Digital microfluidic chip, detection system and spectral information processing method

Abstract

The application discloses a double-plate micro-fluidic chip, which comprises an upper electrode plate, a lower electrode plate, a detection chip, conductive pads and a controllable droplet, wherein the upper electrode plate and the lower electrode plate are oppositely arranged at a predetermined distance apart from each other, two conductive pads are arranged between the upper electrode plate and the lower electrode plate, the upper and lower ends of the conductive pads are in contact with the upper electrode plate and the lower electrode plate respectively, a cavity is formed between the upper and lower electrode plates, the controllable droplet is arranged in the cavity between the upper and lower electrode plates and is in contact with the upper and lower electrode plates respectively, the detection chip is mounted on the upper electrode plate or the lower electrode plate, the detection chip extends into the cavity between the upper and lower electrode plates and can be in contact with the controllable droplet.

Description

Technical Field

[0001] This invention relates to the field of microfluidics, and more particularly to a digital microfluidic chip, a detection system, and a spectral information processing method. Background Technology

[0002] Digital microfluidics technology utilizes dielectric wetting to alter the contact angle of droplets using DC or AC voltage, enabling various operations such as movement, mixing, and separation of microliters or even nanoliters of droplets on a chip several centimeters in size. This technology offers advantages such as small size, low reagent consumption, and automated operation, and can be widely applied in biomedicine, chemical analysis, drug screening, biosensing, and nucleic acid analysis. Compared to traditional microfluidics, digital microfluidics eliminates the need for complex microfabricated components such as microchannels, microvalves, micropumps, and microstructures to control minute amounts of liquids, significantly reducing device size and fabrication complexity.

[0003] To facilitate the widespread application of microfluidic technology in practical detection, this invention integrates various detection and corresponding result readout methods based on its flexible droplet manipulation, including paper-based detection, electrochemical detection, and optical detection. Currently, there are diverse biochemical sensing technologies based on digital microfluidics; however, achieving flexible manipulation and result reading of microdroplets while providing rapid, accurate, and highly sensitive detection results is one of the current directions for the development of detection technology. In view of this, this invention is proposed. Summary of the Invention

[0004] This invention provides a digital microfluidic chip and detection system integrating biochemical sensors and label-free spectral detection, as well as a spectral information processing method. Specific detection can be achieved by modifying different types of probes onto the detection chip and embedding multiple chips. When using a transparent substrate, the optical path can directly pass through the chip for in-situ detection, thus avoiding damage and contamination to the biochemical chip during use, which would affect the accuracy and sensitivity of the chip's detection.

[0005] To achieve the objectives of this invention, the following technical solution is adopted:

[0006] A dual-plate microfluidic chip includes an upper plate, a lower plate, a detection chip, conductive pads, and a controllable droplet. The upper and lower plates are positioned opposite each other at a predetermined distance. Two conductive pads are disposed between the upper and lower plates, with their upper and lower ends contacting the upper and lower plates, respectively. A cavity is formed between the upper and lower plates. The controllable droplet is disposed within this cavity, with its upper and lower portions contacting the upper and lower plates, respectively. The detection chip is mounted on either the upper or lower plate, extending into the cavity between the plates and contacting the controllable droplet.

[0007] The dual-plate microfluidic chip has an upper plate with a mounting through hole, through which the lower part of the detection chip passes and enters the cavity between the upper and lower plates.

[0008] The dual-plate microfluidic chip has a mounting through hole in the lower plate, through which the upper part of the detection chip passes into the cavity between the upper and lower plates.

[0009] The dual-plate microfluidic chip, wherein the detection chip includes a biochemical sensing chip, the detection surface of which extends into the cavity between the upper and lower plates.

[0010] The dual-plate microfluidic chip includes a detection chip comprising a substrate, and a biochemical sensing chip adhered to the substrate.

[0011] A digital microfluidic chip detection system includes an optical path system, a spectrometer, a computer, a microfluidic chip control host, and control peripherals. The optical path system includes a light source, and the control peripherals are located on the optical path of the emitted light from the light source. The control peripherals are used to carry the dual-plate microfluidic chip as described above. The spectrometer is used to receive the reflected light from the dual-plate microfluidic chip and send the spectral information to the computer. The microfluidic chip control host controls the control peripherals, and the computer controls the microfluidic chip control host.

[0012] A method for processing spectral information, wherein the spectral information is spectral information of a dual-plate microfluidic chip detected by the detection system described above, wherein the method includes:

[0013] S1. Blank Sensor Chip Detection: The microfluidic chip is placed horizontally directly below the optical path system. The thin film layer on the substrate surface of the blank sensor chip generates reflected light. and the formation of reflected light on the substrate surface layer. Calculate the light intensity formed after the interference of two beams. ;

[0014] S2. Sensor chip detection of the incubation detection probe: The microfluidic chip is placed horizontally directly below the optical path system. The light intensity R formed by the interference between the reflected light from the probe surface and the light reflected from the substrate surface layer is measured. capt (λ);

[0015] S3. Sensor chip detection of target capture: The microfluidic chip is placed horizontally directly below the optical path system. A controllable droplet is moved to the detection chip, where it contacts and reacts with the probe of the sensor chip. The probe captures the target molecule in the droplet. The light intensity R is formed by the interference between the reflected light from the detection probe on the thin film of the detection chip and the light reflected from the substrate surface layer. dect (λ).

[0016] The spectral information processing method further includes:

[0017] S4: After normalizing the spectra in steps S1-S3 above, perform time-frequency conversion to convert the wavelength domain spectrum to the frequency domain.

[0018] S5: Identify the peak frequencies and corresponding interference peaks within the frequency domain spectrum obtained in step S4. Calculate the phase information at the peak;

[0019] S6: Calculate the phase difference between the probe and the data after capturing the target detection molecule at the peak frequency relative to the blank chip;

[0020] S7: Calculate the changes in optical path length and dielectric layer thickness based on the phase difference obtained in step S6, and solve for the change in thin film thickness caused by the capture of target molecules. . Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a dual-plate microfluidic chip structure with an integrated sensor chip on the upper plate.

[0022] Figure 2 This is a schematic diagram of a dual-plate microfluidic chip structure with a sensor chip integrated on the lower plate.

[0023] Figure 3 is a schematic diagram of a dual-plate digital microfluidic chip structure with an integrated sensor chip on the upper plate.

[0024] Figure 4 is a schematic diagram of a dual-plate digital microfluidic chip structure with an integrated sensor chip on the lower plate.

[0025] Figure 5 is a schematic diagram of a dual-plate digital microfluidic chip structure with multiple sensor chips integrated on the upper plate.

[0026] Figure 6 is a schematic diagram of the dual-plate digital microfluidic chip structure with an integrated sensor chip on the upper plate.

[0027] Figure 7 is a schematic diagram of various sensor chip configuration methods;

[0028] Figure 8 This is a schematic diagram of a digital microfluidic chip detection system;

[0029] Figure 9 is a schematic diagram of the relevant steps in the method for calculating the concentration of the detected substance;

[0030] Figure 10 This is a schematic diagram of the droplet detection circuit. Detailed Implementation

[0031] The following is in conjunction with the appendix Figure 1-10The specific embodiments of the present invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The embodiments described are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0032] The terms "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of the invention include the specific features, structures, or characteristics described in connection with that embodiment. Therefore, the terms "comprising," "including," "having," and variations thereof in this specification mean "including but not limited to," unless otherwise specifically emphasized.

[0033] like Figure 1 As shown, the dual-plate microfluidic chip with an integrated sensor chip on the upper plate includes an upper plate 1, a lower plate 2, a detection chip 3, conductive pads 4, and a controllable droplet 5. The upper plate 1 and lower plate 2 are positioned opposite each other at a predetermined distance, and two conductive pads 4 are disposed between the upper plate 1 and lower plate 2. Optionally, the area of ​​the lower plate 2 is larger than that of the upper plate 1, and the conductive pads 4 are located at the edge of the upper plate 1. The upper and lower ends of the conductive pads 4 contact the upper plate 1 and lower plate 2 respectively, and the two conductive pads 4 are positioned opposite each other at a predetermined distance, forming a cavity between the upper and lower plates. The controllable droplet 5 is disposed in the cavity between the upper plate 1 and lower plate 2, with its upper and lower parts contacting the upper plate 1 and lower plate 2 respectively. The detection chip 3 is mounted on the upper surface of the upper plate 1, and its lower part passes through a mounting hole in the upper plate into the cavity between the upper and lower plates, where it can contact the controllable droplet 5. The spacing between the upper and lower electrodes can be controlled by the conductive pad 4. Alternatively, a conductive adhesive mixed with polystyrene microspheres of different sizes can be used instead of the conductive pad, and the spacing between the chips can be controlled by the diameter of the microspheres. The manipulable droplet 5 can be programmed to move, allowing the detection chip 3 to come into contact with the manipulable droplet 5 during use.

[0034] The upper electrode 1 includes a substrate 11, an electrode layer 12, and a hydrophobic layer 13. The electrode layer 12 is disposed on the lower surface of the substrate 11, and the hydrophobic layer 13 is coated on the electrode layer 12. The electrode layer 12 faces the lower electrode 2. The lower electrode 2 includes a substrate 21, an electrode layer 22, a dielectric layer 23, and a hydrophobic layer 24. The electrode layer 22 is disposed on the upper surface of the substrate 21. The dielectric layer 23 covers the electrode layer 22 and completely covers the entire surface and sides of the electrode layer 22. The hydrophobic layer 24 is coated on the dielectric layer 23 and faces the upper electrode 1. Generally, the upper electrode 1 is used for grounding, and the lower electrode 2 is used to connect to a controllable voltage source, the controllable voltage range of which can be, for example, 30-150V.

[0035] The conductive pad 4 is directly electrically connected to the lower electrode plate 2, that is, the lower end of the conductive pad 4 is electrically connected to the electrode layer 22 of the lower electrode plate 2; the upper end of the conductive pad 4 is in contact with the hydrophobic layer 13 of the upper electrode plate 1.

[0036] The detection chip 3 includes a biochemical sensor chip 31, an adhesive layer 32, and a substrate 33. The adhesive layer 32 is disposed on the lower surface of the substrate 33. The biochemical sensor chip 31 is bonded to the substrate through the adhesive layer 32. The biochemical sensor chip 31 is inserted into the cavity between the upper and lower electrodes through a mounting hole in the upper electrode. During chip use, the biochemical sensor chip 31 can come into contact with the controllable droplet 5. The contact surface between the biochemical sensor chip 31 and the droplet 5 is called the detection surface.

[0037] In the foregoing description, the substrate can be one of the following: planar glass, paper, polyester film, or printed circuit board (PCB), preferably a transparent material. The electrode material can be one of the following: metal, metal oxide, or polycrystalline silicon. The dielectric layer material can be parylene, Si3N4, Al2O3, etc. The hydrophobic material can be Teflon, CYTOP dispersion, or FluoroPel. The biochemical sensor chip can use silicon-based materials, metallic materials, non-metallic materials, compounds, polymers, etc., as the matrix, and its surface thin film layer can be formed by deposition, growth, bonding, or adhesive methods. The target analytes of the biochemical sensor chip can be biomolecules, non-biomolecules, cells, tissues, viruses, microorganisms, bacteria, etc.

[0038] Figure 2The structure of a dual-plate microfluidic chip with a sensor chip integrated in the lower plate is shown. The main structure of this dual-plate microfluidic chip is the same as that of the dual-plate microfluidic chip with a sensor chip integrated in the upper plate, the difference being the mounting position of the detection chip 3. The lower plate 2 has a mounting through-hole that penetrates the substrate 21, electrode layer 22, dielectric layer 23, and hydrophobic layer 24. The biochemical sensing chip 31 is inserted into the cavity between the upper and lower plates through the mounting through-hole in the lower plate, allowing it to contact the controllable droplet 5 during chip use. The contact surface between the biochemical sensing chip 31 and the droplet 5 is called the detection surface.

[0039] Figure 3 This illustrates another structure of a dual-plate microfluidic chip with an integrated sensor chip on the upper plate, and... Figure 1 The difference between the dual-board microfluidic chips shown is that... Figure 1 In the dual-plate microfluidic chip, the upper plate 1 has a mounting through-hole facing an electrode 22 on the lower plate 2, and the detection chip 3 is also mounted at this position. Figure 3 The mounting through hole of the upper electrode plate 1 of the dual-plate microfluidic chip faces the middle position of the two electrode plates 22 of the lower electrode plate 2, and the detection chip 3 is also installed at this position.

[0040] Figure 4 This illustrates another structure of a dual-plate microfluidic chip with an integrated sensor chip on the lower plate, and... Figure 2 The difference between the dual-board microfluidic chips shown is that... Figure 2 The mounting hole of the lower electrode plate 2 of the dual-plate microfluidic chip is basically coincident with the center of the square electrode (electrode plate 22), and the detection chip 3 is also installed at this position. Figure 4 The mounting through hole of the lower electrode plate 2 of the dual-plate microfluidic chip is located in the middle of the two square electrodes (electrode plates 22) of the lower electrode plate, and the detection chip 3 is also installed in this position.

[0041] Figure 5 This illustrates another structure of a dual-plate microfluidic chip with an integrated sensor chip on the upper plate, and... Figure 1 The difference between the dual-board microfluidic chips shown is that... Figure 5 The detection chip 3 of the dual-plate microfluidic chip includes two biochemical sensing chips 31. The two biochemical sensing chips 31 are bonded to the substrate 33 at a predetermined distance through an adhesive layer 32. The two biochemical chips 31 are respectively inserted into the cavity between the upper and lower plates through two mounting holes opened in the upper plate, and two control droplets 5 can be controlled to contact the two biochemical sensing chips 31 respectively.

[0042] Figure 6 This illustrates another structure of a dual-plate microfluidic chip with an integrated sensor chip on the upper plate, such as... Figure 6As shown, the dual-plate microfluidic chip with an integrated sensor chip on the upper plate includes an upper plate 1, a lower plate 2, a detection chip 3, conductive pads 4, and a controllable droplet 5. The upper plate 1 and lower plate 2 are positioned opposite each other at a predetermined distance. Two conductive pads 4 are disposed between the upper plate 1 and the lower plate 2, with their upper and lower ends respectively contacting the upper plate 1 and the lower plate 2. The two conductive pads 4 are positioned opposite each other at a predetermined distance, forming a cavity between the upper and lower plates. The controllable droplet 5 is disposed in the cavity between the upper plate 1 and the lower plate 2, with its upper and lower parts respectively contacting the upper plate 1 and the lower plate 2. The upper end of the detection chip 3 is embedded in a countersunk hole (blind hole) on the lower surface of the upper plate 1, which saves on additional fixing substrates, ensures a sealed condition, and prevents liquid from seeping out between the plates due to capillary action. The lower end of the detection chip 3 (biochemical sensing chip 31) protrudes beyond the lower surface of the upper electrode 1, extends into the cavity between the upper and lower electrodes, and can contact the controllable droplet 5. The distance between the upper and lower electrodes can be controlled by the conductive pad 4. Alternatively, a conductive adhesive mixed with polystyrene microspheres of different sizes can be used instead of the conductive pad, and the distance between the chips can be controlled by the diameter of the microspheres. The controllable droplet 5 can be moved in a position controlled by a program, and the biochemical sensing chip 31 of the detection chip 3 can contact the controllable droplet 5 during use.

[0043] like Figure 7As shown, the upper electrode plate is a single, integral plate, and its electrode layer is also a single-layer structure. When the electrodes of the lower electrode plate are arranged in an array, there are several ways to set up the detection chips. Specifically: one detection chip 331 can be placed on the upper electrode plate or on the lower electrode plate; multiple detection chips 332 can be placed on the upper electrode plate or on the lower electrode plate respectively; multiple detection chips 333 of different shapes (including circular, rectangular, etc.) can be placed on the upper electrode plate or on the lower electrode plate respectively, where each detection chip 333 can be placed at a position corresponding to one lower electrode plate electrode or at positions corresponding to multiple adjacent lower electrode plates; multiple detection chips 334 can be placed at positions corresponding to multiple non-adjacent lower electrode plates. The advantages of this setup are: if the detection target is singular, a single detection chip can be designed and embedded, or multiple chips can be embedded to detect multiple samples, thereby improving the utilization efficiency of a single digital microfluidic chip; when there are multiple detection targets, multiple detection chips containing different probes can be embedded, enabling single-sample multi-index detection on a single digital microfluidic chip. Different detection probes can also be incubated on the same detection chip, and the detection results at the corresponding locations can be collected separately. Furthermore, the size, shape, and placement of the detection chip can be changed as needed. For example, when the detection chip 31 is placed at positions corresponding to two adjacent lower electrode plates, and two different droplets are manipulated to contact the detection chip, one half of the detection chip 31 can detect sample 1, and the other half can detect sample 2. Therefore, multiple samples can be detected using a single chip, unaffected by crosstalk between samples. The process of embedding multiple detection chips 31 can also be optimized to embed a single chip 31, simplifying the overall chip fabrication process. Under long-term detection conditions, droplets may evaporate, causing non-specific adsorption of the detected sample onto the edges of the detection chip 31. Therefore, using a circular or smaller detection chip 31 can effectively prevent non-specific adsorption and improve the accuracy of subsequent sampling and detection.

[0044] like Figure 8 As shown, the digital microfluidic chip detection system includes an optical path system 51, an optical fiber 52, a spectrometer 53, a computer 54, a microfluidic chip control host 55, and control peripherals 56.

[0045] The optical path system includes a light source 511, a collimating lens 512, a field lens 513, a first aperture 514, a beam splitter 515, an objective lens 516, an imaging lens 517, and a second aperture 518.

[0046] A collimating lens 512 is positioned below the light source 511 to convert the light beam emitted by the collimating light source 511 into a parallel beam. A field lens 513 is positioned below the collimating lens 512 to ensure that the light beam illuminates the entire field of view of the sample uniformly. A first aperture 514 is positioned below the field lens 513 to control the size and shape of the light beam. A beam splitter 515 splits the light beam transmitted through the aperture 514 into two beams. The first beam has the same emission direction as the original beam, and the optical path containing this beam is called the first optical path. The second beam has the emission direction perpendicular to the first beam, and the optical path containing this beam is called the second optical path. An objective lens 516 is positioned on the optical path of the first beam and below the beam splitter to converge the beam. An imaging lens 517 is positioned on a third optical path opposite to the direction of the second optical path and is located outside the beam splitter 515. A second aperture 518 is positioned outside the imaging lens 517 to further control the size and shape of the transmitted light beam and limit the size of the irradiated area.

[0047] The control peripheral 56 is located below the objective lens 516. The control peripheral 56 carries the microfluidic chip as described above and has a moving component, allowing the chip to move freely in the X, Y, and Z directions to achieve detection and focusing of the chip at different positions. The converging beam transmitted through the objective lens 516 illuminates the microfluidic chip. The control peripheral 56 is electrically connected to the microfluidic chip control host 55, allowing the microfluidic chip to move freely without being restricted by the position of the control host 55. The control peripheral 56 also has an electrical connection terminal (not shown in the figure) connected to the corresponding electrode of the microfluidic chip for controlling the movement, separation, and mixing of the droplets 5. The converging beam transmitted through the objective lens 516 illuminates the microfluidic chip. After being reflected by the microfluidic chip, the beam is reflected by the beam splitter 515 and enters the third optical path. It then passes through the imaging lens 517, the second aperture 518, and the optical fiber 52 before being received by the spectrometer 53. The control peripheral 56 is electrically connected to the microfluidic chip control host 55. The microfluidic chip control host 55 controls the operation of the microfluidic chip by applying control signals to the control peripheral 56. The microfluidic chip control host 55 is connected to the computer 54 via a signal transmission line. The computer 54 controls the microfluidic chip control host 55. The second aperture 518 is connected to the spectrometer 53 via an optical fiber 52. The spectrometer 53 is used to analyze optical signals and is also connected to the computer 54 via a signal transmission line. The computer 54 receives the signals detected by the spectrometer 53. That is, the reflected light from the microfluidic chip is transmitted into the spectrometer via optical fiber, and finally the spectral information detected by the spectrometer is transmitted to the computer for analysis via a data line. Since the spectral curves collected by the spectrometer before and after the reaction will have a phase shift, the changes produced on the surface of the sensor (microfluidic chip) can be calculated based on the shift. At the same time, the host can be controlled through the program set in the computer, thereby realizing the manipulation of the controllable droplets.

[0048] When the microfluidic chip is placed on the control peripheral 56, the sensor chip 31 needs to be placed in the first optical path, and the biochemical sensor chip 31 faces the light source 511. When it is placed on the upper electrode plate 1, the lower electrode plate 2 is a transparent plate. When it is placed on the lower electrode plate 2, the upper electrode plate 1 is a transparent plate, so that the light beam can be irradiated onto the sensor chip 31 through the lower electrode plate 2 or through the upper electrode plate 1.

[0049] like Figure 9 As shown, the specific processing steps for spectral information are as follows:

[0050] S1: Blank sensor chip detection

[0051] The integrated digital microfluidic chip is placed horizontally directly below the optical path system. Since there is a thin film of silicon dioxide on the silicon substrate of the blank sensor chip 31, reflected light can be formed on the upper surface of the film. Reflected light is formed on the surface of the substrate. ,in Let λ be the wavelength of the incident light. The two beams have an optical path difference, and they interfere on the upper surface of the thin film. The reflectivity of the light after interference can be expressed as:

[0052] (1)

[0053] in, This represents the interference light reflected from a blank silicon wafer at a wavelength of... Reflectivity at that location The refractive index of the silicon oxide film is given. The thickness of the oxide thin film is given.

[0054] S2: Sensor chip detection of incubation detection probe

[0055] The integrated digital microfluidic chip is placed horizontally directly below the optical path system. Because detection probes are incubated (or fixed) on the thin film on the chip surface, light incident on the sensor surface is reflected from the probe surface, scattered between the probe molecules, and then reflected by the substrate. This is equivalent to a change in the film thickness. The light formed by the interference of the two beams is as follows:

[0056] (2)

[0057] In the formula, The refractive index of the probe is... This represents the relative change in the thickness of the oxide film layer due to the probe.

[0058] S3: Sensor chip detection of target acquisition

[0059] After embedding a biosensor chip with a fixed detection probe into a digital microfluidic chip, a droplet containing the target molecule is added into the chip's cavity. The droplet is driven to reach the sensor chip and move back and forth, causing the detection probe on the chip surface to bind to the target molecule. After removing the droplet, the target molecule remains on the chip surface, thus achieving target molecule capture. Optical detection is then performed. Light incident on the sensor surface is reflected from the target molecule surface, scattered between the target molecule and the detection probe, and then reflected by the substrate. This is equivalent to a further change in the film thickness. The light formed by the interference of the two beams at this point is:

[0060] (3)

[0061] In the formula, The refractive index of the target molecule, This refers to the relative change in film thickness caused by fixing the detection probe and capturing the target molecule.

[0062] S4: After normalizing the spectra in steps S1-S3 above, perform Fast Fourier Transform (FFT) to convert the wavelength domain spectrum to the frequency domain.

[0063] (4)

[0064] (5)

[0065] (6)

[0066] In the formula, For frequency. , , The frequency domain signals obtained by fast Fourier transform of the interference spectra obtained after cleaning the bare (blank) chip, the incubation probe, and the target detection are respectively. Represented as the illumination light at wavelength The amplitude at that point.

[0067] S5: Identify the peak frequencies and corresponding interference peaks within the frequency domain spectrum. Calculate the phase information at the peak.

[0068] Since the interference signal at the peak frequency is most sensitive to the optical thickness of the dielectric layer, and the phase change is proportional to the thickness of the dielectric layer, measuring the phase change at the peak frequency allows for more accurate detection of thickness variations. The peak frequency and corresponding interference peak value in the frequency domain spectrum can be identified using the following formula. Calculate the phase information at the peak:

[0069] (7)

[0070] (8)

[0071] (9)

[0072] In the formula, , , These are the phase information at the peak value.

[0073] S6: Calculate the phase difference between the probe and the data after capturing the target detection molecule at the peak frequency relative to the blank chip.

[0074] Subtracting formula (7) from formula (8) yields:

[0075] (10)

[0076] Similarly, by subtracting formula (7) from formula (9), we can obtain:

[0077] (11)

[0078] To address the potential sidelobe effect caused by the FFT transform, the following steps will focus on... Nearby frequency components are averaged to reduce the impact of noise.

[0079] (12)

[0080] (13)

[0081] in It is the number of frequency components within the selected frequency range. and These are the upper and lower limits of the selected frequency range.

[0082] S7: Calculate the changes in optical path length and dielectric layer thickness using phase difference.

[0083] The length of the optical path is equal to the physical thickness of the medium multiplied by its refractive index. Therefore, the change in the thickness of the medium layer can be calculated.

[0084] (14)

[0085] In the formula, For the change in optical path length, This represents the change in the thickness of the dielectric layer.

[0086] Compared to a blank silicon wafer, the changes in optical path length after incubating the probe and detecting the target are as follows:

[0087] (15)

[0088] (16)

[0089] In summary, the change in film thickness caused by the capture of target molecules can be calculated using formulas (15) and (16). .

[0090] According to this The concentration of target molecules in the controllable droplet can then be calculated using existing methods, which will not be elaborated upon here. In the experiment, ensuring a sufficient number of detection probes fixed to the surface of the sensor chip is crucial. A higher concentration of target molecules in the droplet results in more target molecules being captured by the detection probes, leading to a greater change in the relative film thickness. Therefore, the sensor chip can be used for qualitative or quantitative detection of target molecules in the droplet. Furthermore, the detection probes bind to corresponding target molecules, enabling specific detection of these molecules.

[0091] To achieve precise control of droplet actuation, this invention also provides a droplet detection circuit and a droplet detection method. This method can be applied to the droplet actuation control in step S3.

[0092] like Figure 10 As shown, the input voltage source The first terminal is connected to the sensing resistor R test The first terminal is the sensing resistor R. test The second end is connected to the electrode layer 12 of the upper electrode plate 1; input voltage source The second end is connected to the detection line via the first switch K1; the detection line is connected to the second electrode layer 22 of the lower electrode plate 2 via the second switch K2, and the detection line is connected to the second electrode layer 22 of the lower electrode plate 2 via the third switch K3. The voltage to be measured is the detection resistor R. test The voltage V between the second end and each electrode layer 22 of the lower electrode plate 2 out The circuit described above can detect the voltage between the upper electrode and each lower electrode layer in real time, for example... Figure 10 The text shows two respectively. and Of course, the number of voltages to be measured is not limited by this, and it is the same as the number of electrode layers 22 of the lower electrode plate 2.

[0093] Because the dielectric constant of droplet 5 differs from that of the surrounding air or material, its movement between the upper and lower electrode plates causes a change in capacitance. After the device is connected, the output voltage is monitored. The total capacitance between the upper and lower electrodes in the current state can be calculated. This allows for real-time tracking of the droplet's position and detection of its current movement. The specific detection steps are as follows.

[0094] Assume the input signal is ,capacitance The impedance under alternating current is ,in, It is the angular frequency of the input signal. This can be obtained from voltage division.

[0095] (17)

[0096] Therefore, it can be calculated that

[0097] (18)

[0098] When there are no droplets in the interplate gap corresponding to a single electrode of the current electrode, the measured total capacitance is equivalent to the dielectric layer capacitance C23. dielectric capacitance C with air dielectric air Series connection (the capacitance of the hydrophobic layer 24 is negligible here), assuming the size of a single array electrode 22 on the lower plate is... Total capacitance The expression is:

[0099] (19)

[0100] in, and The dielectric constants of air and dielectric layer 23 are respectively. The distance between the upper and lower plates filled with air. The thickness of dielectric layer 23 is given.

[0101] When a droplet is present in the interplate gap corresponding to a single electrode of the current electrode, the measured total capacitance is equivalent to the dielectric layer capacitance C23. dielectric With liquid dielectric partial capacitance C liquid Series connection, total capacitance The expression is:

[0102] (20)

[0103] in, Let be the dielectric constant of the droplet. This represents the distance between the upper and lower plates filled with liquid. Due to the dielectric constant of the liquid... Typically greater than the dielectric constant of air. , > Therefore, the measured capacitance value is larger in the area covered by droplets.

[0104] As the droplet moves between the plates, assuming the droplet is in If the direction is moved, then its position... This determines the area covered by the droplet. Therefore, the capacitance between the two plates is the parallel capacitance formed by the droplet-covered portion and the air-covered portion:

[0105] (twenty one)

[0106] in, These represent the areas covered by the droplets and the air, respectively. For droplets in Coverage length in the direction, This represents the width of the array electrodes. The capacitance of dielectric layer 23 is... , This represents the area of ​​the corresponding dielectric layer. Since dielectric layer 23 forms a series connection with the parallel capacitor, the total capacitance is... It can be represented as:

[0107] (twenty two)

[0108] Total capacitance with position The change in capacitance allows us to deduce the current position of droplet 5.

[0109] (twenty three)

[0110] By monitoring the current total capacitance Real-time calculation of the current droplet position By establishing a curve of this curve versus time, the velocity of the droplet can be calculated.

[0111] Assume the size of the hole is ( The area of ​​the hole is .

[0112] (1) When holes are drilled in the upper electrode plate, the effective area corresponding to the electrode decreases, resulting in a smaller total capacitance. When there are no droplets in the gap between the plates, the measured total capacitance is equivalent to the dielectric layer 23 being connected in series with part of the air dielectric capacitance. The expression is:

[0113] (twenty four)

[0114] When droplets are present in the gaps between the plates, the measured total capacitance is equivalent to dielectric layer 23 being connected in series with a portion of the liquid dielectric capacitance. The expression is:

[0115] (25)

[0116] (2) Similarly, when a hole is drilled in the lower electrode plate, since the lower electrode plate contains a dielectric layer 23, the area corresponding to the dielectric layer will change when calculating the capacitance, and the total capacitance corresponding to the electrode will be:

[0117] (26)

[0118] Therefore, starting with the capacitance corresponding to each electrode When performing real-time monitoring, the normal operating monitoring range of the capacitor at the perforation location needs to be redefined. Similarly, the effect of the perforation needs to be considered when calculating the droplet movement speed, and the formula needs to be modified to ensure that the chip can operate normally and perform speed detection. When multiple detection chips are embedded on a single microfluidic chip, real-time monitoring of the droplet speed can effectively ensure the consistency of parallel experimental conditions.

[0119] The main advantages of this invention are as follows:

[0120] (1) Compared with directly processing the microfluidic substrate, the method of this patent directly drills or grooves the substrate, eliminating the need for complex micro-nano fabrication methods for electrical impedance chips, as well as the need for precious metal plating for SPR and Raman spectroscopy, and has virtually no impact on subsequent chip processing. Therefore, it can greatly simplify chip fabrication and processing steps and reduce manufacturing costs. For bipolar microfluidic chips, this method allows the detection surface of the biochemical sensor chip to face inward, avoiding the influence of external factors such as the environment.

[0121] (2) When the substrate opposite the chip substrate is made of transparent material, the chip can be placed directly in the system, which can realize the automated operation of the reaction and the real-time collection of detection data. After adding the sample to be detected and the solution required for detection to the digital microfluidic chip, no other additional experimental instruments are required. Using the system of this patent, the detection reaction and data collection can be carried out, realizing the integrated operation from "sample in" to "result out".

[0122] (3) Existing fluorescent labeling measurement methods are usually cumbersome, requiring the following steps: sample incubation, washing with washing solution, adding chromogenic substrate, washing with washing solution, and reading the fluorescence result. The method of this patent eliminates the steps of adding the substrate and subsequent steps, resulting in faster detection speed, simpler operation, reduced consumption of detection solution, and lower requirements for user expertise. Furthermore, the label-free protein detection method does not require fluorescent or chemical labeling of proteins or other detection markers, avoiding labeling-related effects such as fluorescence quenching and enzyme inactivation. Moreover, label-free specific detection can be achieved by modifying the sensor surface with the corresponding capture probe.

[0123] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A digital microfluidic chip detection system, comprising an optical path system, a spectrometer, a computer, a microfluidic chip control host, and control peripherals, characterized in that: The optical path system includes a light source, and the control peripherals are located on the optical path of the emitted light from the light source. The control peripherals are used to carry the dual-board microfluidic chip, the spectrometer is used to receive the reflected light from the dual-board microfluidic chip and send the spectral information to the computer, the microfluidic chip control host controls the control peripherals, and the computer is used to control the microfluidic chip control host. The dual-plate microfluidic chip includes an upper plate, a lower plate, a detection chip, conductive pads, and a controllable droplet. Its features include: the upper and lower plates are positioned opposite each other at a predetermined distance; two conductive pads are disposed between the upper and lower plates, with their upper and lower ends respectively contacting the upper and lower plates; a cavity is formed between the upper and lower plates; the controllable droplet is disposed in the cavity between the upper and lower plates, with its upper and lower parts respectively contacting the upper and lower plates; the detection chip is mounted on the upper plate; a blind hole is formed on the lower surface of the upper plate; the upper end of the detection chip is embedded in the blind hole; and the lower end of the detection chip protrudes beyond the lower surface of the upper plate, extending into the cavity between the upper and lower plates and contacting the controllable droplet. The digital microfluidic chip detection system also includes a droplet detection circuit, which includes an input voltage source. and detection resistor R test ,in: Input voltage source The first terminal is connected to the sensing resistor R test The first terminal is the sensing resistor R. test The second end is connected to the electrode layer of the upper plate; input voltage source The second end is connected to the detection line via the first switch; the detection line is connected to the second electrode layer of the lower electrode plate via the second switch; the detection line is connected to the first electrode layer of the lower electrode plate via the third switch; the voltage to be measured is the detection resistor R. test The voltage V between the second terminal and each electrode layer of the lower plate out ; The digital microfluidic chip detection system monitors the output voltage. The total capacitance between the upper and lower plates in the current state is calculated. This allows for real-time tracking of the droplet's position and detection of its current movement. The specific detection steps are as follows: Assume the input signal is Total capacitance The impedance under alternating current is ,in, It is the angular frequency of the input signal, which can be obtained from voltage division: （17） Calculated: (18) When there is no droplet in the gap between the plates corresponding to a single electrode, the measured total capacitance is equivalent to the dielectric layer capacitance C. dielectric capacitance C with air dielectric air In series, assuming the size of a single array electrode on the lower plate is... Total capacitance The expression is: （19） in, and The dielectric constants of air and the dielectric layer are respectively. The distance between the upper and lower plates filled with air. The thickness of the dielectric layer; When a droplet is present in the inter-plate gap corresponding to a single electrode of the current electrode, the measured total capacitance is equivalent to the dielectric layer capacitance C. dielectric With liquid dielectric partial capacitance C liquid Series connection, total capacitance The expression is: （20） in, Let be the dielectric constant of the droplet. The distance between the upper and lower plates filled with liquid is determined by the dielectric constant of the liquid. Typically greater than the dielectric constant of air. , > Therefore, the capacitance value measured is larger in the area covered by droplets; As the droplet moves between the plates, assuming it moves in the L1 direction, its position... The area covered by the droplet is determined; therefore, the capacitance between the two plates is the parallel capacitance formed by the droplet-covered portion and the air-covered portion. （21） in, These represent the areas covered by the droplets and the air, respectively. For droplets in Coverage length in the direction, The width of the array electrodes is ; the capacitance of the dielectric layer is , This represents the area of ​​the corresponding dielectric layer. Since the dielectric layer and the parallel capacitor form a series connection, the total capacitance is... Represented as: （22） Total capacitance with position The change in capacitance allows us to deduce the droplet's current position by measuring the change in capacitance. （23） in, By monitoring the current total capacitance Real-time calculation of the current droplet position By establishing a curve of this curve versus time, the velocity of the droplet can be calculated. Assume the size of the hole is ,in The area of ​​the hole is , (1) When holes are drilled on the upper electrode plate, the effective area corresponding to the electrode is reduced, resulting in a smaller total capacitance. When there are no droplets in the gap between the plates, the measured total capacitance is equivalent to the dielectric layer (23) being connected in series with part of the air dielectric capacitance. The expression is: （24） When droplets are present in the gaps between the plates, the measured total capacitance is equivalent to the dielectric layer (23) being connected in series with a portion of the liquid dielectric capacitance, and the total capacitance is... The expression is: （25） (2) Similarly, when a hole is drilled in the lower electrode plate, since the lower electrode plate contains a dielectric layer (23), the area corresponding to the dielectric layer will change when calculating the capacitance, and the total capacitance corresponding to the electrode will be: （26）。 2. A method for processing spectral information, wherein the spectral information is the spectral information of a dual-plate microfluidic chip detected by the detection system as described in claim 1, characterized in that... The method includes: S1. Blank Sensor Chip Detection: The microfluidic chip is placed horizontally directly below the optical path system. The thin film layer on the substrate surface of the blank sensor chip generates reflected light. and the formation of reflected light on the substrate surface layer. Calculate the light intensity formed after the interference of two beams. ; S2. Sensor chip detection of the incubation detection probe: The microfluidic chip is placed horizontally directly below the optical path system. The light intensity R formed by the interference between the reflected light from the probe surface and the light reflected from the substrate surface layer is measured. capt (λ); S3. Sensor chip detection of target capture: The microfluidic chip is placed horizontally directly below the optical path system. A controllable droplet is moved to the detection chip, where it contacts and reacts with the probe of the sensor chip. The probe captures the target molecule in the droplet. The light intensity R is formed by the interference between the reflected light from the detection probe on the thin film of the detection chip and the light reflected from the substrate surface layer. dect (λ); S4: After normalizing the spectra in steps S1-S3 above, perform time-frequency conversion to convert the wavelength domain spectrum to the frequency domain. S5: Identify the peak frequencies and corresponding interference peaks within the frequency domain spectrum obtained in step S4. Calculate the phase information at the peak; S6: Calculate the phase difference between the probe and the data after capturing the target detection molecule at the peak frequency relative to the blank chip; S7: Calculate the changes in optical path length and dielectric layer thickness based on the phase difference obtained in step S6, and solve for the change in thin film thickness caused by the capture of target molecules. .

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