Flexible sensor with gradient hollow pyramid microstructure and preparation method thereof

Abstract

The invention discloses a flexible sensor with a gradient hollow pyramid microstructure and a preparation method thereof, relates to the technical field of flexible sensing, effectively improves the sensitivity and linearity of the flexible sensor, and realizes the measurement of tangential force by using a tangential anisotropic structure. An upper-layer insulating flexible substrate, an upper-layer copper foil electrode, a dielectric layer, a flexible gasket, a lower-layer copper foil electrode and a lower-layer insulating flexible substrate are connected in sequence; a plurality of pyramid structures are arranged on the dielectric layer, and the pyramid structures are hollow structures; the dielectric layer is made of hydrogel. According to the invention, a hollow pyramid microstructure is manufactured by using the super-strong conformal capability of the dehydrated hydrogel, the mechanical modulus is further reduced and the sensitivity is improved while the stable performance is ensured, so that the deformation capabilities in the X-axis direction and the Y-axis direction are different, and the measurement of the normal force and the tangential forces in the X-axis direction and the Y-axis direction can be realized.

Description

Technical Field

[0001] The present invention relates to the field of flexible sensing technology, in particular to a flexible sensor with a gradient hollow pyramid microstructure and a preparation method thereof. Background Art

[0002] Flexible sensor technology has developed rapidly, encompassing the detection of a wide range of physical, chemical, and biological signals, and is widely used in fields such as health monitoring, smart wearables, and environmental sensing. Materials used include nanomaterials such as graphene and carbon nanotubes, as well as flexible substrates such as hydrogels and organic polymers. These materials have significantly improved sensor sensitivity, flexibility, and stretchability. In sensor manufacturing, the integration of micro-nanofabrication and printing technologies has promoted sensor miniaturization and integration, reducing production costs and improving efficiency. Currently, flexible sensors can accurately monitor various human physiological indicators such as heart rate, blood pressure, and body temperature. They can also provide real-time monitoring of multiple parameters such as environmental gases, humidity, and pressure, providing important technical support for related fields. However, flexible sensors based on non-gel flexible materials generally suffer from low sensitivity and poor linearity. Flexible sensors based on gel materials often use ion gels as the dielectric layer. While this significantly improves sensor sensitivity, it also suffers from inherent issues such as susceptibility to dehydration and unstable performance. Summary of the Invention

[0003] To address the aforementioned issues of low sensitivity, poor linearity, and unstable performance in flexible sensors, this invention proposes a flexible sensor with a gradient hollow pyramid microstructure and a method for its fabrication. This method leverages the exceptional conformability of dehydrated hydrogels to create a hollow pyramid microstructure. While ensuring stable performance, it further reduces the mechanical modulus and improves sensitivity, creating differential deformation in the X- and Y-axis directions, enabling measurement of normal force as well as X- and Y-axis tangential forces.

[0004] The present invention proposes a flexible sensor with a gradient hollow pyramid microstructure with tangential anisotropy, which specifically includes an upper insulating flexible substrate, an upper copper foil electrode, a dielectric layer, a flexible gasket, a lower copper foil electrode and a lower insulating flexible substrate. The upper insulating flexible substrate, the upper copper foil electrode, the dielectric layer, the flexible gasket, the lower copper foil electrode and the lower insulating flexible substrate are connected in sequence; a plurality of pyramid structures are arranged on the dielectric layer, and the top of the pyramid structure is connected to the upper copper foil electrode; the pyramid structure is a hollow structure.

[0005] Furthermore, a plurality of through holes are provided on two opposite surfaces of the pyramid structure.

[0006] Furthermore, the through holes on the surface of the pyramid structure increase in number from top to bottom.

[0007] Furthermore, the pyramid structure includes small pyramids and large pyramids, and the small pyramids and the large pyramids are arranged alternately.

[0008] Furthermore, the flexible gasket is annular and is arranged at the edge of the lower copper foil electrode.

[0009] A method for preparing the above-mentioned flexible sensor with a gradient hollow pyramid microstructure having tangential anisotropy comprises the following steps:

[0010] Step 1: Prepare the insulating flexible substrate: Use single-sided PET tape for the upper insulating flexible substrate, with the glued side attached to the copper electrode; use double-sided PET tape for the lower insulating flexible substrate, with one side of the double-sided PET tape attached to the copper electrode and the other side for mounting; cut the upper and lower insulating flexible substrates;

[0011] Step 2: Electrode layer preparation: The upper copper foil electrode and the lower copper foil electrode are made using copper foil tape, which is cut into squares.

[0012] Step 3: Preparation of dielectric layer: Print an initial mold using a 3D printer, prepare a PDMS mixture and pour it into the initial mold to solidify to obtain a molded mold; prepare a PVA mixture and pour it into the PDMS mold, dehydrate it to a semi-solid state, insert a fine needle, and then dehydrate it again to obtain a dielectric layer;

[0013] Step 4, sensor packaging: stick the glue side of the upper insulating flexible substrate to the glue side of the upper copper foil electrode; stick one side of the lower insulating flexible substrate to the glue side of the lower copper foil electrode; spray a layer of PDMS mixture on the edge of the upper copper foil electrode without glue, and spray a layer of PDMS mixture on the edge of the lower copper foil electrode; fit the flexible gasket to the edge of the lower copper foil electrode; spray a layer of PDMS mixture on the upper surface of the flexible gasket; fit the upper copper foil electrode to the top of the dielectric layer pyramid, fit the lower surface of the dielectric layer to the flexible gasket, and complete the preparation after curing.

[0014] Furthermore, the components of the PDMS mixed solution in step 3 are PDMS, curing agent and silicone oil, and the mass ratio is 20:1:2.

[0015] Furthermore, the components of the PVA mixed solution in step 3 are polyvinyl sorbitol 1799, deionized water and phosphoric acid solution, with a ratio of 6g:60ml:5ml.

[0016] Furthermore, the PDMS mixed solution coating in step 4 has a thickness of 100 μm.

[0017] Furthermore, in the step 2, the copper foil tape used for the upper copper foil electrode and the lower copper foil electrode has a thickness of 100 μm.

[0018] The flexible sensor with a gradient hollow pyramid microstructure and the preparation method thereof according to the present invention have the following beneficial effects:

[0019] (1) The flexible sensor with a gradient hollow pyramid microstructure and its preparation method described in the present invention utilize the super strong conformal ability of hydrogel after dehydration to produce a hollow pyramid microstructure, thereby improving the sensitivity of the sensor and ensuring stable mechanical properties; the gradient pyramid microstructure is utilized to improve the linearity of the sensor.

[0020] (2) The flexible sensor and preparation method of the gradient hollow pyramid microstructure with tangential anisotropy described in the present invention are as follows: on the basis of the pyramid microstructure, the interior is set as a hollow structure, and a plurality of through holes are set on two surfaces of the pyramid microstructure opposite to each other in the same direction to form a hollow pyramid microstructure, thereby effectively improving the sensitivity of the sensor; while further reducing the mechanical modulus and improving the sensitivity, it also makes the deformation ability in the X-axis and Y-axis directions different. By utilizing the anisotropy of the structure, the normal force and the tangential force of the X-axis and Y-axis can be measured.

[0021] (3) The flexible sensor and preparation method of the present invention having a gradient hollow pyramid microstructure with tangential anisotropy, which reduces the initial capacitance of the sensor by arranging a flexible gasket between the dielectric layer and the lower copper foil electrode, effectively improves the sensitivity of the sensor.

[0022] (4) The flexible sensor with a gradient hollow pyramid microstructure and its preparation method described in the present invention has an ultra-large range of 0 to 1000 kPa and a high sensitivity. The sensitivity of 0 to 6 kPa is S1 = 916.333 kPa -1 ; 6~25kPa sensitivity is S2=289.053kPa -1 ;25~1000kPa sensitivity is S3=60.057kPa -1 , dynamic response time is short, about 50ms; minimum resolution does not exceed 0.0005N, area is about 8×8mm 2 (pressure is approximately 0.78125 Pa), and the sensor has good repeatability and linearity. The sensor can be used to monitor physiological signals such as breathing and swallowing. The sensor has the advantages of simple structure and preparation process, and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0024] In the attached figure:

[0025] Figure 1 This is a structural schematic diagram of a flexible sensor with a gradient hollow pyramid microstructure according to the present invention;

[0026] Figure 2 This is a cross-sectional structural diagram of a flexible sensor with a gradient hollow pyramid microstructure according to the present invention;

[0027] Figure 3 Schematic diagram of the structure of the dielectric layer of a flexible sensor with a gradient hollow pyramid microstructure according to the present invention;

[0028] Figure 4 1 is a top view of a dielectric layer of a flexible sensor having a gradient hollow pyramid microstructure according to the present invention;

[0029] Figure 5 This is a cross-sectional structural diagram of a dielectric layer of a flexible sensor having a gradient hollow pyramid microstructure according to the present invention;

[0030] Figure 6 This is a process flow chart of a method for preparing a flexible sensor with a gradient hollow pyramid microstructure according to the present invention;

[0031] Figure 7 This is a schematic diagram of the initial mold structure of a method for preparing a flexible sensor with a gradient hollow pyramid microstructure according to the present invention;

[0032] Figure 8 This is a structural schematic diagram of a PDMS mold for a method of preparing a flexible sensor with a gradient hollow pyramid microstructure according to the present invention;

[0033] Figure 9 This is a structural schematic diagram of inserting a fine needle into a PDMS mold in a method for preparing a flexible sensor with a gradient hollow pyramid microstructure according to the present invention;

[0034] Among them: 1-upper insulating flexible substrate, 2-upper copper foil electrode, 3-dielectric layer, 3-1-small pyramid, 3-2-large pyramid, 3-3-small pyramid hollow structure, 3-4-large pyramid hollow structure, 3-5-through hole, 4-flexible gasket, 5-lower copper foil electrode, 6-lower insulating flexible substrate, 7-fine needle. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0036] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0038] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0039] Specific implementation method 1: See Figures 1-9 This embodiment is described in detail. A flexible sensor with a gradient hollow pyramid microstructure described in this embodiment specifically includes an upper insulating flexible substrate 1, an upper copper foil electrode 2, a dielectric layer 3, a flexible gasket 4, a lower copper foil electrode 5, and a lower insulating flexible substrate 6. The upper insulating flexible substrate 1, the upper copper foil electrode 2, the dielectric layer 3, the flexible gasket 4, the lower copper foil electrode 5, and the lower insulating flexible substrate 6 are connected in sequence. A plurality of pyramid structures are provided on the dielectric layer 3, the tops of the pyramid structures being connected to the upper copper foil electrode 2. The pyramid structures are hollow structures. The plurality of pyramid structures are provided with a plurality of through holes 3-5 on two opposing surfaces in the same direction, and the number of through holes 3-5 increases from the top to the bottom of the pyramid structure.

[0040] like Figure 3-Figure 4As shown, the pyramid structure includes a small pyramid 3-1 and a large pyramid 3-2, and the small pyramid 3-1 and the large pyramid 3-2 are alternately arranged; Figure 5 As shown, the hollow structure within the small pyramid 3-1 and the through-holes 3-5 on its surface form the small pyramid hollow structure 3-3, while the hollow structure within the large pyramid 3-2 and the through-holes 3-5 on its surface form the large pyramid hollow structure 3-4. The dielectric layer 3 comprises two pyramid structures, one large and one small. When the sensor is subjected to compression, the large pyramid 3-2 begins to deform first. As the large pyramid 3-2 continues to compress, the sensor's sensitivity decreases. When the small pyramid 3-1 is compressed, it contacts the sensor's upper copper foil electrode 2, increasing the contact area and improving sensitivity and linearity. The through-holes 3-5 in the thin wall of the hollow pyramid further reduce the mechanical modulus and improve sensitivity. In this embodiment, the through-holes 3-5 are distributed only in the X-axis direction and not in the Y-axis direction, resulting in different deformation capacities in the X and Y-axis directions. Leveraging the anisotropy of this structure, it is possible to measure tangential forces along both the X and Y axes.

[0041] The flexible gasket 4 is annular and is arranged at the edge of the lower copper foil electrode 5. Initially, the dielectric layer 3 and the lower copper foil electrode 5 are separated by the flexible gasket 4, which reduces the initial capacitance of the sensor and improves the sensitivity of the sensor.

[0042] like Figure 6 As shown, a method for preparing the above-mentioned flexible sensor with a gradient hollow pyramid microstructure includes the following steps:

[0043] Step 1: Preparation of an insulating flexible substrate: The upper insulating flexible substrate 1 is made of single-sided PET tape with a thickness of 115 μm, and the side with glue is adhered to the copper electrode; the lower insulating flexible substrate 6 is made of double-sided PET tape with a thickness of 160 μm, and one side of the double-sided PET tape is adhered to the copper electrode, and the other side is used for installation and adhered to the surface of the application scene; Use scissors to cut the upper insulating flexible substrate 1 and the lower insulating flexible substrate 6 into 10 mm × 10 mm squares;

[0044] Step 2: Electrode layer preparation: The upper copper foil electrode 2 and the lower copper foil electrode 5 are made of copper foil tape. The copper foil tape is 100 μm thick and is cut into 10 mm × 10 mm squares using scissors to prepare the upper copper foil electrode 2 and the lower copper foil electrode 5.

[0045] Step 3: Preparation of dielectric layer: Use 2μm precision light-curing 3D printing equipment to print the initial mold of the sensor dielectric layer microstructure, such as Figure 7As shown; prepare the PDMS mixture and pour it for curing. Mix the PDMS, curing agent and silicone oil in a beaker in a mass ratio of 20:1:2, and use a glass rod to stir in a fixed direction for 3 minutes until fine and uniform bubbles appear to fully mix the components; put the stirred mixed viscous liquid into a vacuum drying oven at room temperature to evacuate and remove bubbles (negative pressure: -0.8Bar, time 30 minutes). After there are no obvious bubbles in the viscous liquid, pour the PDMS mixture onto the initial mold, put it into a vacuum drying oven at room temperature to evacuate and remove bubbles (negative pressure: -0.8Bar, time 10 minutes), ensure that there are no bubbles in the PDMS mixture on the template, put it into a vacuum drying oven, and cure it at 80℃ for 2 hours; after the PDMS is cured, demold and remove the PDMS with gradient pyramid microstructure, use the demolded PDMS as a molding mold, and insert a fine needle 7 into the large and small pyramid structures of the molding mold, as shown Figure 8-Figure 9 shown.

[0046] Prepare a polyvinyl alcohol (PVA) mixture: Polyvinyl Pure 1799, deionized water, and phosphoric acid solution in a ratio of 6g:60ml:5ml. First, use a graduated cylinder to measure 60ml of deionized water and transfer it to a beaker. Then weigh 6g of Polyvinyl Pure 1799. Place the beaker containing deionized water on a magnetic stirrer at 500rpm. Slowly add 6g of Polyvinyl Pure 1799 to the deionized water in small portions. After complete addition, stir at room temperature for 20 minutes. Seal the beaker with plastic wrap and place it on a heated stirrer. Gradually heat to 95°C and stir at 500rpm for 1-2 hours until the solution becomes transparent. Remove the beaker and place it on a magnetic stirrer, continuing stirring until the solution cools to room temperature. Use a pipette to draw 5ml of phosphoric acid solution into the beaker and continue stirring for 5 minutes to mix the solution thoroughly. This results in a PVA mixture.

[0047] Pour the PVA mixture into the PDMS mold. Use a syringe to draw up the PVA mixture and use a 0.4mm needle to pour it into the PDMS mold. This operation can effectively reduce the generation of bubbles compared to direct pouring. Place the template horizontally and dehydrate it at a constant temperature of 25°C for 7 hours. Insert a fine needle 7 and dehydrate for another 5 hours. Remove the fine needle 7 and use tweezers to peel the dielectric layer 3 from the PDMS mold to obtain a dielectric layer 3 with a gradient hollow pyramid microstructure. Use scissors to trim the four sides of the dielectric layer 3 neatly. The reason for not pouring the PVA mixture directly into the 3D-printed mold is that after dehydration, the PVA mixture has a strong adhesion to the initial 3D-printed mold, making it impossible to demold. Using a PDMS mold takes advantage of the hydrophobicity of PDMS, making it easier to demold the PVA hydrogel.

[0048] Step 4, sensor packaging: The structure of the sensor from top to bottom is: upper insulating flexible substrate 1, upper copper foil electrode 2, dielectric layer 3 with gradient hollow pyramid microstructure, flexible gasket 4, lower copper foil electrode 5 and lower insulating flexible substrate 6. The upper insulating flexible substrate 1 is a single-sided PET tape, and the upper copper foil electrode 2 is a copper foil tape. The glued side of the single-sided PET tape is pasted together with the glued side of the copper foil tape; the lower insulating flexible substrate 6 is a double-sided PET tape, and the lower copper foil electrode 5 is a copper foil tape. One of the glued sides of the double-sided PET tape is pasted together with the glued side of the copper foil tape; use a spray pen to spray a layer of PDMS mixture on the non-glue side of the copper foil tape used for the upper copper foil electrode 2. The thickness of the PDMS mixture is 100μm; place an 8×8mm PET baffle in the center of the lower copper foil electrode 5, and spray at the edge of the lower copper foil electrode 5. Apply a layer of PDMS mixture with a thickness of 100μm. After spraying, remove the PET baffle to obtain a thin ring-shaped PDMS layer with a width of 1mm covering the edge of the copper foil; attach the flexible gasket 4 to the edge of the lower copper foil electrode 5; spray a layer of PDMS mixture on the upper surface of the flexible gasket 4; attach the upper copper foil electrode 2 to the pyramid top of the dielectric layer 3, and attach the lower surface of the dielectric layer 3 to the flexible gasket 4. Curing at 45°C for 2 hours, after waiting for the sprayed thin PDMS mixture layer to cure, the dielectric layer 3 and the upper and lower copper foil electrodes can be fixed, completing the bonding and fixation between the sensor layers.

[0049] To summarize the above implementation cases, the flexible sensor with a gradient hollow pyramid microstructure and the preparation method thereof described in the present invention utilize the super-strong conformal ability of the hydrogel after dehydration to produce a hollow pyramid microstructure, thereby ensuring stable mechanical properties and improving the sensitivity of the sensor; the gradient pyramid microstructure is utilized to improve the linearity of the sensor.

[0050] The flexible sensor having a gradient hollow pyramid microstructure and the preparation method thereof disclosed in the present invention are characterized by forming a hollow structure inside the pyramid microstructure and providing a plurality of through holes 3-5 on two surfaces of the pyramid microstructure facing each other in the same direction, thereby effectively improving the sensitivity of the sensor. Furthermore, while further reducing the mechanical modulus and improving the sensitivity, the sensor also produces differences in deformation capabilities in the X-axis and Y-axis directions. Utilizing the anisotropy of the structure, the sensor can measure tangential forces along the X-axis and Y-axis.

[0051] The flexible sensor with a gradient hollow pyramid microstructure and its preparation method described in the present invention reduce the initial capacitance of the sensor by arranging a flexible gasket 4 between the dielectric layer 3 and the lower copper foil electrode 5, thereby effectively improving the sensitivity of the sensor.

[0052] The flexible sensor with a gradient hollow pyramid microstructure and its preparation method described in the present invention has an ultra-large range of 0 to 1000 kPa and a high sensitivity. The sensitivity of 0 to 6 kPa is S1 = 916.333 kPa. -1 ; 6~25kPa sensitivity is S2=289.053kPa -1 ;25~1000kPa sensitivity is S3=60.057kPa -1 , dynamic response time is short, about 50ms; minimum resolution does not exceed 0.0005N, area is about 8×8mm 2 (pressure is approximately 0.78125 Pa), and the sensor has good repeatability and linearity. The sensor can be used to monitor physiological signals such as breathing and swallowing. The sensor has the advantages of simple structure and preparation process, and low cost.

[0053] The specific embodiments described above further illustrate the objectives, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is merely a specific embodiment of the present invention and is not intended to limit the invention. Reasonable combinations of the features described in the above embodiments are also possible. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A flexible sensor with a gradient hollow pyramid microstructure, characterized by: The invention comprises an upper insulating flexible substrate (1), an upper copper foil electrode (2), a dielectric layer (3), a flexible gasket (4), a lower copper foil electrode (5) and a lower insulating flexible substrate (6), wherein the upper insulating flexible substrate (1), the upper copper foil electrode (2), the dielectric layer (3), the flexible gasket (4), the lower copper foil electrode (5) and the lower insulating flexible substrate (6) are connected in sequence; a plurality of pyramid structures are provided on the dielectric layer (3), and the tops of the pyramid structures are connected to the upper copper foil electrode (2); and the pyramid structures are hollow structures.

2. The flexible sensor having a gradient hollow pyramid microstructure according to claim 1, characterized in that: A plurality of through holes (3-5) are provided on two opposite surfaces of the pyramid structure.

3. The flexible sensor having a gradient hollow pyramid microstructure according to claim 2, characterized in that: The through holes (3-5) on the surface of the pyramid structure increase in number from top to bottom.

4. The flexible sensor having a gradient hollow pyramid microstructure according to claim 1, 2 or 3, characterized in that: The pyramid structure comprises a small pyramid (3-1) and a large pyramid (3-2), and the small pyramid (3-1) and the large pyramid (3-2) are arranged alternately.

5. The flexible sensor having a gradient hollow pyramid microstructure according to claim 4, characterized in that: The flexible gasket (4) is annular and is arranged at the edge of the lower copper foil electrode (5).

6. A method for preparing the flexible sensor having a gradient hollow pyramid microstructure according to claim 5, characterized in that: The following steps are involved: Step 1, preparation of an insulating flexible substrate: using a single-sided PET tape for the upper insulating flexible substrate (1), with the side with glue attached to the copper electrode; using a double-sided PET tape for the lower insulating flexible substrate (6), with one side of the double-sided PET tape attached to the copper electrode and the other side used for installation; cutting the upper insulating flexible substrate (1) and the lower insulating flexible substrate (6); Step 2: Preparation of electrode layer: The upper copper foil electrode (2) and the lower copper foil electrode (5) are made using copper foil tape, and the copper foil tape is cut into squares; Step 3: Preparation of dielectric layer: using a 3D printing device to print an initial mold, preparing a PDMS mixed liquid and pouring it into the initial mold to solidify to obtain a molding mold; preparing a PVA mixed liquid and pouring it into the PDMS mold, dehydrating it to a semi-solidified state, inserting a fine needle (7), and then dehydrating it to obtain a dielectric layer (3); Step 4, sensor packaging: the glued side of the upper insulating flexible substrate (1) is glued to the glued side of the upper copper foil electrode (2); the glued side of the lower insulating flexible substrate (6) is glued to the glued side of the lower copper foil electrode (5); a layer of PDMS mixed liquid is sprayed on the edge of the side without glue of the upper copper foil electrode (2), and a layer of PDMS mixed liquid is sprayed on the edge of the lower copper foil electrode (5); the flexible gasket (4) is attached to the edge of the lower copper foil electrode (5); a layer of PDMS mixed liquid is sprayed on the upper surface of the flexible gasket (4); the upper copper foil electrode (2) is attached to the top of the pyramid of the dielectric layer (3), and the lower surface of the dielectric layer (3) is attached to the flexible gasket (4), and the preparation is completed after curing.

7. The method for preparing a flexible sensor having a gradient hollow pyramid microstructure according to claim 6, characterized in that: The components of the PDMS mixed solution in step 3 are PDMS, curing agent and silicone oil, with a mass ratio of 20:1:

2.

8. The method for preparing a flexible sensor having a gradient hollow pyramid microstructure according to claim 6, wherein: The components of the PVA mixed solution in step 3 are polyvinyl alcohol 1799, deionized water and phosphoric acid solution, with a ratio of 6g:60ml:5ml.

9. The method for preparing a flexible sensor having a gradient hollow pyramid microstructure according to claim 6, wherein: The thickness of the PDMS mixed solution coating in step 4 is 100 μm.

10. The method for preparing a flexible sensor having a gradient hollow pyramid microstructure according to claim 6, wherein: The copper foil tape used for the upper copper foil electrode (2) and the lower copper foil electrode (5) in step 2 has a thickness of 100 μm.

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