Flexible capacitance strain sensor

Abstract

The invention provides a flexible capacitance strain type sensor which is of a stacked structure, the limiting part is arranged between the packaging layer and the conductive layer, and the tensile property of the limiting part in each layer of the flexible sensor is the maximum, so that under the action of tensile force, even if the packaging layer is broken, the limiting part has high tensile strength, the conductive layer and the dielectric layer can be protected, and the reliability of the flexible capacitance strain type sensor is improved. Therefore, the situation that the detection work is affected due to sensor failure caused by breakage of the conducting layer and the dielectric layer of the sensor can be avoided, the service life of the sensor can be prolonged, and the sensor has wide application prospects in the technical field of flexible electronics.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible electronics and sensors, and in particular relates to a flexible capacitive strain sensor. Background Art

[0002] The rise and development of smart wearable technology has garnered widespread attention for flexible sensors, a key component. Flexible capacitive strain sensors, a commonly used type of flexible sensor, offer advantages such as softness, stretchability, fast response, good linearity, and low cost, making them promising applications in the field of wearable sensing technology.

[0003] Flexible capacitive strain sensors generally have a stacked structure, such as Figure 1 As shown, it includes a first packaging layer, a first conductive layer, a dielectric layer, a second conductive layer and a second packaging layer in sequence. When used, it has one or more deformation properties such as stretchability, bendability, and twistability. As deformation occurs, the capacitance value changes, thereby being able to detect deformation.

[0004] Since the flexible capacitive strain sensor is flexible as a whole, it can bend, stretch, twist, and other deformations under the action of external force. The first packaging layer, the first conductive layer, the dielectric layer, the second conductive layer, and the second packaging layer have certain deformation capabilities. However, the tensile strength of such materials is generally low. Therefore, if the tensile force is large during use, it is often easy to cause the material to break, resulting in the loss of the sensing effect and shortening the service life of the sensor.

[0005] Deformability and tensile strength are important properties that describe a material's behavior under stress, typically characterized by tensile modulus and tensile strength. In engineering practice, these two parameters are crucial for material selection, design, and application. They must be comprehensively considered based on specific engineering requirements and material properties to ensure the material meets design and application requirements.

[0006] Tensile modulus, also known as Young's modulus, describes a material's response to stress during stretching. It indicates the material's stiffness and ability to deform under load. Its value is the ratio of the force required to stretch the material per unit length along its central axis to its cross-sectional area. The larger the tensile modulus, the less the material deforms under load, meaning it is more difficult to stretch. The units of tensile modulus are typically Pascals (Pa) or Megapascals (MPa).

[0007] Tensile strength is the ability of a material to resist damage during stretching, indicating the material's ability to withstand maximum tensile stress when subjected to force, that is, the maximum tensile stress a specimen can withstand until it breaks during a tensile test. The tensile strength is calculated as follows:

[0008] ot=p / Lw

[0009] Where ot is the tensile strength (MPa), Lw is the cross-sectional area of ​​the specimen (mm 2 ).

[0010] That is, the higher the tensile strength, the better the tensile properties of the material, indicating that the material is more difficult to break when subjected to force.

[0011] Therefore, taking into account the deformation ability and stretchability of flexible capacitive strain sensors is a key factor in ensuring the detection stability and service life of the sensors. Summary of the Invention

[0012] In view of the above technical status quo, the present invention provides a flexible capacitive strain sensor that can achieve both good deformation ability and tensile strength.

[0013] The technical solution provided by the present invention is: a flexible capacitive strain sensor with a stacked structure, such as Figure 2 As shown, it includes a first packaging layer, a first conductive layer, a dielectric layer, a second conductive layer and a second packaging layer in sequence, and the first packaging layer, the first conductive layer, the dielectric layer, the second conductive layer and the second packaging layer have deformation capabilities;

[0014] A first limiting portion is provided between the first packaging layer and the first conductive layer;

[0015] A second limiting portion is provided between the second packaging layer and the second conductive layer;

[0016] Among the dielectric layer, the first conductive layer, the first limiting portion and the first packaging layer, the first limiting portion has the greatest tensile strength;

[0017] Among the dielectric layer, the second conductive layer, the second limiting portion and the second packaging layer, the second limiting portion has the greatest tensile strength.

[0018] In actual stretching, in order to facilitate stretching, preferably, stretching parts are provided at both ends of the flexible capacitive strain sensor along the stretching direction, which are recorded as a first stretching part and a second stretching part.

[0019] The first encapsulation layer and the second encapsulation layer may be made of any material, including elastic fiber cloth, elastic silicone rubber, and the like.

[0020] The first conductive layer and the second conductive layer may be made of any material, including liquid metal slurry, elastic metal fiber cloth, elastic conductive silicone rubber, elastic conductive ionic liquid, mixed slurry of elastic metal and elastomer, and the like.

[0021] The dielectric layer may be made of any material, including fiber cloth, elastic silicone rubber, TPU, TPR, TPE, and the like.

[0022] The first limiting portion and the second limiting portion may be made of any material, including carbon materials, metal materials, nylon, polytetrafluoroethylene and other polymer materials.

[0023] like Figure 3 As shown, when the first stretching part is directly connected to one end of each layer and the second stretching part is directly connected to the other end of each layer, each layer is directly stretched when stretched by the first stretching part and the second stretching part, that is, the stretched length of each layer is equal during the stretching process.

[0024] Generally speaking, the material has a larger tensile strength and a larger tensile modulus, that is, a smaller deformation capacity. Therefore, compared with the dielectric layer, the first conductive layer, the first limiting portion and the first packaging layer, the first limiting portion has a larger tensile modulus and a smaller deformation capacity, that is, it is not easily deformed. Similarly, compared with the dielectric layer, the second conductive layer, the second limiting portion and the second packaging layer, the second limiting portion has a larger tensile modulus and a smaller deformation capacity, that is, it is not easily deformed. Therefore, in Figure 3 In the structure shown, the deformation capacity of the flexible capacitive strain sensor is directly limited by the deformation capacity of each layer, and the overall deformation capacity is relatively small. In order to take into account the good tensile strength and good overall deformation capacity of the flexible capacitive strain sensor, the preferred material is Figure 4 Structure, that is, one end of the first packaging layer and one end of the second packaging layer are directly connected to the first stretching part, the other end of the first packaging layer and the other end of the second packaging layer are directly connected to the second stretching part, and the first limiting part, the first conductive layer, the dielectric layer, the second conductive layer and the two ends of the second limiting part are not directly connected to the first stretching part and the second stretching part. When the first stretching part and the second stretching part are stretched, the first packaging layer and the second packaging layer are directly stretched and deformed, causing the first limiting part, the first conductive layer, the dielectric layer, the second conductive layer and the second limiting part to deform. In this structure, in order to improve the deformation sensitivity, preferably, the tensile modulus of the first conductive layer (i.e., the tensile modulus of the first conductive layer; in the present invention, the tensile modulus of a certain layer refers to the tensile modulus of the constituent material of the layer, and when the constituent material of the layer is a composite material, it refers to the tensile modulus of the composite material; in the present invention, the tensile strength of a certain layer refers to the tensile strength of the constituent material of the layer, and when the constituent material of the layer is a composite material, it refers to the tensile strength of the composite material) is smaller than the tensile modulus of the first limiting portion, and the tensile modulus of the first limiting portion is smaller than the tensile modulus of the first packaging layer. As a further preference, the tensile modulus of the dielectric layer is smaller than the tensile modulus of the first conductive layer; similarly, preferably, the tensile modulus of the second conductive layer is smaller than the tensile modulus of the second limiting portion, and the tensile modulus of the second limiting portion is smaller than the tensile modulus of the second packaging layer. As a further preference, the tensile modulus of the dielectric layer is smaller than the tensile modulus of the second conductive layer.

[0025] In addition, in order to balance the good tensile strength and overall deformation ability of the first and second limiting portions, the first and second limiting portions are preferably elongated structures (i.e., their length is much greater than their cross-sectional diameter), with their length direction along the stretching direction and their cross-sectional diameter preferably not greater than 10 mm, more preferably not greater than 2 mm, and most preferably not greater than 1 mm, such as nylon thread, carbon thread, steel wire, polyethylene thread, etc. As a further preferred embodiment, a pleated structure is provided in the first and second limiting portions. As the pleated structure is stretched and expanded, the length is extended, and the first and second limiting portions thus achieve a certain degree of stretchability. As a preferred implementation, the elongated first and second limiting portions are undulating along the stretching direction, forming a pleated structure. In addition, as a preferred implementation, the first limiting portion is provided at both ends of the width direction of the first encapsulation layer, the width direction of the first encapsulation layer being perpendicular to the stretching direction; the second limiting portion is provided at both ends of the width direction of the second encapsulation layer, the width direction of the second encapsulation layer being perpendicular to the stretching direction.

[0026] Preferably, the first stretching portion and the second stretching portion are made of a hard material. In order to facilitate stretching and use, preferably, the first stretching portion and the second stretching portion are designed to be easy to hold, such as a ring shape.

[0027] The flexible capacitive strain sensor is as follows Figure 4 When the structure is , the preparation method comprises the following steps:

[0028] (1) preparing a first limiting portion on the surface of the first encapsulation layer, and preparing a first conductive layer on the surface of the first limiting portion; when the first limiting portion is an elongated structure, preferably, the first limiting portion and the first conductive layer are prepared on the surface of the first encapsulation layer, and the first limiting portion and the first conductive layer do not overlap (i.e., there is no overlapping area between the two);

[0029] A second limiting portion is formed on the surface of the second encapsulation layer, and a second conductive layer is formed on the surface of the second limiting portion. When the second limiting portion is an elongated structure, the second limiting portion and the second conductive layer are preferably formed on the surface of the second encapsulation layer, and the second limiting portion and the second conductive layer do not overlap (i.e., there is no overlapping area between the two);

[0030] (2) The first conductive layer and the second conductive layer are respectively arranged on the upper and lower surfaces of the dielectric layer, and the layers are combined together.

[0031] In the step (1), the preparation methods of the first conductive layer and the second conductive layer are not limited, including screen printing, template printing, coating, thermal transfer and the like.

[0032] In the step (2), the bonding method is not limited and includes methods such as hot pressing, bonding, and sewing.

[0033] When the flexible capacitive strain sensor includes a first stretching portion and a second stretching portion, preferably, step (1) is as follows:

[0034] (1) preparing a first stretching portion and a first limiting portion on the surface of the first packaging layer, and preparing a first conductive layer on the surface of the first limiting portion; when the first limiting portion is an elongated structure, preferably, the first stretching portion, the first limiting portion and the first conductive layer are prepared on the surface of the first packaging layer, and the first stretching portion and the first limiting portion do not overlap with the first conductive layer;

[0035] A second stretching portion and a second limiting portion are prepared on the surface of the second packaging layer, and a second conductive layer is prepared on the surface of the second limiting portion; when the second limiting portion is a slender structure, it is preferred to prepare a second stretching portion, a second limiting portion and a second conductive layer on the surface of the second packaging layer, and the second stretching portion and the second conductive layer do not overlap, and the second limiting portion and the second conductive layer do not overlap.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) The present invention sets a limiting part between the packaging layer and the conductive layer of the flexible capacitive strain sensor. Among the layers of the flexible sensor, the limiting part has the largest tensile strength. Therefore, under the action of tensile force, even if the packaging layer breaks, the limiting part has a high tensile strength and can play a role in protecting the conductive layer and the dielectric layer, thereby protecting the sensor and avoiding sensor failure due to the breakage of the conductive layer and the dielectric layer, which affects the detection work, and can also improve the service life of the sensor.

[0038] (2) In order to take into account both the high tensile strength and good deformation ability of the limiting part, the present invention preferably designs the limiting part to be a slender structure with a pleated structure, which has a certain tensile deformation ability when stretched, and meets different tensile deformation requirements by adjusting the limiting part structure and the pleated structure.

[0039] (3) When a stretching portion is provided at both ends of the flexible capacitive strain sensor, it is preferred that the stretching portion is directly connected to both ends of the packaging layer, but is not directly connected to the end portions of the limiting portion, the conductive layer, and the dielectric layer. When the stretching portion is used for stretching, the packaging layer is directly stretched and deformed, thereby causing the limiting portion, the conductive layer, and the dielectric layer to deform. At this time, the tensile moduli of the dielectric layer, the conductive layer, the limiting portion, and the packaging layer are preferably increased in sequence, which can improve the tensile sensitivity of the sensor.

[0040] (4) The present invention can obtain flexible capacitive strain sensors with different stretching ranges by adjusting the tensile modulus of each layer, thereby meeting different sensing requirements of the flexible capacitive strain sensor.

[0041] (5) The flexible capacitive strain sensor of the present invention has broad application prospects in the field of flexible electronic technology, such as in intelligent robots, intelligent wearable devices, intelligent flexible medical devices, intelligent flexible exercise and health equipment, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a structural schematic diagram of a flexible capacitive strain sensor in the prior art.

[0043] Figure 2 It is a structural schematic diagram of the flexible capacitive strain sensor of the present invention.

[0044] Figure 3 It is a structural schematic diagram of an implementation method of the flexible capacitive strain sensor of the present invention.

[0045] Figure 4 It is a structural schematic diagram of another implementation of the flexible capacitive strain sensor of the present invention.

[0046] Figure 5 Schematic diagram of the structure of the training belt in Example 1 of the present invention.

[0047] Figure 6 Schematic diagram of the exploded structure of each layer of the flexible capacitive strain sensor in Example 1 of the present invention.

[0048] Figure 7 It is a schematic diagram of the overall structure of the flexible capacitive strain sensor in Example 1 of the present invention.

[0049] Figure 8 Schematic diagram of the exploded structure of each layer of the flexible capacitive strain sensor in Example 2 of the present invention.

[0050] Figure 9 It is a schematic diagram of the overall structure of the flexible capacitive strain sensor in Example 2 of the present invention.

[0051] Figure 10 It is a schematic diagram of the exploded structure of the control box in Example 2 of the present invention.

[0052] Figure 5-7 The reference numerals in the drawings are: flexible capacitive strain sensor 1, extension belt 2, control box 3, first packaging layer 11, first hard body 12, first limiting portion 13, first conductive layer 14, second packaging layer 21, second hard body 22, second limiting portion 23, second conductive layer 24, dielectric layer 31, annular structure 41;

[0053] Figure 8-10 The figures are as follows: first packaging layer 111, first hard body 112, first limiting part 113, first conductive unit 114, first conductor 115, second packaging layer 121, second hard body 122, second limiting part 123, second conductive unit 124, second conductor 125, dielectric layer 131, dielectric layer 132, annular structure 141, first fixed male buckle 151, second fixed male buckle 152, third fixed male buckle 153, upper shell 31, lower shell 32, button 33, circuit board 34, battery 35, first fixed female buckle 361, second fixed female buckle 362, third fixed female buckle 363. DETAILED DESCRIPTION

[0054] The present invention is further described in detail below in conjunction with the embodiments and drawings. It should be noted that the embodiments described below are intended to facilitate understanding of the present invention and do not have any limiting effect on the present invention.

[0055] Example 1:

[0056] like Figure 5 As shown, in this embodiment, the training belt includes a flexible capacitive strain sensor 1, an extension belt 2 and a control box 3.

[0057] like Figure 6-7 As shown, the flexible capacitive strain sensor has a stacked structure, which includes a first packaging layer 11, a first limiting portion 13, a first conductive layer 14, a dielectric layer 31, a second conductive layer 24, a second limiting portion 23 and a second packaging layer 21 in sequence.

[0058] In this embodiment, the first encapsulation layer 11 and the second encapsulation layer 21 are elastic fiber cloth with a tensile elasticity of 90% (in the present invention, tensile elasticity = (length after stretching - length before stretching) ÷ length before stretching × 100%), with a tensile modulus of 34.08 MPa and a tensile strength of 55.4 MPa; the first conductive layer 14 and the second conductive layer 24 are made of liquid metal with a tensile elasticity of 100%, with a tensile modulus of 24.25 MPa and a tensile strength of 66.8 MPa; the dielectric layer 31 is a TPU film with a tensile elasticity of 120%, with a tensile modulus of 14.86 MPa and a tensile strength of 51.2 MPa.

[0059] In this embodiment, the first limiting portion 13 and the second limiting portion 23 are designed as slender structures, and nylon wire, carbon wire, steel wire, polyethylene wire, etc. can be selected. In this embodiment, a polytetrafluoroethylene wire with a wire diameter of 0.16 mm is selected, which has a tensile modulus of 29.77 MPa and a tensile strength of 151.6 MPa. In addition, in this embodiment, the polytetrafluoroethylene wire has a wavy structure along the stretching direction. When stretched, it can be stretched and unfolded to extend its length, achieving a tensile elasticity of 98%. In this embodiment, the width direction of the first encapsulation layer 11 is perpendicular to the stretching direction, and the width direction of the second encapsulation layer 21 is perpendicular to the stretching direction. The first limiting portion 13 is arranged at both ends of the width direction of the first encapsulation layer 11 and does not overlap with the first conductive layer 14. The second limiting portion 23 is arranged at both ends of the width direction of the second encapsulation layer 21 and does not overlap with the second conductive layer 24.

[0060] In this embodiment, stretching portions are provided at both ends of the flexible capacitive strain sensor along the stretching direction, referred to as a first stretching portion and a second stretching portion. In this embodiment, the first stretching portion and the second stretching portion are made of a hard material, polyurethane, and are designed in a ring shape for easy gripping.

[0061] In this embodiment, Figure 4 As shown, one end of the first packaging layer and one end of the second packaging layer are directly connected to the first stretching part, and the other end of the first packaging layer and the other end of the second packaging layer are directly connected to the second stretching part, while the first limiting part, the first conductive layer, the dielectric layer, the second conductive layer and the two ends of the second limiting part are not directly connected to the first stretching part and the second stretching part. When the first stretching part and the second stretching part are stretched, the first packaging layer and the second packaging layer are directly stretched and deformed, driving the first limiting part, the first conductive layer, the dielectric layer, the second conductive layer and the second limiting part to deform.

[0062] In this embodiment, the preparation method of the flexible capacitive strain sensor is as follows:

[0063] (1) A polyurethane film is adhered to both ends of the length of the surface of the first encapsulation layer 11 to form a first hard body 12; a liquid metal slurry is coated on the surface of the first encapsulation layer 11 by screen printing to prepare a first conductive layer 14; a polytetrafluoroethylene wire is hot pressed on both ends of the width of the surface of the first encapsulation layer 11; and the first hard body 12, the first conductive layer 14 and the polytetrafluoroethylene wire do not overlap with each other;

[0064] A polyurethane film is adhered to both ends of the length of the second encapsulation layer 21 to form a second rigid body 22. An annular structural member 41 is embedded in the second rigid body 22. In this embodiment, the annular structural member 41 is a metal ring. A second conductive layer 24 is formed by screen-printing a liquid metal slurry on the second encapsulation layer 21. A polytetrafluoroethylene thread is hot-pressed on both ends of the width of the second encapsulation layer 21. The second rigid body 22, the second conductive layer 24, and the polytetrafluoroethylene thread do not overlap.

[0065] (2) The first conductive layer 14 and the second conductive layer 24 are respectively arranged on the upper and lower surfaces of the dielectric layer 31, and the first conductive layer 14, the dielectric layer 31 and the second conductive layer 24 are combined together by a hot pressing method, and the first packaging layer 11, the first hard body 12, the second hard body 22 and the second packaging layer 21 are combined together.

[0066] In this embodiment, the overall tensile elasticity of the flexible capacitive strain sensor is 90%, which is a large strain tensile sensor.

[0067] In this embodiment, the extension belt 2 is preferably made of inelastic flexible fabric, and its two ends are connected to the two ends of the flexible capacitive strain sensor 1 through Velcro.

[0068] In this embodiment, the first electrode is connected to the first conductive layer, the second electrode is connected to the second conductive layer, and the first and second electrode leads are electrically connected to the controller. The control box 3 includes a data acquisition unit, a central processing unit, a wireless transmission unit, and a battery unit. The data acquisition unit is used to collect capacitance values; the central processing unit is used to process the collected capacitance values; and the wireless transmission unit is used to wirelessly transmit data signals.

[0069] Example 2:

[0070] In this embodiment, the training belt is basically the same as the training belt in embodiment 1. The difference is that in this embodiment, the lead wire is convenient and the control box is easy to install. Figure 8 、 9 As shown, the first conductive layer is composed of two symmetrical parts, each part is a first conductive unit 114 with a protruding structure, and the two protruding structures are connected by a first conductor 115; the second conductive layer is composed of two symmetrical parts, each part is a second conductive unit 124 with a protruding structure, and the two protruding structures are connected by a second conductor 125.

[0071] like Figure 10As shown, the control box includes an upper shell 31, a lower shell 32, a button 33, a circuit board 34, and a battery 35. A first fixing female buckle 361, a second fixing female buckle 362, and a third fixing female buckle 363 are also included. The circuit board 34 comprises a data acquisition unit, a data processing unit, and a data transmission module. The first, second, and third fixing female buckles 361, 362, and 363 are welded to the circuit board and are preferably positioned in a triangular configuration.

[0072] A first fixing male buckle 151 is provided on the first conductor 115 and connects to a first fixing female buckle 361 on the control box. A second fixing male buckle 152 is provided on the second conductor and connects to a second fixing female buckle 362 on the control box. A third fixing male buckle 153 is provided between the first conductor 115 and the second conductor 125 and connects to a third fixing female buckle 363 on the control box. The first fixing male buckle 151, the second fixing male buckle 152, the third fixing male buckle 153, the first fixing female buckle 361, the second fixing female buckle 362, and the third fixing female buckle 363 are preferably one or more of magnetic buckles, buttons, and electrode buckles.

[0073] In this embodiment, the training belt can be used to assist abdominal breathing, for example, it can be used in postpartum recovery, and can restore the pelvic floor muscles and rectus abdominis muscles through abdominal breathing, thereby achieving the effect of fat reduction and plasticity.

[0074] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A flexible capacitive strain sensor, having a stacked structure, sequentially comprising a first packaging layer, a first conductive layer, a dielectric layer, a second conductive layer and a second packaging layer, wherein the first packaging layer, the first conductive layer, the dielectric layer, the second conductive layer and the second packaging layer all have deformation capability; wherein: A first limiting portion is provided between the first packaging layer and the first conductive layer; A second limiting portion is provided between the second packaging layer and the second conductive layer; Among the dielectric layer, the first conductive layer, the first limiting portion and the first packaging layer, the first limiting portion has the largest tensile strength; Among the dielectric layer, the second conductive layer, the second limiting portion and the second packaging layer, the second limiting portion has the largest tensile strength.

2. The flexible capacitive strain sensor according to claim 1, characterized in that: Along the stretching direction, stretching parts are arranged at both ends of the flexible capacitive strain sensor, which are denoted as a first stretching part and a second stretching part.

3. The flexible capacitive strain sensor according to claim 2, characterized in that: The first stretching portion directly connects the first packaging layer, the first limiting portion, the first conductive layer, the dielectric layer, the second conductive layer, the second limiting portion and one end of the second packaging layer, and the second stretching portion directly connects the first packaging layer, the first limiting portion, the first conductive layer, the dielectric layer, the second conductive layer, the second limiting portion and the other end of the second packaging layer.

4. The flexible capacitive strain sensor according to claim 2, characterized in that: One end of the first encapsulation layer and one end of the second encapsulation layer are directly connected to the first stretching portion; the other end of the first encapsulation layer and the other end of the second encapsulation layer are directly connected to the second stretching portion; The first limiting part, the first conductive layer, the dielectric layer, the second conductive layer and the two ends of the second limiting part are not directly connected to the first stretching part and the second stretching part. When the first stretching part and the second stretching part are stretched, the first packaging layer and the second packaging layer are directly stretched and deformed, driving the first limiting part, the first conductive layer, the dielectric layer, the second conductive layer and the second limiting part to deform.

5. The flexible capacitive strain sensor according to claim 4, characterized in that: The tensile modulus of the first conductive layer is smaller than the tensile modulus of the first limiting portion, and the tensile modulus of the first limiting portion is smaller than the tensile modulus of the first encapsulation layer; The tensile modulus of the second conductive layer is smaller than the tensile modulus of the second limiting portion, and the tensile modulus of the second limiting portion is smaller than the tensile modulus of the second encapsulation layer; Preferably, the tensile modulus of the dielectric layer is smaller than the tensile modulus of the first conductive layer; Preferably, the tensile modulus of the dielectric layer is smaller than the tensile modulus of the second conductive layer.

6. The flexible capacitive strain sensor according to claim 1, characterized in that: The first limiting portion is an elongated structure, and its length direction is along the stretching direction; The second limiting portion is an elongated structure, and its length direction is along the stretching direction; Preferably, the cross-sectional diameter of the first limiting portion is not greater than 10 mm, more preferably not greater than 2 mm, and most preferably not greater than 1 mm; Preferably, the cross-sectional diameter of the second limiting portion is no greater than 10 mm, more preferably no greater than 2 mm, and most preferably no greater than 1 mm.

7. The flexible capacitive strain sensor according to claim 6, characterized in that: The first limiting portion is provided with a pleated structure, and the pleated structure is stretched and expanded along with the stretching; The second limiting portion is provided with a pleated structure, and the pleated structure is stretched and expanded along with the stretching; Preferably, along the stretching direction, the first limiting portion is undulating; Preferably, along the stretching direction, the second limiting portion is wavy.

8. The flexible capacitive strain sensor according to claim 7, characterized in that: The first limiting parts are arranged on both sides of the first encapsulation layer in a width direction, and the width direction of the first encapsulation layer is perpendicular to the stretching direction; The second limiting portions are arranged on both sides of the second encapsulation layer in a width direction, and the width direction of the second encapsulation layer is perpendicular to the stretching direction.

9. The flexible capacitive strain sensor according to claim 7, characterized in that: The first stretching portion and the second stretching portion are made of hard material; Preferably, the first stretching portion and the second stretching portion are designed to be in a shape that is easy to hold.

10. The flexible capacitive strain sensor according to claim 1, characterized in that: The constituent material of the first limiting part includes one or more of carbon material, metal material, and polymer material; The second limiting portion is made of a material comprising one or more of a carbon material, a metal material, and a polymer material.

11. The flexible capacitive strain sensor according to any one of claims 1 to 10, characterized in that: The method for preparing the flexible capacitive strain sensor comprises the following steps: (1) preparing a first limiting portion on the surface of the first encapsulation layer, and preparing a first conductive layer on the surface of the first limiting portion; when the first limiting portion is an elongated structure, preferably the first limiting portion and the first conductive layer are prepared on the surface of the first encapsulation layer, and the first limiting portion and the first conductive layer do not overlap; A second limiting portion is prepared on the surface of the second packaging layer, and a second conductive layer is prepared on the surface of the second limiting portion; when the second limiting portion is an elongated structure, the second limiting portion and the second conductive layer are preferably prepared on the surface of the second packaging layer, and the second limiting portion and the second conductive layer do not overlap; (2) The first conductive layer and the second conductive layer are respectively disposed on the upper and lower surfaces of the dielectric layer to combine the layers together.

12. The flexible capacitive strain sensor according to claim 11, characterized in that: When the flexible capacitive strain sensor includes a first stretching portion and a second stretching portion, the step (1) is as follows: (1) preparing a first stretching portion and a first limiting portion on the surface of the first encapsulation layer, and preparing a first conductive layer on the surface of the first limiting portion; when the first limiting portion is an elongated structure, preferably the first stretching portion, the first limiting portion and the first conductive layer are prepared on the surface of the first encapsulation layer, and the first stretching portion and the first conductive layer do not overlap, and the first limiting portion and the first conductive layer do not overlap; A second stretching portion and a second limiting portion are prepared on the surface of the second packaging layer, and a second conductive layer is prepared on the surface of the second limiting portion; when the second limiting portion is an elongated structure, it is preferred to prepare a second stretching portion, a second limiting portion and a second conductive layer on the surface of the second packaging layer, and the second stretching portion and the second conductive layer do not overlap, and the second limiting portion and the second conductive layer do not overlap.

13. The flexible capacitive strain sensor according to claim 11 or 12, characterized in that: In the step (1), the preparation method of the first conductive layer and the second conductive layer includes one or more of screen printing, template printing, coating, and thermal transfer.

14. The flexible capacitive strain sensor according to claim 11 or 12, characterized in that: In the step (2), the bonding method includes one or more of heat pressing, bonding, and sewing.

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