Pore water pressure sensor based on intelligent flexible material

Abstract

The invention discloses a pore water pressure sensor based on an intelligent flexible material, and relates to a pore water pressure sensor. The pore water pressure gauge is mainly invented for solving the problem that the existing pore water pressure gauge can generate fatigue damage or mechanical damage and the like in the long-term use process. The sensor comprises a sensitive element arranged in a shell, the surface of the sensitive element is coated with a pressure-sensitive film, a water filtering plate is arranged above the sensitive element, a cavity is formed between the water filtering plate and the sensitive element, the sensitive element comprises a flexible substrate and a micro-channel arranged on the flexible substrate, and the micro-channel is filled with a conductive layer. The conductive layer is prepared from the following raw materials: poly (3, 4-ethylenedioxythiophene), polystyrolsulfon acid, tridecafluorooctyltriethoxysilane, N, N-dimethylacetamide, polyacrylonitrile, polyvinylidene fluoride, poly (1, 5-naphthalene diamine) and a carbon nano tube; the pressure-sensitive film is of a continuous layered structure formed by compounding silk fibroin and a two-dimensional material; the flexible substrate is made of polyethylene glycol terephthalate. The sensor has the advantage of high fatigue damage resistance.

Description

Technical field:

[0001] The invention relates to a pore water pressure sensor, in particular to a pore water pressure sensor based on an intelligent flexible material. Background technology:

[0002] The vibrating string pore water pressure gauge is an instrument used to measure the pore water pressure in soil or rock. It is suitable for long-term burial in hydraulic structures or other concrete structures and foundations to measure the pore water pressure inside the structure or foundation, and can simultaneously measure the temperature of the burial point. The pore water pressure gauge is a device that senses pressure and converts it into a frequency signal output that is in a certain relationship with the pressure. Its typical structure consists of a pressure sensing membrane, a vibrating string, an excitation signal pickup device, a sealed housing and a shielded cable, etc., and is used to monitor the distribution of water pressure in the rock and soil. The performance of the sensor mainly depends on the material and structure of the sensor, especially the material of the sensor directly determines the sensitivity, range, hysteresis, repeatability, durability and other performance of the sensor. With the improvement of the requirements for various performance of sensors and their applicability in various geological environments, the performance of these sensors is slightly insufficient and has certain defects. For example, the vibrating-wire pore-water pressure gauge, whose sensitive elements are mostly made of rigid or brittle materials, will suffer fatigue damage or mechanical damage during long-term use, and will also be disturbed by the external environment. For example, temperature will affect the refractive index of the fiber grating to light, the steel string will become loose or fatigue damaged due to long-term use, and the resistivity of traditional piezoresistive materials is easily disturbed by the external environment such as the magnetic field. Flexible pressure sensors with different working principles are easy to be damaged, have a low range, and are easily disturbed by various external signals. Therefore, it is not enough to use them for pressure monitoring in geotechnical engineering.

[0003] Therefore, it is necessary to solve the problems of fatigue damage or mechanical destruction of sensors and anti-interference. Summary of the invention:

[0004] The technical problem to be solved by the present invention is to provide a pore water pressure sensor based on intelligent flexible material, which avoids fatigue damage or mechanical damage during long-term use of the pore water pressure sensor, is less affected by external environmental interference, can improve detection accuracy and stability, reduce failure rate, and improve durability.

[0005] The pore water pressure sensor based on intelligent flexible materials of the present invention comprises a shell and a sensitive element arranged in the shell, the surface of the sensitive element is coated with a pressure-sensitive membrane, a water filter plate is arranged in the shell above the sensitive element, a cavity area is formed between the water filter plate and the sensitive element, the sensitive element comprises a flexible substrate and a microchannel arranged on the flexible substrate, and the microchannel is filled with a conductive layer.

[0006] The raw materials of the conductive layer include poly (3,4-ethylenedioxythiophene), polystyrene sulfonic acid, tridecafluorooctyl triethoxysilane, N,N-dimethylacetamide, polyacrylonitrile, polyvinylidene fluoride, poly (1,5-naphthalenediamine) and carbon nanotubes;

[0007] Furthermore, the weight proportions of the raw materials of the conductive layer are: 10-20 parts of poly (3,4-ethylenedioxythiophene), 10-20 parts of polystyrene sulfonic acid, 4-8 parts of tridecafluorooctyltriethoxysilane, 1-5 parts of N,N-dimethylacetamide, 0.5-1.5 parts of polyacrylonitrile, 0.5-1.5 parts of polyvinylidene fluoride, 1-3 parts of poly (1,5-naphthalenediamine), and 1-3 parts of carbon nanotubes; the raw materials are mixed evenly according to the weight proportions and then filled into the microchannel.

[0008] Furthermore, the pressure-sensitive film is a composite of silk fibroin and a two-dimensional material into a continuous layered structure; the two-dimensional material is Ti3C2;

[0009] The preparation method of the pressure-sensitive film is as follows:

[0010] The silk fibroin aqueous solution is dissolved in the formic acid solution, the mass ratio of the silk fibroin aqueous solution to the formic acid solution is 18:100, and then the Ti3C2 solution is added and ultrasonically stirred evenly, and after vacuum filtration, the obtained film is dried in a vacuum drying oven until the formic acid is completely volatilized; the method obtains a single-layer film of Ti3C2 and silk fibroin, and then the multi-layer film is composited together and coated on the sensitive original;

[0011] The weight ratio of silk fibroin and two-dimensional material is:

[0012] Silk fibroin: 2D material = 4-6:1;

[0013] Further, the material of the flexible substrate is polyethylene terephthalate;

[0014] Further, the water filter plate is a permeable stone;

[0015] Furthermore, the thickness of the permeable stone is 2-3 mm, and the thickness of the pressure-sensitive film is 2-3 mm;

[0016] Furthermore, the height of the cavity area is 1-2 mm.

[0017] The beneficial effects of the present invention are as follows: the sensor has good softness and deformability, has the advantages of moderate sensitivity, low hysteresis and high repeatability, has high fatigue damage resistance, strong anti-interference ability, high detection accuracy and good stability, and improves the durability of the sensor. Description of the drawings:

[0018] Figure 1 It is a schematic diagram of the cross-sectional structure of the pore water pressure sensor of the present invention. Specific implementation method:

[0019] Combine the following Figure 1 The present invention is further described;

[0020] The pore water pressure sensor based on intelligent flexible materials comprises a shell 1 and a sensitive element 3 arranged in the shell 1, wherein the surface of the sensitive element 3 is coated with a pressure-sensitive membrane 31, a water filter plate 2 is arranged above the sensitive element 3, a cavity area is formed between the water filter plate and the sensitive element 3, the sensitive element comprises a flexible substrate 32 and a microchannel arranged on the flexible substrate 32, wherein the microchannel is filled with a conductive layer; the conductive layer material comprises poly (3,4-ethylenedioxythiophene), polystyrene sulfonic acid, tridecafluorooctyl triethoxysilane, N,N-dimethylacetamide, polyacrylonitrile, polyvinylidene fluoride, poly (1,5-naphthalenediamine) and carbon nanotubes.

[0021] The setting and arrangement of the microchannel is a prior art, for example, the channel is designed to be wavy.

[0022] The weight proportions of the raw materials of the conductive layer are: 10-20 parts of poly-3,4-ethylenedioxythiophene, 10-20 parts of polystyrene sulfonic acid, 4-8 parts of tridecafluorooctyltriethoxysilane, 1-5 parts of N,N-dimethylacetamide, 0.5-1.5 parts of polyacrylonitrile, 0.5-1.5 parts of polyvinylidene fluoride, 1-3 parts of poly-1,5-naphthalenediamine, and 1-3 parts of carbon nanotubes; the raw materials are mixed evenly according to the weight proportions and then filled into the microchannel.

[0023] The pressure-sensitive film is composed of silk fibroin and a two-dimensional material composited into a continuous layered structure; the two-dimensional material is Ti3C2; during the composite process, the silk fibroin and the two-dimensional material interact with each other and self-assemble into a continuous layered structure, thereby improving the flexibility and mechanical stability of the composite film and imparting excellent pressure-sensitive properties.

[0024] The preparation method of the pressure-sensitive film:

[0025] The silk fibroin aqueous solution was dissolved in the formic acid solution, the mass ratio of the silk fibroin aqueous solution to the formic acid solution was 18:100, and then the Ti3C2 solution was added and ultrasonically stirred evenly, and the obtained film was dried in a vacuum drying oven after vacuum filtration until the formic acid was completely volatilized;

[0026] The weight ratio of silk fibroin and two-dimensional material is:

[0027] Silk fibroin: 2D material = 4-6:1;

[0028] The flexible substrate material is polyethylene terephthalate; it not only gives the sensor flexibility, but also has a high degree of compatibility with the conductive layer, thereby improving the sensitivity of the sensor.

[0029] The water filter plate is a permeable stone; the thickness of the permeable stone is 2-3 mm, the thickness of the pressure-sensitive membrane is 2-3 mm; the height of the cavity area is 1-2 mm. The smaller the thickness of the permeable stone and the length of the cavity, the more beneficial it is to improve the response rate of the pore water pressure.

[0030] The working principle of the sensor of the present invention is: the main function of the water filter plate is to filter the water in the pores of the rock and soil into the cavity structure, and the cavity is located between the permeable stone and the sensitive element. The pressure water is collected into the cavity through the permeable stone and acts on the pressure-sensitive membrane. The size of the cavity is inversely proportional to the response rate of the sensor. Through the action of stress waves in the water, the pressure-sensitive membrane transmits the pressure to the sensitive element inside. The sensitive element is deformed after being compressed, and the cross-sectional area of ​​the microchannel filled with conductive material inside is reduced, resulting in an increase in the resistance value of the conductive material. The resistance value is measured by a DC resistance meter, and then the relationship between the resistance value R and the pressure P is established. The purpose of monitoring the pressure value is achieved by measuring the resistance value. This is a prior art and will not be described here one by one. Therefore, the water pressure can be measured by monitoring the output signal of the sensitive element.

[0031] Generally, resin is used as the shell of the sensor. As one of the force-bearing structures of the sensor, the shell can increase the range of the sensor. At the same time, the shell can isolate the sensitive element from the external environment, protect the sensitive element, and prevent damage to the sensitive element. The main function of the water filter plate is to filter the water in the pores of the rock and soil into the cavity structure, and the cavity is located between the permeable stone and the sensitive element. The pressure water is collected in the cavity through the permeable stone and acts on the pressure-sensitive membrane. The uniform water pressure is transmitted to the sensitive element through the pressure-sensitive membrane. The pressure-sensitive membrane can separate the sensitive element from the water to prevent the sensitive element from being hydrolyzed and damaged underwater for a long time; at the same time, it can also increase the range of the sensor.

[0032] For sensitive elements, the conductive layer uses poly (3,4-ethylenedioxythiophene) and polystyrene sulfonic acid to improve the response sensitivity, conductivity and mechanical flexibility, so that the sensor has excellent repeatability, low power consumption and high spatial resolution. The use of tridecafluorooctyl triethoxysilane can improve the hydrophobicity of the composite material. N,N-dimethylacetamide as a solvent can improve the conductivity of the composite material. Polyacrylonitrile and polyvinylidene fluoride synergistically improve the sensitivity and durability of the sensor. Poly (1,5-naphthalene diamine) (P1,5-DAN) is a typical aromatic diamine conductive polymer. In addition to having a large π bond structure like polyaniline, it also has a large number of active free amino groups. Carbon nanotubes, as a special carbon material with a one-dimensional nanostructure with good conductivity, catalytic activity and a high aspect ratio, can be combined with polymers to improve the conductivity of polymers in neutral solutions.

[0033] Embodiment 1;

[0034] In the pore water pressure sensor based on intelligent flexible materials of this embodiment, the conductive layer raw materials used in the sensitive element are, by weight, 10 parts of poly (3,4-ethylenedioxythiophene), 10 parts of polystyrene sulfonic acid, 4 parts of tridecafluorooctyltriethoxysilane, 1 part of N,N-dimethylacetamide, 0.5 parts of polyacrylonitrile, 0.5 parts of polyvinylidene fluoride, 1 part of poly (1,5-naphthalenediamine), and 1 part of carbon nanotubes.

[0035] Embodiment 2;

[0036] In the pore water pressure sensor based on intelligent flexible materials of this embodiment, the conductive layer raw materials used in the sensitive element are, by weight, 20 parts of poly (3,4-ethylenedioxythiophene), 20 parts of polystyrene sulfonic acid, 8 parts of tridecafluorooctyltriethoxysilane, 5 parts of N,N-dimethylacetamide, 1.5 parts of polyacrylonitrile, 1.5 parts of polyvinylidene fluoride, 3 parts of poly (1,5-naphthalenediamine), and 3 parts of carbon nanotubes.

[0037] Embodiment 3;

[0038] In the pore water pressure sensor based on intelligent flexible materials of this embodiment, the conductive layer raw materials used in the sensitive element are, by weight, 12 parts of poly (3,4-ethylenedioxythiophene), 18 parts of polystyrene sulfonic acid, 5 parts of tridecafluorooctyltriethoxysilane, 4 parts of N,N-dimethylacetamide, 1.2 parts of polyacrylonitrile, 1 part of polyvinylidene fluoride, 2 parts of poly (1,5-naphthalenediamine), and 2.5 parts of carbon nanotubes.

[0039] Embodiment 4;

[0040] In the pore water pressure sensor based on intelligent flexible materials of this embodiment, the conductive layer raw materials used in the sensitive element are, by weight, 15 parts of poly (3,4-ethylenedioxythiophene), 15 parts of polystyrene sulfonic acid, 6 parts of tridecafluorooctyltriethoxysilane, 3 parts of N,N-dimethylacetamide, 1 part of polyacrylonitrile, 1 part of polyvinylidene fluoride, 2 parts of poly (1,5-naphthalenediamine), and 2 parts of carbon nanotubes.

[0041] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A pore water pressure sensor based on intelligent flexible materials, comprising a housing and a sensitive element arranged in the housing, wherein the surface of the sensitive element is coated with a pressure-sensitive film, a water filter plate is arranged above the sensitive element, a cavity area is formed between the water filter plate and the sensitive element, the sensitive element comprises a flexible substrate and a microchannel arranged on the flexible substrate, wherein the microchannel is filled with a conductive layer; wherein the characteristics are: The conductive layer material includes poly (3,4-ethylenedioxythiophene), polystyrene sulfonic acid, tridecafluorooctyl triethoxysilane, N,N-dimethylacetamide, polyacrylonitrile, polyvinylidene fluoride, poly (1,5-naphthalenediamine) and carbon nanotubes.

2. The pore water pressure sensor based on the intelligent flexible material according to claim 1 is characterized in that: The weight proportions of the raw materials of the conductive layer are: 10-20 parts of poly-3,4-ethylenedioxythiophene, 10-20 parts of polystyrene sulfonic acid, 4-8 parts of tridecafluorooctyltriethoxysilane, 1-5 parts of N,N-dimethylacetamide, 0.5-1.5 parts of polyacrylonitrile, 0.5-1.5 parts of polyvinylidene fluoride, 1-3 parts of poly-1,5-naphthalenediamine, and 1-3 parts of carbon nanotubes; the raw materials are mixed evenly according to the weight proportions and then filled into the microchannel.

3. The pore water pressure sensor based on the intelligent flexible material according to claim 1 or 2, characterized in that: The pressure-sensitive film is formed by compounding silk fibroin and two-dimensional material into a continuous layered structure.

4. The pore water pressure sensor based on the smart flexible material according to claim 3 is characterized in that: The two-dimensional material is Ti3C2.

5. The pore water pressure sensor based on the smart flexible material according to claim 3 is characterized in that: The preparation method of the pressure-sensitive film: The silk fibroin aqueous solution was dissolved in the formic acid solution, the mass ratio of the silk fibroin aqueous solution to the formic acid solution was 18:100, and then the Ti3C2 solution was added and ultrasonically stirred evenly. After vacuum filtration, the obtained film was dried in a vacuum drying oven until the formic acid was completely volatilized.

6. The pore water pressure sensor based on the smart flexible material according to claim 5 is characterized in that: The weight ratio of silk fibroin and two-dimensional material is: Silk fibroin: two-dimensional material = 4-6:

1.

7. The pore water pressure sensor based on the smart flexible material according to claim 1 is characterized in that: The flexible substrate material is polyethylene terephthalate.

8. The pore water pressure sensor based on the smart flexible material according to claim 1 is characterized in that: The water filter plate is a permeable stone, and the thickness of the permeable stone is 2-3 mm.

9. The pore water pressure sensor based on the smart flexible material according to claim 1 is characterized in that: The thickness of the pressure-sensitive film is 2-3 mm; the height of the cavity area is 1-2 mm.

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