Thermal / magnetic shielding composite structure for flexible hall type force sensor

Abstract

Disclosed in the present invention is a thermal / magnetic shielding composite structure for a flexible Hall type force sensor, which is constituted by an outer thermal-insulation functional layer and an inner low-frequency magnetic field shielding functional layer. The outer thermal-insulation functional layer is formed by combining three composite material layers, which are successively, from outside to inside, a flexible thermal-insulation composite material layer, a flexible high-frequency magnetic field shielding and cooling composite material layer and a flexible thermal-insulation composite material layer; the inner low-frequency magnetic field shielding functional layer is a flexible low-frequency magnetic field shielding composite material layer. The thermal / magnetic shielding composite structure provided by the present invention can effectively shield both thermal interference and broadband magnetic field interference so as to ameliorate the problem of interference in the use of flexible Hall type force sensors, and has excellent elasticity and flexibility, being suitable for manufacturing elastic sensitive elements of different structures and dimensions.

Description

Thermal / magnetic shielding composite structure for flexible Hall-effect force sensor Technical Field

[0001] The present invention belongs to the technical field of functional polymer composite materials, and in particular relates to a thermal / magnetic shielding composite structure for a flexible Hall-type force sensor. Background Art

[0002] Flexible Hall-type force sensors based on magnetic fields can be used to measure complex tactile information of contact interfaces, helping intelligent robots perceive and obtain external environmental information, thereby realizing the interaction between intelligent robots and the external environment. Due to their high sensitivity, good stability and simple structure, they have broad application prospects in the field of robot skin. However, flexible Hall-type force sensors based on magnetic fields are extremely susceptible to the influence of environmental interference magnetic fields and the proximity / contact of sensors with heat sources in their use scenarios. Therefore, designing a thermal / magnetic shielding composite structure that can be applied to flexible Hall-type force sensors is of great significance to the development of flexible Hall-type force sensors. In recent years, people have done a lot of work on the research of electromagnetic and thermal shielding materials:

[0003] In the article "Shielding Effectiveness of Multilayer Composite Electrodeposited Magnetic Shielding Films", the chemical composition and thickness of the deposited film were precisely controlled by electrodeposition, and an iron-nickel / copper / iron-nickel multilayer composite magnetic shielding film was prepared on an aluminum cylindrical substrate. The film can achieve a shielding effectiveness of 38-62 dB in a magnetic field of 4-16 Oe with a thickness of 200 μm [Gong Jian, Xu Changyou, Wang Donghong, et al. Shielding Effectiveness of Multilayer Composite Electrodeposited Magnetic Shielding Films [J]. Journal of Terahertz Science and Electronic Information, 2020, 18(02): 259-263.]. However, since the composite film prepared by the deposition method does not have stretchability and flexibility, it is very easy to crack and defect when deformed by force. Therefore, it is not suitable for use in flexible Hall-type force sensors where the shielding layer will deform with the force of the sensor.

[0004] Patent CN112980199B, titled "Organic Silicone Composite Magnetic Material for Low-Frequency Alternating Magnetic Field Shielding and Its Preparation Method," utilizes soft magnetic alloy powder fillers, such as iron-nickel-molybdenum magnetic powder, iron-silicon magnetic powder, iron-silicon-aluminum magnetic powder, iron-silicon-chromium magnetic powder, and amorphous and nanocrystalline magnetic powders. These are mixed with organic silicon materials and then vulcanized to produce a composite material with excellent mechanical strength and flexibility for shielding against low-frequency (below 200kHz) radiation interference magnetic fields. However, because only soft magnetic alloy powder is used as the primary filler, the composite magnetic material only effectively shields low-frequency magnetic fields below 200kHz, without the ability to simultaneously shield against thermal interference and broadband magnetic field interference.

[0005] Patent CN111698898B, titled "A Wide-Width Electromagnetic Shielding Material and Its Preparation Method," utilizes an electromagnetic shielding layer composed of at least one layer of soft magnetic alloy strip, at least one layer of wide soft magnetic alloy sheet, and / or at least one layer of wide good conductor material, along with protective films on the upper and lower surfaces. This effectively reduces magnetic flux leakage while forming a wide electromagnetic shielding material. However, because the material primarily consists of non-stretchable soft magnetic alloy strip, soft magnetic alloy sheet, and wide good conductor material, the resulting electromagnetic shielding layer has poor flexibility and is difficult to shape, making it unsuitable for shielding flexible Hall-effect force sensors.

[0006] In the article "Preparation and Properties of Silicone Rubber Thermal Insulation Composites", hollow glass microspheres (HGB) and expanded vermiculite (EVMT) were used as thermal insulation fillers and blended with high-temperature vulcanized silicone rubber (HTV) to prepare HGB / HTV and EVMT / HTV thermal insulation composites, respectively. By setting the filling mass ratio of HGB to HTV to 20 / 100 and the filling mass ratio of EVMT to HTV to 10 / 100, the thermal conductivity of the HTV material samples was reduced by 20.44% and 12.34%, respectively [Zeng Shengqu, Chen Xiang, Luo Piaohui. Preparation and Properties of Silicone Rubber Thermal Insulation Composites [J]. Synthetic Rubber Industry, 2023, 46(02): 119-123.]. However, due to the single type and particle size of the thermal insulation fillers, the filling amount of the composite material is limited by the mechanical properties, making it difficult to further reduce the thermal conductivity and improve the thermal insulation performance.

[0007] In the article "Preparation and Thermal Insulation Properties of Expanded Perlite and Fumed Silica Filled Silicone Rubber Composites," a 2.5 cm thick perlite-fumed silica powder composite insulation material was prepared by mixing and bonding 107 silica gel to perlite and fumed silica powder. With a 37.5% inorganic filler filling mass ratio, a thermal conductivity of 0.0349 W·m was achieved. -1 ·K -1 Thermal insulation composite materials [Wang Wei, Kong Bo, Chen Shumei, et al. Preparation and thermal insulation properties of expanded perlite and fumed silica filled silicone rubber composites [J]. Journal of the Chinese Ceramic Society, 2023, 51(04): 975-981.]. However, the thermal insulation system is composed of only a single layer of material. When the outside temperature is high, there will still be a large accumulation of local heat inside the thermal insulation layer, and the thermal insulation effect is still poor at a low thickness.

[0008] In the article “Soft Magnetic Tactile Skin for Continuous Force and Location Estimation Using Neural Networks”, a Hall-type flexible three-dimensional force sensor was developed, which consists of a flexible magnetic source and six Hall chips. Among them, five Hall chips are used to detect the influence of three-dimensional force on the magnetic field signal, and the Hall chip in direct alignment with the center chip is used to detect the interference of external factors on the magnetic field as a reference for numerical compensation [Tess Hellebrekers, et al. Soft Magnetic Tactile Skin for Continuous Force and Location Estimation Using Neural Networks[J]. IEEE ROBOTICS AND AUTOMATION LETTERS, 2020, 5(3): 3892-3898.]. However, due to the uneven distribution of environmental stray magnetic fields and temperature, the environmental interference at the reference chip and the center chip is inconsistent, so this method has a limited shielding effect on external magnetic fields and temperature.

[0009] The article "A Gradiometric Magnetic Force Sensor Immune to Stray Magnetic Fields for Robotic Hands and Grippers" designs a three-dimensional force sensor consisting of a magnet, an elastomer, and multiple Hall elements. It uses the gradient of the magnetic field intensity detected by multiple Hall elements to eliminate the interference of external stray magnetic fields. At the same time, it uses a temperature sensor and a temperature compensation algorithm to reduce temperature drift [Théo Le Signor, et al. A Gradiometric Magnetic Force Sensor Immune to Stray Magnetic Fields for Robotic Hands and Grippers [J]. IEEE ROBOTICS AND AUTOMATION LETTERS, 2022, 7(2): 3070-3076.]. However, the shielding effect is still poor in an external magnetic field environment that is relatively uniform and changes rapidly and uncertainly. In the case of inconsistent temperatures between the magnetic source and the Hall element caused by heat sources, the compensation effect is also limited.

[0010] In summary, it is still a great challenge to prepare a thermal / magnetic shielding composite material with both high flexibility and high shielding effectiveness.

[0011] Summary of the Invention

[0012] Based on the problems existing in the above-mentioned prior art, the present invention provides a thermal / magnetic shielding composite structure for a flexible Hall-type force sensor, which can effectively shield thermal interference and broadband magnetic field interference during the application of the flexible Hall-type force sensor.

[0013] To achieve the purpose, the present invention adopts the following technical solutions:

[0014] The present invention first discloses a thermal / magnetic shielding composite structure for a flexible Hall-type force sensor, which is composed of an outer thermal insulation functional layer and an inner low-frequency magnetic field shielding functional layer; the outer thermal insulation functional layer is composed of three layers of composite materials, which, from the outside to the inside, are a flexible thermal insulation composite material layer, a flexible high-frequency magnetic field shielding and heat dissipation composite material layer, and a flexible thermal insulation composite material layer; the inner low-frequency magnetic field shielding functional layer is a flexible low-frequency magnetic field shielding composite material layer.

[0015] Furthermore, the flexible heat-insulating composite material layer is made by simultaneously filling fumed silica particles and expanded perlite particles into a silicone rubber matrix based on a foaming process and a thermal curing process, and its thermal conductivity is not higher than 0.04 W·m -1 ·K -1 , tensile strength not less than 4MPa, elongation at break not less than 30%. Thermal conductivity refers to the amount of heat transferred through an area of ​​1 square meter in one hour under stable heat transfer conditions, with a temperature difference of 1 degree (K, ℃) on both sides of a 1m thick material. The unit is W·m -1 ·K -1 The thermal conductivity of the composite material is low enough to significantly reduce the speed at which heat from the external heat source is transferred to the inside.

[0016] Furthermore, the flexible high-frequency magnetic field shielding and heat dissipation composite material layer is made based on a thermal curing process by filling a silicone rubber matrix with flaky silver-coated nickel powder filler and gallium-based liquid metal droplets treated with a 3-mercaptopropyltrimethoxysilane surface coating, and the filler is arranged in a directional manner, with a volume resistivity of no more than 105Ω·cm and an in-plane thermal conductivity of no less than 4W·m -1 ·K -1 , tensile strength is not less than 4MPa, and elongation at break is not less than 50%. The shielding of high-frequency alternating magnetic fields by conductive materials relies on the reverse magnetic field of eddy currents generated on the surface of the shielding shell by electromagnetic induction to offset the magnetic field entering the shielding body. The conductive paths of the composite material are dense enough and the resistivity is low enough to significantly attenuate the intensity of the high-frequency alternating magnetic field passing through the shielding film. The high-frequency magnetic field shielding composite material prepared according to the above-mentioned volume resistivity can make the shielding effect of the 0.5mm thick shielding composite material against high-frequency magnetic fields above 200kHz reach more than 30dB.

[0017] Furthermore, the flexible low-frequency magnetic field shielding composite material layer is made by filling a silicone rubber matrix with ferromagnetic nanowires and flaky Sendust alloy powder surface-modified with a silane coupling agent (γ-aminopropyltriethoxysilane, KH-550) based on a thermal curing process, and the magnetic conductive fillers are arranged in a directional manner, and the magnetic permeability is not less than 110 H·m -1 , tensile strength not less than 4MPa, and elongation at break not less than 30%. Low-frequency magnetic field shielding mainly uses a closed shielding cover made of soft magnetic material with high magnetic permeability to divert the magnetic field passing through the shielding area. The magnetic path is sufficiently smooth and dense, and the magnetic permeability is high enough to significantly attenuate the magnetic field strength passing through the inner side of the shielding area.

[0018] In the flexible Hall-type force sensor thermal / magnetic shielding composite structure of the present invention, the flexible thermal insulation composite material layer comprises a thermal insulation filler system composed of expanded perlite particles of varying particle sizes and fumed silica particles. The composite material is foamed with a blowing agent to create uniformly distributed microporous bubbles, further reducing the thermal conductivity of the composite material. The flexible high-frequency magnetic field shielding and heat dissipation composite material layer comprises a synergistic thermal / electrical conductive network composed of solid flaky silver-coated nickel powder and liquid gallium-based liquid metal. The flaky silver-coated nickel powder is oriented parallel to the film surface, further enhancing the in-plane thermal conductivity of the composite material. The flexible low-frequency magnetic field shielding composite material layer comprises a multi-dimensional synergistic magnetic conductive network composed of one-dimensional ferromagnetic nanowires and two-dimensional flaky Sendust magnetic powder. The ferromagnetic nanowires and flaky Sendust alloy powder are oriented parallel to the film surface after magnetic field alignment, further enhancing the in-plane magnetic permeability of the composite material.

[0019] The method for preparing the thermal / magnetic shielding composite structure for the flexible Hall-type force sensor of the present invention comprises the following steps:

[0020] Step 1: Prepare a flexible thermal insulation composite material layer

[0021] The following raw materials are weighed in parts by weight: 10-20 parts of expanded perlite particles with a particle size range of 20-30 μm, 10-20 parts of fumed silica particles with a particle size range of 30-50 nm, 100 parts of component A of a two-component room temperature curing silicone rubber, 10 parts of component B of a two-component room temperature curing silicone rubber, 1-4 parts of a foaming agent N,N'-dinitrosopentamethylenetetramine, 1-2 parts of a foaming aid pentaerythritol, 5-10 parts of a silane coupling agent, and 50-100 parts of anhydrous ethanol.

[0022] The weighed expanded perlite particles, fumed silica particles and silane coupling agent are placed in anhydrous ethanol, magnetically stirred at room temperature for 1 to 2 hours, and then dried in an oven to obtain a surface-modified filler powder; the surface-modified filler powder is mixed with the weighed foaming agent, foaming aid and component A of a two-component room-temperature curing silicone rubber, and then ultrasonically dispersed at a power of 1000 to 2000 W for 1 to 2 hours, and then the weighed component B of the two-component room-temperature curing silicone rubber is added, and ultrasonic dispersion is continued for 5 to 20 minutes. After that, the mixture is loaded into an aluminum molding mold and heated in an oven at 130 to 150° C. for 5 to 8 hours for foaming and curing to obtain a flexible thermal insulation composite material layer.

[0023] Step 2: Prepare a flexible high-frequency magnetic field shielding and heat dissipation composite material layer

[0024] The following raw materials are weighed in parts by weight: 50-70 parts of flaky silver-coated nickel powder, 10-20 parts of gallium-based liquid metal, 3-7 parts of 3-mercaptopropyltrimethoxysilane, 100 parts of component A of two-component room temperature curing silicone rubber, 10 parts of component B of two-component room temperature curing silicone rubber, 3-7 parts of silane coupling agent, and 100-150 parts of anhydrous ethanol.

[0025] The weighed gallium-based liquid metal, 3-mercaptopropyltrimethoxysilane and 50-100 parts of anhydrous ethanol are mixed, and ultrasonically dispersed at a power of 1000-2000 W for 1-3 hours to obtain gallium-based liquid metal droplets with a surface coating treatment with 3-mercaptopropyltrimethoxysilane.

[0026] The weighed flaky silver-coated nickel powder and silane coupling agent are placed in the remaining anhydrous ethanol, ultrasonically dispersed at a power of 1000-2000 W for 1-2 hours, and then dried in an oven to obtain a surface-modified flaky silver-coated nickel powder.

[0027] The surface-modified flaky silver-coated nickel powder, the gallium-based liquid metal droplets coated with 3-mercaptopropyltrimethoxysilane, and the weighed component A of the two-component room-temperature curing silicone rubber are mixed and placed in a horizontal ball mill. After stirring at room temperature for 1 to 2 hours, the component B of the two-component room-temperature curing silicone rubber is added and stirred for 5 to 20 minutes. The resulting slurry is vacuum-evacuated in a vacuum treatment furnace to remove bubbles, and then injected into an aluminum molding mold. The slurry is placed in a magnetic field with a magnetic induction intensity of 0.5 to 1.5 T parallel to the magnetic field, and the sample is rotated 90 degrees every 2 to 3 minutes until the slurry loses fluidity. The sample is then placed in the magnetic field for 15 to 20 hours, taken out, and heated in an oven at 100 to 150° C. for 5 to 10 hours to completely cure it, thereby obtaining the flexible high-frequency magnetic field shielding and heat dissipation composite material layer.

[0028] Step 3: Prepare a flexible low-frequency magnetic field shielding composite material layer

[0029] The following raw materials are weighed by weight: 20-50 parts of ferromagnetic nanowire powder, 100-150 parts of flaky Sendust alloy powder, 100 parts of component A of two-component room temperature curing silicone rubber, 10 parts of component B of two-component room temperature curing silicone rubber, 4-10 parts of silane coupling agent, 1-5 parts of dispersant, and 50-100 parts of anhydrous ethanol.

[0030] The weighed ferromagnetic nanowire powder, flaky Sendust alloy powder and silane coupling agent are placed in anhydrous ethanol, ultrasonically dispersed at a power of 1000-2000 W for 1-2 hours, and then dried in an oven to obtain a mixed filler surface-modified with a silane coupling agent.

[0031] The mixed filler surface-modified with a silane coupling agent is mixed with the weighed component A and dispersant of the two-component room-temperature curing silicone rubber and placed in a horizontal ball mill. After stirring at room temperature for 1 to 2 hours, the component B of the two-component room-temperature curing silicone rubber is added and stirring is continued for 5 to 20 minutes. The resulting slurry is vacuum-evacuated in a vacuum treatment furnace to remove bubbles and then injected into an aluminum forming mold. The slurry is then placed in a magnetic field with a magnetic induction intensity of 0.5 to 1.5 T parallel to the magnetic field. The sample is rotated 90 degrees every 2 to 3 minutes until the slurry loses fluidity. The sample is then placed in the magnetic field for 15 to 20 hours, taken out, and heated in an oven at 100 to 150° C. for 5 to 10 hours to completely cure it, thereby obtaining the flexible low-frequency magnetic field shielding composite material layer.

[0032] Step 4: Prepare a thermal / magnetic shielding composite structure for a flexible Hall-type force sensor

[0033] The surfaces of the composite material layers obtained in steps 1, 2 and 3 are brushed with a primer treatment agent and dried, and then coated with a silicone adhesive. Subsequently, the composite material layers are stacked in order from the outside to the inside, namely, a flexible thermal insulation composite material layer, a flexible high-frequency magnetic field shielding and heat dissipation composite material layer, a flexible thermal insulation composite material layer, and a flexible low-frequency magnetic field shielding composite material layer. The layers are placed in an oven and heated at 100 to 200° C. for 20 to 30 minutes to complete curing, thereby obtaining the thermal / magnetic shielding composite structure for the flexible Hall-type force sensor.

[0034] Compared with the prior art, the beneficial effects of the present invention are embodied in:

[0035] 1. The present invention provides a thermal / magnetic shielding composite structure for a flexible Hall-type force sensor. Through the specific functions of each layer and their combination, it can effectively shield thermal interference and broadband magnetic field interference at the same time, thereby improving the thermal interference and magnetic field interference problems in the application process of the flexible Hall-type force sensor.

[0036] 2. The present invention uses silicone rubber as the base material to ensure that each functional layer has both good shielding effectiveness and excellent elasticity and flexibility. It is suitable for making elastic sensitive elements of different structures and sizes, and is used in flexible Hall-type force sensors of various structures.

[0037] 3. The present invention forms a thermal insulation functional layer with gradient thermal conductivity through a sandwich structure consisting of a flexible thermal insulation composite material layer, a flexible high-frequency magnetic field shielding and heat dissipation composite material layer, and a flexible thermal insulation composite material layer, which effectively slows down the speed of heat transfer from the outside to the inside and further improves the temperature shielding capability.

[0038] 4. The flexible high-frequency magnetic field shielding and heat dissipation composite material layer proposed in the present invention is constructed by filling flaky silver-coated nickel powder and gallium-based liquid metal droplets with high thermal conductivity and high electrical conductivity into silicone rubber, thereby constructing a solid / liquid synergistic high-density conductive / thermal conductive network, and preparing a flexible composite material with both high thermal conductivity and electromagnetic shielding performance.

[0039] 5. The flexible high-frequency magnetic field shielding and heat dissipation composite material layer proposed in the present invention induces the flaky silver-coated nickel powder filler to be oriented in the direction parallel to the membrane surface in the composite material during the room temperature curing process of a uniform mixed slurry filled with flaky silver-coated nickel powder and gallium-based liquid metal droplets, thereby increasing the density of the conductive / thermal conductive network parallel to the membrane surface, thereby further improving the high-frequency magnetic field shielding effectiveness and the thermal conductivity in the membrane surface direction.

[0040] 6. The flexible, low-frequency magnetic field shielding composite material proposed in this invention constructs a multi-dimensional, synergistic, high-density magnetic network by simultaneously filling silicone rubber with ferromagnetic nanowires and flaky iron-silicon-aluminum alloy powder, resulting in a flexible composite material with high soft magnetic properties. Furthermore, treatment with a rotating magnetic field induces the alignment of the one- and two-dimensional soft magnetic fillers parallel to the composite surface, increasing the density of the composite's in-plane magnetic network and further enhancing its low-frequency magnetic field shielding performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIG1 is a schematic cross-sectional view of the thermal / magnetic shielding composite structure in Example 1 of the present invention.

[0042] FIG2 is a schematic diagram of the filler oriented arrangement treatment process in step 2 and step 3 of Example 1 of the present invention.

[0043] Figure 3 is a schematic diagram of the filler system structure before and after the oriented arrangement treatment of the flexible high-frequency magnetic field shielding and heat dissipation composite material layer ((a) in Figure 3) and the flexible low-frequency magnetic field shielding composite material layer ((b) in Figure 3) in Example 1 of the present invention.

[0044] FIG4 is a curve showing the variation of the in-plane thermal conductivity of the flexible high-frequency magnetic field shielding and heat dissipation composite material layer with the filler mass fraction in Example 1 of the present invention.

[0045] FIG5 is a curve showing the change of the in-plane magnetic permeability of the flexible low-frequency magnetic field shielding composite material layer as a function of the filler mass fraction in Example 1 of the present invention.

[0046] FIG6 is a schematic diagram of the heat shielding principle when the outer heat insulation functional layer contacts a heat source in Example 1 of the present invention.

[0047] FIG7 is a schematic diagram of a device for testing the temperature shielding effect of the thermal / magnetic shielding composite structure in Example 1 of the present invention.

[0048] FIG8 is a temperature variation curve of the inner side of the thermal / magnetic shielding composite structure in Example 1 of the present invention when the outer side contacts a 100° C. heat source for 0 to 5 minutes.

[0049] FIG9 is a schematic diagram of a magnetic field shielding effectiveness testing device for the thermal / magnetic shielding composite structure in Example 1 of the present invention.

[0050] FIG. 10 is a broadband magnetic field shielding effectiveness curve of the thermal / magnetic shielding composite structure in Example 1 of the present invention.

[0051] Numbers in the figure: 1 is a flexible thermal insulation composite material layer, 2 is a flexible high-frequency magnetic field shielding and heat dissipation composite material layer, 3 is a flexible low-frequency magnetic field shielding composite material layer, 4 is a flaky silver-coated nickel powder, 5 is a gallium-based liquid metal droplet, 6 is a flaky Sendust alloy powder, and 7 is a nickel nanowire powder. DETAILED DESCRIPTION

[0052] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following embodiments are implemented based on the technical solutions of the present invention, and provide detailed implementation methods and specific operating procedures. However, the protection scope of the present invention is not limited to the following embodiments.

[0053] Example 1

[0054] This embodiment provides a flexible thermal / magnetic shielding composite material for a Hall-type force sensor, comprising an outer thermal insulation functional layer and an inner low-frequency magnetic field shielding functional layer. A schematic cross-sectional structure diagram is shown in Figure 1. The outer thermal insulation functional layer is composed of three composite layers: from the outside to the inside, a flexible thermal insulation composite material layer 1 (length × width × thickness = 80 * 80 * 1 mm), a flexible high-frequency magnetic field shielding and heat dissipation composite material layer 2 (length × width × thickness = 80 * 80 * 0.5 mm), and a flexible thermal insulation composite material layer 1 (length × width × thickness = 80 × 80 × 1 mm). The inner low-frequency magnetic field shielding functional layer is made of a flexible low-frequency magnetic field shielding composite material and is therefore also referred to as a flexible low-frequency magnetic field shielding composite material layer 3 (length × width × thickness = 80 × 80 × 0.8 mm).

[0055] Specifically: The flexible thermal insulation composite material layer is made by simultaneously filling a silicone rubber matrix with fumed silica particles and expanded perlite particles, and using a foaming agent to produce a uniform microporous structure. The flexible high-frequency magnetic field shielding and heat dissipation composite material layer is made by filling a silicone rubber matrix with flaky silver-coated nickel powder filler and gallium-based liquid metal droplets surface-coated with 3-mercaptopropyltrimethoxysilane (A1891), and then aligning the filler. The flexible low-frequency magnetic field shielding composite material layer is made by filling a silicone rubber matrix with ferromagnetic nanowires (nickel nanowires) surface-modified with γ-aminopropyltriethoxysilane (KH-550) and flaky iron-silicon-aluminum alloy powder, and then aligning the magnetic conductive filler.

[0056] The thermal / magnetic shielding composite structure of this embodiment is manufactured according to the following steps:

[0057] Step 1: Prepare a flexible thermal insulation composite material layer

[0058] Weigh 1.5 g of expanded perlite particles (average particle size 25 μm), 1.5 g of fumed silica particles (average particle size 40 nm), 10 g of component A of two-component room temperature curing silicone rubber, 1 g of component B of two-component room temperature curing silicone rubber, 0.3 g of foaming agent H (N,N'-dinitrosopentamethylenetetramine), 0.15 g of foaming aid (pentaerythritol), 0.5 g of KH-550 silane coupling agent, and 8 g of anhydrous ethanol.

[0059] The weighed expanded perlite particles, fumed silica particles, and silane coupling agent were placed in anhydrous ethanol, stirred at room temperature under high-speed magnetic stirring for 1.5 hours, and then dried in an oven to obtain a surface-modified filler powder. The surface-modified filler powder was then mixed with the weighed blowing agent, foaming aid, and component A of a two-component room-temperature-curing silicone rubber. The mixture was then ultrasonically dispersed at 1500 W for 1.5 hours. Component B of the two-component room-temperature-curing silicone rubber was then added. Ultrasonic dispersion was continued for 15 minutes, and the mixture was quickly loaded into an aluminum molding mold and heated in an oven at 140°C for 7 hours for foaming and curing, yielding a 1 mm thick flexible thermal insulation composite material layer.

[0060] Step 2: Prepare a flexible high-frequency magnetic field shielding and heat dissipation composite material layer

[0061] Weigh 5 g of flaky silver-coated nickel powder (average diameter 25 μm, thickness 600 nm), 1.5 g of gallium liquid metal, 0.4 g of 3-mercaptopropyltrimethoxysilane, 10 g of component A of two-component room temperature curing silicone rubber, 1 g of component B of two-component room temperature curing silicone rubber, 0.5 g of KH-550 silane coupling agent, and 15 g of anhydrous ethanol.

[0062] The weighed gallium-based liquid metal, 3-mercaptopropyltrimethoxysilane and 7 g of anhydrous ethanol solution were mixed, and then ultrasonically dispersed at a power of 1500 W for 2 hours to obtain gallium-based liquid metal droplets with a surface coating treatment with 3-mercaptopropyltrimethoxysilane.

[0063] The weighed flaky silver-coated nickel powder and silane coupling agent were placed in 8 g of anhydrous ethanol, ultrasonically dispersed at a power of 1500 W for 1.5 hours, and then dried in an oven to obtain a surface-modified flaky silver-coated nickel powder.

[0064] The surface-modified flaky silver-coated nickel powder, the gallium-based liquid metal droplets coated with 3-mercaptopropyltrimethoxysilane, and the weighed component A of the two-component room-temperature curing silicone rubber are mixed and placed in a horizontal ball mill. After stirring at room temperature for 1.5 hours, the weighed component B of the two-component room-temperature curing silicone rubber is added, and stirring is continued for 10 minutes. The resulting slurry is vacuum-evacuated in a vacuum treatment furnace to remove bubbles, and then injected into an aluminum molding mold and placed in a magnetic field with a magnetic induction intensity of 1 T parallel to the magnetic field. The sample is rotated 90 degrees every 2 minutes until the slurry loses fluidity. The sample is then placed in the magnetic field for another 15 hours, taken out, and heated in an oven at 150°C for 6 hours to completely cure it, thereby obtaining a 0.5 mm thick flexible high-frequency magnetic field shielding and heat dissipation composite material layer.

[0065] Step 3: Prepare a flexible low-frequency magnetic field shielding composite material layer

[0066] Weigh 3 g of nickel nanowire powder (length 10 μm, diameter 100 nm), 12 g of flaky sendust powder (average diameter 80 μm, thickness 0.5 μm), 10 g of component A of two-component room temperature curing silicone rubber, 1 g of component B of two-component room temperature curing silicone rubber, 0.6 g of KH-550 silane coupling agent, 0.3 g of dispersant polyacrylamide (PAM), and 8 g of anhydrous ethanol.

[0067] The weighed nickel nanowire powder, flaky Sendust alloy powder and silane coupling agent were placed in an anhydrous ethanol solution, ultrasonically dispersed at a power of 1500 W for 1.5 hours, and then dried in an oven to obtain a mixed filler surface-modified with a silane coupling agent.

[0068] The mixed filler surface-modified with a silane coupling agent is mixed with the weighed component A and dispersant of the two-component room-temperature curing silicone rubber and placed in a horizontal ball mill. After stirring at room temperature for 1.5 hours, the weighed component B of the two-component room-temperature curing silicone rubber is added, and stirring is continued for 10 minutes. The resulting slurry is vacuum-evacuated in a vacuum treatment furnace to remove bubbles, and then injected into an aluminum molding mold. Then, it is placed in a magnetic field with a magnetic induction intensity of 1 T parallel to the magnetic field direction, and the sample is rotated 90 degrees every 2 minutes until the slurry loses fluidity. The sample is then placed in the magnetic field for 15 hours, taken out, and heated in an oven at 150°C for 6 hours to completely cure it, thereby obtaining a flexible low-frequency magnetic field shielding composite material layer with a thickness of 0.8 mm.

[0069] Step 4: Prepare a thermal / magnetic shielding composite structure for a flexible Hall-type force sensor

[0070] The surfaces of the composite material layers obtained in steps 1, 2 and 3 are coated with a primer treatment agent and dried, and then coated with a silicone adhesive. Subsequently, the composite material layers are stacked in order from the outside to the inside, namely, a flexible thermal insulation composite material layer, a flexible high-frequency magnetic field shielding and heat dissipation composite material layer, a flexible thermal insulation composite material layer, and a flexible low-frequency magnetic field shielding composite material layer. The layers are placed in an oven and heated at 150°C for 25 minutes to complete curing, thereby obtaining the thermal / magnetic shielding composite structure for the flexible Hall-type force sensor.

[0071] Figure 2 is a schematic diagram of the filler alignment treatment process in steps 2 and 3 of Example 1 of the present invention. The semi-cured uniform mixed slurry is placed in a uniform static magnetic field formed by electromagnets on both sides, with the magnetic field direction parallel to the in-plane direction of the composite material. The sample is rotated 90 degrees every two minutes until the slurry loses fluidity. At this point, the flaky or linear soft magnetic powder fillers with anisotropic morphology in the composite material are oriented parallel to the magnetic field direction.

[0072] Figure 3 shows the filler system architecture of the flexible high-frequency magnetic field shielding and heat dissipation composite material layer (Figure 3(a)) and the flexible low-frequency magnetic field shielding composite material layer (Figure 3(b)) in Example 1 of the present invention before and after oriented arrangement. The distribution of the various fillers in the mixed slurry, including flaky silver-coated nickel powder 4, gallium-based liquid metal droplets 5, flaky Sendust powder 6, and nickel nanowire powder 7, is shown in the absence of a magnetic field (left) and in the presence of a magnetic field (right). In the absence of a magnetic field, the various fillers are uniformly dispersed and randomly arranged. In the presence of a magnetic field, the anisotropic soft magnetic fillers, including flaky silver-coated nickel powder 4, flaky Sendust powder 6, and nickel nanowire powder 7, are rapidly magnetized and oriented along the magnetic field. The oriented flaky or linear soft magnetic fillers increase the density of the network connections between fillers in the in-plane direction of the composite material layer, improving the in-plane electrical / thermal conductivity and magnetic permeability of the flexible high-frequency magnetic field shielding and heat dissipation composite layer and the flexible low-frequency magnetic field shielding composite layer, respectively.

[0073] Figure 4 shows the relationship between the in-plane thermal conductivity of a flexible high-frequency magnetic field shielding and heat dissipation composite layer and filler mass fraction (the filler mass fraction refers to the ratio of the mass of the functional filler to the mass of the composite material). The three filler systems are: single flaky silver-coated nickel powder; a mixture of flaky silver-coated nickel powder and gallium liquid metal droplets (mass ratio of 10:3); and an aligned mixture of flaky silver-coated nickel powder and gallium liquid metal droplets (mass ratio of 10:3). It can be seen that the in-plane thermal conductivity of the composite layer increases with increasing total filler volume fraction. The combination of flaky silver-coated nickel powder and gallium liquid metal droplets exhibits higher thermal conductivity than a single flaky silver-coated nickel powder. The aligned mixture of flaky silver-coated nickel powder and gallium liquid metal droplets exhibits higher thermal conductivity than the unaligned composite. This demonstrates the beneficial effects of the solid / liquid combined filler system design and the aligned arrangement of the flaky silver-coated nickel powder on improving the in-plane thermal conductivity of the composite.

[0074] Figure 5 shows the relationship between the in-plane magnetic permeability of a flexible low-frequency magnetic field shielding composite layer and filler mass fraction. The three filler systems are: single flaky Sendust alloy powder; mixed flaky Sendust alloy powder and nickel nanowire powder (mass ratio of 4:1); and aligned mixed flaky Sendust alloy powder and nickel nanowire powder (mass ratio of 4:1). It can be seen that the in-plane magnetic permeability of the composite layer increases with increasing filler volume fraction. The mixed flaky Sendust alloy powder and nickel nanowire powder has higher magnetic permeability than single flaky Sendust alloy powder. The aligned mixed flaky Sendust alloy powder and nickel nanowire powder has higher magnetic permeability than the unaligned version. This demonstrates the beneficial effects of a multi-dimensional, synergistic filler system design combining one-dimensional and two-dimensional design and soft magnetic alignment treatment on improving the in-plane magnetic permeability of the composite.

[0075] Figure 6 is a schematic diagram of the heat shielding principle of the outer thermal insulation layer of the present invention when it contacts a heat source. The outer thermal insulation layer is composed of three layers of composite materials: from the outside to the inside, a flexible thermal insulation composite material layer 1 with low thermal conductivity, a flexible high-frequency magnetic field shielding and heat dissipation composite material layer 2 with high in-plane thermal conductivity, and a flexible thermal insulation composite material layer 1 with low thermal conductivity. When in contact with a heat source, the first flexible thermal insulation composite material layer blocks most of the heat from being conducted inward. The flexible high-frequency magnetic field shielding and heat dissipation composite material layer quickly transfers the localized heat that has passed through the first flexible thermal insulation composite layer inward and dissipates it, preventing heat accumulation in a localized area. The second flexible thermal insulation composite material layer further reduces the small amount of heat that is conducted inward, achieving a highly effective heat shielding effect.

[0076] After testing, in this embodiment, the thermal conductivity of the flexible thermal insulation composite material layer is 0.04W·m -1 ·K -1The tensile strength and elongation at break are 4MPa and 30% respectively. The volume resistivity of the flexible high-frequency magnetic field shielding and heat dissipation composite material layer is 105Ω·cm, and the in-plane thermal conductivity is 4W·m -1 ·K -1 , tensile strength and elongation at break are 4MPa and 50% respectively. The in-plane magnetic permeability of the flexible low-frequency magnetic field shielding composite layer is 110H·m -1 , the tensile strength and elongation at break are 4MPa and 30% respectively.

[0077] Figure 7 is a schematic diagram of a device for testing the temperature shielding effectiveness of a thermal / magnetic shielding composite structure for a flexible Hall-type force sensor in Example 1 of the present invention. A semiconductor refrigeration sheet and a temperature control module are used as a controllable contact heat source, and a temperature sensor is used to detect real-time temperature changes on the other side of the shielding material.

[0078] Figure 8 compares the thermal shielding effectiveness of the outer thermal insulation layer in the thermal / magnetic shielding composite structure of Example 1 of the present invention. The three curves in the figure represent the temperature changes on the other side of a 2.5 mm thick unfilled silicone rubber layer, a 2.5 mm thick flexible thermal insulation composite material layer prepared according to the method of Step 1 of Example 1, and the outer thermal insulation layer of the sandwich structure prepared in Example 1 after exposure to a 100°C heat source. As can be seen from the figure, both the flexible thermal insulation composite layer and the sandwich structure significantly reduce the heat conduction rate between the inside and outside. The outer thermal insulation layer of the sandwich structure prepared in Example 1 exhibits the best thermal insulation effect, maintaining the inner temperature below 33°C for 5 minutes.

[0079] Figure 9 is a schematic diagram of the magnetic field shielding effectiveness testing apparatus for the thermal / magnetic shielding composite structure for the flexible Hall-type force sensor in Example 1 of the present invention. The magnetic shielding cavity is made of ultra-high magnetic permeability Permalloy, and one end of the cavity is sealed with a prepared shielding material sample. An electromagnet and an alternating current source are used to apply a broadband magnetic field to the outer surface of the shielding material, and a magnetic field Hall sensor is used to detect the magnetic induction intensity penetrating into the cavity. Static magnetic field shielding tests show that the thermal / magnetic shielding composite structure obtained in Example 1 can achieve a shielding effectiveness of 30 dB against static magnetic fields.

[0080] Figure 10 illustrates the magnetic shielding effect of the thermal / magnetic shielding composite structure obtained in Example 1 of the present invention. The curves in the figure represent the shielding effectiveness of the thermal / magnetic shielding composite structure against magnetic fields of varying frequencies, expressed in decibels (dB). As can be seen from the figure, the composite structure exhibits high shielding effectiveness against low-frequency magnetic fields in the 1kHz to 200kHz range, exceeding 33dB. For high-frequency magnetic fields above 200kHz, the shielding effectiveness is even higher, reaching 48dB.

[0081] The above-described embodiments merely illustrate several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A thermal / magnetic shielding composite structure for a flexible Hall force sensor, characterized in that: The thermal / magnetic shielding composite structure is composed of an outer thermal insulation functional layer and an inner low-frequency magnetic field shielding functional layer; the outer thermal insulation functional layer is composed of three layers of composite materials, which are, from the outside to the inside, a flexible thermal insulation composite material layer, a flexible high-frequency magnetic field shielding and heat dissipation composite material layer, and a flexible thermal insulation composite material layer; the inner low-frequency magnetic field shielding functional layer is a flexible low-frequency magnetic field shielding composite material layer; The flexible heat-insulating composite material layer is made by simultaneously filling fumed silica particles and expanded perlite particles into a silicone rubber matrix based on a foaming process and a thermal curing process; The flexible high-frequency magnetic field shielding and heat dissipation composite material layer is made based on a thermal curing process by filling a silicone rubber matrix with flaky silver-coated nickel powder filler and gallium-based liquid metal droplets treated with a 3-mercaptopropyltrimethoxysilane surface coating. The flexible low-frequency magnetic field shielding composite material layer is made based on a thermal curing process by filling ferromagnetic nanowires and flaky Sendust alloy powders surface-modified by a silane coupling agent into a silicone rubber matrix.

2. The thermal / magnetic shielding composite structure for a flexible Hall force sensor according to claim 1, characterized in that: The thermal conductivity of the flexible heat-insulating composite material layer is not higher than 0.04 W·m -1 ·K -1 , tensile strength is not less than 4MPa, and elongation at break is not less than 30%.

3. The thermal / magnetic shielding composite structure for a flexible Hall force sensor according to claim 1, characterized in that: The volume resistivity of the flexible high-frequency magnetic field shielding and heat dissipation composite material layer is not higher than 105Ω·cm, and the thermal conductivity in the plane direction is not lower than 4W·m -1 ·K -1 , tensile strength is not less than 4MPa, and elongation at break is not less than 50%.

4. The thermal / magnetic shielding composite structure for a flexible Hall force sensor according to claim 1, characterized in that: The magnetic permeability of the flexible low-frequency magnetic field shielding composite material layer is not less than 110 H·m -1 , tensile strength is not less than 4MPa, and elongation at break is not less than 30%.

5. A method for preparing a thermal / magnetic shielding composite structure for a flexible Hall force sensor as claimed in any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1: Prepare a flexible thermal insulation composite material layer Weigh the following raw materials in parts by weight: 10-20 parts of expanded perlite particles with a particle size range of 20-30 μm, 10-20 parts of fumed silica particles with a particle size range of 30-50 nm, 100 parts of component A of two-component room temperature curing silicone rubber, 10 parts of component B of two-component room temperature curing silicone rubber, 1-4 parts of N,N'-dinitrosopentamethylenetetramine as a foaming agent, 1-2 parts of pentaerythritol as a foaming aid, 5-10 parts of silane coupling agent, and 50-100 parts of anhydrous ethanol; The expanded perlite particles, fumed silica particles and silane coupling agent weighed are placed in anhydrous ethanol, magnetically stirred at room temperature for 1 to 2 hours, and then placed in an oven for drying to obtain a surface-modified filler powder; the surface-modified filler powder is mixed with the weighed foaming agent, foaming aid and component A of the two-component room temperature curing silicone rubber, and then ultrasonically dispersed at a power of 1000 to 2000 W for 1 to 2 hours, and then the weighed component B of the two-component room temperature curing silicone rubber is added. After continuing ultrasonic dispersion for 5 to 20 minutes, the mixture is loaded into an aluminum molding mold and placed in an oven for heating at 130 to 150° C. for 5 to 8 hours for foaming and curing to obtain a flexible thermal insulation composite material layer; Step 2: Prepare a flexible high-frequency magnetic field shielding and heat dissipation composite material layer Weigh the following raw materials in parts by weight: 50-70 parts of flaky silver-coated nickel powder, 10-20 parts of gallium-based liquid metal, 3-7 parts of 3-mercaptopropyltrimethoxysilane, 100 parts of component A of two-component room temperature curing silicone rubber, 10 parts of component B of two-component room temperature curing silicone rubber, 3-7 parts of silane coupling agent, and 100-150 parts of anhydrous ethanol; The weighed gallium-based liquid metal, 3-mercaptopropyltrimethoxysilane and 50-100 parts of anhydrous ethanol are mixed, and ultrasonically dispersed at a power of 1000-2000 W for 1-3 hours to obtain gallium-based liquid metal droplets that are surface-coated with 3-mercaptopropyltrimethoxysilane; The weighed flaky silver-coated nickel powder and the silane coupling agent are placed in the remaining anhydrous ethanol, and ultrasonically dispersed at a power of 1000 to 2000 W for 1 to 2 hours, and then placed in an oven for drying to obtain a flaky silver-coated nickel powder after surface modification; The surface-modified flaky silver-coated nickel powder, the gallium-based liquid metal droplets treated with 3-mercaptopropyltrimethoxysilane surface coating, and the weighed component A of the two-component room-temperature curing silicone rubber are mixed and placed in a horizontal ball mill, stirred at room temperature for 1 to 2 hours, and then the component B of the two-component room-temperature curing silicone rubber is added, and the stirring is continued for 5 to 20 minutes; the obtained slurry is vacuum-evacuated in a vacuum treatment furnace to remove bubbles, and then injected into an aluminum molding mold, and placed in a magnetic field with a magnetic induction intensity of 0.5 to 1.5 T parallel to the magnetic field direction, and the sample is rotated 90 degrees every 2 to 3 minutes until the slurry loses fluidity, and then the sample is placed in the magnetic field for 15 to 20 hours, taken out, and heated in an oven at 100 to 150° C. for 5 to 10 hours to fully cure it, thereby obtaining the flexible high-frequency magnetic field shielding and heat dissipation composite material layer; Step 3: Prepare a flexible low-frequency magnetic field shielding composite material layer Weigh the following raw materials by weight: 20-50 parts of ferromagnetic nanowire powder, 100-150 parts of flaky iron-silicon-aluminum alloy powder, 100 parts of component A of two-component room temperature curing silicone rubber, 10 parts of component B of two-component room temperature curing silicone rubber, 4-10 parts of silane coupling agent, 1-5 parts of dispersant, and 50-100 parts of anhydrous ethanol; The weighed ferromagnetic nanowire powder, flaky iron-silicon-aluminum alloy powder and silane coupling agent are placed in anhydrous ethanol, ultrasonically dispersed at a power of 1000 to 2000 W for 1 to 2 hours, and then placed in an oven for drying to obtain a mixed filler surface-modified with a silane coupling agent; The mixed filler surface-modified by the silane coupling agent is mixed with the weighed component A and dispersant of the two-component room-temperature-curing silicone rubber, and then put into a horizontal ball mill. After stirring at room temperature for 1 to 2 hours, the component B of the two-component room-temperature-curing silicone rubber is added, and stirring is continued for 5 to 20 minutes. The obtained slurry is vacuum-evacuated in a vacuum treatment furnace to remove bubbles, and then injected into an aluminum molding mold, and then placed in a magnetic field with a magnetic induction intensity of 0.5 to 1.5 T parallel to the magnetic field direction, and the sample is rotated 90 degrees every 2 to 3 minutes until the slurry loses fluidity, and then the sample is placed in the magnetic field for 15 to 20 hours, taken out, and heated in an oven at 100 to 150° C. for 5 to 10 hours to fully cure it, thereby obtaining the flexible low-frequency magnetic field shielding composite material layer; Step 4: Prepare a thermal / magnetic shielding composite structure for a flexible Hall force sensor The surfaces of the composite material layers obtained in step 1, step 2 and step 3 are coated with a primer treatment agent and dried, and then coated with a silicone adhesive. Subsequently, the composite material layers are stacked in sequence from the outside to the inside, namely, a flexible thermal insulation composite material layer, a flexible high-frequency magnetic field shielding and heat dissipation composite material layer, a flexible thermal insulation composite material layer, and a flexible low-frequency magnetic field shielding composite material layer, and are placed in an oven and heated at 100 to 200° C. for 20 to 30 minutes to complete curing, thereby obtaining the thermal / magnetic shielding composite structure for the flexible Hall force sensor.

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