Flexible strain sensor and preparation method thereof

Abstract

The invention discloses a flexible strain sensor and a preparation method thereof, and relates to the technical field of sensors, the flexible strain sensor comprises a first flexible substrate layer and a plurality of sensor modules, the plurality of sensor modules are arranged on the first flexible substrate layer in an array structure, each sensor module comprises at least one strain gauge, and the strain gauges are arranged on the first flexible substrate layer. The strain gauges of all the sensor modules are electrically connected, each sensor module, the strain gauge of the sensor module and the first flexible substrate layer corresponding to the bottom protrude outwards to form a protruding structure, and when the protruding structure makes contact with a detected object, the strain gauge on the protruding structure is used for detecting the deformation quantity of the detected object. The flexible strain sensor provided by the embodiment of the invention not only is suitable for hard materials such as metal structures with relatively large rigidity, but also is suitable for elastic or composite materials with large deformation.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, and in particular to a flexible strain sensor and a preparation method thereof. Background Art

[0002] Strain refers to the amount of deformation of a material that stretches or shortens after being subjected to external force. The sensor that detects strain through electrical signals is a strain gauge. A strain gauge is a sensor used to measure the strain and deformation of an object. When a conductor or semiconductor material undergoes mechanical deformation under the action of external force, its resistance value will change accordingly.

[0003] In the prior art, the deformation of the object to be measured is obtained by pasting a strain gauge at the position where the strain needs to be measured. However, pasting a strain gauge is only suitable for hard materials such as metal structures with high rigidity, and it is difficult to paste a strain gauge on elastic or composite materials with large deformation for measurement. Summary of the invention

[0004] The embodiment of the present invention provides a flexible strain sensor and a preparation method thereof to solve the technical problem in the related art that the existing technology of pasting strain gauges is only suitable for hard materials such as metal structures with relatively high rigidity, and it is difficult to paste strain gauges on elastic or composite materials with large deformation for measurement.

[0005] In a first aspect, a flexible strain sensor is provided, comprising:

[0006] a first flexible base layer;

[0007] A plurality of sensor modules, wherein the plurality of sensor modules are arranged on the first flexible substrate layer in an array structure, each of the sensor modules comprises at least one strain gauge, and the strain gauges of all the sensor modules are electrically connected;

[0008] Each sensor module and its strain gauge and the first flexible base layer corresponding to the bottom protrude outward to form a protruding structure. When the protruding structure contacts the object to be measured, the strain gauge on the protruding structure is used to detect the deformation amount of the object to be measured.

[0009] In some embodiments, each of the sensor modules further comprises:

[0010] A first metal layer, an isolation layer and a second metal layer are arranged in sequence from bottom to top, the first metal layer is in the same layer as the strain gauge, the isolation layer and the second metal layer are arranged on the strain gauge in sequence, the strain gauges of all sensor modules are electrically connected through the first metal layer and the second metal layer, and the isolation layer is used to isolate the first metal layer from the second metal layer.

[0011] In some embodiments, there are four strain gauges, and the four strain gauges are arranged circumferentially at intervals;

[0012] The first strain gauge is electrically connected to the second strain gauge through the first metal layer;

[0013] The third strain gauge is electrically connected to the fourth strain gauge through the first metal layer;

[0014] The first strain gauge is electrically connected to the fourth strain gauge through the second metal layer;

[0015] The second strain gauge is electrically connected to the third strain gauge through the second metal layer.

[0016] In some embodiments, each of the strain gauges comprises:

[0017] The second flexible substrate layer, the conductor layer, the connection hole layer and the conductive metal layer are arranged in sequence from bottom to top. The conductor layer is used to detect the deformation amount of the object to be measured, and the connection hole layer and the conductive metal layer are used to achieve electrical connection.

[0018] In some embodiments, the conductor layer includes a transverse gate structure and a longitudinal gate structure, the transverse gate structure is used to detect the transverse deformation of the object under test, and the longitudinal gate structure is used to detect the longitudinal deformation of the object under test.

[0019] In some embodiments, the first flexible base layer, the isolation layer, and the second flexible base layer are all made of polyimide material.

[0020] In some embodiments, the flexible strain sensor further comprises:

[0021] A flexible filler is disposed at the bottom of the first flexible base layer, and the flexible filler forms a protruding structure together with the corresponding first flexible base layer and the sensor module.

[0022] In some embodiments, the flexible filler is made of silicone or fossil-based polymer material.

[0023] In a second aspect, a method for preparing a flexible strain sensor is provided, comprising:

[0024] Step S10, preparing a first flexible substrate layer, a plurality of sensor modules and at least one strain gauge on a silicon wafer substrate by using a MEMS process;

[0025] Step S20, peeling the first flexible base layer, multiple sensor modules and their strain gauges from the silicon wafer base and placing them between a concave mold and a convex mold, and using the convex mold to extrude them so that each sensor module and its strain gauge and the first flexible base layer corresponding to the bottom bulge outward to form a convex structure.

[0026] In some embodiments, after making each of the sensor modules and the strain gauges thereof and the first flexible base layer corresponding to the bottom bulge outward to form a bulge structure, the method includes:

[0027] The convex mold is separated from the first flexible substrate layer, multiple sensor modules and their strain gauges, and a flexible filler is filled on a side of the first flexible substrate layer away from the multiple sensor modules, and then the concave mold is separated from the flexible filler, the first flexible substrate layer, multiple sensor modules and their strain gauges.

[0028] The beneficial effects brought about by the technical solution provided by the present invention include:

[0029] An embodiment of the present invention provides a flexible strain sensor and a preparation method thereof, wherein the flexible strain sensor comprises: a first flexible substrate layer, a plurality of sensor modules, wherein the plurality of sensor modules are arranged on the first flexible substrate layer in an array structure, wherein each of the sensor modules comprises at least one strain gauge, wherein the strain gauges of all the sensor modules are electrically connected, and each of the sensor modules and its strain gauge protrude outward from the first flexible substrate layer corresponding to the bottom to form a protruding structure. When the protruding structure contacts an object to be measured, the strain gauge on the protruding structure is used to detect the deformation amount of the object to be measured, and the deformation amount of the object to be measured can be obtained without pasting the strain gauge at the position where the strain amount is to be measured, and the measurement can be achieved by touching the protruding structure, so that the flexible strain sensor of the embodiment of the present invention is not only suitable for hard materials such as metal structures with relatively large rigidity, but also suitable for elastic or composite materials with large deformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 A schematic diagram of the three-dimensional structure of a flexible strain sensor provided in an embodiment of the present invention;

[0032] Figure 2 A schematic diagram of the planar structure of a flexible strain sensor provided by an embodiment of the present invention;

[0033] Figure 3 A schematic diagram of a transverse cross-sectional structure of a flexible strain sensor provided in an embodiment of the present invention;

[0034] Figure 4 A schematic diagram of a longitudinal cross-sectional structure of a flexible strain sensor provided in an embodiment of the present invention;

[0035] Figure 5 A schematic diagram of the three-dimensional structure of a strain gauge provided in an embodiment of the present invention;

[0036] Figure 6 A schematic diagram of the planar structure of a strain gauge provided in an embodiment of the present invention;

[0037] Figure 7 A schematic diagram of the structure of a concave mold and a convex mold provided in an embodiment of the present invention;

[0038] Figure 8 A schematic diagram of the structure of a flexible filler provided in an embodiment of the present invention;

[0039] Reference numerals:

[0040] 1. A first flexible base layer;

[0041] 2. sensor module; 21. strain gauge; 211. second flexible substrate layer; 212. conductor layer; 2121. transverse grid structure; 2122. longitudinal grid structure; 213. connection hole layer; 214. conductive metal layer; 22. first metal layer; 23. isolation layer; 24. second metal layer;

[0042] 3. Flexible filler;

[0043] 4. Concave mold;

[0044] 5. Convex mold. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] The embodiment of the present invention provides a flexible strain sensor and a preparation method thereof, which can solve the technical problem in the related art that the existing technology of pasting strain gauges is only suitable for hard materials such as metal structures with relatively high rigidity, and it is difficult to paste strain gauges on elastic or composite materials with large deformation for measurement.

[0047] Figure 1 An embodiment of the present invention provides a flexible strain sensor, comprising: a first flexible substrate layer 1 and a plurality of sensor modules 2 .

[0048] Multiple sensor modules 2 are arranged in an array structure on the first flexible substrate layer 1, each of the sensor modules 2 includes at least one strain gauge 21, and the strain gauges 21 of all the sensor modules 2 are electrically connected. Each of the sensor modules 2 and its strain gauge 21 and the first flexible substrate layer 1 corresponding to the bottom protrude outward to form a protruding structure. When the protruding structure contacts the object to be measured, the strain gauge 21 on the protruding structure is used to detect the deformation amount of the object to be measured.

[0049] The flexible strain sensor of the embodiment of the present invention is provided with a first flexible base layer and multiple sensor modules. The multiple sensor modules are arranged on the first flexible base layer in an array structure. Each of the sensor modules includes at least one strain gauge. The strain gauges of all the sensor modules are electrically connected. Each of the sensor modules and its strain gauge protrudes outward from the first flexible base layer corresponding to the bottom to form a protruding structure. When the protruding structure contacts the object to be measured, the strain gauge on the protruding structure is used to detect the deformation amount of the object to be measured. The deformation amount of the object can be obtained without pasting the strain gauge at the position of measuring the strain amount. The measurement can be achieved by touching the protruding structure. Therefore, the flexible strain sensor of the embodiment of the present invention is not only suitable for hard materials such as metal structures with relatively large rigidity, but also suitable for elastic or composite materials with large deformation. Moreover, the three-dimensional structure of the protrusion can simultaneously measure deformations in multiple dimensions or directions, thereby improving the measurement dimension and spatial resolution of the sensor.

[0050] As an optional embodiment, in one embodiment of the invention, see Figure 2 , Figure 3 and Figure 4As shown, each of the sensor modules 2 further includes: a first metal layer 22, an isolation layer 23, and a second metal layer 24 arranged sequentially from bottom to top, the first metal layer 22 and the strain gauge 21 are in the same layer, the isolation layer 23 and the second metal layer 24 are arranged sequentially on the strain gauge 21, the strain gauges 21 of all the sensor modules 2 are electrically connected through the first metal layer 22 and the second metal layer 24, the isolation layer 23 is used to isolate the first metal layer 22 and the second metal layer 24, the first metal layer 22 and the strain gauge 21 are arranged in the same layer, the isolation layer 23 and the second metal layer 24 are arranged sequentially from bottom to top on the strain gauge The sheet 21, i.e., the first metal layer 22, realizes mutual electrical connection of at least one strain gauge 21 in each sensor module 2 through the first metal layer 22 and the second metal layer 24, and also realizes mutual electrical connection of the strain gauges 21 between multiple sensor modules 2. The isolation layer 23 is used to electrically isolate the first metal layer 22 and the second metal layer 24, so that the first metal layer 22 and the second metal layer 24 remain independent, avoiding current from flowing between the first metal layer 22 and the second metal layer 24, which helps to improve the anti-interference ability, safety and reliability of the circuit, and ensure that the circuit can work stably and accurately.

[0051] As an optional embodiment, in one embodiment of the invention, see Figure 2 , Figure 3 and Figure 4 As shown, there are four strain gauges 21, and the four strain gauges 21 are arranged circumferentially at intervals. The first strain gauge 21 is electrically connected to the second strain gauge 21 through the first metal layer 22, the third strain gauge 21 is electrically connected to the fourth strain gauge 21 through the first metal layer 22, the first strain gauge 21 is electrically connected to the fourth strain gauge 21 through the second metal layer 24, and the second strain gauge 21 is electrically connected to the third strain gauge 21 through the second metal layer 24. Figure 2 As shown, taking the first strain gauge 21 set at the upper left corner of each sensor module 2 as the base point and rotating clockwise, there are the second strain gauge 21, the third strain gauge 21 and the fourth strain gauge 21 in sequence. The first strain gauge 21 and the second strain gauge 21 as well as the third strain gauge 21 and the fourth strain gauge 21 are all electrically connected through the first metal layer 22, and the first strain gauge 21 and the fourth strain gauge 21 as well as the second strain gauge 21 and the third strain gauge 21 are all electrically connected through the second metal layer 24, thereby realizing the mutual electrical connection of the first strain gauge 21, the second strain gauge 21, the third strain gauge 21 and the fourth strain gauge 21.

[0052] As an optional embodiment, in one embodiment of the invention, see Figure 5 As shown, each strain gauge 21 includes: a second flexible substrate layer 211, a conductor layer 212, a connection hole layer 213 and a conductive metal layer 214 arranged in sequence from bottom to top, the conductor layer 212 is used to detect the deformation of the object to be measured, the connection hole layer 213 and the conductive metal layer 214 are used to achieve electrical connection, the second flexible substrate layer 211 is a carrier of the conductor layer 212, the conductor layer 212 is a foil resistance strain gauge, that is, a metal foil is used as a sensitive grid, which can convert the strain of the object to be measured into a resistance change. When the conductor layer 212 contacts the object to be measured, the conductor layer 212 converts the strain of the object to be measured into a resistance change and then obtains its deformation, and transmits electrical signals through the connection hole layer 213 and the conductive metal layer 214. The connection hole layer 213 and the conductive metal layer 214 are also used to be electrically connected to the first metal layer 22 and the second metal layer 24.

[0053] As an optional embodiment, in one embodiment of the invention, see Figure 6 As shown, the conductor layer 212 includes a transverse grid structure 2121 and a longitudinal grid structure 2122. The transverse grid structure 2121 is used to detect the transverse deformation of the object under test, and the longitudinal grid structure 2122 is used to detect the longitudinal deformation of the object under test. The transverse grid structure 2121 and the longitudinal grid structure 2122 are sensitive grids. When the measuring point of the object under test is deformed, the sensitive grid is also deformed, thereby causing its resistance to change. This resistance change is converted into the deformation value of the object under test.

[0054] As an optional embodiment, in one embodiment of the invention, see Figure 3 , Figure 4 and Figure 6 The first flexible substrate layer 1, the isolation layer 23, and the second flexible substrate layer 211 are all made of polyimide material. Polyimide is a flexible material, which can make the present invention a flexible tactile sensor suitable for stress perception of electronic skin, elastic or composite materials with large deformation. In addition, polyimide has high mechanical properties, good creep resistance and dimensional stability, and also has insulating properties, and can be used to carry the sensor module 2 and isolate the first metal layer 22 and the second metal layer 24.

[0055] As an optional embodiment, in one embodiment of the invention, see Figure 1 and Figure 8As shown, the flexible strain sensor also includes: a flexible filler 3, which is arranged at the bottom of the first flexible substrate layer 1, and the flexible filler 3 forms a protruding structure together with the corresponding first flexible substrate layer 1 and the sensor module 2. The flexible filler 3 is used to carry the first flexible substrate layer 1 and the multiple sensor modules 2, and forms a flexible tactile sensor together with the first flexible substrate layer 1 and the multiple sensor modules 2, so that the flexible strain sensor of the present invention is not only suitable for hard materials such as metal structures with relatively large rigidity, but also suitable for elastic or composite materials with large deformation.

[0056] As an optional embodiment, in one embodiment of the invention, see Figure 1 and Figure 8 As shown, the flexible filler 3 is made of silicone or fossil-based polymer material. As an excellent insulating material, silicone material can effectively isolate electric current and conduct heat, has good insulating properties, and is also resistant to high temperatures and has good softness and fluidity, making it more flexible in application. Fossil-based polymers have good machinability and can be processed through various molding processes, such as injection molding, extrusion, blow molding, etc., so that products of various shapes and sizes can be manufactured. This good machinability makes fossil-based polymers highly flexible and adaptable in the manufacturing process.

[0057] The present invention also provides a method for preparing a flexible strain sensor. Figure 7 As shown, the following steps are included:

[0058] Step S10, preparing a first flexible substrate layer 1, a plurality of sensor modules 2 and at least one strain gauge 21 on a silicon wafer substrate by using a MEMS process;

[0059] Step S20, peel off the first flexible substrate layer 1, multiple sensor modules 2 and their strain gauges 21 from the silicon wafer substrate and place them between the concave mold 4 and the convex mold 5, and use the convex mold 5 to extrude them so that each of the sensor modules 2 and its strain gauges 21 and the first flexible substrate layer 1 corresponding to the bottom bulge outward to form a convex structure.

[0060] Specifically, when the raised structure contacts the object to be measured, the strain gauge 21 on the raised structure is used to detect the deformation amount of the object to be measured. When there are four strain gauges 21, the ring center of the four strain gauges 21 is the highest point of the raised structure, and the four strain gauges 21 are located around the raised structure to detect the deformation amount of the object to be measured. The deformation amount can be obtained without pasting the strain gauge at the position of measuring the strain amount. The measurement can be achieved by touching the raised structure, so that the flexible strain sensor of the embodiment of the present invention is not only suitable for hard materials such as metal structures with greater rigidity, but also suitable for elastic or composite materials with large deformation.

[0061] As an optional embodiment, in one embodiment of the invention, see Figure 8 As shown, after making each sensor module 2 and its strain gauge 21 and the first flexible substrate layer 1 corresponding to the bottom bulge outward to form a bulging structure, the process includes: separating the convex mold 5 from the first flexible substrate layer 1, the multiple sensor modules 2 and their strain gauges 21, and filling the flexible filler 3 on the side of the first flexible substrate layer 1 away from the multiple sensor modules 2, and then separating the concave mold 4 from the flexible filler 3, the first flexible substrate layer 1, the multiple sensor modules 2 and their strain gauges 21.

[0062] Specifically, after each of the sensor modules 2 and its strain gauge 21 bulge outward with the first flexible substrate layer 1 corresponding to the bottom to form a bulging structure, a flexible filler 3 is filled on the concave side of the first flexible substrate layer 1, i.e., the side away from the sensor module 2, and the flexible filler 3 is smoothed through a grinding process, and the flexible filler 3 fills the groove of the first flexible substrate layer 1. After the filling is completed, the flexible filler 3, the first flexible substrate layer 1, the multiple sensor modules 2 and their strain gauges 21 are separated from the concave mold 4 as a whole.

[0063] In the description of the present invention, it should be noted that the terms "upper", "lower", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on the present invention. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0064] It should be noted that, in the present invention, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0065] The above description is only a specific embodiment of the present invention, so that those skilled in the art can understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but should conform to the widest scope consistent with the principles and novel features of the present invention.

Claims

1. A flexible strain sensor, characterized in that: include: A first flexible substrate layer (1); A plurality of sensor modules (2), wherein the plurality of sensor modules (2) are arranged on the first flexible base layer (1) in an array structure, each of the sensor modules (2) comprises at least one strain gauge (21), and the strain gauges (21) of all the sensor modules (2) are electrically connected; Each sensor module (2) and its strain gauge (21) and the first flexible base layer (1) corresponding to the bottom protrude outward to form a protruding structure; when the protruding structure contacts the object to be measured, the strain gauge (21) on the protruding structure is used to detect the deformation amount of the object to be measured.

2. The flexible strain sensor according to claim 1, characterized in that: Each of the sensor modules (2) further comprises: A first metal layer (22), an isolation layer (23) and a second metal layer (24) are arranged in sequence from bottom to top, the first metal layer (22) is in the same layer as the strain gauge (21), the isolation layer (23) and the second metal layer (24) are arranged in sequence on the strain gauge (21), the strain gauges (21) of all sensor modules (2) are electrically connected via the first metal layer (22) and the second metal layer (24), and the isolation layer (23) is used to isolate the first metal layer (22) from the second metal layer (24).

3. The flexible strain sensor according to claim 2, characterized in that: There are four strain gauges (21), and the four strain gauges (21) are arranged at intervals in the circumferential direction; The first strain gauge (21) is electrically connected to the second strain gauge (21) via the first metal layer (22); The third strain gauge (21) is electrically connected to the fourth strain gauge (21) via the first metal layer (22); The first strain gauge (21) is electrically connected to the fourth strain gauge (21) via the second metal layer (24); The second strain gauge (21) is electrically connected to the third strain gauge (21) via the second metal layer (24).

4. The flexible strain sensor according to claim 3, characterized in that: Each of the strain gauges (21) comprises: A second flexible substrate layer (211), a conductor layer (212), a connection hole layer (213) and a conductive metal layer (214) are arranged in sequence from bottom to top, wherein the conductor layer (212) is used to detect the deformation amount of the object to be measured, and the connection hole layer (213) and the conductive metal layer (214) are used to achieve electrical connection.

5. The flexible strain sensor according to claim 4, characterized in that: The conductor layer (212) comprises a transverse grid structure (2121) and a longitudinal grid structure (2122); the transverse grid structure (2121) is used to detect the transverse deformation of the object being measured, and the longitudinal grid structure (2122) is used to detect the longitudinal deformation of the object being measured.

6. The flexible strain sensor according to claim 4, characterized in that: The first flexible base layer (1), the isolation layer (23), and the second flexible base layer (211) are all made of polyimide material.

7. The flexible strain sensor according to claim 1, characterized in that: Also includes: A flexible filler (3), the flexible filler (3) being arranged at the bottom of the first flexible base layer (1), the flexible filler (3) forming a protruding structure together with the corresponding first flexible base layer (1) and the sensor module (2).

8. The flexible strain sensor according to claim 7, characterized in that: The flexible filler (3) is made of silica gel or fossil-based polymer material.

9. A method for preparing the flexible strain sensor according to claim 1, characterized in that: The following steps are involved: Step S10, using a MEMS process to prepare a first flexible substrate layer (1), a plurality of sensor modules (2) and at least one strain gauge (21) on a silicon wafer substrate; Step S20, peeling the first flexible base layer (1), the plurality of sensor modules (2) and the strain gauges (21) thereof from the silicon wafer base and placing them between a concave mold (4) and a convex mold (5), and using the convex mold (5) to extrude them so that each of the sensor modules (2) and the strain gauges (21) thereof and the first flexible base layer (1) corresponding to the bottom thereof bulge outward to form a bulging structure.

10. The method for preparing a flexible strain sensor according to claim 9, characterized in that: After making each of the sensor modules (2) and the strain gauges (21) thereof and the first flexible base layer (1) corresponding to the bottom bulge outward to form a bulge structure, the method comprises: The convex mold (5) is separated from the first flexible base layer (1), the multiple sensor modules (2) and the strain gauges (21) thereof, and a flexible filler (3) is filled on a side of the first flexible base layer (1) away from the multiple sensor modules (2), and then the concave mold (4) is separated from the flexible filler (3), the first flexible base layer (1), the multiple sensor modules (2) and the strain gauges (21) thereof.

Images