High-strength high-elasticity graphene metamaterial-based stress sensor and application thereof

Abstract

The application discloses a high-strength and high-elasticity graphene metamaterial-based stress sensor and application thereof. The sensor takes high-elasticity graphene metamaterial as a main sensor device, and forms a stress sensor through assembly design. Through compression of the graphene superstructure, resistance change of an internal network is caused, a current signal with strength change is formed, and different stress values are detected. The graphene metamaterial has characteristics of high conductivity, high strength and high elasticity, and can be used as a high-strength stress sensor.

Description

Technical Field

[0001] This invention relates to the field of graphene material preparation, specifically to a high-strength, high-elasticity graphene metamaterial-based stress sensor and its application. Background Technology

[0002] High-stress sensors achieve highly sensitive stress measurement based on the change in material resistance under stress, exhibiting a linear response over a wide stress range. They have crucial applications in many fields, especially in high-risk, high-safety industries such as aerospace, civil engineering, and the automotive industry. High-stress sensors can monitor the stress state of structures in real time, detecting potential faults or damage early, thereby effectively improving safety and reliability.

[0003] Meanwhile, graphene metamaterials, as a novel nanomaterial, have been widely used in sensors, energy storage, and thermal insulation materials in recent years due to their excellent conductivity, lightweight, and ultra-high specific surface area. Graphene aerogels, with their lightweight and high surface area advantages, exhibit high performance in many applications; however, their relatively low mechanical strength and stress-bearing capacity limit their application in high-stress environments, particularly in mechanical sensing. Traditional soft carbon aerogel materials, due to their structural characteristics and material properties, mostly exhibit low stress response performance, making it difficult for them to meet the high precision and sensitivity requirements of high-stress sensors.

[0004] Therefore, developing a graphene metamaterial that can operate stably under high stress conditions and possesses excellent sensing properties is crucial for improving the performance of stress sensors. Stress sensors typically rely on the change in resistance of a material after being subjected to stress, and the conductivity and microstructure optimization of graphene aerogels can further enhance their performance in mechanical sensors. Summary of the Invention

[0005] This invention provides a high-strength, high-elasticity graphene metamaterial-based stress sensor and its application. By optimizing the microstructure of the graphene metamaterial, its stress response performance and stability under high stress environments are significantly improved. This stress sensor utilizes the principle of resistance change in graphene metamaterials to achieve highly sensitive, linear-response stress measurement under stress, and maintains high stability under a wide range of stress conditions.

[0006] One of the technical solutions of the present invention is to provide a high-strength and high-elasticity graphene metamaterial-based stress sensor, comprising a substrate, a strain gauge, and a graphene metamaterial located between the two; the substrate, strain gauge, and graphene metamaterial are electrically connected; and the substrate, strain gauge, and digital source meter are connected, wherein the graphene metamaterial has an arched structure formed by horizontally stacking of bent graphene sheets; multiple arched structures are stacked vertically and fused together at the interface.

[0007] Furthermore, the thickness of the graphene metamaterial is 1mm-5cm.

[0008] Furthermore, the stacked arched structure has one or more layers.

[0009] Furthermore, the substrate is made of materials with excellent mechanical strength, thermal stability and good conductivity, such as silicon wafers, stainless steel, aluminum alloys or conductive polymers (such as polyimide PI), to ensure sufficient stability and mechanical strength during long-term use. The strain gauge is a high-sensitivity metal foil strain gauge, using metal foils such as copper foil, nickel foil, aluminum foil, and platinum alloy foil as strain elements.

[0010] Furthermore, the substrate and strain gauge are electrically connected to the graphene metamaterial via conductive silver paste.

[0011] The microstructure of this graphene metamaterial is specially designed, with vertically bent graphene sheets stacked laterally to form an arched structure, which induces a change in resistance under external stress. This change in resistance serves as the core principle of stress sensing, enabling highly sensitive stress measurement and maintaining a linear response over a wide stress range, thus providing reliable stress detection. By optimizing the microstructure of the graphene metamaterial, it maintains good mechanical properties and stress response characteristics even under high stress environments. The specific strength of this graphene metamaterial is higher than that of traditional soft carbon aerogels, enabling stable operation within a stress range exceeding 0.5 MPa, ensuring the long-term stability of the sensor.

[0012] The second technical solution of the present invention is to provide a method for preparing the above-mentioned stress sensor, comprising the following steps:

[0013] (1) A graphene oxide solution is extruded into a coagulation bath to obtain a graphene oxide metamaterial; multiple horizontal grid plates with a spacing greater than 10 μm are set at the extrusion port to horizontally divide the extrusion port; this is used to control the arrangement and stacking of graphene sheets. Generally, a rigid material is used as the grid. The design of this device is based on the fact that a velocity gradient difference will be generated during the liquid flow process, so that the graphene oxide sheets will experience shear force in the flow channel, thereby resulting in orderly arrangement and orientation;

[0014] (2) Reduce graphene oxide metamaterials to graphene metamaterials;

[0015] (3) Dry the graphene metamaterial;

[0016] (4) The dried graphene metamaterial is heat-treated at 300-2800℃;

[0017] High-temperature treatment can effectively release residual stress between graphene sheets, improving the material's crystallinity and structural stability. Through high-temperature treatment, the arrangement of graphene sheets is further optimized, and the material's strength, conductivity, and resilience are significantly improved.

[0018] (5) The obtained graphene metamaterial is electrically connected to the substrate and strain gauge to form a vertically stacked heterostructure, resulting in a high-strength, high-elasticity graphene metamaterial-based stress sensor. Further, the graphene oxide solution in step (1) also includes a polymer; the polymer is one of PAN, PAA, PVA and PVP, and the mass of graphene oxide in the solute of the graphene oxide solution is not less than 30%; the concentration of graphene oxide is 5.0 to 80.0 mg / mL.

[0019] Further, the coagulation bath in step (1) is a metal salt solution or a polyamine solution, including one of calcium chloride, aluminum chloride, diamine, and triamine; the metal salt or polyamine can undergo a cross-linking reaction with graphene oxide. Generally, high-valence metal salt solutions such as calcium chloride and aluminum chloride are selected as the coagulation bath.

[0020] Further, the reduction method in step (2) involves reacting in a reducing agent with a concentration of 5 wt% for 5 hours; the reducing agent is one of sodium ascorbate, hydroiodic acid, hydrobromic acid, tin dichloride, and hydrazine hydrate. The reduction process not only improves the conductivity of the material but also further enhances its mechanical properties.

[0021] Furthermore, the drying method described in step (3) is freeze drying or room temperature and atmospheric pressure drying.

[0022] Further, the graphene oxide solution in step (1) is a pure graphene oxide solution or a mixed solution of graphene oxide and polymer; the polymer is one of PAN, PAA, PVA and PVP, and the mass of graphene oxide in the solute of the graphene oxide solution is not less than 30%; the concentration of graphene oxide is 5.0 to 80.0 mg / mL.

[0023] The preparation method described in this invention uses a grid as a fluid subdivision device. The shear anchoring effect of the grid on the graphene oxide slows down the flow rate of the graphene oxide solution near the grid, while the flow rate is faster away from the grid. This causes the graphene oxide solution to form a C-structure when it is forced into the coagulation bath through the fluid subdivision device. Specifically, the portion near the grid is parallel to the grid, while the middle portion away from the grid is perpendicular to it. This structure allows the material to more effectively disperse and resist stress under load. Compared to a closed cross-section, the open C-shaped cross-section helps to disperse stress, reduce stress concentration points, and thus improve the overall long-term cycling stability of the material.

[0024] The electrical properties of graphene metamaterials are closely related to their microstructure. In this invention, the graphene metamaterial employs an arched structure formed by laterally stacked bent graphene sheets. This structure enhances the material's response to external stress. Specifically, under stress, the relative arrangement, slippage, and electron transport paths between the graphene sheets undergo structural changes, leading to localized disturbances in the flow of charge carriers within the material, ultimately manifesting as changes in electrical resistance.

[0025] Under compressive stress, the distance between graphene sheets decreases, shortening the electron migration path and thus enhancing carrier mobility and reducing electrical resistance. The compressive effect may also enhance the π-π packing interaction between graphene sheets, improving electron conductivity and further reducing resistance. Conversely, when graphene metamaterials are subjected to tensile stress, the relative distance between graphene sheets increases, leading to a longer carrier migration path and consequently reducing electron mobility and increasing electrical resistance. Furthermore, the tensile effect causes slight deformation of the graphene lattice, altering the electron transition energy levels and thus affecting conductivity.

[0026] In practical applications, the quantitative relationship between resistance change and stress can be expressed by the following formula: in, The change in resistance, The applied stress (which can be tensile, compressive, or bending stress). η is the stress-resistance response coefficient, representing the degree of influence of stress on resistance. By optimizing and adjusting the materials, η can be kept within a suitable range, thereby ensuring the sensor's high sensitivity and linear response.

[0027] The third technical solution of the present invention is to provide an application of the above-mentioned stress sensor in intelligent monitoring equipment, health monitoring equipment, structural health monitoring or flexible electronic products.

[0028] The beneficial effects of this invention are as follows: Graphene metamaterials themselves possess extremely strong chemical stability and excellent oxidation resistance. After optimization and design by this invention, the sensor exhibits extremely high environmental adaptability and long-term stability. Even under extreme environmental conditions (such as high temperature, low temperature, high humidity, strong acids and alkalis), the sensor's performance remains stable, and its resistance response is unaffected by external factors. Compared to traditional stress sensors, it has a longer service life and lower maintenance costs, significantly reducing performance degradation issues during long-term use.

[0029] The stress sensor of this invention can operate stably over an extremely wide stress range. Whether subjected to minute tensile forces or extremely high compressive stresses, the sensor maintains a linear response and exhibits exceptional stability even under high stress. This broad operating stress range gives the sensor unparalleled advantages in high-risk environments, making it suitable for various high-safety-standard fields such as aerospace, civil engineering, and the automotive industry, enabling high-precision monitoring around the clock and from all directions. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a stress sensor;

[0031] Figure 2 (a) The structure of the grating, Figure 2 (b) shows the cross-sectional structure of the metamaterial in Example 1;

[0032] Figure 3 This illustrates the response of the current to external pressure in Example 1.

[0033] Figure 4 This refers to the stress change over 5000 cycles in the stress sensor of Example 2;

[0034] Figure 5 Example 2: Stress sensing test;

[0035] Figure 6 The resistance change in the stress sensor in Example 3;

[0036] Figure 7 This is a schematic diagram of the structure of Example 4. Detailed Implementation

[0037] This invention aims to provide a high-strength, high-elasticity graphene metamaterial-based stress sensor. This sensor uses highly elastic graphene metamaterial as the main sensor element, and through assembly design, forms a stress sensor. For example... Figure 1 As shown, it includes a graphene metamaterial, a substrate, and strain gauges. The graphene metamaterial has an arched structure formed by laterally stacked bent graphene sheets; multiple arched structures are stacked vertically and fused together at the interfaces. Compression of this graphene metamaterial causes a change in the resistance of its internal network, generating a current signal with varying intensity, thereby detecting different stress values. This graphene metamaterial possesses high conductivity, high strength, and high resilience, making it suitable for use as a high-intensity stress sensor.

[0038] The following examples are provided to further illustrate the present invention and are intended to explain the invention, not to limit its scope. Unless otherwise specified, all figures are expressed in parts by weight and weight percentages.

[0039] Unless otherwise specified, the raw materials used in this invention are all conventional commercially available products; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0040] The thickness of the graphene metamaterial described in this invention is determined by the direction in which multiple graphene material arch-shaped structures are stacked vertically.

[0041] The coagulation bath used in this invention is a commonly used coagulation bath in the art, including but not limited to calcium chloride, aluminum chloride, diamine, and triamine. As is common knowledge in the art, the concentration of the coagulation bath is generally between 1 wt% and 10 wt%.

[0042] The embodiments of the present invention will be further described below with reference to several examples.

[0043] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0044] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0045] Example 1

[0046] (1) The extrusion port is divided into parallel sections using multiple grid plates with a vertical spacing of 100 μm. An 80 mg / mL aqueous solution of graphene oxide and PAN are mixed and passed through the following process: Figure 2 The grid shown was extruded into a triamine coagulation bath with a graphene oxide to PAN mass ratio of 3:7. The triamine on the graphene surface was then washed away with water multiple times to obtain a graphene oxide superstructure hydrogel.

[0047] (2) The gel-like graphene oxide metamaterial from step 1 was immersed in a 5wt% tin dichloride solution, the temperature was controlled at 80 °C, and the reaction was carried out for 5 hours to reduce the graphene oxide. Then, the free ions on its surface were washed away with water multiple times to obtain the gel-like graphene metamaterial.

[0048] (3) The gel-like graphene metamaterial in step 2 is freeze-dried to remove internal moisture and ensure the integrity of the structure, so as to obtain the freeze-dried sample.

[0049] (4) The freeze-dried sample from step 3 was subjected to high-temperature annealing at 300℃ to obtain a rectangular graphene metamaterial.

[0050] (5) Electrically connect a 2cm thick graphene metamaterial to a silicon wafer and strain gauge copper foil. After sensing testing. (For example...) Figure 3 As shown, the current change of the stress sensor prepared in this embodiment has a linear relationship with the applied stress. The simulated linear curves are: ① Stress (kPa) = (current change value - 0.048) / 0.0059 (current change value < 0.16). ② Stress (kPa) = (current change value + 0.199) / 0.016 (current change value > 0.16).

[0051] A stress sensor is used to apply pressure to the strain gauge of the device. Based on the above formulas ① and ②, the pressure value is calculated according to the acquired current signal. The actual pressure value and the calculated pressure value are shown in Table 1 below.

[0052] Table 1. Accuracy Test of Stress Sensor in Example 1

[0053]

[0054] As shown in Table 1, the device exhibits an error within 2% over a wide range (10-140 kPa). Furthermore, sensing tests revealed that the internal resistance of the graphene metamaterial remains almost constant with each compression and rebound cycle, demonstrating its durability and cyclic performance.

[0055] Example 2

[0056] (1) The extrusion port was divided in parallel by multiple grid plates with a vertical spacing of 50 μm. A 5 mg / mL aqueous solution of graphene oxide and PVA were mixed evenly and extruded into a coagulation bath of diamine. The mass ratio of graphene oxide to PVA was 5:5. Then, the diamine on the surface of graphene was washed away with water multiple times to obtain graphene oxide superstructure hydrogel.

[0057] (2) The gel-like graphene oxide metamaterial from step 1 was immersed in a 5wt% hydroiodic acid solution, the temperature was controlled at 80 °C, and the reaction was carried out for 5 hours to reduce the graphene oxide. Then, the free ions on its surface were washed away with water multiple times to obtain the gel-like graphene metamaterial.

[0058] (3) The gel-like graphene metamaterial in step 2 is freeze-dried to remove internal moisture and ensure the integrity of the structure, so as to obtain the freeze-dried sample.

[0059] (4) The freeze-dried sample from step 3 was subjected to high-temperature annealing at 2800℃ to obtain a rectangular graphene metamaterial.

[0060] (5) Electrically connect the 1mm thick graphene metamaterial to the stainless steel substrate and the strain gauge nickel foil.

[0061] like Figure 4As shown, this stress sensor exhibits a stress range of 140 kPa within 70% of the strain, far exceeding that of other carbonaceous materials, and also demonstrates high sensitivity. The graphene metamaterial shows almost unchanged compression and rebound in each of 5000 cycles, proving its durability and cyclic performance. Sensing tests are as follows... Figure 5 As shown, the current change of this device tends to be consistent with the stress value change within a large range (10-140 kPa). The stress sensor has a stress range of 140 kPa within 66% of the strain, which is far greater than that of other carbonaceous materials.

[0062] Example 3

[0063] (1) The extrusion port was divided in parallel by multiple grid plates with a vertical spacing of 50 μm. 15 mg / mL of graphene oxide aqueous solution and PAA were mixed and extruded into the coagulation bath of aluminum chloride. The mass ratio of graphene oxide to PAA was 6:4. The free aluminum on the surface of graphene was washed away with water multiple times to obtain graphene oxide superstructure hydrogel.

[0064] (2) The gel-like graphene oxide metamaterial from step 1 was immersed in a 5wt% hydrobromic acid solution, the temperature was controlled at 80 °C, and the reaction was carried out for 5 hours to reduce the graphene oxide. Then, the free ions on its surface were washed away with water multiple times to obtain the gel-like graphene metamaterial.

[0065] (3) The gel-like graphene metamaterial in step 2 is freeze-dried to remove internal moisture and ensure the integrity of the structure, so as to obtain the freeze-dried sample.

[0066] (4) The freeze-dried sample from step 3 was subjected to high-temperature annealing at 300℃ to obtain a rectangular graphene metamaterial.

[0067] (5) Electrically connect the 5cm thick graphene metamaterial to the substrate and strain gauge. The substrate is an aluminum alloy and the strain gauge is an aluminum foil.

[0068] After sensing tests, the device showed an error within 3% over a wide range (10-140 kPa). The stress sensor exhibited a stress range of 145 kPa within 70% strain, far exceeding that of other carbonaceous materials. Over 100 cycles at 70% strain, the internal resistance of the graphene metamaterial remained almost constant with each compression and rebound cycle, demonstrating its durability and cyclic performance.

[0069] Example 4

[0070] (1) The extrusion port was divided in parallel by multiple grid plates with a vertical spacing of 10 μm. A 10 mg / mL aqueous graphene oxide solution was extruded into a calcium chloride coagulation bath. The free calcium on the graphene surface was washed away with water multiple times to obtain a graphene oxide superstructure hydrogel.

[0071] (2) The graphene oxide superstructure hydrogel in step 1 was immersed in a 5wt% sodium ascorbate solution, the temperature was controlled at 80 °C, and the reaction was carried out for 5 hours to reduce the graphene oxide. Then, the free ions on its surface were washed away with water multiple times to obtain a gel-like graphene supermaterial.

[0072] (3) The gel-like graphene metamaterial in step 2 is freeze-dried to remove internal moisture and ensure the integrity of the structure, so as to obtain the freeze-dried sample.

[0073] (4) The freeze-dried sample from step 3 was subjected to high-temperature annealing at 1000 °C to obtain a rectangular graphene metamaterial.

[0074] (5) Electrically connect a 5cm thick graphene metamaterial to a substrate and a strain gauge. The substrate is polyimide, and the strain gauge is a platinum alloy foil. This yields a flexible stress sensor.

[0075] Furthermore, the aforementioned flexible stress sensor is encapsulated with an elastic buffer material before application to protect the internal graphene metamaterial and electrodes. The elastic buffer material can be an elastic polymer, such as TPU / PU (polyurethane elastomer), polyethylene foam, EVA (ethylene-vinyl acetate copolymer), etc. Details are as follows:

[0076] (1) Sensor installation: Graphene metamaterial-based stress sensors are installed on the joints of the robot arm. The sensors are precisely placed at the load-bearing locations to ensure accurate monitoring of stress changes generated during operation.

[0077] (2) Stress testing and response detection: When the robot arm performs handling tasks (e.g., moving car body parts or performing welding operations), the joints will experience a load of approximately 100 kPa. During this process, sensors monitor and record the stress response of the robot arm joints in real time.

[0078] (3) Data Acquisition and Analysis: The sensor can obtain stress change data based on the change in current, and the sensor transmits the stress change data to the central control system in real time. Through data analysis, the control system can evaluate the working status of the robot in real time. If the stress value exceeds the set threshold, the system will automatically adjust, such as slowing down the robot's movement speed, or issuing an alarm signal if the robot arm malfunctions.

[0079] (4) Feedback and adjustment: Based on real-time monitoring data, the robot control system can make responsive adjustments, such as reducing the load, changing the working trajectory, or triggering the robot to pause, in order to prevent further stress damage or structural failure.

[0080] The above embodiments describe in detail the structure, features, and effects of the present invention. The above description is only a preferred embodiment of the present invention. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, shall still fall within the scope of protection of the present invention if they do not exceed the scope covered by the specification.

Claims

1. A high strength high elasticity graphene metamaterial based stress sensor, characterized in that, The graphene metamaterial includes a substrate, a strain gauge, and graphene located between the substrate and the strain gauge; the substrate, the strain gauge, and the graphene are electrically connected; the substrate, the strain gauge, and a digital source table are connected; the graphene has an arch structure formed by stacking curved graphene sheets in a transverse direction; a plurality of arch structures are stacked in a vertical direction and fused with each other at an interface. The graphene superstructure is compressed to cause a change in resistance of an internal network, form a current signal with a change in strength, and detect different stress values. The graphene metamaterial is prepared by the following steps: (1) extruding a graphene oxide solution into a coagulation bath to obtain an oxidized graphene metamaterial; a plurality of horizontal grid plates with a mutual distance greater than 10 μm are arranged at an extrusion outlet to horizontally divide the extrusion outlet; (2) reducing the oxidized graphene metamaterial into a graphene metamaterial; (3) drying the graphene metamaterial; (4) heat treating the dried graphene metamaterial at 300-2800 °C.

2. The stress sensor of claim 1, wherein The graphene metamaterial has a thickness of 1 mm-5 cm.

3. The stress sensor of claim 1, wherein, The stacked arch structures are greater than or equal to 1 layer.

4. The stress sensor of claim 1, wherein, The substrate is one of a silicon wafer, stainless steel, an aluminum alloy, and a conductive polymer; the strain gauge is a metal foil strain gauge, which is one of a copper foil, a nickel foil, an aluminum foil, and a platinum alloy metal foil.

5. The stress sensor of claim 1, wherein, The substrate and the strain gauge are electrically connected to the graphene metamaterial by conductive silver paste.

6. The stress sensor of claim 1, wherein, In step (1), the graphene oxide solution further includes a polymer; the polymer is one of PAN, PAA, PVA, and PVP; the mass fraction of graphene oxide in the solute of the graphene oxide solution is not less than 30%; the concentration of the graphene oxide is 5.0-80.0 mg / mL; the coagulation bath is a metal salt solution or a polyamine solution, which includes one of calcium chloride, aluminum chloride, and one of di-amine and tri-amine; the metal salt or the polyamine can cross-link with the graphene oxide.

7. Application of the stress sensor of claim 1 to intelligent monitoring equipment, health monitoring equipment, structural health monitoring, or flexible electronic products.

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