A biosensor based on magnetic field regulation and a preparation method thereof

Abstract

The application discloses a biosensor based on magnetic field regulation and a preparation method thereof, and belongs to the field of biosensors. The application solves the problem of insufficient sensitivity of the existing biosensor. The technical scheme adopted to solve the technical problem is as follows: a conductive part and a flexible substrate with elasticity are included; a magnetoelastic layer, a GMR sensing layer and a biological recognition layer are sequentially deposited on the flexible substrate; the conductive part is in contact with the GMR sensing layer; the magnetoelastic layer comprises a closed magnetic loop with a serpentine structure; an insulating layer is arranged between the magnetoelastic layer and the GMR sensing layer; a passivation layer is deposited between the GMR sensing layer and the biological recognition layer; the surface of the biological recognition layer is modified with RGD peptide; and the conductive part comprises a top electrode and a bottom electrode, and the top electrode and the bottom electrode both adopt a interdigitated electrode pattern. The application is applied to the biosensor.

Description

Technical Field

[0001] This invention provides a biosensor based on magnetic field modulation and its preparation method, belonging to the field of biosensor technology. Background Technology

[0002] With the increasing demand for high-precision and high-sensitivity sensors in fields such as biomedicine, environmental monitoring, and food safety, the bottlenecks of traditional biosensors in terms of performance, sensitivity, and specificity are gradually becoming apparent, necessitating breakthroughs in new sensing technologies. In recent years, biosensors based on multi-physics coupling effects have gradually become a research hotspot. Among them, sensors with magnetic, mechanical, and electrical coupling have attracted widespread attention due to their high sensitivity, real-time performance, and ease of miniaturization.

[0003] In recent years, researchers have developed GMR-based biosensors using the giant magnetoresistance (GMR) effect. These biosensors utilize the influence of magnetic fields on biomolecules to detect their presence even under weak magnetic field changes, achieving high sensitivity and specificity. However, they still face some challenges in practical applications, such as sensor stability, repeatability, and cost.

[0004] Therefore, developing a novel magnetic field-controlled biosensor to solve the above-mentioned technical problems has significant academic value and application prospects. Summary of the Invention

[0005] To address the technical problem of insufficient sensitivity in existing biosensors, this invention proposes a biosensor based on magnetic field modulation and its fabrication method. The aim is to combine the giant magnetoresistance (GMR) effect with the magnetoelastic effect. This invention can achieve high-sensitivity detection of weak biological signals, and is particularly suitable for high-precision biological detection fields such as single-cell and molecular recognition.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: it includes a conductive part and an elastic flexible substrate, wherein a magnetoelastic layer, a GMR sensing layer and a biometric layer are sequentially deposited on the flexible substrate, and the conductive part is in contact with the GMR sensing layer.

[0007] The magnetoelastic layer includes a closed magnetic circuit with a serpentine structure;

[0008] An insulating layer is provided between the magnetoelastic layer and the GMR sensing layer;

[0009] A passivation layer is deposited between the GMR sensing layer and the biometric layer;

[0010] The surface of the biometric layer is modified with RGD peptide;

[0011] The conductive part includes a top electrode and a bottom electrode, both of which adopt an interdigitated electrode pattern.

[0012] Furthermore, the flexible substrate includes a glass substrate, on which tin foil is wrapped, and on which a PDMS film is coated.

[0013] Furthermore, the GMR sensing layer is a multilayer film structure composed of alternating ferromagnetic and nonmagnetic metal layers.

[0014] Furthermore, the biometric layer is made of gold nanomaterials.

[0015] Furthermore, the magnetostriction coefficient λ of the magnetoelastic layer s ≥60 ppm.

[0016] Furthermore, the passivation layer is made of Al2O3 material; the insulating layer is made of SiO2 material.

[0017] Furthermore, the magnetoelastic layer is made of a magnetoelastic material.

[0018] Furthermore, the GMR sensing layer is made of alternating deposited CoFe and Cu materials.

[0019] A method for fabricating the above-described magnetic field-controlled biosensor includes the following steps:

[0020] Step 1: Prepare a flexible substrate;

[0021] Step 2: Deposit magnetoelastic material on a flexible substrate and use a mask to form a serpentine structure to form a magnetoelastic layer;

[0022] Step 3: Alternately deposit several layers of ferromagnetic and non-magnetic metallic materials on the magnetoelastic layer to form the GMR sensing layer;

[0023] Step 4: In an ultra-high vacuum (UHV) environment, gold nanomaterials are deposited on the GMR sensing layer to obtain a gold nanolayer, and RGD peptides are modified on the gold nanolayer to obtain a bio-recognition layer.

[0024] Step 5: Install the electrodes and electrically connect them to the GMR sensing layer;

[0025] Step 6: Package and test;

[0026] Furthermore, an insulating layer is deposited on the surface of the magnetoelastic layer obtained in step two; and a passivation layer is deposited on the GMR sensing layer obtained in step three.

[0027] The advantages of this invention over the prior art are as follows:

[0028] 1. The GMR sensing layer and magnetoelastic layer of this invention effectively enhance the modulation effect of the magnetic field on the sensor's detection performance, thereby significantly improving the sensitivity and detection accuracy of the biosensor. By introducing the stress response of the magnetoelastic material and the resistance change of the GMR material, the sensor can efficiently convert minute mechanical signals into electrical signals, thus achieving highly sensitive detection of weak biological signals (such as proteins, cells, DNA, etc.). Furthermore, the biomolecule recognition layer is modified with RGD peptides, enabling the sensor to detect highly selective biomolecules, making it suitable for various biomedical, environmental monitoring, and food safety fields.

[0029] 2. By combining the GMR effect and the magnetoelastic effect, this invention can make full use of the advantages of both and solve the shortcomings of traditional biosensors in terms of sensitivity, response speed and stability. It has important application value and broad market prospects. Attached Figure Description

[0030] The present invention will be further described below with reference to the accompanying drawings:

[0031] Figure 1 This is a schematic diagram of the structure of the present invention;

[0032] Figure 2 This is a schematic diagram of the structure of the magnetoelastic layer of the present invention;

[0033] Figure 3 This is a schematic diagram of the composition of the biosensor film based on magnetic field modulation of the present invention;

[0034] In the figure: 1 is the flexible substrate, 2 is the magnetoelastic layer, 3 is the insulating layer, 4 is the bottom electrode, 5 is the GMR sensing layer, 6 is the top electrode, 7 is the passivation layer, 8 is the biometric layer, and 9 is the conductive part. Detailed Implementation

[0035] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate relative orientations or positional relationships and are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0036] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0037] like Figures 1 to 3 As shown, the present invention provides a biosensor based on magnetic field modulation, including a conductive part 9 and a flexible substrate 1 with elasticity. The conductive part 9 includes a top electrode 6 and a bottom electrode 4. Both the top electrode 6 and the bottom electrode are made of Cu material. Both the top electrode 6 and the bottom electrode 4 adopt interdigitated electrode patterns with a width of 50 μm-80 μm.

[0038] The flexible substrate 1 includes a glass substrate, a tin foil covering the glass substrate, and a polydimethylsiloxane (hereinafter referred to as "PDMS") film covering the tin foil, the thickness of the PDMS film being 8μm-10μm.

[0039] A magnetoelastic layer 2, a GMR sensing layer 5, and a biometric layer 8 are sequentially deposited on a flexible substrate 1. A conductive part 9 is electrically connected to the giant magnetoresistive sensing layer (hereinafter referred to as the "GMR sensing layer"), and the signal is read through an external circuit, which facilitates the signal reading and data processing of the sensor. Specifically, the top electrode 6 and the bottom electrode 4 are located on the upper and lower surfaces of the GMR sensing layer 5, respectively.

[0040] A magnetoelastic layer 2 is formed by depositing a magnetoelastic material, such as an iron-based alloy or a nickel-iron alloy, on a flexible substrate 1 using methods such as sputtering or laser pulse deposition to provide strong magnetoelastic response. The magnetoelastic layer 2 can respond to small changes in external force and convert them into changes in surface stress, and also exhibits an electrical response to weak mechanical changes. In this embodiment, FeGa material is used, specifically Fe... 0.8 Ga 0.2 Alloy. The thickness of magnetoelastic layer 2 is 200nm-300nm. Magnetoelastic layer 2 is a closed magnetic circuit structure with a serpentine structure. The magnetostriction coefficient λs≥60 ppm. The linewidth of its serpentine structure is 3μm and the spacing is 5μm. The magnetoelastic layer 2 is made into a serpentine structure using a mask.

[0041] GMR material is deposited on the magnetoelastic layer 2 using techniques such as sputtering, chemical vapor deposition (CVD), and plasma-enhanced chemical vapor deposition (PECVD) to uniformly cover the surface of the magnetoelastic layer 2, forming the GMR sensing layer 5. The GMR sensing layer 5 is a uniform multilayer film structure composed of alternating ferromagnetic and non-magnetic metal layers, achieving a highly sensitive response to changes in the applied magnetic field. Specifically, it utilizes the GMR effect, causing a change in resistance in the GMR sensing layer 5 due to variations in the external magnetic field. The GMR sensing layer 5 is fully coupled to the magnetoelastic layer 2 to improve the sensor's sensitivity and response speed. In this embodiment, a 0.6-2 nm CoFe layer and a 2.2-5 nm Cu layer are alternately deposited on the magnetoelastic layer, with an alternation period of 10.

[0042] The biometric layer 8 is composed of a 50nm thick gold nanolayer. This gold nanolayer is modified with selenoglycinin (hereinafter referred to as "RGD peptide"), giving the sensor specific biometric functions. Modifying the gold nanolayer with RGD peptide enhances biocompatibility, enabling specific recognition of target biomolecules (such as proteins, DNA, and single cells), and facilitating the detection of specific biomarkers. The biometric layer 8 uses self-assembly technology or chemical modification methods to immobilize target biomolecules on the surface of the GMR sensing layer 5 in a high-density and highly stable manner, thereby improving the sensor's specificity and stability.

[0043] An insulating layer 3 is also deposited between the GMR sensing layer 5 and the magnetoelastic layer 2. The thickness of the insulating layer 3 is 20nm-50nm. The insulating layer 3 is made of SiO2 material and is used to prevent interference from the conductivity of the magnetoelastic layer 2 itself.

[0044] A passivation layer 7 is deposited between the GMR sensing layer 5 and the biometric layer 8. The passivation layer 7 is an Al2O3 thin film with a thickness of 20nm-50nm, which can block the penetration of Cl⁻, Na⁺ and other ions, and prevent electrochemical corrosion of the multilayer film of the GMR sensing layer 5; as an elastic medium, it can withstand applied forces (local stress gradients can reach 10). 4 The Pa / μm is uniformly transferred to the GMR sensing layer 5 to avoid film rupture caused by stress concentration.

[0045] The deposition thickness and structure of the GMR sensing layer 5 and the magnetoelastic layer 2 can be adjusted by optimizing process parameters, thereby improving the multi-physics coupling effect and enhancing the sensor's response to weak mechanical changes.

[0046] The present invention also provides a method for fabricating the above-mentioned magnetic field-controlled biosensor, comprising the following steps:

[0047] Step 1: Preparation of flexible substrate 1: Use a spin coater to cover the degassed PDMS liquid onto the tin foil covering the glass substrate. After curing, a PDMS film is formed on the tin foil covering the glass substrate.

[0048] Specifically, a flexible substrate 1 is prepared by sputtering, coating, and other methods. Using Sylgard 184 and Dow Corning as raw materials, the prepolymer and curing agent are mixed at a weight ratio of 10:1, then stirred until homogeneous. Next, a degassing machine is used to remove air bubbles from the mixture. After standing for 10-15 minutes, a spin coater is used to coat the PDMS solution onto a glass substrate wrapped with tin foil to form a PDMS film. The PDMS film is then cured on a drying table at 110-130℃ for 10-15 minutes. In this embodiment, the spin coater is set to single-step operation mode, with a rotation speed of 2000 rpm, a time of 60 seconds, and an acceleration of 500 m / s². After successful setup, the degassed PDMS is spin-coated onto the tin foil covering the glass substrate using the spin coater, and then cured on a heating table at 120℃ for 10 minutes to form a PDMS film.

[0049] Step 2: Deposit magnetoelastic material on flexible substrate 1 and use a mask to make a serpentine structure to form magnetoelastic layer 2, thus obtaining the second substrate.

[0050] Specifically, a 200 nm thick FeGa thin film was deposited by magnetron sputtering. The magnetron sputtering parameters were: target material: Fe... 0.8 Ga 0.2 Alloy target (99.99% purity); sputtering gas: Ar (99.999% purity); gas pressure: 3 mTorr; power: DC 200W; first substrate temperature ≤100℃, preferably 50℃; sputtering rate: 0.5 nm / s; FeGa thin film properties: magnetostriction coefficient λ s =70 ppm, surface roughness Ra<2 nm. The first substrate specifically refers to flexible substrate 1.

[0051] When depositing magnetoelastic material on flexible substrate 1 using PECVD process, the parameters are: gas: SiH4 (30 sccm) + N2O (100 sccm); RF power: 40 W, deposition rate: 20 nm / min; thickness: 50 nm, dielectric strength > 20 MV / cm.

[0052] Step 3: Alternately deposit multiple layers of ferromagnetic and nonmagnetic metallic materials on the magnetoelastic layer 2 to form the GMR sensing layer 5.

[0053] Specifically, a layer of CoFe with a thickness of 0.6 nm-5 nm and a layer of Cu with a thickness of 2.2-5 nm are alternately deposited on the magnetoelastic layer 2 by magnetron sputtering, with an alternation period of 10. The magnetron sputtering parameters are: second substrate temperature: 80℃, vacuum degree <5×10⁻ 8 Torr; CoFe target power: RF 150 W, Cu target power: DC 100 W.

[0054] Step 4: Sputter 50nm gold nanomaterials onto the GMR sensing layer 5 using magnetron sputtering to obtain a gold nanolayer. Clean the gold surface to remove organic contaminants and oxide layers, and modify the gold nanolayer with RGD peptides to obtain the biometric layer 8.

[0055] Specifically, the magnetron sputtering parameters are as follows: target material: Au metal target (purity 99.99%); sputtering gas: Ar (purity 99.999%), gas pressure 3 mTorr; power: DC 50 W, substrate temperature 200℃; thin film characteristics: deposition thickness 50 nm, surface roughness Ra < 1 nm.

[0056] The modification of RGD peptides onto gold nanolayers involves first coupling amino-containing molecules (such as glycine) to the surface of the gold nanolayer using chemical reagents (such as EDC / NHS), and then coupling the amino groups of the RGD peptides to functionalized groups on the surface of the gold nanolayer using chemical reagents containing active groups (such as EDC / NHS). More specifically, high-purity RGD peptide powder is dissolved in dimethyl sulfoxide (DMSO) solution to prepare a 5 μM RGD peptide solution. Equal volumes of 50-100 mol / L EDC and NHS solutions are mixed with the RGD peptide solution, and then the mixture is added dropwise to the sensor and reacted at 37 °C for 2 hours. After modification, the surface of the gold nanolayer needs to be post-treated to remove unreacted reagents and unbound RGD peptides. The surface of the gold nanolayer is washed with phosphate-buffered saline (PBS) buffer to remove unbound molecules.

[0057] Step 5: Install the electrodes and electrically connect them to the GMR sensing layer 5.

[0058] Step 6: Package and test.

[0059] Furthermore, an insulating layer 3 is deposited on the surface of the magnetoelastic layer 2 obtained in step two. Copper is then sputtered onto the insulating layer 3 to form the bottom electrode 4. The pattern of the bottom electrode 4 is set as an intercalation electrode using a photolithography mask. The photolithography mask parameters are: AZ5214 photoresist (1.5 μm thickness), exposure dose 120 mJ / cm². The sputtering copper plating process parameters are: sputtering power 150 W (DC), Ar gas pressure 5 mTorr; thickness: 5 μm-10 μm.

[0060] Furthermore, a 20 nm passivation layer 7 is deposited on the GMR sensing layer 5 obtained in step three. The passivation layer 7 is made of Al2O3 material. A 50 nm thick copper layer is sputtered and deposited on the passivation layer 7 to form the top electrode 6. The fabrication process of the top electrode 6 is the same as that of the bottom electrode 4.

[0061] Working principle of the invention:

[0062] When the analyte is modified onto the biometric layer 8, it causes the magnetoelastic layer 2 to deform, thereby changing its magnetic permeability and altering the local magnetic field. This, in turn, causes a change in the resistance of the GMR sensing layer 5, which outputs an electrical signal through the top electrode 6 and the bottom electrode 4, thus enabling highly sensitive detection of weak biological signals (such as proteins, cells, DNA, etc.).

[0063] Regarding the specific structure of this invention, it should be noted that the connection relationships between the various component modules used in this invention are definite and achievable. Except as specifically described in the embodiments, their specific connection relationships can bring about corresponding technical effects and solve the technical problems proposed by this invention without relying on the execution of corresponding software programs. The models of the components, modules, and specific components appearing in this invention, the connection methods between them, and the conventional usage methods and expected technical effects brought about by the above technical features, unless specifically described, are all publicly disclosed content in patents, journal articles, technical manuals, technical dictionaries, and textbooks that can be obtained by those skilled in the art before the application date, or belong to conventional technology, common knowledge, and other existing technologies in this field. There is no need to elaborate, which makes the technical solution provided in this case clear, complete, and achievable, and can reproduce or obtain corresponding physical products based on this technical means.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a magnetic field-based biosensor, characterized by: The biosensor based on magnetic field regulation comprises a conductive part (9) and a flexible substrate (1) with elasticity, and the flexible substrate (1) is sequentially deposited with a magnetoelastic layer (2), a GMR sensing layer (5) and a biological recognition layer (8); the conductive part (9) is in contact with the GMR sensing layer (5). The magnetoelastic layer (2) comprises a closed magnetic loop with a serpentine structure. An insulating layer (3) is arranged between the magnetoelastic layer (2) and the GMR sensing layer (5). A passivation layer (7) is deposited between the GMR sensing layer (5) and the biological recognition layer (8). The surface of the biological recognition layer (8) is modified with RGD peptide. The conductive part (9) comprises a top electrode (6) and a bottom electrode (4), and both the top electrode (6) and the bottom electrode (4) adopt a finger electrode pattern. The preparation method of the biosensor based on magnetic field regulation comprises the following steps: Step one, preparing a flexible substrate (1); Step two, depositing a magnetoelastic material on the flexible substrate (1), forming a serpentine structure by using a mask plate to form a magnetoelastic layer (2); Step three, alternately depositing several layers of ferromagnetic material and non-magnetic metal material on the magnetoelastic layer (2) to form a GMR sensing layer (5); Step four, depositing a nano-gold material on the GMR sensing layer (5) in an ultrahigh vacuum environment to obtain a nano-gold layer, and modifying the nano-gold layer with RGD peptide to obtain a biological recognition layer (8); Step five, installing an electrode, and the electrode is electrically connected with the GMR sensing layer (5); Step six, packaging and testing.

2. The method for preparing a magnetic field regulated biosensor according to claim 1, wherein: The flexible substrate (1) comprises a glass substrate, the glass substrate is coated with a tin paper, and the tin paper is covered with a PDMS film.

3. The method of claim 1, wherein the method further comprises: The GMR sensing layer (5) is a multilayer film structure composed of alternating ferromagnetic and non-magnetic metal layers.

4. The method for preparing a magnetic field regulated biosensor according to claim 1, wherein: The biological recognition layer (8) is made of nano-gold material.

5. The method of claim 1, wherein the method further comprises: The magnetostriction coefficient λs of the magnetoelastic layer (2) is greater than or equal to 60 ppm.

6. The method of claim 1, wherein the method further comprises: The passivation layer (7) is made of Al2O3 material, and the insulating layer (3) is made of SiO2 material.

7. The method of claim 1, wherein the method further comprises: The magnetoelastic layer (2) is made of magnetoelastic material.

8. The method of claim 1, wherein the method further comprises: The GMR sensing layer (5) is made of alternately deposited CoFe material and Cu material.

9. The method of claim 1, wherein: The surface of the magnetoelastic layer (2) obtained in the step two is deposited with an insulating layer (3); and the GMR sensing layer (5) obtained in the step three is deposited with a passivation layer (7).

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