Graphene flexible gradient pressure sensor array system and preparation method thereof

Abstract

The invention discloses a graphene flexible gradient pressure sensor array system and a preparation method thereof, and belongs to the field of pressure sensors. The graphene flexible gradient pressure sensor array system comprises an array circuit board, and a transverse array unit circuit, a longitudinal array unit circuit, a graphene flexible gradient pressure sensing unit and a graphene flexible gradient pressure sensitive element which are arranged on the array circuit board. The two graphene flexible gradient pressure sensing elements are perpendicular to each other and are arranged in a cross shape, and the two graphene flexible gradient pressure sensing elements and the four electrodes are combined to form a graphene flexible gradient pressure sensing unit. The graphene flexible gradient pressure sensing unit is pressed to generate electric signal change, and the electric signal change is converted into a pressure value through the signal acquisition and processing system. According to the preparation method, a lamination and superposition method is adopted, and graphene is sequentially laminated from bottom to top according to the stepped content from small to large. Therefore, the tensile property of the bottom polymer is relatively optimal, and the rigidity to the top material is also continuously enhanced.

Description

Technical Field

[0001] The invention relates to a graphene flexible gradient pressure sensor array system and a preparation method thereof, and belongs to the field of pressure sensors. Background Art

[0002] Sensor units are core components of wearable devices, smart detection and other applications. However, the current preparation process of smart sensor units is relatively complicated, and most materials use precious metals, which are extremely expensive, and the sensitivity and stability of use do not meet the expected results. Graphene is a two-dimensional structure of a hexagonal honeycomb lattice formed by sp2 hybridization of carbon atoms. Due to the stable connection between carbon atoms, graphene has good mechanical, electrical, optical, and thermal properties and excellent light transmittance. It also has good flexibility and stability; and its resistivity reaches 10 -6 Ω·cm, better conductivity than copper and silver, and better biocompatibility than traditional metal materials. Wearable devices based on graphene have better perception performance, smart green and high ergonomic design matching, and have broad application prospects. At the same time, silicone rubber also has good strength and elasticity, corrosion resistance and aging resistance, and is also widely used in the medical field.

[0003] Functional gradient material is a new type of composite material with continuous gradient changes in components and structures, which has no obvious interface and reduces interface damage. The characteristics of gradient materials are the inhomogeneity of organization, multi-scale and continuity of mechanical properties, as well as the multi-level nature of structure. Conductive films made of gradient structures can give full play to the mechanical properties and conductive properties of materials. Currently, there is little research on polymers.

[0004] Chinese invention patent applications with application numbers CN201610863656 and CN201210013024 have applied for graphene-based array pressure distribution sensors. Both patents use pure graphene film as the sensing unit, which results in the graphene pressure sensor being unable to be used for monitoring a larger pressure range. In addition, the process for preparing the graphene film is complex, the material cost is high, and the reliability of the device is poor, which is not conducive to widespread application. Although patent CN201610863656 adds a layer of polymer to the graphene surface, when the strain is large, stratification is likely to occur between the two; and the graphene layer is located at the bottom, with greater deformation, and it is easy to tear the graphene layer apart, resulting in unstable performance and even equipment damage. Therefore, it is necessary to provide a new material structure and a lower-cost process method. The use of a coating method to prepare a conductive gradient film material can ensure the mechanical properties, sensitivity and stability of the material, and the process is simple and can be mass-produced and used. Summary of the invention

[0005] In order to solve the problem that traditional strain sensors cannot meet the measurement requirements under large strain conditions and the measurement structure range is limited, the purpose of the present invention is to provide a graphene flexible gradient pressure sensor array system and a preparation method thereof, which is based on a high-sensitivity flexible gradient conductive film and an array unit circuit arranged on an array circuit board. The conductive film with a gradient structure can give full play to the mechanical properties and conductive properties of the material, realize the gradient of the function, improve the strain limit of the sensing unit, and significantly increase the maximum range of the sensor. The preparation method of the present invention has the advantages of simple equipment, simple operation, stable process, continuous operation, high production efficiency, and high automation, and can industrially prepare large-area, thin and flat conductive gradient functional materials.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] A graphene flexible gradient pressure sensor array system includes an array circuit board and a transverse array unit circuit, a longitudinal array unit circuit, a graphene flexible gradient pressure sensing unit and a graphene flexible gradient pressure sensitive element arranged on the array circuit board. Two graphene flexible gradient pressure sensitive elements are arranged perpendicular to each other in a cross-shaped arrangement, and the two graphene flexible gradient pressure sensitive elements and four electrodes are combined to form a graphene flexible gradient pressure sensing unit. A plurality of graphene flexible gradient pressure sensing units are arranged in series in a transverse array to form a transverse array unit circuit. A plurality of graphene flexible gradient pressure sensing units are arranged in series in a longitudinal array to form a longitudinal array unit circuit. When the graphene flexible gradient pressure sensing unit is subjected to pressure, the change in electrical signal generated is converted into a pressure value through a signal acquisition and processing system.

[0008] Furthermore, the array series connection is realized through a flexible circuit board, and the flexibility of the pressure sensing unit and the circuit board makes the sensor array system have the advantage of flexibility.

[0009] Furthermore, the graphene flexible gradient pressure sensitive element is a multilayer gradient flexible conductive sensing film composed of graphene and polysiloxane; the graphene concentration gradually increases from bottom to top.

[0010] The method for preparing the pressure sensor array system comprises the following steps:

[0011] Step 1: Carve a number of grooves on the flexible circuit board to form an array circuit board;

[0012] Step 2: Arrange the transverse array unit circuit and the longitudinal array unit circuit on the array circuit board; the array circuit includes longitude and latitude, and the circuit formed is used to connect the electrodes at both ends of each sensor unit, and control the gating of the unit device through the analog switch;

[0013] Step 3, preparing a graphene flexible gradient pressure sensitive element; preparing a plurality of mixed solutions of graphene and polysiloxane, wherein the concentration of graphene in the mixed solutions is different; coating is performed gradually from bottom to top to form a graphene flexible gradient pressure sensitive element precursor with a step-type change; cutting to obtain a graphene flexible gradient pressure sensitive element;

[0014] Step 4: Laminating the graphene flexible gradient pressure sensitive element with the array circuit board to form a cross shape, and the upper graphene flexible gradient pressure sensitive element is stacked on the lower graphene flexible gradient pressure sensitive element, so that the upper graphene flexible gradient pressure sensitive element has a slight protrusion relative to the whole, and the electrodes at both ends form ohmic contact with the array circuit; obtaining a graphene flexible gradient pressure sensing unit;

[0015] Step 5: Connect the array circuit to the signal acquisition and processing system to prepare the pressure sensor array system; collect the signal of each unit in the sensor array in real time and convert it into a pressure value; input it to the digital display through the analog-to-digital converter, and use the LCD to display and analyze the curves and values ​​in real time.

[0016] Beneficial effects:

[0017] 1. The present invention discloses a graphene flexible gradient pressure sensor array system and a preparation method thereof, which adopts a lamination method to stack graphene from bottom to top in a step-by-step manner from less to more content. Therefore, the tensile properties of the bottom polymer are relatively the best, and the stiffness of the top material is also continuously enhanced.

[0018] 2. The present invention discloses a graphene flexible gradient pressure sensor array system and a preparation method thereof. The graphene flexible gradient pressure sensing unit adopts a groove design to fully improve the strain range. The conductive film with a gradient structure can increase the strain degree of the material and increase the safety of the material. In addition, compared with homogenized conductive polymer materials, the content of conductive fillers is reduced, thereby reducing costs.

[0019] 3. The present invention discloses a graphene flexible gradient pressure sensor array system and a preparation method thereof, which adopts a design in which the upper gradient conductive film has a slight protrusion relative to the whole, thereby increasing the distance when under pressure contact and having a higher sensitivity, so that it can sense quickly; and can also form two sensing array unit lines, a horizontal array unit line and a longitudinal array unit line, which are controlled by a circuit program to increase the safety of the equipment.

[0020] 4. The present invention discloses a graphene flexible gradient pressure sensor array system and a preparation method thereof, which adopts a conductive film with a gradient structure so that the graphene flexible gradient pressure sensing unit exhibits the non-uniformity, multi-scale and continuity of mechanical properties of the tissue, as well as the multi-level nature of the structure.

[0021] 5. The present invention discloses a graphene flexible gradient pressure sensor array system and a preparation method thereof, which adopts a coating method to prepare a conductive gradient thin film material, wherein a conductive polymer solution is evenly coated on a platform by a roller, and a multi-layer conductive film is formed after multiple coatings. The process is simple, the cost is low, and large-scale production can be carried out. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a graphene flexible gradient pressure sensor array system;

[0023] Figure 2 is a cross-sectional view of a sensor array unit;

[0024] Figure 3 The deformation of the graphene flexible gradient pressure sensitive element;

[0025] Figure 4 The invention provides steps for preparing a graphene flexible gradient pressure sensor array system;

[0026] Figure 5 This is the preparation process of gradient conductive thin film materials.

[0027] Among them, 1 is a transverse array unit circuit, 2 is a longitudinal array unit circuit, 3 is a graphene flexible gradient pressure sensing unit, and 4 is a graphene flexible gradient pressure sensitive element. DETAILED DESCRIPTION

[0028] In order to better illustrate the purpose and advantages of the present invention, the invention is further described below with reference to the accompanying drawings and examples.

[0029] Embodiment 1:

[0030] The graphene flexible gradient pressure sensor array system disclosed in this embodiment is as follows Figure 1 As shown, it includes an array circuit board and a transverse array unit circuit, a longitudinal array unit circuit, a graphene flexible gradient pressure sensing unit and a graphene flexible gradient pressure sensitive element arranged on the array circuit board. Two graphene flexible gradient pressure sensitive elements are arranged perpendicular to each other in a cross shape, and the two graphene flexible gradient pressure sensitive elements and four electrodes are combined to form a graphene flexible gradient pressure sensing unit. A plurality of graphene flexible gradient pressure sensing units are arranged in series in a transverse array to form a transverse array unit circuit. A plurality of graphene flexible gradient pressure sensing units are arranged in series in a longitudinal array to form a longitudinal array unit circuit. When the graphene flexible gradient pressure sensing unit is pressurized, the electrical signal change generated is converted into a pressure value through a signal acquisition and processing system. The corresponding array size parameters can be modified according to the specific use environment and equipment requirements.

[0031] like Figure 4As shown, the preparation method of the graphene flexible gradient pressure sensor array system disclosed in this embodiment is specifically implemented in the following steps:

[0032] Step 1: Carve a number of grooves on the rigid circuit board; use laser cutting to carve a 4×3 array of groove areas of 1mm×1mm in size with a spacing of 0.5mm on the upper layer of the rigid circuit board.

[0033] Step 2: Arrange the array circuit on the array circuit board with the grooves carved; make the array circuit on the array circuit board with a line width of 0.1mm, corresponding to the hollow area; the array circuit includes a horizontal array unit line 1 and a vertical array unit line 2, and the circuit formed is used to connect the electrodes at both ends of each sensor unit, and control the selection of the unit device through the analog switch.

[0034] Step 3: Prepare a step-type graphene flexible gradient pressure sensitive element precursor, using graphene and polysiloxane to prepare a gradient conductive film material. Figure 5 As shown, there are the following steps.

[0035] Step a: Add 100 parts of polysiloxane and 20 parts of fumed silica as a reinforcing agent into a large beaker, use a stirring device and heat to 100°C, stir and mix for 1 hour. Finally, place in a vacuum box and evacuate for 15 minutes to obtain the base material.

[0036] Step b: The base material obtained in step a is divided into 4 equal parts and placed in four beakers #1, #2, #3 and #4 in turn. Then, 0.2 parts, 0.4 parts, 0.6 parts and 0.8 parts of graphene are weighed into the above four beakers in turn, and the corresponding contents are 0.8wt%, 1.6wt%, 2.4wt% and 3.2wt% (the percolation threshold of the silicone rubber graphene conductive polymer is about 0.8wt%, and it has excellent conductivity when the content is 3wt%, and the overall sensitivity GF≥50 or more), so that the content of the conductive filler changes in a step-type manner. Ultrasonic dispersion is carried out in an ultrasonic instrument for 2 hours to obtain a graphene conductive polymer solution.

[0037] Step c: Use a coating machine to coat the film. The entire operation process is as follows: Figure 5 First, a cleaned inert substrate is placed on the platform, and then 1.5 parts of hydrogenated silicone oil crosslinking agent and 0.2 parts of platinum catalyst are added to the graphene conductive polymer solution obtained in step b, and stirred evenly for 10 minutes; secondly, the conductive polymers in beakers #1, #2, #3, and #4 are added to the needle tube in the coating machine in turn, and then coating is started in turn.

[0038] Step d: The thickness of each layer of the film is about 15 to 100 μm, and the film material with a certain gradient content is coated and stacked in sequence by lamination method; a certain temperature (about 50°C) is first applied to the platform for full curing, and finally a graphene flexible gradient pressure sensitive element precursor with a step-type change is obtained.

[0039] Step 4: Cut the step-shaped graphene flexible gradient pressure sensitive element precursor prepared in step 3 into a plurality of graphene flexible gradient pressure sensitive elements 4; cut the gradient conductive film material into 1.2 mm × 0.6 mm pressure sensitive elements by laser cutting. The deformation of the graphene flexible gradient pressure sensitive element 4 under pressure is as follows: Figure 3 shown.

[0040] Step 5: Attach the graphene flexible gradient pressure sensitive element 4 to the array circuit board to form a cross shape, and stack the upper graphene flexible gradient pressure sensitive element on the lower graphene flexible gradient pressure sensitive element, so that the upper graphene flexible gradient pressure sensitive element has a slight protrusion relative to the whole, and the electrodes at both ends form an ohmic contact with the array circuit to obtain a graphene flexible gradient pressure sensing unit 3. The structural cross-sectional view of the graphene flexible gradient pressure sensing unit 3 is shown in FIG. Figure 2 shown.

[0041] Step 6: Connect the transverse array unit line 1 and the longitudinal array unit line 2 to the signal acquisition and processing system. Each unit signal in the sensor array can be collected in real time and converted into a pressure value. The analog-to-digital converter inputs it to the digital display, and the liquid crystal display is used to display and analyze the curve and value in real time.

[0042] Step seven, test the specification coefficient of the graphene flexible gradient pressure sensor array system under large strain conditions; place the graphene flexible gradient pressure sensor array system under a universal testing machine, apply 30% strain to the graphene flexible gradient pressure sensing unit 3, and obtain the specification coefficient of the graphene flexible gradient pressure sensor array system is 65.51, the response time is 85ms, and it has good stability.

[0043] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A graphene flexible gradient pressure sensor array system, characterized in that: It comprises an array circuit board and a transverse array unit circuit, a longitudinal array unit circuit, a graphene flexible gradient pressure sensing unit and a graphene flexible gradient pressure sensitive element arranged on the array circuit board; two graphene flexible gradient pressure sensitive elements are arranged perpendicular to each other in a cross shape, and the two graphene flexible gradient pressure sensitive elements and four electrodes are combined to form a graphene flexible gradient pressure sensing unit; a plurality of graphene flexible gradient pressure sensing units are arranged in series in a transverse array to form a transverse array unit circuit; a plurality of graphene flexible gradient pressure sensing units are arranged in series in a longitudinal array to form a longitudinal array unit circuit; when the graphene flexible gradient pressure sensing unit is subjected to pressure, the change in electrical signal generated is converted into a pressure value through a signal acquisition and processing system.

2. A graphene flexible gradient pressure sensor array system as claimed in claim 1, characterized in that: The array series connection is realized through a flexible circuit board, and the flexibility of the pressure sensing unit and the circuit board makes the sensor array system have the advantage of flexibility.

3. A graphene flexible gradient pressure sensor array system as claimed in claim 1, characterized in that: The graphene flexible gradient pressure sensitive element is a multilayer gradient flexible conductive sensing film composed of graphene and polysiloxane; the graphene concentration gradually increases from bottom to top.

4. A method for preparing a pressure sensor array system as claimed in claim 1, 2 or 3, characterized in that: The following steps are included: Step 1: Carve a number of grooves on the flexible circuit board to form an array circuit board; Step 2: Arrange the transverse array unit circuit and the longitudinal array unit circuit on the array circuit board; the array circuit includes longitude and latitude, and the circuit formed is used to connect the electrodes at both ends of each sensor unit, and control the gating of the unit device through the analog switch; Step 3, preparing a graphene flexible gradient pressure sensitive element; preparing a plurality of mixed solutions of graphene and polysiloxane, wherein the concentration of graphene in the mixed solutions is different; coating is performed gradually from bottom to top to form a graphene flexible gradient pressure sensitive element precursor with a step-type change; cutting to obtain a graphene flexible gradient pressure sensitive element; Step 4: Laminating the graphene flexible gradient pressure sensitive element with the array circuit board to form a cross shape, and the upper graphene flexible gradient pressure sensitive element is stacked on the lower graphene flexible gradient pressure sensitive element, so that the upper graphene flexible gradient pressure sensitive element has a slight protrusion relative to the whole, and the electrodes at both ends form ohmic contact with the array circuit; A graphene flexible gradient pressure sensing unit is obtained; Step 5: Connect the array circuit to the signal acquisition and processing system to prepare the pressure sensor array system; collect the signal of each unit in the sensor array in real time and convert it into a pressure value; input it to the digital display through the analog-to-digital converter, and use the LCD to display and analyze the curves and values ​​in real time.

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