A flexible tactile sensor and its application

Abstract

The present invention provides a flexible tactile sensor and its application. The flexible tactile sensor comprises a flexible magnetic film, an intermediate elastic body, a magnetic sensing unit and a flexible substrate arranged in sequence from top to bottom. The magnetic sensing unit has a sensitive axis, and the magnetization direction of the flexible magnetic film is adjustable. The flexible tactile sensor of the present invention has a simple structure and is easy to industrialize. The sensor is a fully flexible design as a whole. Compared with traditional devices with rigid substrates, it has a wider range of applications and can be prepared on a large area. The magnetic sensing unit has a sensitive axis, can perform multi-degree-of-freedom detection, has high sensitivity, fast response, and good temperature resistance.

Description

Technical Field

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

[0002] A tactile sensor is a sensor that imitates the sense of touch. With the rapid development of artificial intelligence technology, higher requirements are placed on tactile sensors in the fields of intelligent robots, consumer electronics, smart medical care, health monitoring equipment, etc.

[0003] The most widely used tactile sensor on the market is the piezoresistive tactile sensor, whose sensitive element is the resistive strain material. The test principle is: the resistance of the resistive strain material is related to the material type, cross-sectional area A, and length L, that is, The material deforms when subjected to force, resulting in a change in resistance. However, piezoresistive tactile sensors have many defects during use, such as low sensitivity, slow response time, severe mechanical hysteresis, and only single-degree-of-freedom detection, which cannot meet the various needs in the field of artificial intelligence. Chinese invention patent CN113607307A discloses a capacitive tactile sensor with a special structure. The sensor can achieve high sensitivity and multi-degree-of-freedom detection, but the sensor still has many problems, such as its structural design is too complicated and cannot be flexible.

[0004] In summary, existing tactile sensors can no longer meet the needs of the field of artificial intelligence, and there is an urgent need for a tactile sensor that can be used in the fields of intelligent robots, smart medical care, etc. Summary of the invention

[0005] In order to overcome the above-mentioned deficiencies of the prior art, an object of the present invention is to provide a tactile sensor that can achieve high sensitivity, fast response, multi-degree-of-freedom detection and flexible design.

[0006] The present invention provides a flexible tactile sensor, comprising a flexible magnetic film, an intermediate elastic body, a magnetic sensing unit and a flexible substrate which are arranged in sequence from top to bottom. The magnetic sensing unit has a sensitive axis, and the magnetization direction of the flexible magnetic film is adjustable.

[0007] The flexible tactile sensor of the present invention has a simple structure and is easy to industrialize. The sensor is a fully flexible design as a whole. Compared with traditional devices with rigid substrates, it has a wider range of applications and can be prepared on a large area. The magnetic sensing unit has a sensitive axis and can perform multi-degree-of-freedom detection. It has high sensitivity, fast response, and good temperature resistance.

[0008] Preferably, the magnetization direction of the flexible magnetic film is parallel to the sensitive axis direction of the magnetic sensing unit.

[0009] Preferably, the magnetic sensing unit and the flexible magnetic film are arranged in an array, and the flexible tactile sensor has a plurality of array units.

[0010] Preferably, in each of the array units, the sensitive axis direction of the magnetic sensing unit and the magnetization direction of the flexible magnetic film are independently designed. The magnetic sensing unit and the flexible magnetic film can be designed in an array to obtain better performance.

[0011] Preferably, the flexible substrate is a flexible film, and the material of the flexible substrate is selected from one or more of the following: PI, PET, PEN, PMMA and Kapton. The flexible substrate is in a film state, can be bent and deformed, and has a wide range of applications.

[0012] Preferably, the magnetic sensing unit comprises a sensitive element, and the sensitive element is selected from the following: a spin valve element, a Hall sensing element, a spin Hall magnetoresistive element, a giant magnetoresistive element, and an anisotropic magnetoresistive element. The magnetic sensing unit has a sensitive axis and can perform multi-degree-of-freedom detection. The sensitive element has high sensitivity and fast response.

[0013] Preferably, the material of the intermediate elastomer is selected from one or more of the following: silicone rubber, block copolymer and hydrogel. The intermediate elastomer has a low elastic modulus and will undergo a large deformation when subjected to a small force, and can be bent, compressed, stretched and other deformations, which is conducive to the sensor to achieve high sensitivity and rapid response.

[0014] Preferably, the flexible magnetic film is made of a mixture of magnetic material and polymer material. The flexible magnetic film is a permanent magnet, and its magnetization direction can be designed according to the sensitive element of the magnetic sensing unit. The magnetic sensing unit can obtain the magnetic field change of the flexible magnetic film in the three-dimensional direction, thereby measuring and detecting compressive stress and shear force.

[0015] Preferably, the magnetic material is selected from one or more of the following: neodymium iron boron, magnetic metal or alloy, magnetic oxide and magnetic nitride, and the polymer material is selected from one or more of the following: foam, silicone rubber, block copolymer and hydrogel. The flexible magnetic film is a mixture of magnetic material and polymer material, and its magnetization direction is adjustable.

[0016] Another aspect of the present invention provides an application of the above-mentioned flexible tactile sensor, wherein the flexible tactile sensor is applied to detection of multiple tactile sensing modes, high-precision tactile detection or high-spatial-resolution tactile detection.

[0017] The flexible tactile sensor of the present invention can realize multiple tactile modes such as pressing and friction, and has the performance of ultra-sensitivity, ultra-spatial resolution, rapid response, etc. It is flexible as a whole and can be attached to the surface of irregularly shaped objects, meeting the use requirements in the fields of intelligent robots, consumer electronics, smart medical care, health monitoring equipment, etc.

[0018] In summary, the present invention provides a flexible tactile sensor and its application. The flexible tactile sensor has a multilayer structure of a flexible magnetic film, an intermediate elastic body, a magnetic sensing unit and a flexible substrate. Compared with the prior art, it has the following beneficial effects:

[0019] (1) The magnetic sensing unit has a sensitive axis, high sensitivity, fast response, good temperature resistance, and can perform multi-degree-of-freedom detection;

[0020] (2) The flexible tactile sensor is a fully flexible design. Compared with traditional devices with rigid substrates, it has a wider range of applications and can be prepared on a large area.

[0021] (3) The magnetic sensing unit can be miniaturized to improve the integration density;

[0022] (4) The flexible tactile sensor has a simple device structure and is easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the structure of a flexible tactile sensor in an embodiment of the present invention;

[0024] Figure 2 Schematic diagram of the magnetic field of the flexible magnetic film of the flexible tactile sensor in an embodiment of the present invention;

[0025] Figure 3 It is a schematic structural diagram of a flexible tactile sensor in another embodiment of the present invention;

[0026] Figure 4 is a distribution diagram of magnetic induction intensity along the z-axis direction when x=y=0 in the area below the flexible magnetic film in Example 1;

[0027] Figure 5 is a distribution diagram of magnetic induction intensity along the x-axis and y-axis directions when z=2.5 mm in the area below the flexible magnetic film in Example 1;

[0028] Figure 6 is the magnetoresistance curve of the magnetic sensing unit in Example 1;

[0029] Figure 7 The output resistance of the flexible tactile sensor of Example 1 and the magnetoresistance curve of the displacement of the flexible magnetic film along the z-axis direction;

[0030] Figure 8 The output resistance of the flexible tactile sensor of Example 1 and the magnetoresistance curve of the flexible magnetic film displacement along the x-axis direction.

[0031] Description of reference numerals:

[0032] 1-flexible magnetic film, 2-intermediate elastic body, 3-magnetic sensing unit, 4-flexible substrate, 5-sensitive axis direction of the magnetic sensing unit, 6-magnetization direction of the flexible magnetic film, 7-coordinate axis direction. DETAILED DESCRIPTION

[0033] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. It should be noted that the following embodiments are only used to illustrate the implementation method and typical parameters of the present invention, and are not used to limit the parameter range described in the present invention. Reasonable changes derived therefrom are still within the scope of protection of the claims of the present invention.

[0034] It should be noted that the endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this article.

[0035] Combination Figure 1 and Figure 2 As shown, an embodiment of the present invention provides a flexible tactile sensor, including a flexible magnetic film 1, an intermediate elastomer 2, a magnetic sensing unit 3 and a flexible substrate 4, the magnetic sensing unit 3 is arranged on the upper surface of the flexible substrate 4, the intermediate elastomer 2 covers the upper surface of the magnetic sensing unit 3, and the flexible magnetic film 1 is arranged on the upper surface of the intermediate elastomer 2, located at the top layer.

[0036] The flexible magnetic film 1 is made of a mixture of magnetic material and polymer material. The flexible magnetic film 1 is a permanent magnet, and its magnetization direction can be designed according to the sensitive element of the magnetic sensing unit 3. The intermediate elastomer 2 is made of various flexible polymer materials with a low elastic modulus. When subjected to a small force, it will undergo a large deformation and can be bent, compressed, stretched, etc. The magnetic sensing unit 3 has a sensitive axis, and the direction of the sensitive axis is defined as the x-axis. The geometric center of the magnetic sensing unit 3 is taken as the origin, and the y-axis and z-axis are defined respectively, such as Figure 2 The magnetization direction of the flexible magnetic film 1 is adjustable. In this embodiment, the magnetization direction of the flexible magnetic film 1 is parallel to the direction of the sensitive axis of the magnetic sensing unit 3. The flexible substrate 4 is in a thin film state and can be bent and deformed. The material of the flexible substrate 4 is various types of flexible high molecular polymer materials.

[0037] The working principle of the flexible tactile sensor is as follows: the upper surface of the flexible magnetic film 1 of the flexible tactile sensor is subjected to the normal force (shear force) to be measured, and the pressure causes the deformation of the intermediate elastic body 2, thereby causing the flexible magnetic film 1 to be displaced along the z-axis (x-axis or y-axis), thereby affecting the distribution of the magnetic field of the flexible magnetic film 1 along the z-axis (x-axis or y-axis). Since the distribution of the magnetic field along the z-axis (x-axis or y-axis) changes, and the change in magnetic induction intensity is a functional relationship with the displacement of the flexible magnetic film 1 along the z-axis (x-axis or y-axis), the output signal of the magnetic sensing unit 3 is also a functional relationship with the change of the magnetic field. At the same time, the pressure is also a functional relationship with the deformation of the intermediate elastic body 2 in the z-axis (x-axis or y-axis). Therefore, by receiving the output signal of the tactile sensor, the change in the magnetic field can be calculated, and then the magnitude of the pressure to be measured can be obtained.

[0038] The flexible tactile sensor has a simple structure and is easy to industrialize. The sensor is a fully flexible design as a whole. Compared with traditional devices with rigid substrates, it has a wider range of applications and can be prepared on a large area. The magnetic sensing unit 3 has a sensitive axis and can perform multi-degree-of-freedom detection. It has high sensitivity, fast response, and good temperature resistance, and can meet the use requirements of intelligent robots, consumer electronics, smart medical care, health monitoring equipment and other fields.

[0039] Combination Figure 3 As shown, another embodiment of the present invention provides another flexible tactile sensor, including a flexible magnetic film 1, an intermediate elastic body 2, a magnetic sensing unit 3 and a flexible substrate 4 arranged in sequence from top to bottom, wherein the magnetic sensing unit 3 and the flexible magnetic film 1 are arranged in an array, and the flexible tactile sensor has a plurality of array units. The sensitive axis direction of the magnetic sensing unit 3 and the magnetization direction of the flexible magnetic film 1 are independently designed, so as to obtain better functions, such as detection of multiple tactile sensing modes, high-precision tactile detection, high spatial resolution tactile detection, etc.

[0040] In a specific embodiment of the present invention, the magnetic material of the flexible magnetic film 1 is selected from one or more of the following: neodymium iron boron, magnetic metal or alloy, magnetic oxide and magnetic nitride; the polymer material of the flexible magnetic film 1 is selected from one or more of the following: foam, silicone rubber, block copolymer and hydrogel.

[0041] In a specific embodiment of the present invention, the material of the intermediate elastomer 2 is selected from one or more of the following: foam, silicone rubber, block copolymer and hydrogel.

[0042] In a specific embodiment of the present invention, the magnetic sensing unit 3 includes a sensitive element, and the sensitive element is selected from the following: a spin valve element, a Hall sensor element, a spin Hall magnetoresistive element, a giant magnetoresistive element, and an anisotropic magnetoresistive element.

[0043] In a specific embodiment of the present invention, the material of the flexible substrate 4 is selected from one or more of the following: PI, PET, PEN, PMMA and Kapton.

[0044] The present invention is described in detail below through specific embodiments.

[0045] Example 1

[0046] The flexible tactile sensor of this embodiment includes a flexible magnetic film 1, an intermediate elastic body 2, a magnetic sensing unit 3 and a flexible substrate 4 arranged in order from top to bottom. The flexible magnetic film 1 is made of a mixture of magnetic material and polymer material. The magnetic material is neodymium iron boron powder, and the polymer material is PDMS. The magnetic induction intensity of the flexible magnetic film 1 is as follows: Figure 4 and Figure 5 As shown; the material of the middle elastomer layer 2 is Ecoflex; the sensitive element of the magnetic sensing unit 3 is a spin valve element; the material of the flexible substrate 4 is polyimide.

[0047] The magnetic sensing unit 3 of the flexible tactile sensor uses a spin valve element with high sensitivity and precision as a sensitive element. The magnetoresistance curve is as follows: Figure 6 When an external magnetic field H parallel to the sensitive axis direction is applied to the spin valve element, within a specific range of the external magnetic field H, the resistance value R of the spin valve element changes with the change of the external magnetic field H. When the applied external field is greater than the absolute value of its saturation field, its resistance value no longer changes, that is, the sensitive element reaches saturation.

[0048] The upper surface of the flexible magnetic film 11 of the flexible tactile sensor is subjected to the normal force to be measured. The normal force causes the deformation of the intermediate elastic body 2, thereby causing the displacement of the flexible magnetic film 1 along the z-axis direction, thereby affecting the distribution of the magnetic field of the flexible magnetic film 1 along the z-axis direction. At this time, the magnetic flux density felt by the magnetic sensor element changes, thereby causing the resistance of the spin valve element to change. Figure 5 ,It can be seen from the figure that when the flexible magnetic film 1 moves close to the origin in the positive direction of the z-axis, the output resistance increases.

[0049] The upper surface of the flexible magnetic film 1 of the flexible tactile sensor is subjected to the shear force to be measured along the x-axis (or y-axis). The shear force causes the deformation of the intermediate elastic body 2, thereby causing the displacement of the flexible magnetic film 1 along the x-axis (or y-axis), thereby affecting the distribution of the magnetic field of the flexible magnetic film 1 along the x-axis (or y-axis). At this time, the magnetic flux density felt by the magnetic sensor element changes, thereby causing the resistance of the spin valve element to change. Figure 6 As can be seen from the figure, when the flexible magnetic film 11 moves away from the origin along the x-axis, the output resistance decreases.

[0050] It can be seen that the flexible tactile sensor can detect compressive stress and shear force, and can achieve high sensitivity, fast response and multi-degree-of-freedom detection.

[0051] Example 2

[0052] The flexible tactile sensor of this embodiment includes a flexible magnetic film 1, an intermediate elastic body 2, a magnetic sensing unit 3 and a flexible substrate 4, which are arranged in order from top to bottom. The flexible magnetic film 1 is made of a mixture of magnetic material and polymer material, wherein the magnetic material is ferroferric oxide powder and the polymer material is silicone rubber; the material of the intermediate elastic body 2 layer is PDMS; the sensitive element of the magnetic sensing unit 3 is a Hall sensor element; and the material of the flexible substrate 4 is PET.

[0053] Example 3

[0054] The flexible tactile sensor of this embodiment includes a flexible magnetic film 1, an intermediate elastic body 2, a magnetic sensing unit 3 and a flexible substrate 4, which are arranged in order from top to bottom. The flexible magnetic film 1 is made of a mixture of magnetic material and polymer material, the magnetic material is nickel powder, and the polymer material is hydrogel; the material of the intermediate elastic body 2 layer is silicone rubber; the sensitive element of the magnetic sensing unit 3 is a giant magnetoresistance element; and the material of the flexible substrate 4 is PEN.

[0055] Example 4

[0056] The flexible tactile sensor of this embodiment includes a flexible magnetic film 1, an intermediate elastic body 2, a magnetic sensing unit 3 and a flexible substrate 4, which are arranged in order from top to bottom. The flexible magnetic film 1 is made of a mixture of magnetic material and polymer material, wherein the magnetic material is cobalt powder and the polymer material is PET; the material of the intermediate elastic body 2 layer is SEBS; the sensitive element of the magnetic sensing unit 3 is an anisotropic magnetoresistance element; and the material of the flexible substrate 4 is PMMA.

[0057] Example 5

[0058] The flexible tactile sensor of this embodiment includes a flexible magnetic film 1, an intermediate elastic body 2, a magnetic sensing unit 3 and a flexible substrate 4, which are arranged in order from top to bottom. The flexible magnetic film 1 is made of a mixture of magnetic material and polymer material, the magnetic material is iron powder, and the polymer material is foam; the material of the intermediate elastic body 2 layer is PDMS; the sensitive element of the magnetic sensing unit 3 is a spin Hall magnetoresistive element; and the material of the flexible substrate 4 is Kapton.

[0059] Example 6

[0060] The flexible tactile sensor of this embodiment includes a flexible magnetic film 1, an intermediate elastic body 2, a magnetic sensing unit 3 and a flexible substrate 4 arranged in sequence from top to bottom. The magnetic sensing unit 3 and the flexible magnetic film 1 are arranged in an array, and the flexible tactile sensor has a plurality of array units. The sensitive axis direction of the magnetic sensing unit 3 in each array unit is parallel to the magnetization direction of the flexible magnetic film 1, and the sensitive axis directions of the magnetic sensing units 3 in each array unit are different. The flexible magnetic film 1 is made of a mixture of magnetic material and polymer material, the magnetic material is neodymium iron boron powder, and the polymer material is PDMS; the material of the intermediate elastic body 2 layer is foam; the sensitive element of the magnetic sensing unit 3 is a spin valve element; the material of the flexible substrate 4 is PI.

[0061] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A flexible tactile sensor, characterized in that: The flexible tactile sensor comprises a flexible magnetic film (1), an intermediate elastic body (2), a magnetic sensing unit (3) and a flexible substrate (4) which are arranged in sequence from top to bottom. The magnetic sensing unit (3) has a sensitive axis. The magnetization direction of the flexible magnetic film (1) is adjustable. The flexible magnetic film (1) is made of a mixture of magnetic material and polymer material. The magnetic material is selected from one or more of the following: magnetic metal or alloy, magnetic oxide and magnetic nitride. The polymer material is selected from one or more of the following: foam, silicone rubber, block copolymer and hydrogel. The magnetic sensing unit (3) and the flexible magnetic film (1) are arranged in an array. The flexible tactile sensor comprises a plurality of array units. In each of the array units, the sensitive axis direction of the magnetic sensing unit (3) and the magnetization direction of the flexible magnetic film (1) are independently designed.

2. The flexible tactile sensor according to claim 1, characterized in that: The flexible substrate (4) is a flexible film, and the material of the flexible substrate (4) is selected from one or more of the following: PI, PET, PEN, PMMA and Kapton.

3. The flexible tactile sensor according to claim 1, characterized in that: The magnetic sensing unit (3) comprises a sensitive element, and the sensitive element is selected from the following: a spin valve element, a Hall sensing element, a spin Hall magnetoresistance element, a giant magnetoresistance element and an anisotropic magnetoresistance element.

4. The flexible tactile sensor according to claim 1, characterized in that: The material of the intermediate elastomer (2) is selected from one or more of the following: foam, silicone rubber, block copolymer and hydrogel.

5. An application of the flexible tactile sensor according to any one of claims 1 to 4, characterized in that: The flexible tactile sensor can be applied to detection of multiple tactile sensing modes, high-precision tactile detection or high-spatial-resolution tactile detection.

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