Biosensor based on off-diagonal GMI effect and magnetic bead detection method

Abstract

The invention relates to the technical field of magnetic sensors, in particular to a biosensor based on the off-diagonal GMI effect and a magnetic bead detection method.The sensor device comprises an off-diagonal giant magneto-impedance sensor, a PI film, an Au film, a crossed detection channel, a magnetic bead A, a magnetic bead B and a signal acquisition system; the non-diagonal giant magneto-impedance sensor is composed of a crossed magnetic core and an induction coil. A PI film is used as a substrate for sputtering Au, an Au film is a sputtered Cr / Au film, and a crossed detection channel is placed on the surface of the Au film and is used as a channel for magnetic bead detection. And the magnetic beads A and B are different superparamagnetic bead nanoparticles. The magnetic bead particles with superparamagnetism can generate a stray field under an external magnetic field, and when the magnetic bead particles are located on the surface of the magnetic sensor, the weak stray field generated by the magnetic beads can be detected by the magnetic sensor. By adopting an in-situ detection mode, high-sensitivity detection of two different magnetic beads can be realized at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic sensors, and in particular to a biosensor based on an off-diagonal GMI effect and a magnetic bead detection method. Background Art

[0002] In the biomedical field, highly sensitive detection of biomolecules is fundamental to disease diagnosis, drug development, and bioscience research. In recent years, with the advancement of nanotechnology and microelectronics, biosensors based on magnetic nanoparticles have garnered widespread attention due to their unique physicochemical properties and biocompatibility. Among them, superparamagnetic nanoparticles, which generate detectable stray fields in an external magnetic field, are ideal biosensor markers.

[0003] Traditional magnetic bead detection methods rely on optical, electrochemical, or mechanical principles, which have limitations in terms of sensitivity, selectivity, and real-time performance. For example, optical methods, while highly sensitive, are susceptible to interference from ambient light; electrochemical methods, while highly selective, may involve complex chemical reactions during the detection process; and mechanical methods, while highly real-time, are relatively low in sensitivity.

[0004] The giant magnetoimpedance (GMI) effect is a phenomenon in which the impedance of a magnetic material changes significantly with the external magnetic field under the influence of an alternating magnetic field. Compared with the traditional giant magnetoimpedance (GMI) effect, the off-diagonal GMI effect offers higher sensitivity and a wider linear range, providing new insights into magnetic bead detection. However, magnetic bead-based biosensors based on the off-diagonal GMI effect are still in the research stage and face challenges such as complex preparation processes and the need to improve detection sensitivity. Summary of the Invention

[0005] The purpose of the present invention is to provide a biosensor and a magnetic bead detection method based on the off-diagonal GMI effect, so that the magnetic bead detection biosensor can achieve multi-channel parallel detection capability, high-sensitivity detection and real-time dynamic monitoring capability.

[0006] To achieve the above objectives, the present invention provides a biosensor based on the off-diagonal GMI effect, comprising an off-diagonal giant magneto-impedance sensor, a PI film, an Au film, a cross-type detection channel, magnetic beads A, magnetic beads B, and a signal acquisition system. The off-diagonal giant magneto-impedance sensor, the PI film, the Au film, and the cross-type detection channel are arranged in sequence from bottom to top, with magnetic beads A and magnetic beads B located in the cross-type detection channel. The signal acquisition system is externally connected to the off-diagonal giant magneto-impedance sensor.

[0007] The non-diagonal giant magneto-impedance sensor consists of a magnetic core and an induction coil. The magnetic core is a Co-based or Fe-based amorphous thin strip with a cross structure. The induction coil is a micro-solenoid coil made using MEMS technology and has 15 turns.

[0008] In the non-diagonal giant magneto-impedance sensor, polyimide (PI) is selected to fill all gaps between the sensitive element and the induction coil.

[0009] The PI film is used as a substrate for sputtering Au, and Cr is used as a buffer layer in the Au film.

[0010] The cross-type detection channel is made by 3D printing, using organic glass as the material, and is made into a cross structure with the same size as the magnetic core, and bonded to the surface of the Au film;

[0011] In the cross-type detection channel, the inlet 10 is connected to the inlet 12, the inlet 11 is connected to the inlet 13, the inlet 10 is opposite to the inlet 13, and the inlet 11 is opposite to the inlet 12.

[0012] Wherein, the signal acquisition system is an SR844 DSP lock-in amplifier.

[0013] Furthermore, the present invention also proposes a biosensor magnetic bead detection method based on the off-diagonal GMI effect, which is applied to the biosensor based on the off-diagonal GMI effect, comprising the following steps:

[0014] Step 1: A cross-structured thin-strip magnetic core is manufactured using a MEMS micromachining process combining photolithography and wet etching;

[0015] Step 2: Use MEMS technology to process a micro three-dimensional solenoid coil structure around the magnetic core;

[0016] Step 3: Sputter a 200 nm thick Cr / Au film on the PI film;

[0017] Step 4: Bond the sputtered PI film to the surface of the micro 3D solenoid coil;

[0018] Step 5: 3D print a cross-shaped detection channel with the same size and structure as the magnetic core and bond it to the surface of the Au film to serve as a channel for magnetic bead detection;

[0019] Step 6: Store magnetic beads A and magnetic beads B in phosphate buffer solution at pH 7.4 with 0.01% Tween-20 and 0.09% NaN3 as protective agents;

[0020] Step 7: Magnetic beads A are introduced from the inlet 11 through a syringe pump, and the stray field signal ΔV1 of the magnetic beads is captured by the sensor; phosphate buffer solution is passed through for washing, and the beads are dried at room temperature;

[0021] Step 8: Magnetic beads A are introduced from the inlet 12 via a syringe pump, and the stray field signal ΔV2 of the magnetic beads is captured by the sensor; phosphate buffer solution is passed through for washing, and the beads are dried at room temperature;

[0022] Step 9: Use the syringe pump to simultaneously introduce magnetic beads A and B from inlet 11 and inlet 12 respectively, and capture the stray field signal ΔV12 of the magnetic beads through the sensor; pass phosphate buffer solution for washing and dry at room temperature.

[0023] Optionally, magnetic beads A and magnetic beads B are different types of superparamagnetic nanoparticles, and an in-situ detection method is used during the detection process.

[0024] The present invention provides a biosensor and magnetic bead detection method based on the off-diagonal GMI effect. The sensor device comprises an off-diagonal giant magneto-impedance (GMI) sensor, a PI film, an Au film, a cross-shaped detection channel, magnetic beads A, magnetic beads B, and a signal acquisition system. The off-diagonal GMI sensor is composed of a cross-shaped magnetic core and an induction coil. The PI film serves as the substrate for sputtered Au, and the Au film is a sputtered Cr / Au film. Because Au has excellent biocompatibility and is easily modified on the surface, making it well-suited for a range of biological applications, magnetic bead samples are detected on the Au film. The cross-shaped detection channel is placed on the surface of the Au film and serves as the channel for magnetic bead detection. Magnetic beads A and B are different superparamagnetic nanoparticles. Superparamagnetic magnetic beads generate stray fields in an external magnetic field. When the magnetic beads are on the surface of the magnetic sensor, the weak stray fields generated by the beads can be detected by the magnetic sensor. The present invention employs in-situ detection, enabling simultaneous and highly sensitive detection of two different magnetic beads. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 3 is a schematic structural diagram of a biosensor based on the off-diagonal GMI effect according to a specific embodiment of the present invention.

[0027] Figure 2 2 is a front view of a biosensor based on the off-diagonal GMI effect in a specific embodiment of the present invention.

[0028] Figure 3 It is a right view of a biosensor based on the off-diagonal GMI effect in a specific embodiment of the present invention.

[0029] Figure 4 FIG. 4 is a top view of a biosensor based on the off-diagonal GMI effect in a specific embodiment of the present invention.

[0030] Figure 5 It is a schematic diagram of the magnetic core structure in the non-diagonal GMI sensor in a specific embodiment of the present invention.

[0031] Figure 6 It is a structural schematic diagram of a cross channel in a specific embodiment of the present invention.

[0032] 1-magnetic core electrode, 2-magnetic core, 3-coil electrode, 4-induction coil, 5-PI film, 6-Au film, 7-cross channel, 8-magnetic bead A, 9-magnetic bead B, 10-entrance 10, 11-entrance 11, 12-entrance 12, 13-entrance 13. DETAILED DESCRIPTION

[0033] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0034] The present invention provides a biosensor based on the off-diagonal GMI effect, comprising an off-diagonal giant magneto-impedance sensor, a PI film, an Au film, a cross-type detection channel, magnetic beads A, magnetic beads B, and a signal acquisition system. The off-diagonal giant magneto-impedance sensor, the PI film, the Au film, and the cross-type detection channel are arranged in sequence from bottom to top, with the magnetic beads A and the magnetic beads B located in the cross-type detection channel. The signal acquisition system is externally connected to the off-diagonal giant magneto-impedance sensor.

[0035] The non-diagonal giant magneto-impedance sensor consists of a magnetic core and an induction coil. The magnetic core is a Co-based or Fe-based amorphous thin strip with a cross structure. The induction coil is a micro-solenoid coil made using MEMS technology and has 15 turns.

[0036] In this embodiment, the cross structure helps improve the performance of the sensor, with higher sensitivity than the traditional meander structure;

[0037] During the preparation of the non-diagonal giant magneto-impedance sensor, polyimide (PI) is selected as the insulating and supporting material, and is filled into all gaps between the sensitive element and the induction coil, thereby providing protection for the device.

[0038] The PI film has the advantages of high temperature resistance, chemical corrosion resistance, and easy peeling, so it is selected as the substrate for sputtering Au.

[0039] The cross-type detection channel is made by 3D printing, using organic glass as the material, and is made into a cross structure with the same size as the magnetic core, and bonded to the surface of the Au film;

[0040] In the cross-type detection channel, the inlet 10 is connected to the inlet 12, the inlet 11 is connected to the inlet 13, the inlet 10 is opposite to the inlet 13, and the inlet 11 is opposite to the inlet 12.

[0041] The signal acquisition system is an SR844 DSP lock-in amplifier.

[0042] The following is further described in conjunction with specific embodiments. Figures 1 to 6 :

[0043] First, the biosensor based on the off-diagonal GMI effect is prepared by the following process:

[0044] 1) A cross-structured thin-strip magnetic core is manufactured using a MEMS micromachining process that combines photolithography and wet etching.

[0045] 2) Substrate pretreatment: ultrasonically clean the glass substrate with acetone, ethanol, and deionized water in sequence, and blow dry with nitrogen;

[0046] 3) Bottom metallization: sputtering 80nm Cr / Cu seed layer, through double-layer photoresist process (18μ

[0047] m / 6μm), electroplating process, respectively constructing the bottom coil conductor and Cu connecting column structure;

[0048] 4) Polyimide encapsulation: After removing the seed layer by dry etching, polyimide is coated and cured and polished to expose the top of the connecting column;

[0049] 5) Pasting the thin-strip magnetic core: The prepared magnetic core is bonded to the bottom coil by diluting polyimide.

[0050] 6) Polishing polyimide: Polyimide is coated for the second time and cured. The surface of the core is made flush with the top surface of the connecting column through rough grinding and polishing process, preparing for the upper metallization.

[0051] 7) Upper metallization: Re-sputter 80nm Cr / Cu seed layer, spin-coat 6μm photoresist, and electroplate Cu connecting column heightening structure and magnetic core electrode after photolithography.

[0052] 8) Top coil preparation: Using the same MEMS process as the bottom layer, electroplate an 18μm Cu top coil conductor to construct a three-dimensional winding structure.

[0053] 9) Electroplate the Cu electrode lead terminals and coat the protective device with polyimide.

[0054] 10) A 200 nm thick Cr / Au film was sputtered on the purchased PI film.

[0055] 11) Using 3D printing technology, a cross-type detection channel with the same size and structure as the magnetic core is produced.

[0056] It is bonded to the surface of the Au film and serves as a channel for magnetic bead detection.

[0057] Furthermore, the present invention proposes a biosensor magnetic bead detection method based on the off-diagonal GMI effect. Superparamagnetic magnetic beads generate a stray field in an external magnetic field. Using an in-situ detection method, when the beads are located on the surface of a magnetic sensor, the weak stray field generated by the beads can be detected by the magnetic sensor.

[0058] The magnetic bead detection method includes the following steps:

[0059] Step 1: Use the MEMS micromachining process combining photolithography and wet etching to make a cross-structured thin-strip magnetic core. Figure 5 shown.

[0060] Step 2: Use MEMS technology to process a micro three-dimensional solenoid coil structure around the magnetic core. This includes sputtering technology, photolithography technology, etching technology, electroplating technology, and polyimide technology.

[0061] Step 3: Sputter a 200 nm thick Cr / Au film on the purchased PI film.

[0062] Step 4: Bond the sputtered PI film to the sensor surface.

[0063] Step 5: Use 3D printing technology to make a cross-type detection channel with the same size and structure as the magnetic core. Figure 6 It is bonded to the Au film surface as a channel for magnetic bead detection.

[0064] Step 6: Store magnetic beads A and magnetic beads B in phosphate buffer solution (PBS) at pH = 7.4, using 0.01% Tween-20 and 0.09% NaN3 as protective agents.

[0065] Step 7: Use a syringe pump to introduce magnetic beads A from inlet 11, and use a sensor to capture the stray field signal ΔV1 of the magnetic beads. Wash with PBS solution and dry at room temperature.

[0066] Step 8: Use a syringe pump to introduce magnetic beads B from inlet 12, and use a sensor to capture the stray field signal ΔV2 of the magnetic beads. Wash with PBS solution and dry at room temperature.

[0067] Step 9: Use the syringe pump to simultaneously inject magnetic beads A and B from inlets 11 and 12 respectively, and measure the stray field signal ΔV of the magnetic beads through the sensor. 12 The cells were captured and washed with PBS solution and dried at room temperature.

[0068] In this example, magnetic bead detection utilizes an in-situ detection method. When the magnetic beads are located on the magnetic sensor surface, the weak stray field generated by the beads can be detected by the magnetic sensor. Three tests were performed, each with magnetic beads A, B, and both A and B, to verify that the sensor can simultaneously detect two different types of magnetic beads.

[0069] In summary, compared with the conventional technology, the present invention has the following beneficial effects:

[0070] 1) Highly Sensitive Detection: Compared to traditional diagonal GMI sensors, off-diagonal GMI sensors offer higher sensitivity and greater geometric design freedom, while also offering superior noise immunity and temperature stability. In particular, thin-ribbon off-diagonal GMI sensors offer a larger surface area than amorphous wire-based off-diagonal sensors, enabling more effective immune responses. The cross-ribbon design further significantly enhances sensor sensitivity.

[0071] 2) Multi-channel parallel detection capability: Traditional methods typically use a single-channel detection mode and cannot distinguish multiple types of magnetic beads simultaneously. This invention uses a cross-type detection channel and dual magnetic bead (A / B) design, combined with an in situ detection strategy, to simultaneously capture the independent signals (ΔV1, ΔV2) and mixed signals (ΔV12) of two different magnetic beads, enabling parallel analysis of multiple target biomolecules, significantly improving detection efficiency and information dimensionality.

[0072] 3) Manufacturing process compatibility and integration: Traditional magnetic sensors are complex to manufacture, making miniaturization and mass production difficult. This invention integrates the magnetic core, coil, and detection channel by combining MEMS processes (photolithography, etching, and electroplating) with 3D printing technology. The precise matching of the 15-turn microsolenoid coil with the cross-structured magnetic core significantly reduces device size (to the millimeter level) while ensuring signal quality, laying the foundation for the development of portable bioassay equipment.

[0073] 4) Real-time dynamic monitoring capability: Traditional methods (such as electrochemical detection) rely on the reaction time of the marker, which limits their real-time performance. This invention uses an in-situ detection mode, using a syringe pump to drive the magnetic bead solution through the detection channel. Combined with the high-frequency signal acquisition of a lock-in amplifier (SR844 DSP), this method can capture transient signals during the flow of magnetic beads and dynamically monitor the binding process between magnetic beads and biomolecules, providing a new method for kinetic research.

[0074] The above disclosure is merely one or more preferred embodiments of the present invention, and certainly cannot be used to limit the scope of the present invention. A person skilled in the art can understand that all or part of the processes of the above embodiments and equivalent changes made in accordance with the claims of the present invention still fall within the scope of the invention.

Claims

1. A biosensor based on the off-diagonal GMI effect, characterized in that: The device comprises a non-diagonal giant magneto-impedance sensor, a PI film, an Au film, a cross-type detection channel, magnetic beads A, magnetic beads B, and a signal acquisition system. The non-diagonal giant magneto-impedance sensor, the PI film, the Au film, and the cross-type detection channel are arranged in sequence from bottom to top, the magnetic beads A and the magnetic beads B are located in the cross-type detection channel, and the signal acquisition system is externally connected to the non-diagonal giant magneto-impedance sensor. The non-diagonal giant magneto-impedance sensor consists of a magnetic core and an induction coil. The magnetic core is a Co-based or Fe-based amorphous thin strip with a cross structure. The induction coil is a micro-solenoid coil made using MEMS technology and has 15 turns.

2. The biosensor based on the off-diagonal GMI effect according to claim 1, wherein: In the non-diagonal giant magneto-impedance sensor, polyimide (PI) is selected to fill all gaps between the sensitive element and the induction coil.

3. The biosensor based on the off-diagonal GMI effect according to claim 2, wherein: The PI film was used as a substrate for sputtering Au, and Cr was used as a buffer layer in the Au film.

4. The biosensor based on the off-diagonal GMI effect according to claim 3, wherein: The cross-type detection channel is made by 3D printing, using organic glass as the material, and is made into a cross structure with the same size as the magnetic core, and bonded to the surface of the Au film; In the cross-type detection channel, the inlet 10 is connected to the inlet 12, the inlet 11 is connected to the inlet 13, the inlet 10 is opposite to the inlet 13, and the inlet 11 is opposite to the inlet 12.

5. The biosensor based on the off-diagonal GMI effect according to claim 4, wherein: The signal acquisition system is an SR844 DSP lock-in amplifier.

6. A biosensor magnetic bead detection method based on the off-diagonal GMI effect, applied to the biosensor based on the off-diagonal GMI effect according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1: A cross-structured thin-strip magnetic core is manufactured using a MEMS micromachining process combining photolithography and wet etching; Step 2: Use MEMS technology to process a micro three-dimensional solenoid coil structure around the magnetic core; Step 3: Sputter a 200 nm thick Cr / Au film on the PI film; Step 4: Bond the sputtered PI film to the surface of the micro 3D solenoid coil; Step 5: 3D print a cross-shaped detection channel with the same size and structure as the magnetic core and bond it to the surface of the Au film to serve as a channel for magnetic bead detection; Step 6: Store magnetic beads A and magnetic beads B in phosphate buffer solution at pH 7.4 with 0.01% Tween-20 and 0.09% NaN3 as protective agents; Step 7: Magnetic beads A are introduced from the inlet 11 through a syringe pump, and the stray field signal ΔV1 of the magnetic beads is captured by the sensor; phosphate buffer solution is passed through for washing, and the beads are dried at room temperature; Step 8: Magnetic beads A are introduced from the inlet 12 via a syringe pump, and the stray field signal ΔV2 of the magnetic beads is captured by the sensor; phosphate buffer solution is passed through for washing, and the beads are dried at room temperature; Step 9: Use the syringe pump to simultaneously inject magnetic beads A and B from inlet 11 and inlet 12 respectively, and measure the stray field signal ΔV of the magnetic beads through the sensor. 12 The cells were captured and washed with phosphate buffer solution and dried at room temperature.

7. The biosensor magnetic bead detection method based on the off-diagonal GMI effect according to claim 6, wherein: Magnetic beads A and magnetic beads B are different types of superparamagnetic nanoparticles, and in situ detection is used during the detection process.

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