A flexible magnetostrictive material patch, a preparation method thereof and a detection device

Abstract

The application provides a flexible magnetostrictive material patch, a preparation method thereof and a detection device. The flexible magnetostrictive material patch comprises, from bottom to top, a flexible base layer, an intermediate functional layer and a flexible packaging layer in sequence. The flexible base layer comprises, from bottom to top, a PET film and Ecoflex silicone rubber. The intermediate functional layer comprises magnetostrictive material powder and polyether polyurethane elastomer. The flexible packaging layer comprises a high-modulus elastic polymer material and hydrophobic modified fumed silica. The flexible magnetostrictive material patch has high sensitivity, high linearity, good flexibility and environmental stability, and is suitable for complex curved surface and weak pressure monitoring scenes.

Description

Technical Field

[0001] This invention relates to the fields of flexible sensors, magnetic functional materials and their preparation technology, and in particular to a flexible magnetostrictive material patch, its preparation method and detection device. Background Technology

[0002] As an important research direction in the field of high-precision sensors, weak pressure measurement technology is widely used in aerospace, medical and health monitoring, environmental monitoring, and precision instruments. With the development of related applications towards higher sensitivity, higher stability, and miniaturization, higher requirements are being placed on the detection accuracy and response capability of weak pressure signals.

[0003] Traditional weak pressure sensors mainly include piezoelectric sensors and resistance strain gauge sensors. Resistance strain gauge sensors typically convert deformation into a resistance change signal by bonding a strain gauge to the surface of an elastic substrate. However, in practical applications, the adhesive layer between the strain gauge and the elastic body significantly affects signal transmission, and their mechanical properties often mutually restrict each other, thus affecting the sensor's measurement accuracy, linearity, and long-term stability. Piezoelectric sensors achieve force-to-electricity conversion based on the piezoelectric effect of materials, but due to the problem of charge leakage, they are not suitable for long-term measurement of static or low-frequency weak pressure. Furthermore, their signal acquisition relies on high-performance charge amplifiers, resulting in high system costs and limited application range. In recent years, magnetostrictive materials have received widespread attention in the field of pressure and strain detection due to their excellent magneto-force coupling characteristics. These materials deform under the influence of an external magnetic field, and their magnetic properties change with the stress state, enabling the conversion between mechanical and magnetic signals. A current emerging and popular research direction is to utilize the Villari effect of magnetostrictive materials, which is the phenomenon that magnetic parameters such as permeability and magnetization of materials change under external stress. Sensors based on the Villari effect are more sensitive to minute stress changes and can generate significant magnetic response signals under extremely weak pressure, thereby greatly improving detection sensitivity and resolution, and providing a new technical path for the measurement of weak pressure.

[0004] Meanwhile, with the development of flexible electronics technology, flexible polymer materials, such as silicone rubber and polyester films, are widely used in wearable sensors and surface-mount detection devices due to their excellent elasticity, flexibility, and environmental adaptability. Combining magnetostrictive materials with flexible substrates to construct flexible composite structures offers advantages such as high pressure transmission efficiency, high-precision force-magnetic relationship conversion, and stable magnetic signal acquisition. This promises to achieve high-precision detection of complex curved surfaces or minute pressure distributions, showing promising application prospects, especially in the field of non-destructive testing of building materials and monitoring the operation of precision instruments in harsh environments requiring the measurement of weak pressure.

[0005] Currently disclosed flexible magnetostrictive sensor structures and fabrication technologies mostly employ a single magnetostrictive material to form the sensitive functional layer, resulting in a micrometer-thick thin film. The homogeneous composition and structure of this functional layer often lead to uneven stress transmission and localized stress concentration during stress application, resulting in poor sensor linearity, significant hysteresis, and insufficient repeatability. Alternatively, a simple blending of the magnetostrictive material with a single polymer matrix can be used to form a homogeneous composite layer, enhancing the flexibility and repeatability of the functional layer. However, this also reduces the permeability change under weak pressure due to the reduced content of the magnetostrictive material, weakening the magnetic signal output and lowering the force-magnetic coupling conversion efficiency. In traditional sensor structure design, there is a conflict between the rigid magnetostrictive element and the flexibility required for patch functionality, making it impossible to simultaneously meet the comprehensive requirements of high sensitivity, high linearity, good adhesion, and structural stability for weak pressure detection. Summary of the Invention

[0006] In view of this, the present invention proposes a flexible magnetostrictive material patch, its preparation method, and a detection device. The flexible magnetostrictive material patch possesses high sensitivity, high linearity, good flexibility, and environmental stability, making it suitable for monitoring complex curved surfaces and weak pressure scenarios.

[0007] The technical solution of this invention is implemented as follows: In a first aspect, the present invention provides a flexible magnetostrictive material patch, comprising, from bottom to top, a flexible substrate layer, an intermediate functional layer, and a flexible encapsulation layer. The flexible substrate layer comprises, from bottom to top, a PET film and Ecoflex silicone rubber. The intermediate functional layer comprises magnetostrictive material powder and polyether-type polyurethane elastomer. The flexible encapsulation layer comprises a high-modulus elastic polymer material.

[0008] In the flexible magnetostrictive material patch, a PET film is attached to the surface of the object to be tested, serving as a component for directly applying pressure to the patch.

[0009] This invention utilizes a composite three-layer structure design to construct a flexible magnetostrictive sensing patch, consisting of a PET / Ecoflex flexible substrate, a FeCoCr-polyether type polyurethane elastomer intermediate functional layer, and a PDMS elastomer encapsulated with hydrophobically modified fumed silica. This three-layer design ensures that the intermediate magnetostrictive functional layer is under approximately bidirectional uniform stress when subjected to forces on both its upper and lower surfaces. This improves the sensor's linearity and repeatability, ensuring its strain range and high stability in detecting weak pressure.

[0010] The Ecoflex base layer is made of ultra-soft platinum silicone, the magnetic dielectric constant functional layer is made of polyether-type polyurethane elastomer, and the encapsulation and protective surface layer is made of PDMS elastomer, which has a stretchability of over 250%.

[0011] The flexible substrate layer provides flexible support and deformation transmission capability for the overall structure. It has good ductility and resilience, and can uniformly and effectively transmit the pressure applied to the PET film surface to the upper functional structure. At the same time, it reduces local stress concentration, avoids fatigue damage to the material during repeated loading, and improves the consistency and repeatability of sensing signals.

[0012] Based on the above technical solution, the magnetostrictive material powder further comprises FeCoCr, and the mass ratio of the magnetostrictive material powder to the polyether-type polyurethane elastomer is (0.8~1.2):1.

[0013] When the powder-to-binder ratio is 0.5, the number of magnetic particles actually participating in the Villarius effect decreases, leading to a smaller change in permeability per unit pressure. Although the material flexibility is further improved, the force-to-magnetic conversion efficiency is significantly reduced, sensor sensitivity decreases, and the ability to detect weak pressure deteriorates. When the powder-to-binder ratio is 2, the proportion of FeCoCr powder is too high, resulting in increased direct contact between powder particles, making the composite layer brittle and exacerbating stress concentration. During the compression process, external pressure is difficult to uniformly transmit to each magnetostrictive particle, easily causing excessive local strain or microcracks, resulting in increased output signal fluctuations and decreased linearity. At the same time, due to insufficient binder phase, problems such as difficulty in leveling, agglomeration, cracking, and peeling are prone to occur during spraying, making it difficult to form a continuous and uniform functional layer and hindering the formation of a stable gradient structure through gravity settling.

[0014] In summary, when the mass ratio of magnetostrictive material powder to polyether-type polyurethane elastomer is less than 0.8:1, the sensitivity and accuracy are insufficient; when the powder-to-binder ratio is greater than 1.2:1, molding is difficult, and the molded product has low toughness, high brittleness, and is prone to breakage, resulting in severe drift and poor repeatability during use.

[0015] This invention utilizes the gravitational sedimentation behavior of magnetic powder (FeCoCr) in polyether-type polyurethane elastomers to spontaneously form an intermediate functional layer with a continuous gradient distribution along the thickness direction. The bottom layer is enriched with magnetic powder to enhance the mechano-magnetic conversion efficiency, while the surface layer is enriched with elastomer to ensure flexibility and uniform stress transmission, thus resolving the contradiction between sensitivity and flexibility. FeCoCr acts as the functional response unit, performing its normal sensing ring function; the polyether-type polyurethane elastomer is responsible for providing structural support stability, stress transmission paths, and overall flexibility. A stable physical interface is formed between the two, achieving stress transmission coupling, and they work in a synergistic relationship.

[0016] Specifically, the interaction between polyether-type polyurethane elastomer (PEFE) and FeCoCr is primarily a physical interface: the magnetostrictive powder particles are coated with PEFE elastomer, and the two are mainly mechanically interlocked, supplemented by a small amount of adhesion through van der Waals forces or interfacial chemical bonds. The core function of the PEFE elastomer coating is to achieve uniform stress transfer, acting as a mechanical coupling medium and synergistically forming a functional layer with FeCoCr. The PEFE elastomer can uniformly disperse particles, buffering and transmitting stress to the functional layer, thereby improving the linearity of the system. If only magnetostrictive materials are used as the functional layer, problems such as severe stress concentration and high signal noise are likely to occur.

[0017] Furthermore, the gravity migration behavior generated during the preparation process forms a gradient structure, which simultaneously amplifies the transduction efficiency and linearity of FeCoCr, as well as the structural support and flexibility of polyether polyurethane elastomers.

[0018] In addition to the synergistic effect with FeCoCr, the addition of polyether-type polyurethane elastomers offers the following process advantages: First, it facilitates molding. Using only magnetostrictive powders with conventional elastic polymers (such as epoxy resins and phenolic resins), curing agents, and solvents, leveling and film formation are difficult when the powder-to-binder ratio is high. Adding polyether-type polyurethane elastomers allows for the formation of an integral structure, facilitating subsequent spraying, spin coating, and other operations, significantly reducing the difficulty of preparation. Second, in this invention, a bias magnetic field is applied during the curing process to pre-magnetize the material. Adding polyether-type polyurethane elastomers is a prerequisite for achieving this step, as it helps form controllable microstructures and facilitates operations such as orientation structure and anisotropic design.

[0019] The raw materials for the intermediate functional layer may also include other flexible polyurethane elastomers, whose soft ends contain ether bonds and whose hard segments contain benzene rings.

[0020] Based on the above technical solutions, the high-modulus elastic polymer material further includes polydimethylsiloxane.

[0021] Based on the above technical solution, the flexible encapsulation layer further includes hydrophobic modified fumed silica. The preparation method of the hydrophobic modified fumed silica includes: preparing fumed silica by chemical vapor deposition, and then reacting the fumed silica with either dimethyldichlorosilane or hexamethyldisilazane to obtain the hydrophobic modified fumed silica.

[0022] The flexible encapsulation surface layer is prepared by uniformly mixing high-modulus elastic polymer material (PDMS) with hydrophobically modified fumed silica. The silica is hydrophobically modified to improve compatibility with PDMS and to give the outer surface of the flexible encapsulation layer hydrophobic and waterproof properties. This composite system simultaneously possesses excellent flexibility, mechanical strength, and environmental stability, serving to mechanically protect and isolate the intermediate magnetostrictive functional layer from environmental damage, preventing the effects of oxidation, humidity changes, and mechanical damage on sensing performance, and significantly improving the signal stability and reliability of the sensor. Furthermore, it forms a symmetrical structure of elastic polymer material with the flexible substrate layer, placing the intermediate functional layer in a near-bidirectional uniform stress state under stress, thus improving the linearity and repeatability of the sensor.

[0023] A PDMS elastomer-doped hydrophobic fumed silica encapsulation surface layer is constructed and completely covers the underlying structure to effectively isolate interference from external environmental changes such as temperature and humidity. This significantly enhances the system's scratch resistance, wear resistance, and puncture resistance, ensuring the stability of the flexible magnetostrictive material patch in operating environments. Furthermore, the hydrophobic surface properties improve the system's hydrophobic, waterproof, oxidation-resistant, corrosion-resistant, and hygrothermal aging-resistant capabilities. In addition, the superior tensile / compressive strength and fracture toughness of PDMS elastomer, along with its ability to deform with the Ecoflex layer, prevent material damage such as breakage or detachment. Ultimately, this results in minimal signal drift, high cycle stability, and extended service life.

[0024] Based on the above technical solutions, further, the thickness of the PET film is 100~300μm, the thickness of the Ecoflex layer is 0.5~1.5mm, the thickness of the flexible encapsulation layer is 0.5~1.5mm, and the thickness of the intermediate functional layer is 0.1~0.3mm.

[0025] According to the stress transfer theory of composite layers, increasing the thickness of the PET and Ecoflex layers leads to enhanced stress attenuation during the transfer process, while insufficient thickness prevents uniform stress distribution. If the thickness of the intermediate functional layer is too small, the number of magnetic response units will be insufficient; if the thickness is too large, the stress distribution along the thickness direction will be uneven, reducing the linearity of the force-magnetic conversion. Based on the magnetic field dipole attenuation and 1 / r... 3 Proportional to the magnetic signal, increasing the encapsulation layer thickness increases the magnetic signal detection distance, leading to a weakening of the magnetic response; conversely, insufficient thickness makes it difficult to provide effective environmental protection. Therefore, through theoretical analysis, finite element simulation, and experimental optimization, the thicknesses of the PET layer, Ecoflex layer, intermediate functional layer, and encapsulation layer were controlled within the aforementioned ranges to achieve optimal pressure transmission efficiency, magnetic response intensity, flexible adhesion capability, and environmental stability.

[0026] Secondly, the present invention also provides a method for preparing the flexible magnetostrictive material patch, comprising the following steps: S1, placing a PET film at the bottom of a mold, and then pouring Ecoflex silicone rubber into the mold to form a semi-cured Ecoflex layer; S2. Mix the magnetostrictive material powder and the polyether-type polyurethane elastomer evenly, and spray it onto the surface of the semi-cured Ecoflex layer to form an intermediate functional layer. S3. After mixing the high-modulus elastic polymer material and the hydrophobic modified fumed silica, the mixture is coated onto the surface of the intermediate functional layer to form a flexible encapsulation layer, thus obtaining the first material. S4. Apply a magnetic field to the first material and cure it to obtain the flexible magnetostrictive material patch.

[0027] The detection device is used to realize the entire pressure detection process of "applying pressure - converting pressure into magnetic field change - detecting magnetic field change - outputting corresponding pressure response".

[0028] Based on the above technical solution, the method of applying the magnetic field further includes: the external magnetic field is applied along the length direction of the flexible magnetostrictive material patch and parallel to the plane where the intermediate functional layer is located.

[0029] Applying a magnetic field causes the FeCoCr magnetostrictive particles in the intermediate functional layer to establish a stable initial magnetization state along the length direction, thereby forming a structure like... before actual use. Figure 1 The orientation shown.

[0030] Based on the above technical solution, the method for forming a semi-cured Ecoflex layer in step S1 further includes drying at 30~50℃ for 4~6 minutes.

[0031] A coating of FeCoCr and polyether-type polyurethane elastomer is sprayed onto the semi-solid Ecoflex substrate to form a semi-cured state. Then, the surface layer is spin-coated, and a certain external magnetic field is applied to orient the powder particles. Simultaneously, curing is carried out until the final product is formed.

[0032] Under conditions of moderate external pressure and a relatively weak external magnetic field, the relationship between stress and magnetic field strength is mainly influenced by the magnetostrictive properties of FeCoCr and the electron tunneling effect. This design can yield an intermediate functional layer with excellent linearity, sensitivity, and recovery capability.

[0033] Based on the above technical solution, the magnetic field strength in step S4 is further 80~120Gs.

[0034] The magnetostrictive material (FeCoCr) powder in the intermediate functional layer exhibits changes in magnetic parameters under weak external pressure. Pre-magnetizing the FeCoCr with an applied bias magnetic field further enhances the magnetic response signal. Under conditions of moderate external pressure and a relatively weak applied magnetic field, its permeability and magnetization change linearly with pressure, thus achieving effective coupling and conversion between pressure and magnetic field quantities, exhibiting high sensitivity and stability. Simultaneously, the FeCoCr powder is dispersed within a polyether-type polyurethane elastomer, concentrated in the bottom layer, forming a flexible, continuous gradient composite structure. Compared to a uniformly distributed FeCoCr powder, the bottom layer enhances the conversion capability, achieving a uniform distribution of stress transmission and improving the sensor's sensitivity and accuracy in detecting weak pressure. Furthermore, the polyether-type polyurethane elastomer concentrated on the surface layer improves the overall flexibility and mechanical stability of the patch, enabling it to adapt to pressure detection requirements under curved surface attachment and micro-deformation environments.

[0035] Thirdly, the present invention also provides a weak pressure detection device based on the flexible magnetostrictive material patch, including the flexible magnetostrictive material patch, a magnetic field biasing module, a pressure loading module, a magnetic signal detection module, and a data processing module; The magnetic field biasing module is used to apply a bias magnetic field to the flexible magnetostrictive patch. The pressure loading module is used to apply external pressure to the PET film side of the flexible magnetostrictive patch; The magnetic signal detection module is used to detect the change in the spatial magnetic field generated by the flexible magnetostrictive patch when it is compressed, and convert it into an electrical signal. The data processing module is used to receive and process the electrical signal and output the pressure detection result.

[0036] The detection device is used to realize the entire pressure detection process of "applying pressure - converting pressure into magnetic field change - detecting magnetic field change - outputting corresponding pressure response".

[0037] The weak pressure detection device and method utilize the Virari effect of magnetostrictive materials, where the magnetic parameters of the material change under external mechanical stress, thus forming a highly sensitive and accurate linear force-magnetic coupling relationship. The intermediate functional layer converts the weak pressure signal into a magnetic field change signal through the Virari effect, ensuring high-precision output from the device under low pressure.

[0038] When the flexible magnetostrictive material patch is compressed, the spatial magnetic field strength changes accordingly. A high-sensitivity GMR detection module acquires the weak magnetic field change signal, amplifies the signal through a low-noise amplifier circuit, and then converts it into a digital signal via an ADC for transmission to the host computer. The data processing module is responsible for filtering, amplifying, compensating, and fitting the digital signal, removing external noise for signal stabilization, and using a compensation algorithm to correct for environmental errors, achieving real-time output of the magnetic field strength value. A linear regression fitting model converts the magnetic field strength value into an actual pressure value, enabling long-term pressure signal detection through a GUI interface.

[0039] Based on the above technical solutions, the magnetic induction intensity of the bias magnetic field is further defined as 3~5 Gs.

[0040] Based on the above technical solutions, the length of the flexible magnetostrictive patch is 50-70mm and the width is 10-20mm.

[0041] Based on the actual specifications of the detection device and the magnetic properties of FeCoCr, the excitation magnetic field of the magnetic field bias module and the size parameters of the flexible magnetostrictive sensing patch were optimized. This included changing the bias magnetic field strength and the length and width of the patch, and comparing the sensitivity coefficients of the output response value and the load size to obtain the magnetic induction intensity range (3-5Gs) and the length (50~70mm) and width (10~20mm) of the patch that are suitable for the detection device and the selected FeCoCr-based flexible magnetostrictive patch.

[0042] Building upon the above technical solutions, the magnetic signal detection module further includes a GMR sensor and an STM32 main control unit. The GMR sensor employs a triaxial composite structure design to accurately acquire changes in the spatial magnetic field caused by pressure on the flexible magnetostrictive patch at the sensitive element in real time, converting this data into a processable electrical signal. The acquired signal is amplified by a low-noise amplifier circuit and then undergoes high-precision analog-to-digital conversion via an ADC. The magnetic signal detection module also includes an automatic threshold adjustment mechanism, which automatically adjusts the signal acquisition threshold based on changes in the actual working environment, ensuring stable capture of weak magnetic signals under various environmental conditions. Through the I2C serial communication protocol, this module connects to the data processing module, achieving efficient and stable signal transmission and ensuring high-precision detection of weak magnetic field quantities.

[0043] Based on the above technical solutions, the data processing module includes a GMR response signal waveform and real-time fitted pressure measurement values. The GMR response signal waveform, based on the digital signal transmitted by the magnetic signal detection module, uses Kalman filtering and exponential moving average filtering algorithms to remove noise caused by environmental changes, ensuring signal stability and accuracy. After gain amplification, a compensation algorithm is used to process the signal, correcting errors caused by changes in external environment such as temperature and humidity, ensuring the accuracy of the magnetic field signal measurement results. Finally, it is represented as an oscillation waveform of magnetic induction intensity over time. The real-time fitted pressure measurement values ​​are based on the aforementioned principle that "when the external pressure is not too high and the applied magnetic field is not too strong, the magnetic parameters change linearly with pressure." A linear regression fitting mathematical model is used to accurately convert the real-time response change signal output from the GMR response signal waveform into pressure measurement data. An RTOS is used for rapid data processing, presented through a graphical GUI interface, supporting long-term monitoring and data recording, ensuring high reliability and stability of weak pressure detection.

[0044] The design principle of this invention combines the high-precision mechanical-magnetic response effect of magnetostrictive materials, the continuous gradient distribution structure layer constructed based on the theory of gravity sedimentation, and the elasticity, flexibility, and environmental adaptability of flexible polymer materials. It achieves real-time monitoring of weak pressure signals through weak magnetic detection and algorithm amplitude modulation.

[0045] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention constructs a flexible magnetostrictive material patch using a composite three-layer structure design: a PET / Ecoflex base layer, a FeCoCr polyether-type polyurethane elastomer intermediate functional layer, and a PDMS elastomer-doped hydrophobically modified fumed silica encapsulation surface layer. The three-layer structure design enables the intermediate magnetostrictive functional layer to be in a near-bidirectional uniform stress state when subjected to force on both the upper and lower surfaces. This improves the linearity and repeatability of the sensor, ensuring its strain range and high stability in weak pressure detection.

[0046] (2) The method for preparing the flexible magnetostrictive material patch involves spraying a uniformly mixed coating of FeCoCr and polyether-type polyurethane elastomer onto the surface of a semi-cured Ecoflex substrate, so that part of the FeCoCr-polyether-type polyurethane elastomer partially penetrates into the Ecoflex layer through mechanical interlocking effect, and then a layer of PDMS-doped hydrophobic modified fumed silica is coated onto the entire layer structure by spin coating.

[0047] (3) In the preparation method of the present invention, the first material is cured when an external magnetic field is applied, which can make the powder arrangement oriented. At the same time, the gradient structure is constructed by waiting for the gravity migration behavior of FeCoCr powder in the polyether polyurethane elastomer matrix, forming a 0.1~0.3mm thick FeCoCr-polyether polyurethane elastomer continuous gradient distribution layer with pre-magnetization. Under the conditions that the external pressure is not too large and the external magnetic field is not too strong, the relationship between its stress and magnetic field strength is mainly affected by the magnetostrictive properties of FeCoCr itself and the electron tunneling effect. This design can obtain an intermediate functional layer with excellent linearity, sensitivity and recovery ability.

[0048] (4) The preparation method provided by the present invention effectively improves the flexibility, ductility, working range and mechanical stability of the system under bending deformation conditions. The linear strain range of the Ecoflex layer after being subjected to force can reach 250%, and its bending radius is reduced from 2.5 mm to 1.7 mm. The tensile strength of PDMS is increased by about 18%, from the original 1.2 MPa to 1.42 MPa. At the same time, the process does not significantly affect the internal stress distribution of the FeCoCr-polyether type polyurethane elastomer layer. Its magnetostriction coefficient is maintained at 0.28±0.02, and the magnetic field response sensitivity under 1% strain can reach 150 nT in 20 cycles of deformation.

[0049] (5) Further, based on the flexible magnetostrictive material patch and its preparation process, the present invention designs a weak pressure measurement device and method, including a flexible magnetostrictive sensing patch, a magnetic field bias module, a pressure loading module, a magnetic signal detection module and a data processing module. The device is designed for working scenarios in the extremely low pressure range and has the characteristics of stability, high sensitivity, fast response speed, stable cycle performance and adaptability to different types of pressure sources. It can present the waveform of the spatial magnetic field strength over time through the magnetic signal detection module and the data processing module and realize real-time pressure value detection. Attached Figure Description

[0050] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0051] Figure 1This is a structural design diagram of a flexible magnetostrictive material patch according to an embodiment of the present invention, including a local SEM image of the fracture section of the FeCoCr-polyether type polyurethane elastomer hybrid layer along the direction of the applied magnetic field and a SEM image of the material density gradient of the complete cross section. Figure 2 This is a schematic diagram of a weak pressure detection device module based on a flexible magnetostrictive patch according to an embodiment of the present invention. Figure 3 The present invention provides a graph showing the functional relationship between the GMR sensor response value and the applied pressure value measured by the material and supporting device in the initial state, the 20th stretch, and the 20th compression, respectively, for embodiments of the present invention.

[0052] Figure 4 The present invention provides positive and negative error band diagrams of GMR sensor response values ​​measured by the material and supporting device in the initial state, at the 20th stretch, and at the 20th compression, respectively, for embodiments of the present invention.

[0053] Figure 5 The waveform diagram of the response signal of the GMR sensor of the material and supporting device under a micro-vibration pressure source is provided for Embodiment 1 of the present invention. Detailed Implementation

[0054] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0055] This invention provides a flexible magnetostrictive material patch, its preparation method, and a testing device, wherein the structure of the flexible magnetostrictive material patch is designed as follows: Figure 1As shown, the sensor patch structure includes a PET film 1, an Ecoflex transition layer 2, a FeCoCr-polyether polyurethane elastomer magnetic dielectric elasticity composite functional layer 3, and an encapsulation surface layer 6. The magnetic dielectric elasticity composite functional layer comprises FeCoCr powder 4 enriched in the bottom layer and polyether polyurethane elastomer 5. The figure shows that the sensor patch structure employs a stacked design of three elastic polymer materials with different properties: Ecoflex, polyether polyurethane elastomer, and PDMS. This design balances flexibility and mechanical stability. Furthermore, the use of an elastic polymer-functional layer-elastic polymer sandwich structure creates a symmetrical structure that allows the intermediate functional layer to be in a near-bidirectional uniform stress state under stress, improving the linearity and repeatability of the sensor. Compared to traditional weak pressure measurements that directly use dense bulk materials or stacked materials composed of a single material for each layer, the composite three-layer flexible sensing structure of this invention decouples and synergistically optimizes the main functions of each layer—rigid support and stress transmission, sensitive response, and protective encapsulation—to achieve superior performance compared to traditional magnetostrictive materials. Furthermore, by adjusting the filler distribution and interfacial properties, the material's flexibility and deformability were significantly improved, enabling minute external pressures to be transmitted more fully and evenly to the magnetostrictive sensing unit, ultimately enhancing the force-magnetic coupling sensitivity. Simultaneously addressing the issues of short lifespan and high wear rate in traditional rigid magnetostrictive sensors, the structure maintains overall mechanical stability while possessing excellent adhesion and environmental adaptability, allowing it to conform to complex curved surfaces and be suitable for wearable or irregular surface measurement scenarios.

[0056] The preparation method includes the following steps: (1) Take a double-sided PET film with a thickness of 100~300μm, perform surface plasma cleaning, and place it at the bottom of the mold; (2) Mix the Ecoflex precursor with the curing agent and stir evenly, remove air bubbles by vacuuming, pour it into the mold, control the curing time to keep it in a semi-cured state, and form a semi-solid Ecoflex layer with a thickness of 0.5~1.5mm; (3) Mix the magnetostrictive material powder, polyether polyurethane elastomer and curing agent and stir evenly, remove air bubbles by vacuuming, and apply the magnetostrictive material-polyether polyurethane elastomer by spraying. The composite layer is laid flat on the surface of the base layer and spontaneously forms an intermediate functional layer of 0.1~0.3 mm thickness under the control of gravity migration behavior; (4) The high modulus elastic polymer material is mixed with hydrophobic modified fumed silica and stirred evenly, ultrasonically dispersed, vacuumed to remove bubbles, and spin-coated onto the incompletely cured magnetostrictive material-polyether polyurethane elastomer functional layer, so that it completely covers the PET film, Ecoflex layer and magnetostrictive material-polyether polyurethane elastomer functional layer, forming a 0.5~1.5 mm thick stable encapsulation protective layer; (5) Take neodymium iron boron magnets and place them at both ends of the material to generate along the Figure 1A uniform magnetic field of 100 Gs along the long axis is applied, followed by heating and curing, so that each layer completes the cross-linking reaction and the interlayer mechanical interlocking at the same time, forming an integrated composite three-layer structure, which constitutes a flexible magnetostrictive sensing patch.

[0057] The detection device is as follows Figure 2 As shown, it includes a power supply, a left coil, a right coil, a fixing fixture, a flexible magnetostrictive material patch, a GMR sensor, a pressure loading platform, a magnetic signal detection circuit, and a data processing system. Together, they form a flexible magnetostrictive sensing patch, a magnetic field bias module, a pressure loading module, a magnetic signal detection module, and a data processing module, which are used to realize the entire pressure detection process of "applying pressure - converting pressure into magnetic field change - detecting magnetic field change - outputting corresponding pressure response". The modules work together as follows: (1) Magnetic field bias in pre-magnetization: Under the power supply, the left and right coils apply a constant bias magnetic field of 3-5 Gs to the flexible magnetostrictive sensing patch along the bias magnetic field direction, so that the FeCoCr magnetostrictive powder in the patch reaches the optimal pre-magnetization state, establishes a stable initial permeability and linear working range, and provides a basis for the magnetic parameter response under weak pressure.

[0058] (2) Pressure loading and stress transfer: The weak pressure to be measured is applied to the pressure loading platform and uniformly transferred to the flexible magnetostrictive sensing patch through the fixing fixture; the flexible magnetostrictive material patch bears the pressure with the PET / Ecoflex base layer and efficiently and uniformly transmits the stress to the middle magnetic dielectric high-elasticity composite functional layer to avoid local stress concentration.

[0059] (3) Force-magnetic signal conversion: Under stress, the intermediate functional layer undergoes linear changes in magnetic parameters such as permeability and magnetization intensity based on the Villari effect, causing the magnetic field strength around the patch to change regularly in accordance with the pressure magnitude, thus completing the physical quantity conversion of weak pressure-magnetic field changes.

[0060] (4) Magnetic signal acquisition: The GMR sensor acquires the weak magnetic field change signal around the patch in real time and converts the magnetic signal into an analog electrical signal; the GMR sensor adopts a triaxial composite structure and is equipped with an automatic threshold adjustment mechanism to suppress environmental noise interference and stably capture weak magnetic response.

[0061] (5) Signal conditioning and analog-to-digital conversion: The analog electrical signal is amplified by the low-noise amplifier circuit in the magnetic signal detection circuit, and then the ADC completes the high-precision analog-to-digital conversion to obtain the digital magnetic signal; the digital signal is stably transmitted to the data processing system through the I2C serial communication protocol.

[0062] (6) Data processing and pressure output: The data processing system uses Kalman filtering and exponential moving average filtering to remove environmental noise and corrects environmental errors such as temperature and humidity through compensation algorithms. Based on the linear regression fitting model, the digital signal of magnetic field strength is converted into the corresponding pressure value. The pressure data is displayed and recorded in real time through the GUI interface to complete the high-precision and stable detection of weak pressure.

[0063] The magnetic field bias module provides a uniform magnetic field dispersed throughout the entire space, pre-magnetizing the magnetostrictive patch. Most of the magnetic domains are pre-oriented along the magnetic field direction, establishing a stable initial magnetization state. When pressure is applied to the intermediate functional layer, the stress-induced change in magnetic anisotropy further drives these partially oriented domains to rotate. At this point, the change in magnetization intensity increases significantly, thus making the detected magnetic field change more pronounced. From the BH image, the role of the bias magnetic field is to adjust the slope (i.e., permeability) by controlling H, thereby increasing the slope and adjusting the material's operating point to the high-sensitivity region of the magnetization curve.

[0064] The function of the pressure loading module is to apply the external pressure to be detected. For performance testing of the sensing system, a load of known mass can be applied to selected components of a material testing machine. Furthermore, the pressure loading module can be subjected to various forms of load, including static, quasi-static, dynamic, and periodically alternating loads. This is determined by the characteristics of the Villarius effect, unlike other types of weak pressure sensors such as piezoelectric and piezoresistive sensors.

[0065] The magnetic field detection system converts the magnetic field changes caused by the patch into digital signals output to the host computer, and is not limited to a specific device. This invention uses a giant magnetoresistive sensor. The sensing element is installed in a manner optimized through simulation testing and micro-adjustment, specifically 3-4 mm below the lower surface of the material's middle end. It collects the magnetic signals changing before and after pressure is applied using a multi-channel synchronous AD conversion controlled by hardware processing circuitry. The weak magnetic signal is converted into a weak electrical signal by a signal conversion circuit, and then amplified step-by-step by an amplification circuit into an electrical signal. Finally, the microcontroller processes the signal and outputs digital data.

[0066] The collected data is fed into the data processing system and the background algorithm within the interactive unit. This algorithm comprises two parts: signal preprocessing and fitting calculation. The preprocessing step, analyzing the serial port assistant data converted from the sensor gain setting lookup table, employs a weighted average filtering algorithm. The fitting calculation, on the other hand, is based on the SciPy and Matplotlib modules built into JetBrain Riders and their related algorithms. The processed signal yields real-time magnetic field strength data, which is matched with the input pressure value and subjected to linear regression fitting. The resulting image is then displayed on the interactive interface.

[0067] In the following specific embodiments, the hydrophobically modified fumed silica was purchased from Maclean's Reagent Store, item number N817574; In the following specific embodiments, the preparation method of polyether-type polyurethane elastomer includes: using polypropylene glycol (Mw=2000, 3000) and toluene diisocyanate (TDI-80) as raw materials to prepare polyether-type polyurethane elastomer PPG / TDI with NCO group content of 5.0% by prepolymer method; Ecoflex 00-10 silicone rubber was purchased from Ruimai Flagship Store on JD.com, item number 563842402728; PET film, JD.com Sanxihu Laboratory Supplies Flagship Store, item number 10202209112952; The PDMS was purchased from the TONSAN store on JD.com, item number DC184.

[0068] In the following specific implementation methods, unless otherwise specified, all materials used are conventional materials that are commercially available.

[0069] Example 1 This embodiment provides a flexible magnetostrictive material patch, its preparation method, and a testing device.

[0070] 1. The preparation method includes the following steps: (1) Select a commercial PET film with a thickness of 200 μm, cut it into small pieces of 20 mm × 20 mm, place the PET film flat in the plasma cleaning machine chamber, and evacuate to 10 mm. -1 After the pressure drops below Pa, high-purity oxygen is introduced, and the mixture is treated in an oxygen plasma environment for 90 seconds. After completion, a PET film is placed at the bottom of the mold. (2) Take 30g of Ecoflex 00-10 silicone rubber, mix it with the curing agent in a 1:1 ratio and stir for 1 minute. Place the well-stirred mixture into a vacuum pump until no bubbles are observed, then remove it. (3) Pour the prepared mixture into the prefabricated mold to form the Ecoflex base layer, and control the pouring height at 1mm; (4) After casting Ecoflex, place the mold with the PET film at the bottom in a 40°C drying environment for 5 minutes and then remove it; (5) Take 20g of heat-treated Fe 43.5 Co 43.5 Cr 13The flake-shaped powder was mixed with PPG / TDI, a polyether-type polyurethane elastomer with 5.0% NCO content, at a powder-to-adhesive mass ratio of 1:1. Then, a curing agent and 10g of solvent were added at a polyether-type polyurethane elastomer to curing agent mass ratio of 1:0.5. The mixture was stirred for 10 minutes until the viscosity of the coating was suitable for spraying. The well-stirred mixture was placed in a vacuum pump and removed after observing that no bubbles appeared. (6) Spray FeCoCr-PPG / TDI coating onto the surface of the uncured substrate to form a 0.2mm thick FeCoCr-PPG / TDI functional layer; (7) After the material obtained in step (6) is cured in a 40°C drying environment, it is taken out and removed after 15 minutes; (8) Take 30g of PDMS and the curing agent in a ratio of 10:1, add 3 wt% of hydrophobic modified fumed silica, stir for 5 minutes until uniform, place the mixture in an ultrasonic disperser, disperse at 100 W for 8 minutes, and then place it in a vacuum pump until no bubbles are observed before taking it out. (9) The mixture prepared in step (8) is coated onto the surface of the material obtained in (7) by spin coating, completely covering the PET film, Ecoflex layer and FeCoCr-PPG / TDI layer to form a 1mm thick encapsulation protective layer. (10) Place neodymium iron boron magnets at both ends of the material to generate a linear... Figure 1 A uniform magnetic field of 100 Gs along the long axis was used to send the magnet and the material into the drying oven, where they were dried sequentially at 40°C for 2 hours, at 60°C for 2 hours, and at 80°C for 8 hours. (11) Remove and complete the preparation of the flexible magnetostrictive material patch.

[0071] 2. A schematic diagram of a weak pressure detection device based on the aforementioned flexible magnetostrictive material patch is shown below. Figure 2 As shown, it includes a flexible magnetostrictive sensing patch, a magnetic field bias module, a pressure loading module, a magnetic signal detection module, and a data processing module, which are used to realize the entire pressure detection process of "applying pressure - converting pressure into magnetic field change - detecting magnetic field change - outputting corresponding pressure response".

[0072] Based on the actual specifications of the detection device and Fe 43.5 Co 43.5 Cr 13 The electromagnetic parameters were optimized using ANSYS to optimize the excitation magnetic induction intensity of the magnetic field bias module and the length and width of the flexible magnetostrictive sensing patch. The applied magnetic field magnetic induction intensity was controlled to be 4Gs, the patch length to be 50mm, and the width to be 15mm. At this time, the pressure detection device has the maximum response pressure-magnetic response sensitivity within the detection range.

[0073] In the weak pressure detection device provided in this embodiment, after the magnetostrictive sensing patch is magnetized to a certain extent by the magnetic field bias module, when a weak external pressure is applied to the surface of the PET film of the patch, the stress is conducted through the Ecoflex transition layer in the internal structure of the patch. In the FeCoCr-PPG / TDI layer, this causes a change in the magnetic domain structure inside the FeCoCr crystal in the form of mechanical strain, resulting in a change in the macroscopic magnetic permeability of FeCoCr and generating a corresponding spatial magnetic field strength change signal, thus realizing the conversion of pressure signal into magnetic field signal. The weak magnetic signal is converted into a weak point signal by the magnetic signal detection module dominated by the GMR sensor. After processing by amplification circuit, analog-to-digital conversion, etc., it is input to the data processing module. The filtering algorithm is used to remove external noise for signal stabilization, and the compensation algorithm is used to correct errors caused by environmental factors such as temperature and airflow. Finally, the response signal oscillation waveform over time is presented, and the real-time fitted pressure measurement value is output through the GUI interface.

[0074] Figure 3 The relationship between the GMR sensor response value and the applied pressure value is measured by a matching pressure measuring device after the flexible magnetostrictive material patch of Example 1 undergoes 20 tensile and compressive deformations. The magnetic induction intensity is 4Gs, the patch length is 60mm, and the width is 15mm.

[0075] Figure 4 The diagram shows the positive and negative error bands at each steady-state pressure point under the 20th stretch, 20th compression, and original length conditions.

[0076] from Figure 3 and Figure 4 As can be seen, under the measurement conditions and within the measurement range, the disturbance amplitude of the force-magnetic relationship conversion efficiency caused by repeated stretching and compression is within 3%. Under different pressures, the efficiency changes of the stretching and recovery processes are monotonically and simultaneously tend to be opposite, and the pressure signal and the magnetic field change signal have a linear relationship. The slope of the fitting curve is the sensitivity coefficient of the magnetic field change to pressure. Based on the sensitivity coefficient of the standard fitting curve, the corresponding pressure value can be calculated according to the response value caused by the real-time input pressure. This flexible magnetostrictive patch material has mechanical-magnetic field conversion performance with high linearity, high sensitivity, large working range, and excellent fatigue performance.

[0077] Figure 5 The waveform of the GMR response signal of the pressure measuring device described in Example 1 facing the micro-vibration pressure source is shown, with artificial instantaneous pressure intervention implemented at 47 seconds and 134 seconds.

[0078] from Figure 5Overall, the output signal fluctuates slightly around a certain reference value when there is no strong pressure stimulus, the system output is relatively stable, the baseline drift is small, and the voltage fluctuation range is narrow, reflecting that the system has a low static noise level. This indicates that the flexible magnetostrictive patch and its matching pressure detection device block have a certain degree of stability and repeatability. When an instantaneous dynamic pressure input is applied to the boundary, a significant sudden drop in signal occurs, and the fluctuation amplitude is significantly increased compared to the baseline. This indicates that when the sensing patch is subjected to pressure, it can complete the stress transmission traversing the PET surface-Ecoflex layer transition-intermediate functional layer in a very short time, and cause a rapid response of the GMR sensor output voltage through the Villari effect. This shows that the device also has good sensitivity and response capability to weak but sudden pressure changes. In addition, from the perspective of response characteristics, the signal can quickly recover to the original fluctuation range after the sudden change, without obvious hysteresis or residual offset. This indicates that the flexible structure has good elastic recovery performance after being subjected to force. The PET / Ecoflex + magnetostrictive composite layer + PDMS design structure does not show obvious plastic deformation or hysteresis accumulation effect, which is conducive to achieving repeated measurements and long-term stable operation.

[0079] Example 2 This embodiment provides a flexible magnetostrictive material patch, its preparation method, and a testing device.

[0080] 1. The preparation method includes the following steps: (1) Select a commercial PET film with a thickness of 100 μm, cut it into small pieces of 20 mm × 20 mm, place the PET film flat in the plasma cleaning machine chamber, and evacuate to 10 mm. -1 After the pressure drops below Pa, high-purity oxygen is introduced, and the mixture is treated in an oxygen plasma environment for 90 seconds. After completion, a PET film is placed at the bottom of the mold. (2) Take 30g of Ecoflex 00-10 silicone rubber, mix it with the curing agent in a 1:1 ratio and stir for 1 minute. Place the well-stirred mixture into a vacuum pump until no bubbles are observed, then remove it. (3) Pour the prepared mixture into the prefabricated mold to form the Ecoflex base layer, and control the pouring height at 1.5mm; (4) After casting Ecoflex, place the mold with the PET film at the bottom in a 30°C drying environment for 6 minutes and then remove it; (5) Take 20g of heat-treated Fe 43.5 Co 43.5 Cr 13The flake-shaped powder was mixed with PPG / TDI, a polyether-type polyurethane elastomer with 5.0% NCO content, at a powder-to-binder mass ratio of 1:0.8. Then, a curing agent and 10g of solvent were added at a polyether-type polyurethane elastomer-to-curing agent mass ratio of 1:0.5. The mixture was stirred for 10 minutes until the viscosity of the coating was suitable for spraying. The well-stirred mixture was placed in a vacuum pump until no bubbles were observed, and then removed. (6) Spray FeCoCr-PPG / TDI coating onto the surface of the uncured substrate to form a 0.1mm thick FeCoCr-PPG / TDI functional layer; (7) After the material obtained in step (6) is cured in a 40°C drying environment, it is taken out and removed after 15 minutes; (8) Take 30g of PDMS and the curing agent in a ratio of 10:1, add 3 wt% of hydrophobic modified fumed silica, stir for 5 minutes until uniform, place the mixture in an ultrasonic disperser, disperse at 100 W for 8 minutes, and then place it in a vacuum pump until no bubbles are observed before taking it out. (9) The mixture prepared in step (8) is coated onto the surface of the material obtained in (7) by spin coating, completely covering the PET film, Ecoflex layer and FeCoCr-PPG / TDI layer to form a 0.5 mm thick encapsulation protective layer. (10) Place neodymium iron boron magnets at both ends of the material to generate a linear... Figure 1 A uniform magnetic field of 100 Gs along the long axis was used to send the magnet and the material into the drying oven, where they were dried sequentially at 40°C for 2 hours, at 60°C for 2 hours, and at 80°C for 8 hours. (11) Remove and complete the preparation of the flexible magnetostrictive material patch.

[0081] 2. The weak pressure detection device based on the flexible magnetostrictive material patch differs from that in Example 1 in that: the magnetic induction intensity of the applied magnetic field is controlled to be 3Gs, the patch length is 60mm, and the width is 10mm.

[0082] Example 3 This embodiment provides a flexible magnetostrictive material patch, its preparation method, and a testing device.

[0083] 1. The preparation method includes the following steps: (1) Select a commercial PET film with a thickness of 300 μm, cut it into small pieces of 20 mm × 20 mm, place the PET film flat in the plasma cleaning machine chamber, and evacuate to 10 mm. -1 After the pressure drops below Pa, high-purity oxygen is introduced, and the mixture is treated in an oxygen plasma environment for 90 seconds. After completion, a PET film is placed at the bottom of the mold. (2) Take 30g of Ecoflex 00-10 silicone rubber, mix it with the curing agent in a 1:1 ratio and stir for 1 minute. Place the well-stirred mixture into a vacuum pump until no bubbles are observed, then remove it. (3) Pour the prepared mixture into the prefabricated mold to form the Ecoflex base layer, and control the pouring height at 0.5mm; (4) After casting Ecoflex, place the mold with the PET film at the bottom in a 50°C drying environment for 4 minutes and then remove it; (5) Take 20g of heat-treated Fe 43.5 Co 43.5 Cr 13 The flake-shaped powder was mixed with PPG / TDI, a polyether-type polyurethane elastomer with 5.0% NCO content, at a powder-to-binder mass ratio of 1:1.2. Then, a curing agent and 10g of solvent were added at a polyether-type polyurethane elastomer-to-curing agent mass ratio of 1:0.5. The mixture was stirred for 10 minutes until the viscosity of the coating was suitable for spraying. The well-stirred mixture was placed in a vacuum pump and removed after observing that no bubbles appeared. (6) Spray FeCoCr-PPG / TDI coating onto the surface of the uncured substrate to form a 0.3mm thick FeCoCr-PPG / TDI functional layer; (7) After the material obtained in step (6) is cured in a 40°C drying environment, it is taken out and removed after 15 minutes; (8) Take 30g of PDMS and the curing agent in a ratio of 10:1, add 3 wt% of hydrophobic modified fumed silica, stir for 5 minutes until uniform, place the mixture in an ultrasonic disperser, disperse at 100 W for 8 minutes, and then place it in a vacuum pump until no bubbles are observed before taking it out. (9) The mixture prepared in step (8) is coated onto the surface of the material obtained in (7) by spin coating, completely covering the PET film, Ecoflex layer and FeCoCr-PPG / TDI layer to form a 1.5mm thick encapsulation protective layer. (10) Place neodymium iron boron magnets at both ends of the material to generate a linear... Figure 1 A uniform magnetic field of 100 Gs along the long axis was used to send the magnet and the material into the drying oven, where they were dried sequentially at 40°C for 2 hours, at 60°C for 2 hours, and at 80°C for 8 hours. (11) Remove and complete the preparation of the flexible magnetostrictive material patch.

[0084] 2. The weak pressure detection device based on the flexible magnetostrictive material patch differs from that in Example 1 in that: the magnetic induction intensity of the applied magnetic field is controlled to be 5Gs, the patch length is 70mm, and the width is 20mm.

[0085] Comparative Example 1 This comparative example provides a flexible magnetostrictive material patch, its preparation method, and a testing device. In this comparative example, a three-layer structure is formed by directly bonding the PET film to the intermediate functional layer and then to the flexible encapsulation layer. The remaining steps are the same as in Example 1. The difference from Example 1 is that the Ecoflex transition layer is not set in steps (2), (3), and (4), and the intermediate functional layer is in direct contact with the pressure-bearing surface through the PET film.

[0086] Material mechanical property testing and practical application revealed that, due to the lack of an Ecoflex transition layer, the overall stiffness of the structure in Comparative Example 1 was relatively high, with an equivalent elastic modulus of approximately 8–12 MPa, making it difficult to achieve good flexibility matching. When attached to curved surfaces or soft substrates, the minimum bending radius of the patch was approximately 5–7 mm, which easily led to localized lifting or interface debonding, resulting in discontinuous pressure transmission. Furthermore, in tensile tests, its elongation at break was only 40%–60%, indicating insufficient ductility. Under pressure during the 20th tensile and 20th compression tests, interfacial microcracks were easily generated, affecting structural stability.

[0087] In contrast, Example 1, by introducing a low-hardness Ecoflex transition layer between the PET film and the intermediate functional layer, creates a gradient transition from a rigid support layer to a flexible functional layer in the overall structure, significantly improving the material's flexibility and ductility. Its equivalent elastic modulus can be reduced to approximately 1-3 MPa, and the minimum bending radius can be reduced to approximately 2 mm, enabling stable adhesion to complex curved surfaces. Simultaneously, the elongation at break is increased to 150%-250%, maintaining good structural integrity even after 20 tensile and 20 compressive tests. Therefore, the Ecoflex transition layer plays a crucial role in alleviating interfacial stress concentration, improving flexibility matching, and enhancing structural durability, making it an indispensable structural unit for realizing high-performance flexible magnetostrictive sensing patches.

[0088] Comparative Example 2 This comparative example provides a flexible magnetostrictive material patch, its preparation method, and a testing device. The comparative example uses a three-layer structure of PET / Ecoflex, FeCoCr film, PDMS, and hydrophobic fumed silica. The remaining steps are the same as in Example 1. The difference between this comparative example and Example 1 is that steps (5) and (6) are omitted. FeCoCr powder of the same mass as used in (5) of Example 1 is molded using a compression molding process. At room temperature, it is unidirectionally molded at 300 MPa for 1 min to prepare a dense FeCoCr sheet with a density ≥95%. This dense FeCoCr sheet is directly bonded to the surface of a PET film. There is no PPG / TDI transition or interface bonding treatment between layers; the composite is achieved solely through physical contact.

[0089] Material mechanical property testing and practical application revealed that, due to the lack of a flexible PPG / TDI substrate and gradient structure design, the overall rigidity of the proportional structure was significantly improved, with an equivalent elastic modulus of approximately 18-22 MPa, making it difficult to achieve good flexibility matching. When attached to curved or soft substrates, the minimum bending radius of the patch was approximately 9-11 mm, which easily led to localized lifting or interfacial debonding, resulting in discontinuous pressure transmission. Furthermore, in tensile tests, its elongation at break was only 15%-25%, indicating severely insufficient ductility. Under pressure during the 20th tensile and 20th compression tests, microcracks and interlayer delamination in the FeCoCr flakes were easily generated, affecting structural stability. In contrast, Example 1, with its gradient functional layer constructed from polyether-type polyurethane elastomer, creates a gradient transition from a rigid functional layer to a flexible substrate in the overall structure. This reduces the equivalent elastic modulus to 1-3 MPa and the minimum bending radius to approximately 2 mm, enabling stable adhesion to complex curved surfaces. Simultaneously, the elongation at break is increased to 150%-250%, maintaining good structural integrity even after 20 tensile and 20 compression tests. Therefore, the PPG / TDI substrate plays a crucial role in alleviating interfacial stress concentration, improving flexibility matching, and enhancing structural durability, making it an indispensable structural unit for realizing high-performance flexible magnetostrictive sensing patches.

[0090] Comparative Example 3 This comparative example provides a flexible magnetostrictive material patch, its preparation method, and a testing device. The difference from Example 1 is that step (5) uses a dispersant-assisted forced uniform dispersion process to prepare a homogeneous intermediate functional layer, including the following steps: FeCoCr powder, PPG / TDI, and curing agent of equal mass as used in step (5) of Example 1 are mixed, and γ-aminopropyltriethoxysilane (KH550) with a mass fraction of 2% is added. The mixture is first stirred for 15 min at 5000 r / min using a high-speed shear homogenizer, and then dispersed for 20 min at 300W using an ultrasonic disperser, so that the FeCoCr powder is uniformly dispersed in PPG / TDI without agglomeration, eliminating the concentration gradient along the thickness direction. After the uniformly mixed coating is sprayed onto the surface of the Ecoflex film, it is immediately placed in an 80°C environment for rapid curing for 2 hours to completely block the powder sedimentation process and form a uniform intermediate functional layer with uniform composition throughout.

[0091] In the material mechanical property testing and pressure sensing performance verification, it was found that during stress transmission, FeCoCr was uniformly encapsulated and isolated by PPG / TDI, and the effective stress concentration factor was still 45%~55% lower than that of Example 1, and the force-magnetic conversion coupling efficiency was significantly reduced. When detecting weak pressures of 0~100 kPa, the permeability change amplitude was only 52%~58% of that of Example 1, the sensing sensitivity was approximately 0.65~0.85 mV / kPa, and the minimum detection resolution decreased from 0.1 kPa in Example 1 to 0.3 kPa, making it difficult to accurately identify minute pressure fluctuations. Simultaneously, the cyclic loading hysteresis error reached 13%~16%, and the signal repeatability error after 20 cycles was ±7.5%~±9%, with a linear fitting correlation coefficient R0... 2 The values ​​were only 0.970~0.978, far lower than the 0.993~0.996 of the gradient structure in Example 1. Furthermore, after being placed in a humid heat environment of 60℃ and 90% RH for 24 hours, the comparative structure showed a signal drift of ±8.5%, indicating that its fatigue resistance and long-term stability were significantly inferior to Example 1. This demonstrates that achieving uniform powder dispersion solely through dispersants cannot replace the gravity-driven gradient distribution structure. The latter, through powder enrichment along the stress transmission path, significantly optimizes stress transmission efficiency and force-magnetic conversion performance, and is the core design for improving the sensitivity, detection accuracy, and structural stability of the magnetostrictive functional layer.

[0092] Comparative Example 4 This comparative example provides a flexible magnetostrictive material patch, its preparation method, and a testing device. The flexible encapsulation layer is made using Ecoflex and does not contain hydrophobically modified fumed silica.

[0093] The difference from Example 1 is that in step (8), an equal amount of Ecoflex is used instead of PDMS, and hydrophobic modified fumed silica is not used.

[0094] In the compression deformation and dynamic mechanical property tests, it was found that the surface compression deformation of the structure in Comparative Example 3 reached 25%~35% during compression, and the proportion of stress effectively transferred to the functional layer decreased. Simultaneously, its storage modulus was approximately 0.05~0.1 MPa, exhibiting obvious viscoelastic characteristics. During cyclic loading, the energy hysteresis loss was approximately 20%, accompanied by some signal hysteresis and baseline drift. Furthermore, due to the high permeability of Ecoflex material, performance fluctuations are easily caused in humid and hot environments, resulting in relatively poor environmental adaptability. In contrast, Example 1 used PDMS doped with hydrophobic fumed silica as the surface layer, controlling its compression deformation to within 10%, increasing the storage modulus to approximately 0.5~1 MPa, and reducing hysteresis loss to below approximately 8%. This allows pressure to be applied more concentratedly and efficiently to the intermediate functional layer, and the signal remains stable with minimal drift during cyclic loading. It also maintains good structural integrity and performance consistency under humid and hot environmental conditions, demonstrating superior mechanical stability and environmental adaptability.

[0095] Comparative Example 5 This comparative example provides a flexible magnetostrictive material patch, its preparation method, and a testing device. The difference from Example 1 is that it does not contain polyether-type polyurethane elastomer; instead, it directly uses heat-treated Fe... 43.5 Co 43.5 Cr 13 The flake-shaped powder is evenly distributed on the surface of the uncured substrate layer.

[0096] In the material mechanical property testing and pressure sensing performance verification, it was found that, due to the absence of a gradient distribution structure formed by PPG / TDI matrix coating and gravity sedimentation in Comparative Example 5, the magnetic particles were mainly concentrated on the surface of Ecoflex, resulting in unstable interparticle contact and poor stress distribution uniformity. When a pressure of 0–100 kPa was applied, the permeability change amplitude was only 55%–65% of that in Example 1, the sensing sensitivity was approximately 0.70–0.95 mV / kPa, and the minimum detection resolution decreased from 0.1 kPa in Example 1 to 0.3–0.5 kPa, indicating a significant weakening of the ability to detect weak pressure. In the bending adhesion test, due to the lack of flexible polymer coating protection in the particle layer, when the bending radius decreased to below 3 mm, localized particle detachment and functional layer discontinuity were prone to occur.

[0097] Comparative Example 6 This comparative example provides a flexible magnetostrictive material patch, its preparation method, and a testing device, which differs from Example 1 in that: Step (4): After casting Ecoflex, place the mold with the bottom PET film together in a 70℃ drying environment for 10 minutes and then remove it. The Ecoflex layer will be completely cured.

[0098] In the material mechanical property testing and pressure sensing performance verification, it was found that because the Ecoflex layer was fully cured before the functional layer was sprayed, it was difficult to form an effective interface between the intermediate functional layer and the substrate layer, resulting in a decrease in stress transfer efficiency. Within the pressure range of 0–100 kPa, its permeability variation amplitude was only 65%–75% of that in Example 1, the sensing sensitivity was approximately 0.85–1.05 mV / kPa, and the minimum detection resolution decreased from 0.1 kPa in Example 1 to 0.2–0.3 kPa. Simultaneously, the cyclic loading hysteresis error increased to 8%–11%, the signal repeatability error after 20 cycles was ±5.0%–±6.5%, and the linear fitting correlation coefficient R² was only 0.978–0.985. Bending adhesion testing showed that when the bending radius decreased to approximately 3 mm, micro-delamination was prone to occur at the local interface, leading to increased signal fluctuations. In contrast, Example 1, by controlling the Ecoflex layer to be in a pre-cured state, enabled a more stable interface bond between the functional layer and the substrate layer, thereby achieving higher stress transfer efficiency and sensing stability. It is evident that Ecoflex's semi-curing process plays a crucial role in constructing stable interfaces and improving sensing performance.

[0099] Comparative Example 7 This comparative example provides a flexible magnetostrictive material patch, its preparation method, and a testing device, which differs from Example 1 in that: Step (4): Place the mold after casting Ecoflex along with the PET film at the bottom in a 30°C drying environment for 1 minute and then remove it.

[0100] In the material mechanical property testing and pressure sensing performance verification, it was found that because the Ecoflex layer was only treated in a 30℃ drying environment for 1 min and had not yet reached a semi-cured state, its surface fluidity was high, causing some powder and PPG / TDI system to penetrate into the substrate layer, affecting the formation of the gradient structure. Within the pressure range of 0–100 kPa, its magnetic permeability variation amplitude was only 70%–80% of that in Example 1, the sensing sensitivity was approximately 0.90–1.10 mV / kPa, and the minimum detection resolution decreased to 0.2–0.3 kPa. After 20 cycles, the signal repeatability error was ±4.5%–±6.0%, the cycle hysteresis error was approximately 7%–10%, and the linear fitting correlation coefficient R² was 0.980–0.987. In contrast, Example 1, by controlling the Ecoflex to reach a suitable semi-cured state, achieved a more stable interface structure and superior pressure sensing performance. Therefore, the semi-cured state of Ecoflex plays a crucial role in the construction of the functional layer and the improvement of sensing performance.

[0101] Comparative Example 8 This comparative example provides a flexible magnetostrictive material patch, its preparation method, and a testing device. The difference from Example 1 is that no magnetic field is applied in step (10).

[0102] In the testing of material mechanical properties and the verification of pressure sensing performance, it was found that, due to the lack of an applied magnetic field for orientation treatment, Fe... 43.5 Co 43.5 Cr 13 The plate-like particles are randomly distributed within the functional layer, making it difficult to form a uniform preferred magnetization direction, resulting in a weakened magnetostrictive response. Within a pressure range of 0–100 kPa, the permeability variation amplitude is only 60%–70% of that in Example 1, the sensing sensitivity is approximately 0.75–0.95 mV / kPa, and the minimum detection resolution decreases to 0.3–0.5 kPa. After 20 cycles, the signal repeatability error is ±5.5%–±7.0%, and the linear fitting correlation coefficient R0 is [not specified]. 2 The values ​​range from 0.975 to 0.983. In contrast, Example 1, through magnetic field orientation treatment, forms an ordered arrangement of magnetic particles, significantly improving the force-to-magnetic conversion efficiency and pressure detection sensitivity. It is evident that magnetic field orientation treatment plays a crucial role in enhancing the sensing performance of flexible magnetostrictive material patches.

[0103] Comparative Example 9 This comparative example provides a flexible magnetostrictive material patch, its preparation method, and a testing device. The difference between this example and Example 1 is that it does not include step (10). Step (7) involves placing neodymium iron boron magnets at both ends of the material to generate a flow along... Figure 1 A uniform magnetic field of 100Gs along the long axis was used to send the magnet and the material obtained in step (6) into a drying oven. After curing in a drying environment at 40℃, the material was taken out and removed after 15 minutes.

[0104] In the testing of material mechanical properties and the verification of pressure sensing performance, it can be found that due to the application of a magnetic field during the curing process of the functional layer, Fe... 43.5 Co 43.5 Cr 13The sheet-like particles undergo orientation movement before the resin system is fully cured. Some particles aggregate locally under the combined effects of gravity settling and magnetic field drive, leading to a decrease in the uniformity of orientation in the thickness direction. Simultaneously, as the curing process progresses, the system viscosity gradually increases, and the orientation of some particles is prematurely fixed, making it difficult to achieve the optimal magnetization state. Within the pressure range of 0–100 kPa, the permeability variation amplitude is 75%–85% of that of Example 1, the sensing sensitivity is approximately 1.00–1.20 mV / kPa, and the minimum detection resolution is 0.2 kPa. After 20 cycles, the signal repeatability error is ±4.0%–±5.5%, and the linear fitting correlation coefficient R² is 0.982–0.989. In contrast, Example 1, by performing magnetic field orientation treatment after the functional layer has formed and stabilized, achieves a more uniform particle orientation structure and higher force-magnetic conversion efficiency, thus exhibiting superior pressure sensing performance.

[0105] Comparative Example 10 This comparative example provides a method for preparing a flexible magnetostrictive material patch and a testing device, which differs from Example 1 in that the bias magnetic induction intensity in the testing is 1 Gs.

[0106] In actual testing, it was found that when the bias magnetic induction intensity was 1 Gs, the magnetization of the magnetostrictive material was insufficient, the GMR output signal variation was small, and its sensitivity was about 0.6~0.8 mV / kPa, which was significantly lower than the approximately 1.2~1.5 mV / kPa of Example 1 under the condition of 4 Gs. At the same time, the slope of the output curve was relatively gentle, and the signal-to-noise ratio dropped to about 18~22 dB, making it difficult to effectively distinguish weak pressure changes.

[0107] Comparative Example 11 This comparative example provides a method for preparing a flexible magnetostrictive material patch and a testing device, which differs from Example 1 in that the bias magnetic induction intensity in the testing is 7 Gs.

[0108] In actual testing, it was found that when the bias magnetic field was increased to 7 Gs, the material gradually approached magnetic saturation, the GMR response became more gradual, and its sensitivity decreased to approximately 0.7~0.9 mV / kPa. Furthermore, the linear range shortened to approximately 0~60 kPa, significantly smaller than the 0~100 kPa linear range of Example 1. In addition, signal fluctuations increased under high magnetic field conditions, and the repeatability error increased to approximately ±6%~±8%. In contrast, Example 1 showed the most significant output curve change, the largest signal slope, and the best stability under a 4 Gs bias magnetic field, achieving a balance between high sensitivity and good linearity.

[0109] Comparative Example 12 This comparative example provides a method for preparing a flexible magnetostrictive material patch and a testing device. The difference from Example 1 is that the size of the flexible magnetostrictive material patch is too small, at 30mm × 5mm.

[0110] In actual testing, it was found that when a 30mm×10mm patch was used, the effective sensing area was reduced by about 60%, the overall deformation under pressure was reduced, the output signal amplitude dropped by about 30%~45%, and the corresponding sensitivity was about 0.7~0.9mV / kPa. At the same time, local stress concentration increased the signal fluctuation, and the repeatability error was about ±7%.

[0111] Comparative Example 13 This comparative example provides a method for preparing a flexible magnetostrictive material patch and a testing device. The difference from Example 1 is that the size of the flexible magnetostrictive material patch is too small, which is 90mm×30mm.

[0112] In actual testing, it was found that when 70mm×20mm was selected, although the sensing area increased, the excessive structural flexibility led to uneven stress distribution and a decrease in the proportion of effective stress actually transmitted to the functional layer. Its sensitivity was about 0.9~1.1 mV / kPa, and there was a hysteresis error of about 10%~15%, and the response time was extended by about 20%~30%.

[0113] Therefore, based on the Fe selected in this invention 43.5 Co 43.5 Cr 13 The electromagnetic parameters of the magnetostrictive material and the size of the provided device show that the pressure-magnetic field response is most significant and stable when the size is on the order of 50mm×15mm, while the curve tends to flatten out or fluctuate more when the size deviates from this range.

[0114] In summary, this invention proposes a flexible magnetostrictive material patch, its preparation method, and a detection device. The flexible magnetostrictive material patch comprises, from bottom to top, a flexible substrate layer, an intermediate functional layer, and a flexible encapsulation layer. The flexible substrate layer comprises, from bottom to top, a PET film and an Ecoflex layer. The intermediate functional layer comprises FeCoCr and a polyether-type polyurethane elastomer. This invention utilizes the gravitational sedimentation effect and the application of an external magnetic field to create a continuous gradient distribution of FeCoCr powder in the intermediate functional layer. Combined with a "soft-hard-soft" symmetrical sandwich structure, this improves the stress transfer efficiency and force-magnetic coupling linearity of the patch. The preparation method involves spraying the intermediate functional layer coating onto the semi-cured Ecoflex layer and applying a magnetic field for orientation curing, achieving integrated molding. This invention also provides a weak pressure detection device based on this patch. By applying a 3-5 Gs bias magnetic field and using a GMR sensor to detect the magnetic field change caused by pressure, the pressure value is output using a filtering and fitting algorithm. This patch exhibits high sensitivity, high linearity, good flexibility, and environmental stability, making it suitable for complex curved surfaces and weak pressure monitoring scenarios.

[0115] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A flexible magnetostrictive material patch, characterized in that, From bottom to top, it includes a flexible substrate layer, an intermediate functional layer, and a flexible encapsulation layer. The flexible substrate layer comprises, from bottom to top, a PET film and Ecoflex silicone rubber. The intermediate functional layer comprises magnetostrictive material powder and polyether-type polyurethane elastomer. The flexible encapsulation layer comprises a high-modulus elastic polymer material.

2. The flexible magnetostrictive material patch as described in claim 1, characterized in that, The magnetostrictive material powder includes FeCoCr, and the mass ratio of the magnetostrictive material powder to the polyether-type polyurethane elastomer is (0.8~1.2):

1.

3. The flexible magnetostrictive material patch as described in claim 1, characterized in that, The high-modulus elastic polymer material includes polydimethylsiloxane.

4. The flexible magnetostrictive material patch as described in claim 3, characterized in that, The flexible encapsulation layer further includes hydrophobic modified fumed silica. The preparation method of the hydrophobic modified fumed silica includes: preparing fumed silica by chemical vapor deposition, and then reacting the fumed silica with either dimethyldichlorosilane or hexamethyldisilazane to obtain the hydrophobic modified fumed silica.

5. A method for preparing a flexible magnetostrictive material patch as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Place the PET film at the bottom of the mold, and then pour the Ecoflex silicone rubber into the mold to form a semi-cured Ecoflex layer; S2. Mix the magnetostrictive material powder and the polyether-type polyurethane elastomer evenly, and spray it onto the surface of the semi-cured Ecoflex layer to form an intermediate functional layer. S3. The raw material of the flexible encapsulation layer is coated onto the surface of the intermediate functional layer to form a flexible encapsulation layer, thus obtaining the first material; S4. Apply a magnetic field to the first material and cure it to obtain the flexible magnetostrictive material patch.

6. The preparation method according to claim 5, characterized in that, The method for forming a semi-cured Ecoflex layer in step S1 includes drying at 30~50℃ for 4~6 minutes.

7. The preparation method according to claim 6, characterized in that, The magnetic field strength in step S4 is 80~120 Gs.

8. A weak pressure detection device based on a flexible magnetostrictive material patch according to any one of claims 1 to 4, characterized in that, include: The flexible magnetostrictive patch, magnetic field biasing module, pressure loading module, magnetic signal detection module, and data processing module as described in any one of claims 1 to 4; The magnetic field biasing module is used to apply a bias magnetic field to the flexible magnetostrictive patch. The pressure loading module is used to apply external pressure to the PET film side of the flexible magnetostrictive patch; The magnetic signal detection module is used to detect the change in the magnetic field generated by the flexible magnetostrictive patch when it is compressed, and convert it into an electrical signal. The data processing module is used to receive and process the electrical signal and output the pressure detection result.

9. The weak pressure detection device as described in claim 8, characterized in that, The magnetic induction intensity of the bias magnetic field is 3~5 Gs.

10. The weak pressure detection device as described in claim 8, characterized in that, The length of the flexible magnetostrictive patch is 50-70mm and the width is 10-20mm.

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