Symmetrical LC sensor and preparation method thereof, wireless passive flexible strain sensor and preparation method thereof

Abstract

The present invention discloses a symmetrical LC sensor, a wireless passive strain sensor, and methods for preparing the same. The wireless passive strain sensor includes two identical symmetrical LC sensors, one located in a measurement area and the other in a non-measurement area, wherein the symmetrical LC sensor includes a first inductance structure and a second inductance structure aligned vertically. The method for preparing the symmetrical LC sensor includes sequentially preparing the first inductance structure and the second inductance structure on a substrate to obtain a symmetrical LC sensor, and then combining the two symmetrical LC sensors into a wireless passive strain sensor. The symmetrical LC sensor of the present invention has a dual-inductance model, which can effectively enhance the sensitivity and resolution of the sensor and has advantages such as high sensitivity. The wireless passive strain sensor constructed using the symmetrical LC sensor also has advantages such as strong anti-interference ability and easy installation. It is a new type of flexible strain sensor with excellent performance and can be widely used in medical testing, wearable devices and other fields. It has high practical value and good application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of strain sensor manufacturing, and relates to a symmetrical LC sensor and a preparation method thereof, a wireless passive flexible strain sensor and a preparation method thereof. Background Art

[0002] Currently, flexible strain sensors that have the flexibility of human skin and can convert environmental changes into electrical signals have broad application prospects in fields such as medical testing and wearable devices. However, the reliance on electrical connections to transmit electrical signals by flexible sensors has limited their further application. Flexible strain sensors based on the LC resonance principle have advantages such as small size, long life, low power consumption, simple process, and simple signal processing. However, sensors based on the LC resonance principle have the disadvantage of low sensitivity. In addition, existing wireless passive sensors based on the LC resonance principle are resonant circuits composed of planar inductors and bipolar plate capacitors. Their resonant frequency is easily affected by changes in environmental factors such as temperature, humidity, and vibration, and their anti-interference ability is poor, which can easily adversely affect strain measurement. In addition, wireless passive sensors based on surface acoustic wave technology and radio frequency identification technology have complex preparation processes and expensive back-end processing circuits. Therefore, the development of a wireless passive flexible strain sensor with high sensitivity and strong anti-interference ability is of great significance for promoting the widespread application of flexible sensors in fields such as medical testing and wearable devices. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a symmetrical LC sensor with high sensitivity and a preparation method thereof, and also provide a wireless passive flexible strain sensor with high sensitivity and strong anti-interference ability and a preparation method thereof.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0005] A symmetrical LC sensor includes a first inductor structure and a second inductor structure aligned vertically. The first inductor structure includes a first inductor coil and a first capacitor plate, one end of the first inductor coil being electrically connected to the first capacitor plate. The second inductor structure includes a second inductor coil and a second capacitor plate, one end of the second inductor coil being electrically connected to the second capacitor plate. The first inductor coil and the second inductor coil are electrically connected at their other ends to form a dual inductor layer. A capacitor is formed between the first capacitor plate and the second capacitor plate. The dual inductor layer and the capacitor form a three-dimensional LC resonant circuit.

[0006] The above-mentioned symmetrical LC sensor is further improved in that the symmetrical LC sensor further includes a flexible substrate, and the first inductive structure is arranged on the flexible substrate; the material of the flexible substrate is polydimethylsiloxane or polyimide.

[0007] The above-mentioned symmetrical LC sensor is further improved, wherein the first inductor coil is formed by a first planar coil in a spiral manner; the number of turns of the first planar coil is 3 to 10 turns; the line width of the first planar coil is 1 mm to 10 mm; the first capacitor plate is polygonal, circular or elliptical; when the first capacitor plate is polygonal, the side length is 50 mm to 200 mm.

[0008] The above-mentioned symmetrical LC sensor is further improved, wherein the second inductor coil is formed by a second planar coil in a spiral manner; the number of turns of the second planar coil is 3 to 10 turns; the line width of the second planar coil is 1 mm to 10 mm; the second capacitor plate is polygonal, circular or elliptical; when the second capacitor plate is polygonal, the side length is 50 mm to 200 mm.

[0009] The above-mentioned symmetrical LC sensor is further improved, wherein the first inductor structure includes, from bottom to top, a first adhesion layer and a first metal functional layer; the first adhesion layer is provided on a substrate; the first adhesion layer is a Cr film, a Ti film or a Ni film; the thickness of the first adhesion layer is 10nm to 100nm; the first metal functional layer is an Al thin film; the thickness of the first metal functional layer is 500nm to 1000nm.

[0010] The above-mentioned symmetrical LC sensor is further improved, wherein the second inductor structure includes, from bottom to top, a second adhesion layer and a second metal functional layer; the second adhesion layer is a Cr film, a Ti film or a Ni film; the thickness of the second adhesion layer is 10nm to 100nm; the second metal functional layer is an Al thin film; the thickness of the second metal functional layer is 500nm to 1000nm.

[0011] The above symmetrical LC sensor is further improved in that the sides of the first metal functional layer and the second metal functional layer are electrically connected by silk-screen printing.

[0012] As a general technical concept, the present invention also provides a method for preparing the above-mentioned symmetrical LC sensor, comprising the following steps:

[0013] (1) providing a substrate;

[0014] (2) preparing a first inductor coil pattern and a first capacitor plate pattern on a substrate;

[0015] (3) depositing a first adhesion layer and a first metal functional layer on the substrate in sequence to form a first inductor structure;

[0016] (4) According to the operations of (2) and (3), a second adhesion layer and a second metal functional layer are prepared to form a second inductor structure;

[0017] (5) Aligning the first inductor structure and the second inductor structure, electrically connecting the first metal functional layer and the second metal functional layer, and completing the preparation of the symmetrical LC sensor.

[0018] The above-mentioned method for preparing a symmetrical LC sensor is further improved, in which in (2), a first inductor coil pattern and a first capacitor plate pattern are prepared on a substrate using a high-temperature tape; the high-temperature tape has a melting temperature resistance of above 200°C.

[0019] The above-mentioned method for preparing the symmetrical LC sensor is further improved, wherein in said (3), a first adhesion layer and a first metal functional layer are sequentially deposited on the substrate by a magnetron sputtering process or an ion beam sputtering process.

[0020] The above-mentioned method for preparing the symmetrical LC sensor is further improved, wherein in the above-mentioned (4), the first metal functional layer and the second metal functional layer are electrically connected by welding.

[0021] As a general technical concept, the present invention also provides a wireless passive flexible strain sensor comprising two identical symmetrical LC sensors. When in use, one of the symmetrical LC sensors is located in a measurement area, and the other symmetrical LC sensor is located in a non-measurement area. The distance between the two identical symmetrical LC sensors is ≥5 cm.

[0022] The symmetrical LC sensor includes a first inductor structure and a second inductor structure aligned vertically. The first inductor structure includes a first inductor coil and a first capacitor plate, one end of the first inductor coil being electrically connected to the first capacitor plate. The second inductor structure includes a second inductor coil and a second capacitor plate, one end of the second inductor coil being electrically connected to the second capacitor plate. The other ends of the first inductor coil and the second inductor coil are electrically connected to form a dual inductor layer. A capacitor is formed between the first capacitor plate and the second capacitor plate. The dual inductor layer and the capacitor form a three-dimensional LC resonant circuit.

[0023] The above-mentioned wireless passive flexible strain sensor is further improved in that the two identical symmetrical LC sensors are arranged on the same plane in the same manner; and the distance between the two identical symmetrical LC sensors is 5 cm to 30 cm.

[0024] The above-mentioned wireless passive flexible strain sensor is further improved, wherein the symmetrical LC sensor also includes a flexible substrate, and the first inductor structure is arranged on the flexible substrate; the material of the flexible substrate is polydimethylsiloxane or polyimide; and the flexible substrate is a long strip of 30mm×100mm×0.5mm.

[0025] The above-mentioned wireless passive flexible strain sensor is further improved, wherein the first inductor coil is composed of a first planar coil in a spiral manner; the number of turns of the first planar coil is 3 to 10 turns; the line width of the first planar coil is 1 mm to 10 mm; the first capacitor plate is polygonal, circular or elliptical; when the first capacitor plate is polygonal, the side length is 50 mm to 200 mm.

[0026] The above-mentioned wireless passive flexible strain sensor is further improved, wherein the second inductor coil is composed of a second planar coil in a spiral manner; the number of turns of the second planar coil is 3 to 10 turns; the line width of the second planar coil is 1 mm to 10 mm; the second capacitor plate is polygonal, circular or elliptical; when the second capacitor plate is polygonal, the side length is 50 mm to 200 mm.

[0027] The above-mentioned wireless passive flexible strain sensor is further improved, wherein the first inductive structure includes a first adhesion layer and a first metal functional layer from bottom to top; the first adhesion layer is arranged on a flexible substrate; the first adhesion layer is a Cr film, a Ti film or a Ni film; the thickness of the first adhesion layer is 10nm to 100nm; the first metal functional layer is an Al thin film; the thickness of the first metal functional layer is 500nm to 1000nm.

[0028] The above-mentioned wireless passive flexible strain sensor is further improved, wherein the second inductive structure includes a second adhesion layer and a second metal functional layer from bottom to top; the second adhesion layer is a Cr film, a Ti film or a Ni film; the thickness of the second adhesion layer is 10nm to 100nm; the second metal functional layer is an Al thin film; the thickness of the second metal functional layer is 500nm to 1000nm.

[0029] The above-mentioned wireless passive flexible strain sensor is further improved in that the sides of the first metal functional layer and the second metal functional layer are electrically connected by silk-screen printing.

[0030] As a general technical concept, the present invention also provides a method for preparing the above-mentioned wireless passive flexible strain sensor, including preparing a symmetrical LC sensor. The method for preparing the symmetrical LC sensor includes the following steps:

[0031] S1. providing a flexible substrate;

[0032] S2, preparing a first inductor coil pattern and a first capacitor plate pattern on a flexible substrate;

[0033] S3, sequentially depositing a first adhesion layer and a first metal functional layer on the flexible substrate to form a first inductor structure;

[0034] S4. According to the operations of S2 and S3, a second adhesion layer and a second metal functional layer are prepared to form a second inductor structure;

[0035] S5. Align the first inductor structure and the second inductor structure, and electrically connect the first metal functional layer and the second metal functional layer to complete the preparation of the symmetrical LC sensor.

[0036] The above-mentioned method for preparing the wireless passive flexible strain sensor is further improved. In S2, a first inductor coil pattern and a first capacitor plate pattern are prepared on the substrate using a high-temperature tape; the high-temperature tape has a melting temperature of above 200°C.

[0037] The above-mentioned method for preparing the wireless passive flexible strain sensor is further improved, wherein in S3, a first adhesion layer and a first metal functional layer are sequentially deposited on the substrate by a magnetron sputtering process or an ion beam sputtering process.

[0038] The above-mentioned method for preparing the wireless passive flexible strain sensor is further improved, wherein in S4, the first metal functional layer and the second metal functional layer are electrically connected by welding.

[0039] The above-mentioned method for preparing the wireless passive flexible strain sensor is further improved. In S4, after the preparation of the symmetrical LC sensor is completed, two symmetrical LC sensors are respectively arranged in the measurement area and the non-measurement area to obtain the wireless passive flexible strain sensor.

[0040] Compared with the prior art, the advantages of the present invention are:

[0041] (1) In view of the fact that existing LC sensors employ asymmetric methods and still suffer from defects such as low sensitivity, the present invention creatively proposes a symmetrical LC sensor comprising a first inductor structure and a second inductor structure aligned vertically. These two identical LC resonant structures are combined to form a three-dimensional LC resonant circuit, providing a dual-inductor model that can effectively enhance the sensitivity and resolution of the sensor. The symmetrical LC sensor of the present invention has advantages such as high sensitivity and is a novel sensor with excellent performance, high practical value, and promising application prospects.

[0042] (2) The present invention also provides a method for preparing a symmetrical LC sensor, which has the advantages of simple preparation, reliable process, low energy consumption, low cost, etc., is suitable for large-scale preparation, and is convenient for industrial utilization.

[0043] (3) In view of the fact that the existing wireless passive flexible sensors based on the LC resonance principle are difficult to overcome the adverse effects of the external environment on measurement, and still have defects such as low sensitivity and poor anti-interference ability, the present invention creatively proposes a wireless passive flexible strain sensor, including two identical symmetrical LC sensors. When in use, one symmetrical LC sensor is set in the measurement area and the other symmetrical LC sensor is set in the non-measurement area. The symmetrical LC sensor used includes a first inductance structure and a second inductance structure aligned up and down. These are two completely identical LC resonance structures. The two are combined to form a three-dimensional LC resonance circuit with a dual inductance model, which can effectively enhance the sensitivity and resolution of the sensor. At the same time, the sensor adopts a completely identical and independent dual LC resonance structure, one is set in the measurement area as a strain sensing LC device, and the other is set in the non-measurement area as a non-strain sensing LC device. By calculating the difference between the resonance frequency of the strain sensing LC device and the resonance frequency of the non-strain sensing LC device, the interference of the external environment on the measurement (such as physical quantities such as temperature and humidity) is eliminated, which is conducive to improving the anti-interference ability of the sensor. In addition, the dual LC resonance structure of the sensor of the present invention can eliminate the through-hole electrical connection and simplify the preparation process. Furthermore, the two identical, symmetrical LC sensors employed in the present invention can be installed either integrally or separately. Through simple calibration, the strain-sensitive LC sensor and the non-strain-sensitive LC sensor can be independently installed, unconstrained by sensor size. Therefore, the wireless passive flexible strain sensor of the present invention offers advantages such as high sensitivity, strong anti-interference capabilities, and ease of installation. It is a novel, high-performance flexible strain sensor with broad application potential in fields such as medical testing and wearable devices, boasting high value and promising prospects.

[0044] (4) In the wireless passive flexible strain sensor of the present invention, two identical symmetrical LC sensors can share a flexible substrate, and the two identical symmetrical LC sensors can be arranged on the same plane in the same manner. This simplifies the process, and the same deposition method ensures consistency. Furthermore, no insulating layer is required between the first inductor structure and the flexible substrate, which is more conducive to maintaining the heterogeneity of the dielectric constant of the dual LC resonant structure. Furthermore, in the present invention, by ensuring that the distance between the two identical symmetrical LC sensors is ≥5 cm, and particularly, the distance between the two is 5 cm to 30 cm, crosstalk between the two sensors can be further avoided while ensuring equivalent transferred inductance, thereby facilitating the production of a sensor with enhanced anti-interference capabilities.

[0045] (5) The present invention also provides a method for preparing a wireless passive flexible strain sensor, including preparing a symmetrical LC sensor and combining two identical symmetrical LC sensors to form a sensor with a dual LC resonant structure. The method has the advantages of simple preparation, reliable process, low energy consumption, and low cost, and is suitable for large-scale preparation and convenient for industrial use. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0047] Figure 1 Schematic diagram of the structure of the second inductor structure in the symmetrical LC sensor of the present invention.

[0048] Figure 2 Schematic diagram of the structure of the wireless passive flexible strain sensor in the present invention.

[0049] Legend:

[0050] 1. Flexible substrate; 2. Second inductor coil; 3. Second capacitor plate; a. Symmetrical LC sensor. DETAILED DESCRIPTION

[0051] The present invention will be further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the scope of protection of the present invention is not limited thereby.

[0052] Example 1

[0053] To address the low sensitivity and other shortcomings of existing LC sensors, the present invention innovatively proposes a symmetrical LC sensor. This sensor comprises a first inductor structure and a second inductor structure aligned vertically. These two identical LC resonant structures combine to form a three-dimensional LC resonant circuit, creating a dual-inductor model that effectively enhances the sensor's sensitivity and resolution. This symmetrical LC sensor boasts advantages such as high sensitivity, making it a novel sensor with excellent performance, high practical value, and promising application prospects.

[0054] In order to better understand the innovation of the technical solution of the present invention, as one of the examples in the technical solution of the present invention, Figure 1 and Figure 2As shown, the symmetrical LC sensor a involved includes a first inductance structure and a second inductance structure aligned vertically. The first inductance structure includes a first inductance coil and a first capacitor plate, one end of the first inductance coil is electrically connected to the first capacitor plate, and the second inductance structure includes a second inductance coil 2 and a second capacitor plate 3, one end of the second inductance coil is electrically connected to the second capacitor plate, and the other ends of the first inductance coil and the second inductance coil are electrically connected to form a double inductance layer. A capacitor is formed between the first capacitor plate and the second capacitor plate, and the double inductance layer and the capacitor form a three-dimensional LC resonant circuit.

[0055] In this embodiment, the symmetrical LC sensor further includes a flexible substrate 1 , and the first inductive structure is disposed on the flexible substrate, wherein the flexible substrate is a polydimethylsiloxane (PDMS) film.

[0056] In this embodiment, the first inductor coil is formed by a first planar coil in a spiral manner. The number of turns of the first planar coil is 5, the line width of the first planar coil is 3 mm, and the first capacitor plate is a rectangle with a side length of 100 mm.

[0057] In this embodiment, the second inductor coil is formed by a second planar coil in a spiral manner. The number of turns of the second planar coil is 5, the line width of the second planar coil is 3 mm, and the second capacitor plate is a square with a side length of 100 mm.

[0058] In this embodiment, the first inductor structure includes, from bottom to top, a first adhesion layer and a first metal functional layer. The first adhesion layer is provided on the substrate, wherein the first adhesion layer is a Cr film with a thickness of 100 nm; the first metal functional layer is an Al film with a thickness of 1000 nm.

[0059] In this embodiment, the second inductor structure includes a second adhesion layer and a second metal functional layer from bottom to top, wherein the second adhesion layer is a Cr film with a thickness of 100 nm; the second metal functional layer is an Al film with a thickness of 1000 nm.

[0060] In this embodiment, the sides of the first metal functional layer and the second metal functional layer are electrically connected by silk-screen printing.

[0061] Furthermore, a method for preparing the symmetrical LC sensor in the embodiment is provided, comprising the following steps:

[0062] (1) Providing a substrate, specifically: using a polydimethylsiloxane (PDMS) film as a flexible substrate, cutting it into strips with a width × length × thickness of 30 mm × 100 mm × 0.5 mm.

[0063] (2) Using a laser cutting machine, a high-temperature tape (commercially available conventional tape with a melting temperature of above 200°C) with a width of 30 mm and a length of 100 mm is cut to form a planar inductor pattern and a capacitor mask pattern. The planar inductor pattern and capacitor mask pattern made of the above-mentioned high-temperature tape are attached to the substrate to form a first inductor coil pattern and a first capacitor plate pattern.

[0064] (3) A first adhesion layer and a first metal functional layer are sequentially deposited on the substrate using a magnetron sputtering process, wherein the first adhesion layer is a Cr film with a thickness of 100 nm, and the first metal functional layer is an Al film with a thickness of 1000 nm, thereby forming a first inductor structure.

[0065] (4) According to the operations of (2) and (3), a second adhesion layer and a second metal functional layer are prepared to form a second inductor structure.

[0066] (5) Aligning the first inductor structure and the second inductor structure, electrically connecting the first metal functional layer and the second metal functional layer by soldering, thereby obtaining a symmetrical LC sensor.

[0067] Tests have shown that the symmetrical LC sensor prepared in this embodiment has higher sensitivity and resolution than conventional asymmetrical LC sensors, and is a new type of sensor with better performance.

[0068] Example 2

[0069] To address the difficulties existing wireless passive flexible sensors based on the LC resonance principle face in overcoming the adverse effects of the external environment on measurement, and to address the remaining shortcomings of low sensitivity and poor anti-interference capabilities, the present invention creatively proposes a wireless passive flexible strain sensor comprising two identical symmetrical LC sensors. During use, one symmetrical LC sensor is located in the measurement area, and the other symmetrical LC sensor is located in the non-measurement area. The symmetrical LC sensors comprise a first inductor structure and a second inductor structure aligned vertically. These two identical LC resonant structures, when combined, form a three-dimensional LC resonant circuit, creating a dual-inductance model that effectively enhances the sensor's sensitivity and resolution. Furthermore, the sensor employs identical and independent dual LC resonant structures, one located in the measurement area as a strain-sensing LC device and the other located in the non-measurement area as a non-strain-sensing LC device. By differentially calculating the resonances of the strain-sensing LC device and the non-strain-sensing LC device, interference from the external environment (such as temperature, humidity, and other physical quantities) is eliminated, thereby improving the sensor's anti-interference capabilities. Furthermore, the dual LC resonant structure of the present sensor eliminates the need for through-hole electrical connections, simplifying the manufacturing process. Furthermore, the two identical, symmetrical LC sensors employed in the present invention can be installed either integrally or separately. Through simple calibration, the strain-sensitive LC sensor and the non-strain-sensitive LC sensor can be independently installed, unconstrained by sensor size. Therefore, the wireless passive flexible strain sensor of the present invention offers advantages such as high sensitivity, strong anti-interference capabilities, and ease of installation. It is a novel, high-performance flexible strain sensor with broad application potential in fields such as medical testing and wearable devices, boasting high value and promising prospects.

[0070] In order to better understand the innovation of the technical solution of the present invention, as one of the examples in the technical solution of the present invention, Figure 2 As shown, the wireless passive flexible strain sensor includes two identical symmetrical LC sensors a. When in use, one symmetrical LC sensor is arranged in a measuring area, and the other symmetrical LC sensor is arranged in a non-measuring area.

[0071] In this embodiment, two identical symmetrical LC sensors are arranged on the same plane in the same manner, ie, on a flexible substrate on the same plane, and the distance between the two identical symmetrical LC sensors is 10 cm.

[0072] In this embodiment, the symmetrical LC sensor includes a first inductor structure and a second inductor structure aligned vertically. The first inductor structure includes a first inductor coil and a first capacitor plate, one end of the first inductor coil is electrically connected to the first capacitor plate, and the second inductor structure includes a second inductor coil 2 and a second capacitor plate 3. One end of the second inductor coil is electrically connected to the second capacitor plate, and the other ends of the first inductor coil and the second inductor coil are electrically connected to form a dual inductor layer. A capacitor is formed between the first capacitor plate and the second capacitor plate, and the dual inductor layer and the capacitor form a three-dimensional LC resonant circuit.

[0073] In this embodiment, the symmetrical LC sensor also includes a flexible substrate 1, and the first inductive structure is arranged on the flexible substrate, wherein the flexible substrate is a polydimethylsiloxane (PDMS) film, which is a long strip of 30mm×100mm×0.5mm, that is, two symmetrical LC sensors are located at both ends of the same flexible substrate.

[0074] In this embodiment, the first inductor coil is formed by a first planar coil in a spiral manner. The number of turns of the first planar coil is 5, the line width of the first planar coil is 30 mm, and the first capacitor plate is a square with a side length of 100 mm.

[0075] In this embodiment, the second inductor coil is formed by a second planar coil in a spiral manner. The number of turns of the second planar coil is 5, the line width of the second planar coil is 3 mm, and the second capacitor plate is a square with a side length of 100 mm.

[0076] In this embodiment, the first inductor structure includes, from bottom to top, a first adhesion layer and a first metal functional layer. The first adhesion layer is provided on the substrate, wherein the first adhesion layer is a Cr film with a thickness of 100 nm; the first metal functional layer is an Al film with a thickness of 1000 nm.

[0077] In this embodiment, the second inductor structure includes a second adhesion layer and a second metal functional layer from bottom to top, wherein the second adhesion layer is a Cr film with a thickness of 100 nm; the second metal functional layer is an Al film with a thickness of 1000 nm.

[0078] In this embodiment, the sides of the first metal functional layer and the second metal functional layer are electrically connected by silk-screen printing.

[0079] Furthermore, a method for preparing the wireless passive flexible strain sensor in the above embodiment is provided, which includes preparing a symmetrical LC sensor. The method for preparing the symmetrical LC sensor includes the following steps:

[0080] (1) Providing a substrate, specifically: using a polydimethylsiloxane (PDMS) film as a flexible substrate, cutting it into strips with a width × length × thickness of 30 mm × 100 mm × 0.5 mm.

[0081] (2) Using a laser cutting machine, a high-temperature tape (commercially available conventional tape with a melting temperature of above 200°C) with a width of 30 mm × 100 mm is cut to form a planar inductor pattern and a capacitor mask pattern. The planar inductor pattern and capacitor mask pattern made of the above-mentioned high-temperature tape are attached to the substrate to form a first inductor coil pattern and a first capacitor plate pattern.

[0082] (3) A first adhesion layer and a first metal functional layer are sequentially deposited on the substrate using a magnetron sputtering process, wherein the first adhesion layer is a Cr film with a thickness of 100 nm, and the first metal functional layer is an Al film with a thickness of 1000 nm, thereby forming a first inductor structure.

[0083] (4) According to the operations of (2) and (3), a second adhesion layer and a second metal functional layer are prepared to form a second inductor structure.

[0084] (5) Aligning the first inductor structure and the second inductor structure, electrically connecting the first metal functional layer and the second metal functional layer by soldering, thereby obtaining a symmetrical LC sensor.

[0085] According to the same method, an identical symmetrical LC sensor was prepared at the other end of the flexible substrate, and the distance between the two symmetrical LC sensors was set to 10 cm to obtain a wireless passive flexible strain sensor.

[0086] After testing: compared with the existing conventional wireless passive flexible strain sensor (asymmetric LC sensor), the wireless passive flexible strain sensor prepared in this embodiment has higher sensitivity, stronger anti-interference ability, and is easier to install. It is a new type of flexible strain sensor with better performance.

[0087] From the above results, it can be seen that the wireless passive flexible strain sensor of the present invention includes two identical symmetrical LC sensors, wherein the symmetrical LC sensors adopted have a dual inductance model, which can effectively enhance the sensitivity and resolution of the sensor. At the same time, the use of a completely identical and independent dual LC resonant structure eliminates interference from the external environment on the measurement (such as physical quantities such as temperature and humidity), which is conducive to improving the anti-interference ability of the sensor. It has the advantages of high sensitivity, strong anti-interference ability, and easy installation. It is a new type of flexible strain sensor with excellent performance and can be widely used in medical testing, wearable devices and other fields. It has high use value and good application prospects.

[0088] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions that fall within the scope of protection of the present invention are within the scope of protection of the present invention. It should be noted that improvements and modifications that can be made by a person skilled in the art without departing from the principles of the present invention are also considered to be within the scope of protection of the present invention.

Claims

1. A symmetrical LC sensor, characterized in that The symmetrical LC sensor includes a first inductor structure and a second inductor structure aligned vertically; the first inductor structure includes a first inductor coil and a first capacitor plate, one end of the first inductor coil is electrically connected to the first capacitor plate; the second inductor structure includes a second inductor coil and a second capacitor plate, one end of the second inductor coil is electrically connected to the second capacitor plate; the first inductor coil and the second inductor coil are electrically connected at the other end to form a double inductor layer; a capacitor is formed between the first capacitor plate and the second capacitor plate; the double inductor layer and the capacitor form a three-dimensional LC resonant circuit; the first inductor structure includes, from bottom to top, a first adhesion layer and a first metal functional layer; the first An adhesion layer is provided on a substrate; the first adhesion layer is a Cr film, a Ti film or a Ni film; the thickness of the first adhesion layer is 10nm to 100nm; the first metal functional layer is an Al thin film; the thickness of the first metal functional layer is 500nm to 1000nm; the second inductor structure includes, from bottom to top, a second adhesion layer and a second metal functional layer; the second adhesion layer is a Cr film, a Ti film or a Ni film; the thickness of the second adhesion layer is 10nm to 100nm; the second metal functional layer is an Al thin film; the thickness of the second metal functional layer is 500nm to 1000nm; the sides of the first metal functional layer and the second metal functional layer are electrically connected by silk-screen printing.

2. The symmetrical LC sensor according to claim 1, characterized in that The symmetrical LC sensor further includes a flexible substrate, and the first inductive structure is arranged on the flexible substrate; the material of the flexible substrate is polydimethylsiloxane or polyimide.

3. The symmetrical LC sensor according to claim 1 or 2, characterized in that The first inductor coil is formed by a first planar coil in a spiral manner; the number of turns of the first planar coil is 3 to 10; the line width of the first planar coil is 1 mm to 10 mm; the first capacitor plate is polygonal, circular or elliptical; when the first capacitor plate is polygonal, the side length is 50 mm to 200 mm; The second inductor coil is composed of a second planar coil in a spiral manner; the number of turns of the second planar coil is 3 to 10; the line width of the second planar coil is 1 mm to 10 mm; the second capacitor plate is polygonal, circular or elliptical; when the second capacitor plate is polygonal, the side length is 50 mm to 200 mm.

4. A method for preparing a symmetrical LC sensor according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Providing a substrate; (2) preparing a first inductor coil pattern and a first capacitor plate pattern on a substrate; (3) depositing a first adhesion layer and a first metal functional layer on the substrate in sequence to form a first inductor structure; (4) According to the operations of (2) and (3), a second adhesion layer and a second metal functional layer are prepared to form a second inductor structure; (5) Aligning the first inductor structure and the second inductor structure, electrically connecting the first metal functional layer and the second metal functional layer, and completing the preparation of the symmetrical LC sensor.

5. The method for preparing a symmetrical LC sensor according to claim 4, characterized in that: In (2), a first inductor coil pattern and a first capacitor plate pattern are prepared on a substrate using a high-temperature adhesive tape; the high-temperature adhesive tape has a melting temperature of above 200°C; In (3), a first adhesion layer and a first metal functional layer are sequentially deposited on the substrate using a magnetron sputtering process or an ion beam sputtering process; In the above (4), the first metal functional layer and the second metal functional layer are electrically connected by welding.

6. A wireless passive flexible strain sensor, characterized in that: The device comprises two identical symmetrical LC sensors. When in use, one of the symmetrical LC sensors is located in a measuring area, and the other symmetrical LC sensor is located in a non-measuring area. The distance between the two identical symmetrical LC sensors is ≥5 cm. The symmetrical LC sensor includes a first inductor structure and a second inductor structure aligned vertically; the first inductor structure includes a first inductor coil and a first capacitor plate, one end of the first inductor coil is electrically connected to the first capacitor plate; the second inductor structure includes a second inductor coil and a second capacitor plate, one end of the second inductor coil is electrically connected to the second capacitor plate; the other ends of the first inductor coil and the second inductor coil are electrically connected to form a double inductor layer; a capacitor is formed between the first capacitor plate and the second capacitor plate; the double inductor layer and the capacitor form a three-dimensional LC resonant circuit; the first inductor structure includes a first adhesive layer and a first metal functional layer from bottom to top; the first adhesive layer is electrically connected to the first capacitor plate ... The adhesion layer is arranged on the substrate; the first adhesion layer is a Cr film, a Ti film or a Ni film; the thickness of the first adhesion layer is 10nm to 100nm; the first metal functional layer is an Al thin film; the thickness of the first metal functional layer is 500nm to 1000nm; the second inductor structure includes a second adhesion layer and a second metal functional layer from bottom to top; the second adhesion layer is a Cr film, a Ti film or a Ni film; the thickness of the second adhesion layer is 10nm to 100nm; the second metal functional layer is an Al thin film; the thickness of the second metal functional layer is 500nm to 1000nm; the sides of the first metal functional layer and the second metal functional layer are electrically connected by silk screen printing.

7. The wireless passive flexible strain sensor according to claim 6, characterized in that: The two identical symmetrical LC sensors are arranged on the same plane in the same manner; the distance between the two identical symmetrical LC sensors is 5 cm to 30 cm.

8. The wireless passive flexible strain sensor according to claim 6 or 7, characterized in that: The symmetrical LC sensor further includes a flexible substrate, and the first inductive structure is disposed on the flexible substrate; the material of the flexible substrate is polydimethylsiloxane or polyimide; the flexible substrate is a strip of 30 mm×100 mm×0.5 mm; The first inductor coil is formed by a first planar coil in a spiral manner; the number of turns of the first planar coil is 3 to 10; the line width of the first planar coil is 1 mm to 10 mm; the first capacitor plate is polygonal, circular or elliptical; when the first capacitor plate is polygonal, the side length is 50 mm to 200 mm; The second inductor coil is composed of a second planar coil in a spiral manner; the number of turns of the second planar coil is 3 to 10; the line width of the second planar coil is 1 mm to 10 mm; the second capacitor plate is polygonal, circular or elliptical; when the second capacitor plate is polygonal, the side length is 50 mm to 200 mm.

9. A method for preparing a wireless passive flexible strain sensor according to any one of claims 6 to 8, characterized in that: The method comprises preparing a symmetrical LC sensor, wherein the method comprises the following steps: S1. providing a flexible substrate; S2, preparing a first inductor coil pattern and a first capacitor plate pattern on a flexible substrate; S3, sequentially depositing a first adhesion layer and a first metal functional layer on the flexible substrate to form a first inductor structure; S4. According to the operations of S2 and S3, a second adhesion layer and a second metal functional layer are prepared to form a second inductor structure; S5. Align the first inductor structure and the second inductor structure, and electrically connect the first metal functional layer and the second metal functional layer to complete the preparation of the symmetrical LC sensor.

10. The method for preparing a wireless passive flexible strain sensor according to claim 9, characterized in that: In S2, a first inductor coil pattern and a first capacitor plate pattern are formed on a substrate using a high-temperature tape having a melting temperature of above 200° C.; In S3, a first adhesion layer and a first metal functional layer are sequentially deposited on the substrate using a magnetron sputtering process or an ion beam sputtering process; In S4, the first metal functional layer and the second metal functional layer are electrically connected by welding; In the above S4, after the preparation of the symmetrical LC sensor is completed, two symmetrical LC sensors are respectively arranged in the measurement area and the non-measurement area to obtain a wireless passive flexible strain sensor.

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