A flexible magnetic sensor array stretchable in all directions and a method for manufacturing the same

Abstract

The application provides a flexible magnetic sensor array and a preparation method thereof, and the flexible magnetic sensor array comprises a high-elasticity substrate film layer, an array rigid island layer and a magnetic sensor layer, the array rigid island layer comprises a plurality of rigid islands arranged in an array on the high-elasticity substrate film layer, the magnetic sensor layer comprises a magnetic sensor arranged on each rigid island, each rigid island draws a plurality of elastic electrodes from the magnetic sensor, all the elastic electrodes are arranged on the high-elasticity substrate film layer in a matched mode and are drawn to the edge of the high-elasticity substrate film layer, the Young's modulus of the magnetic sensor is greater than the Young's modulus of the rigid island, and the Young's modulus of the rigid island is greater than the Young's modulus of the high-elasticity substrate film layer. The high-elasticity substrate film layer, the array rigid island layer and the magnetic sensor layer of the application have a modulus gradient structure and have a strain isolation effect under deformation, so that the high-elasticity substrate film layer bears most of the strain and the original performance of the magnetic sensor is ensured.

Description

Technical Field

[0001] This invention relates to the field of flexible magnetic sensor technology, and more specifically, to a flexible magnetic sensor array that can be stretched in all directions and its fabrication method. Background Technology

[0002] With the rapid development of the Internet of Things (IoT) and wearable devices, flexible electronics technology has attracted much attention. Flexible electronic materials and devices, with their stretchability, biocompatibility, durability, and miniaturization, can be applied to various complex surfaces, including human skin, allowing functional materials to be reshaped as needed after manufacturing. Therefore, flexible electronics are widely used in flexible circuit boards, supercapacitors, biomedicine, smart textiles, and electronic skin, among other fields.

[0003] Flexible magnetic sensor devices can realize a series of unique functions, including positioning and navigation, stress detection, real-time monitoring and non-contact interaction, and have become an important field in flexible electronic devices. Its core structure is a magnetic thin film.

[0004] Traditional magnetic thin films are fabricated on rigid silicon substrates. The stretchability of such devices rarely exceeds the inherent ductility of the material, falling far short of the strain requirements of stretchable magnetoelectronics. To address this issue, the most common method is to directly deposit rigid multilayer films (with curved patterns) onto flexible substrates using a direct deposition method, resulting in flexible spin valve magnetic sensors with a degree of flexibility. However, because the magnetic thin film material is rigid, the modulus mismatch between it and the flexible substrate during stretching easily leads to surface defects, preventing effective improvement in the film's stretchability and stability. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a flexible magnetic sensor array that can be stretched in all directions, thereby solving the problem that defects will be generated on the surface of the thin film of the magnetic sensor when it is stretched, resulting in a decrease in performance.

[0006] The technical solution adopted by the present invention to solve the above problems is as follows: a flexible magnetic sensor array that can be stretched in all directions, comprising a highly elastic substrate thin film layer, an array of rigid island layers, and a magnetic sensor layer. The array of rigid island layers comprises a plurality of rigid islands arranged in an array on the highly elastic substrate thin film layer. The magnetic sensor layer comprises a magnetic sensor disposed on each rigid island. Each rigid island leads out a plurality of elastic electrodes from the magnetic sensor. All the elastic electrodes are attached to the highly elastic substrate thin film layer and lead out to the edge of the highly elastic substrate thin film layer. The Young's modulus of the magnetic sensor is greater than the Young's modulus of the rigid island, and the Young's modulus of the rigid island is greater than the Young's modulus of the highly elastic substrate thin film layer.

[0007] Compared with the prior art, the advantages of the present invention are as follows: the high elastic substrate thin film layer, the array rigid island layer and the magnetic sensor layer present a modulus gradient structure, which can have a strain isolation effect under deformations such as stretching, bending and torsion in various directions. This allows the high elastic substrate thin film layer to bear most of the strain, while the magnetic sensor on the array rigid island layer maintains its original performance, greatly improving the application range and service life of the magnetic sensor; the array arrangement makes it more sensitive.

[0008] Preferably, the material of the highly elastic substrate thin film layer is PDMS, PU or Ecofelx, the material of the rigid island is polyimide or photoresist, and the material of the elastic electrode is liquid metal or silver nanowires.

[0009] The technical effects achieved by adopting this technical solution are as follows: the high elastic substrate thin film layer is made of materials with low Young's modulus, which makes it easy to withstand most of the strain during deformation such as stretching, bending and twisting; the rigid island is made of materials with high Young's modulus, which serves as a transition to ensure that the magnetic sensor can maintain its original performance; the elastic electrode is made of a stretchable conductor material whose resistance does not change significantly under a certain stretch, ensuring that the wire will not break under stretching and the resistance will not change significantly.

[0010] Preferably, the surface roughness of both the highly elastic substrate thin film layer and the rigid island is less than 1 nanometer.

[0011] The technical effects achieved by adopting this technical solution are: making the surface roughness smaller facilitates the bonding between layers and improves the stability of the connection between layers; at the same time, it also reduces the roughness of the magnetic thin film of the magnetic sensor layer connected to it, thereby improving the magnetic sensing performance.

[0012] Preferably, both the rigid island and the magnetic sensor are circular or polygonal.

[0013] The technical effect achieved by adopting this technical solution is that the rigid island and magnetic sensor are designed into specific shapes, which facilitates mass production.

[0014] Another technical solution adopted by the present invention to solve the above problems is: a method for fabricating a flexible magnetic sensor array that can be stretched in all directions, including a forward fabrication method and a reverse fabrication method. The forward fabrication method is carried out sequentially according to steps S1, S2, S3, S4 and S5, and the reverse fabrication method is carried out sequentially according to steps S1, S4, S3, S2 and S5; wherein

[0015] S1. Provide a temporary substrate and clean it;

[0016] S2. Fabrication of a high-elasticity substrate thin film layer: Mix the precursor of the high-elasticity substrate and the curing agent evenly according to a preset weight ratio and spin-coat them onto the upper layer. After drying and curing, a high-elasticity substrate thin film layer is obtained.

[0017] S3. Fabrication of an array of rigid islands: Spin-coat photoresist onto the upper layer, dry and cure it, and then use a photolithography plate with a specific pattern to perform photolithography to obtain an array of rigid islands. Then, perform development, fixing, drying and curing in sequence to obtain several rigid islands.

[0018] S4. Fabrication of the magnetic sensor layer: Several magnetic thin films with spin valve structures are grown on the previous layer by magnetron sputtering to obtain the magnetic sensor layer.

[0019] S5. Each rigid island in the array of rigid islands has several elastic electrodes led out from the corresponding magnetic sensor, and the led-out elastic electrodes are attached to the highly elastic substrate thin film layer.

[0020] Compared with the prior art, the advantages of the present invention are: the high elastic substrate thin film layer, the array rigid island layer and the magnetic sensor layer present a modulus gradient structure, which can have a strain isolation effect under deformations such as stretching, bending and torsion in various directions, so that the high elastic substrate thin film layer bears most of the strain, while the magnetic sensor on the array rigid island layer maintains its original performance, which greatly improves the application range and service life of the magnetic sensor.

[0021] Preferably, in both the forward fabrication method and the reverse fabrication method, step S1 includes the following steps: S11, providing a silicon wafer as a temporary substrate layer and cleaning the surface of the silicon wafer using plasma; S12, spin-coating a dextran solution of a specific concentration onto the cleaned silicon wafer surface and baking to obtain a sacrificial layer.

[0022] The technical effect achieved by adopting this technical solution is that by using a silicon wafer as a temporary substrate layer and then setting a sacrificial layer on it, it is easier to separate the highly elastic substrate thin film layer, the array rigid island layer and the magnetic sensor layer after they are fabricated.

[0023] Preferably, in the forward fabrication method, a cleaning step is provided after step S2 and before step S3: the surface of the highly elastic substrate thin film layer is cleaned using plasma.

[0024] The technical effects achieved by adopting this technical solution are as follows: by cleaning, the cleanliness is improved, and the surface wettability of the high-elasticity substrate thin film layer is also improved, which can improve the production yield.

[0025] Preferably, in both the forward and reverse fabrication methods, in step S3, after spin-coating the photoresist, the spin-drying process is carried out at a specific rotation speed for a period of time.

[0026] The technical effect achieved by adopting this technical solution is: by idling at a specific speed for a period of time, the edge effect is reduced and the flatness of the photoresist thickness after spin coating is improved.

[0027] Preferably, in the forward fabrication method, step S4 includes the following steps: dissolving the sacrificial layer with deionized water, removing the temporary substrate layer and drying it, fixing it on the array rigid island layer using a mask with a corresponding pattern, and fabricating a magnetic thin film with a spin valve structure on each rigid island by magnetron sputtering to obtain a magnetic sensor layer; in the reverse fabrication method, step S4 includes the following steps: fabricating a plurality of magnetic thin films with spin valve structures on the sacrificial layer by magnetron sputtering to obtain a magnetic sensor layer, and a stripping step is provided after step S2 and before step S5: dissolving the sacrificial layer with deionized water, removing the temporary substrate layer and drying it.

[0028] The technical effect achieved by adopting this technical solution is that after removing the temporary substrate layer and dissolving the sacrificial layer, a magnetic sensor with a modulus gradient structure can be obtained.

[0029] Preferably, in the reverse fabrication method, step S1 includes the following steps: providing a mica sheet as a temporary substrate layer, cleaning the mica sheet using plasma; and peeling off the mica sheet layer by layer using adhesive tape after step S2 and before step S5.

[0030] The technical effects achieved by adopting this technical solution are as follows: using mica sheets as a temporary substrate layer eliminates the need for a sacrificial layer, and finally, the mica sheets can be peeled off layer by layer, making the design convenient. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of a flexible magnetic sensor array that can be stretched in all directions according to the present invention.

[0032] Figure labeling: 1-Highly elastic substrate thin film layer; 2-Rigid island; 3-Magnetic sensor; 4-Elastic electrode. Detailed Implementation

[0033] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0034] like Figure 1 As shown, this embodiment relates to a flexible magnetic sensor array that can be stretched in all directions, including a highly elastic substrate thin film layer 1, an array rigid island layer, and a magnetic sensor layer.

[0035] The array rigid island layer includes several rigid islands 2 arranged in an array on the high elastic substrate thin film layer 1. The magnetic sensor layer includes a magnetic sensor 3 disposed on each rigid island 2. Several elastic electrodes 4 are led out from each rigid island 2 from the magnetic sensor 3. All elastic electrodes 4 are attached to the high elastic substrate thin film layer 1 and led out to the edge of the high elastic substrate thin film layer 1.

[0036] In this embodiment, the Young's modulus of the magnetic sensor 3 is greater than that of the rigid island 2, and the Young's modulus of the rigid island 2 is greater than that of the highly elastic substrate thin film layer 1.

[0037] The high-elasticity substrate thin film layer 1, the array rigid island layer, and the magnetic sensor layer present a modulus gradient structure, which can still have a strain isolation effect under deformations such as stretching, bending, and torsion in various directions. This allows the high-elasticity substrate thin film layer 1 to bear most of the strain, while the magnetic sensor 3 on the array rigid island layer maintains its original performance, greatly improving the application range and service life of the magnetic sensor 3; the array arrangement also makes it more sensitive.

[0038] Among them, the material of the highly elastic substrate thin film layer 1 is polydimethylsiloxane (PDMS), polyurethane (PU) or Ecofelx, the material of the rigid island 2 is PI (polyimide) or photoresist, and the material of the elastic electrode 4 is liquid metal or silver nanowires.

[0039] The high-elasticity substrate thin film layer 1 is made of materials with low Young's modulus, which makes it easy to withstand most of the strain during deformations such as stretching, bending and twisting; the rigid island 2 is made of materials with high Young's modulus, which serves as a transition to ensure that the magnetic sensor 3 can maintain its original performance; the elastic electrode 4 is made of a stretchable conductor material whose resistance does not change significantly under certain stretching, ensuring that it will not break under stretching and that its resistance will not change significantly.

[0040] In this embodiment, the surface roughness of both the highly elastic substrate thin film layer 1 and the rigid island 2 is less than 1 nanometer. A smaller surface roughness facilitates adhesion between layers and improves the stability of the connection between layers; it also reduces the roughness of the magnetic thin film of the magnetic sensor layer connected to it, thereby improving the magnetic sensing performance.

[0041] Both the rigid island 2 and the magnetic sensor 3 are circular or polygonal. Designing the rigid island 2 and the magnetic sensor 3 with specific shapes facilitates mass production. The external structures of the rigid island 2 and the magnetic sensor 3 need to match, and their cross-sectional areas should be identical to ensure that they do not detach under tensile deformation.

[0042] Each rigid island 2 has four elastic electrodes 4 leading out from the corresponding magnetic sensor 3.

[0043] Example 1

[0044] This embodiment relates to a method for fabricating a flexible magnetic sensor array that can be stretched in all directions, including a forward fabrication method, which includes the following steps:

[0045] Step 1: Provide a temporary substrate and clean it. Specifically, this includes the following steps:

[0046] Step 11: Provide a silicon wafer as a temporary substrate, place the silicon wafer into a plasma cleaner, evacuate the vacuum, introduce oxygen, and bombard the surface of the silicon wafer with oxygen plasma for 2 minutes under the action of an electromagnetic field of 150W, thereby cleaning and activating the surface of the silicon wafer.

[0047] Step 12: Place the cleaned silicon wafer on a spin coater and spin coat the surface of the silicon wafer with a concentration of 1% to 10% dextran solution at a speed of 8500 rpm. First, place it on a heating stage at 80°C and bake for 1 minute, then place it on a heating stage at 180°C and bake for 30 minutes to obtain a sacrificial layer with a thickness of less than 1 micrometer.

[0048] By using a silicon wafer as a temporary substrate layer and then setting a sacrificial layer on it, it is easier to prepare a highly elastic substrate thin film layer 1.

[0049] Step 2: Fabrication of high elastic substrate thin film layer 1: Mix the precursor of the high elastic substrate and the curing agent evenly according to the preset weight ratio and spin coat them onto the previous layer. After drying and curing, the high elastic substrate thin film layer 1 is obtained.

[0050] Specifically, the process includes the following steps: the precursor of the high-elasticity substrate and the curing agent are mixed evenly at a weight ratio of 10:1, spin-coated on the sacrificial layer at a speed of 1200 rpm, and then cured in a 60°C forced-air oven for 12 hours to obtain the high-elasticity substrate layer.

[0051] Following this step, there is a cleaning step 21: the prepared sample is placed in a plasma cleaner, a vacuum is drawn, oxygen is introduced, and under the action of a 300W electromagnetic field, oxygen plasma bombards the surface of the high elastic substrate thin film layer 1 for 5s, thereby activating the surface of the high elastic substrate thin film layer 1.

[0052] Cleaning improves cleanliness and surface wettability of the high-elasticity substrate thin film layer 1, thereby increasing the fabrication yield. The precursor material for the high-elasticity substrate is polydimethylsiloxane (PDMS).

[0053] Step 3: Fabrication of the array of rigid islands: Photoresist is spin-coated onto the high-elasticity substrate thin film layer 1, dried and cured, and then photolithography is performed using a photolithography plate with a specific pattern to obtain the array of rigid islands. The process then involves development, fixing, and drying / curing to obtain several rigid islands 2. Specifically, the steps are as follows:

[0054] The prepared sample was placed on a spin coater and PI photoresist was spin-coated on the high elastic substrate thin film layer 1 at a speed of 1500 rpm. Then, it was rotated at 8000 rpm for 1 second to reduce edge effect and improve the flatness of the photoresist thickness after spin coating.

[0055] Place it on a 90℃ heating plate for 9 minutes to soften, then place it on a 50℃ heating plate for 30 seconds to bake.

[0056] After standing at room temperature for 5 minutes, use a photoresist plate with a circular or polygonal pattern.

[0057] The sample was immersed in NMD solution and shaken for about 90 seconds for development, then shaken in deionized water for about 5 seconds for fixing, and finally dried with nitrogen.

[0058] Place the sample in a 200℃ forced-air oven to cure for 90 minutes, away from light.

[0059] Step 4: Fabrication of the magnetic sensor layer: Several magnetic thin films with spin valve structures are grown on the array of rigid island layers by magnetron sputtering to obtain the magnetic sensor layer.

[0060] Specifically, the steps include: dissolving the sacrificial layer with deionized water, removing the temporary substrate layer and drying it with nitrogen, fixing it on the array rigid island layer using a mechanical mask with a corresponding pattern, and growing the magnetic sensor 3 with a spin valve structure in the defined rigid island 2 region by magnetron sputtering to obtain the magnetic sensor layer.

[0061] After this step, the sacrificial layer is dissolved using deionized water, and the temporary substrate layer is removed to obtain the magnetic sensor 3 with a modulus gradient structure.

[0062] Step 5: Each rigid island 2 in the array rigid island layer leads out several elastic electrodes 4 from the corresponding magnetic sensor 3, and attaches the led-out elastic electrodes 4 to the highly elastic substrate thin film layer 1.

[0063] Specifically, the steps include: using liquid metal or silver nanowires to lead out four elastic electrodes 4 from the magnetic sensor 3 on each rigid island 2, connecting them to platinum wires, encapsulating them with PDMS, and then detecting the device performance.

[0064] In this embodiment, the high-elasticity substrate thin film layer 1, the array rigid island layer, and the magnetic sensor layer present a modulus gradient structure, which can still have a strain isolation effect under deformations such as stretching, bending, and torsion in various directions. This allows the high-elasticity substrate thin film layer 1 to bear most of the strain, while the magnetic sensor 3 on the array rigid island layer maintains its original performance, greatly improving the application scenarios and service life of the magnetic sensor 3.

[0065] The flexible magnetic sensor 3 prepared in this embodiment can be stretched in all directions. Its GMR performance can reach 6.2%. The process is simple and precise. The sample volume is small. It has good stretchability, high stability and high sensitivity.

[0066] Example 2

[0067] This embodiment relates to a method for fabricating a flexible magnetic sensor array that can be stretched in all directions, including a reverse fabrication method, which includes the following steps:

[0068] Step 1: Provide a temporary substrate and clean it. Specifically, this includes the following steps:

[0069] Step 11: Provide a silicon wafer as a temporary substrate, place the silicon wafer into a plasma cleaner, evacuate the vacuum, introduce oxygen, and bombard the surface of the silicon wafer with oxygen plasma for 2 minutes under the action of an electromagnetic field of 150W, thereby cleaning and activating the surface of the silicon wafer.

[0070] Step 12: Place the cleaned silicon wafer on a spin coater and spin coat the surface of the silicon wafer with a concentration of 1% to 10% dextran solution at a speed of 8500 rpm. First, place it on a heating stage at 80°C and bake for 1 minute, then place it on a heating stage at 180°C and bake for 30 minutes to obtain a sacrificial layer with a thickness of less than 1 micrometer.

[0071] By using a silicon wafer as a temporary substrate and then setting a sacrificial layer on it, it is easier to fabricate a magnetic sensor layer on top.

[0072] Step 2: Fabrication of the magnetic sensor layer: On the sacrificial layer, without using any mask, several magnetic thin films with spin valve structures are grown by magnetron sputtering to obtain the magnetic sensor layer.

[0073] Step 3: Fabrication of the array of rigid islands: Photoresist is spin-coated onto the magnetic sensor layer, dried and cured, and then photolithography is performed using a photomask with a specific pattern to obtain the array of rigid islands. This is followed by development, fixing, and drying / curing to obtain several rigid islands 2. Specifically, the steps are as follows:

[0074] The prepared sample was placed on a spin coater and PI photoresist was spin-coated on the high elastic substrate thin film layer 1 at a speed of 1500 rpm. Then, it was rotated at 8000 rpm for 1 second to reduce edge effect and improve the flatness of the photoresist thickness after spin coating.

[0075] Place it on a 90℃ heating plate for 9 minutes to soften, then place it on a 50℃ heating plate for 30 seconds to bake.

[0076] After standing at room temperature for 5 minutes, use a photoresist plate with a circular or polygonal pattern.

[0077] The sample was immersed in NMD solution and shaken for about 90 seconds for development, then shaken in deionized water for about 5 seconds for fixing, and finally dried with nitrogen.

[0078] Place the sample into the etching machine and etch it with argon gas for about 30 minutes;

[0079] Place the sample in a 200℃ forced-air oven to cure for 90 minutes, away from light.

[0080] In this step, argon gas is introduced for etching, which can eliminate the influence of rigid mask on sputtered magnetic film deposition, improve the function of magnetic sensor, and improve the accuracy of pattern.

[0081] Step 4: Fabrication of high elastic substrate thin film layer 1: Mix the precursor of the high elastic substrate and the curing agent evenly according to the preset weight ratio and spin coat them onto the array of rigid islands 2. After drying and curing, the high elastic substrate thin film layer 1 is obtained.

[0082] Specifically, the process includes the following steps: the precursor of the high-elasticity substrate and the curing agent are mixed uniformly at a weight ratio of 10:1, spin-coated onto the sacrificial layer at a speed of 1200 rpm, and then cured in a 60°C forced-air oven for 12 hours to obtain the high-elasticity substrate layer. The precursor material for the high-elasticity substrate is polydimethylsiloxane (PDMS).

[0083] After this step, perform the stripping step 41: use deionized water to dissolve the sacrificial layer, remove the temporary substrate layer and dry it with nitrogen gas in time to obtain the magnetic sensor 3 with a modulus gradient structure.

[0084] Step 5: Each rigid island 2 in the array rigid island layer leads out several elastic electrodes 4 from the corresponding magnetic sensor 3, and attaches the led-out elastic electrodes 4 to the highly elastic substrate thin film layer 1.

[0085] Specifically, the steps include: using liquid metal or silver nanowires to lead out four elastic electrodes 4 from the magnetic sensor 3 on each rigid island 2, connecting them to platinum wires, encapsulating them with PDMS, and then detecting the device performance.

[0086] In this embodiment, the high-elasticity substrate thin film layer 1, the array rigid island layer, and the magnetic sensor layer present a modulus gradient structure, which can still have a strain isolation effect under deformations such as stretching, bending, and torsion in various directions. This allows the high-elasticity substrate thin film layer 1 to bear most of the strain, while the magnetic sensor 3 on the array rigid island layer maintains its original performance, greatly improving the application scenarios and service life of the magnetic sensor 3.

[0087] The flexible magnetic sensor that can be stretched in all directions prepared in this embodiment is fabricated in reverse. However, the sacrificial layer will cause wrinkles in the magnetic film, resulting in the GMR performance being only half that of the forward fabrication. However, the stretching performance is better, the process is more refined, the sample volume is relatively small, the stretching is good, the stability is high, and the sensitivity is high.

[0088] Example 3

[0089] This embodiment relates to a method for fabricating a flexible magnetic sensor array that can be stretched in all directions, including a reverse fabrication method, which includes the following steps:

[0090] Step 1: Provide a temporary substrate and clean it. The specific steps are as follows: Provide a mica sheet as a temporary substrate and clean the surface of the mica sheet using nitrogen plasma.

[0091] Using mica sheets as a temporary substrate eliminates the need for a sacrificial layer; the mica sheets can then be peeled off layer by layer, making the design convenient.

[0092] Step 2: Fabrication of the magnetic sensor layer: On a mica sheet, without using any mask, several magnetic thin films with spin valve structures are grown by magnetron sputtering to obtain the magnetic sensor layer.

[0093] Step 3: Fabrication of the array of rigid islands: Photoresist is spin-coated onto the magnetic sensor layer, dried and cured, and then photolithography is performed using a photomask with a specific pattern to obtain the array of rigid islands. This is followed by development, fixing, and drying / curing to obtain several rigid islands 2. Specifically, the steps are as follows:

[0094] The prepared sample was placed on a spin coater and PI photoresist was spin-coated on the high elastic substrate thin film layer 1 at a speed of 1500 rpm. Then, it was rotated at 8000 rpm for 1 second to reduce edge effect and improve the flatness of the photoresist thickness after spin coating.

[0095] Place it on a 90℃ heating plate for 9 minutes to soften, then place it on a 50℃ heating plate for 30 seconds to bake.

[0096] After standing at room temperature for 5 minutes, use a photoresist plate with a circular or polygonal pattern.

[0097] The sample was immersed in NMD solution and shaken for about 90 seconds for development, then shaken in deionized water for about 5 seconds for fixing, and finally dried with nitrogen.

[0098] Place the sample into the etching machine and etch it with argon gas for about 30 minutes;

[0099] Place the sample in a 200℃ forced-air oven to cure for 90 minutes, away from light.

[0100] In this step, argon gas is introduced for etching, which can eliminate the influence of rigid mask on sputtered magnetic film deposition, improve the function of magnetic sensor, and improve the accuracy of pattern.

[0101] Step 4: Fabrication of high elastic substrate thin film layer 1: Mix the precursor of the high elastic substrate and the curing agent evenly according to the preset weight ratio and spin-coat it onto the array of rigid islands. After drying and curing, the high elastic substrate thin film layer 1 is obtained.

[0102] Specifically, the process includes the following steps: the precursor of the high-elasticity substrate and the curing agent are mixed uniformly at a weight ratio of 10:1, spin-coated onto the sacrificial layer at a speed of 1200 rpm, and then cured in a 60°C forced-air oven for 12 hours to obtain the high-elasticity substrate layer. The precursor material for the high-elasticity substrate is polydimethylsiloxane (PDMS).

[0103] After this step, perform the peeling step 41: peel off the mica sheet layer by layer using adhesive tape to obtain the magnetic sensor 3 with a modulus gradient structure.

[0104] Step 5: Each rigid island 2 in the array rigid island layer leads out several elastic electrodes 4 from the corresponding magnetic sensor 3, and attaches the led-out elastic electrodes 4 to the highly elastic substrate thin film layer 1.

[0105] Specifically, the steps include: using liquid metal or silver nanowires to lead out four elastic electrodes 4 from the magnetic sensor 3 on each rigid island 2, connecting them to platinum wires, encapsulating them with PDMS, and then detecting the device performance.

[0106] In this embodiment, the high-elasticity substrate thin film layer 1, the array rigid island layer, and the magnetic sensor layer present a modulus gradient structure, which can still have a strain isolation effect under deformations such as stretching, bending, and torsion in various directions. This allows the high-elasticity substrate thin film layer 1 to bear most of the strain, while the magnetic sensor 3 on the array rigid island layer maintains its original performance, greatly improving the application scenarios and service life of the magnetic sensor 3.

[0107] The flexible magnetic sensor that can be stretched in all directions obtained in this embodiment is fabricated in reverse. The sacrificial layer causes wrinkles in the magnetic film, resulting in GMR performance that is only half that of the forward fabrication. At the same time, a mica sheet is used as a temporary substrate. When the mica is torn off, it will cause slight damage to the sample and leave mica residue. However, the stretching performance of the device is similar to that of the forward fabrication. The sample volume is relatively small, with good stretchability, high stability, and high sensitivity.

[0108] The beneficial effects of the present invention are as follows: the high elastic substrate thin film layer 1, the array rigid island layer and the magnetic sensor layer present a modulus gradient structure, which can still have a strain isolation effect under deformations such as stretching, bending and torsion in various directions. This allows the high elastic substrate thin film layer 1 to bear most of the strain, while the magnetic sensor 3 on the array rigid island layer maintains its original performance, greatly improving the application scenarios and service life of the magnetic sensor 3.

[0109] The foregoing description illustrates and describes several preferred embodiments of the present invention. However, as previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the inventive concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

[0110] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. A flexible magnetic sensor array that can be stretched in all directions, characterized in that: The system includes a high-elasticity substrate thin film layer (1), an array of rigid islands, and a magnetic sensor layer. The array of rigid islands includes a plurality of rigid islands (2) arranged in an array on the high-elasticity substrate thin film layer (1). The magnetic sensor layer includes a magnetic sensor (3) disposed on each rigid island (2). Each rigid island (2) leads out a plurality of elastic electrodes (4) from the magnetic sensor (3). All the elastic electrodes (4) are attached to the high-elasticity substrate thin film layer (1) and lead out to the edge of the high-elasticity substrate thin film layer (1). The Young's modulus of the magnetic sensor (3) is greater than that of the rigid island (2). The Young's modulus of the rigid island (2) is greater than that of the high-elasticity substrate thin film layer (1). The material of the high elastic substrate thin film layer (1) is PDMS, PU or Ecofelx, the material of the rigid island (2) is polyimide or photoresist, and the material of the elastic electrode (4) is liquid metal or silver nanowires. The surface roughness of both the highly elastic substrate thin film layer (1) and the rigid island (2) is less than 1 nanometer.

2. The flexible magnetic sensor array that can be stretched in all directions according to claim 1, characterized in that: Both the rigid island (2) and the magnetic sensor (3) are circular or polygonal.

3. A method for fabricating an anisotropic stretchable flexible magnetic sensor array according to any one of claims 1 to 2, characterized in that: The method includes a forward fabrication method and a reverse fabrication method. The forward fabrication method is performed sequentially according to steps S1, S2, S3, S4, and S5, and the reverse fabrication method is performed sequentially according to steps S1, S4, S3, S2, and S5. S1. Provide a temporary substrate and clean it; S2. Fabrication of a high-elasticity substrate thin film layer (1): The precursor of the high-elasticity substrate and the curing agent are mixed evenly according to a preset weight ratio and spin-coated onto the upper layer. After drying and curing, a high-elasticity substrate thin film layer (1) is obtained. S3. Fabrication of an array of rigid islands: spin-coating photoresist onto the upper layer, drying and curing, and then using a photolithography plate with a specific pattern to perform photolithography to obtain an array of rigid islands. Then, development, fixing, drying and curing are performed in sequence to obtain several rigid islands (2). S4. Fabrication of the magnetic sensor layer: Several magnetic thin films with spin valve structures are grown on the previous layer by magnetron sputtering to obtain the magnetic sensor layer. S5. Each rigid island (2) in the array rigid island layer has several elastic electrodes (4) drawn out from the corresponding magnetic sensor (3), and the drawn elastic electrodes (4) are attached to the high elastic substrate thin film layer (1).

4. The method for fabricating an isotropic stretchable flexible magnetic sensor array according to claim 3, characterized in that: In both the forward and reverse manufacturing methods, step S1 includes the following steps: S11. Provide a silicon wafer as a temporary substrate and clean the surface of the silicon wafer using plasma. S12. Spin-coat a dextran solution of a specific concentration onto the cleaned silicon wafer surface and bake to obtain a sacrificial layer.

5. A method for fabricating an anisotropic stretchable flexible magnetic sensor array according to claim 3 or 4, characterized in that: In the forward fabrication method, a cleaning step is provided after step S2 and before step S3: the surface of the high elastic substrate thin film layer (1) is cleaned using plasma.

6. The method for fabricating an isotropically stretchable flexible magnetic sensor array according to claim 4, characterized in that: In both the forward and reverse fabrication methods, in step S3, after spin-coating the photoresist, the image is then idled at a specific speed for a period of time.

7. The method for fabricating an isotropic stretchable flexible magnetic sensor array according to claim 4, characterized in that: In the forward fabrication method, step S4 includes the following steps: dissolving the sacrificial layer with deionized water, removing the temporary substrate layer and drying it, fixing it on the array rigid island layer with a mask of the corresponding pattern, and growing a magnetic thin film of a spin valve structure on each rigid island (2) by magnetron sputtering to obtain a magnetic sensor layer. In the reverse fabrication method, step S4 includes the following steps: a magnetic thin film with a spin valve structure is grown on the sacrificial layer by magnetron sputtering to obtain a magnetic sensor layer; and a stripping step is provided after step S2 and before step S5: the sacrificial layer is dissolved with deionized water, the temporary substrate layer is removed and dried.

8. The method for fabricating an isotropic stretchable flexible magnetic sensor array according to claim 3, characterized in that: In the reverse fabrication method, step S1 includes the following steps: providing a mica sheet as a temporary substrate layer, cleaning the mica sheet using plasma; and peeling off the mica sheet layer by layer using adhesive tape after step S2 and before step S5.

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