A knitted fabric flexible capacitive sensor

Abstract

The present invention relates to a knitted fabric flexible capacitive sensor comprising a first knitted fabric layer, a second knitted fabric layer, and an intermediate layer. The first knitted fabric layer and the second knitted fabric layer are connected to each other by spacer yarns woven between them, and the spacer yarns constitute the intermediate layer. The first knitted fabric layer and the second knitted fabric layer are both formed by mutually interlaced conductive yarns. The spacer yarns are insulating elastic yarns and are connected to the first knitted fabric layer and the second knitted fabric layer by tucking. The knitted fabric flexible capacitive sensor of the present invention is integrally formed, has a simple structure, and has good stretchability and compressibility. It can detect compressive loads or tensile loads and output the specific load value. It can be widely used in fields such as human motion monitoring and human-computer interaction.

Description

Technical Field

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

[0002] With the rapid development of wearable artificial intelligence devices, flexible sensors, due to their stretchability and lightweight advantages, are gradually showing broad application prospects in areas such as human motion monitoring, electronic skin, and human-computer interaction. Based on the sensing principle, flexible sensors are divided into resistive sensors, piezoelectric sensors, and capacitive sensors. Among them, capacitive sensors have the advantages of high sensitivity, short response time, wide detection range, and strong environmental adaptability, and thus have a wider range of applications.

[0003] Knitted fabrics have excellent extensibility and elasticity. A knitted flexible capacitive sensor, constructed from a multilayer composite structure of conductive yarn and insulating elastic yarn, undergoes a compressive load, causing the distance between the first and second knitted layers to change, resulting in a change in capacitance and thus acting as a capacitive pressure sensor. Under a tensile load, the surface area of the first and second knitted layers changes, along with the distance between them. This change in capacitance also creates a capacitive strain sensor.

[0004] Knitted fabric flexible capacitive sensors are soft, breathable, stretchable, and easily integrated with other carriers (such as clothing, seat cushions, and gloves), greatly improving the comfort of wearable AI devices. Knitted fabric flexible capacitive sensors can be integrated directly into the fabric, by gluing, or through other methods.

[0005] The paper (Batch Fabrication of Customizable Silicone-Textile Composite Capacitive Strain Sensors for Human Motion Tracking [J]. Advanced Materials Technologies, 2017:1700136.) discloses a capacitive sensor with a highly stretchable silver-plated knitted fabric as the electrode layer, separated by a silicone elastomer as the dielectric. The sensor exhibits high linearity, low hysteresis, and high sensitivity. However, its multilayer structure requires specialized tools for multiple coatings and drying, making the manufacturing process complex. Because the silver-plated knitted fabric used as the electrode layer must be coated and dried multiple times to bond the dielectric layer to the electrode layer, the sensor cannot be directly woven into a substrate and must be integrated by hand sewing.

[0006] Patent CN106884257A discloses a weft-knitted fabric strain sensor, comprising a sensing region and a connecting region. The sensing region is composed of plain-stitched plating loops woven from a conductive face yarn and an elastic ground yarn, with the conductive yarn in a bent configuration. The connecting regions, located on either side of the sensing region, are composed of plain-stitched plating loops made from a face yarn and an elastic ground yarn. This sensor is a resistive strain sensor with high sensitivity, knittability, and the ability to be directly woven into a carrier. However, the sensor can only detect tensile loads, not compressive loads.

[0007] Patent CN114111878A discloses a capacitive sensor comprising a first conductive layer, a second conductive layer, an electromagnetic shielding element, and a spacer fabric. The spacer fabric is disposed between the first and second conductive layers and has a first thickness. The capacitive sensor can be in the form of a flexible capacitive sensing pad. A capacitive detection circuit generates a detection signal when the spacer fabric is compressed to a second thickness. This sensor can only detect the presence of a pressure load above a specific value, not the specific value of the pressure load. Furthermore, the spacer fabric serves only as a dielectric layer, separating the first and second conductive layers.

[0008] Patent CN210014750U discloses a capacitive elastic strain sensor based on an elastic textile material. It can be integrated into wearable devices to detect stress and strain such as stretching and bending in the body. The sensor comprises an elastic bonding layer, a first conductive layer, a second conductive layer, an elastic dielectric layer, and an elastic encapsulation layer. The sensor has a low thickness, which improves its wearability and comfort. Although the sensor is based on an elastic textile material, it has poorer moisture absorption and air permeability than knitted fabric sensors and cannot be directly woven into a carrier.

[0009] Therefore, it is of great significance to study a high-sensitivity sensor that is easy to integrate and can accurately detect the size of tensile load or compressive load to solve the problems existing in the existing technology. Summary of the Invention

[0010] The purpose of the present invention is to solve the problems existing in the prior art and provide a knitted fabric flexible capacitive sensor.

[0011] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0012] A knitted fabric flexible capacitive sensor comprises a planar first knitted fabric layer, a planar second knitted fabric layer and an intermediate layer;

[0013] The first knitted fabric layer and the second knitted fabric layer are connected to each other by weaving spacer yarns therebetween, the spacer yarns constituting the intermediate layer;

[0014] The first knitted fabric layer and the second knitted fabric layer are both formed by mutually interlacing conductive yarns;

[0015] The spacer yarn is an insulating elastic yarn, and connects the first knitted fabric layer and the second knitted fabric layer in the form of tuck loops.

[0016] As the preferred technical solution:

[0017] In the above-mentioned flexible capacitive sensor for knitted fabrics, the tucks are full-needle tucks or spaced-needle tucks.

[0018] As described above, a knitted fabric flexible capacitive sensor, the conductive yarn is one or more of metal-based conductive yarn, carbon-based conductive yarn and conductive polymer yarn; the present invention only lists common conductive yarns, and other yarns that can achieve this function are also suitable for the present invention.

[0019] In the knitted fabric flexible capacitive sensor as described above, the insulating elastic yarn is spandex, latex yarn or thermoplastic elastomer yarn.

[0020] As described above, the knitted fabric flexible capacitive sensor, the thermoplastic elastomer yarn is a polyester thermoplastic elastomer, a polystyrene thermoplastic elastomer, a polyolefin thermoplastic elastomer, a polydiene thermoplastic elastomer, a polyvinyl chloride thermoplastic elastomer, a polyurethane thermoplastic elastomer, a polyamide thermoplastic elastomer, a polyorganofluorine thermoplastic elastomer, a polysilicone thermoplastic elastomer or a polyethylene thermoplastic elastomer polyester yarn, polyamide yarn, organic fluorine yarn, polyolefin yarn or a mixed multifilament thereof; the present invention only lists common substances that can be used to make insulating elastic yarns, and other substances that can achieve this function are also suitable for the present invention.

[0021] After the thermoplastic elastomer yarn is woven between the first knitted fabric layer and the second knitted fabric layer, the thermoplastic elastomer yarn is melted by heat pressing to form an elastomer block material.

[0022] The knitted fabric flexible capacitive sensor as described above, wherein the linear density of the conductive yarn is 22-280 dtex, and the linear density of the insulating elastic yarn is 22-280 dtex;

[0023] The thickness of the first knitted fabric layer is 1-3 mm, the thickness of the second knitted fabric layer is 1-3 mm, and the thickness of the intermediate layer is 1-3 mm.

[0024] A knitted fabric flexible capacitive sensor as described in any one of the above items, wherein the knitted fabric flexible capacitive sensor can be used to detect a tensile load or a compressive load;

[0025] Under a tensile load, the surface areas of the first knitted fabric layer and the second knitted fabric layer in the knitted fabric flexible capacitive sensor change, and simultaneously the distance between the first knitted fabric layer and the second knitted fabric layer changes, causing the capacitance to change;

[0026] Under a compressive load, the distance between the first knitted fabric layer and the second knitted fabric layer in the knitted fabric flexible capacitive sensor changes, causing the capacitance to change.

[0027] The knitted fabric flexible capacitive sensor can withstand a tensile stress of 0.01 to 300 N within a 50% tensile strain range and a compressive stress of 0.1 to 4 × 10 5 Pa pressure.

[0028] A knitted fabric flexible capacitive sensor as described above, wherein the sensitivity range of the knitted fabric flexible capacitive sensor is 1 to 2;

[0029] After one knitted fabric flexible capacitive sensor is cut into multiple capacitive sensors of the same shape, under the same tensile load or compressive load, the cut capacitive sensors have consistent baseline capacitance values and consistent sensitivities.

[0030] The principles of the present invention are as follows:

[0031] In the present invention, the first and second knitted fabric layers are formed by mutually interlacing conductive yarns, serving as the first and second electrode layers, respectively. A middle layer, composed of insulating elastic yarn, connects the first and second knitted fabric layers via tucks during the knitting process, serving as a dielectric layer. Under a tensile load, the surface areas of the first and second knitted fabric layers change, and the distance between them also changes, causing a change in capacitance. Under a compressive load, the distance between them also changes, causing a change in capacitance. The unique three-layer composite structure provides a specific initial spacing between the two electrode layers, enabling the knitted flexible capacitive sensor to achieve a stable base capacitance value. The insulating elastic yarn serves as the spacer yarn of the knitted spacer fabric, giving the knitted flexible capacitive sensor a high sensitivity. Furthermore, the first and second knitted fabric layers of the knitted flexible capacitive sensor are formed by mutually interlacing coils of conductive yarn to form a conductive network, allowing the sensor to be cut into any shape while retaining a high sensitivity.

[0032] Beneficial effects:

[0033] (1) The knitted fabric flexible capacitive sensor of the present invention is integrally formed and has good weavability. It can be integrated into a carrier by direct weaving or other means and has a simple structure.

[0034] (2) The knitted fabric flexible capacitive sensor of the present invention has good stretchability and compressibility, can detect compressive load or tensile load, and output the specific numerical value of the load (by detecting the change of capacitance value and then obtaining the specific load value corresponding to different capacitance values through data processing); it can be applied to the fields of human motion monitoring, human-computer interaction, etc.

[0035] (3) The knitted fabric flexible capacitive sensor of the present invention uses insulating elastic yarn as the middle layer, i.e., the dielectric layer, which gives the sensor higher sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the front coil structure of the knitted fabric flexible capacitive sensor of the present invention;

[0037] Figure 2 This is a schematic diagram of the cross-sectional structure of the knitted fabric flexible capacitive sensor after hot pressing treatment of the present invention;

[0038] Figure 3 This is a working principle diagram of the knitted fabric flexible capacitive sensor before and after compression load of the present invention; Figure 3 (a) is the working principle diagram of the knitted fabric flexible capacitive sensor before compression load. Figure 3 (b) is a diagram showing the working principle of the knitted fabric flexible capacitive sensor before and after compression load; where S is the surface area, d is the distance between the first and second knitted fabric layers before compression, and d0 is the distance between the first and second knitted fabric layers after compression;

[0039] Figure 4 This is a working principle diagram of the knitted fabric flexible capacitive sensor before and after stretching load of the present invention; Figure 4 (a) is the working principle diagram of the knitted fabric flexible capacitive sensor before stretching load. Figure 4 (b) is a diagram showing the working principle of the knitted fabric flexible capacitive sensor after stretching. Here, S is the surface area, d is the distance between the first and second knitted fabric layers before stretching, and d0 is the distance between the first and second knitted fabric layers after stretching. S0 is the surface area after stretching.

[0040] Among them, 1 is the first knitted fabric layer, 2 is the second knitted fabric layer, and 3 is the middle layer. DETAILED DESCRIPTION

[0041] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0042] The test methods involved in the performance indicators of the present invention are as follows:

[0043] The knitted fabric flexible capacitive sensor of this invention was placed between the indenter / chuck of a YG028 fabric strength tester. A conductive yarn was extended from each of the first and second knitted fabric layers of the sensor to connect to the two electrode chucks of a TH283X series compact LCR digital bridge, creating a complete conductive path. During testing, the digital bridge monitored and recorded changes in the sensor's capacitance in real time, while the fabric strength tester monitored changes in tensile stress / compression applied to the sensor.

[0044] During the test, the pressure head of the testing instrument YG028 fabric strength tester used completely covers the sensor, that is, during the compression process, the sensor is evenly stressed and slight changes in surface area can be ignored.

[0045] (1) Tensile stress: The tensile stress to which the present invention is subjected during the test is directly measured by a YG028 fabric strength meter.

[0046] (2) Pressure: The pressure to which the present invention is subjected during the test cannot be directly measured, but the pressure can be directly measured. Therefore, its value can be directly calculated using a theoretical formula. The theoretical formula is as follows:

[0047] ;

[0048] in, is the pressure; F is the pressure; S is the force-bearing area, that is, the surface area.

[0049] (3) Sensitivity: The sensitivity of the present invention cannot be directly measured, but the change in capacitance during the test can be directly measured. Therefore, its value can be directly calculated using a theoretical formula. The theoretical formula is as follows:

[0050] ;

[0051] in, is the capacitance value after load; is the initial state capacitance value; For strain.

[0052] Example 1

[0053] A knitted flexible capacitive sensor is knitted using 280D silver yarn as the conductive yarn and 120D spandex as the spacer yarn on a computerized flat knitting machine (machine gauge: 14). The first knitting cycle is formed by knitting the silver yarn on the front needle bed, the second knitting cycle is formed by knitting the silver yarn on the rear needle bed, and the third knitting cycle is formed by knitting the spandex full needles. The above three knitting cycles form a fabric row, that is, every three knitting cycles constitute a knitting cycle.

[0054] like Figure 1As shown, the knitted fabric flexible capacitive sensor comprises a planar first knitted fabric layer 1, a planar second knitted fabric layer 2, and an intermediate layer 3; the first knitted fabric layer 1 and the second knitted fabric layer 2 are both formed by interlacing silver threads, and the intermediate layer 3 is woven from elastic yarn spandex. The first knitted fabric layer 1 and the second knitted fabric layer 2 are connected by full-needle tucks, and the elastic yarn spandex in the intermediate layer 3 tightens the first knitted fabric layer 1 and the second knitted fabric layer 2; the first knitted fabric layer 1 and the second knitted fabric layer 2 serve as electrode layers of the knitted fabric flexible capacitive sensor, and the intermediate layer 3 serves as a dielectric layer of the knitted fabric flexible capacitive sensor;

[0055] The thickness of the first knitted fabric layer 1 is 1.42 mm, the thickness of the second knitted fabric layer 2 is 1.42 mm, and the thickness of the intermediate layer 3 is 2.37 mm;

[0056] The knitted fabric flexible capacitive sensor has a gram weight of 354g / m 2 The horizontal density is 14.3 columns / inch and the vertical density is 12.6 rows / inch.

[0057] Knitted fabric flexible capacitive sensors can be used to detect tensile or compressive loads;

[0058] like Figure 4 As shown, under a tensile load, the surface areas of the first knitted fabric layer and the second knitted fabric layer in the knitted fabric flexible capacitive sensor change, and at the same time, the distance between the first knitted fabric layer and the second knitted fabric layer changes, causing the capacitance to change;

[0059] like Figure 3 As shown, under compression load, the distance between the first knitted fabric layer and the second knitted fabric layer in the knitted fabric flexible capacitive sensor changes, causing the capacitance to change;

[0060] The knitted fabric flexible capacitive sensor can withstand a tensile stress of 0.01~300N in the range of 50% tensile strain and a compressive stress of 0.1~3.2×10 5 The sensitivity of the knitted fabric flexible capacitive sensor is 1.23; after 10,000 cycles of compression or stretching, the repeatability error δ R压缩 = 3.74%, δ R拉伸 = 3.21%, showing excellent cycle stability and dynamic durability;

[0061] After a knitted flexible capacitive sensor is cut into multiple capacitive sensors of the same shape, under the same tensile load or compressive load, the baseline capacitance values and sensitivities of the cut capacitive sensors are consistent.

[0062] Example 2

[0063] A knitted flexible capacitive sensor is basically the same as Example 1, except that the conductive yarn is 95D / 12f C / PET multifilament (the mass fraction of C is 30.51%), the spacer yarn is 60D latex yarn, and the sensor is knitted using a computerized flat knitting machine (machine gauge: 20).

[0064] like Figure 1 As shown, the knitted fabric flexible capacitive sensor comprises a planar first knitted fabric layer 1, a planar second knitted fabric layer 2, and an intermediate layer 3; the first knitted fabric layer 1 and the second knitted fabric layer 2 are both made of C / PET multifilaments strung together, and the intermediate layer 3 is woven from latex yarns. The first knitted fabric layer 1 and the second knitted fabric layer 2 are connected by full-needle tucks, and the latex yarns of the intermediate layer 3 tighten the first knitted fabric layer 1 and the second knitted fabric layer 2; the first knitted fabric layer 1 and the second knitted fabric layer 2 serve as electrode layers of the knitted fabric flexible capacitive sensor, and the intermediate layer 3 serves as a dielectric layer of the knitted fabric flexible capacitive sensor;

[0065] The thickness of the first knitted fabric layer 1 is 1.33 mm, the thickness of the second knitted fabric layer 2 is 1.33 mm, and the thickness of the intermediate layer 3 is 1.75 mm;

[0066] The knitted fabric flexible capacitive sensor has a gram weight of 297g / m 2 The horizontal density is 20.4 columns / inch and the vertical density is 16.3 rows / inch.

[0067] Knitted fabric flexible capacitive sensors can be used to detect tensile or compressive loads;

[0068] like Figure 4 As shown, under a tensile load, the surface areas of the first knitted fabric layer and the second knitted fabric layer in the knitted fabric flexible capacitive sensor change, and at the same time, the distance between the first knitted fabric layer and the second knitted fabric layer changes, causing the capacitance to change;

[0069] like Figure 3 As shown, under compression load, the distance between the first knitted fabric layer and the second knitted fabric layer in the knitted fabric flexible capacitive sensor changes, causing the capacitance to change;

[0070] The knitted fabric flexible capacitive sensor can withstand a tensile stress of 0.01~240N in the range of 50% tensile strain and a compressive stress of 0.1~2.3×10 5 The sensitivity of the knitted flexible capacitive sensor is 1.13; after 10,000 cycles of compression or stretching, the repeatability error δ R压缩 = 2.78%, δ R拉伸 = 2.59%, showing excellent cycle stability and dynamic durability;

[0071] After a knitted flexible capacitive sensor is cut into multiple capacitive sensors of the same shape, under the same tensile load or compressive load, the baseline capacitance values and sensitivities of the cut capacitive sensors are consistent.

[0072] Example 3

[0073] A knitted fabric flexible capacitive sensor is knitted using 75D / 40f Cu / PAN multifilament yarn (Cu mass fraction: 32.2%) as the conductive yarn and 115D TPU as the spacer yarn on a computerized flat knitting machine (machine gauge: 20). The first knitting pass is made of the Cu / PAN multifilament yarn, which is looped on the front needle bar. The second knitting pass is made of the Cu / PAN multifilament yarn, which is looped on the rear needle bar. The third and fourth knitting passes are made of the spacer yarn, which is tucked every other needle. These four knitting passes form a single course of fabric, i.e., each four knitting passes constitutes a knitting cycle. After weaving, the knitted fabric is hot-pressed at 180°C for 1 minute using a flat-bed hot press to melt the TPU into an elastic block material.

[0074] like Figure 2 As shown, the knitted fabric flexible capacitive sensor obtained after weaving and hot pressing includes a planar first knitted fabric layer 1, a planar second knitted fabric layer 2, and an intermediate layer 3; the first knitted fabric layer 1 and the second knitted fabric layer 2 are both made of Cu / PAN multifilaments strung together, and the intermediate layer 3 is woven from elastic yarn TPU. The first knitted fabric layer 1 and the second knitted fabric layer 2 are connected by spacer stitches, and the elastic yarn TPU in the intermediate layer 3 tightens the first knitted fabric layer 1 and the second knitted fabric layer 2; the first knitted fabric layer 1 and the second knitted fabric layer 2 serve as electrode layers of the knitted fabric flexible capacitive sensor, and the intermediate layer 3 serves as the dielectric layer of the knitted fabric flexible capacitive sensor;

[0075] The thickness of the first knitted fabric layer 1 is 1.21 mm, the thickness of the second knitted fabric layer 2 is 1.21 mm, and the thickness of the intermediate layer 3 is 1.85 mm;

[0076] The weight of the fabric flexible capacitive sensor is 249g / m 2 The horizontal density is 19.2 columns / inch and the vertical density is 20.3 rows / inch.

[0077] Knitted fabric flexible capacitive sensors can be used to detect tensile or compressive loads;

[0078] Under tensile load, the surface areas of the first knitted fabric layer and the second knitted fabric layer in the knitted fabric flexible capacitive sensor change, and at the same time, the distance between the first knitted fabric layer and the second knitted fabric layer changes, causing the capacitance to change;

[0079] Under compressive load, the distance between the first knitted fabric layer and the second knitted fabric layer in the knitted fabric flexible capacitive sensor changes, causing the capacitance to change;

[0080] The knitted fabric flexible capacitive sensor can withstand a tensile stress of 0.01~300N in the range of 50% tensile strain and a compressive stress of 0.1~2.37×10 5 The sensitivity range of the knitted fabric flexible capacitive sensor is 1.56; after 10,000 cycles of compression or stretching, the repeatability error δ R压缩 = 3.05%, δ R拉伸 = 2.87%, showing excellent cycle stability and dynamic durability;

[0081] After a knitted flexible capacitive sensor is cut into multiple capacitive sensors of the same shape, under the same tensile load or compressive load, the baseline capacitance values and sensitivities of the cut capacitive sensors are consistent.

[0082] Example 4

[0083] A knitted fabric flexible capacitive sensor is basically the same as Example 3, except that the spacer yarn is a 75D / 12f polyester / polyamide multifilament (mass ratio is 55:45).

[0084] like Figure 1 As shown, the knitted fabric flexible capacitive sensor obtained after weaving and hot pressing includes a planar first knitted fabric layer 1, a planar second knitted fabric layer 2, and an intermediate layer 3; the first knitted fabric layer 1 and the second knitted fabric layer 2 are both made of silver threads strung together, and the intermediate layer 3 is woven from polyester / polyamide multifilaments. The first knitted fabric layer 1 and the second knitted fabric layer 2 are connected by full-needle tucks, and the polyester / polyamide multifilaments of the intermediate layer 3 tighten the first knitted fabric layer 1 and the second knitted fabric layer 2; the first knitted fabric layer 1 and the second knitted fabric layer 2 serve as electrode layers of the knitted fabric flexible capacitive sensor, and the intermediate layer 3 serves as the dielectric layer of the knitted fabric flexible capacitive sensor;

[0085] The thickness of the first knitted fabric layer 1 is 1.42 mm, the thickness of the second knitted fabric layer 2 is 1.42 mm, and the thickness of the intermediate layer 3 is 1.29 mm;

[0086] The knitted fabric flexible capacitive sensor has a gram weight of 313 g / m 2 The horizontal density is 14.2 columns / inch and the vertical density is 12.3 rows / inch.

[0087] Knitted fabric flexible capacitive sensors can be used to detect tensile or compressive loads;

[0088] like Figure 4 As shown, under a tensile load, the surface areas of the first knitted fabric layer and the second knitted fabric layer in the knitted fabric flexible capacitive sensor change, and at the same time, the distance between the first knitted fabric layer and the second knitted fabric layer changes, causing the capacitance to change;

[0089] like Figure 3 As shown, under compression load, the distance between the first knitted fabric layer and the second knitted fabric layer in the knitted fabric flexible capacitive sensor changes, causing the capacitance to change;

[0090] The knitted fabric flexible capacitive sensor can withstand a tensile stress of 0.01~300N in the range of 50% tensile strain and a compressive stress of 0.1~3.4×10 5 The sensitivity of the knitted flexible capacitive sensor is 1.17; after 10,000 cycles of compression or stretching, the repeatability error δ R压缩 = 4.04%, δ R拉伸 = 3.87%, showing excellent cycle stability and dynamic durability;

[0091] After a knitted flexible capacitive sensor is cut into multiple capacitive sensors of the same shape, under the same tensile load or compressive load, the baseline capacitance values and sensitivities of the cut capacitive sensors are consistent.

Claims

1. A knitted fabric flexible capacitive sensor, characterized by: comprising a planar first knitted fabric layer, a planar second knitted fabric layer and an intermediate layer; The first knitted fabric layer and the second knitted fabric layer are connected to each other by weaving spacer yarns therebetween, the spacer yarns constituting the intermediate layer; The first knitted fabric layer and the second knitted fabric layer are both formed by mutually interlacing conductive yarns; The spacer yarn is an insulating elastic yarn, which connects the first knitted fabric layer and the second knitted fabric layer in the form of tuck loops. The insulating elastic yarn is a thermoplastic elastomer yarn. After the thermoplastic elastomer yarn is woven between the first knitted fabric layer and the second knitted fabric layer, the thermoplastic elastomer yarn is melted by heat pressing to form an elastomer block material. The knitted fabric flexible capacitive sensor can be used to detect tensile load or compressive load; Under a tensile load, the surface areas of the first knitted fabric layer and the second knitted fabric layer in the knitted fabric flexible capacitive sensor change, and simultaneously the distance between the first knitted fabric layer and the second knitted fabric layer changes, causing the capacitance to change; Under a compressive load, the distance between the first knitted fabric layer and the second knitted fabric layer in the knitted fabric flexible capacitive sensor changes, causing the capacitance to change.

2. The knitted fabric flexible capacitive sensor according to claim 1, characterized in that: The tuck stitches are full needle tuck stitches or every other needle tuck stitches.

3. The knitted fabric flexible capacitive sensor according to claim 1, characterized in that: The conductive yarn is one or more of metal-based conductive yarn, carbon-based conductive yarn and conductive polymer yarn.

4. The knitted fabric flexible capacitive sensor according to claim 1, characterized in that: The thermoplastic elastomer yarn is polyester thermoplastic elastomer, polystyrene thermoplastic elastomer, polyolefin thermoplastic elastomer, polyvinyl chloride thermoplastic elastomer, polyurethane thermoplastic elastomer, polyamide thermoplastic elastomer, polyorganofluorine thermoplastic elastomer, polyorganosilicone thermoplastic elastomer or mixed multifilaments thereof.

5. The knitted fabric flexible capacitive sensor according to claim 1, characterized in that: The linear density of the conductive yarn is 22 to 280 dtex, and the linear density of the insulating elastic yarn is 22 to 280 dtex; The thickness of the first knitted fabric layer is 1 to 3 mm, the thickness of the second knitted fabric layer is 1 to 3 mm, and the thickness of the middle layer is 1 to 3 mm.

6. The knitted fabric flexible capacitive sensor according to claim 1, characterized in that: The knitted fabric flexible capacitive sensor can withstand a tensile stress of 0.01 to 300 N within a 50% tensile strain range and a compressive stress of 0.1 to 4×10 5 Pa pressure.

7. The knitted fabric flexible capacitive sensor according to claim 1, characterized in that: The sensitivity range of the knitted fabric flexible capacitive sensor is 1 to 2; The calculation formula of sensitivity GF is as follows: Where C is the capacitance value after loading; C0 is the capacitance value in the initial state; ε is the strain; After one knitted fabric flexible capacitive sensor is cut into multiple capacitive sensors of the same shape, under the same tensile load or compressive load, the cut capacitive sensors have consistent baseline capacitance values and consistent sensitivities.

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