Long-life flexible pressure sensor based on PDMS insulating layer packaging structure and preparation method thereof

Abstract

The invention discloses a long-life flexible pressure sensor based on a PDMS insulating layer packaging structure. The long-life flexible pressure sensor comprises a packaging layer, a nano conductive layer, a flexible substrate layer and a flexible electrode, the packaging layer, the nano conductive layer and the flexible substrate layer are arranged in sequence; the flexible substrate layer is filled with a conductive nano material; a flexible electrode is arranged on the nano conductive layer; the flexible substrate layer is sensitive to pressure and is used for generating corresponding electric signal changes when the flexible substrate layer is pressed, and therefore pressure detection is achieved. And the nano conductive layer is temperature-sensitive and is used for realizing temperature detection. According to the scheme, a flexible substrate and a conductive nano material are mixed to form a filling type composite conductive material with a conductive network inside, a pressure sensitive unit is sealed through pouring of a PDMS solution, and an insulation packaging layer is attached to the surface to prevent air from penetrating through gaps of a PDMS layer to make contact with a pressure sensitive layer to cause aging; the sensor is low in production cost, large-area tactile perception can be achieved, and different pressure detection sensitivities can be obtained by adjusting the content of the conductive phase material so as to adapt to different application scenes.

Description

Technical Field

[0001] The invention belongs to the field of flexible tactile sensor packaging, and in particular relates to a long-life flexible pressure sensor based on a PDMS insulating layer packaging structure and a preparation method thereof. Background Art

[0002] As an innovative achievement in the intersection of smart materials and biomedical engineering, electronic skin has a far-reaching impact on the fields of smart wearable devices, human-computer interaction technology, and medical auxiliary equipment. As an important research direction of electronic skin research, flexible tactile sensors can not only simulate the response of real skin to external stimuli, but also provide robots with a perception ability beyond vision through advanced sensing technology. The development of this composite sensor has immeasurable scientific significance and practical application value for robots' autonomous navigation, fine operation, and more natural interaction with humans in complex environments.

[0003] With the in-depth exploration of applications and the continuous improvement of production and preparation processes, higher requirements have been put forward for flexible tactile sensors used in human-computer interaction in terms of functional structure and long service life. Flexible tactile sensors with the characteristics of high ductility, wearing comfort, high sensitivity, real-time temperature measurement, and long service life have become the current key research direction. Traditional silicon-based and metal strain gauge pressure sensors cannot meet the functional requirements of flexibility, ductility, and wearing comfort. Therefore, force-sensitive filling composite conductive materials obtained by mixing nano-conductors with organic macromolecular materials are widely used in the preparation of flexible tactile sensors.

[0004] According to the working principle, flexible pressure sensors can be divided into several categories, such as capacitive, resistive, piezoelectric, and triboelectric. Among them, capacitive flexible pressure sensors can detect static and dynamic forces, and have fast response, high sensitivity and accuracy. However, there may be disadvantages of high cost and complex detection circuits. They are widely used in the industrial field to measure fluid pressure, temperature, flow and other parameters. Piezoelectric pressure sensors have a fast response speed and are suitable for measuring dynamic pressure. They have the advantage of not requiring an external power supply, but it is difficult to measure static pressure. Triboelectric flexible pressure sensors also have self-driving characteristics, but because they rely on the triboelectric effect generated when two surfaces of different materials come into contact to perform pressure detection, their stability and durability are often not high.

[0005] The piezoresistive flexible pressure sensor based on filled composite conductive materials has low cost, but has defects such as low sensitivity, short service life and inability to measure temperature. Problems such as low sensitivity can be solved by setting microstructures in the tactile sensitive layer. Common microstructures include pyramid type, microsphere type, hollow type, etc. Usually, complex processes are required to prepare microstructures, such as photolithography, sputtering, evaporation, etching, etc., and there are disadvantages such as difficulty in large-scale production.

[0006] The short life of piezoresistive flexible pressure sensors with filled composite conductive materials as pressure-sensitive end elements is mainly caused by the following factors: material aging - since the pressure-sensitive unit is exposed to the air and is often loose and porous, the various materials inside react physically and chemically with the various components in the air; interface stability issues - long-term stress may cause separation or failure of the interfaces inside the force-sensitive unit, affecting the long-term reliability of the sensor.

[0007] Interface modification can solve the problem of interface stability inside the force-sensitive unit. The surface of the conductive filler can be modified by using a coupling agent or surfactant to increase its compatibility and bonding with the polymer matrix. Or a stable coating can be formed on the surface of the conductive molecule by chemical or physical methods to improve its bonding strength with the matrix. However, material aging always restricts the long-term application of flexible pressure sensors. Summary of the invention

[0008] In view of the above problems, an object of the present invention is to provide a long-life flexible pressure sensor based on a PDMS insulating layer packaging structure and a preparation method thereof.

[0009] The specific technical solution for achieving the purpose of the present invention is:

[0010] A long-life flexible pressure sensor based on a PDMS insulating layer packaging structure, comprising a packaging layer, a nano conductive layer, a flexible substrate layer and a flexible electrode;

[0011] The encapsulation layer, the nano-conductive layer and the flexible substrate layer are arranged in sequence;

[0012] The flexible substrate layer is filled with conductive nanomaterials;

[0013] A flexible electrode is arranged on the nano conductive layer;

[0014] Wherein, the flexible substrate layer is pressure sensitive and is used to generate corresponding electrical signal changes when subjected to pressure, thereby realizing pressure detection;

[0015] The nano conductive layer is temperature sensitive and is used to realize temperature detection.

[0016] Further, the encapsulation layer includes a first encapsulation layer, a second encapsulation layer, a third encapsulation layer, and a fourth encapsulation layer;

[0017] The first packaging layer, the second packaging layer, the third packaging layer and the fourth packaging layer are arranged in sequence from bottom to top, wherein the flexible substrate layer is arranged between the second packaging layer and the third packaging layer, and the nano conductive layer is arranged between the third packaging layer and the fourth packaging layer.

[0018] Furthermore, the second encapsulation layer and the third encapsulation layer are made of PDMS thin film material;

[0019] The first encapsulation layer and the fourth encapsulation layer are made of polyethylene or polyethylene terephthalate material.

[0020] Furthermore, the conductive nanomaterial is graphite, carbon black, carbon nanotube or graphene material;

[0021] The flexible base layer is made of high molecular weight organic silicon compound or silicone rubber material.

[0022] Furthermore, the nano conductive layer is prepared by using nano silver particles and nano gold particles.

[0023] The present invention also provides a method for preparing the above sensor, comprising the following steps:

[0024] Step 1, preparing an encapsulation layer;

[0025] Step 2, preparing a nano conductive layer;

[0026] Step 3, preparing a flexible base layer;

[0027] Step 4: Prepare a long-life flexible pressure sensor based on a PDMS insulating layer packaging structure.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The flexible substrate layer in the sensor of the present invention is a pressure-sensitive layer, which is the core part of the sensor and is composed of a filled composite conductive material obtained by mixing conductive nanomaterials with a flexible substrate. This material is selected to ensure that the sensor can produce obvious electrical signal changes when subjected to pressure, thereby realizing pressure detection. In addition, the nano-conductive layer is a temperature-sensitive layer, which is located above the pressure-sensitive layer and is composed of a fractal pattern of nano-silver or gold particles solidified on PDMS (polydimethylsiloxane). This design enables the sensor to measure temperature by detecting resistance changes caused by temperature changes. Finally, in order to improve the stability and durability of the sensor, a solidified PDMS solution is poured around the pressure-sensitive layer to form a solid package. In addition, the upper and lower surfaces of the pressure-sensitive layer are also covered with a PDMS film, which further enhances the structural stability of the sensor. The present invention combines conductive nanomaterials with a flexible substrate, so that the sensor has high sensitivity to tiny pressure changes and accurate temperature measurement capabilities.

[0030] (2) The sensor of the present invention can detect pressure and temperature changes simultaneously through the coordinated work of the pressure sensitive layer and the temperature sensitive layer, thereby realizing a multimodal sensing function. At the same time, PDMS is used as the main packaging material, which not only provides good mechanical stability but also has excellent chemical stability and biocompatibility, thereby extending the service life of the sensor;

[0031] (3) The present invention uses common chemical material vulcanized silicone rubber as a substrate, carbon nanoparticles as nano-conductive fillers, and PDMS and PE polyester films to prepare a composite packaging structure. The materials used are low-cost and can well meet the requirements of electronic skin for flexibility, comfortable wearability, and large-area tactile perception. The flexible tactile sensor of the filled composite conductive material provided by the present invention forms a conductive network by compounding carbon nanoparticles and vulcanized silicone rubber. The sensitivity of the force-sensitive sensing unit can be controlled by controlling the content of carbon nanoparticles. At the same time, the vulcanized silicone rubber is used as a non-conductive phase, so that the entire sensing unit has good flexibility and temperature and humidity stability.

[0032] (4) The present invention adopts a liquid phase preparation method in the preparation of overshoot, by uniformly mixing the various components in liquid state and then applying them to the prepared mold, and then completing the final preparation through high-temperature curing, thereby reducing the preparation cost, simplifying the process flow, and having the advantage of large-scale preparation.

[0033] The present invention is further described below in conjunction with specific implementation modes. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the structure of a long-life flexible pressure sensor based on a PDMS insulating layer packaging structure of the present invention.

[0035] Figure 2 The figure is a schematic diagram of the process of preparing the flexible substrate layer of the present invention.

[0036] Figure 3 It is a schematic diagram of the preparation process of the PDMS encapsulation layer of the present invention.

[0037] Figure 4 It is a schematic diagram of the process of preparing the nano conductive layer of the present invention.

[0038] Figure 5 A schematic diagram of a mold that specifies dimensions for a flexible pressure sensor in an embodiment of the present invention.

[0039] Figure 6 This is a physical picture of the flexible pressure sensor in an embodiment of the present invention.

[0040] Figure 7 This is a fractal graphic design diagram of the flexible temperature sensor in an embodiment of the present invention.

[0041] Figure 8 This is a resistance and pressure test curve obtained by testing the flexible pressure sensor in an embodiment of the present invention. DETAILED DESCRIPTION

[0042] Example

[0043] In order to clearly describe the technical solution and the effects achieved by the present invention, the technical solution of the present invention is clearly explained below in combination with the accompanying drawings and specific embodiments of the present invention, so that technical personnel in the field can implement the invention without performing creative work. The structure shown in the accompanying drawings is not the entire actual structure but only a part of the actual structure. It should be noted that all other embodiments made by ordinary technical personnel in the field on the basis of the embodiments of the present invention without performing creative work should fall within the protection scope of the present invention.

[0044] The following examples are only for better explanation of the present invention, but the content of the present invention is not limited to the application in the examples. Therefore, those skilled in the art can make non-essential modifications to the implementation scheme based on the above invention content and apply it to other embodiments, which is still within the protection scope of the present invention. In addition, the experimental methods without specific conditions in the following examples should be carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the expressions in the text are not specially explained, they are only used for distinction and have no other meanings.

[0045] In order to reduce production costs and achieve large-area tactile perception, a flexible substrate is mixed with conductive nanomaterials to form a filled composite conductive material with a conductive network inside. The pressure-sensitive unit is sealed by casting with PDMS solution, and an insulating packaging layer is attached to the surface to prevent air from passing through the gaps in the PDMS layer and contacting the pressure-sensitive layer, causing aging. The sensor can adjust the content of the conductive phase material to obtain different pressure detection sensitivities to adapt to different application scenarios.

[0046] Combination Figure 1 , a long-life flexible pressure sensor based on a PDMS insulating layer packaging structure, comprising a packaging layer, a nano conductive layer, a flexible substrate layer and a flexible electrode;

[0047] The encapsulation layer, the nano-conductive layer and the flexible substrate layer are arranged in sequence;

[0048] The flexible substrate layer is filled with conductive nanomaterials;

[0049] Flexible electrodes are arranged on the nano conductive layer and the flexible substrate layer;

[0050] Wherein, the flexible substrate layer is pressure sensitive and is used to generate corresponding electrical signal changes when subjected to pressure, thereby realizing pressure detection;

[0051] The nano conductive layer is temperature sensitive and is used to detect temperature;

[0052] The temperature-sensitive nano-conductive layer is arranged on the pressure-sensitive flexible substrate layer, and the two are isolated by a flexible packaging layer, and then an insulating packaging layer is arranged outside to isolate the sensor from the outside.

[0053] In addition, the flexible electrode can be made of 12-core conductive copper wire, which is embedded around the flexible substrate layer made of force-sensitive filled composite conductive material. Such an electrode design helps to improve the electrical signal transmission efficiency and stability of the sensor;

[0054] In addition, electrodes are also set around the edges of the nano-conductive layer. Copper foil coated with nano-silver material can be used, and the nano-silver particles are fixed to the end of the temperature sensitive layer. This electrode design helps to improve the accuracy and response speed of temperature measurement.

[0055] More specifically, the encapsulation layer includes a first encapsulation layer, a second encapsulation layer, a third encapsulation layer, and a fourth encapsulation layer;

[0056] The first packaging layer, the second packaging layer, the third packaging layer, and the fourth packaging layer are arranged in sequence from bottom to top, wherein the flexible substrate layer is arranged between the second packaging layer and the third packaging layer, the nano-conductive layer is arranged between the third packaging layer and the fourth packaging layer, and the flexible substrate layer and the nano-conductive layer are tightly attached to both sides of the third packaging layer.

[0057] The second packaging layer and the third packaging layer are made of PDMS thin film material, which not only provides good mechanical stability, but also has excellent chemical stability and biocompatibility, thereby extending the service life of the sensor; the first packaging layer and the fourth packaging layer are made of polyethylene or polyethylene terephthalate material, which further enhances the structural stability of the sensor.

[0058] The conductive nano material is graphite, carbon black, carbon nanotube or graphene material; the flexible base layer is prepared by high molecular organic silicon compound or silicone rubber material.

[0059] The nano conductive layer is prepared by using nano silver particles and nano gold particles, and is generally prepared by using nano silver particle ink.

[0060] The present invention also provides a method for preparing the above sensor, comprising the following steps:

[0061] Step 1, preparing the encapsulation layer, that is, the second encapsulation layer and the third encapsulation layer are made of PDMS film;

[0062] The flexible PDMS solution and the curing agent were mixed in a ratio of 10:1, stirred evenly, and placed in a vacuum tube furnace for 30 minutes to remove bubbles. The solution was then poured into the corresponding mold, allowed to stand for 10 minutes until it flowed smoothly, and placed on a heating platform for 100°C and heated for 10 minutes to cure, thereby forming the second and third encapsulation layers, namely the flexible PDMS encapsulation layers.

[0063] Step 2: Preparation of nano-conductive layer:

[0064] Using nano silver particle ink or nano gold particle ink to print a pre-set pattern on the PDMS film substrate corresponding to the third encapsulation layer 3 to 4 times until the narrowest part of the fractal pattern is greater than 2 mm, the printing adopts an electrostatic jet method;

[0065] The PDMS film substrate of the third encapsulation layer printed with nano silver particle ink or nano gold particle ink is heated to solidify the nano silver particle ink or nano gold particle ink, the heating temperature is 175° C. to 250° C., and the heating time is 30 min to 90 min;

[0066] A copper foil conductor is led out from the end of the conductive pattern formed by electrostatic spraying, and two conductors are led out to serve as electrodes of the nano conductive layer.

[0067] Step 3: Prepare a flexible substrate layer:

[0068] Step 3-1, prepare a flexible substrate solution, take room temperature vulcanized silicone rubber: dimethyl silicone oil: tetraethyl silicate: dibutyltin dilaurate in a mass ratio of 40:4:2:1, put them in a test tube and mix them evenly;

[0069] Step 3-2: Add conductive nanomaterials into the flexible substrate solution, the mass ratio of the flexible substrate material to the conductive nanomaterials being 5:1, mix them in proportion, and stir evenly to obtain a force-sensitive filled composite conductive material, i.e., a flexible substrate layer.

[0070] Step 4: Prepare a long-life flexible pressure sensor based on a PDMS insulating layer packaging structure:

[0071] The prepared PDMS film corresponding to the second encapsulation layer is used as a substrate, a corresponding mold is arranged on the substrate, and the flexible substrate solution doped with conductive nanomaterials prepared in step 3 is poured into the mold;

[0072] Before the flexible substrate solution is solidified, the copper core conductor and the flexible substrate solution are fixed by using a mold;

[0073] The PDMS film corresponding to the third encapsulation layer prepared with the nano-conductive layer in step 2 is cut into the required size and applied to the surface of the mold, so that the PDMS film is attached to the upper and lower surfaces of the flexible substrate doped with the conductive nano-material to slow down oxidation;

[0074] Afterwards, the mold with the flexible substrate layer was left to stand for 72 hours under heavy pressure to allow the flexible substrate layer to fully solidify;

[0075] Lay the flexible base layer flat after curing, remove the surrounding molds, and keep the flexible base layer;

[0076] PDMS solution was injected into the PDMS gaps around the flexible substrate layer, with the thickness controlled at about 1 mm, and then placed on a heating table and heated and dried at 100°C for 5 minutes to achieve PDMS material wrapping the flexible substrate layer;

[0077] The prepared first packaging layer and fourth packaging layer are cut into suitable sizes, and are respectively pasted under the PDMS film corresponding to the second packaging layer and on the nano-conductive layer to complete the preparation of the sensor.

[0078] like Figure 2 As shown in the figure, the preparation process of the flexible substrate layer is shown. According to the mold volume, 8g of vulcanized silicone rubber, 0.4g of dimethyl silicone oil, 0.2g of tetraethyl silicate, and 0.1g of dibutyltin dilaurate are required. After weighing the above materials, pour them into a beaker and stir in the same direction for 5 minutes to ensure that the components are fully mixed. Then weigh 1.6g of carbon black powder according to a mass ratio of 20%, add it to the beaker, and stir again for 10 minutes to ensure that the carbon black powder is evenly dispersed in the rubber substrate. To ensure that a complete conductive network is formed inside the device.

[0079] like Figure 3 As shown in the figure, the preparation process of the PDMS film corresponding to the second and third encapsulation layers is demonstrated. The flexible PDMS solution and the curing agent are mixed in a ratio of 10:1, stirred evenly and placed in a vacuum tube furnace for 20 minutes to remove bubbles. The solution is then poured into the mold for leveling, placed on a heating platform for heating at 90°C for 30 minutes to cure, and the second and third encapsulation layers are formed.

[0080] like Figure 4 As shown in the figure, the preparation process of the conductive nanolayer is demonstrated. The designed fractal design pattern is imported into the human-computer interaction platform, and the nanosilver ink is sprayed on the third packaging layer, that is, the PDMS film, by electrostatic spraying. The PDMS film with the pre-designed pattern is heated to solidify the nanosilver ink. The heating temperature is 175℃~250℃, and the heating time is 30min~90min;

[0081] like Figure 5As shown in the figure, a schematic diagram of a mold of a specified size for a flexible pressure sensor is shown. The prepared PDMS film is laid flat on the prepared glass plate or acrylic plate substrate, and the glass slide is cut as required to enclose a rectangular space of 75mm×75mm×1mm. A gap is left in the middle of both ends of the rectangle for placing electrodes. The electrodes are made of multi-strand copper wires, and the ends are coiled into a circular coil to ensure full contact between the electrodes and the sensing material.

[0082] like Figure 6 As shown, this is a fractal graphic design diagram of the flexible temperature sensor in this implementation example. In order to prevent the flexible temperature sensor from breaking under external pressure, we design the temperature sensor into a snake shape, which improves the tensile strength while also increasing the temperature sensing area.

[0083] Figure 7 Schematic diagram of a long-life flexible pressure sensor based on a PDMS insulating layer packaging structure prepared in this embodiment. Figure 8 The resistance and pressure test curves obtained by testing the flexible pressure sensor prepared in this embodiment show that the flexible pressure sensor under this packaging structure exhibits good sensitivity within 70 days.

[0084] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A long-life flexible pressure sensor based on a PDMS insulating layer packaging structure, characterized in that: It includes a packaging layer, a nano conductive layer, a flexible substrate layer and a flexible electrode; The encapsulation layer, the nano-conductive layer and the flexible substrate layer are arranged in sequence; The flexible substrate layer is filled with conductive nanomaterials; A flexible electrode is arranged on the nano conductive layer; Wherein, the flexible substrate layer is pressure sensitive and is used to generate corresponding electrical signal changes when subjected to pressure, thereby realizing pressure detection; The nano conductive layer is temperature sensitive and is used to realize temperature detection.

2. The long-life flexible pressure sensor based on the PDMS insulating layer packaging structure according to claim 1 is characterized in that: The encapsulation layer comprises a first encapsulation layer, a second encapsulation layer, a third encapsulation layer, and a fourth encapsulation layer; The first packaging layer, the second packaging layer, the third packaging layer and the fourth packaging layer are arranged in sequence from bottom to top, wherein the flexible substrate layer is arranged between the second packaging layer and the third packaging layer, and the nano conductive layer is arranged between the third packaging layer and the fourth packaging layer.

3. The long-life flexible pressure sensor based on the PDMS insulating layer packaging structure according to claim 2 is characterized in that: The second encapsulation layer and the third encapsulation layer are made of PDMS thin film material; The first encapsulation layer and the fourth encapsulation layer are made of polyethylene or polyethylene terephthalate material.

4. The long-life flexible pressure sensor based on the PDMS insulating layer packaging structure according to claim 2 is characterized in that: The conductive nanomaterial is graphite, carbon black, carbon nanotube or graphene material; The flexible base layer is made of high molecular weight organic silicon compound or silicone rubber material.

5. The long-life flexible pressure sensor based on the PDMS insulating layer packaging structure according to claim 2, characterized in that: The nano conductive layer is prepared by using nano silver particles and nano gold particles.

6. The method for preparing the sensor according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1, preparing an encapsulation layer; Step 2, preparing a nano conductive layer; Step 3, preparing a flexible base layer; Step 4: Prepare a long-life flexible pressure sensor based on a PDMS insulating layer packaging structure.

7. The preparation method according to claim 6, characterized in that: The preparation of the encapsulation layer in step 1 is specifically as follows: The flexible PDMS solution and the curing agent were mixed in a ratio of 10:1, stirred evenly, and placed in a vacuum tube furnace for 30 minutes to remove bubbles. The solution was then poured into the corresponding mold, allowed to stand for 10 minutes until it flowed smoothly, and placed on a heating platform for 100°C and heated for 10 minutes to cure, thereby forming the second and third encapsulation layers, namely the flexible PDMS encapsulation layers.

8. The preparation method according to claim 6, characterized in that: The step 2 of preparing the nano conductive layer is specifically as follows: Using nano silver particle ink or nano gold particle ink to print a pre-set pattern on the PDMS film substrate corresponding to the third encapsulation layer 3 to 4 times until the narrowest part of the fractal pattern is greater than 2 mm, the printing adopts an electrostatic jet method; The PDMS film substrate of the third encapsulation layer printed with nano silver particle ink or nano gold particle ink is heated to solidify the nano silver particle ink or nano gold particle ink, the heating temperature is 175° C. to 250° C., and the heating time is 30 min to 90 min; A copper foil conductor is led out from the end of the conductive pattern formed by electrostatic spraying, and two conductors are led out to serve as electrodes of the nano conductive layer.

9. The preparation method according to claim 6, characterized in that: The preparation of the flexible base layer in step 3 is specifically as follows: Step 3-1, prepare a flexible substrate solution, take room temperature vulcanized silicone rubber: dimethyl silicone oil: tetraethyl silicate: dibutyltin dilaurate in a mass ratio of 40:4:2:1, put them in a test tube and mix them evenly; Step 3-2: Add conductive nanomaterials into the flexible substrate solution, the mass ratio of the flexible substrate material to the conductive nanomaterials being 5:1, mix them in proportion, and stir evenly to obtain a force-sensitive filled composite conductive material, i.e., a flexible substrate layer.

10. The preparation method according to claim 6, characterized in that: The preparation of the long-life flexible pressure sensor based on the PDMS insulating layer packaging structure in step 4 is specifically as follows: The prepared PDMS film corresponding to the second encapsulation layer is used as a substrate, a corresponding mold is arranged on the substrate, and the flexible substrate solution doped with conductive nanomaterials prepared in step 3 is poured into the mold; Before the flexible substrate solution is solidified, the copper core conductor and the flexible substrate solution are fixed by using a mold; The PDMS film corresponding to the third encapsulation layer prepared with the nano-conductive layer in step 2 is cut into the required size and applied to the surface of the mold, so that the PDMS film is attached to the upper and lower surfaces of the flexible substrate doped with the conductive nano-material; Afterwards, the mold with the flexible substrate layer was left to stand for 72 hours under heavy pressure to allow the flexible substrate layer to fully solidify; Lay the flexible base layer flat after curing, remove the surrounding molds, and keep the flexible base layer; PDMS solution was injected into the PDMS gaps around the flexible substrate layer, with the thickness controlled at about 1 mm, and then placed on a heating table and heated and dried at 100°C for 5 minutes to achieve PDMS material wrapping the flexible substrate layer; The prepared first packaging layer and fourth packaging layer are cut into suitable sizes, and are respectively pasted under the PDMS film corresponding to the second packaging layer and on the nano-conductive layer to complete the preparation of the sensor.

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