Preparation method of wide-temperature-range near-zero-temperature-coefficient thin film pressure sensor

Abstract

This invention discloses a method for fabricating a near-zero temperature coefficient thin-film pressure sensor with a wide temperature range. The purpose of this invention is to address the common problem of insufficient environmental adaptability in existing flexible thin-film sensors, particularly the significant performance degradation under extreme temperature conditions. This invention proposes a wide-temperature-range intrinsically self-compensating flexible pressure sensor based on a PVDF / CFT / Cu composite sensing material thin film. This sensor achieves a near-zero temperature coefficient of resistance for the composite material by synergistically introducing carbon fiber tubes with negative temperature coefficients and copper nanoparticles with positive temperature coefficients into the flexible PVDF matrix and dynamically controlling their ratio, thereby constructing a temperature self-compensation mechanism at the material level. This invention provides an effective material solution for developing next-generation high-reliability, wide-temperature-range adaptive flexible sensing systems.

Description

Technical Field

[0001] This invention relates to a method for fabricating a thin-film pressure sensor. Background Technology

[0002] With the rapid development of science, technology, medicine, and artificial intelligence, the requirements for parameter acquisition and status monitoring in the production process are increasing, which places higher demands on the measurement accuracy and range of sensors. Traditional thin-film sensors are mostly based on rigid materials such as silicon and metals, relying on the piezoresistive or piezoelectric effect to achieve sensing functions, and have good measurement accuracy and operational stability. However, these sensors are limited by the inherent rigidity and brittleness of the materials, making it difficult to adapt to special needs such as complex environments, miniaturized structures, and flexible production. Therefore, developing flexible thin-film sensors that can operate stably in harsh environments such as extreme temperatures has become a cutting-edge research direction of common concern in academia and industry.

[0003] Piezoresistive thin-film pressure sensors have attracted widespread attention due to their advantages such as simple structure, high sensitivity, and ease of integration. The flexible functional materials used to construct piezoresistive sensors mainly consist of conductive materials (such as metal nanomaterials and carbon-based nanomaterials) and flexible substrate materials (PEDOT, PEO, and silicone). However, most flexible substrate materials (such as hydrogels, ionogels, and some polymers) freeze and lose their flexibility at low temperatures (<0℃), resulting in a sharp decrease in low-temperature sensing performance. At high temperatures (>80℃), they soften and decompose due to oxidation, causing significant temperature drift in their intrinsic resistance, which interferes with the pressure-sensitive signal and renders the sensor ineffective. Summary of the Invention

[0004] The purpose of this invention is to address the problem that existing flexible thin-film sensors generally lack environmental adaptability, especially the significant performance degradation under extreme temperature conditions, and to provide a method for fabricating a near-zero temperature coefficient thin-film pressure sensor with a wide temperature range.

[0005] A method for fabricating a wide-temperature-range near-zero temperature coefficient thin-film pressure sensor is specifically carried out according to the following steps:

[0006] I. Preparation of PVDF / CFT / Cu composite sensing materials:

[0007] ① Grind PVDF powder, then add copper powder and grind, then add carbon fiber tubes in batches and grind to obtain a mixed powder after grinding.

[0008] ② Add the ground mixed powder to N-methylpyrrolidone, stir, remove bubbles, and obtain a uniformly dispersed composite material slurry;

[0009] ③ Coat the uniformly dispersed composite material slurry onto the polyimide film, then dry it, and then separate the film formed by the slurry from the polyimide film to obtain the PVDF / CFT / Cu composite sensitive material film.

[0010] II. Fabrication of a thin-film pressure sensor:

[0011] Excess copper foil is etched away on a polyimide substrate with copper foil on its surface using a laser etching machine, leaving interdigitated electrode copper wire pathways. Then, a PVDF / CFT / Cu composite sensing material film is pasted and covered on the interdigitated electrode copper wire pathways. Finally, polyimide tape is used to cover the polyimide substrate, forming a structure from bottom to top consisting of a polyimide substrate, interdigitated electrode copper wire pathways, composite sensing material film, and polyimide tape, resulting in a wide-temperature-range near-zero temperature coefficient thin-film pressure sensor.

[0012] Advantages of this invention:

[0013] I. This invention proposes a wide-temperature-range intrinsically self-compensating flexible pressure sensor based on a PVDF / CFT / Cu composite sensitive material thin film. The sensor achieves a near-zero temperature coefficient of resistance (TCR≈0) for the composite material by synergistically introducing carbon fiber tubes with a negative temperature coefficient (NTC) and copper nanoparticles with a positive temperature coefficient (PTC) into the flexible PVDF matrix and dynamically adjusting the ratio of the two, thereby constructing a temperature self-compensating mechanism at the material level.

[0014] II. The wide-temperature-range near-zero temperature coefficient thin-film pressure sensor prepared by this invention exhibits excellent temperature stability in a wide temperature range from -30℃ to 140℃, with an average temperature coefficient of resistance as low as 0.05% / ℃, effectively suppressing signal drift caused by temperature fluctuations; at the same time, the sensor still has a range of up to 4MPa and a fast response capability of less than 400ms even in extreme temperature environments.

[0015] Third, this invention provides an effective material solution for developing next-generation, highly reliable, wide-temperature-range adaptive flexible sensing systems. Attached Figure Description

[0016] Figure 1 SEM image of the PVDF / CFT / Cu composite sensitive material film prepared in Example 1;

[0017] Figure 2 EDS image of the PVDF / CFT / Cu composite sensitive material film prepared in Example 1;

[0018] Figure 3 Raman spectra of copper powder, carbon fiber tubes, PVDF powder, and the PVDF / CFT / Cu composite sensitive material film prepared in Example 1;

[0019] Figure 4 Fourier transform infrared spectra of copper powder, carbon fiber tubes, PVDF powder, and the PVDF / CFT / Cu composite sensitive material film prepared in Example 1;

[0020] Figure 5 The diagram shows the structural design of the interdigitated electrode copper wire path in Example 1 and the physical image of the wide-temperature-range near-zero temperature coefficient thin-film pressure sensor prepared in Example 1.

[0021] Figure 6 The images show a physical picture of the PVDF / CFT / Cu composite sensitive material film prepared in Example 1 and a thickness measurement diagram of the wide temperature range near-zero temperature coefficient thin film pressure sensor prepared in Example 1.

[0022] Figure 7 A schematic diagram illustrating the synergistic compensation mechanism for achieving zero temperature coefficient in the PVDF / CFT / Cu composite sensitive material prepared in Example 1;

[0023] Figure 8 The stability test diagram of the wide-temperature-range near-zero temperature coefficient thin-film pressure sensor prepared in Example 1 is shown in the wide-temperature-range test diagram.

[0024] Figure 9 The stability test results of the wide-temperature-range near-zero temperature coefficient thin-film pressure sensor prepared in Example 1 under thermal shock conditions are shown in the figure.

[0025] Figure 10 Dynamic response curves of the wide-temperature-range near-zero temperature coefficient thin-film pressure sensor prepared in Example 1 at different pressure endpoints;

[0026] Figure 11 Current response curves of the wide-temperature-range near-zero temperature coefficient thin-film pressure sensor prepared in Example 1 under different temperatures and loads;

[0027] Figure 12 The real-time current response curve of the wide-temperature-range near-zero temperature coefficient thin-film pressure sensor prepared in Example 1 under gradient step pressure. Detailed Implementation

[0028] Specific Implementation Method 1: This implementation method is a fabrication method for a wide-temperature-range near-zero temperature coefficient thin-film pressure sensor, specifically completed according to the following steps:

[0029] I. Preparation of PVDF / CFT / Cu composite sensing materials:

[0030] ① Grind PVDF powder, then add copper powder and grind, then add carbon fiber tubes in batches and grind to obtain a mixed powder after grinding.

[0031] ② Add the ground mixed powder to N-methylpyrrolidone, stir, remove bubbles, and obtain a uniformly dispersed composite material slurry;

[0032] ③ Coat the uniformly dispersed composite material slurry onto the polyimide film, then dry it, and then separate the film formed by the slurry from the polyimide film to obtain the PVDF / CFT / Cu composite sensitive material film.

[0033] II. Fabrication of a thin-film pressure sensor:

[0034] Excess copper foil is etched away on a polyimide substrate with copper foil on its surface using a laser etching machine, leaving interdigitated electrode copper wire pathways. Then, a PVDF / CFT / Cu composite sensing material film is pasted and covered on the interdigitated electrode copper wire pathways. Finally, polyimide tape is used to cover the polyimide substrate, forming a structure from bottom to top consisting of a polyimide substrate, interdigitated electrode copper wire pathways, composite sensing material film, and polyimide tape, resulting in a wide-temperature-range near-zero temperature coefficient thin-film pressure sensor.

[0035] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the preparation method of the carbon fiber tube described in step one ① is specifically completed according to the following steps: The collected willow catkins are washed 2 to 4 times with deionized water and anhydrous ethanol respectively, then placed in a vacuum oven for pre-carbonization at 110℃ to 120℃ for 10 to 12 hours, and then placed in a tube furnace. Under the protection of argon atmosphere, the temperature is increased to 700℃ at a rate of 10℃ / min, and then calcined at 700℃ for 2 to 4 hours to obtain the carbon fiber tube. Other steps are the same as in Specific Implementation Method One.

[0036] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that: in step 1①, the PVDF powder is ground until the particle size is <200μm, then copper powder is added and ground for 15min~20min, and then carbon fiber tubes are added in 3~5 portions and ground for 15min~20min each time to obtain the ground mixed powder. Other steps are the same as in Specific Implementation Method 1 or 2.

[0037] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the mass ratio of PVDF powder, carbon fiber tube, and copper powder in the mixed powder described in step one ① is 10:(0.1~0.3):(0.8~1.8). The other steps are the same as in Specific Implementation Methods One to Three.

[0038] Specific Implementation Method Five: The difference between this implementation method and Specific Implementation Methods One to Four is that the stirring method described in step one ② is as follows: first, stir at 180 rpm for 2 hours, then stir at 200 rpm for 3 hours, and finally stir at 280 rpm for 2 hours. The other steps are the same as in Specific Implementation Methods One to Four.

[0039] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: the mass ratio of the mixed powder to the volume of N-methylpyrrolidone in step one (②) is 1 g: 10 mL; the defoaming in step one (②) is performed under a vacuum of -0.1 MPa for 4 to 6 hours. Other steps are the same as in Specific Implementation Methods One to Five.

[0040] Specific Implementation Method Seven: The difference between this implementation method and Specific Implementation Methods One to Six is ​​that the scraping speed in step 1③ is 0.8cm / s to 1cm / s, and the scraping thickness is 1mm to 2mm. The other steps are the same as in Specific Implementation Methods One to Six.

[0041] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that: the thickness of the polyimide film mentioned in step 1③ is 100μm; the drying temperature mentioned in step 1③ is 80℃~100℃, and the drying time is 20h~24h. Other steps are the same as in Specific Implementation Methods One to Seven.

[0042] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that: the thickness of the copper-clad polyimide substrate in step two is 60 μm, the thickness of the PVDF / CFT / Cu composite sensitive material film is 60 μm to 65 μm, and the thickness of the polyimide tape is 50 μm. Other steps are the same as in Specific Implementation Methods One to Eight.

[0043] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in the following ways: the diameter of the interdigitated electrode copper wire path in step two is 20 mm; the diameter of the PVDF / CFT / Cu composite sensitive material film is 20 mm; the polyimide substrate includes a circular working area and a strip-shaped lead-out area, the diameter of the circular working area is 26 mm, and the interdigitated electrode copper wire path is disposed within the circular working area; the diameter of the polyimide tape is 26 mm. Other steps are the same as in Specific Implementation Methods One to Nine.

[0044] The beneficial effects of the present invention are verified using the following embodiments:

[0045] Example 1: A method for fabricating a near-zero temperature coefficient thin-film pressure sensor over a wide temperature range, specifically comprising the following steps:

[0046] I. Preparation of PVDF / CFT / Cu composite sensing materials:

[0047] ① The collected willow catkins were washed three times with deionized water and anhydrous ethanol respectively. Then they were placed in a vacuum oven and pre-carbonized at 120℃ for 12 hours. Then they were placed in a tube furnace and heated to 700℃ at a rate of 10℃ / min under argon atmosphere protection. They were then calcined at 700℃ for 3 hours to obtain carbon fiber tubes (CFT).

[0048] ② Grind 2g of PVDF powder for 20min until the particle size is <200μm, then add 0.24g of copper powder and grind for 15min, then add a total of 0.04g of carbon fiber tube in 4 portions and grind for 20min each time to obtain the ground mixed powder.

[0049] ③ Add 2g of the ground mixed powder to 10mL of N-methylpyrrolidone, grind until a paste is formed, then add another 10mL of N-methylpyrrolidone, stir, and defoam under a vacuum of -0.1MPa for 5 hours to obtain a uniformly dispersed composite material slurry;

[0050] The stirring method described in step 1③ is as follows: first stir at 180 rpm for 2 hours, then stir at 200 rpm for 3 hours, and finally stir at 280 rpm for 2 hours.

[0051] ④ The uniformly dispersed composite material slurry is coated onto a polyimide film and then dried at 80°C for 24 hours. The film formed by the slurry is then separated from the polyimide film to obtain a PVDF / CFT / Cu composite sensitive material film.

[0052] The thickness of the polyimide film mentioned in step 1, section 4 is 100 μm;

[0053] The scraping speed described in step 1, ④ is 0.8 cm / s, and the scraping thickness is approximately 2 mm;

[0054] II. Fabrication of a thin-film pressure sensor:

[0055] Excess copper foil is etched away on a polyimide substrate with copper foil on its surface using a laser etching machine, leaving interdigitated electrode copper wire pathways. Then, a PVDF / CFT / Cu composite sensing material film is placed on the interdigitated electrode copper wire pathways, and polyimide tape is used to adhere and cover the polyimide substrate, forming a structure from bottom to top consisting of a polyimide substrate, interdigitated electrode copper wire pathways, composite sensing material film, and polyimide tape, resulting in a wide-temperature-range near-zero temperature coefficient thin-film pressure sensor (PCCU).

[0056] In step two, the thickness of the copper-clad polyimide substrate is approximately 60 μm, the thickness of the PVDF / CFT / Cu composite sensitive material film is 60 μm, and the thickness of the polyimide tape is 50 μm.

[0057] In step two, the diameter of the interdigitated electrode copper wire path is 20 mm; the diameter of the PVDF / CFT / Cu composite sensitive material film is 20 mm; the polyimide substrate includes a circular working area and a strip-shaped lead-out area, the diameter of the circular working area is 26 mm, and the interdigitated electrode copper wire path is set in the circular working area; the diameter of the polyimide tape is 26 mm.

[0058] Example 1 prepared a PVDF / CFT / Cu composite sensitive material film, whose unique microstructure is the fundamental reason for achieving high sensitivity piezoresistive effect and zero temperature coefficient characteristics.

[0059] The morphology of the thin film was characterized by scanning electron microscopy (SEM), such as... Figure 1 As shown;

[0060] Figure 1 SEM image of the PVDF / CFT / Cu composite sensitive material film prepared in Example 1;

[0061] Figure 1 The left-middle image shows a cross-sectional SEM image of the composite sensing material, in which CFT and Cu interweave to form a three-dimensional, porous, interwoven mesh framework structure within the PVDF. This conductive network framework structure provides the sensor with excellent compressibility and piezoresistive effect. When external pressure is applied, this framework structure can undergo significant and reversible deformation, which in turn causes the internal conductive network to be compressed, enhancing the conductivity of the sensing material and reducing its resistance, thus achieving the piezoresistive characteristics. Figure 1 The middle and right images show the surface morphology of the composite sensing material and its magnified SEM images, respectively. Carbon fiber tubes are uniformly coated and distributed within the PVDF matrix in a three-dimensional network, while nano-Cu particles are uniformly dispersed within the PVDF and CFT networks. The introduction of Cu particles serves two purposes: firstly, it enhances the overall conductivity as an auxiliary conductive phase; secondly, the inherent positive temperature coefficient effect of Cu compensates for and cancels out the inherent negative temperature coefficient effect of CFT, thus enabling the entire composite sensing film to exhibit near-zero temperature coefficient stability over a wide temperature range. The magnified images reveal uniform dispersion of the materials, no obvious agglomeration, and a uniformly distributed conductive network within the substrate material. Figure 1 As shown in the middle right figure.

[0062] Figure 2 EDS image of the PVDF / CFT / Cu composite sensitive material film prepared in Example 1;

[0063] from Figure 2 The element distribution diagram shows that the elements are evenly distributed, which also proves that the conductive network inside the PVDF is evenly distributed, and the metal particles are also evenly distributed in the conductive network, forming a stable near-zero temperature coefficient piezoresistive conductive network.

[0064] Figure 3 Raman spectra of copper powder, carbon fiber tubes, PVDF powder, and the PVDF / CFT / Cu composite sensitive material film prepared in Example 1;

[0065] from Figure 3 It can be seen that the characteristic Raman peak of PVDF is located at approximately 795 cm. -1 and 840 cm -1 The locations at these points correspond to the α and β phases of PVDF, respectively. The characteristic Raman peak of carbon fiber tube (CFT) is located at approximately 1350 cm⁻¹. -1 (D peak) and approximately 1580 cm -1 At the (G peak), the intensity ratio of the D peak to the G peak characterizes the degree of disorder in carbon materials. Copper powder (Cu), due to its metallic properties, does not exhibit obvious characteristic vibrational peaks in Raman spectroscopy. The spectrum of the PVDF / CFT / Cu composite sensitive material (PCCU) completely inherits the D peak (~1350 cm⁻¹) of CFT. -1 ) and G peak (~1580 cm) -1 ), confirming CFT's sp 2 The carbon skeleton was not damaged during the blending and drying process.

[0066] Figure 4 Fourier transform infrared spectra of copper powder, carbon fiber tubes, PVDF powder, and the PVDF / CFT / Cu composite sensitive material film prepared in Example 1;

[0067] from Figure 4 The characteristic signals of PVDF (characteristic peaks corresponding to its molecular chain vibration), Cu (metal characteristic absorption region), and CFT (carbon material characteristic wavenumber band) indicate that PVDF, Cu, and CFT were successfully composited in PCCU film through NMP blending and drying processes, and no component loss occurred due to solvent evaporation (NMP) or drying process.

[0068] Figure 5 The diagram shows the structural design of the interdigitated electrode copper wire path in Example 1 and the physical image of the wide-temperature-range near-zero temperature coefficient thin-film pressure sensor prepared in Example 1.

[0069] Figure 5The electrodes at points A and b are based on a 20mm diameter circle, with the radius of each interdigitated ring increasing by 0.5mm. The radius of the first ring is 2mm, and the radius of the outermost ring is 10mm. This structure can increase the contact area between the PVDF / CFT / Cu composite sensitive material film and the electrode, and improve the signal response sensitivity under pressure load. At the same time, the overall size of the sensor (lead length at point a is 150.00mm, pin width at point c is 5.00mm) takes into account both ease of installation and signal transmission stability. Figure 5 B is a physical diagram of the copper wire path of the interdigitated electrode of the sensor; Figure 5 C is a physical image of the finished sensor after encapsulating a PVDF / CFT / Cu composite sensitive material film.

[0070] Figure 6 The images show a physical picture of the PVDF / CFT / Cu composite sensitive material film prepared in Example 1 and a thickness measurement diagram of the wide temperature range near-zero temperature coefficient thin film pressure sensor prepared in Example 1.

[0071] Figure 6 a is a sample of PVDF / CFT / Cu composite sensitive material film (PCCU composite film); Figure 6 b shows the thickness of the PCCU composite film measured using a thickness gauge, which indicates a thickness of 0.063 mm (i.e., 63 μm). Figure 6 c shows the thickness of the wide-temperature-range near-zero temperature coefficient thin-film pressure sensor prepared in Example 1, with a total thickness of 0.176 mm.

[0072] Figure 7 A schematic diagram illustrating the synergistic compensation mechanism for achieving zero temperature coefficient in the PVDF / CFT / Cu composite sensitive material prepared in Example 1;

[0073] Figure 7 The core mechanism by which composite thin films achieve zero temperature coefficient is explained. In the conductive network composed of CFTs, ​​electrons are transported between adjacent CFTs or CFT segments through "hopping" or "tunneling" mechanisms. Increased temperature provides electrons with more energy, making it easier for them to overcome the potential barrier, thereby enhancing the overall conductivity of the network and reducing resistance. Therefore, the CFT network exhibits a negative temperature coefficient characteristic. For metallic Cu, increased temperature causes intensified atomic thermal vibrations, enhancing the scattering of free electron flow, thus leading to increased resistance. By precisely controlling the ratio, dispersion state, and three-dimensional network structure of CFTs and Cu in the composite material, the aforementioned opposing resistance-temperature trends are macroscopically canceled out, thereby achieving a stable state with zero temperature coefficient where the resistance of the entire sensitive thin film remains essentially unchanged across a wide temperature range.

[0074] The wide-temperature-range near-zero temperature coefficient thin-film pressure sensor prepared in Example 1 was connected to an electrochemical workstation with an operating voltage of 1V and a sampling frequency of 0.1Hz. It was then placed in a high-low temperature test oven, and a heating curve was set for the oven. During this process, the sensor's resistance was measured. Figure 8 As shown;

[0075] Figure 8 The stability test diagram of the wide-temperature-range near-zero temperature coefficient thin-film pressure sensor prepared in Example 1 is shown in the wide-temperature-range test diagram.

[0076] like Figure 8 The near-zero temperature coefficient thin-film pressure sensor prepared in Example 1 exhibits highly stable initial resistance with no significant temperature drift within a temperature range of 90°C to 140°C. Calculations show its temperature coefficient of resistance (TCR) is as low as 0.05% / °C. This data fully verifies the near-zero temperature coefficient characteristic achieved by the mutual compensation of the negative temperature coefficient of CFT and the positive temperature coefficient of Cu / polymer in the material system described in this invention, indicating that the sensitive material thin film still possesses excellent signal stability under high-temperature environments.

[0077] The wide-temperature-range near-zero temperature coefficient thin-film pressure sensor prepared in Example 1 was connected to an electrochemical workstation with an operating voltage of 1V and a sampling frequency of 0.1Hz. It was then placed in a high-low temperature test oven and rapidly heated from room temperature to 90°C to test the sensor's thermal shock stability. (See attached image.) Figure 9 As shown;

[0078] Figure 9 The stability test results of the wide-temperature-range near-zero temperature coefficient thin-film pressure sensor prepared in Example 1 under thermal shock conditions are shown in the figure.

[0079] from Figure 9 It can be seen that the wide-temperature-range near-zero temperature coefficient thin-film pressure sensor prepared in Example 1 exhibited stable transient resistance response without significant jumps during the continuous step temperature increase from 25℃ to 90℃. The resistance change rate (ΔR / R0) remained below ±0.3% throughout the process, demonstrating excellent dynamic thermal stability. This indicates that the sensitive material thin film can maintain stable electrical properties even under rapid temperature fluctuations in actual operating conditions, possessing good thermal shock resistance.

[0080] Connect the sensor to the electrochemical workstation, set the operating voltage to 1V and the sampling frequency to 0.1Hz, then fix it to the surface of the universal testing press, set the cyclic mechanics program, and perform the measurement. (See attached image.) Figure 10 As shown;

[0081] Figure 10Dynamic response curves of the wide-temperature-range near-zero temperature coefficient thin-film pressure sensor prepared in Example 1 at different pressure endpoints;

[0082] Depend on Figure 10 It is evident that under the same dynamic cyclic loading condition (100 N / s), the sensor's response curves to different pressure endpoints of 80 kPa, 160 kPa, 240 kPa, and 320 kPa all exhibit regular and stable periodic fluctuations. The steady-state current response values ​​corresponding to each pressure endpoint were extracted, and linear fitting was performed between them and the pressure. The results show that the sensor's dynamic pressure sensitivity within this range is approximately 1.05 μA / kPa, with a linear correlation coefficient R0. 2 >0.98. This data fully verifies that the sensor has excellent consistency, linearity, and discrimination in its dynamic response under different pressures, and can accurately respond to and distinguish dynamic loads of different magnitudes.

[0083] The wide-temperature-range near-zero temperature coefficient thin-film pressure sensor prepared in Example 1 was connected to an electrochemical workstation with a working voltage of 1V and a sampling frequency of 0.1Hz. It was then placed in a high-low temperature testing oven, and the oven temperature was increased from -30℃ to 140℃. Three sets of weights of different weights (50g, 100g, and 200g) were used. During this process, the resistance of the sensor was measured. (See attached diagram). Figure 11 As shown;

[0084] Figure 11 Current response curves of the wide-temperature-range near-zero temperature coefficient thin-film pressure sensor prepared in Example 1 under different temperatures and loads;

[0085] Figure 11 The near-zero temperature coefficient thin-film pressure sensor (PCCU thin-film sensor) prepared in Example 1 is demonstrated. Within the temperature range of -30°C to 140°C, the current output fluctuation of the sensor under loads of 50g, 100g, and 200g is less than ±4%. The sensor exhibits small current response fluctuation and excellent consistency across the entire temperature range and under different loads, demonstrating its stable sensing performance with zero temperature coefficient.

[0086] The wide-temperature-range near-zero temperature coefficient thin-film pressure sensor prepared in Example 1 was connected to an electrochemical workstation with an operating voltage of 1V and a sampling frequency of 0.1Hz. It was then fixed to the surface of a universal testing press, and a gradient mechanics program was set to measure the sensor resistance. (See attached diagram.) Figure 12 As shown;

[0087] Figure 12 The real-time current response curve of the wide-temperature-range near-zero temperature coefficient thin-film pressure sensor prepared in Example 1 under gradient step pressure;

[0088] from Figure 12 In the test, the sensor was subjected to nine progressively increasing pressures, ranging from 635 kPa to 5.71 MPa, and it still responded even after increasing the load above 5 MPa. The sensor's current signal showed a stable stepwise increase with increasing pressure, and the signals at each pressure plateau were clearly distinguishable.

Claims

1. A method for fabricating a wide-temperature-range near-zero temperature coefficient thin-film pressure sensor, characterized in that... The preparation method is specifically carried out according to the following steps: I. Preparation of PVDF / CFT / Cu composite sensing materials: ① Grind PVDF powder, then add copper powder and grind, then add carbon fiber tubes in batches and grind to obtain a mixed powder after grinding. ② Add the ground mixed powder to N-methylpyrrolidone, stir, remove bubbles, and obtain a uniformly dispersed composite material slurry; ③ Coat the uniformly dispersed composite material slurry onto the polyimide film, then dry it, and then separate the film formed by the slurry from the polyimide film to obtain the PVDF / CFT / Cu composite sensitive material film. II. Fabrication of a thin-film pressure sensor: Excess copper foil is etched away on a polyimide substrate with copper foil on its surface using a laser etching machine, leaving interdigitated electrode copper wire pathways. Then, a PVDF / CFT / Cu composite sensing material film is placed on the interdigitated electrode copper wire pathways. Finally, polyimide tape is used to adhere and cover the polyimide substrate, forming a structure from bottom to top consisting of a polyimide substrate, interdigitated electrode copper wire pathways, composite sensing material film, and polyimide tape, resulting in a wide-temperature-range near-zero temperature coefficient thin-film pressure sensor.

2. The method for fabricating a wide-temperature-range near-zero temperature coefficient thin-film pressure sensor according to claim 1, characterized in that... The preparation method of carbon fiber tubes described in step 1① is carried out according to the following steps: the collected willow catkins are washed 2 to 4 times with deionized water and anhydrous ethanol respectively, then placed in a vacuum oven for pre-carbonization at 110℃ to 120℃ for 10h to 12h, then placed in a tube furnace and heated to 700℃ at a temperature increase rate of 10℃ / min under argon atmosphere protection, and calcined at 700℃ for 2h to 4h to obtain carbon fiber tubes.

3. The method for fabricating a wide-temperature-range near-zero temperature coefficient thin-film pressure sensor according to claim 1, characterized in that... In step 1①, PVDF powder is ground until the particle size is <200μm, then copper powder is added and ground for 15min~20min, and then carbon fiber tube is added in 3~5 times and ground for 15min~20min to obtain the ground mixed powder.

4. The method for fabricating a wide-temperature-range near-zero temperature coefficient thin-film pressure sensor according to claim 1, characterized in that... In step 1①, the mass ratio of PVDF powder, carbon fiber tube, and copper powder in the mixed powder is 10:(0.1~0.3):(0.8~1.8).

5. The method for fabricating a wide-temperature-range near-zero temperature coefficient thin-film pressure sensor according to claim 1, characterized in that... The stirring method described in step 1② is as follows: first stir at 180 rpm for 2 hours, then stir at 200 rpm for 3 hours, and finally stir at 280 rpm for 2 hours.

6. The method for fabricating a wide-temperature-range near-zero temperature coefficient thin-film pressure sensor according to claim 1, characterized in that... The mass ratio of the mixed powder to the volume of N-methylpyrrolidone in steps 1 and 2 is 1 g: 10 mL; the defoaming in steps 1 and 2 is carried out under a vacuum of -0.1 MPa for 4 to 6 hours.

7. The method for fabricating a wide-temperature-range near-zero temperature coefficient thin-film pressure sensor according to claim 1, characterized in that... The scraping speed described in step 1, ③ is 0.8cm / s to 1cm / s, and the scraping thickness is 2mm.

8. The method for fabricating a wide-temperature-range near-zero temperature coefficient thin-film pressure sensor according to claim 1, characterized in that... The thickness of the polyimide film mentioned in step 1 ③ is 100 μm; the drying temperature mentioned in step 1 ③ is 80℃~100℃, and the drying time is 20h~24h.

9. The method for fabricating a wide-temperature-range near-zero temperature coefficient thin-film pressure sensor according to claim 1, characterized in that... In step two, the thickness of the copper-clad polyimide substrate is 60 μm, the thickness of the PVDF / CFT / Cu composite sensitive material film is 60 μm to 65 μm, and the thickness of the polyimide tape is 50 μm.

10. The method for fabricating a wide-temperature-range near-zero temperature coefficient thin-film pressure sensor according to claim 1, characterized in that... In step two, the diameter of the interdigitated electrode copper wire path is 20 mm; the diameter of the PVDF / CFT / Cu composite sensitive material film is 20 mm; the polyimide substrate includes a circular working area and a strip-shaped lead-out area, the diameter of the circular working area is 26 mm, and the interdigitated electrode copper wire path is set in the circular working area; the diameter of the polyimide tape is 26 mm.

Images