Flexible pressure-sensitive material based on porous carbon sponge, flexible pressure sensor and preparation method of flexible pressure-sensitive material

Abstract

The invention relates to the technical field of flexible pressure sensors, in particular to a flexible pressure-sensitive material based on porous carbon sponge, a flexible pressure sensor and a preparation method of the flexible pressure-sensitive material. According to the preparation method, cheap absorbent cotton which is easy to obtain is used as a carbon source, the carbon source is supplemented in the polymer foam carbonization process, the low-temperature graphitization process is promoted, and the 3D porous structure sensitive material with good mechanical performance and conductive performance is obtained. The flexible pressure sensor prepared from the material is excellent in performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flexible pressure sensor, in particular to a flexible pressure-sensitive material based on porous carbon sponge, a flexible pressure sensor and a preparation method thereof. BACKGROUND

[0002] Flexible pressure sensors play an increasingly important role in medical health monitoring. Developing flexible pressure-sensitive materials with fast response speed, high sensitivity, wide response range and long cycle stability has become a key research. The introduction of 3D porous structure not only makes the material have lower density, but also effectively widens the pressure response range, becoming a hot spot in the design of sensitive materials. The rich conductive network provided by the 3D porous structure presents "point-point" contact under small pressure and "face-face" contact under large pressure, and the number of conductive paths has different characteristics, which further affects the size of the resistance. This makes the pressure-sensitive sensor have good response under small pressure and large pressure. While improving the sensitivity, the pressure response range is widened.

[0003] Commercial polyurethane or melamine polymer foams are easy to obtain and have rich pore structure, which are often used as 3D porous structure sensitive layer carriers to realize the preparation of 3D porous sensitive layer by coating a conductive layer on the surface. However, this method has the problems of complex process (such as the need for pretreatment of the carrier), uneven coating of the conductive layer, and poor performance repeatability and stability. Commercial polyurethane or melamine foams can also be directly carbonized to obtain electrode materials with certain conductivity, but under the premise of maintaining mechanical properties, the conductivity of the obtained material is usually poor, and the pressure-sensitive performance is not obvious. SUMMARY

[0004] To solve the conflict between the conductivity and mechanical properties of polymer foams during carbonization and obtain a porous material with good pressure-sensitive performance, the present application proposes to use easily obtained and inexpensive absorbent cotton as a carbon source to supplement the carbon source during the carbonization of the polymer foam, promote the low-temperature graphitization process, improve the conductivity of the material while maintaining good mechanical properties, and obtain a 3D porous structure sensitive material with excellent pressure-sensitive performance. The flexible pressure-sensitive material based on porous carbon sponge uses low-cost and easily obtained raw materials, has a simple preparation method and excellent pressure-sensitive performance, and the flexible pressure sensor prepared by using the material has excellent performance.

[0005] The present application aims to provide a preparation method of a flexible pressure-sensitive material based on porous carbon sponge, which specifically comprises the following steps:

[0006] The absorbent cotton and the melamine sponge are placed in a porcelain boat, and then the porcelain boat is sent into a tube furnace for carbonization under the protection of high-purity nitrogen. After carbonization, the porcelain boat is naturally cooled to room temperature to obtain a flexible pressure-sensitive material based on porous carbon sponge.

[0007] Further, the melamine sponge is cut into small pieces, and the absorbent cotton is placed in the porcelain boat together with the small pieces of melamine sponge;

[0008] Further, the carbonization temperature is 500-650 DEG C, and the carbonization time is 1-2 h; the temperature is increased from room temperature to the carbonization temperature at a rate of 2-5 DEG C / min.

[0009] Further, the mass ratio of the melamine sponge to the absorbent cotton is 3:1-3:6.

[0010] The purpose of the present application is also to provide a preparation method of the flexible pressure sensor, which specifically comprises the following steps: cutting the flexible pressure-sensitive material into a square block, taking one of the blocks as the middle layer, placing two PET electrodes sputtered with ITO on the opposite sides of the middle layer to form a sandwich structure, and fixing the sandwich structure with adhesive tape to obtain the flexible pressure sensor.

[0011] The present application also provides a porous carbon sponge-based flexible pressure-sensitive material and a flexible pressure sensor obtained by the above preparation method.

[0012] Compared with the prior art, the present application has the following beneficial effects:

[0013] (1) Low-temperature graphitization is realized, the electrical conductivity is improved at a lower carbonization temperature, and the mechanical properties of the material are ensured;

[0014] (2) The raw materials used in the present application are cheap and easy to obtain, the preparation method is simple, and the flexible pressure-sensitive material prepared has excellent pressure-sensitive properties. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is the SEM image of the sponge after carbonization in step (1) of Example 1;

[0016] Figure 2 is the Raman spectrum of the sponge after carbonization in step (1) of Example 1 and Comparative Example 1;

[0017] Figure 3 is the electrical conductivity and pressure-sensitive property diagram of the flexible pressure sensor obtained in Example 1 and Comparative Examples 1 and 2, respectively;

[0018] Figure 4 is the cycle stability test result diagram of the flexible pressure sensor prepared in Example 1;

[0019] Figure 5 is the test result diagram of the flexible pressure sensor prepared in Example 1 applied to respiratory rate detection. DETAILED DESCRIPTION

[0020] In order to better understand the content of the present application, the present application will be further described below in conjunction with specific examples and drawings. The following examples are implemented based on the technology of the present application, and detailed implementation modes and operation steps are given, but the protection scope of the present application is not limited to the following examples.

[0021] The PET electrodes sputtered with ITO in the examples and comparative examples are all purchased.

[0022] Example 1:

[0023] (1) First, the melamine sponge with a density of 0.0075 g / cm 3 was cut into small pieces of 5*2*0.5 cm with a knife, and 0.05 g of absorbent cotton was placed together with one piece of the melamine sponge into a porcelain boat (i.e. the mass ratio of the melamine sponge to the absorbent cotton was 3:4), and the porcelain boat was sent into a tube furnace for carbonization under the protection of high-purity nitrogen, and the temperature was raised to the carbonization temperature at a rate of 2 ℃ / min from room temperature, the carbonization temperature was 600 ℃, and the carbonization time was 1 h, and after the carbonization was completed, the temperature was naturally cooled to room temperature;

[0024] (2) The carbonized sponge was cut into 1*1 cm (length* width, i.e. both the length and the width were 1 cm) squares, one of which was taken as the middle layer, and two PET electrodes sputtered with ITO were respectively located on the opposite sides of the middle layer to form a sandwich structure, and the sandwich structure was fixed with adhesive tape, thereby obtaining a flexible pressure sensor.

[0025] Example 2:

[0026] (1) First, the melamine sponge with a density of 0.0075 g / cm 3 was cut into small pieces of 5*2*0.5 cm with a knife, and 0.02 g of absorbent cotton was placed together with one piece of the melamine sponge into a porcelain boat (i.e. the mass ratio of the melamine sponge to the absorbent cotton was 3:1.6), and the porcelain boat was sent into a tube furnace for carbonization under the protection of high-purity nitrogen, and the carbonization temperature was 600 ℃, and the carbonization time was 1 h, and after the carbonization was completed, the temperature was naturally cooled to room temperature;

[0027] (2) The carbonized sponge was cut into 1*1 cm (length* width, i.e. both the length and the width were 1 cm) squares, one of which was taken as the middle layer, and two PET electrodes sputtered with ITO were respectively located on the opposite sides of the middle layer to form a sandwich structure, and the sandwich structure was fixed with adhesive tape, thereby obtaining a flexible pressure sensor.

[0028] Example 3:

[0029] (1) First, the melamine sponge with a density of 0.0075 g / cm 3The melamine sponge was cut into small pieces of 5×2×0.5 cm with a knife. 0.075 g of absorbent cotton and one of the small pieces of melamine sponge were placed in a porcelain boat (i.e., the mass ratio of melamine sponge to absorbent cotton was 3:6). The porcelain boat was placed in a tube furnace and carbonized under the protection of high-purity nitrogen at a carbonization temperature of 550°C for 2 h. After the carbonization was completed, the mixture was naturally cooled to room temperature.

[0030] (2) The carbonized sponge was cut into 1*1 cm (length*width, i.e., length and width were both 1 cm) squares, one of which was used as the middle layer. Two PET electrodes sputtered with ITO were placed on opposite sides of the middle layer to form a sandwich structure, which was fixed with tape to obtain a flexible pressure sensor.

[0031] Comparative Example 1:

[0032] (1) First, the density of 0.0075g / cm 3 The melamine sponge was cut into small pieces of 5×2×0.5 cm with a knife. The prepared melamine sponge was placed in a porcelain boat, which was then placed in a tube furnace for carbonization under the protection of high-purity nitrogen. The temperature was raised from room temperature to the carbonization temperature at a rate of 2°C / min, the carbonization temperature was 600°C, the carbonization time was 1 hour, and the carbonization was completed and the mixture was naturally cooled to room temperature.

[0033] (2) The carbonized sponge was cut into 1*1 cm squares, one of which was used as the middle layer. Two PET electrodes sputtered with ITO were placed on opposite sides of the middle layer to form a sandwich structure, which was fixed with tape to obtain a flexible pressure sensor.

[0034] Comparative Example 2:

[0035] (1) First, the density of 0.0075g / cm 3 The melamine sponge was cut into small pieces of 5×2×0.5 cm with a knife, and 0.1 g of absorbent cotton and one of the melamine sponge pieces were placed in a porcelain boat (i.e., the mass ratio of melamine sponge to absorbent cotton was 3:8). The porcelain boat was placed in a tube furnace and carbonized under the protection of high-purity nitrogen. The temperature was raised from room temperature to the carbonization temperature at a rate of 2°C / min, the carbonization temperature was 600°C, the carbonization time was 1 h, and the carbonization was completed and the boat was naturally cooled to room temperature.

[0036] (2) The carbonized sponge was cut into 1*1 cm squares, one of which was used as the middle layer. Two PET electrodes sputtered with ITO were placed on opposite sides of the middle layer to form a sandwich structure, which was fixed with tape to obtain a flexible pressure sensor.

[0037] Figure 1The SEM image of the sponge after carbonization in Example 1 Step (1) shows a clear 3D skeleton structure.

[0038] Figure 2 The Raman spectra of the sponge after carbonization in Example 1 Step (1) and Comparative Example 1 Step (1) are shown in Figure 2, wherein the sponge after carbonization in Example 1 Step (1) is denoted as CMF / DC, and the sponge after carbonization in Comparative Example 1 Step (1) is denoted as CMF. It can be seen from Figure 2 that the G peak signal related to the degree of graphitization in the sponge after carbonization in Example 1 (i.e. the doped foam carbon) is enhanced, corresponding to the improvement of the electrical conductivity of the material. Figure 2

[0039] Figure 3 The conductive property and pressure-sensitive performance of the flexible pressure sensor obtained in Example 1 and Comparative Examples 1 and 2 are shown in Figure 3, wherein the doped amount of the absorbent cotton in Example 1 and Comparative Examples 1 and 2 is different. Figure 3 It can be seen from Figure 3 that the doped amount of the absorbent cotton has an effect on the conductive property and pressure-sensitive performance of the material. Specifically, it can be seen from Figure 3(a) that the conductive property of the material is improved with the increase of the doped amount. Figure 3 Figure 3 It can be seen from Figure 3(b) that the doped amount has an effect on the pressure-sensitive performance. When the doped amount is 0.05 g, the material has the highest sensitivity, and when the doped amount is 0.1 g, the sensitivity is reduced compared with the material without doped absorbent cotton.

[0040] Figure 4 Figure 4 is the result of the cycle stability test of the flexible pressure sensor prepared in Example 1. No obvious signal drift or fluctuation was observed in the cycle test after 12500 repeated loading and unloading. In the 12500 cycle performance test, the performance data of the first 6 cycles before the cycle test was compared with the performance data of the last 6 cycles after the cycle test, and it was found that the peak value and waveform of the output current signal had almost no change, indicating that the material has excellent cycle stability.

[0041] Figure 5 Figure 5 is the result of the test of the application of the flexible pressure sensor prepared in Example 1 to the detection of the breathing frequency. Different breathing frequency signals of the same test object were detected, including fast breathing (67.5 breaths per minute), normal breathing (31.5 breaths per minute) and slow breathing (18 breaths per minute), and the response data were very stable. This indicates that the sensor can effectively detect different breathing frequencies and can be effectively applied to physiological signal detection.

[0042] ​​The above merely illustrates the embodiments of the present application, and does not limit the present application in any form, and the present application can have other forms of embodiments according to the above structure and function, and does not list them one by one. Therefore, any skilled person in the art, without departing from the technical solution range of the present application, according to the technical essence of the present application, any simple modification, equivalent change and modification of the above embodiments, still belongs to the range of the technical solution of the present application.

Claims

1. A method for preparing a flexible pressure-sensitive material based on porous carbon sponge, characterized in that: The specific steps include: After putting the absorbent cotton and melamine sponge into a porcelain boat, the porcelain boat is sent into a tube furnace and carbonized under the protection of high-purity nitrogen. After the carbonization is completed, it is naturally cooled to room temperature to obtain a flexible pressure-sensitive material based on porous carbon sponge.

2. The method for preparing a flexible pressure-sensitive material based on porous carbon sponge according to claim 1, wherein: Cut the melamine sponge into small pieces, and then put the absorbent cotton and the small pieces of melamine sponge into the porcelain boat.

3. The method for preparing a flexible pressure-sensitive material based on porous carbon sponge according to claim 1, wherein: The carbonization temperature is 500-650°C, and the carbonization time is 1-2h; the temperature is raised from room temperature to the carbonization temperature at a heating rate of 2-5°C / min.

4. The method for preparing a flexible pressure-sensitive material based on porous carbon sponge according to claim 1, wherein: The mass ratio of melamine sponge to absorbent cotton is 3:1-3:

6.

5. A flexible pressure-sensitive material based on porous carbon sponge prepared by the preparation method according to any one of claims 1 to 4.

6. A method for preparing a flexible pressure sensor, characterized in that: The flexible pressure-sensitive material as described in claim 5 is cut into blocks, one of which is used as the middle layer. Two PET electrodes sputtered with ITO are placed on opposite sides of the middle layer to form a sandwich structure, which is fixed with tape to obtain a flexible pressure sensor.

7. A flexible pressure sensor prepared by the preparation method according to claim 6.

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