Bridge type magnetoelectric composite magnetic sensor

Abstract

The invention relates to a bridge type magnetoelectric composite magnetic sensor. In the sensor, a PI layer is arranged on a buffer layer, and an excitation coil layer is bonded at each of the two ends of the upper surface of the PI layer; each excitation coil layer is covered with a lower electrode layer, each lower electrode layer is provided with a piezoelectric layer, the lower surface of the magnetostriction layer covers the two piezoelectric layers, and the projection of the magnetostriction layer coincides with the projection of the buffer layer; the upper surfaces of the two ends of the magnetostriction layer are each provided with a piezoelectric layer. The upper surfaces of the two piezoelectric layers are respectively covered with an upper electrode layer. Redundant lines are reduced and sensing signals are improved by adopting an integrated structure differential parallel connection mode, the signal-to-noise ratio is correspondingly improved by suppressing noise, the requirement of high-precision detection is further met, and the sensing capacity of the sensor to a magnetic field is enhanced by adopting a bridge type structure.

Description

Technical Field

[0001] The present invention combines magnetostrictive materials with piezoelectric materials and applies them to the field of electromagnetic sensing. It mainly involves iron-cobalt-vanadium strips with magnetostrictive effect and PZT-5H with piezoelectric effect. It can monitor magnetic field changes and convert them into electrical signals. Background Art

[0002] With the development of the information age, electronic communications technologies are becoming increasingly sophisticated. The worldwide application of the Internet of Things, in particular, requires various sensor devices to accurately detect the physical properties of different substances. Therefore, sensor applications in the 21st century are expected to become increasingly widespread. The emergence of microelectromechanical systems (MEMS) has significantly reduced the size of sensors, greatly improving their efficiency. Among various sensors, magnetic sensors are a diverse group. However, most magnetic sensors struggle to simultaneously meet the requirements of miniaturization, low power consumption, and high sensitivity at ultra-low frequencies. Magnetoelectric coupling sensors, on the other hand, offer the potential to reduce size and power consumption while maintaining high performance. In addition to energy harvesters, magnetoelectric coupling sensors can also be used for contactless positioning and navigation, such as detecting the Earth's magnetic field and even imaging the magnetic field within the brain. Magnetoelectric coupling sensors are often made of multiferroic materials, and research on multiferroic materials has had a profound impact on the development of magnetoelectric coupling sensors.

[0003] Among multiferroic materials, magnetoelectric materials represent a class with relatively mature research results and promising development prospects. They are essential for the manufacture of many components related to energy and information technology. However, despite their exceptional performance, traditional single-phase multiferroic materials struggle to achieve strong magnetoelectric coupling at room temperature. To address these challenges, researchers have turned their attention to multiferroic composites, formed by combining a ferroelectric phase with a strong piezoelectric effect and a ferromagnetic phase with a strong magnetostrictive effect. They have also begun exploring the design of different magnetoelectric composite structures to enhance the magnetoelectric coupling performance of these composites.

[0004] To improve sensor sensitivity, researchers primarily alter the magnetoelectric phase connection method. Kumar et al. [AS Kumar, CS C Lekha, S Vivek, et al. Multiferroic and magnetoelectric properties of Ba0.85Ca0.15Zr0.1Ti0.9O3-CoFe2O4 core-shell nanocomposite JL Journal of Magnetism & Magnetic Materials, 2016, 418: 294-299.] used a 0-3 connection method to embed 0-dimensional magnetic phase particles within a 3D ferroelectric bulk to enhance overall magnetoelectric coupling performance. However, the uneven distribution of ferrite particles within the ferroelectric dielectric induces internal conductive paths, which can lead to leakage current. Zhang et al. [Zhang, Y., et al., Dual-Mode Detection Method for UXO Targets by Measuring Magnetic Anomaly and Electromagnetic Response With FeNiMoSiB / PZT-5A Composite. IEEE Transactions on Geoscience and Remote Sensing, 2024. 62: pp. 1-11.] used a magnetoelectric composite material, using the magnetostrictive material FeNiMoSiB and the piezoelectric material PZT as the main components. They constructed a magnetic field detection sensor using a classic sandwich structure and differentially connected the two magnetoelectric composite units in parallel to suppress noise. However, the complex circuitry made sensor packaging difficult, resulting in a large device and poor signal accuracy.

[0005] In magnetoelectric composites, the magnetostrictive material strains in response to changes in the external magnetic field, causing the electric polarization of the piezoelectric material to change. Magnetic sensors based on magnetoelectric composites utilize the principle of magneto-elastic-electric coupling to convert external magnetic signals into output charge signals, thereby indirectly measuring magnetic field signals. These sensors play an important and strategic role in national defense security, industrial production, biomedicine, geological exploration, and other fields. However, because magnetoelectric sensors are susceptible to noise, such as intrinsic noise, environmental vibration, and external power frequency interference, the magnetic induction intensity generated by the target to be detected rapidly decays with increasing detection distance. In practical applications, the signals collected by magnetoelectric sensors typically have a low signal-to-noise ratio, making it difficult to distinguish the target magnetic signal from the noisy signal.

[0006] Patent CN116338536A describes a magnetoelectric sensing unit installed within an excitation coil. The sensing unit's output voltage is transmitted to a demodulation module, which then demodulates the target output voltage to generate a magnetic field signal containing information about the magnetic field to be measured, thereby enhancing magnetic sensing capabilities. However, the complex wiring of the sensing device makes the output signal susceptible to interference from the external environment. Summary of the Invention

[0007] The purpose of the present invention is to provide a bridge-type magnetoelectric composite magnetic sensor to address the limitations of current technology. The sensor unit includes a magnetostrictive layer, a piezoelectric layer, a PI layer, a PDMS layer, and upper and lower electrode layers. The surface of the piezoelectric layer is covered with electrodes. A differential parallel connection method is adopted. The upper electrode of the left piezoelectric layer and the upper electrode of the right piezoelectric layer are respectively led out as output terminals, and the lower electrode of the left piezoelectric layer and the lower electrode of the right piezoelectric layer are connected to the ground; a copper conductive coil layer is adhered to the PI layer; the PDMS layer is used as a buffer layer at the bottom of the sensor to improve the overall stability of the sensor. The present invention adopts an integrated structure of differential parallel connection to reduce redundant circuits and improve the sensing signal. By suppressing noise, the signal-to-noise ratio is also improved accordingly, thereby meeting the requirements of high-precision detection, and the bridge-type structure enhances the sensor's ability to perceive magnetic fields.

[0008] The technical solution adopted by the present invention to solve its technical problem is:

[0009] A bridge-type magnetoelectric composite magnetic sensor, comprising: a piezoelectric layer, a magnetostrictive layer, a PI layer, an excitation coil, an upper electrode layer, a lower electrode layer, and a buffer layer;

[0010] The buffer layer is provided with a PI layer, and an excitation coil layer is bonded to each end of the upper surface of the PI layer; each excitation coil layer is covered with a lower electrode layer, and each lower electrode layer is provided with a piezoelectric layer; the lower surface of the magnetostrictive layer is covered on the two piezoelectric layers, and the projection of the magnetostrictive layer coincides with the projection of the buffer layer; the upper surfaces of the two ends of the magnetostrictive layer are also provided with a piezoelectric layer; and the upper surfaces of the two piezoelectric layers are respectively covered with an upper electrode layer;

[0011] The magnetostrictive layer is made of Fe-Co-V material; the thickness of the magnetostrictive layer is 0.75 to 1 mm;

[0012] The piezoelectric layer is made of PZT-5H material and has a thickness of 0.8mm to 1mm.

[0013] The upper electrode layer and the lower electrode layer are both made of silver; the thickness is 0.03mm to 0.07mm;

[0014] The magnetostrictive layer is magnetized along the Y axis, and the piezoelectric layer is polarized along the Z axis;

[0015] The thickness of the PI layer is 0.1 mm to 0.2 mm;

[0016] The coil layer is made of copper with a thickness of 0.05 to 0.1 mm.

[0017] The material of the buffer layer is PDMS, and the thickness is 0.9mm to 2mm;

[0018] The two excitation coil layers embedded in the PI layer are identical and mirror-imaged relative to each other, and are copper conductive coils with a coil thickness of 0.1 mm.

[0019] The length of a single piezoelectric layer is 35-37.5% of the length of the magnetostrictive layer; the width of the piezoelectric layer is consistent with the width of the magnetostrictive layer;

[0020] The essential features of the present invention are:

[0021] Current technology uses a bridge-type magnetoelectric composite sensor, consisting of a magnetostrictive layer, a piezoelectric layer, an electrode layer, and a PI layer for magnetic sensing. Each layer is bonded together with epoxy resin, enabling the conversion between the three physical quantities of magnetoelasticity and electric field.

[0022] The present invention adopts a bridge-type structure, with four piezoelectric layers symmetrically distributed on the upper left and right sides and the lower upper and right sides of the magnetostrictive layer, and the PI layer of the bonding coil is adhered to the lower piezoelectric layer to facilitate dynamic excitation. PDMS is used as the sensor buffer layer and provides certain support for the sensor.

[0023] Its operating principle is as follows: a magnetic field is provided by a magnet. Driven by a dynamic excitation source, the magnetostrictive layer responds to the external magnetic field and expands and contracts. The resulting strain is transmitted to the piezoelectric layer, generating an electric potential difference, thereby propagating a magnetic signal. Unlike traditional ME composite structures, the bridge-type ME composite structure achieves mechanical coupling at the interface through an integrated differential structure, suppressing noise and improving the signal-to-noise ratio. The integrated design also reduces the sensor's size, enabling flexible and high-precision magnetic field detection.

[0024] Beneficial effects of the present invention:

[0025] 1. The present invention adopts a bridge-type magnetoelectric composite structure. The integrated design facilitates packaging, has a simple manufacturing process, and is low in cost. The excitation coil is attached to the PI layer and connected to the piezoelectric layer, making it easy to apply the excitation source.

[0026] 2. The magnetoelectric composite magnetic sensor of the present invention innovatively adopts an integrated differential structure. Through the symmetrical layout of dual magnetoelectric units and the coplanar electrode integrated design, it suppresses common-mode interference and thermal drift noise while reducing packaging complexity, thereby improving the signal-to-noise ratio by 3-8 times. It takes into account both miniaturization (volume reduction by 40%) and high precision, and is suitable for scenarios such as geomagnetic detection and biomedical microcurrent monitoring.

[0027] 3. The present invention adopts a bridge-type structure to enhance the strain transfer at the interface to improve the induction of the external magnetic field. The magnetoelectric composite magnetic sensor with the bridge-type structure has a sensitivity of 169.53mV / mOe to the external magnetic field, while the traditional sandwich structure has a sensitivity of only 91.5mV / mOe to the external magnetic field. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the principle of the core unit of magnetoelectric composite magnetic sensing;

[0029] Figure 2 Schematic diagram of the structure of the magneto-electric composite magnetic sensing unit;

[0030] Figure 3 This is a schematic diagram of the overall design of the magneto-electric composite magnetic sensor;

[0031] Figure 4 This is the plane design drawing of the magneto-electric composite magnetic sensor;

[0032] Figure 5 This is a partially enlarged schematic diagram of the magnetoelectric composite magnetic sensor;

[0033] Figure 6 This is the magnetization intensity distribution diagram of the magnetostrictive layer of the magnetoelectric composite magnetic sensor;

[0034] Figure 7 This is a schematic diagram showing how the output voltage of the magnetoelectric composite magnetic sensor changes with the intensity of the magnetic field;

[0035] Figure 8 Schematic diagram comparing the output voltage of the bridge structure and the traditional sandwich structure;

[0036] Among them, 1-permanent magnet; 2-piezoelectric layer; 3-magnetostrictive layer; 4-PI layer; 5-excitation coil layer; 6-buffer layer; 7-upper electrode layer; 8-lower electrode layer; DETAILED DESCRIPTION

[0037] Example 1:

[0038] The bridge-type magnetoelectric composite magnetic sensing core unit of the present invention is composed of a Fe-Co-V magnetostrictive layer, a PZT-5H piezoelectric layer, an upper electrode layer and a lower electrode layer. It uses the magnetostrictive effect of the Fe-Co-V magnetostrictive layer and the piezoelectric effect of the PZT-5H piezoelectric layer to achieve magnetic field induction. Figure 1As shown in the figure, under the stimulation of an external magnetic field, the Fe-Co-V magnetostrictive layer undergoes nonlinear expansion and contraction, generating strain that is transferred to the PZT-5H piezoelectric layer. A potential difference is generated between the upper and lower piezoelectric layers, and a differential parallel connection is used to connect the output terminals. As the external magnetic field changes, the output voltage also changes accordingly, converting the magnetic field signal into an electrical signal, thus achieving the conversion between the three physical quantities of "magnetic-elastic-electric".

[0039] The present invention will be further described in detail below with reference to the figures. This embodiment is only a specific description of the invention and is not to be regarded as limiting the scope of protection.

[0040] The bridge type magnetoelectric composite magnetic sensor of the present invention is as follows Figure 2 、 Figure 3 As shown, its composition includes: a PI layer 4 on a buffer layer 6, and an excitation coil layer 5 is bonded to each end of the upper surface of the PI layer 4; a lower electrode layer 8 is placed on each excitation coil layer 5, and a piezoelectric layer 2 is placed on each lower electrode layer 8; the lower surface of the magnetostrictive layer 3 covers the two piezoelectric layers 2, and the projection of the magnetostrictive layer 3 coincides with the projection of the buffer layer 6; there is also a piezoelectric layer 2 on each end of the upper surface of the magnetostrictive layer 3; the upper surfaces of the two piezoelectric layers 2 are each covered with an upper electrode layer 7;

[0041] The integrated differential structure is composed of a piezoelectric layer 2, an upper electrode layer 7, and a lower electrode layer 8. The output is drawn from the upper electrode layer 7 on the left and right sides of the upper part of the piezoelectric layer 2, and the lower electrode layer 8 on the left and right sides of the lower part of the piezoelectric layer 2 is grounded, forming a differential parallel structure.

[0042] The length of a single piezoelectric layer is 37.5% of the magnetostrictive layer; the width of the piezoelectric layer is consistent with the width of the magnetostrictive layer;

[0043] The thickness of the single layer of the electrode layers 7 and 8 is 10 to 100 microns, specifically 50 microns in this embodiment;

[0044] The thickness of the piezoelectric layer 2 is 0.8 mm to 1 mm, specifically 1 mm in this embodiment;

[0045] The thickness of the magnetostrictive layer 3 is 0.75 to 1 mm, specifically 0.8 mm in this embodiment;

[0046] The specific bridge-type magnetoelectric composite sensing structure is as follows: the four piezoelectric layers 2 are symmetrically distributed on the upper left and right sides and the lower left and right sides of the magnetostrictive layer 3, and the PI layer 4 bonded to the excitation coil layer 5 is adhered to the lower part of the piezoelectric layer 2 to facilitate dynamic excitation, and PDMS is used as the sensor buffer layer 6 to provide certain support for the sensor.

[0047] The magnetostrictive layer 3 is made of Fe-Co-V material; the piezoelectric layer 2 is made of PZT-5H material;

[0048] The magnetostrictive layer 3 is magnetized along the Y axis and is made of Fe-Co-V. It has a width of 12 mm, a length of 32 mm, a thickness of 1 mm, and is located at the geometric center.

[0049] The piezoelectric layer 2 is polarized along the Z axis and is made of PZT-5H with a width of 12 mm, a length of 12 mm, and a thickness of 0.8 mm.

[0050] The positive electrode 7 is made of conductive silver paste and silver; the thickness is 50 microns; the positive electrode covered on the upper surface of the piezoelectric layer 2 is 12 mm wide and 12 mm long;

[0051] The negative electrode 8 is made of conductive silver paste and silver; the thickness is 50 microns; the negative electrode covered on the lower surface of the piezoelectric layer 2 is 12 mm wide and 12 mm long;

[0052] The PI layer 4 is made of polyimide, with a width of 12 mm, a length of 12 mm, and a thickness of 0.1 mm;

[0053] The coil layer 5 is made of copper, has 3 turns, a wire diameter of 0.5 mm, and a cross-sectional area of 100 mm. 2 , thickness is 0.05mm;

[0054] The buffer layer 6 is made of PDMS, has a width of 12 mm, a length of 32 mm, and a thickness of 1 mm;

[0055] The preparation method of the bridge-type magnetoelectric composite magnetic sensing unit comprises the following steps:

[0056] The magnetostrictive layer 3 of the present invention is composed of a single layer of magnetostrictive material: from the Fe-Co-V strip, laser cutting is performed as follows: Figure 4For a single magnetostrictive layer with the dimensions shown on the long side, apply a sufficient amount of epoxy glue to filter paper and stir to mix thoroughly. Apply the epoxy glue to the single magnetostrictive layer using a clean toothpick. Using a brush soaked in silver, apply the epoxy glue to the upper surfaces of the two piezoelectric layers 2 above the magnetostrictive layer and the lower surfaces of the two piezoelectric layers 2 below the magnetostrictive layer, forming positive electrodes 7 and negative electrodes 8. Continue applying epoxy resin to the corresponding upper and lower surfaces of the four piezoelectric layers 2, bonding them to corresponding locations on the magnetostrictive layer 3. Press firmly, removing any excess epoxy glue from the surrounding area with a clean knife. Then, press the bonded magnetoelectric composite unit with a metal block for 10 minutes. Place the bonded unit in a vacuum bag and apply vacuum using a vacuum packer to rupture any bubbles within the epoxy glue, allowing the air inside the bubbles and the glue to escape. Press the device together using a non-magnetic flat copper block to further suppress bubbles and improve bonding. Finally, cure the device at room temperature for 24 hours. Thoroughly clean the two flexible PI substrates 4 to remove any impurities. Then, a thin layer of adhesive is applied to each substrate, and a copper conductive layer 5 is bonded to each of the two substrates through a lamination process. After the copper layer is in place, a circuit pattern is prepared using photolithography technology. A photoresist material is applied to the copper surface, exposed to ultraviolet light through a pattern mask, and the required circuit design is developed. The exposed copper is then etched away, leaving the circuit pattern. After etching, the remaining photoresist is peeled off, and the circuit is then cleaned. The PI layer 4 bonded to the coil layer 5 is adhered to the lower part of the piezoelectric layer 2, and finally a PDMS buffer layer 6 is pasted on the bottom layer of the unit. The overall sensor made in this embodiment is 3.2 mm thick.

[0057] The bridge-type magnetoelectric composite sensing unit in the example was simulated and modeled using COMSOL Multiphysics finite element simulation software, and a traditional sandwich structure with the same length and width as the bridge-type magnetoelectric composite sensing unit was modeled.

[0058] The software and protocols involved in the present invention are all known technologies.

[0059] Specifically, a finite element theoretical model of the magnetoelectric composite structure was constructed based on the COMSOL finite element software. The model couples the three physical field modules of "magnetic field", "electrostatics" and "solid mechanics". Among them, the piezoelectric effect is mainly realized by solid-state mechanics and electrostatic coupling, while the magnetostrictive effect is realized by coupling solid mechanics with the magnetic field. In solid mechanics, the state of the piezoelectric layer is set to "piezoelectric material", and electrostatics is set to "charge conservation, piezoelectric" state. The lower surface of the lower piezoelectric layer is set to ground. In solid mechanics, the magnetostrictive layer is set to "magnetostrictive material", and in the magnetic field, it is set to "Ampere's law, magnetostriction". In order to simulate the bridge-type magnetoelectric composite sensing unit sensing the magnetic field, a permanent magnet is set directly above the sensing unit. By changing the magnetic field intensity, the change in the output voltage of the sensing unit reflects the bridge-type magnetoelectric composite sensing unit's ability to sense the magnetic field.

[0060] Draw a spherical area as the air domain, and set the magnetic potential to zero at the spherical boundary of the air domain, that is, the magnetic lines of force will not pass through the air domain. Use the interior of the air domain as the calculation area to accurately simulate the magnetic field distribution. Set the shell current with an amplitude of 100mA, a frequency of 5kHz, and opposite polarity in the two coils, so that at any time, the direction of the excitation magnetic field generated inside the film is opposite in space. During the simulated deformation process, the two ends of the long axis of the sensing structure are set as fixed constraints. Set the permanent magnet directly above the sensing unit, and measure the magnetization intensity distribution of the magnetostrictive layer in the sensing structure, as shown below: Figure 6 As shown. The results show that the sensing unit converts the external magnetic field signal into a magnetic response in the magnetostrictive layer. Different magnetic field intensities were set under the permanent magnet, and the output voltage of the bridge structure and the sandwich structure was simulated and measured as a function of the magnetic field intensity and compared. The results show that the output voltage of the magnetoelectric sensing unit with the bridge structure is greater than that of the traditional sandwich structure under an external magnetic field of 0 to 1000A / m. It is worth noting that as the magnetic field increases, the rising slope of the curve gradually increases. This nonlinear response characteristic shows that the sensing unit has a significant amplification effect in a strong magnetic field environment, providing a physical basis for the accurate detection of equipment under complex magnetic field conditions. The sensitivity of the traditional sandwich structure to the external magnetic field is only 91.5mV / mOe, while the sensitivity of the bridge structure to the external magnetic field is 169.53mV / mOe, which is significantly higher than the traditional sandwich structure. This is equivalent to being able to identify more subtle magnetic field fluctuations in the same detection scenario. The bridge structure enhances the magnetoelectric composite sensor's ability to perceive the magnetic field. Figure 7 , as shown in 8.

[0061] Matters not covered by the present invention are known technologies.

Claims

1. A bridge-type magnetoelectric composite magnetic sensor, characterized by: The sensor is composed of: piezoelectric layer, magnetostrictive layer, PI layer, excitation coil, upper electrode layer, lower electrode layer, and buffer layer; Among them, the buffer layer is provided with a PI layer, and an excitation coil layer is bonded to both ends of the upper surface of the PI layer; each excitation coil layer is covered with a lower electrode layer, and each lower electrode layer is provided with a piezoelectric layer; the lower surface of the magnetostrictive layer is covered on the two piezoelectric layers, and the projection of the magnetostrictive layer coincides with the projection of the buffer layer; there is also a piezoelectric layer on each of the upper surfaces of the two ends of the magnetostrictive layer; the upper surfaces of the two piezoelectric layers are each covered with an upper electrode layer.

2. The bridge-type magnetoelectric composite magnetic sensor according to claim 1, wherein: The magnetostrictive layer is made of Fe-Co-V material; the thickness of the magnetostrictive layer is 0.75 to 1 mm; The piezoelectric layer is made of PZT-5H material and has a thickness of 0.8 mm to 1 mm.

3. The bridge-type magnetoelectric composite magnetic sensor according to claim 1, wherein: The magnetostrictive layer is magnetized along the Y axis, and the piezoelectric layer is polarized along the Z axis.

4. The bridge-type magnetoelectric composite magnetic sensor according to claim 1, wherein: The upper electrode layer and the lower electrode layer are both made of silver; the thickness is 0.03mm to 0.07mm; The thickness of the PI layer is 0.1 mm to 0.2 mm; The material of the buffer layer is PDMS, and the thickness is 0.9 mm to 2 mm.

5. The bridge-type magnetoelectric composite magnetic sensor according to claim 1, wherein: The two excitation coil layers embedded in the PI layer are completely identical and distributed in mirror image relative to each other. They are copper conductive coils with a coil thickness of 0.05 to 0.1 mm.

6. The bridge-type magnetoelectric composite magnetic sensor according to claim 1, wherein: The length of a single piezoelectric layer is 35-37.5% of the length of the magnetostrictive layer; and the width of the piezoelectric layer is consistent with the width of the magnetostrictive layer.

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