A measuring method for a micro-scale temperature field measuring chip based on frequency conversion light emitting technology

Abstract

This invention discloses a measurement method for a microscale temperature field sensing chip based on frequency conversion luminescence technology, belonging to the field of temperature measurement technology. The invention uses temperature as the abscissa and fluorescence intensity ratio as the ordinate, obtaining a functional relationship between fluorescence intensity ratio and temperature, i.e., a temperature calibration curve, through data fitting. One side of the luminescent material film layer of the sensing chip is attached to the surface being measured. Images of the corresponding wavelength bands of characteristic emission peaks A and B are acquired, and pixel-level processing is performed on the two grayscale images to calculate the grayscale ratio of each pixel. The grayscale ratio of each pixel is substituted into the temperature calibration curve to obtain the temperature value corresponding to that pixel. Through image rendering technology, the temperature data is mapped to corresponding color information, generating a visualized temperature field image reflecting the temperature distribution of the measured area, thus intuitively presenting the spatial distribution of temperature.

Description

Technical Field

[0001] This invention belongs to the field of temperature measurement technology, specifically, it relates to a measurement method for a microscale temperature field measurement chip based on frequency conversion light emission technology. It can be applied to high-precision, visualized temperature measurement of microscale temperature fields (such as planes with temperature gradients, cell surfaces, etc.). Background Technology

[0002] Temperature measurement technology plays a crucial role in many fields, including industrial production, biomedicine, and materials science. With the development of technology, the demand for microscale, high-precision, and non-contact temperature measurement is becoming increasingly urgent. For example, in cell metabolism research, it is necessary to monitor the temperature changes of individual cells or cell populations, and in the thermal analysis of electronic devices, it is necessary to obtain the temperature gradient distribution on the chip surface. In existing temperature measurement technologies, contact temperature measurement (such as thermocouples and thermistors) is difficult to achieve accurate temperature measurement in microscale areas and will interfere with the temperature field of the object being measured; although traditional optical temperature measurement is non-contact, its spatial resolution is low and it is difficult to meet the needs of microscale scenes. Fluorescence thermometry measures temperature based on the correlation between the fluorescence properties of fluorescent materials (such as fluorescence intensity ratio and fluorescence lifetime) and temperature, offering advantages such as non-contact measurement, high sensitivity, and high spatial resolution. Among these, the method using fluorescence intensity ratio (FIR) effectively avoids interference from factors such as excitation light intensity fluctuations and uneven material concentration, resulting in higher measurement accuracy. However, existing fluorescence intensity ratio-based thermometry techniques largely rely on spectrometers for single-point or small-area spectral acquisition and analysis, making it difficult to achieve large-area, rapid, and visualized temperature measurement, thus limiting its application in scenarios such as dynamic temperature field monitoring. Therefore, there is an urgent need for a method that combines the principles of luminescence thermometry with imaging technology to achieve rapid, visualized, and high-precision measurement of microscale temperature fields. (Invention Content) The purpose of this invention is to provide a measurement method for a microscale temperature field measurement chip based on spectral imaging technology. By integrating an upconversion or downconversion luminescent material film with temperature response characteristics, and combining spectral imaging technology with the principle of fluorescence intensity ratio thermometry, a rapid, visualized, and high-precision measurement of the microscale temperature field can be achieved. A method for measuring microscale temperature fields using a temperature sensing chip based on spectral imaging technology mainly includes the following components: Luminescent material film: This is the core functional layer of the temperature sensing chip, and it is made of fluorescent material that can achieve upconversion luminescence or downconversion luminescence. This film has temperature-dependent luminescence characteristics, and the ratio of fluorescence intensity of at least two characteristic emission peaks in its emission spectrum changes monotonically and stably with temperature. Upconversion luminescent materials can be selected from rare earth ion (Er, Tm, Ho, etc.) doped fluorides, vanadates, and borates (such as NaYF4, NaGF4, LaVO4, etc.), which can emit characteristic fluorescence in the visible light band under near-infrared light excitation. Downconversion luminescent materials can be selected from: rare earth-doped oxides (such as Y2O3:Eu). 3+ Gd2O3:Tb 3+ Materials such as CdSe / ZnS quantum dots and PbS quantum dots (or quantum dots) can emit fluorescence in specific wavelengths when excited by ultraviolet or visible light.

[0003] Substrate: Used to support the luminescent material film layer. Different materials can be selected according to the application scenario, such as silicon wafers, glass sheets, and flexible polymer substrates (such as polydimethylsiloxane PDMS, polyimide PI, etc.) to adapt to different test surfaces (such as rigid planes, flexible curved surfaces, cell surfaces, etc.). Encapsulation layer: Covers the surface of the luminescent material film to protect the film from the influence of the external environment (such as humidity and chemical corrosion) without affecting the incident excitation light and the emission of fluorescence. The material can be a transparent polymer (such as polymethyl methacrylate PMMA) or a silicon dioxide film. This method for measuring microscale temperature fields using spectral imaging includes the following steps: Step 1: Establish the calibration relationship between fluorescence intensity ratio and temperature Spectroscopic testing: The prepared luminescent material film is placed in a temperature-controlled environment (such as a temperature control table), and the emission spectrum of the film at different temperatures is collected using a spectrometer; the corresponding excitation light source is selected according to the type of film (near-infrared laser is used for upconversion film, and ultraviolet lamp or visible light laser is used for downconversion film). Data processing: From the emission spectra collected at different temperatures, two characteristic emission peaks with obvious temperature responses (denoted as peak A and peak B) were selected, and the fluorescence intensity ratio of peak A to peak B at each temperature was calculated (FIR = I0). A / I B or I B / I A Calibration curve fitting: With temperature as the abscissa and fluorescence intensity ratio as the ordinate, the functional relationship between fluorescence intensity ratio and temperature is obtained through data fitting, i.e., the temperature calibration curve, which serves as the basis for subsequent temperature measurements. Step 2: Spectral Imaging and Temperature Field Visualization Measurement Sample bonding: The luminescent material film layer of the spectral imaging temperature measurement chip is bonded to the surface of the object being measured (such as a metal plane with a temperature gradient, the cell surface in a cell culture dish, etc.) to ensure that the film layer is in close contact with the surface being measured, so as to achieve effective temperature transfer. Spectral imaging acquisition: A spectroscopic camera (capable of multi-band imaging, separately acquiring images of the bands corresponding to characteristic emission peaks A and B) is used to image the area under test, obtaining grayscale images (Ig) of peak A at different locations within the area under test. A (img) and grayscale image of peak B (I B (img). Gray-scale ratio calculation: Perform pixel-level processing on two gray-scale images and calculate the gray-scale ratio (GR = G) for each pixel. A / G B or G B / G A G A For I A The grayscale value of that pixel in the image, G B For I B (The grayscale value of the pixel in the image); Since the grayscale value of the image is linearly correlated with the fluorescence intensity of the corresponding band, the grayscale ratio can be used as an equivalent substitute for the fluorescence intensity ratio. Temperature Inversion and Visualization: By substituting the grayscale ratio of each pixel into the established temperature calibration curve, the temperature value corresponding to that pixel is obtained. Through image rendering technology, the temperature data is mapped to corresponding color information, generating a visualized temperature field image reflecting the temperature distribution of the measured area, thus intuitively presenting the spatial distribution of temperature. In other words, by using image rendering technology, different temperature values ​​are mapped to different colors to generate a visualized temperature field image of the measured area, achieving an intuitive presentation of temperature distribution.

[0004] Compared with the prior art, the present invention has the following beneficial effects: High precision and high stability: Temperature measurement based on fluorescence intensity ratio effectively eliminates interference from factors such as excitation light intensity fluctuations and uneven material film thickness, resulting in high measurement accuracy; at the same time, the temperature response characteristics of the upconversion / downconversion luminescent materials are stable, ensuring high reliability for long-term use.

[0005] Visualization and high spatial resolution: By combining spectral imaging technology, the temperature field distribution image of the measured area can be directly acquired, realizing visualized temperature monitoring; the high pixel characteristics of the spectral camera enable the chip to have micron-level or even submicron-level spatial resolution, which can meet the needs of microscale temperature measurement (such as cell surface temperature measurement). Non-contact and widely applicable: During temperature measurement, the chip and the object being measured only need to be in surface contact, without direct electrical contact, and will not interfere with the temperature field of the object being measured; the substrate can be made of flexible material to adapt to different shapes of the measured surface, and the light-emitting material film layer can be selected as up-conversion or down-conversion type according to the requirements, which is suitable for different excitation environments and temperature measurement ranges. Rapid Response: Spectral imaging acquisition and data processing can be completed within milliseconds, enabling real-time monitoring of dynamic temperature fields, suitable for scenarios with rapidly changing temperatures (such as transient thermal analysis of electronic devices). For a deeper understanding of the features and technical content of this invention, please refer to the appended detailed description and accompanying drawings. It should be noted that the accompanying drawings are provided for illustrative purposes only and are not intended to limit the scope of the invention. Attached Figure Description

[0006] Figure 1 It is the FIR and T fitting curve; Figure 2 It is a 520nm band grayscale image (I 520 _img); Figure 3 It is a 540nm band grayscale image (I 540 _img); Figure 4 It is a pseudo-color image of the temperature field distribution on the cell surface. Detailed Implementation

[0007] The present invention will be described in detail below with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but should not be considered as limiting the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0008] Example 1: Cell surface temperature sensing chip based on upconversion luminescent material film (1) Chip fabrication ① Preparation of luminescent material film: NaYF4:Yb 3+ E 3+ Upconversion nanoparticles (average particle size 20 nm) were dispersed in deionized water to prepare a dispersion with a concentration of 5 mg / mL. The dispersion was then spin-coated onto the surface of a flexible PDMS substrate (substrate size 10 mm × 10 mm, thickness 50 μm) at a spin-coating speed of 3000 r / min for 30 s. The substrate was subsequently dried at 80 °C for 30 min to form an upconversion luminescent material film with a thickness of approximately 1 μm. Encapsulation: A 200 nm thick silicon dioxide encapsulation layer was deposited on the surface of the luminescent material film using plasma-enhanced chemical vapor deposition (PECVD) technology to complete chip fabrication. (2) Temperature calibration ① Place the prepared chip on a temperature control platform with a temperature control accuracy of ±0.1℃, select a 980nm near-infrared laser as the excitation source (power 50mW), and use a micro-spectrometer (resolution 0.1nm) to collect the emission spectrum every 5℃ in the range of 25℃-60℃. ② Select Er from the spectrum 3+ Two characteristic emission peaks: 520nm ( 2 H 11 / 2 → 4 I 15 / 2 (leap) and 540nm ( 4 S 3 / 2 → 4 I 15 / 2 (Flight transition), calculate the fluorescence intensity ratio of the 520nm and 540nm peaks at different temperatures (FIR=I) 520 / I 540 ). ③ Perform data fitting with temperature T as the x-axis and FIR as the y-axis (e.g.) Figure 1 As shown in the figure, the calibration equation is obtained as: T = a×ln (FIR) + b (where a and b are the fitting coefficients, and a≈-25.3 and b≈89.6 are calculated from the experimental data). The correlation coefficient R²>0.995 indicates that the fitting effect is good. (3) Cell surface thermometry experiment The PDMS substrate side of the chip is attached to the bottom of a culture dish containing HeLa cells, ensuring that the luminescent material film is in contact with the cell culture environment (the culture medium does not affect the transmission of upconversion fluorescence). A spectral camera (1024×1024 pixels, capable of acquiring images in the 515-525nm and 535-545nm bands) equipped with a 980nm laser excitation module was used to image the cellular region, obtaining a 520nm band grayscale image (I). 520 _img) and 540nm band grayscale image (I 540 (See _img) Figure 2 and Figure 3 After denoising the two images, the grayscale ratio GR=G for each pixel is calculated. 520 / G 540 Substituting GR into the calibration equation, the temperature value of the corresponding pixel is obtained by inversion. By using pseudo-color rendering, temperature values ​​are mapped to colors (e.g., 37℃ is green, 40℃ is yellow, and 42℃ is red) to generate a temperature field distribution map of the HeLa cell surface (see [link]). Figure 4 This allows for clear observation that the temperature in metabolically active areas of cells is 1-2°C higher than the surrounding environment, enabling precise temperature measurement at the cell level. Example 2: Temperature gradient temperature measurement chip for electronic devices based on downconversion luminescent material film. (1) Chip fabrication Preparation of luminescent material film: Y2O3:Eu 3+Down-conversion phosphor (particle size 1μm) is mixed with silicone resin at a mass ratio of 1:10 to form a fluorescent paste. The paste is then screen-printed onto the surface of a silicon substrate (size 20mm×20mm, thickness 300μm) to a thickness of 5μm. The paste is then cured at 150℃ for 1 hour to form a down-conversion luminescent material film.

[0009] (2) Temperature calibration The chip was placed on a temperature control platform, and a 365nm ultraviolet LED was selected as the excitation source (power 100mW). The emission spectrum in the range of -40℃ to 125℃ was collected using a spectrometer (this temperature range covers the operating temperature of common electronic devices). Select Eu 3+ Two characteristic emission peaks: 590nm ( 5 D0→ 7 F1 transition) and 612nm ( 5 D0→ 7 (F2 transition), calculate the fluorescence intensity ratio FIR=I at different temperatures. 590 / I 612 The calibration curve was obtained by fitting: T = c×FIR + d (c≈1200, d≈-200, R²>0.99). (3) Temperature measurement experiment of electronic devices The chip was attached to the surface of the CPU in operation, and images of the CPU surface in the 590nm and 612nm bands were acquired using a spectral camera. By calculating the grayscale ratio and inverting the temperature, a temperature field image of the CPU surface is generated. It can be clearly observed that the temperature in the CPU core area is as high as 95℃, while the temperature in the edge area is about 60℃. The temperature gradient distribution on the CPU surface is accurately obtained, providing data support for the thermal design optimization of electronic devices.

[0010] The specific embodiments of the present invention have been described in detail above. It should be noted that the present invention is not limited to the specific embodiments described above. Various modifications or alterations can be made by those skilled in the art without departing from the scope of protection defined by the claims, and all such modifications or alterations fall within the scope of the present invention.

Claims

1. A measurement method for a microscale temperature field sensing chip based on frequency conversion luminescence technology, characterized in that, Step 1: Select an upconversion or downconversion luminescent material, disperse it in deionized water, coat it on the substrate surface, dry it, and encapsulate it with a protective film to obtain a temperature sensing chip; Step 2: Place the film in a temperature-controlled environment and collect the emission spectrum of the film at different temperatures. Select two characteristic emission peaks with obvious temperature response, denoted as peak A and peak B, and calculate the fluorescence intensity ratio (FIR) of peak A to peak B at each temperature. Step 3: Plot temperature on the x-axis and fluorescence intensity ratio on the y-axis, and obtain the functional relationship between fluorescence intensity ratio and temperature through data fitting, i.e., the temperature calibration curve; Step 4: Attach one side of the luminescent material film layer of the temperature sensing chip to the surface to be measured, ensuring full contact between the film layer and the surface. Acquire images of the corresponding wavelength bands of characteristic emission peaks A and B, and obtain the grayscale image I of peak A. A grayscale images of img and peak B (I) B The image shows two grayscale images processed pixel-by-pixel, with the grayscale ratio GR calculated for each pixel: GR = G. A / G B or G B / G A G A For I A The grayscale value of that pixel in the image, G B For I B The grayscale value of that pixel in the img image; Step 6: Substitute the grayscale ratio of each pixel into the temperature calibration curve established in Step 3, and invert the temperature value corresponding to that pixel. Through image rendering technology, map the temperature data into the corresponding color information to generate a visualized temperature field image that reflects the temperature distribution of the measured area, thereby intuitively presenting the spatial distribution of temperature.

2. The method according to claim 1, characterized in that, The upconversion luminescent materials are rare earth ion-doped fluorides, vanadates, and borates.

3. The method according to claim 2, characterized in that, The rare earth ions are Er, Tm, and Ho.

4. The method according to claim 1, characterized in that, The fluoride is NaYF4, the vanadate is NaGF4, and the borate is LaVO4.

5. The method according to claim 1, characterized in that, The downconversion luminescent material is a rare-earth-doped oxide or a quantum dot material.

6. The method according to claim 1, characterized in that, The rare earth-doped oxide is Y₂O₃:Eu 3+ Gd2O3:Tb 3+ The quantum dot materials are CdSe / ZnS quantum dots and PbS quantum dots.

7. The method according to claim 1, characterized in that, The substrate is a silicon wafer, a glass sheet, polydimethylsiloxane (PDMS), or polyimide (PI).

8. The method according to claim 1, characterized in that, The protective film is made of polymethyl methacrylate (PMMA) or silicon dioxide film.

9. The method according to claim 1, characterized in that, The ratio of bottom fluorescence intensity to FIR = I A / I B Or I B / I A .

10. The method according to claim 1, characterized in that, The emitted light is collected using a spectrometer. The upconversion layer uses a near-infrared laser, and the downconversion layer uses an ultraviolet lamp or a visible laser.

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