An integrated digital microfluidic plasmonic metasurface chip biological image detection system

Abstract

The application discloses an integrated digital microfluidic plasmonic metasurface chip biological image detection system, and belongs to the field of microfluidic and metasurface biological image sensing. The system comprises a digital microfluidic chip, a plasmonic metasurface chip, a light source, a CMOS image sensor and a control circuit. The digital microfluidic chip is provided with a driving electrode array, a medium layer and a hydrophobic layer, and is used for constructing a liquid path and controlling droplets. The plasmonic metasurface chip is combined with the digital microfluidic chip to form a detection site, and is used for detecting biomolecules by using a plasmonic resonance effect. The light source is used for exciting plasmonic resonance. The CMOS image sensor is used for capturing images at the detection site. The control circuit is used for controlling electrodes of the digital microfluidic chip, and realizes construction of the liquid path and control of the droplets. The biomolecule solution to be detected can be accurately guided to the detection site of the plasmonic metasurface chip, the light source is used for exciting plasmonic resonance, and the CMOS image sensor is used for capturing images. Image intensity changes are analyzed by using image processing software, and a detection result of the biomolecules is obtained.

Description

Technical Field

[0001] This invention belongs to the field of microfluidics and metasurface biological image sensing, specifically relating to a plasmonic metasurface chip biological image detection system integrating digital microfluidics. Background Technology

[0002] Microfluidics is a system used to control and manipulate small volumes of liquids. It involves manipulating small amounts of fluid (typically 10⁻⁶ liters) within sub-millimeter channels using pressure, capillary force, and centrifugal force. -8 ~10 -12 Microfluidics is a technology for processing and transporting liquids. Compared to manual liquid handling, microfluidics can automate a series of steps, including sample transport, mixing, reaction, and detection, achieving high-throughput processing. At the same time, it can reduce the amount of samples and reagents used and increase the mixing rate between different reagents. These advantages make microfluidic systems a significant contributor to the field of bioassay.

[0003] Digital microfluidics is a technology that manipulates microfluidics based on the principle of dielectric electrowetting. More specifically, the dielectric electrowetting effect utilizes an electric field to alter the wettability of a liquid on a solid surface: when a voltage is applied to the electrodes, a potential difference is generated between two adjacent driving electrodes. The contact angle between the droplet and the surface decreases due to dielectric wetting and dielectric adhesion forces, generating a driving force pointing towards the side with the higher potential. This manifests as a controllable movement of the droplet according to the sequence of electrode energization. Compared to typical microfluidics, digital microfluidics, by digitally applying voltage to the electrodes, allows for customization of the droplet's movement path, offering greater flexibility and portability. Furthermore, digital microfluidic chips are small, finely structured, and capable of automated reactions, making them particularly suitable for many complex and intricate processes. Therefore, digital microfluidic chips are widely used in various biochemical reactions and detection applications.

[0004] In recent years, surface plasmon resonance (SPR) technology has shown broad application prospects in point-of-care biomolecular detection, attracting significant attention from researchers. Compared to traditional biomarker detection methods, plasmon-based metasurface biosensing enables label-free detection of biomolecules and offers non-destructive testing capabilities, meaning it is less restricted by operational conditions. As an improved version of plasmon-based metasurface sensing, image-based metasurface sensing technology can achieve multiplexing and simultaneously acquire multidimensional data, providing more detailed information about the analytes. Furthermore, image-based metasurface sensing technology boasts extremely high detection sensitivity, making it easy to observe interactions between biomolecules. Therefore, image-based biosensing using metasurface chips is more suitable for multi-index, high-volume point-of-care detection.

[0005] In image-sensing-based biosensing using metasurface chips, samples and biological reagents need to be added. Manual addition makes it difficult to precisely control the amount of reagents and samples, resulting in waste; at the same time, manual addition is prone to sample and reagent contamination, thus affecting the detection results. Traditional microfluidics require the design of liquid paths for each biosensor individually, which is not suitable for multi-sensor, high-volume point-of-care testing, and it does not allow for temporary changes in detection indicators or modifications to the detection process, making it unsuitable for using metasurface chips in point-of-care testing. Summary of the Invention

[0006] The purpose of this invention is to address the aforementioned problems in the prior art by providing a plasmonic metasurface chip-based bio-image detection system integrating digital microfluidics. This system combines the automation and programmability of digital microfluidics with the label-free detection capabilities of plasmonic metasurface chips, and utilizes a portable metal-oxide-semiconductor (CMOS) image sensor to achieve miniaturized, high-throughput, and multi-index biomolecule detection.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution.

[0008] A bio-image detection system for a plasmonic metasurface chip with integrated digital microfluidics includes a digital microfluidic chip, a plasmonic metasurface chip, a light source, and a CMOS image sensor.

[0009] The digital microfluidic chip adopts a dual-plate structure, consisting of a lower plate and an upper plate, with an operating space between the lower and upper plates for accommodating droplets. The droplets to be processed and detected are located between the parallel and spaced upper and lower plates. The lower plate is provided with a driving electrode array, a dielectric layer covering the driving electrode array, and a first hydrophobic layer covering the dielectric layer from bottom to top. The lower surface of the upper plate is provided with a second hydrophobic layer coated on the top plate. The driving electrode array is connected to a control circuit, which flexibly constructs the liquid path required for detection.

[0010] The lower electrode of the plasmonic metasurface chip and the digital microfluidic chip are combined. The plasmonic metasurface chip forms a detection site on a single electrode for the detection of biomolecules. The biomolecule solution to be tested can be controlled to move in and out through the digital microfluidic chip.

[0011] The optical path, consisting of the light source and the CMOS image sensor, passes through the detection site. The system captures the image at the detection site using the CMOS image sensor, and the image is used for subsequent analysis.

[0012] Furthermore, the operating space between the upper and lower electrode plates is encapsulated with a filling medium for droplet movement.

[0013] Furthermore, the filling medium can be silicone oil or air.

[0014] Furthermore, the digital microfluidic chip can accommodate more droplets and construct more complex liquid channels by increasing the number of electrodes.

[0015] Furthermore, the digital microfluidic chip has programmable liquid circuitry, enabling high-throughput or multi-index biomolecular detection at the same time.

[0016] Furthermore, this scheme is an imaging system based on a plasmonic metasurface chip design, which uses a CMOS image sensor for imaging.

[0017] Furthermore, when label-free biomolecules combine with the metal nanostructures on the metasurface chip, plasmon resonance occurs, affecting the refractive index and causing a shift in the spectral absorption peak. Specifically, this manifests as changes in image intensity captured by the CMOS image sensor, and the detection results can be obtained through image processing software such as MATLAB.

[0018] Furthermore, the light intensity images acquired by the CMOS image sensor were processed using MATLAB to obtain the results of biomolecule detection.

[0019] Furthermore, multiple detection sites can be set on the digital microfluidic chip to achieve high-throughput multi-index detection, which requires the addition of an additional optical path module. Specifically, multiple detection sites are set on the digital microfluidic chip, each site corresponding to a plasmonic metasurface detection unit. By adding an additional optical path module, the simultaneous detection of multiple biomolecular indicators can be achieved.

[0020] Furthermore, for intensity images acquired from multiple detection sites, the region images acquired by CMOS image sensor pixel units aligned with each detection site on the overall intensity image are selected as the detection images for each detection point. These images are then processed using MATLAB programs to obtain high-throughput or multi-index detection results.

[0021] Compared with the prior art, the beneficial effects achieved by the technical solution of this invention are:

[0022] This invention organically combines digital microfluidics, nano-optics, and a portable CMOS image sensor. First, the integrated digital microfluidic chip automates the mixing, reaction, and chip cleaning of biological droplets, solving the problems of sample and reagent waste and contamination in traditional manual sample addition methods, reducing manual operation time, and simplifying procedures. Simultaneously, the digital microfluidic chip possesses a multi-electrode programmable liquid path, eliminating the cumbersome process of customizing each liquid path for high-throughput, multi-index biomolecule detection in traditional microfluidic sample addition methods, thus reducing the overall system manufacturing cost. Second, compared to other biodetection methods, the use of plasmon metasurface chips eliminates the need for labeling the target biomolecules, avoiding damage to biomolecules from labeling agents, simplifying the biomolecule reaction steps in the detection process, and reducing the overall detection time. Third, the plasmon intensity images used contain more effective information, enabling high-throughput, multi-index detection. Finally, compared to the bulky and expensive spectrometers required for traditional spectral-based plasmon detection methods, the image-based detection method uses a portable CMOS image sensor, achieving miniaturization of the overall system. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall framework of the integrated digital microfluidic plasmonic metasurface chip biological image detection system in Embodiment 1 of the present invention;

[0024] Figure 2 This is a partial structural diagram of Embodiment 1 of the present invention;

[0025] Figure 3 This is a schematic diagram of the overall system framework in Embodiment 2 of the present invention;

[0026] Figure 4 This is a partial structural diagram of Embodiment 2 of the present invention;

[0027] Figure 5 This is a schematic diagram of the overall system framework in Embodiment 3 of the present invention;

[0028] Figure 6 This is a partial structural diagram of Embodiment 3 of the present invention. Detailed Implementation

[0029] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0030] Example 1

[0031] Figure 1This is a schematic diagram of the overall framework of the integrated digital microfluidic plasmonic metasurface chip biological image detection system in a specific embodiment of the present invention. The detection part includes a light source 101, an optical path module 102, a digital microfluidic chip 103 combined with a plasmonic metasurface chip, and a CMOS image sensor 105. The control part includes a digital microfluidic chip control module 104 and a host computer 106.

[0032] In this embodiment, the digital microfluidic chip control module is connected to the host computer. The host computer transmits data to the control module to control the movement of droplets on the digital microfluidic chip and construct a detection liquid path. The CMOS image sensor is also connected to the host computer. The host computer controls the switch of the CMOS image sensor, and the CMOS image sensor transmits the acquired images to the host computer. The images are then filtered and processed by the MATLAB program in the host computer to obtain the detection results.

[0033] Figure 2 This is a partial structural diagram of the detection section of the digital microfluidic chip in this embodiment, which includes a metasurface chip. It includes a collimated light source 201, a full width at half maximum (FWHM) filter 202, an upper electrode 203, a second hydrophobic layer 204, a droplet to be tested 205, a plasmonic metasurface chip 206, a first hydrophobic layer 207, a driving electrode array 208, a dielectric layer 209, a lower electrode 210, and a CMOS image sensor 211. The broad arrows indicate the optical path, and the combination of the droplet to be tested and the plasmonic metasurface chip is called the detection site.

[0034] In this embodiment, the system requires two images to obtain the detection site results, specifically as follows: First, the plasmon metasurface chip is biofunctionalized to enable it to capture the target biomolecule; then, a digital microfluidic chip is used to move droplets of a buffer solution (such as phosphate buffered saline solution) onto the plasmon metasurface chip, and the first image is acquired as the original image; then, droplets of the same buffer solution containing the target biomolecule are moved onto the plasmon metasurface chip, allowing the target biomolecule to bind to the metasurface, and the second image is acquired as the detection image. By comparing the original image and the detection image and quantifying the differences, the detection results can be obtained qualitatively and quantitatively.

[0035] In this embodiment, the system employs transmission imaging. Specifically, the system's light source includes a collimated light source, which comprises an LED array and a collimating lens module. The light from the collimated light source passes through an FWHM filter and is transmitted downwards from above the digital microfluidic chip, through the droplet under test and the metasurface chip, and finally, a CMOS image sensor below the digital microfluidic chip acquires the transmission intensity image. The FWHM filter's function is to allow the light passing through it to excite plasmons on the metasurface chip. To ensure the transmission intensity, the digital microfluidic chip uses transparent indium tin oxide (ITO) conductive glass as the substrate material for the upper and lower electrodes, and the plasmon metasurface chip uses glass as the substrate material.

[0036] In this embodiment, the collimated light source and the CMOS image sensor are located at the same center. The light spot of the collimated light source passes through the detection point and completely covers the CMOS image sensor. The area of ​​the light spot is larger than the area of ​​the CMOS image sensor chip. While acquiring the plasmon transmission intensity image, it achieves full coverage of the CMOS photosensitive array, ensuring the quality of imaging.

[0037] Example 2

[0038] Figure 3 This is a schematic diagram of the overall framework of a plasmonic metasurface chip-based biological image detection system with integrated digital microfluidics in another specific embodiment of the present invention. The system has multiple detection points. The detection section includes a light source 301, an optical path module 302, a digital microfluidic chip 303 integrated with a plasmonic metasurface chip, an additional optical path module 305, and a CMOS image sensor 307. The control section includes a digital microfluidic chip control module 304 and a host computer 306. Unlike Embodiment 1, this embodiment has a larger transmission range, and the transmitted light needs to be focused by the additional optical path module before it can be acquired by the CMOS image sensor.

[0039] Figure 4 This is a partial structural diagram of the detection section of the digital microfluidic chip in this embodiment, which includes a metasurface chip. It includes a collimating light source 401, an FWHM filter 402, an upper electrode 403, a second hydrophobic layer 404, multiple test droplets 405, multiple plasmon metasurface chips 406, a first hydrophobic layer 407, a driving electrode array 408, a dielectric layer 409, a lower electrode 410, a focusing lens 411, and a CMOS image sensor 412. The optical path is labeled in the diagram. The combination of the test droplets and the plasmon metasurface chips is referred to as the detection site. Similar to Embodiment 1, this embodiment requires two images to obtain the detection site results.

[0040] Similar to Example 1, this embodiment employs transmission imaging. The digital microfluidic chip uses transparent indium tin oxide (ITO) conductive glass as the substrate material for both the upper and lower electrodes, and the plasmonic metasurface chip uses glass as the substrate material. The collimated light source and the CMOS image sensor are located at the same center. The difference lies in the fact that, due to the multiple detection points in this embodiment, the light source must cover all detection sites. Since large-area CMOS image sensors are expensive, an additional focusing lens is used to focus the transmitted light onto a small-area CMOS image sensor to obtain plasmonic transmission intensity maps related to multiple detection sites, thus reducing costs.

[0041] In this embodiment, the overall transmission intensity image acquired by the host computer needs to be segmented and filtered to obtain the transmission intensity image of each detection point. Pixel regions with valid detection information can be selected from the image based on the positional relationship between the optical path and the detection point. Furthermore, since the transmission intensity of the detection point is significantly different from other locations, machine learning techniques can be used to assist in the identification and judgment of the pixel region corresponding to the detection point.

[0042] Example 3

[0043] Figure 5 This is a schematic diagram of the overall framework of a plasmonic metasurface chip-based biological image detection system with integrated digital microfluidics in another specific embodiment of the present invention. The detection part includes a light source 501, an optical path module 504, a digital microfluidic chip 505 combined with a plasmonic metasurface chip, and a CMOS image sensor 502. The control part includes a digital microfluidic chip control module 503 and a host computer 506. Unlike embodiments 1 and 2, this embodiment uses reflective imaging.

[0044] Figure 6 This is a partial structural diagram of the detection section of the digital microfluidic chip in this embodiment, which includes a metasurface chip. It includes a collimating light source 602, an FWHM filter 603, an upper electrode 604, a second hydrophobic layer 605, a test droplet 606, a plasmonic metasurface chip 607, a first hydrophobic layer 608, a dielectric layer 609, a driving electrode array 610, a lower electrode 611, and a CMOS image sensor 601. The incident and reflected light paths are marked in the diagram. The combination of the test droplet and the plasmonic metasurface chip is referred to as the detection site. Similar to Embodiment 1, this embodiment requires two images to obtain the detection site results.

[0045] Since this embodiment uses reflective imaging, there is no need to select transparent materials to manufacture the digital microfluidic chip and plasmonic metasurface chip, which is slightly different from the previous embodiments. In this embodiment, the digital microfluidic chip can be manufactured using PCB technology, with electrodes made of a double-layer metal material of copper on the bottom and gold on top. The plasmonic metasurface can be obtained by further processing (such as nanoimprinting) directly on the gold on the electrodes. When fabricating the dielectric layer and hydrophobic layer of the lower electrode of the digital microfluidic chip, the metasurface part is masked to protect its biodetection characteristics; alternatively, a space can be reserved on the digital microfluidic chip to embed and combine the plasmonic metasurface chip with silicon as the substrate.

[0046] In this embodiment, the image acquired by the CMOS image sensor is a plasmon reflection intensity image. The image acquired by the CMOS image sensor should be as complete as possible. This requires strict adherence to the positional relationships between the light source, the detection site, and the CMOS image sensor. For example, the incident angle and reflection angle formed by the incident light path, the reflected light path, and the normal to the plasmon metasurface chip should be equal. The spot area of ​​the collimated light source should cover the detection site, and the area of ​​the reflected spot should also be larger than the area of ​​the CMOS image sensor chip to ensure the quality of the acquired results.

[0047] The system of this invention can precisely guide a solution of biomolecules to be detected to the detection site of a plasmonic metasurface chip, excite plasmonic resonance using a light source, and capture the image using a CMOS image sensor. By analyzing the changes in image intensity using image processing software, the detection results of the biomolecules can be obtained.

[0048] In addition, the system of the present invention also has high-throughput detection capability. By designing multiple electrodes and plasmonic metasurface regions, it can simultaneously detect a variety of biomolecules, greatly improving detection efficiency and accuracy.

[0049] The digital microfluidic chip of this invention can be a dual-plate digital microfluidic chip. The lower plate can use ITO glass as the substrate for the driving electrode, and the driving electrode array is fabricated using photolithography. The dielectric layer can be made of tetramethyl terephthalate (PTFE) and is applied to the driving electrode array to prevent short circuits between the electrodes. The first hydrophobic layer can be a polytetrafluoroethylene (PTFE) coating to increase the contact angle between the droplet and the surface, making the surface hydrophobic. The upper plate can be made of transparent ITO glass, and the lower surface is coated with a second hydrophobic layer, the material of which can be the same as the first hydrophobic layer.

[0050] Plasmonic metasurface chips can utilize gold nanopore structure arrays as the plasmonic metasurface. These arrays are fabricated on transparent silicon dioxide (SiO2) or sapphire (Al2O3) substrates using electron beam etching. Each gold nanopore structure can have a diameter of 100–200 nm, and the array period can be 300–600 nm. The plasmonic metasurface chip is then aligned and bonded to specific electrode positions on the lower plate of a digital microfluidic chip using a precision positioning device.

[0051] Light source and CMOS image sensor: An LED light source with a wavelength of 635nm is selected as the excitation source. After passing through a 10nm FWHM filter, it can excite the plasmonic metasurface chip. A high-sensitivity, high-resolution CMOS image sensor is selected, and the lens system focuses on the detection site to ensure image clarity.

[0052] During detection, a solution of the target biomolecule (such as proteins, exosomes, etc.) and various reagent solutions involved in the biological reaction can be loaded onto specific electrodes of a digital microfluidic chip. By controlling the activation of the electrodes, various reagent solutions are moved to pretreat the target biomolecule solution and biofunctionalize the plasmonic metasurface chip. The pretreated target biomolecule solution is then moved to the detection site on the plasmonic metasurface chip. A light source is activated, and an image at the detection site is captured by a CMOS image sensor. The image is processed using a MATLAB program to analyze changes in image intensity and obtain the detection results.

[0053] The biological image detection system of the present invention has the advantages of simple operation, high detection sensitivity, and strong high-throughput detection capability. It is applicable to fields such as biomedical research, clinical diagnosis, and drug screening, and provides a new technical means for the rapid and accurate detection of biomolecules.

[0054] Although the contents of this application are specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that any changes in form and detail made to this application without departing from the spirit and scope of this application as defined by the appended claims and without inventive effort are within the scope of protection of this application.

Claims

1. A plasmonic metasurface chip-based biological image detection system integrating digital microfluidics, characterized in that, This includes digital microfluidic chips, plasmonic metasurface chips, light sources, and CMOS image sensors; The digital microfluidic chip adopts a dual-plate structure, including a lower plate and an upper plate, forming an operating space between the lower and upper plates to accommodate the droplets to be tested. The droplets to be processed and detected are located between the parallel and spaced upper and lower plates. The lower plate is provided with a driving electrode array, a dielectric layer covering the driving electrode array, and a first hydrophobic layer covering the dielectric layer from bottom to top. The lower surface of the upper plate is provided with a second hydrophobic layer coated on the top plate. The driving electrode array is connected to a control circuit, which flexibly constructs the liquid path required for detection. The lower electrode of the plasmonic metasurface chip and the digital microfluidic chip are combined. The plasmonic metasurface chip forms a detection site on a single electrode for the detection of biomolecules. The digital microfluidic chip controls the movement of the biomolecule solution to be tested in and out. The light source is used to excite plasmon resonance on the plasmon metasurface chip; the CMOS image sensor is used to capture the image at the detection site; the optical path formed by the light source and the CMOS image sensor passes through the detection site, and the system images the image in the CMOS image sensor, which is then used for subsequent analysis.

2. The integrated digital microfluidic plasmonic metasurface chip biological image detection system as described in claim 1, characterized in that, The operating space between the upper and lower electrode plates is encapsulated with a filling medium for droplet movement.

3. The integrated digital microfluidic plasmonic metasurface chip biological image detection system as described in claim 2, characterized in that, The filling medium is silicone oil or air.

4. The integrated digital microfluidic plasmonic metasurface chip biological image detection system as described in claim 1, characterized in that, The digital microfluidic chip has a driving electrode array with multiple electrodes to accommodate more droplets, build a complex liquid path network, and achieve high-throughput detection.

5. The integrated digital microfluidic plasmonic metasurface chip biological image detection system as described in claim 1, characterized in that, The plasmonic metasurface chip includes an array of gold nanostructures, which can be adapted to the detection of different biomolecules by adjusting the size, shape and arrangement of the gold nanostructures.

6. The integrated digital microfluidic plasmonic metasurface chip biological image detection system as described in claim 1, characterized in that, The wavelength of the light source is matched with the resonant wavelength of the plasmonic metasurface chip to excite plasmonic resonance.

7. The integrated digital microfluidic plasmonic metasurface chip biological image detection system as described in claim 1, characterized in that, Multiple detection sites are set on the digital microfluidic chip, each site corresponding to a plasmonic metasurface detection unit. By adding an additional optical path module, multiple biomolecular indicators can be detected simultaneously.

8. The integrated digital microfluidic plasmonic metasurface chip biological image detection system as described in claim 1, characterized in that, It also includes image processing software for analyzing images captured by CMOS image sensors, extracting image intensity changes caused by plasmon resonance, and obtaining detection results.

9. The integrated digital microfluidic plasmonic metasurface chip biological image detection system as described in claim 8, characterized in that, The image processing software is a MATLAB program, which can batch process images of multiple detection sites to achieve high-throughput, multi-index biomolecular detection.

10. The integrated digital microfluidic plasmonic metasurface chip biological image detection system as described in claim 1, characterized in that, The digital microfluidic chip has programmable liquid circuitry, enabling high-throughput or multi-index biomolecular detection at the same time.

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