Flexible touch sensor and manufacturing method thereof

Abstract

The invention discloses a flexible touch sensor and a manufacturing method thereof. The flexible touch sensor comprises a flexible substrate, a pressure sensitive layer and a pressure electrode, the flexible base body is provided with a cavity, a stress end face is formed on the outer wall of the flexible base body, and the stress end face and the cavity are arranged in a spaced mode. The pressure sensitive layer is arranged in the flexible base body, at least part of the pressure sensitive layer coincides with the projection of the cavity on the stress end face, and the pressure sensitive layer deforms when subjected to external force; the pressure electrode is arranged on the flexible substrate and connected with the pressure sensitive layer. According to the scheme, the part, directly facing the cavity, of the pressure sensitive layer can deform towards the cavity, the hindering effect of the flexible base body on the part of the pressure sensitive layer is relieved, the pressure sensitive layer can deform towards the cavity when bearing small external force, the measuring sensitivity is improved, and meanwhile the measuring accuracy is improved. And in combination with the deformation of the pressure sensitive layer following the flexible substrate and the deformation of the pressure sensitive layer in the cavity part, the measurement range of the sensor is expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of tactile sensors, and in particular to a flexible tactile sensor and a manufacturing method thereof. Background Art

[0002] Electronic skin is the first organ of a robot to respond to external stimuli such as pressure, touch, vibration and temperature, and external stimulus perception is usually achieved through tactile sensors.

[0003] Publication number CN112213016A discloses a piezoelectric flexible tactile sensor and tactile sensing structure, wherein a rigid array unit includes several rigid bodies, which are arranged on the flexible upper substrate and fixedly combined with the flexible upper substrate. The contact stress acting on the flexible upper substrate is transmitted to the piezoelectric sensing unit through the flexible upper substrate and the rigid array unit, and the piezoelectric sensing unit senses the magnitude of the contact stress, causing the piezoelectric sensing unit to deform and destroy the balance of its electric dipole moment to generate a potential difference.

[0004] However, the piezoelectric sensing unit in this patent is placed between the rigid-flexible substrate and the flexible lower substrate. The rigid-flexible substrate and the flexible lower substrate still have certain obstacles to the deformation of the piezoelectric sensing unit, which is not conducive to improving the sensitivity of the sensor. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned technical deficiencies and propose a flexible tactile sensor and a manufacturing method thereof, so as to solve the technical problem in the prior art that the piezoelectric sensing unit is placed between a rigid-flexible substrate and a flexible lower substrate, and the flexible lower substrate and the flexible substrate still have certain obstacles to the deformation of the piezoelectric sensing unit, which is not conducive to improving the sensitivity of the sensor.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a flexible tactile sensor, comprising: The flexible substrate has a cavity and a force-bearing end surface formed on its outer wall, wherein the force-bearing end surface is spaced apart from the cavity; a pressure-sensitive layer disposed inside the flexible substrate and between the cavity and the force-bearing end surface, and at least partially overlapping with a projection of the cavity on the force-bearing end surface, wherein the pressure-sensitive layer deforms when subjected to an external force and is used to convert pressure into an electrical signal; and The pressure electrode is provided on the flexible substrate and connected to the pressure sensitive layer.

[0007] In some embodiments, the pressure-sensitive layer extends in a direction parallel to the force-bearing end surface, and a projection area of ​​the portion to which the cavity belongs on the force-bearing end surface is a first area; The flexible tactile sensor also includes a protruding structure, which is arranged in the flexible substrate and located on the side of the pressure-sensitive layer close to the force-bearing end surface, and the projection area on the force-bearing end surface is a second area, and the second area falls within the first area.

[0008] In some embodiments, the cavity is symmetrically arranged at both ends of the extension direction of the pressure sensitive layer; The geometric center of the protruding structure falls on the symmetry axis of the cavity.

[0009] In some embodiments, the protruding structure and the pressure-sensitive layer are spaced apart from each other along an extending direction of the pressure-sensitive layer.

[0010] In some embodiments, the protruding structure is configured as a hemisphere and has an arc-shaped convex surface and a force-transmitting plane on its surface, the arc-shaped convex surface is close to the force-bearing end surface, and the force-transmitting plane is close to the cavity.

[0011] In some embodiments, the flexible tactile sensor further includes a temperature-sensitive layer and a temperature electrode, wherein the temperature-sensitive layer is disposed in the flexible substrate and is located on a side of the pressure-sensitive layer away from the force-bearing end surface and is offset from a portion of the pressure-sensitive layer exposed to the cavity; the temperature electrode is disposed in the flexible substrate and is partially located on an outer wall of the flexible substrate and is connected to the temperature-sensitive layer; The temperature sensitive layer changes its resistance when the temperature changes.

[0012] In some embodiments, the cavity is open on a side away from the force-bearing end surface; One end of the temperature sensitive layer extends to a side wall where the cavity intersects the opening.

[0013] In some embodiments, the pressure-sensitive layer has an expansion section and a main section connected thereto, and the expansion section coincides with a projection of the cavity on the force-bearing end surface; The temperature sensitive layer, the temperature electrode, the pressure electrode and the main body segment are located on the same side of the cavity.

[0014] In some embodiments, the flexible substrate includes a polyimide layer, a silicon oxide layer, an insulating layer, and an encapsulation layer, wherein the polyimide layer, the silicon oxide layer, the pressure-sensitive layer, the insulating layer, the temperature-sensitive layer, and the encapsulation layer are stacked in sequence, and the pressure-sensitive layer is coated between the silicon oxide layer and the insulating layer, and the temperature-sensitive layer is coated between the insulating layer and the encapsulation layer; The cavity is formed between the encapsulation layer and the insulating layer.

[0015] In addition, the present invention also provides a method for manufacturing a flexible tactile sensor, which is used to manufacture the flexible tactile sensor as described in any one of the above items, comprising the steps of: preparing the flexible substrate without the cavity, and preparing the pressure-sensitive layer inside the flexible substrate during the preparation of the flexible substrate; Then, a photoresist is spin-coated on the surface of the flexible substrate, and a development and patterning process is performed. The photoresist coating is used as a mask layer for an electrode etching process, and dry etching is performed to form an electrode opening. The pressure electrode is prepared in the electrode opening by an electroplating process. Then, a photosensitive coating is spin-coated on the surface of the flexible substrate and used as a base for preparing the cavity. The cavity is prepared by a photolithography process, and the pressure electrode is opened.

[0016] Compared with the prior art, in the flexible tactile sensor provided by the present invention, the pressure-sensitive layer is placed in a flexible substrate, so that when the force-bearing end face of the flexible substrate is subjected to external force, the force can be transmitted to the pressure-sensitive layer through the flexible substrate, and drive the pressure-sensitive layer to deform, thereby realizing the external force measurement. And because part of the pressure-sensitive layer is facing the cavity, the part of the pressure-sensitive layer facing the cavity can be deformed toward the cavity, reducing the obstruction of the flexible substrate on the pressure-sensitive layer in this part. In this way, the pressure-sensitive layer can be deformed toward the cavity when subjected to a small external force, and the pressure is converted into an electrical signal and output through the pressure electrode, thereby improving the measurement sensitivity. At the same time, combined with the deformation of the pressure-sensitive layer following the deformation of the flexible substrate and its deformation in the cavity, the measurement range of the sensor is expanded. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a perspective view of a flexible tactile sensor provided by one embodiment of the present invention; Figure 2 yes Figure 1 Front view of the flexible tactile sensor; Figure 3 yes Figure 1 Top view of the flexible tactile sensor. Figure 4 is a cross-sectional view of a flexible tactile sensor provided by another embodiment of the present invention; Figure 5 is a schematic diagram of a flexible tactile system according to an embodiment of the present invention; Figure 6 yes Figure 4 Schematic diagram of the flexible tactile sensor fabrication process; Figure 7 yes Figure 4 Schematic diagram of the process of manufacturing a flexible tactile sensor from preparing a bare silicon wafer to growing a pressure-sensitive layer; Figure 8 yes Figure 4 Schematic diagram of the process from growing the insulating layer to etching the electrodes during the fabrication of the flexible tactile sensor; Figure 9 yes Figure 4 Schematic diagram of the process of opening the cavity by electroplating metal electrodes and coating photosensitive PI in the flexible tactile sensor fabrication process; Figure 10 yes Figure 4 Schematic diagram of the process of self-removing bare silicon and encapsulating electronic skin devices during the production of flexible tactile sensors.

[0018] Description of reference numerals: 1. Flexible tactile sensor; 2. Flexible substrate; 2a. Cavity; 2b. Electrode opening; 21. Force-bearing end face; 22. Polyimide layer; 23. Silicone oxide layer; 24. Insulation layer; 25. Encapsulation layer; 26. Silicone layer; 3. Pressure-sensitive layer; 31. Range extension section; 32. Main section; 4. Pressure electrode; 5. Protrusion structure; 6. Temperature-sensitive layer; 7. Temperature electrode; 8. Bare silicon wafer. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0020] In order to solve the technical problem in the prior art that the piezoelectric sensing unit is placed between the rigid-flexible substrate and the flexible lower substrate, and the rigid-flexible substrate and the flexible lower substrate still have certain obstacles to the deformation of the piezoelectric sensing unit, which is not conducive to improving the sensitivity of the sensor, the present invention provides a flexible tactile sensor, which can enable the pressure-sensitive layer to deform toward the cavity when subjected to a small external force, thereby improving the measurement sensitivity. At the same time, combined with the deformation of the pressure-sensitive layer following the flexible substrate and its deformation in the cavity, the measurement range of the sensor is expanded.

[0021] See also Figures 1 to 3 , Figures 1 to 3This is a schematic structural diagram of a flexible tactile sensor 1 according to an embodiment of the present invention. The flexible tactile sensor 1 includes a flexible substrate 2, a pressure-sensitive layer 3, and a pressure electrode 4. The flexible substrate 2 has a cavity 2a and a force-bearing end surface 21 formed on its outer wall, spaced apart from the cavity 2a. The pressure-sensitive layer 3 is disposed within the flexible substrate 2, between the cavity 2a and the force-bearing end surface 21, and at least partially overlaps with the projection of the cavity 2a on the force-bearing end surface 21. The pressure-sensitive layer 3 deforms when subjected to an external force, thereby converting pressure into an electrical signal. The pressure electrode 4 is disposed on the flexible substrate 2 and connected to the pressure-sensitive layer 3. Specifically, the pressure electrode 4 is at least partially located on the outer wall of the flexible substrate 2.

[0022] In the flexible tactile sensor 1 provided by the present invention, the pressure-sensitive layer 3 is placed in the flexible substrate 2, so that when the force-bearing end surface 21 of the flexible substrate 2 is subjected to external force, the force can be transmitted to the pressure-sensitive layer 3 through the flexible substrate 2, and the pressure-sensitive layer 3 is driven to deform, thereby realizing the external force measurement. And because the part of the pressure-sensitive layer 3 is facing the cavity 2a, the part of the pressure-sensitive layer 3 facing the cavity 2a can be deformed toward the cavity 2a, reducing the obstruction of the flexible substrate 2 on the pressure-sensitive layer 3 in this part. In this way, the pressure-sensitive layer 3 can be deformed toward the cavity 2a when subjected to a small external force, and the pressure is converted into an electrical signal and output through the pressure electrode 4, thereby improving the measurement sensitivity. At the same time, combined with the deformation of the pressure-sensitive layer 3 following the flexible substrate 2 and its deformation in the cavity 2a, the measurement range of the sensor is expanded.

[0023] It should be noted that the pressure-sensitive layer 3 converts pressure into an electrical signal to enable external force measurement. It can be a structural layer that generates resistance, capacitance, or piezoelectric response based on changes in external pressure. Specifically, in this solution, the pressure-sensitive layer 3 converts changes in external pressure into changes in resistance. The pressure-sensitive layer 3 is configured as a pressure grid, which can be an Au (gold) film or other metals such as nickel-chromium alloy or constantan. The pressure grid is connected to an external power source via pressure electrodes 4. Consequently, when the pressure grid deforms, the resistance changes, which in turn changes the current flow, enabling external force measurement.

[0024] In addition, in this embodiment, the pressure grid is configured as a corrugated shape with bends, and the number of bends in the pressure grid is designed according to requirements to further improve measurement accuracy. In this embodiment, the pressure sensitive layer 3 partially overlaps with the orthographic projection of the cavity 2a on the force-bearing end surface 21.

[0025] In one embodiment, the pressure sensitive layer 3 is partially exposed in the cavity 2 a , thereby completely eliminating the obstruction of the flexible substrate 2 on the portion of the pressure sensitive layer 3 , further improving the measurement accuracy of the sensor.

[0026] In one embodiment, the pressure-sensitive layer 3 extends in a direction parallel to the force-bearing end surface 21, and the projection area of ​​the portion to which the cavity 2a belongs on the force-bearing end surface 21 is the first area; the flexible tactile sensor 1 also includes a protrusion structure 5, which is arranged in the flexible substrate 2 and is located on the side of the pressure-sensitive layer 3 close to the force-bearing end surface 21, and the projection area on the force-bearing end surface 21 is the second area, and the second area falls within the first area.

[0027] In this embodiment, the raised structure 5 is positioned directly opposite the cavity 2a. Therefore, when force is applied to the force-bearing end surface 21, the force is transmitted through the raised structure 5 to the cavity 2a, thereby causing deformation of the pressure-sensitive layer 3, further improving measurement accuracy. It should be noted that the outer diameter of the raised structure 5 should preferably not exceed 500 microns. If the raised structure 5 is too large, it will be difficult to cover the raised structure 5 when the surface layer is encapsulated.

[0028] Furthermore, it should be understood that see Figure 4 The projection direction of the first area of ​​cavity 2a on the force-bearing end surface 21 is the same as the projection direction of the second area of ​​protrusion structure 5 on the force-bearing end surface 21. Specifically, in this case, the first area is the area of ​​the orthographic projection of the portion of cavity 2a on the force-bearing end surface 21, and correspondingly, the second area is the area of ​​the orthographic projection of protrusion structure 5 on the force-bearing end surface 21, shortening the transmission distance during force measurement.

[0029] In one embodiment, the cavity 2 a is symmetrically arranged at both ends of the pressure-sensitive layer 3 in the extension direction; the geometric center of the protruding structure 5 falls on the symmetry axis of the cavity 2 a.

[0030] In this embodiment, the cavity 2a is symmetrically arranged as above, and the geometric center of the protruding structure 5 is placed on the symmetry axis of the cavity 2a, so that the force transmitted through the protruding structure 5 is more uniform, thereby improving the measurement accuracy. In one embodiment, the protruding structure 5 is arranged in the form of a rectangular cavity.

[0031] In addition, it should be understood that the distance between the protruding structure 5 and the pressure-sensitive layer 3 in the thickness direction of the flexible substrate 2 should be as close as possible. The closer the protruding structure 5 is to the pressure-sensitive layer 3, the easier it is for the external load on the protruding structure 5 to be transmitted to the pressure-sensitive layer 3, thereby making it easier for the pressure grid wire to deform along with the protruding structure 5, and the higher the sensitivity of the sensor.

[0032] In one embodiment, the protruding structure 5 and the pressure-sensitive layer 3 are spaced apart from each other along the extending direction of the pressure-sensitive layer 3 .

[0033] In this embodiment, the raised structure 5 is spaced apart from the pressure-sensitive layer 3 as described above to prevent the raised structure 5 from covering the top of the pressure-sensitive layer 3 , thereby preventing the raised structure 5 from damaging the strain-sensitive layer when a large impact is applied to the raised structure 5 .

[0034] It should be noted that the protruding structure 5 can be configured as a cuboid, a cone or other forms.

[0035] In one embodiment, the protruding structure 5 is hemispherical and has an arc-shaped convex surface and a force-transmitting plane on its surface. The arc-shaped convex surface is close to the force-bearing end surface 21, and the force-transmitting plane is close to the cavity 2a.

[0036] In this embodiment, the raised structures 5 are configured as hemispheres and arranged as described above, enabling uniform force transmission. Furthermore, it should be understood that the hardness of the raised structures 5 is higher than that of the flexible substrate 2. Specifically, in this embodiment, the raised structures 5 are UV (ultraviolet) epoxy resin microspheres.

[0037] In one embodiment, the flexible tactile sensor 1 further includes a temperature-sensitive layer 6 and a temperature electrode 7. The temperature-sensitive layer 6 is disposed in the flexible substrate 2 and is located on the side of the pressure-sensitive layer 3 away from the force-bearing end surface 21, and is staggered from the portion of the pressure-sensitive layer 3 exposed to the cavity 2a. The temperature electrode 7 is disposed in the flexible substrate 2 and is partially located on the outer wall of the flexible substrate 2 and is connected to the temperature-sensitive layer 6; wherein the temperature-sensitive layer 6 changes its resistance when the temperature changes.

[0038] In this embodiment, a temperature-sensitive layer 6 is also provided to simultaneously measure external pressure and temperature, improving practicality. Placing the temperature-sensitive layer 6 at the bottom of the pressure-sensitive layer 3 prevents the temperature-sensitive layer 6 from being affected by pressure, thereby improving temperature measurement accuracy.

[0039] It should be noted that the temperature-sensitive layer 6 is a functional layer that generates changes in resistance, conductivity, or physical properties in response to temperature. It can be configured as a thermosensitive ceramic layer, a metal composite layer, or other forms. Specifically, in this embodiment, the temperature-sensitive layer 6 is configured as a temperature-sensitive grid, and the metal used can be a metal such as Pt.

[0040] In one embodiment, the cavity 2a is open on a side away from the force-bearing end surface 21; one end of the temperature-sensitive layer 6 extends to the side wall where the cavity 2a intersects with the opening.

[0041] In this embodiment, the cavity 2a is opened on the side away from the force-bearing end surface 21. On the one hand, it is convenient to form the cavity 2a by photoresist development, thereby improving production convenience; on the other hand, it enables part of the temperature-sensitive layer 6 to be connected to the outside through the cavity 2a, thereby facilitating the temperature-sensitive layer 6 to accurately sense the ambient temperature.

[0042] In one embodiment, the pressure-sensitive layer 3 has an expansion section 31 and a main section 32 connected to each other, and the expansion section 31 coincides with the projection of the cavity 2a on the force-bearing end surface 21; the temperature-sensitive layer 6, the temperature electrode 7, the pressure electrode 4 and the main section 32 are located on the same side of the cavity 2a.

[0043] In this embodiment, the temperature sensitive layer 6, temperature electrode 7, pressure electrode 4 and main body section 32 are located on the same side of the cavity 2a, so as to facilitate the connection of electrodes to corresponding sensitive layers, simplify wiring, and facilitate the reduction of sensor size.

[0044] It should be noted that the flexible substrate 2 can be entirely configured to be polydimethylsiloxane (PDMS), polyimide (PI), polyester (PET) or other forms.

[0045] In one embodiment, the flexible substrate 2 includes a polyimide layer 22, a silicon oxide layer 23, an insulating layer 24, and an encapsulation layer 25. The polyimide layer 22, the silicon oxide layer 23, the pressure-sensitive layer 3, the insulating layer 24, the temperature-sensitive layer 6, and the encapsulation layer 25 are stacked in sequence, and the pressure-sensitive layer 3 is coated between the silicon oxide layer 23 and the insulating layer 24, and the temperature-sensitive layer 6 is coated between the insulating layer 24 and the encapsulation layer 25; the cavity 2a is formed between the encapsulation layer 25 and the insulating layer 24.

[0046] In this embodiment, a silicon oxide layer 23 is deposited on the polyimide layer 22 to prevent the diffusion of the pressure sensitive layer 3 and increase the metal adhesion of the pressure sensitive layer 3. The temperature sensitive layer 6 and the pressure sensitive layer 3 are isolated by the insulating layer 24 to ensure the normal operation of the two sensitive layers.

[0047] It should be noted that the insulating layer 24 can be made of a flexible pure PI film, a PDMS-based composite material, a graphene-PDMS material or other materials.

[0048] Furthermore, it should be understood that in this solution, the deeper cavity 2a, the greater the change in the pressure grid resistance, that is, the greater the change in the pressure grid resistance, thus increasing the sensor's range. At the same time, cavity 2a cannot pass inspection. When the polyimide film exceeds 100 microns, the polyimide film produced by low-speed microelectromechanical systems (MEMS) spin coating is uneven. Furthermore, the thicker the polyimide film, the higher the hardness of the entire device, making it unsuitable for curved and irregular surfaces.

[0049] Also, see Figure 5 The present solution also provides a flexible tactile system, which includes a plurality of flexible tactile sensors 1 as described above, wherein the plurality of flexible tactile sensors 1 are arranged in an array, and the cavities 2a in the plurality of flexible tactile sensors 1 are alternately defined as first cavities 2a and second cavities 2a in sequence, and the second cavities 2a are filled.

[0050] In this embodiment, one cavity 2a in any two adjacent flexible tactile sensors 1 is filled, eliminating the cavity 2a in one of the flexible tactile sensors 1. This allows for a portion of the flexible tactile sensor 1 to retain the cavity 2a to improve pressure sensitivity and range, while also allowing for a temperature-compensated, non-cavity module design, i.e., a solid structure. Consequently, in a cavity-free flexible tactile sensor 1, even if the temperature within the sensor changes, the resistance of the pressure grid in that portion is not easily affected by the temperature and remains unchanged due to the non-strain of the flexible substrate 2.

[0051] Therefore, the flexible tactile system can achieve complementarity through the flexible tactile sensor 1 with the cavity 2 a and the flexible tactile sensor 1 without the cavity 2 a, thereby improving measurement accuracy.

[0052] It should be understood that in this solution, a single grid wire is connected using a two-wire method. However, array-type flexible tactile systems (such as 2×2, 3×3, 4×4, 6×4, or 8×4) use serial wiring. Both the pressure module and the temperature module use this wiring method, which greatly reduces the system size.

[0053] Also, see Figures 6 to 10 The present invention further provides a method for manufacturing a flexible tactile sensor 1, which is used to manufacture the flexible tactile sensor 1 as described above. A first embodiment thereof comprises the following steps: A flexible substrate 2 without a cavity 2a is prepared, and during the process of preparing the flexible substrate 2, a pressure-sensitive layer 3 is prepared inside the flexible substrate 2; Then, a photoresist is spin-coated on the surface of the flexible substrate 2 and subjected to a development and patterning process. The photoresist coating is used as a mask layer for an electrode etching process, and dry etching is performed to form an electrode opening 2b. A pressure electrode 4 is then prepared in the electrode opening 2b by an electroplating process. A photosensitive coating is then spin-coated on the surface of the flexible substrate 2 and used as a base for preparing the cavity 2 a . The cavity 2 a is prepared by a photolithography process, and the pressure electrode 4 is opened.

[0054] In this embodiment, the base layer of the flexible substrate 2 includes a polyimide layer 22, a silicon oxide layer 23, an insulating layer 24, and an encapsulation layer 25. The fabrication process begins with preparing a bare silicon wafer 8, spin-coating a first layer of PI adhesive, and curing it to form the flexible substrate of the electronic skin sensor. Silicon oxide is then deposited to prevent metal diffusion from the pressure-sensitive layer 3 and enhance metal adhesion. A metal layer is then sputter-deposited to form the pressure grid. The strained metal layer used for the pressure grid can be an Au thin film or other metals, such as nickel-chromium alloy or constantan.

[0055] Then, the middle insulating layer 24 is spin-coated to prepare the temperature sensitive layer 6. The metal of the temperature sensitive layer 6 can be Pt or other metals. The encapsulation layer 25 is spin-coated on the basis of the metal film of the temperature sensitive layer 6 to protect the device structure.

[0056] Then, photoresist is spin-coated, exposed, and developed for patterning. The photoresist serves as a mask layer for the subsequent etching process. Dry etching is performed to form electrode openings 2b. Metal electrodes, including pressure electrode 4 and temperature electrode 7, are prepared through electroplating. Then, photosensitive thick PI is spin-coated as a substrate for preparing the cavity 2a structure. The cavity 2a structure is prepared through photolithography, and the previously prepared electrodes are opened for subsequent device testing.

[0057] Since the entire device is a flexible substrate, the subsequent steps are simply to separate the device from the bare silicon die 8 of the wafer. This can be done in two ways. The first is to use the MEMS process. A thick photoresist is spin-coated on the entire wafer surface as a mask. The PI layer of the device is opened by dry etching, and all the individual devices on the wafer are flexibly transferred. The second method is the laser cutting process. By laser ablation of the PI film layer, the devices on the entire wafer are individually separated. Then, by lifting a part of the corner of the device, the complete device is separated from the wafer.

[0058] Finally, the flexible device is placed on the processing platform of a dispensing machine, and after presetting the parameters, a small amount of UV epoxy resin is applied to form bumps, creating a raised structure 5 that facilitates force transmission to the front end of the pressure-sensitive grid. To protect the electronic skin device, the PI device is combined with silicone. Silicone such as Ecoflex (aliphatic aromatic random copolyester) and PDMS is spin-coated on the surface of the device. Silicone with a specific modulus can be customized according to the application requirements to form the top silicone layer 26 for encapsulation.

[0059] The process of the above steps is as follows Figures 6 to 10 As shown, steps a to m are as follows: prepare a bare silicon wafer 8—spin-coat the base PI—grow silicon oxide—grow the pressure-sensitive layer 3—grow the insulating layer 24—grow the temperature-sensitive layer 6—encapsulation layer 25—etch the electrode—electroplate the metal electrode—apply photosensitive PI to open the cavity 2a—remove the bare silicon wafer 8—dispense glue to form the raised structure 5—encapsulate the electronic skin device and form the silicone layer 26.

[0060] In order to better understand the present invention, the following Figures 1 to 10 The technical solution of the present invention is described in detail: In this embodiment, the raised structure 5 is positioned above and at the center of cavity 2a, while the leading edge of the pressure grid lies within cavity 2a. As the external load increases, the pressure grid deforms, causing its impedance to change. This linear relationship between resistance and pressure is observed, allowing pressure to be monitored. The temperature-sensitive layer 6 is located below the pressure grid. This arrangement offers the advantage of being unaffected by pressure, resulting in the most accurate temperature measurement.

[0061] Thus, this case has the following advantages: (1) Dual-mode sensor: The temperature-sensitive layer and pressure-sensitive layer of the sensor can be prepared simultaneously through MEMS process technology, which greatly reduces the difficulty of the sensor preparation process and reduces the size of the sensor. The design of the multifunctional sensitive layer enables the sensor to not only monitor the changes in the load of the object, but also to identify the temperature changes of the external object. This greatly broadens the application scenarios of the sensor. (2) Cavity 2a structure design: The cavity 2a structure is made using MEMS technology, which greatly improves the sensitivity of the sensor, while reducing the size of the sensor, reducing the difficulty of flexible device preparation and saving process flow; and it can design as many microstructures as possible within a unit area, while combining the protruding structure 5 to reduce the cost of the flexible device.

[0062] The specific embodiments of the present invention described above do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A flexible tactile sensor, characterized in that: include: The flexible substrate has a cavity and a force-bearing end surface formed on its outer wall, wherein the force-bearing end surface is spaced apart from the cavity; a pressure-sensitive layer disposed inside the flexible substrate and between the cavity and the force-bearing end surface, and at least partially overlapping with a projection of the cavity on the force-bearing end surface, wherein the pressure-sensitive layer deforms when subjected to an external force and is used to convert pressure into an electrical signal; and The pressure electrode is provided on the flexible substrate and connected to the pressure sensitive layer.

2. The flexible tactile sensor according to claim 1, characterized in that The pressure-sensitive layer extends in a direction parallel to the force-bearing end surface, and the projection area of ​​the portion to which the cavity belongs on the force-bearing end surface is the first area; The flexible tactile sensor also includes a protruding structure, which is arranged in the flexible substrate and located on the side of the pressure-sensitive layer close to the force-bearing end surface, and the projection area on the force-bearing end surface is a second area, and the second area falls within the first area.

3. The flexible tactile sensor according to claim 2, characterized in that: The cavities are symmetrically arranged at both ends of the extension direction of the pressure sensitive layer; The geometric center of the protruding structure falls on the symmetry axis of the cavity.

4. The flexible tactile sensor according to claim 2, characterized in that: The protruding structure and the pressure-sensitive layer are spaced apart from each other along an extending direction of the pressure-sensitive layer.

5. The flexible tactile sensor according to claim 2, characterized in that: The protruding structure is arranged in a hemispherical shape and has an arc-shaped convex surface and a force transmission plane located on its surface. The arc-shaped convex surface is close to the force-bearing end surface, and the force transmission plane is close to the cavity.

6. The flexible tactile sensor according to claim 1, characterized in that: The flexible tactile sensor further includes a temperature sensitive layer and a temperature electrode. The temperature sensitive layer is disposed in the flexible substrate and is located on a side of the pressure sensitive layer away from the force-bearing end surface and is offset from a portion of the pressure sensitive layer exposed to the cavity. The temperature electrode is disposed in the flexible substrate and is partially located on an outer wall of the flexible substrate and is connected to the temperature sensitive layer. The temperature sensitive layer changes its resistance when the temperature changes.

7. The flexible tactile sensor according to claim 6, characterized in that: The cavity is open on one side away from the force-bearing end surface; One end of the temperature sensitive layer extends to a side wall where the cavity intersects the opening.

8. The flexible tactile sensor according to claim 7, characterized in that: The pressure sensitive layer comprises an expansion section and a main body section connected to each other, wherein the expansion section coincides with a projection of the cavity on the force-bearing end surface; The temperature sensitive layer, the temperature electrode, the pressure electrode and the main body segment are located on the same side of the cavity.

9. The flexible tactile sensor according to claim 6, characterized in that: The flexible substrate includes a polyimide layer, a silicon oxide layer, an insulating layer, and an encapsulation layer, wherein the polyimide layer, the silicon oxide layer, the pressure-sensitive layer, the insulating layer, the temperature-sensitive layer, and the encapsulation layer are stacked in sequence, and the pressure-sensitive layer is coated between the silicon oxide layer and the insulating layer, and the temperature-sensitive layer is coated between the insulating layer and the encapsulation layer; The cavity is formed between the encapsulation layer and the insulating layer.

10. A method for manufacturing a flexible tactile sensor, for manufacturing the flexible tactile sensor according to any one of claims 1 to 9, characterized in that: Including steps: preparing the flexible substrate without the cavity, and preparing the pressure-sensitive layer inside the flexible substrate during the preparation of the flexible substrate; Then, a photoresist is spin-coated on the surface of the flexible substrate, and a development and patterning process is performed. The photoresist coating is used as a mask layer for an electrode etching process, and dry etching is performed to form an electrode opening. The pressure electrode is prepared in the electrode opening by an electroplating process. Then, a photosensitive coating is spin-coated on the surface of the flexible substrate and used as a base for preparing the cavity. The cavity is prepared by a photolithography process, and the pressure electrode is opened.

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