Resonant current sensor integrated with miniature magnet and acoustic resonator

Abstract

The invention belongs to the technical field of sensors, and particularly relates to a resonant current sensor integrated with a miniature magnet and an acoustic resonator. According to the miniature sensor integrated with the magnet, the current is measured by measuring the magnetic force borne by the magnet in a current magnetic field. The magnetic force borne by the permanent magnet is in direct proportion to the magnetic field gradient, so that an interfered uniform magnetic field (such as a geomagnetic field) emitted by the outside can be shielded. Secondly, according to the invention, the magnitude of the current is measured by measuring the offset of the resonant frequency based on the acoustic resonant measurement principle. Due to the characteristics of high Q value, high sensitivity and the like of the acoustic resonator, the produced sensor has the characteristics of high sensitivity, high precision, low-frequency noise resistance and the like, and is simple in structure and easy to measure. Compared with a traditional current sensor, the current sensor is much smaller in size and has certain advantages.

Description

Technical Field

[0001] The invention belongs to the technical field of sensors, and in particular relates to a resonant current sensor integrating a micro magnet and an acoustic resonator. Background Art

[0002] The current sensor is a key electronic component. Its core significance lies in its ability to accurately and in real time monitor current changes in circuit systems. By converting current into measurable and processable signals (such as voltage or digital signals), current sensors provide basic data for the protection, control and monitoring of electrical equipment. In electrical systems, current sensors play a vital role in ensuring safety, precise control and optimized management. In addition, current sensors also play an irreplaceable role in energy management, fault diagnosis and predictive maintenance.

[0003] Among them, non-contact current sensors are becoming more and more popular. They measure the magnitude of the current by detecting the magnetic field generated by the current. Since this method does not introduce additional resistance, it is widely used in current measurement. The current mainstream non-contact current sensors are Hall type, fluxgate type, magnetoresistance type, current mutual inductance type, and Rosenberger coil type. The Hall type and magnetoresistance type directly measure the magnetic field strength and output voltage and resistance signals, but have the limitations of low accuracy and susceptibility to interference from external magnetic fields, such as the geomagnetic field. Although the fluxgate type has higher accuracy, its peripheral circuit is complex and easily affected by the surrounding tiny magnetic field. Due to their principles, the current mutual inductance type and Rosenberger coil type need to be wound around the current to be measured, and the volume cannot be reduced, making the equipment larger. Summary of the invention

[0004] The object of the present invention is to provide a resonant current sensor integrating a micro magnet and an acoustic resonator. The resonant current sensor provided by the present invention is not affected by the external magnetic field and has the characteristics of high sensitivity, high precision and resistance to low-frequency noise.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a resonant current sensor, comprising:

[0007] A platform, wherein the platform is provided with a through hole;

[0008] A strain beam, wherein the strain beam is arranged on the inner surface of the through hole; the strain beam comprises a support platform area and a functional area; the strain beam comprises a silicon layer, a silicon dioxide layer and a lithium niobate film layer stacked in sequence from bottom to top, a circuit module is arranged on the lithium niobate film layer in the functional area, and the circuit module comprises an interdigital transducer; the area of ​​the circuit module is smaller than the area of ​​the functional area, and the area in the functional area corresponding to the circuit module does not include a silicon layer;

[0009] A micro permanent magnet, wherein the micro permanent magnet is disposed on the supporting platform area;

[0010] The platform and the strain beam are an integrated structure.

[0011] Preferably, the platform comprises a silicon layer, a silicon dioxide layer and a lithium niobate thin film layer stacked in sequence from bottom to top;

[0012] The silicon dioxide layer of the platform and the silicon dioxide layer of the strain beam are connected and have the same thickness;

[0013] The lithium niobate film layer of the platform and the lithium niobate film layer of the strain beam are connected and have the same thickness;

[0014] The silicon layer of the platform and the silicon layer of the strain beam are connected and have different thicknesses.

[0015] Preferably, the thickness of the silicon dioxide layer of the platform and the silicon dioxide layer of the strain beam are both 60nm to 1μm;

[0016] The thickness of the lithium niobate thin film layer of the platform and the lithium niobate thin film layer of the strain beam are both 300nm-1μm;

[0017] The thickness of the silicon layer of the platform is 250 μm to 600 μm; the thickness of the silicon layer of the strain beam is 5 to 30 μm.

[0018] Preferably, the lithium niobate thin film layer of the platform and the lithium niobate thin film layer of the strain beam both adopt a 41Y shear orientation;

[0019] The silicon layer of the platform and the silicon layer of the strain beam are both made of high-resistance silicon, and the resistance of the high-resistance silicon is greater than 1 kΩ·cm.

[0020] Preferably, the material of the IDT is aluminum, with a thickness of 100 nm to 400 nm; the spacing of the IDT is 2 μm to 10 μm, and the width is 2 μm to 10 μm; the number of pairs of the IDT is 5 to 100 pairs;

[0021] The circuit module also includes a first short-circuit reflective grid and a second short-circuit reflective grid; the first short-circuit reflective grid and the second short-circuit reflective grid are respectively located on both sides of the interdigital transducer; the first short-circuit reflective grid, the interdigital transducer, the second short-circuit reflective grid and the micro permanent magnet are located on the same central axis; the first short-circuit reflective grid and the second short-circuit reflective grid are both made of aluminum, and the thickness is 100nm to 400nm; the number of pairs of the first short-circuit reflective grid and the second short-circuit reflective grid is ≤100 pairs.

[0022] Preferably, the functional area is a trapezoidal structure, the upper base of the trapezoidal structure is connected to the supporting platform area, and the lower base of the trapezoidal structure is connected to the platform.

[0023] Preferably, busbar electrodes are further provided on both sides of the functional area; a circuit connection is formed between the busbar electrodes and the interdigital transducers; the busbar electrodes are made of aluminum with a thickness of 100 nm to 400 nm.

[0024] Preferably, a PAD component is further provided on the platform connected to the functional area; a circuit connection is formed between the PAD component and the interdigital transducer; the material of the PAD component is aluminum, and the thickness is 100nm to 400nm.

[0025] Preferably, a nickel layer is further provided between the lithium niobate film layer in the support platform area and the micro permanent magnet;

[0026] The size of the micro permanent magnet is (400-1000 μm)*(400-1000 μm)*(400-1000 μm).

[0027] The present invention also provides a method for preparing the resonant current sensor described in the above technical solution, comprising the following steps:

[0028] i. Providing an LNOI wafer, wherein the LNOI wafer comprises a lithium niobate layer, a silicon dioxide layer and a silicon layer stacked in sequence from top to bottom;

[0029] ii. On the lithium niobate layer, photolithography, evaporation and stripping are performed in sequence to obtain an interdigital transducer, a bus electrode, a PAD component, a first short-circuit reflector, a second short-circuit reflector and a nickel layer;

[0030] iii. using an IBE ion beam etcher to etch a portion of the lithium niobate layer and a portion of the silicon dioxide layer to obtain a release hole;

[0031] iv. depositing a silicon dioxide mask layer on the silicon layer using PECVD;

[0032] v. performing photolithography and ICP etching on the silicon dioxide mask layer in sequence to obtain a first mask layer;

[0033] vi~vii, performing a first deep silicon etching and a second deep silicon etching on the first mask layer in sequence to form a strain beam;

[0034] viii. using a micro needle syringe, drop-coating UV glue on the nickel layer;

[0035] ix. Place a micro permanent magnet on the UV glue and cure it to obtain the resonant current sensor.

[0036] The invention provides a resonant current sensor.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The micro sensor with integrated magnet proposed by the present invention measures the current by measuring the magnetic force exerted on the magnet in the current magnetic field. Since the magnetic force exerted on the permanent magnet is proportional to the magnetic field gradient, it can shield the interfering uniform magnetic field (such as the earth's magnetic field) emitted by the outside world. Secondly, the present invention utilizes the measurement principle of acoustic resonance to measure the magnitude of the current by measuring the offset of the resonant frequency. Due to the high Q value and high sensitivity of the acoustic resonator, the resulting sensor has the characteristics of high sensitivity, high precision, and resistance to low-frequency noise, and its structure is simple and easy to measure. And the volume is much smaller than that of traditional current sensors, which has certain advantages.

[0039] The present invention also provides a method for preparing the resonant current sensor described in the above technical solution. The entire device is produced by MEMS technology, and the preparation process of the MEMS sensor is compatible with the Si-based process; due to its small size, it not only greatly reduces the chip area and improves the integration, but also has a relatively low price in mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A top view of the actual object of the resonant current sensor provided by the present invention;

[0041] Figure 2 A top view of a schematic diagram of a resonant current sensor provided by the present invention;

[0042] Figure 3 A schematic flow chart of a method for preparing a resonant current sensor provided by the present invention;

[0043] Figure 4 This is a schematic diagram of the principle of current generating magnetism;

[0044] Figure 5 A three-dimensional diagram of the resonant current sensor provided by the present invention;

[0045] Figure 6 A schematic diagram of the bottom structure of the resonant current sensor provided by the present invention;

[0046] Figure 7 A schematic diagram of a sensor testing device provided by the present invention;

[0047] Figure 8 This is a test result diagram of the sensor obtained in Example 1;

[0048] Among them, 1-circuit module, 2-micro permanent magnet, 3-functional area, 12-interdigital transducer, 13-short-circuit reflective grid, 21-nickel layer, 31-PAD component. DETAILED DESCRIPTION

[0049] The present invention provides a resonant current sensor integrating a micro-magnet and an acoustic resonator, comprising:

[0050] A platform, wherein the platform is provided with a through hole;

[0051] A strain beam, wherein the strain beam is arranged on the inner surface of the through hole; the strain beam comprises a support platform area and a functional area; the strain beam comprises a silicon layer, a silicon dioxide layer and a lithium niobate film layer stacked in sequence from bottom to top, a circuit module is arranged on the lithium niobate film layer in the functional area, and the circuit module comprises an interdigital transducer; the area of ​​the circuit module is smaller than the area of ​​the functional area, and the area in the functional area corresponding to the circuit module does not include a silicon layer;

[0052] A micro permanent magnet, wherein the micro permanent magnet is disposed on the supporting platform area;

[0053] The platform and the strain beam are an integrated structure.

[0054] In the present invention, the platform preferably includes a silicon layer, a silicon dioxide layer and a lithium niobate thin film layer stacked in sequence from bottom to top.

[0055] In the present invention, the lithium niobate film layer of the platform is preferably connected to the lithium niobate film layer of the strain beam, and the thickness is preferably the same. In the present invention, the thickness of the lithium niobate film layer of the platform and the lithium niobate film layer of the strain beam are preferably 300nm to 1μm, specifically 400nm. In the present invention, the lithium niobate of the lithium niobate film layer of the platform and the lithium niobate film layer of the strain beam are preferably 41Y crystal orientation.

[0056] In the present invention, the silicon dioxide layer of the platform is preferably connected to the silicon dioxide layer of the strain beam, and the thickness is preferably the same. In the present invention, the thickness of the silicon dioxide layer of the platform and the silicon dioxide layer of the strain beam are preferably 60nm to 1μm, specifically 300nm.

[0057] In the present invention, the silicon layer of the platform is preferably connected to the silicon layer of the strain beam, and the thickness is preferably different; the thickness of the silicon layer of the platform is preferably greater than the thickness of the silicon layer of the strain beam. In the present invention, the thickness of the silicon layer of the platform is preferably 250μm to 600μm; the thickness of the silicon layer of the strain beam is preferably 5 to 30μm, and more preferably 10 to 30μm. In the present invention, the material of the silicon layer of the platform and the silicon layer of the strain beam is preferably high-resistance silicon, and the resistance of the high-resistance silicon is preferably greater than 1kΩ·cm.

[0058] In the present invention, the material of the interdigital transducer is preferably aluminum, and the thickness is preferably 100nm~400nm, specifically 200nm; the spacing of the interdigital transducer is preferably 2μm~10μm, specifically 4μm; the width is preferably 2μm~10μm, specifically 4μm; the number of pairs of the interdigital transducers is preferably 5~100 pairs, specifically 35 pairs.

[0059] In the present invention, the circuit module preferably also includes a first short-circuit reflective grid and a second short-circuit reflective grid; the first short-circuit reflective grid and the second short-circuit reflective grid are preferably located on both sides of the interdigital transducer respectively; the first short-circuit reflective grid, the interdigital transducer, the second short-circuit reflective grid and the micro permanent magnet are preferably located on the same central axis; the material of the first short-circuit reflective grid and the second short-circuit reflective grid are preferably aluminum, and the thickness is 100nm to 400nm, specifically 200nm; the number of pairs of the first short-circuit reflective grid and the second short-circuit reflective grid is preferably ≤100 pairs, specifically 50 pairs.

[0060] In the present invention, the functional area is preferably a trapezoidal structure, the upper base of the trapezoidal structure is preferably connected to the supporting platform area, and the lower base of the trapezoidal structure is preferably connected to the platform.

[0061] In the present invention, bus electrodes are preferably provided on both sides of the functional area; a circuit connection is preferably formed between the bus electrode and the interdigital transducer; the bus electrode is preferably made of aluminum, and the thickness is preferably 100nm to 400nm, specifically 200nm.

[0062] In the present invention, a PAD component is preferably provided on the platform connected to the functional area; a circuit connection is preferably formed between the PAD component and the interdigital transducer; the material of the PAD component is preferably aluminum, and the thickness is preferably 100nm to 400nm, specifically 200nm.

[0063] In the present invention, a nickel layer is preferably provided between the lithium niobate film layer in the support platform area and the micro permanent magnet; the present invention has no special limitation on the thickness of the nickel layer, and a thickness familiar to those skilled in the art may be adopted; the area of ​​the nickel layer is preferably the same as the area of ​​the micro permanent magnet; the nickel layer and the micro permanent magnet are preferably connected by UV glue; the size of the micro permanent magnet is preferably (400-1000μm)*(400-1000μm)*(400-1000μm), specifically 400μm*500μm*500μm.

[0064] In the specific use process, the test principle of the resonant sensor provided by the present invention is: the functional area forms a piezoelectric acoustic resonator, and by integrating a micro permanent magnet, the micro permanent magnet applies force to the piezoelectric acoustic resonator, thereby changing the wavelength and sound velocity of the resonator, and then changing the resonant frequency;

[0065] The details are as follows;

[0066] The acoustic resonator is deformed by the magnetic force between the micro permanent magnet and the magnetic field of the current to be measured; the magnetic field generated by the current to be measured is given by Formula 1 and Formula 2:

[0067]

[0068] Among them, B is the magnetic flux density, H is the magnetic field, μ0 is the vacuum permeability, r is the distance between the measured point and the center of the wire, i is the current to be measured, and a θ is the tangent unit vector.

[0069] The force on the micro permanent magnet in the magnetic field is calculated according to Formula 3;

[0070]

[0071] Among them, B m is the residual magnetism of the permanent magnet, H is the background magnetic field, F m is the magnitude of the magnetic force, which is proportional to the gradient of the magnetic field;

[0072] Under the action of magnetic force, a force is applied to the support platform area to cause elastic deformation. Since the support platform area and the functional area (i.e., the acoustic resonator) are connected to each other, the elastic deformation is coupled to the acoustic resonator, resulting in elastic deformation of the acoustic resonator.

[0073] Furthermore, the interdigital spacing of the interdigital transducer on the acoustic resonator changes due to elastic deformation, resulting in a change in the wavelength of the acoustic resonator. The lithium niobate film is affected by stress, and the speed of the sound wave in the lithium niobate film also changes. The resonant frequency of the resonator is determined by Formula 4;

[0074] λ=c / f Formula 4;

[0075] Among them, λ is the wavelength, f is the resonant frequency, and c is the speed of sound;

[0076] Finally, the resonant frequency of the acoustic resonator changes due to the magnetic field generated by the current.

[0077] The present invention also provides a method for preparing the resonant current sensor described in the above technical solution, comprising the following steps:

[0078] i. Providing an LNOI wafer, wherein the LNOI wafer comprises a lithium niobate layer, a silicon dioxide layer and a silicon layer stacked in sequence from top to bottom;

[0079] ii. On the lithium niobate layer, photolithography, evaporation and stripping are performed in sequence to obtain an interdigital transducer, a bus electrode, a PAD component, a first short-circuit reflector, a second short-circuit reflector and a nickel layer;

[0080] iii. using an IBE ion beam etcher to etch a portion of the lithium niobate layer and a portion of the silicon dioxide layer to obtain a release hole;

[0081] iv. depositing a silicon dioxide mask layer on the silicon layer using PECVD;

[0082] v. performing photolithography and ICP etching on the silicon dioxide mask layer in sequence to obtain a first mask layer;

[0083] vi~vii, performing a first deep silicon etching and a second deep silicon etching on the first mask layer in sequence to form a strain beam;

[0084] viii. using a micro needle syringe, drop-coating UV glue on the nickel layer;

[0085] ix. Place a micro permanent magnet on the UV glue and cure it to obtain the resonant current sensor.

[0086] In the present invention, after the first deep silicon etching, cleaning is preferably performed, and the cleaning is preferably performed using acetone, isopropanol and deionized water in sequence.

[0087] In the present invention, the remaining silicon dioxide mask layer on the platform can be retained or removed without affecting the use of the resonant current sensor.

[0088] The preparation method provided by the present invention has two characteristics. Characteristic 1: two layers of masks (a silicon oxide mask and a photoresist) are made on the back of the wafer, and two deep silicon etchings are used to make the acoustic resonator unit and the micro permanent magnet unit have different thicknesses to improve the quality factor of the resonator. Characteristic 2: a layer of nickel is deposited on the structure, and the attraction between the permanent magnet and the soft magnet is used to achieve self-alignment and self-assembly of the magnet.

[0089] Unless otherwise specified, the materials and equipment used in the present invention are all commercially available products in the art.

[0090] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0091] Example 1

[0092] according to Figure 1 Prepared according to the process shown;

[0093] The specific steps are:

[0094] i. Providing an LNOI wafer, wherein the LNOI wafer comprises a lithium niobate layer, a silicon dioxide layer and a silicon layer stacked in sequence from top to bottom; wherein the lithium niobate in the lithium niobate layer adopts a 41Y crystal orientation and has a thickness of 400 nm; and the thickness of the silicon dioxide layer is 300 nm;

[0095] ii. On the lithium niobate layer, photolithography, evaporation and stripping are performed in sequence to obtain an interdigital transducer, a bus electrode, a PAD component, a first short-circuit reflector, a second short-circuit reflector and a nickel layer;

[0096] iii. using an IBE ion beam etcher to etch a portion of the lithium niobate layer and a portion of the silicon dioxide layer to obtain a release hole;

[0097] iv. depositing a silicon dioxide mask layer on the silicon layer using PECVD;

[0098] v. performing photolithography and ICP etching on the silicon dioxide mask layer in sequence to obtain a first mask layer;

[0099] vi~vii, performing a first deep silicon etching on the first mask layer, cleaning with acetone, isopropyl alcohol and deionized water in sequence, and then performing a second deep silicon etching to form a strain beam;

[0100] viii. using a micro needle syringe, drop-coating UV glue on the nickel layer;

[0101] ix. placing a micro permanent magnet (with a size of 400 μm*500 μm*500 μm) on the UV glue and curing it to obtain the resonant current sensor;

[0102] The specific parameters of each unit in the obtained resonant current sensor are as follows:

[0103] The thickness of the silicon layer in the platform is 250 μm; the material of the PAD is aluminum, with a thickness of 200 nm;

[0104] In the functional area (i.e., the acoustic resonator), the first short-circuit reflector, the interdigital transducer, the second short-circuit reflector and the bus electrode are all made of aluminum, and the thickness is 200 nm; the interdigital transducer has a spacing of 4 μm and a width of 4 μm; the number of pairs of the interdigital transducers is 35; the number of pairs of the first short-circuit reflector and the second short-circuit reflector are both 50 pairs;

[0105] The thickness of the silicon layer in the support platform region is 30 μm.

[0106] Performance Testing

[0107] The performance of the resonant current sensor obtained in Example 1 was tested;

[0108] Figure 7 The test setup of the sensor is shown, where the resonant frequency of the device is obtained using a vector network analyzer (VNA).

[0109] Figure 8 (a) shows the impedance characteristics of the sensor, which is Figure 8 (b) The Q factor can be determined to be 1432. The coil electromagnet is used to provide the magnetic field to the sensor. By applying different currents, we measured the resonant frequency shift, as Figure 8 The final test results show that the sensitivity of the sensor is 325Hz / mA.

[0110] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A resonant current sensor integrating a micro magnet and an acoustic resonator, characterized in that: include: A platform, wherein the platform is provided with a through hole; A strain beam, wherein the strain beam is arranged on the inner surface of the through hole; the strain beam comprises a support platform area and a functional area; the strain beam comprises a silicon layer, a silicon dioxide layer and a lithium niobate film layer stacked in sequence from bottom to top, a circuit module is arranged on the lithium niobate film layer in the functional area, and the circuit module comprises an interdigital transducer; the area of ​​the circuit module is smaller than the area of ​​the functional area, and the area in the functional area corresponding to the circuit module does not include a silicon layer; A micro permanent magnet, wherein the micro permanent magnet is disposed on the supporting platform area; The platform and the strain beam are an integrated structure.

2. The resonant current sensor according to claim 1, characterized in that: The platform comprises a silicon layer, a silicon dioxide layer and a lithium niobate thin film layer stacked in sequence from bottom to top; The silicon dioxide layer of the platform and the silicon dioxide layer of the strain beam are connected and have the same thickness; The lithium niobate film layer of the platform and the lithium niobate film layer of the strain beam are connected and have the same thickness; The silicon layer of the platform and the silicon layer of the strain beam are connected and have different thicknesses.

3. The resonant current sensor according to claim 2, characterized in that: The thickness of the silicon dioxide layer of the platform and the silicon dioxide layer of the strain beam are both 60nm to 1μm; The thickness of the lithium niobate thin film layer of the platform and the lithium niobate thin film layer of the strain beam are both 300nm-1μm; The thickness of the silicon layer of the platform is 250 μm to 600 μm; the thickness of the silicon layer of the strain beam is 5 to 30 μm.

4. The resonant current sensor according to any one of claims 1 to 3, characterized in that: The lithium niobate thin film layer of the platform and the lithium niobate thin film layer of the strain beam both adopt a 41Y shear direction; The silicon layer of the platform and the silicon layer of the strain beam are both made of high-resistance silicon, and the resistance of the high-resistance silicon is greater than 1 kΩ·cm.

5. The resonant current sensor according to claim 1, characterized in that: The material of the interdigital transducer is aluminum, with a thickness of 100nm to 400nm; the spacing of the interdigital transducer is 2μm to 10μm, and the width is 2μm to 10μm; the number of pairs of the interdigital transducer is 5 to 100 pairs; The circuit module also includes a first short-circuit reflective grid and a second short-circuit reflective grid; the first short-circuit reflective grid and the second short-circuit reflective grid are respectively located on both sides of the interdigital transducer; the first short-circuit reflective grid, the interdigital transducer, the second short-circuit reflective grid and the micro permanent magnet are located on the same central axis; the first short-circuit reflective grid and the second short-circuit reflective grid are both made of aluminum, and the thickness is 100nm to 400nm; the number of pairs of the first short-circuit reflective grid and the second short-circuit reflective grid is ≤100 pairs.

6. The resonant current sensor according to claim 1, characterized in that: The functional area is a trapezoidal structure, the upper base of the trapezoidal structure is connected to the supporting platform area, and the lower base of the trapezoidal structure is connected to the platform.

7. The resonant current sensor according to claim 1 or 6, characterized in that: The two sides of the functional area are also provided with busbar electrodes; a circuit connection is formed between the busbar electrodes and the interdigital transducers; the busbar electrodes are made of aluminum with a thickness of 100nm to 400nm.

8. The resonant current sensor according to claim 1, characterized in that: A PAD component is also arranged on the platform connected to the functional area; a circuit connection is formed between the PAD component and the interdigital transducer; the material of the PAD component is aluminum, and the thickness is 100nm to 400nm.

9. The resonant current sensor according to claim 1, characterized in that: A nickel layer is also provided between the lithium niobate film layer in the support platform area and the micro permanent magnet; The size of the micro permanent magnet is (400-1000 μm)*(400-1000 μm)*(400-1000 μm).

10. The method for preparing the resonant current sensor according to any one of claims 1 to 9, characterized in that: The following steps are involved: i. Providing an LNOI wafer, wherein the LNOI wafer comprises a lithium niobate layer, a silicon dioxide layer and a silicon layer stacked in sequence from top to bottom; ii. On the lithium niobate layer, photolithography, evaporation and stripping are performed in sequence to obtain an interdigital transducer, a bus electrode, a PAD component, a first short-circuit reflector, a second short-circuit reflector and a nickel layer; iii. using an IBE ion beam etcher to etch a portion of the lithium niobate layer and a portion of the silicon dioxide layer to obtain a release hole; iv. depositing a silicon dioxide mask layer on the silicon layer using PECVD; v. performing photolithography and ICP etching on the silicon dioxide mask layer in sequence to obtain a first mask layer; vi~vii, performing a first deep silicon etching and a second deep silicon etching on the first mask layer in sequence to form a strain beam; viii. using a micro needle syringe, drop-coating UV glue on the nickel layer; ix. Place a micro permanent magnet on the UV glue and cure it to obtain the resonant current sensor.

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