A flexible fabric-based mechanical sensor and a method for preparing the same

Abstract

The present invention discloses a flexible fabric-based mechanical sensor, comprising a force-sensitive area, wherein the force-sensitive area is composed of an overlapping top fabric and a bottom fabric; the top fabric comprises a flexible substrate layer, and an N-type heavily doped carbon nanowall on the flexible substrate layer; the bottom fabric comprises a flexible substrate layer, a carbon nanowall grown on the flexible substrate layer, and a Bi2Se3 film grown on the basis of the carbon nanowall; the N-type heavily doped carbon nanowall and the Bi2Se3 film are both coated with an aluminum oxide film. The flexible device of the present invention can remain stable in different complex environments, adapt to changes in temperature and pressure, and can therefore be applied to extreme environments.

Description

Technical Field

[0001] The invention relates to a flexible fabric-based mechanical sensor and a preparation method thereof, belonging to the technical field of flexible sensors. Background Art

[0002] Flexible wearable electronic devices have great application potential in the fields of human motion perception, personalized health monitoring, electronic skin and flexible robots. In order to achieve flexible wearability, a variety of materials are widely used in the field of flexible electronics, including polymers (such as polyimide, polyester), metal films (such as gold, copper), carbon nanomaterials (such as carbon nanotubes, graphene) and flexible glass. These materials bring many advantages, such as good flexibility, lightness and plasticity, which help electronic devices better adapt to the surface of the human body, improve comfort and wearability. However, these materials also have some limitations. For example, polymers may age and wear out during long-term use, metal films are prone to cracks after bending, and carbon nanomaterials have certain challenges in the preparation process.

[0003] Flexible wearable devices require that the flexible materials have sufficient mechanical flexibility, be able to fit well onto curved surfaces in a suitable shape, and be able to generate good signal responses to deformation. However, the characteristics of the above-mentioned flexible materials make the devices prone to electrical instability during long-term use or bending. In addition, the response range of existing devices is usually limited, making it difficult to meet the needs of complex environments and unable to work reliably in extreme environments, which has great limitations in specific application scenarios.

[0004] As a special material, topological insulators have the property of being insulating in the body but conducting on the surface or at the boundary. Bi2Se3, as a typical topological insulator, presents a microscopic layered structure during its growth. This layered structure enables the free electrons on the surface of Bi2Se3 to undergo quantum tunneling between different layers, thus forming a topological surface state. In contrast, graphene is a two-dimensional material with excellent conductivity and mechanical properties. When Bi2Se3 forms a heterojunction with two-dimensional materials such as graphene, the difference in its band gap and the coupling of its surface states can bring advantages in sensor design. In particular, by utilizing the quantum tunneling effect, this heterojunction can be used to prepare a stable and highly sensitive mechanical sensor.

[0005] However, the heterojunction formed by Bi2Se3 and graphene also has defects in the band gap structure, which reduces the sensitivity and stability of the sensor. Summary of the invention

[0006] The present invention provides a flexible fabric-based mechanical sensor, which solves the defect of the heterojunction formed by Bi2Se3 and graphene in the prior art, so that the flexible fabric-based mechanical sensor has excellent electrical properties.

[0007] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is a flexible fabric-based mechanical sensor, including a force-sensitive area, which is composed of a top fabric and a bottom fabric that are overlapped; the top fabric includes a flexible substrate layer, and an N-type heavily doped carbon nanowall on the flexible substrate layer; the bottom fabric includes a flexible substrate layer, a carbon nanowall grown on the flexible substrate layer, and a Bi2Se3 film grown on the basis of the carbon nanowall; the Bi2Se3 film is coated with an aluminum oxide film. The N-type heavily doped carbon nanowall is coated with an aluminum oxide film. In the present invention, coating with an aluminum oxide film is, on the one hand, to prevent the Bi2Se3 film from reacting with oxygen and water in the atmosphere, so that Bi2Se3 can exist stably in the atmospheric environment, thereby improving the stability of the device; on the other hand, Al2O3 can make up for the problem of mismatch between the Bi2Se3 band gap and the graphene band structure, reduce the work function difference between the two, improve the performance of the heterojunction, and enhance the sensitivity of the sensor.

[0008] Preferably, the flexible substrate layer is one of silicon carbide fiber, graphite fiber, asbestos fiber, glass fiber, metal fiber, nitrogen boron fiber or ceramic fiber. Silicon carbide fiber is preferred. It can also be asbestos fiber, glass fiber, metal fiber, nitrogen boron fiber or ceramic fiber. Using silicon carbide fiber fabric as a substrate has good mechanical strength and chemical stability, can adapt to temperature changes, pressure changes, etc., helps the device to work stably in extreme environments, and at the same time makes the sensor have excellent flexibility and can adapt to different shapes and application scenarios.

[0009] The present invention also provides a method for preparing a flexible fabric-based mechanical sensor, comprising the following steps: pretreating a flexible substrate layer; preparing a carbon nanowall on the pretreated flexible substrate layer, and using the carbon nanowall as a substrate, forming a Bi2Se3 film on the surface of the substrate, and then coating it with an aluminum oxide film to obtain a bottom fabric; preparing a carbon nanowall on the pretreated flexible substrate layer, and immersing the carbon nanowall in ammonia water for N-type heavy doping, and then coating it with an aluminum oxide film to obtain a top fabric; overlapping the top fabric and the bottom fabric to form a flexible fabric-based mechanical sensor.

[0010] Furthermore, the flexible substrate layer is pre-processed, specifically including the following steps: cutting and cleaning the flexible substrate layer, and then desizing it.

[0011] Furthermore, the PE-CVD method was used to prepare carbon nanowalls on the pretreated flexible substrate layer; the ALD method was used to coat the aluminum oxide film; and the vertically overlapping top fabric and bottom fabric were encapsulated using cling film electrostatic force mounting to form a flexible fabric-based mechanical sensor.

[0012] Furthermore, the carbon nanowall is immersed in ammonia water for 30 minutes to perform N-type heavy doping.

[0013] Furthermore, a Bi2Se3 film is formed by chemical reaction on the surface of the substrate, which specifically includes the following steps: Bi2Se3 powder and Se powder are weighed according to a Se:Bi atomic ratio of 10:1, and Bi and Se precursor gas molecules are chemically reacted on the surface of the substrate to form a Bi2Se3 film using a CVD method.

[0014] The present invention utilizes PECVD and CVD technologies to grow graphene nanosheets (GNW) and Bi2Se3 on silicon carbide fiber fabrics, respectively, soaks the doped graphene nanosheets in ammonia water, and plates an aluminum oxide film on the carbon nanowalls of the top fabric and the Bi2Se3 film of the bottom fabric, thereby compensating for the mismatch between the Bi2Se3 band gap and the graphene band structure, improving the performance of the heterojunction, and enhancing the sensitivity of the sensor; at the same time, by supplementing Se powder in proportion, the problem of excessive Se vacancies in Bi2Se3 is avoided, and the formed petal-like structure provides a better support effect, thereby enhancing the stability of Bi2Se3.

[0015] The flexible fabric-based mechanical sensor prepared by the present invention has excellent stability and sensitivity, and can adapt to extreme environmental changes. At the same time, since the flexible fabric-based mechanical sensor of the present invention is a contact-separation heterojunction, it has good durability and can continue to work stably in extreme environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the device structure of the flexible fabric-based mechanical sensor in an embodiment of the present invention;

[0017] Figure 2 It is a schematic diagram of forming a force-sensitive area of ​​a flexible fabric-based mechanical sensor in an embodiment of the present invention;

[0018] Figure 3 The carbon nanowall grown on the silicon carbide fiber in the embodiment of the present invention;

[0019] Figure 4 The relative potential diagram of GNW immersed in ammonia water for different time periods in the embodiment of the present invention;

[0020] Figure 5 The Bi2Se3 film grown by the carbon nanowall in the embodiment of the present invention;

[0021] Figure 6 Graph showing sensitivity test results of the flexible fabric-based mechanical sensor in Example 2 and Example 5 of the present invention;

[0022] Figure 7This is a graph showing the sensitivity test results of the flexible fabric-based mechanical sensor at different temperatures in Example 2 of the present invention. DETAILED DESCRIPTION

[0023] In order to better understand the essence of the present invention, the present invention is further described below in conjunction with specific embodiments and drawings.

[0024] The present invention provides a flexible fabric-based mechanical sensor, comprising a force-sensitive region, a copper wire and a conductive silver paste, wherein the two ends of the right-angled sides of the force-sensitive region are connected to the copper wires through the conductive silver paste as lead-out electrodes. The force-sensitive region is composed of a top fabric and a bottom fabric vertically overlapped; the top fabric comprises a flexible substrate layer, a carbon nanowall grown on the flexible substrate layer, and a Bi2Se3 film grown on the basis of the carbon nanowall; the bottom fabric comprises a flexible substrate layer, and an N-type heavily doped carbon nanowall on the flexible substrate layer; and the Bi2Se3 film is plated with an Al2O3 passivation layer.

[0025] In some embodiments of the present invention, an Al2O3 passivation layer is coated on the N-type heavily doped carbon nanowall located on the bottom flexible substrate layer; the carbon nanowall can be a single-layer graphene, a double-layer graphene, a few-layer graphene or a multi-layer graphene, and carbon nanowalls with different growth thicknesses can be selected according to specific application scenarios.

[0026] As a preferred embodiment of the present invention, the flexible substrate layer can be silicon carbide fiber fabric or graphite fiber, etc., which are flexible materials that can withstand high temperatures of 1500-3000°C; or asbestos fiber, glass fiber, metal fiber, nitrogen boron fiber or ceramic fiber, etc. Using silicon carbide fiber fabric as a substrate has good mechanical strength and chemical stability, can adapt to temperature changes, pressure changes, etc., helps the device to work stably in extreme environments, and at the same time makes the sensor have excellent flexibility and can adapt to different shapes and application scenarios.

[0027] The flexible substrate layer is in a rectangular block shape with a length and width of 6 cm×2 cm, and its force-sensitive area can be 1 cm×1 cm to meet the needs of miniaturized testing equipment.

[0028] An Al2O3 film is plated on the Bi2Se3 film to prevent the Bi2Se3 film from reacting with oxygen and water in the atmosphere, so that Bi2Se3 can exist stably in the atmospheric environment, thereby improving the stability of the device. On the other hand, due to the mismatch between the band gap of Bi2Se3 and the band structure of graphene, the heterojunction effect is not very strong, which reduces the sensitivity and performance of the sensor. Al2O3 can make up for the mismatch between the band gap of Bi2Se3 and the band structure of graphene, reduce the work function difference between the two, improve the performance of the heterojunction, and enhance the sensitivity of the sensor.

[0029] The working principle of the flexible fabric-based mechanical sensor of the present invention is mainly based on the tunneling effect of the heterojunction of Bi2Se3 and graphene. Under a fixed voltage, the tunneling effect enables electrons to pass through the energy gap and pass through the edge of the band structure between graphene and Bi2Se3, resulting in a significant current change, thereby realizing the response of the sensor. When the fabric-based strain sensor is subjected to strains such as stretching, twisting, bending, and deformation, the electronic energy level is adjusted, thereby changing the conductivity. By detecting the change in the current signal, the size and direction of the strain can be judged, and it can be further applied to the fields of flexible robots, robot dexterous hands, wearable electronic devices, prostheses, etc.

[0030] The present invention provides a method for preparing a flexible fabric-based mechanical sensor, comprising the following steps:

[0031] S1. Pre-treat the flexible substrate layer. Cut and clean the original silicon carbide fiber fabric and then desize it.

[0032] S2. Prepare three-dimensional conformal carbon nanowalls on the pretreated flexible substrate layer. Use PE-CVD method to grow carbon nanowalls on the desized fabric, such as Figure 3 shown.

[0033] S3. The carbon nanowall obtained in step S2 is immersed in ammonia water for 15 to 60 minutes to perform N-type heavy doping on it, and the change of the GNW work function is recorded, as shown in Table 1.

[0034] Table 1

[0035] Ammonia soaking treatment time GNW work function variation <![CDATA[Initial current of the GNW_Bi2Se3 device (the lower, the higher the sensitivity)]]> 0min 4.5ev 0.1mA 15min 4.785ev 55μA 30min 5.305ev 5μA 60min 4.755ev 25μA

[0036] By soaking the doped graphene nanosheets in ammonia, the heterojunction formed by graphene and Bi2Se3 is effectively enhanced. The work function of the carbon wall is changed by soaking in ammonia, as shown in Table 1. Figure 4 As shown, the work function difference between the carbon wall and Bi2Se3 becomes larger. Specifically, ammonia is strongly N-type doped, and Bi2Se3 itself is weakly N-type doped. This strong N-weak N-type heterojunction can also make up for the mismatch between the energy band structures of Bi2Se3 and graphene, and further improve the sensitivity and performance of the sensor.

[0037] S4. Using the carbon nanowall fabric soaked in ammonia water in step S3 as a substrate, forming an aluminum oxide film on the surface of the carbon nanowall by ALD method to obtain the bottom fabric of the flexible fabric-based mechanical sensor.

[0038] S5. The carbon nanowall fabric soaked in ammonia water in step S3 is used as a substrate, and a Bi2Se3 film is formed by chemical reaction on the surface of the substrate. In the raw materials for preparing the Bi2Se3 film, the ratio of Se:Bi atoms is 10:1.

[0039] The present invention can effectively prevent excessive Se vacancies during the growth process of Bi2Se3, thereby causing poor device stability. At the same time, the Bi2Se3 finally formed in the present invention has a self-supporting petal-shaped structure, which provides a better support effect, such as Figure 5 shown.

[0040] S6. An aluminum oxide film is formed on the surface of the Bi2Se3 film using the ALD method to obtain the top fabric of the flexible fabric-based mechanical sensor.

[0041] S7. Use plastic wrap to electrostatically mount the two pieces of fabric together to package them, which can keep the device in a good initial state.

[0042] The present invention uses PECVD and CVD technology to grow graphene nanosheets (GNW) and Bi2Se3 on silicon carbide fiber fabrics respectively. By soaking the doped graphene nanosheets in ammonia water and coating them with Al2O3 film, the problem of mismatch between the band gap of Bi2Se3 and the energy band structure of graphene can be effectively compensated, the performance of the heterojunction is improved, and the sensitivity of the sensor is enhanced; at the same time, by supplementing Se powder in proportion, the problem of too many Se vacancies in Bi2Se3 is avoided, and the formed petal-shaped structure provides a better support effect and enhances the stability of Bi2Se3. The improvement of the present invention not only enhances the responsiveness of the material, but also provides a more reliable basis for the stable operation of the sensor under extreme conditions.

[0043] In the prior art, carbon nanowall growth and Bi2Se3 film are usually performed multiple times on only one piece of fabric. However, the growth of carbon nanowall takes a long time, which makes the efficiency of the entire process low. At the same time, since the existing heterojunctions are all two-dimensional materials, they are obtained by layer-by-layer growth. The growth of subsequent materials needs to be based on the previous layer of materials, so they cannot be separated. Once the growth of one layer does not meet the requirements, the qualified materials that have been grown in the previous order will also be scrapped, which increases the production cost. The present invention grows the top and the bottom separately, thereby solving the shortcomings of the long growth time and easy loss of carbon nanowalls. At the same time, since the sensor of the present invention overlaps the top and the bottom when it is in use, it can be placed separately when not in use, forming a contact-separation heterojunction. Compared with the traditional contact heterojunction, the contact-separation structure can improve the stability and durability of the material. If the top or the bottom is damaged, it is also easy to replace, which greatly improves the qualified rate of the product and improves production efficiency.

[0044] Example 1

[0045] The present invention provides a flexible fabric-based mechanical sensor, comprising a force-sensitive region, a copper wire and a conductive silver paste, wherein the two ends of the right-angled sides of the force-sensitive region are connected to the copper wires through the conductive silver paste as lead-out electrodes. The force-sensitive region comprises a top fabric and a bottom fabric vertically overlapped; the top fabric comprises a silicon carbide fiber fabric, and an N-type heavily doped carbon nanowall on the silicon carbide fiber fabric; the bottom comprises a silicon carbide fiber fabric, a carbon nanowall grown on the silicon carbide fiber fabric, and a Bi2Se3 film grown on the carbon nanowall; an Al2O3 passivation layer is provided on the Bi2Se3 film and the N-type heavily doped carbon nanowall on the top fabric.

[0046] The silicon carbide fiber fabric is in a rectangular block shape with a length and width of 6 cm×2 cm. The carbon nanowall is multilayer graphene.

[0047] Example 2

[0048] Taking the flexible fabric-based mechanical sensor in Example 1 as an example, the preparation steps of the flexible fabric-based mechanical sensor in the present invention are described as follows:

[0049] Specific production steps:

[0050] S1. Pre-treating the flexible substrate layer.

[0051] The original silicon carbide fiber fabric was cut into rectangular blocks with a length and width of 6 cm × 2 cm. Since the dust particles on the surface of the fabric will affect the quality of fabric growth, the rectangular block fabric was first ultrasonically cleaned in deionized water, acetone and alcohol for 15 minutes to remove surface impurities. The cleaned fabric was then placed in a PECVD furnace for empty firing, the temperature was set to 600 ° C, and the temperature was kept for 2 hours.

[0052] To ensure the purity and surface quality of the substrate, the fabric needs to remove impurities and treatment agents from the surface of the fabric to improve the chemical purity of the fabric substrate and provide better surface conditions for subsequent processing steps.

[0053] S2. Select two pieces of desized fabrics and simultaneously grow carbon nanowalls using the PE-CVD method.

[0054] S3. Select a piece of carbon nanowall fabric obtained in step S2, soak it in ammonia water for 30 minutes, and perform N-type heavy doping on it.

[0055] S4. The N-type heavily doped carbon nanowall fabric in step S3 is used as a substrate, and a thin layer of aluminum oxide is formed by alternately supplying metal precursors and oxide precursors layer by layer to form a top fabric.

[0056] S5. Use an electronic balance to weigh Bi2Se3 powder and Se powder in a Se:Bi atomic ratio of 10:1, use another piece of carbon nanowall obtained in step S2 as a substrate, and use a CVD method to allow Bi and Se precursor gas molecules to chemically react on the substrate surface to form a Bi2Se3 film.

[0057] S6. Using the fabric grown with Bi2Se3 in step S5 as a substrate, a thin layer of aluminum oxide is formed by alternately supplying metal precursors and oxide precursors layer by layer, thereby obtaining the bottom fabric of the flexible fabric-based mechanical sensor.

[0058] S7. Device packaging: Use plastic wrap to electrostatically mount two pieces of fabric to keep the device in a good initial state.

[0059] Example 3

[0060] A flexible fabric-based mechanical sensor was prepared by the same method as in Example 2, with the following differences: S3. A piece of carbon nanowall fabric obtained in step S2 was selected and soaked in ammonia water for 15 minutes.

[0061] Example 4

[0062] A flexible fabric-based mechanical sensor was prepared by the same method as in Example 2, except that: S3. A piece of the carbon nanowall fabric obtained in step S2 was selected and soaked in ammonia water for 60 minutes.

[0063] Example 5

[0064] A flexible fabric-based mechanical sensor was prepared by the same method as in Example 2, with the difference being that the aluminum oxide film was not plated on the carbon nanowall of the top fabric and the Bi2Se3 film of the bottom fabric.

[0065] Example 6

[0066] 1. At room temperature, the sensitivity of the flexible fabric-based mechanical sensors prepared in Example 2 and Example 5 was tested. Before the test, the top fabric and the bottom fabric were placed as follows: Figure 2 The test results are as follows: Figure 6 As shown. Figure 6 It can be seen that the Al2O3 passivation layer can greatly improve the performance of the heterojunction.

[0067] 2. The sensitivity of the flexible fabric-based mechanical sensor prepared in Example 2 was tested at different temperatures.

[0068] The sensitivity test of this device is carried out under normal environment using a press machine (0-1MPa); the sensitivity is tested under high temperature using a heating table (temperature is 500 degrees) and applying pressure (weight, 0-1Kg); the sensitivity is tested under low temperature using a low temperature probe table at liquid nitrogen temperature and applying pressure (weight, 0-1Kg). The sensitivity test equipment is 2450, and the data is processed and plotted using origin later. The results are as follows Figure 7 shown.

[0069] from Figure 7 It can be seen that within the range of 0-100 KPa, the flexible fabric-based mechanical sensor in Example 1 has excellent sensitivity at room temperature, high temperature and low temperature environments.

[0070] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A flexible fabric-based mechanical sensor, comprising a force-sensitive area, characterized in that: The force-sensitive area is composed of an overlapping top fabric and a bottom fabric; the top fabric includes a flexible substrate layer and an N-type heavily doped carbon nanowall on the flexible substrate layer; the bottom fabric includes a flexible substrate layer, a carbon nanowall grown on the flexible substrate layer, and a Bi2Se3 film grown on the carbon nanowall; the N-type heavily doped carbon nanowall and the Bi2Se3 film are both coated with an aluminum oxide film.

2. The flexible fabric-based mechanical sensor according to claim 1, characterized in that: The flexible substrate layer is one of silicon carbide fiber, graphite fiber, asbestos fiber, glass fiber, metal fiber, nitrogen boron fiber or ceramic fiber.

3. A method for preparing a flexible fabric-based mechanical sensor, characterized in that: The following steps are involved: Pre-treating the flexible substrate layer; A carbon nanowall is prepared on a pretreated flexible substrate layer, and the carbon nanowall is used as a substrate. After a Bi2Se3 film is formed on the surface of the substrate, an aluminum oxide film is plated to obtain a bottom fabric; Preparing a carbon nanowall on a pretreated flexible substrate layer, and immersing the carbon nanowall in ammonia water for N-type heavy doping, and then coating it with an aluminum oxide film to obtain a top fabric; The top fabric and the bottom fabric are overlapped to form a flexible fabric-based mechanical sensor.

4. The method for preparing the flexible fabric-based mechanical sensor according to claim 3, characterized in that: The flexible substrate layer is pre-processed, specifically comprising the following steps: After the flexible substrate is cut and cleaned, it is desized.

5. The method for preparing the flexible fabric-based mechanical sensor according to claim 3, characterized in that: The carbon nanowall is prepared on the pretreated flexible substrate layer by using the PE-CVD method; and the aluminum oxide film is plated by using the ALD method.

6. The method for preparing the flexible fabric-based mechanical sensor according to claim 3, characterized in that: The vertically overlapping top fabric and bottom fabric are packaged using cling film electrostatic force mounting to form a flexible fabric-based mechanical sensor.

7. The method for preparing the flexible fabric-based mechanical sensor according to claim 3, characterized in that: The carbon nanowall is immersed in ammonia water for 15 to 60 minutes to perform N-type heavy doping.

8. The method for preparing the flexible fabric-based mechanical sensor according to claim 7, characterized in that: The carbon nanowall was immersed in ammonia water for 30 minutes to perform N-type heavy doping.

9. The method for preparing the flexible fabric-based mechanical sensor according to claim 3, characterized in that: Forming a Bi2Se3 film by chemical reaction on the surface of the substrate specifically comprises the following steps: Bi2Se3 powder and Se powder were weighed according to a Se:Bi atomic ratio of 10:1, and Bi and Se precursor gas molecules were chemically reacted on the surface of the substrate to form a Bi2Se3 film using a CVD method.

10. Application of the flexible fabric-based mechanical sensor according to any one of claims 1 to 2 in flexible robots, robot arms, wearable electronic devices and prostheses.

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