Flexible Temperature Sensor Based on Multicomponent Vanadium Dioxide Thin Film and Preparation Method Thereof

Abstract

The present invention relates to the field of flexible temperature sensing technology, specifically a flexible temperature sensor based on a multi-component vanadium dioxide thin film and a preparation method thereof, including a PMMA substrate, a metal electrode disposed on the PMMA substrate, a multi-component VO2 thin film covering the metal electrode, and a substrate covering the multi-component VO2 thin film; the metal electrode is connected through a wire to realize signal input / output, the multi-component VO2 thin film is a VO2 thin film doped with elements W and Ti in a specific ratio, and the substrate is fluorophlogopite or mica. Compared with the prior art, the present invention can realize the preparation of a vanadium dioxide thin film flexible temperature sensor without expensive equipment and a strict vacuum environment, with low cost; the preparation process is simple and easy to implement, and has good mechanical properties, good anti-bending stability, light self-weight, and good bending stability.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible temperature sensing, and particularly to a flexible temperature sensor based on a multi-component vanadium dioxide thin film and a preparation method thereof. Background Art

[0002] Temperature sensors have extremely wide applications in industry and life, such as diagnosing human body temperature, measuring the heat generation of electronic devices, and so on. In recent years, flexible temperature sensors have been extensively studied due to their wearable characteristics and the ability to measure the surface temperature of curved objects in real time. Traditional flexible temperature sensors are mostly prepared from metals, carbon-based materials, metal oxides or polymer materials. Affected by the inherent characteristics of the selected materials, traditional flexible temperature sensors have disadvantages such as high cost, poor sensitivity, and poor mechanical properties.

[0003] Since the metal-insulator phase transition temperature of the vanadium dioxide thin film is near room temperature and the resistance changes greatly during the phase transition, it has broad application prospects. Therefore, studying the phase transition mechanism of vanadium dioxide and regulating its phase transition performance are particularly important for realizing the application of vanadium dioxide thin films. At present, some researchers have prepared flexible temperature sensors using vanadium dioxide thin films as functional materials through the study of the phase change properties of vanadium dioxide thin films, and realized their application in human physiological signal monitoring.

[0004] In existing flexible temperature sensors using vanadium dioxide thin films as functional materials, the preparation of the vanadium dioxide thin film usually involves methods such as graphene-based transfer, wet etching, or using CNT and SiN nanotubes as high-temperature resistant substrates and directly growing VO2 thin films on them. Among them, both graphene-based transfer and wet etching use etching solutions for etching. Since the etching solutions used are usually toxic and harmful substances, they cause great harm to the human body and the environment, and the etching time is long, and the etching process is difficult to control, increasing the preparation difficulty. Directly growing VO2 thin films on CNT and SiN nanotubes avoids the impact of toxic and harmful substances on human health, but has high requirements for the environment and equipment, and requires expensive equipment to prepare VO2 thin films in a high-vacuum and high-cleanliness environment, increasing the preparation cost. Summary of the Invention

[0005] The purpose of the present invention is to provide a flexible temperature sensor based on a multi-component vanadium dioxide thin film and a preparation method thereof, so as to solve the problems of high preparation cost, high operation complexity, poor mechanical properties, etc. existing in existing flexible sensors.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A flexible temperature sensor based on a multi-component vanadium dioxide thin film, comprising a PMMA substrate, a metal electrode disposed on the PMMA substrate, a multi-component VO2 thin film covering the metal electrode, and a substrate covering the multi-component VO2 thin film; the metal electrode is connected through a wire to achieve signal input / output, the multi-component VO2 thin film is a VO2 thin film doped with elements W and Ti, and the substrate is fluorophlogopite or mica.

[0008] Further, the metal electrode deposited on the flexible substrate is a gold electrode, and a silver wire is led out from the gold electrode through silver paste or silver paint as a wire.

[0009] The above flexible temperature sensor based on a multi-component vanadium dioxide thin film and its preparation method include the following steps:

[0010] Step 1, prepare a multi-component VO2 thin film on a fluorophlogopite or mica substrate, and prepare a metal electrode on a PMMA substrate;

[0011] Preparing a multi-component VO2 thin film on a fluorophlogopite or mica substrate includes the following sub-steps:

[0012] a1. Treat the fluorophlogopite or mica substrate to keep it clean and flat;

[0013] a2. Prepare V, W, Ti metal precursor solutions by the polymer assisted deposition (PAD) method, and mix them according to the mass ratio V:W:Ti = 0.8 - 0.95:0.015 - 0.03:0.05 - 0.20 to obtain a mixed solution; wherein, the concentrations of the V, W, Ti metal precursor solutions are 20000 - 30000 mg / L, 5000 - 15000 mg / L, 10 - 100 mg / L respectively;

[0014] a3. Uniformly coat the prepared precursor solution on the fluorophlogopite or mica substrate obtained in step a1, and prepare a multi-component VO2 thin film by the polymer assisted deposition method;

[0015] Preparing a metal electrode on a PMMA substrate includes the following sub-steps,

[0016] b1. Use laser cutting to prepare a PI mask;

[0017] b2. Attach the PI mask to the upper surface of the PMMA substrate, and use magnetron sputtering to fabricate a metal electrode on the upper surface of the PMMA substrate;

[0018] Step 2, align and attach the multi-component VO2 thin film to the side of the PMMA substrate with the metal electrode;

[0019] Step 3: Immerse the structure obtained in Step 2 in deionized water and thin the substrate.

[0020] Step 4: Lead out silver wires from the metal electrodes through silver paste or silver paint, and thus a flexible temperature sensor based on a multi-component vanadium dioxide thin film is fabricated.

[0021] Furthermore, before thinning, the thickness of the fluorophlogopite or mica substrate is 0.2 mm, and the size is 1*1 cm. After thinning, the thickness is 4 - 8 μm, and the size is 1*1 cm.

[0022] Furthermore, in the compound formed by the V, W, and Ti metal precursor solutions, the doping mass ratio of the three metals is V:W:Ti = 0.899:0.021:0.08.

[0023] A flexible temperature sensor based on a multi-component vanadium dioxide thin film provided by the present invention dopes W and Ti in a specific ratio to change the phase transition process of the VO2 thin film, thereby changing the electrical properties of the VO2 thin film, making its phase transition temperature near the human body temperature, and having no thermal hysteresis in the thin film, so as to achieve high sensitivity and fast response speed.

[0024] Beneficial effects: The flexible temperature sensor based on a multi-component vanadium dioxide thin film provided by the present invention can fabricate the vanadium dioxide thin film flexible temperature sensor without expensive equipment and a strict vacuum environment, with low cost; the preparation process is simple and easy to implement, and has good mechanical properties and good anti-bending stability; through the PMMA substrate and the thinned mica substrate, it has the advantages of light self-weight and good bending stability. This sensor can be closely attached to the skin on the body, does not affect human activities, has a sensitivity of 5.72% / K near the human body temperature, a fast response speed, and can be monitored in real time. Description of the Drawings

[0025] Figure 1 It is a schematic structural diagram of the flexible temperature sensor of the multi-component vanadium dioxide thin film of the present invention;

[0026] Figure 2 It is a schematic preparation flow diagram of the flexible temperature sensor of the multi-component vanadium dioxide thin film of the present invention;

[0027] Figure 3 It is a display of the flexible temperature sensor of the multi-component vanadium dioxide thin film of the present invention attached to the human body; where (a) is a top view of the attachment to the arm; (b) is a front view of the arm, (c) is the back of the hand; (d) is a schematic diagram of the forehead;

[0028] Figure 4 It is a schematic diagram of the flexible temperature sensor of the multi-component vanadium dioxide thin film of the present invention in a bent state;

[0029] Figure 5The resistance-temperature curve and dlnR / dT-T relationship curve of Sample 1;

[0030] Figure 6 The resistance-temperature curve and dlnR / dT-T relationship curve of Sample 2;

[0031] Figure 7 The resistance-temperature curve and dlnR / dT-T relationship curve of Sample 3;

[0032] Figure 8 The heating and cooling TCR value-temperature curves of Samples 1, 2, and 3;

[0033] Figure 9 The resistance change of Sample 1 at different bending radii;

[0034] Figure 10 The resistance-temperature curve of Sample 1 near human body temperature;

[0035] Figure 11 The real-time resistance response curve of Sample 1 to the human skin surface;

[0036] Reference numerals: 1, PMMA substrate; 2, gold electrode; 3, thinned fluoro-phlogopite or mica; 4, multi-component VO2 thin film; 5, silver wire. Detailed implementation mode

[0037] As Figure 1 shown, the flexible temperature sensor based on the multi-component vanadium dioxide thin film includes a PMMA substrate, a metal electrode disposed on the PMMA substrate, a multi-component VO2 thin film covering the metal electrode, and a substrate covering the multi-component VO2 thin film; the metal electrode is connected through a wire to realize signal input / output, the multi-component VO2 thin film is a VO2 thin film doped with elements W and Ti, and the substrate is fluoro-phlogopite or mica.

[0038] The above flexible temperature sensor based on the multi-component vanadium dioxide thin film and its preparation method, as Figure 2 shown, includes the following steps:

[0039] Step 1, prepare a multi-component VO2 thin film on a fluoro-phlogopite or mica substrate, and prepare a metal electrode on a PMMA substrate;

[0040] Preparing a multi-component VO2 thin film on a fluoro-phlogopite or mica substrate includes the following sub-steps:

[0041] a1. Treat the fluoro-phlogopite or mica substrate. In this embodiment, fluoro-phlogopite is selected as the substrate, and the impurities attached to the surface of the fluoro-phlogopite substrate are peeled off by the tape peeling method to make its surface clean and flat without obvious layered steps.

[0042] a2. Prepare V, W, and Ti metal precursor solutions using the Polymer assisted deposition (PAD) method, and mix them according to the mass ratio of V:W:Ti = 0.8 - 0.95:0.015 - 0.03:0.05 - 0.20 to obtain a mixed solution; among them, the concentrations of the V, W, and Ti metal precursor solutions are 20000 - 30000 mg / L, 5000 - 15000 mg / L, and 10 - 100 mg / L respectively;

[0043] a3. Uniformly coat the obtained mixed solution on the fluorophlogopite or mica substrate obtained in step a1, and prepare a multi-component VO2 thin film using the polymer-assisted deposition method;

[0044] Preparing a metal electrode on a PMMA substrate includes the following sub-steps,

[0045] b1. Prepare a PI mask using laser cutting;

[0046] b2. Attach the PI mask to the upper surface of the PMMA substrate, and fabricate a metal electrode on the upper surface of the PMMA substrate using magnetron sputtering;

[0047] Step 2. Align and attach the multi-component VO2 thin film to the side of the PMMA substrate with the metal electrode;

[0048] Step 3. Immerse the structure obtained in step 2 in deionized water and perform a thinning treatment on the substrate; the thickness of the fluorophlogopite or mica substrate before thinning is 0.2 mm, the size is 1 * 1 cm, and the thickness after thinning is 4 - 8 μm, and the size is 1 * 1 cm.

[0049] Step 4. Lead out silver wires from the metal electrode through silver paste or silver paint, that is, prepare a flexible temperature sensor based on a multi-component vanadium dioxide thin film.

[0050] Step 5: Measure the variable-temperature electrical properties of the flexible temperature sensor based on the multi-component vanadium dioxide thin film, and the variable-temperature range is 273K - 373K.

[0051] According to the above steps, 3 samples of flexible temperature sensors based on multi-component vanadium dioxide thin films are prepared in this embodiment, and the 3 samples are sample 1, sample 2, and sample 3 respectively.

[0052] Among them, in sample 1, the concentrations of the V, W, and Ti metal precursor solutions are 24720 mg / L, 9648 mg / L, and 36.62 mg / L respectively, and the ratio of the three metals in the compound formed by the V, W, and Ti metal precursor solutions is V:W:Ti = 0.899:0.021:0.08.

[0053] In Sample 2, the concentrations of the V, W, and Ti metal precursor solutions are 24720 mg / L, 9648 mg / L, and 36.62 mg / L, respectively. The ratio of the three metals in the compound formed from the V, W, and Ti metal precursor solutions is V:W:Ti = 0.939:0.021:0.04.

[0054] In Sample 3, the concentrations of the V, W, and Ti metal precursor solutions are 24720 mg / L, 9648 mg / L, and 36.62 mg / L, respectively. The ratio of the three metals in the compound formed from the V, W, and Ti metal precursor solutions is V:W:Ti = 0.859:0.021:0.12.

[0055] Figure 5 are the resistance-temperature curve and the dlnR / dT-T relationship curve of Sample 1, Figure 6 are the resistance-temperature curve and the dlnR / dT-T relationship curve of Sample 2, Figure 7 are the resistance-temperature curve and the dlnR / dT-T relationship curve of Sample 3. Refer to Figure 5 and Figure 6 and Figure 7 It can be seen that thermal hysteresis occurs in Sample 2, while neither Sample 1 nor Sample 3 shows thermal hysteresis. This indicates that by adjusting the doping ratio, the hysteresis effect of the VO2 thin film can be reduced to 0, making it more suitable for the practical application of temperature sensors.

[0056] Figure 8 are the heating and cooling TCR value-temperature curves of Samples 1, 2, and 3; refer to Figure 8 It can be found that the TCR values of Samples 1, 2, and 3 near human body temperature are 5.72% / K, 2.53% / K, and 3.61% / K, respectively. The TCR value of Example 1 is the largest, and Sample 1 has the highest temperature measurement sensitivity near human body temperature, and the flexible temperature sensor prepared with its doping ratio has better performance.

[0057] Samples 1, 2, and 3 are respectively experimentally verified:

[0058] Refer to Figure 3 and Figure 4 and Figure 9 It can be seen that the flexible temperature sensor based on the multi-component vanadium dioxide thin film in this example all shows good bending characteristics, can conformally adhere to the skin at different parts without curling or warping, and maintains a resistance change within 1.2% under different bending radii.

[0059] Figure 10 is the resistance-temperature curve of Sample 1 near human body temperature; refer to Figure 10 It can be seen that Sample 1 has good linearity, which can simplify the design of the backend circuit and lay a foundation for the miniaturization of flexible wearable temperature sensors.

[0060] Figure 11 The real-time response curve of the resistance of Sample 1 to the human skin surface; refer to Figure 11 It can be seen that Sample 1 can respond quickly and accurately to the human skin, and its response recovery times are 8 s and 40 s respectively.

[0061] In summary, for the flexible temperature sensor based on the multi-component vanadium dioxide thin film provided in this embodiment, the sensitive layer material is the VO2 thin film co-doped with W and Ti, which can conformally adhere to the human skin surface, the phase change temperature is close to the human skin temperature, the phase change amplitude R reaches 1097.31, the TCR value is 5.72% / K, and it has high sensitivity.

Claims

1. A flexible temperature sensor based on a multi-component vanadium dioxide thin film, characterized in that: It includes a PMMA substrate, a metal electrode disposed on the PMMA substrate, a multi-component VO2 thin film covering the metal electrode, and a substrate covering the multi-component VO2 thin film; the metal electrode is connected through a wire to achieve signal input / output, the multi-component VO2 thin film is a VO2 thin film doped with elements W and Ti, and the substrate is fluorophlogopite or mica; Its preparation process includes: Step 1, prepare a multi-component VO2 thin film on a fluorophlogopite or mica substrate, and prepare a metal electrode on the PMMA substrate; Preparing a multi-component VO2 thin film on a fluorophlogopite or mica substrate includes the following sub-steps: a1. Treat the fluorophlogopite or mica substrate to keep it clean and flat; a2. Prepare V, W, and Ti metal precursor solutions by the polymer-assisted deposition method, and mix them according to the mass ratio of V:W:Ti = 0.8~0.95:0.015~0.03:0.05~0.20 to obtain a mixed solution; among them, the concentrations of the V, W, and Ti metal precursor solutions are 20000~30000mg / L, 5000~15000mg / L, and 10~100mg / L respectively; a3. Uniformly coat the prepared precursor solution on the fluorophlogopite or mica substrate obtained in step a1, and prepare a multi-component VO2 thin film by the polymer-assisted deposition method; Preparing a metal electrode on the PMMA substrate includes the following sub-steps, b1. Prepare a PI mask by laser cutting; b2. Attach the PI mask to the upper surface of the PMMA substrate, and fabricate a metal electrode on the upper surface of the PMMA substrate by magnetron sputtering; Step 2, align and attach the multi-component VO2 thin film to the side of the PMMA substrate with the metal electrode; Step 3, immerse the structure obtained in step 2 in deionized water, and thin the substrate; Step 4, lead out a silver wire from the metal electrode through silver paste or silver paint, that is, prepare a flexible temperature sensor based on a multi-component vanadium dioxide thin film.

2. The flexible temperature sensor based on a multi-component vanadium dioxide thin film according to claim 1, characterized in that: The metal electrode disposed on the flexible substrate is a gold electrode, and a silver wire is led out from the gold electrode through silver paste or silver paint as a wire.

3. The flexible temperature sensor based on a multi-component vanadium dioxide thin film according to claim 1, characterized in that: The thickness of the fluorophlogopite or mica substrate before thinning is 0.2mm, the size is 1*1cm, and the thickness after thinning is 4~8μm, and the size is 1*1cm.

4. The flexible temperature sensor based on a multi-component vanadium dioxide thin film according to claim 1, characterized in that: In the compound made of the V, W, and Ti metal precursor solutions, the doping mass ratio of the three metals is V:W:Ti = 0.899:0.021:0.08.

Images