Piezoelectric three-dimensional force tactile sensor based on array type PVDF

Abstract

The invention discloses a piezoelectric three-dimensional force tactile sensor based on array type PVDF. A substrate layer is fixedly connected with a lower metal electrode; the four piezoelectric layers arranged in an array are fixedly connected with the lower metal electrode, each piezoelectric layer is fixedly connected with one upper metal electrode, each upper metal electrode is fixedly connected with the dome sensing layer, one side, not fixedly connected with the upper metal electrode, of the dome sensing layer is provided with a spherical bulge, each upper metal electrode is symmetrical about the most salient point of the spherical bulge, and the lower metal electrode is fixedly connected with the dome sensing layer. And the projection of each upper metal electrode on the substrate layer is intersected with the projection of the spherical bulge on the substrate layer. The dome-type three-dimensional flexible sensing structure is adopted, the high symmetry of the structure enables the output response of the piezoelectric sensing unit to be more sensitive, and the magnitude and direction of force are accurately obtained; the three-dimensional network structure of the piezoelectric layer, introduction of pores and simulation of better porosity enable the modulus of the material to be reduced, the composite stacking structure with higher potential output and the FDM preparation process to obtain higher beta phase content, and the piezoelectric property of the sensor is improved.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, in particular to a piezoelectric three-dimensional force tactile sensor based on an array type polyvinylidene fluoride (PVDF) material. Background Art

[0002] In recent years, technologies such as intelligent robots have developed rapidly, and tactile sensors, as key technologies, have attracted much attention. According to different sensing mechanisms, tactile sensors mainly include piezoresistive, piezoelectric, capacitive and optical types. Relatively speaking, piezoelectric tactile sensors have the advantages of high sensitivity, fast dynamic response, low energy consumption and even self-power supply. They have extremely broad application prospects in the fields of dynamic force information detection and imitating human skin tactile perception. In many application scenarios, tactile (or pressure) sensors need to accurately obtain force magnitude and direction information at the same time. Most existing force sensors can only provide force magnitude information, but cannot provide force direction information. Therefore, high-sensitivity, high-resolution, and high-precision three-dimensional force tactile sensors have become a research hotspot in current robot sensing technology. Summary of the invention

[0003] The present invention proposes a piezoelectric three-dimensional force tactile sensor based on the piezoelectric principle and a dome-shaped hemispherical flexible sensing structure, which can simultaneously measure the size and direction of the contact force.

[0004] The present invention discloses a piezoelectric three-dimensional force tactile sensor based on an array type PVDF, comprising a dome sensing layer, an upper metal electrode, a piezoelectric layer, a lower metal electrode and a substrate layer. The substrate layer is fixedly connected to the lower metal electrode; the lower metal electrode is a common electrode, the four piezoelectric layers arranged in the array are fixedly connected to the lower metal electrode, and each piezoelectric layer is fixedly connected to an upper metal electrode, each upper metal electrode is fixedly connected to the dome sensing layer, a spherical protrusion is provided on the side of the dome sensing layer that is not fixedly connected to the upper metal electrode, each upper metal electrode is symmetrical about the most convex point of the spherical protrusion, and the projection of each upper metal electrode on the substrate layer intersects with the projection of the spherical protrusion on the substrate layer; the lower metal electrode and each upper metal electrode are respectively connected to a lead wire.

[0005] Preferably, the piezoelectric layer is formed by stacking five mesh layers in sequence, and the mesh layer is formed by stacking two identical planar layers with a phase angle difference of 90°. The piezoelectric layer uses one of four different structures; the first structure is formed by stacking five identical mesh layers in sequence, and the planar layer in the mesh layer is formed by connecting a plurality of U-shaped parts in sequence, and the width of each U-shaped part of the planar layer is equal and they are arranged equidistantly; the second structure is formed by stacking five identical mesh layers in sequence, and the planar layer in the mesh layer is formed by connecting a plurality of U-shaped parts in sequence, and the width and spacing of each U-shaped part of the planar layer are arranged with a small middle and large sides; the third structure is formed by stacking five mesh layers in sequence, and the structures of the odd-numbered mesh layers and the even-numbered mesh layers in the five mesh layers are different. The plane layers in the odd-numbered mesh layers and the even-numbered mesh layers are formed by connecting a plurality of U-shaped pieces in sequence, and the width and spacing of the U-shaped pieces in the plane layers in the odd-numbered mesh layers are arranged in a manner that the middle is large and the two sides are small, while the width and spacing of the U-shaped pieces in the plane layers in the even-numbered mesh layers are arranged in a manner that the middle is small and the two sides are large; the fourth structure is formed by stacking five mesh layers in sequence, and the plane layers in the mesh layers are formed by connecting a plurality of U-shaped pieces in sequence, and in each mesh layer from bottom to top, the U-shaped pieces in the plane layers are arranged in a manner that the width and spacing are equal and are equidistant, and the width and spacing are gradually reduced in the middle and gradually increased on both sides.

[0006] More preferably, the piezoelectric layer adopts the third structure.

[0007] More preferably, the piezoelectric layer is obtained by immersing the printed component in a 70° C. deionized water bath for 2 hours to remove the ionic liquid.

[0008] More preferably, the parameters of the fused deposition modeling printing are as follows: nozzle temperature is 215° C., hot bed temperature is 75° C., printing speed is 15 mm / s, and printing acceleration is 500 mm / s.

[0009] More preferably, the wire preparation process used in the fused deposition modeling printing is as follows: first, take PVDF powder, ionic liquid and DMF organic solvent in a mass ratio of 100g:15g:237g, dissolve the ionic liquid in the DMF organic solvent under the stirring action of a stirring paddle to obtain a DMF solution; then, add the PVDF powder to the DMF solution and stir it magnetically until the PVDF powder is completely dissolved, and place the obtained liquid mixture in a vacuum oven to dry until the DMF is completely volatilized to obtain a PVDF solid doped with an ionic liquid, chop and granulate it, and place it in a single-screw extruder to extrude the wire.

[0010] More preferably, the outlet temperature of the single screw extruder is controlled to be 175° C., the rotation speed is 22 rpm, and the extrusion diameter is 1.65 to 1.75 mm.

[0011] More preferably, the thickness of the substrate layer is 1 mm, the thickness of the upper and lower metal electrodes is 80 μm, the length and width of the upper metal electrode are 17.5 mm, the thickness of the piezoelectric layer is 3 mm, and the length and width are 19 mm, the radius of the spherical protrusion of the dome sensing layer at the maximum cross-section is 25 mm, the height of the spherical protrusion is 1.8 mm, and the overall height of the dome sensing layer, upper metal electrode, piezoelectric layer, lower metal electrode and substrate layer is 6.8 mm.

[0012] Preferably, the dome sensing layer is prepared by a reverse molding curing process: liquid polydimethylsiloxane is poured into a mold, cured in an oven at 80° C. for 3 hours, and then the dome sensing layer is peeled off from the mold.

[0013] Preferably, the packaging process is as follows: each piezoelectric layer and a fixed upper metal electrode form a piezoelectric sensing unit, the piezoelectric layer of each piezoelectric sensing unit is fixedly connected to the lower metal electrode and then placed on the inverted dome sensing layer, so that the upper metal electrode of each piezoelectric sensing unit is fixedly connected to the dome sensing layer, and then liquid polydimethylsiloxane is rotationally coated on the lower metal electrode layer at a speed of 2000 rpm for 30 seconds to form a 1 mm thick substrate layer.

[0014] The present invention has the beneficial effects:

[0015] 1. The present invention adopts the principle of piezoelectric effect, has self-powered capability, does not require additional power supply, simplifies the signal processing circuit, and has high sensitivity. Among them, the three-dimensional flexible sensing structure in the form of a dome can effectively decompose the three-dimensional force and better transfer the stress to the piezoelectric layer. The present invention arranges the piezoelectric sensing unit in a 2*2 array, decouples the different charge outputs of different piezoelectric sensing units, accurately obtains the magnitude and direction information of the force, and the high symmetry of the structure also makes the output response of the piezoelectric sensing unit more sensitive.

[0016] 2. The present invention designs a three-dimensional network structure for the piezoelectric layer, and the three-dimensional structure reduces the modulus of the material due to the introduction of pores and the simulation of better porosity, selects a composite stacking structure with a higher potential output to obtain a larger effective strain, and selects a process for preparing polyvinylidene fluoride / ionic liquid composite materials using FDM to obtain a higher β-phase content, thereby generating a larger effective strain under the same load and a higher charge output under the same area, thereby improving the piezoelectric performance of the sensor.

[0017] 3. The overall structure of the present invention is simple, the manufacturing process is easy, and the highly symmetrical structure can facilitate the array expansion of the tactile sensing unit.

[0018] 4. The present invention has excellent comprehensive performance and can be promoted and applied in the fields of robot terminal dexterous hands, artificial prostheses and surgical manipulators. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a top view of the present invention.

[0020] Figure 2 It is a structural explosion diagram of the present invention.

[0021] Figure 3 Schematic diagram of the structure of the piezoelectric layer in the present invention.

[0022] Figure 4 Graph showing the output potential of the sensor as a function of normal force in an embodiment of the present invention.

[0023] Figure 5 Graph showing the output potential of the sensor according to the embodiment of the present invention changing with shear stress.

[0024] Figure 6 Graph showing the output potential of the sensor according to an embodiment of the present invention as a function of the direction of the three-dimensional force.

[0025] Figure 7 It is a comparison diagram of the potential output of the single-layer mesh layer structure in the embodiment of the present invention, the existing single-layer thin film shape piezoelectric structure and the existing single-layer columnar piezoelectric structure.

[0026] Figure 8 This is a comparison diagram of the potential output of a single-layer mesh structure with different pore sizes in an embodiment of the present invention.

[0027] Fig. 9 It is a structural diagram of four different piezoelectric layers stacked with different mesh layers in the present invention.

[0028] Fig.10 It is a comparison diagram of the potential output of four different piezoelectric layers stacked with different mesh layers in the present invention. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with the accompanying drawings.

[0030] like Figure 1 and Figure 2 As shown, a piezoelectric three-dimensional force tactile sensor based on array PVDF includes a dome sensing layer 1, an upper metal electrode 2, a piezoelectric layer 3, a lower metal electrode 4 and a substrate layer 5. The substrate layer is fixedly connected to the lower metal electrode; the lower metal electrode is a common electrode, the four piezoelectric layers arranged in the array are fixedly connected to the lower metal electrode, and each piezoelectric layer is fixedly connected to an upper metal electrode, each upper metal electrode is fixedly connected to the dome sensing layer, a spherical protrusion is provided on one side of the dome sensing layer that is not fixedly connected to the upper metal electrode, each upper metal electrode is symmetrical about the most convex point of the spherical protrusion, and the projection of each upper metal electrode on the substrate layer intersects with the projection of the spherical protrusion on the substrate layer; the lower metal electrode and each upper metal electrode are respectively connected to a lead.

[0031] like Figure 3 As shown, the piezoelectric layer is a three-dimensional structure formed by stacking five mesh layers in sequence; the mesh layer is formed by stacking two planar layers with completely identical structures and a phase angle difference of 90°.

[0032] like Fig. 9 As shown, the piezoelectric layer can have four different structures; the first structure is as follows Fig. 9 As shown in (a), it is composed of five identical mesh layers stacked in sequence, and the plane layer in the mesh layer is formed by connecting multiple U-shaped pieces in sequence. The U-shaped pieces of the plane layer have equal width and are arranged equidistantly. The second structure is as shown in Fig. 9 As shown in (b), it is composed of five identical mesh layers stacked in sequence, and the plane layer in the mesh layer is composed of multiple U-shaped pieces connected in sequence. The width and spacing of each U-shaped piece in the plane layer are arranged in a small middle and large sides; the third structure is as follows Fig. 9 As shown in (c), five mesh layers are stacked in sequence. The structures of the odd-numbered mesh layers and the even-numbered mesh layers are different. The plane layers in the odd-numbered mesh layers and the even-numbered mesh layers are connected in sequence by multiple U-shaped pieces. The width and spacing of the U-shaped pieces in the plane layers in the odd-numbered mesh layers are arranged in a large middle and small arrangement on both sides, while the width and spacing of the U-shaped pieces in the plane layers in the even-numbered mesh layers are arranged in a small middle and large arrangement on both sides. The fourth structure is as follows: Fig. 9 As shown in (d), five mesh layers are stacked in sequence, and the plane layer in the mesh layer is connected in sequence by multiple U-shaped parts, and in each mesh layer from bottom to top, the U-shaped parts of the plane layer are arranged from equal width and equidistantly to the width and spacing gradually decreasing in the middle position and gradually increasing on both sides.

[0033] The piezoelectric layer was obtained by immersing the printed component by fused deposition modeling (FDM) in a 70°C deionized water bath for 2 hours to remove the ionic liquid. The printing parameters were as follows: nozzle temperature was 215°C, hot bed temperature was 75°C, printing speed was 15 mm / s, printing acceleration was 500 mm / s, and the slicing software was Bambu Studio; The preparation process of the wire used for printing is as follows: First, take PVDF powder, ionic liquid ([C2mim][BF4]) and DMF organic solvent (N, N-dimethylformamide) in a mass ratio of 100g:15g:237g, dissolve the ionic liquid in the DMF organic solvent under the stirring action of a stirring paddle to ensure that the ionic liquid is evenly dispersed to obtain a DMF solution; then, add the PVDF powder to the DMF solution at a temperature of 60°C and stir magnetically, control the stirring speed to 600r / min, and stir for 6h until the PVDF powder is completely dissolved, place the obtained liquid mixture in a vacuum oven at a temperature of 70°C and dry until DMF is completely volatilized (which can be judged by weighing), and obtain a PVDF solid doped with an ionic liquid, chop and granulate it, and place it in a single-screw extruder to extrude the wire, wherein the outlet temperature of the single-screw extruder is controlled to be 175°C, the rotation speed is 22rpm, and the extrusion diameter is 1.65-1.75mm.

[0034] In the following analysis, the structure adopted by the present invention is: the thickness of the substrate layer is 1mm, the upper and lower metal electrodes are made of copper foil with a thickness of 80μm, the length and width of the upper metal electrode are 17.5mm, the thickness of the piezoelectric layer is 3mm, the length and width are 19mm, the radius of the spherical protrusion of the dome sensing layer at the maximum cross-section is 25mm, the height of the spherical protrusion is 1.8mm, and the overall height of the piezoelectric three-dimensional force tactile sensor of the present invention is 6.8mm.

[0035] If the piezoelectric layer structure of the piezoelectric three-dimensional force tactile sensor of the present invention adopts Fig. 9 In the single-layer mesh layer in (c), when the dome sensing layer is subjected to a normal force, the potential output of the four arrayed piezoelectric layers increases linearly with the increase of the normal force. For the piezoelectric layer B, when the normal force is 10N, its potential output is the highest, reaching 7.32V, and the sensitivity (the slope obtained by linear fitting the relationship between the potential of the piezoelectric layer B and the normal force data) is 0.72V / N. Figure 4 The potential outputs of the four piezoelectric layers A to D indicate that the piezoelectric three-dimensional force tactile sensor of the present invention has a good response to the normal force.

[0036] If the piezoelectric layer structure of the piezoelectric three-dimensional force tactile sensor of the present invention adopts Fig. 9In the single-layer mesh layer (c), when the dome sensing layer is subjected to shear stress from the piezoelectric layer B to the piezoelectric layer A, the piezoelectric layers A and D are deformed by the pressure, and a positive potential output is obtained. The piezoelectric layers B and C are deformed by the tensile force, and a negative potential output is obtained. Under the shear force, the piezoelectric three-dimensional force tactile sensor of the present invention has a sensitivity of 0.52V / N (the sensitivity of the piezoelectric layers B and D can reach 0.52V / N). Figure 5 shown.

[0037] If the piezoelectric layer structure of the piezoelectric three-dimensional force tactile sensor of the present invention adopts Fig. 9 In the single-layer mesh layer in (c), when the dome sensing layer is subjected to a three-dimensional force with an angle φ between the Y direction and the X direction varying from 0 to 360°, the changing trends of the piezoelectric layers A, D and the piezoelectric layers B, C are shown in the figure. Figure 6 As shown, the three-dimensional force is finally mechanically decoupled by outputting different electric potentials to the four piezoelectric layers.

[0038] Directly to the present invention Fig. 9 The single-layer mesh layer structure in (c), the existing single-layer film shape (Plate) piezoelectric structure and the existing single-layer columnar piezoelectric structure are compared by finite element simulation. Under the same shape (length, width, height) size, it can be seen that when subjected to the normal force of the same change law, the potential output of the existing single-layer film shape (Plate) piezoelectric structure is the lowest, while the potential output of the single-layer mesh layer piezoelectric structure of the present invention is better than that of the existing single-layer columnar piezoelectric structure, and the sensitivity reaches 0.8V / N, as shown in FIG. Figure 7 shown.

[0039] Directly to the present invention Fig. 9 The single-layer mesh structure in (a) is simulated and compared with different porosities for potential output finite element simulation. The average surface potential output of the mesh structure with a porosity of 22% is 1.97V, and the maximum is 2.33V; the average surface potential output of the mesh structure with a porosity of 33% is 2.84V, and the maximum is 3.36V; the average surface potential output of the mesh structure with a porosity of 40% is 3.79V, and the maximum is 4.38V. Figure 8 As shown in Figure 2, it can be concluded that at a certain porosity, the potential output is positively correlated with the porosity.

[0040] right Fig. 9 Four different piezoelectric layer structures (including the overall five-layer mesh layer) were simulated and compared for potential output by finite element simulation, and a 5N normal force load was applied. It can be seen that the present invention adopts Fig. 9 The piezoelectric layer structure in (c) has the best potential output, with a maximum value of 10.3V. Fig.10 As shown, therefore Fig. 9 The piezoelectric layer structure in (c) is the preferred structure to obtain higher sensitivity.

[0041] The basic working principle of the present invention is as follows:

[0042] When the dome sensing layer is acted upon by an external force, the external force is transmitted to the upper metal electrode and the piezoelectric layer. The charge inside the piezoelectric layer will gather toward the force-bearing surface, and the amount of charge will change with the change of the external force. The piezoelectric effect is used to convert the applied contact force into an electrical signal. Among them, the dome sensing layer is provided with a spherical protrusion. Compared with the two-dimensional plane sensing structure, the spherical protrusion can effectively concentrate the stress in the central area of ​​the sensor and better transfer the stress to the piezoelectric layer. Since the output charge increases with the increase of stress, a highly sensitive tactile sensor can be obtained. When a three-dimensional force acts on the dome sensing layer, due to the symmetrical structure, part of the bottom of the dome sensing layer is subjected to pressure and part is subjected to tension. Therefore, under the action of different three-dimensional forces, the four piezoelectric layers will obtain different charge outputs. Finally, the size and direction of the three-dimensional force are determined by decoupling the size of the charge output in the four piezoelectric layers.

[0043] Among them, the piezoelectric layer of the present invention is different from the mainstream two-dimensional PVDF piezoelectric film structure, and a three-dimensional structure is selected to obtain a higher β-phase content and better piezoelectric performance. The principle of FDM preparation of PVDF / IL composite three-dimensional piezoelectric layer (piezoelectric layer structure before immersion in deionized water to remove ionic liquid, that is, the component after fused deposition modeling printing) is that on the one hand, IL (ionic liquid) can not only induce and maintain polar β phase, but also improve the warping phenomenon of PVDF during FDM processing. In the PVDF molecular chain, the ion-dipole interaction between the positive imidazolium ions of IL and the negatively charged -CF2 in the PVDF molecular chain can overcome the energy barrier of PVDF from α-conformation to β-conformation, and promote the complete conversion of α-PVDF into β-PVDF crystal form. This strong ion-dipole interaction allows β-PVDF to remain and stably exist in the molten state of 175°C and during FDM printing at 215°C. In addition, during the FDM printing process, the shearing action of the FDM nozzle can also promote the directional arrangement of dipoles in β-PVDF, and obtain a PVDF piezoelectric layer with self-polarization performance. In general, under the action of the ion-dipole interaction between IL and PVDF and the shear force of the FDM small-diameter nozzle, a higher β-phase content and better piezoelectric performance can be obtained to a certain extent. Moreover, the three-dimensional structure of the piezoelectric layer of the present invention is a structure in which five layers of mesh layers with pores are stacked in sequence. The mesh structure has a greater potential output than the thin film structure without pores, because the introduction of pores reduces the modulus of the material, thereby generating a greater effective strain under the same load; further, the present invention simulates by changing the porosity to obtain a better porosity under the same area, and its charge output is higher; further, the mesh layers with different pore arrangement rules are compositely stacked to obtain a higher piezoelectric output.

Claims

1. A piezoelectric three-dimensional force tactile sensor based on array PVDF, comprising an upper metal electrode, a piezoelectric layer, a lower metal electrode and a substrate layer, characterized in that: It also includes a dome sensing layer; the substrate layer is fixedly connected to the lower metal electrode; the lower metal electrode is a common electrode, the four piezoelectric layers arranged in an array are all fixedly connected to the lower metal electrode, and each piezoelectric layer is fixedly connected to an upper metal electrode, each upper metal electrode is fixedly connected to the dome sensing layer, a spherical protrusion is provided on the side of the dome sensing layer that is not fixedly connected to the upper metal electrode, each upper metal electrode is symmetrical about the most convex point of the spherical protrusion, and the projection of each upper metal electrode on the substrate layer intersects with the projection of the spherical protrusion on the substrate layer; the lower metal electrode and each upper metal electrode are respectively connected to a lead.

2. The piezoelectric three-dimensional force tactile sensor based on array PVDF according to claim 1, characterized in that: The piezoelectric layer is formed by stacking five mesh layers in sequence, and the mesh layer is formed by stacking two identical planar layers with a phase angle difference of 90°; the piezoelectric layer selects one of four different structures; the first structure is formed by stacking five identical mesh layers in sequence, and the planar layer in the mesh layer is formed by connecting a plurality of U-shaped parts in sequence, and the width of each U-shaped part of the planar layer is equal and they are arranged equidistantly; the second structure is formed by stacking five identical mesh layers in sequence, and the planar layer in the mesh layer is formed by connecting a plurality of U-shaped parts in sequence, and the width and spacing of each U-shaped part of the planar layer are arranged with a small middle and large sides; the third structure is formed by stacking five mesh layers in sequence The fourth structure is formed by stacking five mesh layers in sequence, and the plane layers in the mesh layers are formed by connecting a plurality of U-shaped parts in sequence, and in each mesh layer from bottom to top, the U-shaped parts of the plane layers are changed from having equal width and being arranged at equal distances to having width and spacing gradually decreasing in the middle and increasing at both sides.

3. The piezoelectric three-dimensional force tactile sensor based on array PVDF according to claim 2, characterized in that: The piezoelectric layer adopts the third structure.

4. A piezoelectric three-dimensional force tactile sensor based on array PVDF according to claim 1, 2 or 3, characterized in that: The piezoelectric layer is obtained by immersing the printed component in a 70° C. deionized water bath for 2 hours to remove the ionic liquid.

5. The piezoelectric three-dimensional force tactile sensor based on array PVDF according to claim 4, characterized in that: The parameters of the fused deposition modeling printing are as follows: nozzle temperature is 215° C., hot bed temperature is 75° C., printing speed is 15 mm / s, and printing acceleration is 500 mm / s.

6. The piezoelectric three-dimensional force tactile sensor based on array PVDF according to claim 4, characterized in that: The wire preparation process used in the fused deposition modeling printing is as follows: first, PVDF powder, ionic liquid and DMF organic solvent with a mass ratio of 100g:15g:237g are taken, and the ionic liquid is dissolved in the DMF organic solvent under the stirring action of a stirring paddle to obtain a DMF solution; then, the PVDF powder is added to the DMF solution and magnetically stirred until the PVDF powder is completely dissolved, and the obtained liquid mixture is placed in a vacuum oven for drying until the DMF is completely volatilized to obtain a PVDF solid doped with an ionic liquid, which is chopped and granulated, and placed in a single-screw extruder to extrude the wire.

7. The piezoelectric three-dimensional force tactile sensor based on array PVDF according to claim 6, characterized in that: The outlet temperature of the single-screw extruder was controlled to be 175° C., the rotation speed was controlled to be 22 rpm, and the extrusion diameter was controlled to be 1.65-1.75 mm.

8. The piezoelectric three-dimensional force tactile sensor based on array PVDF according to claim 1, characterized in that: The thickness of the substrate layer is 1mm, the thickness of the upper and lower metal electrodes is 80μm, the length and width of the upper metal electrode are 17.5mm, the thickness of the piezoelectric layer is 3mm, and the length and width are 19mm. The radius of the maximum cross-section of the spherical protrusion of the dome sensing layer is 25mm, and the height of the spherical protrusion is 1.8mm. The overall height of the dome sensing layer, upper metal electrode, piezoelectric layer, lower metal electrode and substrate layer is 6.8mm.

9. The piezoelectric three-dimensional force tactile sensor based on array PVDF according to claim 1, characterized in that: The dome sensing layer is prepared by a reverse molding curing process: liquid polydimethylsiloxane is poured into a mold, cured in an 80° C. oven for 3 hours, and then the dome sensing layer is peeled off from the mold.

10. The piezoelectric three-dimensional force tactile sensor based on array PVDF according to claim 1, characterized in that: The packaging process is as follows: each piezoelectric layer and an upper metal electrode are fixedly connected to form a piezoelectric sensing unit. The piezoelectric layer of each piezoelectric sensing unit is fixedly connected to the lower metal electrode and then placed on the inverted dome sensing layer, so that the upper metal electrode of each piezoelectric sensing unit is fixedly connected to the dome sensing layer. Then, liquid polydimethylsiloxane is spin-coated on the lower metal electrode layer at a speed of 2000 rpm for 30 seconds to form a 1 mm thick substrate layer.

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