A sensor electrode plate, a flexible sensor and a method for manufacturing the same

Abstract

The application relates to a sensor electrode plate, a flexible sensor and a preparation method thereof. The sensor electrode plate comprises at least one graphene layer and at least one molybdenum sulfide layer, the graphene layer is composed of graphene oxide, the graphene layer and the molybdenum sulfide layer are stacked to form a layered structure, and the graphene layer and the molybdenum sulfide layer are alternately stacked when the total number of the graphene layer and the molybdenum sulfide layer is greater than or equal to 3. The flexible sensor has good comfort and adhesion, good sensing performance, good reusability and response time, and the sensitivity under a large-strain working environment is much higher than that of a traditional capacitive sensor.

Description

TECHNICAL FIELD

[0001] The present application relates to a sensor electrode plate, a flexible sensor and a preparation method thereof, in particular to a sensor electrode plate, a wearable flexible sensor and a preparation method thereof, and belongs to the technical field of wearable electronic devices. BACKGROUND

[0002] Due to interesting applications in healthcare monitoring, soft robotics, artificial intelligence and human-machine interface, skin-inspired wearable devices have great potential in the next generation of smart portable electronics. A lot of research work has been done to customize wearable devices more intelligently in terms of thickness, portability, flexibility, bendability and stretchability, in order to make human interactive devices penetrate into global market and family, and economic manufacturing technology is essential to realize large-scale flexible system with high throughput capacity.

[0003] By realizing high sensitivity, large-area sensing, super-stretchability and design, the performance and function of capacitive strain sensors have been improved. In the past decade, several methods based on optical, chemical and electrical phenomena have been developed to detect mechanical effects from the environment. In recent years, stretchable and wearable strain sensors have been studied due to their potential applications in structural health monitoring. Among them, capacitive sensing technology has been widely studied to obtain spatially distributed high specificity resolution on a large area that can reach the square centimeter limit. However, due to the overlap between the batteries, the resistance method cannot provide high performance; however, capacitive sensor arrays avoid this drawback. SUMMARY

[0004] In view of the deficiencies of the prior art, one of the purposes of the present application is to provide a sensor electrode plate with excellent sensitivity and a preparation method thereof; the second purpose of the present application is to provide a flexible sensor.

[0005] In order to solve the above technical problems, the technical scheme of the present application is as follows:

[0006] A sensor electrode plate, comprising at least 1 layer of graphene layer and at least 1 layer of molybdenum sulfide layer, the graphene layer is composed of graphene oxide, and the graphene layer and the molybdenum sulfide layer are stacked to form a layered structure; when the total number of graphene layers and molybdenum sulfide layers is ≥3 layers, the graphene layers and the molybdenum sulfide layers are alternately stacked.

[0007] In this way, the graphene layers and the molybdenum sulfide layers are stacked to form a layered structure, which can make the electrode plate have better flexibility, and at the same time, the electron transfer between different layers is more frequent, which is more active than a single-layer electrode plate under the same stress, which helps to improve the sensitivity and strain resistance of the electrode plate.

[0008] Further, the thickness of the graphene layer is 2-10 μm, preferably 4-8 μm.

[0009] Further, the thickness of the molybdenum sulfide layer is 2-10 μm, preferably 4-8 μm.

[0010] Further, the thickness of the molybdenum sulfide layer is 1-4 times, preferably 1.5-3.5 times, the thickness of the graphene layer.

[0011] Further, the total number of layers of the graphene layer and the molybdenum sulfide layer is 3-5 layers.

[0012] The method for preparing the sensor electrode plate as described above comprises the following steps:

[0013] S1, pouring a water dispersion of graphene oxide into a vacuum filtration machine, and performing filtration to obtain a graphene layer on a filter membrane of the vacuum filtration machine;

[0014] S2, pouring a water dispersion of molybdenum sulfide into the vacuum filtration machine, and performing filtration to form a molybdenum sulfide layer on a surface of the graphene layer;

[0015] S3, repeating S1 and S2 as needed to obtain a sensor electrode plate on the filter membrane;

[0016] S4, immersing the sensor electrode plate together with the filter membrane in an organic solvent, and separating the sensor electrode plate from the filter membrane.

[0017] The graphene oxide as the bottommost layer can facilitate quick separation of the sensor electrode plate from the filter membrane by using a solution method, and the subsequent immersion of the sensor electrode plate together with the filter membrane in an organic solvent can cause the sensor electrode plate to automatically fall off from the filter membrane. In addition, the fluffy structure of the graphene oxide is suitable for being used as a pressure contact layer of the sensor, which can help to further improve the sensitivity of the flexible sensor.

[0018] Further, the concentration of the graphene oxide in the water dispersion of graphene oxide is 0.5-3 mg / mL, and more further 1-2 mg / mL, and preferably 2 mg / mL.

[0019] Optionally, the water dispersion of graphene oxide is obtained by dispersing graphene oxide in water through ultrasonic dispersion.

[0020] Further, the concentration of the molybdenum sulfide in the water dispersion of molybdenum sulfide is 0.5-3 mg / mL, and more further 1-2 mg / mL, and preferably 1 mg / mL.

[0021] Optionally, the water dispersion of molybdenum sulfide is obtained by dispersing molybdenum sulfide in water through ultrasonic dispersion.

[0022] Preferably, the molybdenum sulfide is few-layer molybdenum sulfide.

[0023] Further, the filter membrane is circular, with a diameter of 40-60 mm, and the filtration range is consistent with the size of the filter membrane.

[0024] Further, in S1, 1-6 mL of the aqueous dispersion of graphene oxide is poured into the vacuum filtration machine, and more further, 3-4 mL of the aqueous dispersion of graphene oxide is poured into the vacuum filtration machine.

[0025] Further, in S2, 1-6 mL of the aqueous dispersion of molybdenum sulfide is poured into the vacuum filtration machine, and more further, 1-4 mL of the aqueous dispersion of molybdenum sulfide is poured into the vacuum filtration machine.

[0026] Preferably, the air suction speed is controlled to be 8-12 m 3 / h during filtration.

[0027] Further, in S4, the organic solvent is one or more of ethanol, methanol, and diethyl ether, and is preferably ethanol.

[0028] Further, the filter membrane is a microporous filter membrane, and is preferably a water-based microporous filter membrane.

[0029] Further, in S4, the sensor electrode plate is separated from the filter membrane by soaking for 3-7 min.

[0030] Optionally, in S4, the sensor electrode plate is transferred to a flexible substrate in the organic solvent, to obtain a sensor electrode plate with a flexible substrate.

[0031] A flexible sensor includes a flexible substrate, and the flexible substrate is provided with a sensor electrode plate as described above or a sensor electrode plate prepared by the preparation method as described above.

[0032] Optionally, both sides of the sensor electrode plate are provided with electrodes connected to the sensor electrode plate.

[0033] Optionally, the electrodes are silver electrodes.

[0034] Optionally, silver paste is applied to both sides of the sensor electrode plate to form silver electrodes.

[0035] Optionally, the surface of the sensor electrode plate away from the flexible substrate is provided with an encapsulation layer. Optionally, the encapsulation layer is a VHB tape layer.

[0036] Optionally, the flexible substrate is one of a PDMS substrate, a PET substrate, and a paper substrate.

[0037] A preparation method of a flexible sensor as described above, including the following steps:

[0038] (1) preparing a sensor electrode plate by the preparation method as described above;

[0039] (2) transferring the sensor electrode plate to a flexible substrate to obtain a sensor electrode plate with a flexible substrate;

[0040] (3) evenly applying silver paste around the sensor electrode plate and making the silver paste contact the sensor electrode plate, and drying to obtain a flexible sensor.

[0041] Optionally, in step (3), the silver paste is evenly spin-coated on both sides of the sensor electrode plate.

[0042] Optionally, after step (3), a packaging step is further included. Optionally, the flexible sensor is packaged by using a VHB tape.

[0043] The flexible sensor of the present application not only has good flexibility, ductility, comfort, high sensitivity for large-area testing, but also can maintain high sensitivity testing performance under large strain conditions, and can be widely applied to device testing, biological skin testing and large-area testing environments. The piezoresistive part of the flexible sensor is an easy-to-handle material, which also has positive significance in environmental protection.

[0044] The structure of the sensor electrode plate of the present application is controllable, has good machinability and flexibility, and can be processed into a target pattern according to the required shape and size, and can be well applied to industrial device testing, artificial intelligence wear and medical testing and other fields.

[0045] The flexible sensor of the present application not only has good comfort and conformability, but also has good sensing performance, has good number of reusable times and response time, and has much higher sensitivity than traditional capacitive sensors under large strain working environment. The uniform distribution of the sensor electrode plate makes the entire sensing range have more contact points, the flexible substrate and the packaging layer packaged outside the sensor electrode plate greatly reduce the loss of the sensor electrode plate, which helps to improve the service life, and also makes the sensor maintain higher sensitivity and sensing performance under large strain environment. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 FIG. 1 is a cross-sectional structure diagram of a flexible sensor of the present application.

[0047] Figure 2 FIG. 4 is an SEM cross-sectional view of a sensor electrode plate of Example 1 of the present application.

[0048] Figure 3 FIG. 5 is a sensitivity diagram of the flexible sensor of Example 1 of the present application under large strain.

[0049] Figure 4The sensitivity of the traditional sensor (i.e., the graphene oxide sensor designed in the document: Wan S, Bi H, Zhou Y, et al. Graphene oxide as high-performance dielectric materials for capacitive pressure sensors [J]. Carbon, 2017, 114: 209-216.) under large strain.

[0050] Figure 5 The time corresponding graph of the flexible sensor of Example 1 of the present application.

[0051] Figure 6 The sensitivity graph of the flexible sensor of Example 1, 3 and 4 under 0 strain condition.

[0052] Figure 7 The physical map of the sensor electrode plate of Example 3.

[0053] Figure 8 The physical map of the sensor electrode plate of Example 5.

[0054] Figure 9 The physical map of the sensor electrode plate of Comparative Example 2.

[0055] In the figure, 1-flexible substrate, 2-graphene layer, 3-molybdenum sulfide layer, 4-electrode, 5-encapsulation layer. DETAILED DESCRIPTION

[0056] The present application will be described in detail below with reference to examples. It should be noted that the examples in the present application and the features in the examples can be combined with each other without conflict.

[0057] Example 1

[0058] The preparation method of the flexible sensor of the present embodiment includes the following steps:

[0059] S1: Put the PDMS substrate into deionized water and wash it clean, dry and reserve.

[0060] S2: Repeat the method of vacuum filtration to form a sensor electrode plate of graphene oxide and MoS2 on the filter membrane (diameter 50 mm, pore size 0.45 μm water-based microporous filter membrane). The specific preparation method of the sensor electrode plate includes the following steps:

[0061] S21: Ultrasonically disperse graphene oxide in water to prepare a water dispersion with a concentration of 1 mg / mL, pour 4 mL of the water dispersion into the vacuum filtration device (the range of vacuum filtration and the size of the filter membrane are consistent, with a diameter of 50 mm), and turn on the vacuum filtration machine (air suction speed: 10 m3 / h) 5 min to make the graphene oxide uniformly cover on the filter membrane to form a dense graphene oxide layer.

[0062] S22: Ultrasonic dispersion of few-layer MoS2 in water to make a dispersion of 1 mg / mL, pour 4 mL of the water dispersion into the vacuum filtration device, open the vacuum filtration machine to filter (air speed: 10 m 3 / h) 10 min to make the MoS2 uniformly cover on the graphene oxide layer to form a dense MoS2 layer.

[0063] S23: Repeat S21 once to obtain a sensor electrode plate on the filter membrane, which is stacked from bottom to top by a graphene oxide layer, a MoS2 layer and a graphene oxide layer.

[0064] S3: Immersing the sensor electrode plate together with the filter membrane into an ethanol solution to transfer the sensor electrode plate on the filter paper to the PDMS substrate by solution method.

[0065] S3: Uniformly spin-coating silver paste (SPI conductive silver paste 31 g, same below) on both sides of the sensor electrode plate, and drying in a vacuum drying oven to form silver electrodes on both sides of the sensor electrode plate.

[0066] S4: Packaging the sensor electrode plate and silver electrode part by VHB tape to obtain a flexible sensor.

[0067] Under standard test conditions, the sensor response time measured in the pressure range of 0-20 kPa is 0.012 s, and the sensor sensitivity is 1.2 kPa -1 Under the test condition of a large strain of 63.33%, the sensor sensitivity can still reach 0.25 kPa -1 , and the capacitance of the sensor electrode plate is 0.64 pF.

[0068] Example 2

[0069] The preparation method of the flexible sensor of the present embodiment comprises the following steps:

[0070] S1: Putting the PDMS substrate into deionized water to clean, and drying for standby.

[0071] S2: Repeating the method of vacuum filtration to make graphene oxide and MoS2 form a sensor electrode plate on the filter membrane (water-based microporous filter membrane with a diameter of 50 mm and a pore size of 0.45 μm), and the specific preparation method of the sensor electrode plate comprises the following steps:

[0072] S21: ultrasonic dispersion of graphene oxide in water to make a water dispersion with a concentration of 0.5 mg / mL, pour 4 mL of the water dispersion into a vacuum filtration device (the range of vacuum filtration and the size of the filter membrane are consistent, with a diameter of 50 mm), turn on the vacuum filtration machine (exhaust speed: 10 m 3 / h) for 5 min to make the graphene oxide uniformly cover the filter membrane to form a dense graphene oxide layer.

[0073] S22: ultrasonic dispersion of few-layer MoS2 in water to make a dispersion with a concentration of 2 mg / mL, pour 4 mL of the water dispersion into a vacuum filtration device, turn on the vacuum filtration machine (exhaust speed: 10 m 3 / h) for 10 min to make the MoS2 uniformly cover the graphene oxide layer to form a dense MoS2 layer.

[0074] S23: repeat S21 once to obtain a sensor electrode plate on the filter membrane, which is stacked from bottom to top by a graphene oxide layer, a MoS2 layer and a graphene oxide layer, see Figure 2 .

[0075] S3: immerse the sensor electrode plate together with the filter membrane in an ethanol solution, and use the solution method to transfer the sensor electrode plate on the filter paper to a PDMS substrate.

[0076] S3: uniformly spin-coat silver paste on both sides of the sensor electrode plate, and place it in a vacuum drying oven for drying, to form silver electrodes on both sides of the sensor electrode plate.

[0077] S4: encapsulate the sensor electrode plate and the silver electrode part by using a VHB adhesive tape, to obtain a flexible sensor.

[0078] Under standard test conditions, the sensor response time measured in the pressure range of 0-20 kPa is 0.012 s, and the sensor sensitivity is 1.2 kPa -1 , and the sensor sensitivity under a large strain of 63% can still reach 0.25 kPa -1 (calculated from the sensitivity curve under 63% strain), and the capacitance of the sensor electrode plate is 0.35 pF. Figure 3

[0079] It can be seen that the sensor electrode plate of the capacitive flexible sensor prepared by the application is vertically stacked by a dense graphene oxide layer and a MoS2 layer. Figure 2

[0080] Figure 3 and Figure 4 ​​The sensitivity change of the flexible sensor of the embodiment 1 of the present application under large strain and the sensitivity change of the traditional structure capacitive sensor are shown in the figure, from which it can be directly seen that with the increase of the strain, the limit value of the sensor sensitivity failure of the embodiment is 73%, and the limit value of the traditional sensor is 53%, obviously, the limit value of the sensor sensitivity failure of the present application is much greater than that of the traditional structure capacitive sensor.

[0081] It can be seen that the response time of the flexible sensor prepared in the embodiment 1 of the present application is 100ms, and the response speed is good. Figure 4

[0082] Comparative example 1

[0083] The embodiment 1 is repeated, and the difference is that the molybdenum sulfide layer is prepared on the filter membrane first.

[0084] It is found that the peeling of the electrode plate from the filter membrane is difficult in the transfer process of S3.

[0085] Embodiment 3

[0086] The embodiment 1 is repeated, and the difference is that the water dispersion of graphene oxide in the embodiment is poured into 3mL each time, and the water dispersion of MoS2 is poured into 1mL.

[0087] Embodiment 4

[0088] The embodiment 1 is repeated, and the difference is that:

[0089] The water dispersion of graphene oxide in the embodiment is poured into 5mL each time, and the water dispersion of MoS2 is poured into 1mL.

[0090] It can be seen that through the comparison of the embodiments 1, 3 and 4, under the condition of 0 strain, the different thicknesses of the graphene oxide and MoS2 layers will cause the sensitivity of the sensor to change to a certain extent. Figure 6 Embodiment 5

[0091] The embodiment 3 is repeated, and the difference is that:

[0092] The vacuum filtration speed of the vacuum filtration machine in the embodiment is 8m 3 / h.

[0093] Comparative example 2

[0094] The embodiment 3 is repeated, and the difference is that the vacuum filtration speed of the vacuum filtration machine in the embodiment is 7m 3 / h.

[0095] It can be seen that through the comparison of the embodiments 1, 3 and 4, under the condition of 0 strain, the different thicknesses of the graphene oxide and MoS2 layers will cause the sensitivity of the sensor to change to a certain extent.

[0096] Figures 7-9 ​​It can be seen that when the speed of suction filtration fails to reach the required speed of the experiment, the prepared sensor electrode plate becomes uneven and not dense.

[0097] The above examples are intended to be illustrative only and should not be used to limit the scope of the invention, which is defined by the claims appended hereto. Modifications of the invention in its various aspects will occur to those skilled in the art to which the invention pertains and such modifications are deemed to fall within the scope of the claims.

Claims

1. A method for preparing a sensor plate, characterized in that: The steps include: S1. Pour the aqueous dispersion of graphene oxide into a vacuum filter, filter, and obtain a graphene layer on the filter membrane of the vacuum filter; S2, pouring the aqueous dispersion of molybdenum sulfide into the vacuum filter, filtering, and forming a molybdenum sulfide layer on the surface of the graphene layer; S3, repeat S1 and S2 as needed to obtain a sensor plate on the filter membrane; S4, soaking the sensor plate and the filter membrane in an organic solvent, and separating the sensor plate and the filter membrane; The sensor plate includes at least one graphene layer and at least one molybdenum sulfide layer, the graphene layer is composed of graphene oxide, and the graphene layer and the molybdenum sulfide layer are stacked on each other to form a layered structure; the total number of graphene layers and molybdenum sulfide layers is ≥3 layers, and the graphene layers and molybdenum sulfide layers are stacked alternately; the concentration of graphene oxide in the aqueous dispersion of graphene oxide is 0.5-3 mg / mL; the concentration of molybdenum sulfide in the aqueous dispersion of molybdenum sulfide is 0.5-3 mg / mL; in S1, 3-6 mL of the aqueous dispersion of graphene oxide is poured into the vacuum filter; in S2, 1-6 mL of the aqueous dispersion of molybdenum sulfide is poured into the vacuum filter; during filtration, the suction speed is controlled to 8-10 m 3 / h.

2. The preparation method according to claim 1, characterized in that The thickness of the graphene layer is 2-10 μm; the thickness of the molybdenum sulfide layer is 2-10 μm.

3. The preparation method according to claim 2, characterized in that The thickness of the graphene layer is 4-8 μm; the thickness of the molybdenum sulfide layer is 4-8 μm.

4. The preparation method according to claim 1, characterized in that The thickness of the molybdenum sulfide layer is 1-4 times that of the graphene layer.

5. The preparation method according to claim 4, characterized in that The thickness of the molybdenum sulfide layer is 1.5-3.5 times that of the graphene layer.

6. The preparation method according to any one of claims 1 to 5, characterized in that The total number of graphene layers and molybdenum sulfide layers is 3-5 layers.

7. The preparation method according to claim 1, characterized in that The molybdenum sulfide is a few-layer molybdenum sulfide.

8. The preparation method according to claim 7, characterized in that The filter membrane is circular with a diameter of 40-60 mm, and the filtration range is consistent with the size of the filter membrane.

9. The preparation method according to claim 7, characterized in that In S4, the organic solvent is one or more of ethanol, methanol, and ether.

10. The preparation method according to claim 7, characterized in that The filter membrane is a microporous filter membrane.

11. The preparation method according to claim 10, characterized in that: The filter membrane is a water-based microporous filter membrane.

12. A flexible sensor comprising a flexible substrate, characterized in that: The flexible substrate is provided with a sensor plate prepared by the preparation method according to any one of claims 1 to 11.

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