. B) 3D schematic of implanting a QRC-SM underneath mouse skin. C) A nude mouse with an implanted QRC-SM such that the QR code pattern is hidden under the mouse skin. D) AR-PAM image of the QRC-SM implanted into the nude mouse. E) Workflow of the CVQR algorithm for retrieving the information from MAP image of a QRC-SM. F) MAP image as input. G) Output after CNN-based detection and super resolution. H) Output after binarization. I) Final output. J) AR-PAM image of the same QRC-SM implanted in the nude mouse imaged using laser wavelength at 670 nm. K) AR-PAM image with vessels enhanced based on (J). Scale bar for (D, J and K), 500 µm.

Fig. 7

Representative H&E-stained images and inflammation responses of contacting tissues (with the QRC-SM implants) after the implantation of QRC-SMs. A) to C): Representative H&E-stained images of tissue slices on day 0 (negative control), day 2, and day 15 after the implantation of QRC-SMs with “hole” and “flat” elements. D) to F): Representative H&E-stained images tissue slices on day 0 (negative control), day 2, and day 15 after the implantation of QRC-SMs with “Ti-coated” and “non-coated” elements. Black arrows: neutrophils; Scale bars, 50 µm. G) Inflammatory responses of tissue slices on day 0 (negative control), day 2, and day 15 after the implantation of QRC-SMs with “hole” and “flat” elements. H) Inflammatory response of tissue slices on day 0 (negative control), day 2, and day 15 after the implantation of QRC-SMs with “Ti-coated” and “non-coated” elements. The median ± the range is indicated at each time point. * *, p < 0.01 compared with day 0.