A flexible tactile sensor and its preparation method and application

Abstract

The present invention provides a flexible tactile sensor, its preparation method, and application. The flexible tactile sensor comprises an interconnected tactile sensing layer and flexible electrodes. The tactile sensing layer has a gradient microsphere structure composed of conductive polymer microspheres arranged in a gradient from small to large sizes. The flexible tactile sensor exhibits high linearity, high sensitivity, a wide measurement range, and a gradient structure, making it particularly suitable for the preparation of electronic skin materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensors and relates to a flexible tactile sensor and a preparation method and application thereof. Background Art

[0002] With the development of society, flexible wearable devices have been integrated into all aspects of human life. Among them, flexible tactile sensors have important applications in industrial robots, deep-sea exploration robots, service robots, space robots, telemedicine, and micro-actuated robots for precision operations in hazardous environments. They play a particularly positive role in measuring contact position when grasping objects, measuring grasping force, and detecting slippage during grasping. In addition, tactile perception is also playing an increasingly important role in the biomedical field, especially in applications such as minimally invasive surgery and tumor detection. Surgical robots can already perform surgical operations on vital organs such as the human brain and heart. However, in addition to requiring micro-magnification and visual monitoring functions, surgical robot systems also have an increasing demand for detecting and sensing contact force information during surgery.

[0003] Among the many applications of flexible electronic sensing, the most widely studied is flexible tactile sensors, especially in the field of collaborative robots. Tactile sensors can detect the tactile force generated during the movement of the robot and feed it back to the motion execution system, thereby adjusting the force and speed of the robot's movement. This can enhance the robot's ability to complete fine and complex tasks in complex environments, thereby improving the robot's operation level and intelligence level.

[0004] CN114720026A discloses a force tactile sensor with a wide linear response range based on a gradient composite integrated structure. The sensor is constructed by laminating two flexible substrates / electrodes onto the upper and lower surfaces of a gradient composite integrated structure composite conductive film. The sensing material, the gradient pore / pyramid integrated structure composite conductive film, is a composite film made by dispersing carbon nanotubes, a conductive material, within a gradient pore / pyramid integrated structure polydimethylsiloxane film via a swelling filling method. However, this swelling filling method makes it difficult to fully disperse the conductive material, and the bonding between the conductive material and the gradient pore / pyramid integrated structure composite film is weak, leaving room for improvement in device sensitivity.

[0005] CN108318161A discloses a wearable pressure sensor and its manufacturing method. The structure uses a flexible PDMS film as a base, PDMS microspheres coated on the PDMS film, and then a carbon nanotube aqueous solution is applied to the surface. After drying, a conductive layer is formed. The two conductive films are stacked relative to each other to prepare a pressure sensor. However, the conductive layer formed by coating the carbon nanotube aqueous solution on the surface of the PDMS microspheres in this tactile sensor is weak in bonding with the microspheres, and it is difficult to fully coat the PDMS microspheres.

[0006] Although the research on flexible tactile sensors has made great progress in recent years, there are still many problems such as insufficient response sensitivity of sensing materials, poor stability and anti-interference ability, and narrow sensing range, which limit their practical applications.

[0007] To solve the above problems, the key is to select active materials with excellent performance and design a reasonable device structure. By coating the flexible polymer microspheres to form a conductive layer, and especially further improving the linearity, sensitivity, wide range and other performance of the electronic skin through the gradient microsphere arrangement structure, not only the prepared flexible tactile sensor has a sensitive mechanical response, but also plays a beneficial role in mechanical properties.

[0008] Therefore, it is necessary to develop a flexible tactile sensor with high linearity, high sensitivity, wide range and gradient structure, as well as its preparation method and application. Summary of the Invention

[0009] In view of the deficiencies in the prior art, the object of the present invention is to provide a flexible tactile sensor and a preparation method and application thereof. The flexible tactile sensor of the present invention has high linearity, high sensitivity, a wide range and a gradient structure.

[0010] One of the objectives of the present invention is to provide a flexible tactile sensor. To achieve this objective, the present invention adopts the following technical solutions:

[0011] A flexible tactile sensor comprises a tactile sensing layer and a flexible electrode connected to each other. The tactile sensing layer has a gradient microsphere structure composed of conductive polymer microspheres arranged in a gradient from small to large sizes.

[0012] The present invention forms a conductive layer by coating flexible polymer microspheres, and further improves the linearity, sensitivity, wide range and other performance of the flexible tactile sensor through the gradient microsphere arrangement structure. Not only does the prepared flexible tactile sensor have a sensitive mechanical response, but it also plays a beneficial role in the mechanical properties of the flexible tactile sensor, and is particularly suitable for the preparation of electronic skin materials.

[0013] The gradient microsphere structure gradually transitions from a bottom layer of small-sized microspheres with a diameter of less than 10 microns to a top layer of large-sized microspheres with a diameter of more than 150 microns.

[0014] As a first preferred embodiment of the present invention, the conductive polymer microspheres include flexible polymer microspheres and a conductive layer, and the conductive layer is coated on the outer layer of the flexible polymer microspheres.

[0015] Preferably, the flexible polymer microspheres are one of polydimethylsiloxane microspheres, polyvinyl alcohol microspheres, and polypyrrole microspheres.

[0016] Preferably, the conductive layer comprises polymer and conductive powder.

[0017] Preferably, the mass ratio of the polymer to the conductive powder is (5-20):1, for example, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, etc., preferably (10-20):1; if the mass ratio of the polymer to the conductive powder is too small, less than 5:1, the polymer precursor cannot fully infiltrate the conductive powder, resulting in the conductive powder being unable to coat the polymer microspheres to form conductive microspheres, that is, the conductive powder cannot be effectively coated on the polymer microspheres, and an effective connection between the microspheres cannot be formed; if the mass ratio of the polymer to the conductive powder is too large, greater than 20:1, the conductive powder in the conductive layer is sparsely distributed, it is difficult to form a conductive path, and sensing is impossible.

[0018] Preferably, the polymer in the conductive layer is consistent with the polymer in the flexible polymer microspheres, and is preferably one of polydimethylsiloxane, polyvinyl alcohol, and polypyrrole.

[0019] Preferably, the conductive powder comprises any one of carbon nanotubes, graphene, graphene oxide, modified graphene oxide, silver nanowires, and MXene, or a mixture of at least two thereof.

[0020] Preferably, the thickness of the conductive layer is 20 nm-30 μm, for example, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, etc.

[0021] As a second preferred embodiment of the present invention, the conductive polymer microspheres comprise polymer microspheres having a hollow cavity and a conductive layer, wherein the conductive layer is coated on the outer layer of the polymer microspheres having a hollow cavity. This preferred embodiment differs from the first preferred embodiment in that the polymer microspheres have a hollow cavity, and the type of polymer microspheres and conductive layer can refer to the first preferred embodiment.

[0022] Preferably, the flexible electrode comprises a flexible base layer and an electrode, wherein the flexible base layer is provided on the upper and lower sides of the electrode, and a tactile sensing layer is provided between the flexible base layer and the electrode on one side.

[0023] Preferably, the flexible substrate layer is a PET film or a PDMS film.

[0024] Preferably, the electrode is a gold electrode or a silver electrode, and the electrode type may be an interdigitated electrode or other types of electrodes commonly used in the art.

[0025] The flexible tactile sensor further includes a polymer packaging material, and the tactile sensing layer and the flexible electrode are packaged together by the polymer packaging material.

[0026] The polymer packaging material includes one of PDMS, silicone rubber material or polyurethane.

[0027] A second object of the present invention is to provide a method for preparing the flexible tactile sensor described in the first object, comprising the following steps: preparing a tactile sensing layer having a gradient microsphere structure, and pressing the tactile sensing layer onto a flexible electrode to obtain the flexible tactile sensor. The method for preparing the tactile sensing layer having a gradient microsphere structure comprises the following steps:

[0028] S1, mixing a polymer and a curing agent to prepare a polymer precursor, adding an emulsifier to emulsify the mixture to prepare a polymer emulsion, and curing, centrifuging, and sieving the mixture to obtain polymer microspheres of different sizes;

[0029] S2, mixing a polymer precursor liquid prepared by mixing a polymer and a curing agent with a conductive powder, and mixing the mixture with the polymer microspheres of different sizes prepared in S1 to obtain conductive polymer microspheres of different sizes;

[0030] S3, arranging the conductive polymer microspheres of different sizes obtained in S2 in a gradient from small to large size, coating them layer by layer, and obtaining the tactile sensing layer having the gradient microsphere structure after curing.

[0031] The mass ratio of the polymer to the curing agent is (8-12):1, for example, 8:1, 9:1, 10:1, 11:1, 12:1, etc.

[0032] Preferably, in S1, the polymer is one of polydimethylsiloxane, polyvinyl alcohol, and polypyrrole, and the curing agent comprises polydimethylsiloxane with a hydrogen group and a trace amount of Pt catalyst.

[0033] Preferably, in S1, the emulsifier comprises an oil-in-water emulsifier, preferably, the emulsifier comprises any one of polysorbate, polyoxyethylene sorbitan monotalate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan dioleate, polyoxyethylene sorbitan monostearate, polyoxyethylene glycerol monolaurate, polyoxyethylene pentaerythritol monotalate, polyoxyethylene sucrose monooleate, and alkylphenol polyoxyethylene ether, or a mixture of at least two thereof.

[0034] Preferably, in S1, the mass percentage of the emulsifier to the mass percentage of the polymer is 0.5-3%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc.

[0035] Preferably, in S1, the curing temperature is 70-90°C, for example, 70°C, 75°C, 80°C, 85°C, 90°C, etc., and the curing time is 1-3h, for example, 1h, 1.5h, 2h, 2.5h, 3h, etc.

[0036] Preferably, in S1, the mesh size of the sieving is 100-1000 mesh, for example, 100 mesh, 200 mesh, 300 mesh, 400 mesh, 500 mesh, 600 mesh, 700 mesh, 800 mesh, 900 mesh, 1000 mesh, etc.

[0037] Preferably, in S2, the polymer is one of polydimethylsiloxane, polyvinyl alcohol, and polypyrrole, and the mass ratio of the polymer to the conductive powder is (5-20):1.

[0038] Preferably, in S2, the curing agent comprises polydimethylsiloxane with a hydrogen group and a trace amount of Pt catalyst, and the mass ratio of the polymer to the curing agent is (8-12):1.

[0039] Preferably, in S2, the mass ratio of the polymer to the conductive powder is (5-20):1.

[0040] As a preferred embodiment of the present invention, a flexible tactile sensor comprises a flexible base layer, a tactile sensing layer, an electrode, and a flexible base layer, connected sequentially from top to bottom. During fabrication, the tactile sensing layer is laminated onto the electrode with the flexible base layer, and the tactile sensing layer is then covered with a flexible base layer, which is then encapsulated with a polymer encapsulation material. The layers can also be connected by applying glue.

[0041] A third object of the present invention is to provide an application of the flexible tactile sensor described in the first object, wherein the flexible tactile sensor is used in the preparation of electronic skin materials.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The flexible tactile sensor of the present invention has high linearity, high sensitivity, wide range and gradient structure, which not only makes the prepared flexible tactile sensor have sensitive mechanical response, but also plays a beneficial role in the mechanical properties of the flexible tactile sensor, and is particularly suitable for the preparation of electronic skin materials. Specifically, the sensitivity is 1.45-2.75kPa -1 , the maximum response tensile force is 320-500kPa, the elongation at break is 60-106%, and the tensile strength is 3.7-6.2MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Schematic diagram of the preparation method of the tactile sensing layer having a gradient microsphere structure of the present invention;

[0045] Figure 2 Schematic diagram of the structure of the tactile sensing layer with a gradient microsphere structure;

[0046] Figure 3 Schematic diagram of the structure of the flexible tactile sensor of the present invention;

[0047] Figure 4 This is the relationship between different PDMS to carbon nanotube mass ratios and the elongation at break of the tactile sensing layer;

[0048] Figure 5 The pressure-resistance curves of Example 3 and Comparative Example 1 of the present invention are shown;

[0049] The reference numerals are as follows:

[0050] 1-Flexible base layer; 2-Tactile sensing layer; 3-Electrode. DETAILED DESCRIPTION

[0051] The following is combined with Figure 1-5 , and further illustrate the technical solution of the present invention through specific implementation methods.

[0052] Unless otherwise specified, various raw materials of the present invention can be purchased commercially or prepared according to conventional methods in the art.

[0053] Example 1

[0054] The flexible tactile sensor of this embodiment is prepared by the following method:

[0055] PDMS and a curing agent are mixed in a ratio of 10:1 to form a PDMS precursor solution. The curing agent is polydimethylsiloxane with a hydrogen group and a trace amount of Pt catalyst. 2.5 wt.% polysorbate is added to deionized water. 20 wt.% of the PDMS precursor solution is added under mechanical stirring and emulsified to form an emulsion.

[0056] The mixture was cured at 80°C for 2 h, then rinsed with deionized water and centrifuged ten times. During the centrifugation, the mixture was filtered through sieves of different mesh sizes (100, 150, 170, 180, 240, 300, 400, 500, 600, 800, and 1000 mesh) to obtain PDMS flexible polymer microspheres of different size ranges.

[0057] PDMS and a curing agent were then mixed at a ratio of 10:1, followed by carbon nanotube conductive powder. The mass ratio of PDMS to carbon nanotube conductive powder was 20:1. The curing agent was polydimethylsiloxane with a hydrogen group and a trace amount of Pt catalyst. The mixture was then centrifuged and stirred with the cured flexible polymer microspheres at a mass ratio of 1:4 to form PDMS flexible conductive microspheres of different sizes.

[0058] According to the average diameter of PDMS flexible conductive microspheres of different sizes, the diameters of the microspheres gradually increase from <10 μm to >150 μm (5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 35 μm, 40 μm, 50 μm, 75 μm, 90 μm, 145 μm, and 165 μm) from the bottom layer to the top layer, and are coated layer by layer in a gradient arrangement, such as Figure 2 As shown, the tactile sensing layer is placed in an oven for curing to prepare a tactile sensing layer having a gradient microsphere structure, as shown in FIG. Figure 1 As shown;

[0059] The tactile sensing layer is laminated onto the flexible interdigital electrode, and PET films are placed on both sides. Finally, the sensor is encapsulated with PDMS to obtain a flexible tactile sensor. The structural diagram is shown in the figure. Figure 3 shown.

[0060] Example 2

[0061] The flexible tactile sensor of this embodiment is prepared by the following method:

[0062] PDMS and curing agent are mixed in a ratio of 10:1 to form a PDMS precursor solution. The curing agent is polydimethylsiloxane with a hydrogen group and a trace amount of Pt catalyst. 2.5wt.% polysorbate is added to deionized water, and 20wt.% PDMS precursor solution is added under mechanical stirring and emulsified to form an emulsion.

[0063] The mixture was cured at 80°C for 2 h, then rinsed with deionized water and centrifuged ten times. During the centrifugation, the mixture was filtered through sieves of different mesh sizes (100, 150, 170, 180, 240, 300, 400, 500, 600, 800, and 1000 mesh) to obtain PDMS flexible polymer microspheres of different size ranges.

[0064] PDMS and a curing agent were then mixed in a ratio of 10:1 and then mixed with carbon nanotube conductive powder, where the mass ratio of PDMS to carbon nanotube conductive powder was 15:1. The curing agent was polydimethylsiloxane with a hydrogen group and a trace amount of Pt catalyst. The mixture was then centrifuged and stirred with the cured flexible polymer microspheres in a mass ratio of 1:4 to form PDMS flexible conductive microspheres of different sizes.

[0065] PDMS flexible conductive microspheres of different sizes are arranged in a gradient pattern, with diameters gradually increasing from <10 microns to >150 microns. These microspheres are then coated layer by layer and placed in an oven for curing to prepare a tactile sensing layer with a gradient microsphere structure.

[0066] The tactile sensing layer is laminated onto the flexible interdigital electrode, and finally the sensor is encapsulated with a polymer material to obtain a flexible tactile sensor.

[0067] Example 3

[0068] The difference between this embodiment and embodiment 1 is that the mass ratio of PDMS to carbon nanotube conductive powder is 10:1, and the other components are the same as those in embodiment 1.

[0069] Example 4

[0070] The difference between this embodiment and embodiment 1 is that the mass ratio of PDMS to carbon nanotube conductive powder is 5:1, and the other components are the same as those in embodiment 1.

[0071] Comparative Example 1

[0072] The flexible tactile sensor of this comparative example was prepared by the following method:

[0073] PDMS and a curing agent (polydimethylsiloxane with hydrogen groups and a trace amount of Pt catalyst) were mixed in a 10:1 ratio to form a PDMS precursor. 2.5 wt.% polysorbate was added to deionized water, and 20 wt.% of the PDMS precursor was added under mechanical stirring to form an emulsion. The mixture was cured at 80°C for 2 hours, then rinsed with deionized water and centrifuged ten times to obtain PDMS flexible polymer microspheres of mixed sizes.

[0074] PDMS and a curing agent are then mixed in a 10:1 ratio and then mixed with carbon nanotube conductive powder. The mass ratio of PDMS to carbon nanotube conductive powder is 10:1. The curing agent is polydimethylsiloxane with a hydrogen group and a trace amount of Pt catalyst. The mixture is then centrifuged and stirred with the cured flexible polymer microspheres in a 1:4 mass ratio to prepare a mixed-size PDMS flexible conductive microsphere ink.

[0075] The mixed structure tactile sensing layer is then coated and cured in an oven. The tactile sensing layer is pressed onto the flexible interdigital electrodes and finally encapsulated with PDMS to obtain a flexible tactile sensor.

[0076] The tactile sensor sensing layers prepared in Examples 1-4 and Comparative Example 1 were subjected to a tensile test at room temperature. The test standard was based on ISO 1798, Tensile test for flexible porous polymers. The elongation at break of the sensing layers with different PDMS to carbon nanotube mass ratios was as follows: Figure 4 shown.

[0077] Depend on Figure 4 As can be seen, because the conductive layer is composed of PDMS and carbon materials, it firmly bonds with the PDMS microspheres, and the resulting tactile sensor sensing layer has good stretchability. However, as the carbon nanotube content increases, when the mass ratio of PDMS to carbon nanotubes in the conductive layer exceeds 10:1, the elongation at break decreases significantly. This is because as the carbon nanotube content increases, the excessive carbon nanotubes tend to agglomerate inside, which in turn reduces the bonding strength between the microspheres.

[0078] The flexible tactile sensors prepared in Example 3 and Comparative Example 1 were used for electronic skin and placed on a multi-axis force / torque sensor test system platform. The mechanical response of the tactile sensors was tested using a multi-axis force / torque sensor. The pressure-resistance curve is shown in FIG. Figure 5 As shown, the test conditions are: pressure speed: 0.01N / s, temperature: 25℃.

[0079] from Figure 5 It can be seen from the medium pressure-resistance curve that due to the use of the coating process, the surface carbon nanotube coating of the PDMS microspheres is achieved, so that a conductive layer is formed on the surface of the PDMS microspheres. Under the action of pressure, the microspheres squeeze each other, resulting in an increase in the conductive path, a decrease in the system resistance, and a response to pressure. However, since Example 3 further adopts a gradient microsphere arrangement structure, the linearity and sensitivity of the flexible tactile sensor are further improved. Under low pressure, the sensitivity is further improved compared to the hybrid structure of Comparative Example 1, reaching 2.75kPa. -1 , which further illustrates that the gradient microsphere arrangement structure can effectively improve sensitivity and respond accurately and sensitively to mechanical forces.

[0080] The performance indicators of the flexible tactile sensors prepared in Example 3 and Comparative Example 1 are shown in Table 1.

[0081] Table 1

[0082]

[0083] It can be seen from the data in Table 1 that, compared with the hybrid structure without gradient arrangement, the flexible tactile sensor of the present invention has a gradient microsphere structure in the tactile sensing layer, which can effectively improve the sensitivity and maximum response pressure of the material, while the material has good mechanical properties.

[0084] The flexible tactile sensor of the present invention has high linearity, high sensitivity, wide range and gradient structure, which not only makes the prepared flexible tactile sensor have sensitive mechanical response, but also plays a beneficial role in the mechanical properties of the flexible tactile sensor, and is particularly suitable for the preparation of electronic skin materials. Specifically, the sensitivity is 1.45-2.75kPa -1 , the maximum response tensile force is 320-500kPa, the elongation at break is 60-106%, and the tensile strength is 3.7-6.2MPa.

[0085] While the present invention uses the above-described embodiments to illustrate the detailed process equipment and process flow of the present invention, the present invention is not limited to the above-described detailed process equipment and process flow, and does not necessarily rely on the above-described detailed process equipment and process flow for implementation. Those skilled in the art will appreciate that any improvements to the present invention, equivalent replacements for raw materials in the products of the present invention, additions of auxiliary ingredients, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

[0086] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0087] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0088] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A flexible tactile sensor, characterized in that: The invention comprises a tactile sensing layer and a flexible electrode connected to each other, wherein the tactile sensing layer has a gradient microsphere structure, and the gradient microsphere structure is composed of conductive polymer microspheres arranged in a gradient from small size to large size; The conductive polymer microspheres include flexible polymer microspheres and a conductive layer, and the conductive layer is coated on the outer layer of the flexible polymer microspheres.

2. The flexible tactile sensor according to claim 1, characterized in that: The gradient microsphere structure gradually transitions from a bottom layer of small-sized microspheres with a diameter of less than 10 microns to a top layer of large-sized microspheres with a diameter of more than 150 microns.

3. The flexible tactile sensor according to claim 1, wherein: The flexible polymer microspheres are one of polydimethylsiloxane microspheres, polyvinyl alcohol microspheres and polypyrrole microspheres.

4. The flexible tactile sensor according to claim 1, wherein: The conductive layer comprises polymer and conductive powder.

5. The flexible tactile sensor according to claim 4, characterized in that: The mass ratio of the polymer to the conductive powder is (5-20):

1.

6. The flexible tactile sensor according to claim 5, characterized in that: The mass ratio of the polymer to the conductive powder is (10-20).

7. The flexible tactile sensor according to claim 4, characterized in that: The polymer in the conductive layer is consistent with the polymer in the flexible polymer microspheres.

8. The flexible tactile sensor according to claim 7, characterized in that: The polymer in the conductive layer is one of polydimethylsiloxane, polyvinyl alcohol and polypyrrole.

9. The flexible tactile sensor according to claim 4, characterized in that: The conductive powder comprises any one of carbon nanotubes, graphene, graphene oxide, modified graphene oxide, silver nanowires, and MXene, or a mixture of at least two thereof.

10. The flexible tactile sensor according to claim 1, characterized in that: The thickness of the conductive layer is 20 nanometers to 30 micrometers.

11. The flexible tactile sensor according to claim 1, characterized in that: The conductive polymer microspheres include polymer microspheres with a hollow cavity and a conductive layer, wherein the conductive layer is coated on the outer layer of the polymer microspheres with a hollow cavity.

12. The flexible tactile sensor according to claim 1, wherein: The flexible electrode comprises a flexible base layer and an electrode. The flexible base layer is arranged on the upper and lower sides of the electrode, and a tactile sensing layer is arranged between the flexible base layer and the electrode on one side.

13. The flexible tactile sensor according to claim 12, characterized in that: The flexible substrate layer is a PET film or a PDMS film.

14. The flexible tactile sensor according to claim 12, characterized in that: The electrodes are gold electrodes or silver electrodes.

15. The flexible tactile sensor according to claim 1, characterized in that: The flexible tactile sensor further includes a polymer packaging material.

16. The flexible tactile sensor according to claim 15, characterized in that: The polymer packaging material includes one of PDMS, silicone rubber material or polyurethane.

17. A method for preparing the flexible tactile sensor according to any one of claims 1 to 16, characterized in that: The method comprises the following steps: preparing a tactile sensing layer with a gradient microsphere structure, and pressing the tactile sensing layer onto a flexible electrode to obtain the flexible tactile sensor.

18. The preparation method according to claim 17, characterized in that: The method for preparing the tactile sensing layer having a gradient microsphere structure comprises the following steps: S1, mixing a polymer and a curing agent to prepare a polymer precursor, adding an emulsifier to emulsify the mixture to prepare a polymer emulsion, and curing, centrifuging, and sieving the mixture to obtain polymer microspheres of different sizes; S2, mixing a polymer precursor liquid prepared by mixing a polymer and a curing agent with a conductive powder, and mixing the mixture with the polymer microspheres of different sizes prepared in S1 to obtain conductive polymer microspheres of different sizes; S3, arranging the conductive polymer microspheres of different sizes obtained in S2 in a gradient from small to large size, coating them layer by layer, and obtaining the tactile sensing layer having the gradient microsphere structure after curing.

19. The preparation method according to claim 18, characterized in that In S1, the mass ratio of the polymer to the curing agent is (8-12):

1.

20. The preparation method according to claim 18, characterized in that In S1, the polymer is one of polydimethylsiloxane, polyvinyl alcohol, and polypyrrole, and the curing agent contains polydimethylsiloxane with a hydrogen group and a trace amount of Pt catalyst.

21. The preparation method according to claim 18, characterized in that In the invention, the emulsifier comprises an oil-in-water emulsifier.

22. The preparation method according to claim 21, characterized in that The emulsifier comprises any one of polysorbate, polyoxyethylene sorbitan monotalate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan dioleate, polyoxyethylene sorbitan monostearate, polyoxyethylene glycerol monolaurate, polyoxyethylene pentaerythritol monotalate, polyoxyethylene sucrose monooleate, and alkylphenol polyoxyethylene ether, or a mixture of at least two of the following.

23. The preparation method according to claim 18, characterized in that In S1, the mass percentage of the emulsifier to the mass percentage of the polymer is 0.5-3%.

24. The preparation method according to claim 18, characterized in that In S1, the curing temperature is 70-90° C., and the curing time is 1-3 hours.

25. The preparation method according to claim 18, characterized in that In S1, the mesh size of the sieving is 100-1000 mesh.

26. The preparation method according to claim 18, characterized in that In S2, the polymer is one of polydimethylsiloxane, polyvinyl alcohol, and polypyrrole, and the mass ratio of the polymer to the conductive powder is (5-20):

1.

27. The preparation method according to claim 18, characterized in that In S2, the curing agent comprises polydimethylsiloxane with a hydrogen group and a trace amount of Pt catalyst, and the mass ratio of the polymer to the curing agent is (8-12):

1.

28. The preparation method according to claim 18, characterized in that In S2, the mass ratio of the polymer to the conductive powder is (5-20):

1.

29. An application of the flexible tactile sensor according to any one of claims 1 to 16, characterized in that: The flexible tactile sensor is used to prepare electronic skin materials.

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