A combined piezoresistive flexible three-dimensional force sensor and preparation method thereof

Abstract

A combined piezoresistive flexible three-dimensional force sensor and a preparation method, relating to the field of sensor technology. The problem that the existing sensors cannot achieve long-term detection, have low sensitivity, poor stability, cannot achieve direction recognition, and the shear force and pressure interfere with each other is solved. The present invention includes a pressure sensing unit, a support unit, a shear force sensing unit and a force collection unit; the pressure sensing unit includes a third flexible substrate layer, a composite sensitive material layer and a fourth flexible substrate layer, the support unit includes an outer frame, a central pillar, the outer frame includes a side wall support frame and a bracket, the shear force sensing unit includes a first flexible substrate layer, a cross-shaped sensitive material layer and a second flexible substrate layer, and the force collection unit includes a contact; the pressure sensing unit, the support unit, the shear force sensing unit and the force collection unit are stacked together from bottom to top, and the central pillar of the support unit is coaxial with the force collection unit. The present invention is applicable to the field of tactile sensors for collecting three-dimensional force signals.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, in particular to the field of tactile sensor technology. Background Art

[0002] With the rapid development of intelligent robots and unmanned equipment, tactile perception, as a prerequisite for their realization of intelligence, has become a frontier field that researchers from all over the world are competing to study. Flexible three-dimensional force sensors, as an indispensable means for robots to realize bionic perception, have also received great attention. Three-dimensional force sensors can detect external forces and feed back the information obtained to the computer system. Through analysis and processing, external parameters such as the weight of the material, the shape, material, and motion state of the surface are evaluated, thereby guiding the intelligent device to respond accordingly to external stimuli. Therefore, the study of high-precision, stable, flexible three-dimensional force sensors with certain tensile properties can greatly improve the intelligence of intelligent devices and broaden the application scenarios of intelligent devices.

[0003] Invention patent document publication number: CN 205449351 U discloses a small three-dimensional force sensor, which consists of an elastomeric shell and a strain sensitive unit. The sensitive unit is located on the elastomeric wall and can monitor the direction and magnitude of the shear force and the magnitude of the normal force, but does not have good tensile properties and the preparation method is relatively complicated.

[0004] Invention patent document publication number: CN 1796955 A discloses a flexible tactile sensor, the flexible filling material, elastic substrate and elastic protective layer of which are made of resin material to achieve flexibility requirements, but its sensitivity is low and cannot adapt to working scenarios with high precision requirements.

[0005] Invention patent document publication number: CN 103743503 A discloses a flexible three-dimensional force tactile sensor based on a combination of piezoresistive and capacitive types. The sensor uses a capacitive sensor to monitor horizontal tangential force and a piezoresistive sensor to detect normal force, separating the monitoring of normal force and horizontal tangential force, thereby achieving simultaneous detection of three-dimensional force. However, the sensor is structurally unable to identify the direction of horizontal tangential force, and the capacitive sensor cannot achieve long-term uninterrupted pressure monitoring.

[0006] Invention patent document publication number: CN 108362410 A discloses a three-dimensional force flexible sensor, which, when subjected to force, is transmitted to the pressure-sensitive unit through four support columns. The direction of the force acting on the pressure-sensitive unit is in the inclined direction, and only the positive pressure causes the change in the resistance of the pressure-sensitive unit. The changed resistance is obtained by scanning, and then the magnitude and direction of the three-dimensional force acting on the flexible sensor unit can be obtained based on theoretical deduction. This method realizes three-dimensional force perception to a certain extent, but because its horizontal tangential force is derived, its accuracy cannot be guaranteed.

[0007] In the development process of flexible tactile sensors, pressure-variable resistor technology, pressure-variable capacitor technology, friction electrification technology, pressure-variable voltage technology and optical-based tactile sensing technology are commonly used to prepare flexible tactile sensors. Among them, pressure-variable capacitor technology and optical-based tactile sensing technology both require more complex signal detection equipment, and their application will be subject to certain restrictions. The main disadvantage of friction electrification technology and pressure-variable voltage technology is that they can only sense the moment of contact with the object, but cannot sense the pressure of the object's long-term contact state. In comparison, the tactile sensing technology based on the principle of pressure-variable resistor does not require complex detection equipment, and can always maintain the state of sensing the contact of the object. The three-dimensional force sensors that have been publicly reported in the world are often designed with a single pressure-variable capacitor technology or a pressure-variable resistor technology to design a tactile sensor with a multi-layer composite structure. Although they have achieved simultaneous perception of shear force and pressure to a certain extent, most of them have defects such as inability to achieve long-term detection, low sensitivity, susceptibility to external interference, low stability, poor stretchability, and inability to achieve direction recognition. In addition, the multi-layer composite structure will cause mutual interference when sensing shear force and pressure at the same time. Summary of the invention

[0008] The present invention provides a combined piezoresistive flexible three-dimensional force sensor, which solves the problems that the existing sensors cannot realize long-term detection, have low sensitivity, poor stability, cannot realize direction recognition, and cause mutual interference between shear force and pressure perception.

[0009] To achieve the above object, the present invention provides the following solutions:

[0010] A combined piezoresistive flexible three-dimensional force sensor, the sensor comprising a pressure sensing unit, a support unit, a shear force sensing unit and a force acquisition unit;

[0011] The pressure sensing unit comprises a third flexible substrate layer, a composite sensitive material layer and a fourth flexible substrate layer, wherein the composite sensitive material layer is arranged between the third flexible substrate layer and the fourth flexible substrate layer, and the third flexible substrate layer, the composite sensitive material layer and the fourth flexible substrate layer are bonded together;

[0012] The support unit includes an outer frame and a central pillar. The outer frame includes a side wall support frame and a bracket. The side wall support frame is cylindrical. The central pillar is fixed at the center of the outer frame. The bracket is located inside the side wall support frame. One end of the bracket is fixedly connected to the inner wall of the side wall support frame, and the other end is fixedly connected to the outer wall of the central pillar. The bracket is in the shape of a cross structure and is made of elastic material.

[0013] The shear force sensing unit comprises a first flexible base layer, a cross-shaped sensitive material layer and a second flexible base layer, wherein the cross-shaped sensitive material layer is arranged between the first flexible base layer and the second flexible base layer, and the first flexible base layer, the cross-shaped sensitive material layer and the second flexible base layer are bonded together;

[0014] The force collection unit comprises a contact, the top of the contact is arc-shaped and the bottom is flat;

[0015] The pressure sensing unit, the support unit, the shear force sensing unit and the force collection unit are stacked together in sequence from bottom to top, and the central pillar of the support unit is coaxial with the force collection unit.

[0016] Furthermore, there is a preferred embodiment in which the force collection unit further includes a protective shell, an opening is provided in the middle of the top of the protective shell, the protective shell covers the contact and the upper part of the shear force sensing unit, and the top of the contact extends to the outside of the top opening of the protective shell.

[0017] Furthermore, in a preferred embodiment, the contact is in a hemispherical shape, and the radius of the bottom circle of the hemispherical shape is between 1.5 and 3 mm.

[0018] Furthermore, in a preferred embodiment, the height of the central pillar is 3 to 10 mm, the shape of the central pillar is a frustum, and the ratio of the radius of the upper end circle to the radius of the lower end circle of the frustum is within 1 to 0.375.

[0019] Furthermore, in a preferred embodiment, the side wall support frame is cylindrical in shape, the height of the side wall support frame is the same as that of the central support, and the wall thickness is 1 to 3 mm.

[0020] Furthermore, in a preferred embodiment, electrodes are respectively disposed at the four tail ends of the cross-shaped sensitive material layer, and a common electrode is disposed at the exact center of the cross-shaped sensitive material layer.

[0021] Furthermore, in a preferred embodiment, the thickness of the cross-shaped sensitive material layer is 80-100 nm.

[0022] Furthermore, in a preferred embodiment, the composite sensitive material layer is in the shape of a quadrilateral, and an electrode is respectively provided near opposite sides of the quadrilateral, and each electrode is connected to an electrode lead wire.

[0023] Furthermore, in a preferred embodiment, the thickness of the composite sensitive material layer is 100-180 nm.

[0024] A method for preparing a combined piezoresistive flexible three-dimensional force sensor, wherein the three-dimensional force sensor is any one of the three-dimensional sensors described above, and the steps of the method are:

[0025] S1, a step of preparing a flexible substrate layer, spin coating a high molecular polymer on a substrate, and removing the polymer from the substrate after curing to obtain a flexible substrate, preparing a total of four flexible substrates, the flexible substrates being a first flexible substrate layer, a second flexible substrate layer, a third flexible substrate layer, and a fourth flexible substrate layer;

[0026] S2, a cross-shaped sensitive material layer manufacturing step, attaching a metal mask to the second flexible substrate layer, placing the metal mask in a vapor deposition machine for gold plating, and completing the manufacturing of the cross-shaped sensitive material layer;

[0027] S3, the steps of making the composite sensitive material layer, mixing carbon nanotubes into deionized water, using an ultrasonic disperser to evenly disperse the carbon nanotubes in the solution, and letting it stand, after the surface of the fourth flexible substrate layer is treated with oxygen plasma, taking an appropriate amount of the supernatant of the carbon nanotube solution and applying it to the position treated with oxygen plasma, and after it is naturally extended and the water evaporates to form a carbon nanotube film, it is placed in a vapor deposition machine for gold plating to complete the production of the composite sensitive material layer;

[0028] S4. Cover the third flexible substrate layer on the composite sensitive material layer, and bond it to the composite sensitive material layer and the fourth flexible substrate layer below it; bond and fix the outer frame and the central pillar on the upper surface of the third flexible substrate layer; bond the bottom surface of the second flexible substrate layer to the top of the outer frame and the top of the central pillar; cover the cross-shaped sensitive material layer, and bond it to the cross-shaped sensitive material layer and the second flexible substrate layer; bond the protective shell and contacts to the upper surface of the first flexible substrate layer to obtain a single sensor.

[0029] Technical Effects

[0030] The present invention provides a combined piezoresistive flexible three-dimensional force sensor to solve the problems that existing sensors cannot achieve long-term detection, have low sensitivity, poor stability, cannot achieve direction recognition, and mutual interference between shear force and pressure perception. At the same time, a preparation method of the combined piezoresistive flexible three-dimensional force sensor is obtained.

[0031] Compared with the existing technology, the following advantages are produced:

[0032] 1. Existing sensors: A three-dimensional force flexible sensor, the perception of shear force is obtained by theoretical deduction of the positive pressure obtained by the pressure sensing structure in each direction, and is not directly perceived. The theoretical derivation method is complicated, the accuracy is low, and errors are prone to occur. The support column structure is a rigid structure with poor tensile performance and flexibility. In addition, adding a collection structure for detecting shear force on the basis of the existing sensor structure will affect the collection accuracy of other forces, thereby reducing the collection accuracy of the entire sensor. The combined piezoresistive flexible three-dimensional force sensor provided by the present invention uses a cross-shaped sensitive layer to sense the size and direction of external shear force. It does not require theoretical deduction, but is directly perceived. At the same time, the material of the central pillar is a high molecular elastomeric polymer, which has good flexibility and can be well covered on the surface of the device. It also minimizes the impact on the pressure collection structure, ensuring the accuracy of pressure and shear force collection. Compared with existing sensors, it has significant progress.

[0033] 2. The present invention provides a combined piezoresistive flexible three-dimensional force sensor, which senses the size and direction of external shear force through a cross-shaped sensitive layer, and senses the size of external pressure through a composite sensitive layer, thereby realizing simultaneous perception of external shear force and pressure. However, if the cross-shaped sensitive layer and the composite sensitive layer are simply used in combination, the pressure sensing force and the shear force will interfere with each other, and the accurate perception of the two forces cannot be achieved. At the same time, the perception of the direction of the shear force is more difficult. At the same time, the flexibility of the device will be sacrificed in the direct combination state, and the device cannot be well covered on the surface of the equipment. While the present invention uses the cross-shaped sensitive layer and the composite sensitive layer in combination, it also adopts a composite structure, utilizes the structural characteristics of the contact and the central pillar, transmits the shear force and pressure to their respective sensitive units, separates the shear force and pressure perception, thereby eliminating the influence of mutual interference between the two forces during the detection process, and the contact and central pillar of the high molecular elastomer polymer ensure the good flexibility of the device.

[0034] 3. The present invention provides a combined piezoresistive flexible three-dimensional force sensor, which utilizes a flexible structure and piezoresistive resistance technology to improve the stability of the sensor.

[0035] 4. The present invention provides a combined piezoresistive flexible three-dimensional force sensor, in which the protective shell and outer frame structure of the sensor are located at the outermost part of the sensor, which can reduce the damage to the internal structure caused by external impact and play a role in protecting the internal circuits and sensitive units.

[0036] 5. With respect to the combined piezoresistive flexible three-dimensional force sensor described in the present invention, the present invention provides a preparation method thereof, in which flexible materials are used to make various parts of the sensor, so that the sensor has good tensile properties and a small geometric volume, and can be covered on a large area on the surface of a smart device, providing it with tactile perception function and enhancing its ability to recognize the external environment.

[0037] 6. In the preparation method described in the present invention, nanogold film is used as the shear force sensing sensitive material, and the composite structure of nanogold film and carbon nanotube film is used as the pressure sensing sensitive material, so that the sensor has high sensitivity and realizes long-term continuous detection.

[0038] 7. The present invention provides a combined piezoresistive flexible three-dimensional force sensor, which has a simple structure. The outer frame, protective shell and contacts can be made by molds. The sensitive material layer and the flexible substrate are made by spin coating, drop coating and evaporation. The sensor parts are easy to assemble and the manufacturing process is simple.

[0039] The present invention is applicable to the technical field of tactile sensors and is used for collecting three-dimensional force signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic diagram of the cross-sectional structure of a combined piezoresistive flexible three-dimensional force sensor described in embodiments one to six.

[0041] Figure 2 This is a top view of the shear force sensing unit structure of a combined piezoresistive flexible three-dimensional force sensor described in embodiment seven.

[0042] Figure 3 It is an exploded stereoscopic diagram of a shear force sensing unit of a combined piezoresistive flexible three-dimensional force sensor described in embodiment seven.

[0043] Figure 4 This is an equivalent circuit diagram of a shear force sensing unit of a combined piezoresistive flexible three-dimensional force sensor described in implementation mode seven.

[0044] Figure 5 It is a top view of the pressure sensing unit mechanism of a combined piezoresistive flexible three-dimensional force sensor described in embodiment eight.

[0045] Figure 6 This is an image of the test results of a combined piezoresistive flexible three-dimensional force sensor described in embodiment eleven.

[0046] Figure 7 This is an image of the test results of a combined piezoresistive flexible three-dimensional force sensor described in embodiment eleven.

[0047] Figure 8This is an image of the test results of a combined piezoresistive flexible three-dimensional force sensor described in embodiment eleven.

[0048] Among them: 1 is a protective shell, 2 is a contact, 3 is a first flexible substrate layer, 4 is a cross-shaped sensitive material layer, 5 is a second flexible substrate layer, 6 is an outer frame, 7 is a bracket, 8 is a central pillar, 9 is a third flexible substrate layer, 10 is a composite sensitive material layer, 11 is a fourth flexible substrate layer, 12 is an electrode, and 13 is a common electrode. DETAILED DESCRIPTION

[0049] Implementation method 1. See Figure 1 This embodiment is described as a combined piezoresistive flexible three-dimensional force sensor, wherein the sensor includes a pressure sensing unit, a support unit, a shear force sensing unit and a force acquisition unit;

[0050] The pressure sensing unit comprises a third flexible base layer 9, a composite sensitive material layer 10 and a fourth flexible base layer 11, wherein the composite sensitive material layer 10 is arranged between the third flexible base layer 9 and the fourth flexible base layer 11, and the third flexible base layer 9, the composite sensitive material layer 10 and the fourth flexible base layer 11 are bonded together;

[0051] The support unit includes an outer frame and a central pillar 8. The outer frame includes a side wall support frame 6 and a bracket 7. The side wall support frame 6 is cylindrical. The central pillar 8 is fixed at the center of the outer frame. The bracket is located inside the side wall support frame 6, and one end of the bracket is fixedly connected to the inner wall of the side wall support frame 6, and the other end is fixedly connected to the outer wall of the central pillar 8. The bracket 7 is in a cross-shaped structure and is made of elastic material.

[0052] The shear force sensing unit comprises a first flexible base layer 3, a cross-shaped sensitive material layer 4 and a second flexible base layer 5, wherein the cross-shaped sensitive material layer 4 is arranged between the first flexible base layer 3 and the second flexible base layer 5, and the first flexible base layer 3, the cross-shaped sensitive material layer 4 and the second flexible base layer 5 are bonded together;

[0053] The force collection unit comprises a contact 2, the top of which is arc-shaped and the bottom is flat;

[0054] The pressure sensing unit, the support unit, the shear force sensing unit and the force collection unit are stacked together in sequence from bottom to top, and the central pillar of the support unit is coaxial with the force collection unit.

[0055] In actual application of this embodiment, the shape of the bracket 7 is a cross structure or a cross-shaped structure, and the bracket 7 and the outer wall of the central pillar 8 are fixed by bonding or using a mold to make the bracket 7 and the central pillar 8 as a whole. The choice can be flexibly made according to the actual work requirements on site.

[0056] Existing sensors: A three-dimensional force flexible sensor, the perception of shear force is obtained by theoretical deduction of the positive pressure obtained by the pressure sensing structure in each direction, and is not directly perceived. The theoretical derivation method is complicated, the accuracy is low, and errors are prone to occur. The support column structure is a rigid structure with poor tensile performance and flexibility. In addition, adding a collection structure for detecting shear force on the basis of the existing sensor structure will affect the collection accuracy of other forces, thereby reducing the collection accuracy of the entire sensor. The combined piezoresistive flexible three-dimensional force sensor provided in this embodiment uses a cross-shaped sensitive layer to sense the size and direction of external shear force. It does not require theoretical deduction, but is directly perceived. At the same time, the material of the central pillar is a high molecular elastomeric polymer, which has good flexibility and can be well covered on the surface of the device. It also minimizes the impact on the pressure collection structure, ensuring the accuracy of pressure and shear force collection. Compared with existing sensors, it has significant progress.

[0057] This embodiment provides a combined piezoresistive flexible three-dimensional force sensor, which senses the size and direction of external shear force through a cross-shaped sensitive layer, and senses the size of external pressure through a composite sensitive layer, thereby realizing simultaneous perception of external shear force and pressure. However, if the cross-shaped sensitive layer and the composite sensitive layer are simply used in combination, the pressure sensing force and the shear force will interfere with each other, and the accurate perception of the two forces cannot be achieved. At the same time, the perception of the direction of the shear force is more difficult. At the same time, the flexibility of the device will be sacrificed in the direct combination state, and the device cannot be well covered on the surface of the equipment. While the present invention uses a cross-shaped sensitive layer and a composite sensitive layer in combination, it also adopts a composite structure, utilizes the structural characteristics of the contact and the central pillar, transmits the shear force and pressure to their respective sensitive units, separates the shear force and pressure perception, thereby eliminating the influence of mutual interference between the two forces during the detection process, and the contact and central pillar of the high molecular elastomeric polymer ensure the good flexibility of the device.

[0058] This embodiment provides a combined piezoresistive flexible three-dimensional force sensor, which utilizes a flexible structure and piezoresistive resistance technology to improve the stability of the sensor.

[0059] This embodiment provides a combined piezoresistive flexible three-dimensional force sensor, in which the protective shell and outer frame structure of the sensor are located at the outermost part of the sensor, which can reduce the damage to the internal structure caused by external impact and play a role in protecting the internal circuits and sensitive units.

[0060] This embodiment provides a combined piezoresistive flexible three-dimensional force sensor. It adopts a composite structure and utilizes the structural characteristics of the contact and the central pillar to separately transmit the shear force and the pressure to their respective sensitive units, separating the perception of the shear force and the pressure, thereby reducing or even eliminating the mutual interference effect generated by the two forces during the detection process.

[0061] Embodiment 2. Refer to Figure 1 To describe this embodiment, a protective housing 1 is added to the force acquisition unit of a combined piezoresistive flexible three-dimensional force sensor described in Embodiment 1. An opening is provided in the middle of the top of the protective housing 1. The protective housing 1 covers the upper part of the contact 2 and the shear force sensing unit, and the top of the contact 2 extends to the outside of the opening at the top of the protective housing 1.

[0062] In the actual application of this embodiment, an opening is provided in the middle of the top of the protective housing 1. The protective housing 1 covers the upper part of the contact 2 and the shear force sensing unit, and the top of the contact 2 extends to the outside of the opening at the top of the protective housing 1. The protective housing 1 can be set in a quadrilateral shape or an arc shape during actual application and can be flexibly selected according to the actual on-site working requirements. The opening of the protective housing is set to be circular. The thickness of the protective housing 1 is 1 mm. The height of the protective housing and the radius of the circular opening are flexibly selected according to the size of the contact 2, ensuring that the contact 2 can be exposed from the protective housing 1 and the contact does not touch the protective housing.

[0063] Embodiment 3. Refer to Figure 1 To describe this embodiment, an example is given of the shape of the contact 2 in a combined piezoresistive flexible three-dimensional force sensor described in Embodiment 1. The shape of the contact 2 is hemispherical, and the radius of the bottom circle of the hemispherical shape is between 1.5 and 3 mm.

[0064] As an optimal embodiment, the shape of the contact 2 is hemispherical, and the radius of the bottom circle of the hemispherical shape is between 1.5 and 3 mm. The hemispherical structure has good contact and acquisition of three-dimensional forces from all directions and good stability. In actual application, the shape of the contact 2 can also be a columnar structure or a frustum structure. When using a frustum structure, the force-bearing area is wider, increasing the sensing area and having very good stability. It can be flexibly selected according to actual working needs. This embodiment uses a lightweight contact as the three-dimensional force acquisition structure and decomposes the collected three-dimensional force, transmitting the shear force to the cross-shaped sensitive material layer in the shear force sensing part and transmitting the positive pressure to the composite sensitive material layer in the pressure sensing part through the central pillar.

[0065] Embodiment 4. Refer to Figure 1To explain this embodiment, this embodiment is an example of the central pillar 8 in a combined piezoresistive flexible three-dimensional force sensor described in embodiment one. The height of the central pillar 8 is 3 to 10 mm, and the shape of the central pillar 8 is a frustum. The ratio of the radius of the upper end circle and the radius of the lower end circle of the frustum is within 1 to 0.375.

[0066] As an optimal embodiment, the shape of the central pillar 8 is a frustum structure. The frustum structure has better stability, is not easy to deform and bend when transmitting force, does not cause inaccurate force perception, and has a moderate contact area with the third flexible substrate layer to ensure the flexibility of the bottom of the sensor, which can cover the surface of most devices. The ratio of the radius of the upper end face circle of the frustum shape to the radius of the lower end face is within 1 to 0.375, the radius of the upper end face circle of the frustum shape is within 1 to 1.5 mm, and the radius of the lower end face circle is within 1 to 4 mm. In actual application, the shape of the central pillar can also be a columnar structure. The columnar structure has moderate stability and a small contact area with the third flexible substrate layer, which makes the sensor more flexible and can cover the surface of more devices. It can be flexibly selected according to actual work needs.

[0067] Implementation method 5. See Figure 1 This embodiment is described as follows: This embodiment is an example of the shape of the side wall support frame 6 in a combined piezoresistive flexible three-dimensional force sensor described in Embodiment 1. The height of the side wall support frame 6 is the same as that of the central pillar 8, and the wall thickness is 1 to 3 mm.

[0068] As an optimal embodiment, the side wall support frame 6 is in the shape of a cylinder, and a central pillar can be placed inside the cylinder structure to better transmit the decomposed normal force. The cylinder structure serves as a supporting structure, plays a supporting and protective role, and does not affect the perception of force. The height of the side wall support frame 6 is 3 to 10 mm, which is the same as the height of the central pillar 8, and the wall thickness is 1 to 3 mm, which can be flexibly selected according to actual work needs.

[0069] Implementation method 6. See Figure 2 , Figure 3 and Figure 4 To explain this embodiment, this embodiment is an example of the structure of a cross-shaped sensitive material layer in a combined piezoresistive flexible three-dimensional force sensor described in embodiment one, wherein the four tail ends of the cross-shaped sensitive material layer 4 are respectively provided with electrodes, and a common electrode is set at the center of the cross-shaped sensitive material layer.

[0070] In actual application of this embodiment, electrodes are respectively provided at the four tail ends of the cross-shaped sensitive material layer 4, and a common electrode is provided at the exact center of the cross-shaped sensitive material layer 4. When the cross-shaped sensitive material layer senses the shear force transmitted by the contact, each part of the sensitive material layer is deformed, and its resistance value changes. Due to the difference in direction and size, the resistance value changes of the four equivalent resistor structures are also different, thereby realizing the size perception and direction identification of the shear force.

[0071] Implementation method 7. See Figure 2 This embodiment is described. This embodiment is an example of the thickness of the cross-shaped sensitive material layer in the combined piezoresistive flexible three-dimensional force sensor described in the first embodiment. The thickness of the cross-shaped sensitive material layer 4 is 80-100 nm.

[0072] In actual application of this embodiment, the thickness of the cross-shaped sensitive material layer 4 is 80-100 nm. The thickness of the cross-shaped sensitive material layer 4 can be flexibly selected according to the requirements of on-site work.

[0073] Implementation 8. See Figure 5 To explain this embodiment, this embodiment is to exemplify the structure of a composite sensitive material layer 10 in a combined piezoresistive flexible three-dimensional force sensor described in Embodiment 1. The composite sensitive material layer 10 is in the shape of a quadrilateral, and one electrode is respectively provided near adjacent opposite sides of the quadrilateral, and each electrode is connected to an electrode lead wire.

[0074] In actual application of this embodiment, the composite sensitive material layer 10 is in the shape of a quadrilateral, and an electrode is respectively provided near the adjacent opposite sides of the quadrilateral, and each electrode is connected to an electrode lead. When the composite sensitive material layer of the pressure sensing part is subjected to the positive pressure transmitted by the contact and the central pillar, a slight deformation occurs, causing the resistance value of the composite sensitive material layer to change, thereby reflecting the magnitude of the positive pressure. The resistance value change of the sensitive unit measured by the electrode set on the composite sensitive material layer is used to calculate the magnitude of the positive pressure based on the measured value.

[0075] Implementation method 9. See Figure 5 This embodiment is described as follows: This embodiment is an example of the thickness of the composite sensitive material layer in the combined piezoresistive flexible three-dimensional force sensor described in the first embodiment. The thickness of the composite sensitive material layer 10 is 100-180 nm.

[0076] In actual application of this embodiment, the thickness of the cross-shaped sensitive material layer 4 is 100-180 nm. The thickness of the cross-shaped sensitive material layer 4 can be flexibly selected according to the requirements of on-site work.

[0077] Embodiment 10. A method for preparing a combined piezoresistive flexible three-dimensional force sensor according to this embodiment, wherein the method prepares a combined piezoresistive flexible three-dimensional force sensor according to any one of embodiments 1 to 8, and the specific steps are as follows:

[0078] S1, a step of preparing a flexible substrate layer, wherein a high molecular weight polymer is spin-coated on a substrate, and after curing, the polymer is removed from the substrate to obtain a flexible substrate, and a total of four flexible substrates are prepared, wherein the flexible substrates are a first flexible substrate layer 3, a second flexible substrate layer 5, a third flexible substrate layer 9, and a fourth flexible substrate layer 11;

[0079] S2, a step of manufacturing a cross-shaped sensitive material layer 4, attaching a metal mask to the second flexible substrate layer 5, and placing the metal mask in a vapor deposition machine for gold plating, thereby completing the manufacturing of the cross-shaped sensitive material layer 4;

[0080] S3, the steps of making the composite sensitive material layer 10, mixing carbon nanotubes into deionized water, using an ultrasonic disperser to evenly disperse the carbon nanotubes in the solution, and letting it stand, after the surface of the fourth flexible substrate layer 11 is treated with oxygen plasma, taking an appropriate amount of the supernatant of the carbon nanotube solution and applying it to the position treated with oxygen plasma, and after it is naturally extended and the water evaporates to form a carbon nanotube film, it is placed in a vapor deposition machine for gold plating, and the composite sensitive material layer 10 is completed;

[0081] S4. Cover the third flexible substrate layer 9 on the composite sensitive material layer 10, and bond it to the composite sensitive material layer 10 and the fourth flexible substrate layer 11 therebelow; bond and fix the outer frame and the central pillar 8 to the upper surface of the third flexible substrate layer 9; bond the bottom surface of the second flexible substrate layer 5 to the top of the outer frame and the top of the central pillar 8; cover the first flexible substrate layer 3 on the cross-shaped sensitive material layer 4, and bond it to the cross-shaped sensitive material layer 4 and the second flexible substrate layer 5; bond the protective shell 1 and the contact 2 to the upper surface of the first flexible substrate layer 3 to obtain a single sensor.

[0082] In actual application of this embodiment, the outer frame 6, the bracket 7, the protective shell 1 and the contact 2 can be obtained by mold processing. For example, if they are made of polymer materials, the polymers are poured into the molds of the corresponding components respectively. After the polymers are solidified, the solidified polymers are taken out of the mold to obtain the corresponding components: the outer frame 6, the bracket 7, the protective shell 1 and the contact 2.

[0083] This embodiment provides a method for preparing a combined piezoresistive flexible three-dimensional force sensor, in which flexible materials are used to make various parts of the sensor, so that the sensor has good tensile properties and a small geometric volume, and can be covered on a large area on the surface of a smart device, providing it with tactile perception function and enhancing its ability to recognize the external environment.

[0084] In practical application of this embodiment, the high molecular polymer includes polydimethylsiloxane, hydrogenated styrene-butadiene block copolymer or polyurethane. The power of the ultrasonic disperser is 50-70w, the time is 2-4h, the static time is more than 1h, and the concentration of the carbon nanotube solution is 2g / L. The power of the oxygen plasma treatment is 20-70w, and the treatment time is 20-60s.

[0085] Implementation method 11. See Figure 4 , Figure 6 , Figure 7 and Figure 8 This embodiment is described as follows. This embodiment is a test experiment of a combined piezoresistive flexible three-dimensional force sensor described in the first embodiment. Figure 7 As shown, when the shear force structure is tested for direction and force magnitude, the position of the equivalent resistor is as follows Figure 4 As shown. Figure 6 The data of the force size and direction test process for the shear force structure are tested in four directions as direction 1 - direction 2 - direction 3 - direction 4. Each test in four directions is a group. The test is carried out in a cycle. The size of the force applied to the contact is different, and the fluctuation and peak value of the four equivalent resistances are different. The size of the force can be calculated by analysis. Figure 7 for Figure 6 A set of loops that test four directions in Figure 8 The changes in the four equivalent resistances when forces in various directions are applied to the contacts can be determined from the figure. The changes in the four resistances can accurately reflect the forces applied in the four directions. This further proves that the direction and magnitude of the applied force can be obtained through the changes in the resistance values ​​of the four resistances.

[0086] from Figure 6 , Figure 7 and Figure 8 It can be seen that the combined piezoresistive flexible three-dimensional force sensor described in this embodiment can collect shear force and pressure at the same time, and can sense the force in each direction, and the sensed pressure and shear force will not interfere with each other.

[0087] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may be subject to various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the claims of the present invention.

Claims

1. A combined piezoresistive flexible three-dimensional force sensor, It is characterized in that The sensor includes a pressure sensing unit, a support unit, a shear force sensing unit and a force acquisition unit; The pressure sensing unit comprises a third flexible base layer (9), a composite sensitive material layer (10) and a fourth flexible base layer (11), wherein the composite sensitive material layer (10) is arranged between the third flexible base layer (9) and the fourth flexible base layer (11), and the third flexible base layer (9), the composite sensitive material layer (10) and the fourth flexible base layer (11) are bonded together; The support unit comprises an outer frame and a central pillar (8); the outer frame comprises a side wall support frame (6) and a bracket (7); the side wall support frame (6) is cylindrical; the central pillar (8) is fixed at the center of the outer frame; the bracket is located inside the side wall support frame (6); one end of the bracket is fixedly connected to the inner wall of the side wall support frame (6); and the other end is fixedly connected to the outer wall of the central pillar (8); the bracket (7) is in the shape of a cross structure and is made of elastic material; The shear force sensing unit comprises a first flexible base layer (3), a cross-shaped sensitive material layer (4) and a second flexible base layer (5), wherein the cross-shaped sensitive material layer (4) is arranged between the first flexible base layer (3) and the second flexible base layer (5), and the first flexible base layer (3), the cross-shaped sensitive material layer (4) and the second flexible base layer (5) are bonded together; The force collection unit comprises a contact (2), the top of the contact is arc-shaped and the bottom is flat; The pressure sensing unit, the support unit, the shear force sensing unit and the force collection unit are stacked together in sequence from bottom to top, and the central pillar of the support unit is coaxial with the force collection unit.

2. A combined piezoresistive flexible three-dimensional force sensor according to claim 1, It is characterized in that The force collection unit further comprises a protective shell (1), wherein an opening is arranged in the middle of the top of the protective shell (1), the protective shell (1) covers the upper part of the contact (2) and the shear force sensing unit, and the top of the contact (2) extends to the outside of the top opening of the protective shell (1).

3. The combined piezoresistive flexible three-dimensional force sensor according to claim 1, It is characterized in that The contact (2) is in the shape of a hemisphere, and the radius of the bottom circle of the hemisphere is between 1.5 and 3 mm.

4. The combined piezoresistive flexible three-dimensional force sensor according to claim 1, It is characterized in that The height of the central pillar (8) is 3 to 10 mm, the shape of the central pillar (8) is a frustum, and the ratio of the radius of the upper end circle to the radius of the lower end circle of the frustum is within 1 to 0.

375.

5. The combined piezoresistive flexible three-dimensional force sensor according to claim 1, It is characterized in that The side wall support frame (6) is cylindrical in shape, the height of the side wall support frame (6) is the same as that of the central support frame (8), and the wall thickness is 1 to 3 mm.

6. The combined piezoresistive flexible three-dimensional force sensor according to claim 1, It is characterized in that Electrodes are respectively arranged at the four tail ends of the cross-shaped sensitive material layer (4), and a common electrode is arranged at the exact center of the cross-shaped sensitive material layer.

7. The combined piezoresistive flexible three-dimensional force sensor according to claim 1, It is characterized in that The thickness of the cross-shaped sensitive material layer (4) is 80-100 nm.

8. The combined piezoresistive flexible three-dimensional force sensor according to claim 1, It is characterized in that The composite sensitive material layer (10) is in the shape of a quadrilateral, and an electrode is respectively arranged near the opposite sides of the quadrilateral, and each electrode is connected to an electrode lead wire.

9. The combined piezoresistive flexible three-dimensional force sensor according to claim 1, It is characterized in that The thickness of the composite sensitive material layer (10) is 100-180 nm.

10. A method for preparing a combined piezoresistive flexible three-dimensional force sensor, It is characterized in that The three-dimensional force sensor is a three-dimensional sensor according to any one of claims 1 to 8, and the steps of the method are: S1, a flexible substrate layer manufacturing step, wherein a high molecular weight polymer is spin-coated on a substrate, and after curing, the polymer is removed from the substrate to obtain a flexible substrate, and a total of four flexible substrates are manufactured, wherein the flexible substrates are a first flexible substrate layer (3), a second flexible substrate layer (5), a third flexible substrate layer (9) and a fourth flexible substrate layer (11); S2, a step of manufacturing a cross-shaped sensitive material layer (4), attaching a metal mask to the second flexible substrate layer (5), placing the metal mask in a vapor deposition machine for gold plating, and completing the manufacturing of the cross-shaped sensitive material layer (4); S3, the steps of making the composite sensitive material layer (10), mixing carbon nanotubes into deionized water, using an ultrasonic disperser to evenly disperse the carbon nanotubes in the solution, and letting it stand, after subjecting the surface of the fourth flexible substrate layer (11) to oxygen plasma treatment, taking an appropriate amount of the supernatant of the carbon nanotube solution and applying it to the position treated by the oxygen plasma, and after it is naturally extended and the water evaporates to form a carbon nanotube film, it is placed in a vapor deposition machine for gold plating, thereby completing the preparation of the composite sensitive material layer (10); S4. Cover the third flexible substrate layer (9) on the composite sensitive material layer (10) and bond it to the composite sensitive material layer (10) and the fourth flexible substrate layer (11) below it. Bond and fix the outer frame and the central pillar (8) on the upper surface of the third flexible substrate layer (9). Bond the bottom surface of the second flexible substrate layer (5) to the top of the outer frame and the top of the central pillar (8). Cover the first flexible substrate layer (3) on the cross-shaped sensitive material layer (4) and bond it to the cross-shaped sensitive material layer (4) and the second flexible substrate layer (5). Bond the protective shell (1) and the contact (2) to the upper surface of the first flexible substrate layer (3) to obtain a single sensor.

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