Biosensor based on magnetic field regulation and control and preparation method thereof

Abstract

The invention discloses a biosensor based on magnetic field regulation and control and a preparation method thereof, and belongs to the field of biosensors. The problem that an existing biosensor is insufficient in sensitivity is solved. In order to solve the technical problem, the technical scheme adopted by the invention is as follows: the sensor comprises a conductive part and an elastic flexible substrate, 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 snakelike structure, an insulating layer is arranged between the magnetoelastic layer and the GMR sensing layer, and the magnetic conductive part is in contact with 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, the conductive part comprises a top electrode and a bottom electrode, and the top electrode and the bottom electrode both adopt interdigitated electrode patterns; the invention is applied to the biosensor.

Description

Technical Field

[0001] The present invention provides a magnetic-field-regulated biosensor and a preparation method thereof, belonging to the technical field of biosensors. Background Art

[0002] With the increasing demand for high-precision and high-sensitivity sensors in the fields of biomedicine, environmental monitoring, and food safety, the bottlenecks of traditional biosensors in terms of performance, sensitivity, specificity, etc. have gradually emerged, and a breakthrough in new sensing technologies is urgently needed. In recent years, biosensors based on the coupling effect of multiple physical fields have gradually become a research hotspot. Among them, sensors coupling magnetics, mechanics, and electricity have received extensive 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 principle. By utilizing the influence of magnetic fields on biomolecules, they can detect the presence of biomolecules under weak magnetic field changes, achieving high-sensitivity and high-specificity detection. However, in practical applications, they still face some challenges, such as issues related to the stability, repeatability, and cost of the sensors.

[0004] Therefore, developing a new type of magnetic-field-regulated biosensor to solve the above technical problems has important academic value and application prospects. Summary of the Invention

[0005] In order to solve the technical problem of insufficient sensitivity of existing biosensors, the present invention proposes a magnetic-field-regulated biosensor and a preparation method thereof. The aim is to combine the giant magnetoresistance (GMR) effect and the magnetoelastic effect. The present invention can achieve high-sensitivity detection of weak biological signals, and is particularly suitable for high-precision biological detection fields such as single cells and molecular recognition.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows: It includes a conductive part and a flexible substrate with elasticity. A magnetoelastic layer, a GMR sensing layer, and a biorecognition layer are sequentially deposited on the flexible substrate, and the conductive part is in contact with the GMR sensing layer; The magnetoelastic layer includes a closed magnetic circuit with a serpentine structure; An insulating layer is provided between the magnetoelastic layer and the GMR sensing layer; A passivation layer is deposited between the GMR sensing layer and the biorecognition layer; The surface of the biorecognition layer is modified with RGD peptides; The conductive part includes a top electrode and a bottom electrode, and both the top electrode and the bottom electrode adopt an interdigitated electrode pattern.

[0007] Further, the flexible substrate includes a glass substrate, on which tinfoil is coated, and a PDMS film is covered on the tinfoil.

[0008] Further, the GMR sensing layer is a multi-layer film structure composed of alternating ferromagnetic and non-magnetic metal layers.

[0009] Further, the biometric recognition layer is made of nano-gold material.

[0010] Further, the magnetostrictive coefficient λ of the magnetoelastic layer s ≥60 ppm.

[0011] Further, the passivation layer is made of Al 2 O 3 material; the insulating layer is made of SiO 2 material.

[0012] Further, the magnetoelastic layer is made of magnetoelastic material.

[0013] Further, the GMR sensing layer is made of alternately deposited CoFe material and Cu material.

[0014] A preparation method for manufacturing the above-mentioned magnetic field-regulated biosensor includes the following steps: Step 1, prepare a flexible substrate; Step 2, deposit a magnetoelastic material on the flexible substrate, and use a mask to form a serpentine structure to form a magnetoelastic layer; Step 3, alternately deposit several layers of ferromagnetic material and non-magnetic metal material on the magnetoelastic layer to form a GMR sensing layer; Step 4, in an ultra-high vacuum (UHV) environment, deposit nano-gold material on the GMR sensing layer to obtain a nano-gold layer, and modify the RGD peptide on the nano-gold layer to obtain a biometric recognition layer; Step 5, install electrodes, and the electrodes are electrically connected to the GMR sensing layer; Step 6, package and test; Further, deposit an insulating layer on the surface of the magnetoelastic layer obtained in Step 2; deposit a passivation layer on the GMR sensing layer obtained in Step 3.

[0015] The beneficial effects of the present invention compared with the prior art are: 1. The setting of the GMR sensing layer and the magnetoelastic layer in the present invention can effectively enhance the regulation effect of the magnetic field on the detection performance of the sensor, 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 tiny mechanical signals into electrical signals, thus achieving high-sensitivity detection of weak biological signals (such as proteins, cells, DNA, etc.). In addition, the biomolecular recognition layer is modified with RGD peptides, enabling the sensor to detect highly selective biomolecules and be applicable to various fields such as biomedicine, environmental monitoring, and food safety; 2. By combining the GMR effect and the magnetoelastic effect, the present invention can make full use of the advantages of both, solve the deficiencies of traditional biosensors in terms of sensitivity, response speed, and stability, and has important application value and broad market prospects. Brief Description of the Drawings

[0016] The present invention will be further described below with reference to the drawings: Figure 1 is a schematic structural diagram of the present invention; Figure 2 is a schematic structural diagram of the magnetoelastic layer of the present invention; Figure 3 is a schematic diagram of the composition of the thin film of the magnetic field-regulated biosensor of the present invention; In the figure: 1 is a flexible substrate, 2 is a magnetoelastic layer, 3 is an insulating layer, 4 is a bottom electrode, 5 is a GMR sensing layer, 6 is a top electrode, 7 is a passivation layer, 8 is a biomolecular recognition layer, and 9 is a conductive part. Detailed Embodiments

[0017] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate relative orientation or position relationships, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation of the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0018] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0019] like Figures 1 to 3 As shown, the present invention provides a biosensor based on magnetic field regulation, including a conductive part 9 and an elastic flexible substrate 1, the conductive part 9 includes a top electrode 6 and a bottom electrode 4, the top electrode 6 and the bottom electrode are both made of Cu material, and the top electrode 6 and the bottom electrode 4 both adopt an interdigitated electrode pattern with a width of 50 μm-80 μm.

[0020] The flexible substrate 1 includes a glass substrate, the glass substrate is coated with tin foil, the tin foil is covered with a polydimethylsiloxane (hereinafter referred to as "PDMS") film, and the thickness of the PDMS film is 8 μm-10 μm.

[0021] A magnetoelastic layer 2, a GMR sensing layer 5 and a biometric recognition layer 8 are sequentially deposited on a flexible substrate 1, and a conductive portion 9 is electrically connected to a giant magnetoresistance sensing layer (hereinafter referred to as a "GMR sensing layer"), and signals are read through an external circuit, which facilitates signal reading and data processing of the sensor. Specifically, a top electrode 6 and a bottom electrode 4 are located on the upper surface and the lower surface of the GMR sensing layer 5, respectively.

[0022] The magnetoelastic material is deposited on the flexible substrate 1 by sputtering, laser pulse deposition, etc. to form a magnetoelastic layer 2 to provide a strong magnetoelastic response capability, such as an iron-based alloy or a nickel-iron alloy. The magnetoelastic layer 2 can respond to small external force changes and convert them into surface stress changes, and generate electrical responses to weak mechanical changes. In this embodiment, FeGa material is used, specifically Fe 0.8 Ga 0.2 Alloy. The magnetoelastic layer 2 has a thickness of 200nm-300nm, is a closed magnetic loop structure of a serpentine structure, has a magnetostriction coefficient λs≥60 ppm, has a line width of 3μm, and a spacing of 5μm, and is made into a serpentine structure by using a mask plate.

[0023] Techniques such as sputtering, chemical vapor deposition (CVD), and plasma-enhanced chemical vapor deposition (PECVD) are used to deposit GMR materials on the magnetoelastic layer 2, so that the GMR materials uniformly cover the surface of the magnetoelastic layer 2 to form 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, which realizes a highly sensitive response to changes in the external magnetic field. That is, using the GMR effect, the GMR sensing layer 5 generates a resistance change due to changes in the external magnetic field. The GMR sensing layer 5 is fully coupled with the magnetoelastic layer 2 to improve the sensitivity and response speed of the sensor. In this embodiment, a layer of 0.6 - 2 nm CoFe and a layer of 2.2 - 5 nm Cu are alternately deposited on the magnetoelastic layer, and the alternating period is 10.

[0024] The biorecognition layer 8 is composed of a nano-gold layer with a thickness of 50 nm. The nano-gold layer is made of nano-gold material, and the nano-gold layer is modified with cilengitide (hereinafter referred to as "RGD peptide"), enabling the sensor to have specific biorecognition functions. Modifying RGD peptide on the nano-gold layer can enhance biocompatibility, realize specific recognition of target biomolecules (such as proteins, DNA, single cells, etc.), and achieve the detection of specific biomarkers. The biorecognition layer 8 fixes the target biomolecules on the surface of the GMR sensing layer 5 in a high-density and high-stability manner through self-assembly technology or chemical modification methods to improve the specificity and stability of the sensor.

[0025] 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 20 nm - 50 nm, and the insulating layer 3 is made of SiO 2 material to prevent the conductivity interference of the magnetoelastic layer 2 itself.

[0026] A passivation layer 7 is deposited between the GMR sensing layer 5 and the biorecognition layer 8. The passivation layer 7 is an Al 2 O 3 thin film with a thickness of 20 nm - 50 nm, which can block the penetration of Cl⁻, Na⁺ and other ions, avoiding electrochemical corrosion of the multilayer film of the GMR sensing layer 5; as an elastic medium, it can uniformly transfer the acting force (the local stress gradient can reach 10 4 Pa / μm) to the GMR sensing layer 5 to avoid film rupture caused by stress concentration.

[0027] 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-physical field coupling effect and enhancing the response ability of the sensor to weak mechanical changes.

[0028] The present invention also provides a preparation method for manufacturing the above-mentioned magnetic field-regulated biosensor, including the following steps: Step 1. Prepare the flexible substrate 1: Use a spin coater to cover the tin foil coated with a glass substrate with the degassed PDMS liquid. After curing, a PDMS film is formed on the tin foil coated with the glass substrate.

[0029] Specifically, the flexible substrate 1 is prepared by methods such as sputtering and coating. Using Sylgard 184, Dow Corning as raw materials, the prepolymer and the curing agent are mixed according to a weight ratio of 10:1, then stirred evenly. Next, use a degassing machine to remove the bubbles in the mixture. After standing for 10 - 15 minutes, use a spin coater to make the PDMS solution cover the glass substrate wrapped with tin foil to form a PDMS film. Cure the PDMS film on a drying table at 110 - 130 °C for 10 - 15 min. In this embodiment, the spin coater is set to the single-step operation mode, the rotation speed is set to 2000 revolutions per second, the time is set to 60 seconds, and the acceleration is set to 500 m / s². After successful setting, spin coat the degassed PDMS on the tin foil coated with the glass substrate through the spin coater, and cure it on a heating table at 120 °C for 10 minutes to form a PDMS film.

[0030] Step 2. Deposit a magnetoelastic material on the flexible substrate 1 and use a mask to make a serpentine structure to form a magnetoelastic layer 2, obtaining a second substrate.

[0031] Specifically, deposit an FeGa film with a thickness of 200 nm by magnetron sputtering. The magnetron sputtering parameters are: target: Fe 0.8 Ga 0.2 alloy target (purity 99.99%); sputtering gas: Ar (purity 99.999%); gas pressure 3 mTorr; power: DC 200W; the temperature of the first substrate ≤ 100 °C, and the temperature of the first substrate is preferably 50 °C; sputtering rate: 0.5 nm / s; the characteristics of the FeGa film are: magnetostrictive coefficient λ s = 70 ppm, surface roughness Ra < 2 nm. The first substrate specifically refers to the flexible substrate 1.

[0032] When depositing the magnetoelastic material on the flexible substrate 1 by the PECVD process, the parameters are: gas: SiH 4 (30 sccm) + N 2 O (100 sccm); RF power: 40 W, deposition rate 20 nm / min; thickness: 50 nm, dielectric strength > 20 MV / cm.

[0033] Step 3. Alternately deposit multiple layers of ferromagnetic materials and non-magnetic metal materials on the magnetoelastic layer 2 to form a GMR sensing layer 5.

[0034] Specifically, on the magnetoelastic layer 2, a 0.6 nm - 5 nm thick CoFe layer and a 2.2 - 5 nm thick Cu layer are alternately deposited by magnetron sputtering, with an alternating period of 10. The magnetron sputtering parameters are: the temperature of the second substrate: 80 °C, the vacuum degree < 5×10⁻ 8 Torr; the power of the CoFe target: RF 150 W, the power of the Cu target: DC 100 W.

[0035] Step 4: Sputter a 50 nm nano - gold material on the GMR sensing layer 5 by magnetron sputtering to obtain a nano - gold layer, clean the gold surface to remove organic pollutants and oxide layers, and modify the RGD peptide on the nano - gold layer to obtain a biorecognition layer 8; Specifically, the magnetron sputtering parameters are: 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 °C; film characteristics: deposition thickness 50 nm, surface roughness Ra < 1 nm.

[0036] Modifying the RGD peptide on the nano - gold layer specifically means that after coupling a molecule containing an amino group (such as glycine) to the surface of the nano - gold layer using chemical reagents (such as EDC / NHS), the amino group of the RGD peptide is coupled to the functional group on the surface of the nano - gold layer using a chemical reagent containing a reactive group (such as EDC / NHS). More specifically, dissolve the RGD peptide powder with a relatively high purity in dimethyl sulfoxide (DMSO) solution to prepare an RGD peptide solution with a concentration of 5 μM. Take equal volumes of 50 - 100 mol / L EDC and NHS solutions and mix them with the RGD peptide solution, then drop the mixed solution into the sensor and react at 37 °C for 2 hours. After the modification, post - treatment of the surface of the nano - gold layer is required to remove unreacted reagents and unbound RGD peptides. Wash the surface of the nano - gold layer with phosphate - buffered saline (PBS buffer) to remove unbound molecules.

[0037] Step 5: Install electrodes to electrically connect the electrodes to the GMR sensing layer 5.

[0038] Step 6: Package and test.

[0039] Furthermore, an insulating layer 3 is also deposited on the surface of the magnetoelastic layer 2 obtained in Step 2, and copper is sputtered and plated on the insulating layer 3 to form a bottom electrode 4. The pattern of the bottom electrode 4 is set as an interdigitated electrode through a photolithography mask. The photolithography mask parameters are: using AZ5214 photoresist (thickness 1.5 μm), exposure dose 120 mJ / cm². The sputtering and plating copper process parameters are: sputtering power 150 W (DC), Ar gas pressure 5 mTorr; thickness: 5 μm - 10 μm.

[0040] Further, a 20-nm passivation layer 7 is also deposited on the GMR sensing layer 5 obtained in Step 3. The passivation layer 7 is made of Al 2 O 3 material. Copper with a thickness of 50 nm is sputter-deposited on the passivation layer 7 to form the top electrode 6. The manufacturing process of the top electrode 6 is the same as that of the bottom electrode 4.

[0041] Working principle of the present invention: When the analyte is modified onto the biorecognition layer 8, it will cause the magnetoelastic layer 2 to deform, thereby changing its magnetic permeability, disturbing the local magnetic field to change, and further causing the resistance of the GMR sensing layer 5 to change. An electrical signal is output through the top electrode 6 and the bottom electrode 4, thereby realizing the highly sensitive detection of weak biological signals (such as proteins, cells, DNA, etc.).

[0042] Regarding the specific structure of the present invention, it should be noted that the connection relationships between the various component modules adopted in the present invention are definite and achievable. Except for the special descriptions in the embodiments, the specific connection relationships can bring corresponding technical effects, and on the premise of not relying on the execution of corresponding software programs, the technical problems proposed by the present invention can be solved. The models of the components, modules, and specific components, the connection methods between each other, and the conventional usage methods and predictable technical effects brought by the above technical features, except for the specific descriptions, all belong to the patent, journal papers, technical manuals, technical dictionaries, and textbooks that those skilled in the art can obtain before the filing date, or belong to the prior art such as the conventional techniques and common general knowledge in the art, and need not be elaborated. This makes the technical solution provided in this case clear, complete, and achievable, and can reproduce or obtain the corresponding physical product according to this technical means.

[0043] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A biosensor based on magnetic field regulation, characterized in that: It comprises a conductive part (9) and an elastic flexible substrate (1), wherein a magnetic elastic layer (2), a GMR sensing layer (5) and a biometric recognition layer (8) are sequentially deposited on the flexible substrate (1), and the conductive part (9) is in contact with the GMR sensing layer (5); The magnetoelastic layer (2) comprises a closed magnetic circuit with a serpentine structure; An insulating layer (3) is provided 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 biometric recognition layer (8); The surface of the biorecognition 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 an interdigitated electrode pattern.

2. The biosensor based on magnetic field regulation according to claim 1, characterized in that: The flexible substrate (1) comprises a glass substrate, the glass substrate is coated with tin foil, and the tin foil is covered with a PDMS film.

3. The biosensor based on magnetic field regulation according to claim 1, characterized in that: The GMR sensing layer (5) is a multilayer film structure composed of alternating ferromagnetic and non-magnetic metal layers.

4. The biosensor based on magnetic field regulation according to claim 1, characterized in that: The biorecognition layer (8) is made of nano-gold material.

5. The biosensor based on magnetic field regulation according to claim 1, characterized in that: The magnetostriction coefficient λs of the magnetoelastic layer (2) is ≥60 ppm.

6. The biosensor based on magnetic field regulation according to claim 1, characterized in that: The passivation layer (7) is made of Al2O3 material; and the insulating layer (3) is made of SiO2 material.

7. The biosensor based on magnetic field regulation according to claim 1, characterized in that: The magnetoelastic layer (2) is made of magnetoelastic material.

8. The biosensor based on magnetic field regulation according to claim 1, characterized in that: The GMR sensing layer (5) is made of alternately deposited CoFe material and Cu material.

9. A method for manufacturing a biosensor based on magnetic field regulation according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1: preparing a flexible substrate (1); Step 2: depositing a magnetoelastic material on the flexible substrate (1), and forming a serpentine structure using a mask to form a magnetoelastic layer (2); Step 3: alternately depositing a plurality of layers of ferromagnetic material and non-magnetic metal material on the magnetoelastic layer (2) to form a GMR sensing layer (5); Step 4: In an ultra-high vacuum environment, depositing nano-gold material on the GMR sensing layer (5) to obtain a nano-gold layer, and modifying the nano-gold layer with RGD peptide to obtain a biorecognition layer (8); Step 5: installing electrodes, the electrodes are electrically connected to the GMR sensing layer (5); Step 6: Packaging and testing.

10. The method for preparing a biosensor based on magnetic field regulation according to claim 9, characterized in that: An insulating layer (3) is deposited on the surface of the magnetoelastic layer (2) obtained in step 2; and a passivation layer (7) is deposited on the GMR sensing layer (5) obtained in step 3.

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