Flexible electromagnetic metamaterial biochemical sensor and preparation method thereof

Abstract

The invention discloses a flexible electromagnetic metamaterial biochemical sensor and a preparation method thereof. The flexible electromagnetic metamaterial sequentially comprises a metal microstructure layer, a dielectric layer and a metal reflecting layer from bottom to top, wherein the metal microstructure layer is composed of unit structures which are arranged periodically; the unit structures are elliptical; the dielectric layer is a polyimide film. According to the wearable non-invasive detection method for the analyte in the sweat, the wearable sensor is a device which can be worn or matched with the skin of the human body, has the characteristics of flexibility, light weight and biocompatibility, can detect indexes closely related to the human body, and can realize early prevention of diseases.

Description

Technical Field

[0001] The present application relates to the technical field of electromagnetic metamaterial sensors, and in particular to a flexible electromagnetic metamaterial biochemical sensor and a preparation method thereof. Background Art

[0002] Human sweat is rich in physiological information, and changes in the concentration of biomarkers in sweat often reflect a person's health. Traditional serum testing methods can cause discomfort. With the innovation of emerging materials, flexible materials have attracted significant attention. The unique advantages of flexible electronics, such as ultrathinness, bendability, and lightweight, pave the way for the development of next-generation human motion detection, health monitoring, and wearable devices.

[0003] Electromagnetic waves can be divided into different bands based on their wavelength and frequency. Terahertz waves, for example, have frequencies between 0.1 and 10 THz. Conventional materials in nature have a weak response to terahertz waves, but metamaterials can effectively address this problem. Metamaterials are artificially designed composite materials with periodic or aperiodic structural units. When the coupling mode of terahertz waves matches theirs, they induce significant terahertz electromagnetic field concentration and enhancement, resulting in distinct terahertz resonance peaks in the spectrum. By adjusting the surface structure and dimensions of the metamaterial, the metamaterial's resonance peak can be modulated to the intrinsic absorption peak of the substance being measured in the terahertz band, achieving coupling between the metamaterial's resonance peak and the intrinsic absorption peak of the substance being measured. Terahertz metamaterial sensing requires a very low dose of the substance being measured, enabling the detection of trace amounts of substances and significantly reducing costs. Sensing is achieved by detecting the shift in the metamaterial's resonance frequency caused by changes in the refractive index of the substance being measured, eliminating the need for material labeling.

[0004] Although metamaterial sensors can detect trace substances using spectrum analysis, their sensitivity and resolution are still quite limited. In order to further improve the sensing performance of metamaterial sensors, it is urgent to design a metamaterial biochemical sensor with high quality factor and high sensitivity. Summary of the Invention

[0005] To address the aforementioned deficiencies in the field, this application aims to provide a flexible electromagnetic metamaterial biochemical sensor and its preparation method. This application proposes a wearable, non-invasive method for detecting analytes in sweat. The wearable sensor is a device that can be worn or otherwise adapted to human skin. It is flexible, lightweight, and biocompatible, capable of detecting indicators closely related to the human body and enabling early prevention of disease.

[0006] According to one aspect of the present application, a flexible electromagnetic metamaterial biochemical sensor is provided, characterized in that it comprises, from top to bottom: a metal microstructure layer, a dielectric layer, and a metal reflective layer;

[0007] The metal microstructure layer is composed of periodically arranged unit structures, and the unit structures are elliptical;

[0008] The dielectric layer is a polyimide film.

[0009] According to some embodiments of the present application, the material of the metal microstructure layer is gold.

[0010] According to some embodiments of the present application, the material of the metal reflective layer is gold.

[0011] According to some embodiments of the present application, the thickness of the metal microstructure layer is 200-500 nm.

[0012] According to some embodiments of the present application, the thickness of the metal reflective layer is 200-500nm, and the skin depth of gold in the terahertz band is 200nm. When the thickness of the gold layer is greater than 200nm, it can be ensured that the terahertz wave cannot penetrate the metal reflective layer, thereby ensuring the transmittance is 0.

[0013] According to some embodiments of the present application, when the thickness of the dielectric layer is 100 μm, the simulated absorption rate is the best, and the absorption rate can reach 99%.

[0014] According to some embodiments of the present application, the major axis of the elliptical unit structure of the metal microstructure layer is 300 μm, and the minor axis is 150 μm.

[0015] According to some embodiments of the present application, a period of the periodic arrangement is 400 μm.

[0016] According to another aspect of the present application, a method for preparing the above-mentioned flexible electromagnetic metamaterial biochemical sensor is provided, comprising:

[0017] pre-treating the polyimide film to obtain a dielectric layer;

[0018] Using an ion beam sputtering device to grow a metal microstructure layer and the metal reflective layer on the upper and lower surfaces of the dielectric layer respectively;

[0019] Femtosecond laser technology is used to process the metal microstructure layer.

[0020] According to some embodiments of the present application, pre-treating the polyimide film to obtain the dielectric layer includes:

[0021] The polyimide film was cleaned with ethanol and then placed in ultrapure water for ultrasonic cleaning to obtain the dielectric layer.

[0022] Compared with the prior art, this application has at least the following beneficial effects:

[0023] The flexible electromagnetic metamaterial biochemical sensor of the present application has a simple structure and is prepared using femtosecond laser processing technology, with low processing difficulty.

[0024] The flexible electromagnetic metamaterial biosensor described in this application uses a flexible substrate that conforms to curved surfaces and can be attached to the skin to facilitate the collection of sweat samples and in-situ detection. It is flexible, lightweight, and biocompatible, capable of detecting indicators closely related to the human body and enabling early prevention of diseases. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic structural diagram of a flexible electromagnetic metamaterial biochemical sensor according to an exemplary embodiment of the present application.

[0026] Figure 2 This is a schematic cross-sectional view of the flexible electromagnetic metamaterial biochemical sensor according to an exemplary embodiment of the present application.

[0027] Figure 3 Schematic diagram of the preparation process of the flexible electromagnetic metamaterial biochemical sensor according to an exemplary embodiment of the present application.

[0028] Figure 4 The surface current and magnetic field distribution of the flexible electromagnetic metamaterial biochemical sensor according to an exemplary embodiment of the present application.

[0029] Figure 5 This is a microscopic image of the flexible electromagnetic metamaterial biochemical sensor according to an exemplary embodiment of the present application.

[0030] Figure 6 The flexible electromagnetic metamaterial biochemical sensor according to the exemplary embodiment of the present application simulates the red shift of the resonant peak of the refractive index change.

[0031] Figure 7 This is a comparison between the bare sensor spectrum and simulation of the flexible electromagnetic metamaterial biochemical sensor according to an exemplary embodiment of this application.

[0032] Figure 8 This is the frequency shift curve of the flexible electromagnetic metamaterial biochemical sensor with different sample concentrations according to an exemplary embodiment of the present application.

[0033] Figure 9 This is an example embodiment of the present application showing the absorption rate of a flexible electromagnetic metamaterial biochemical sensor at different bending radii.

[0034] Figure 10 This is a schematic diagram of in-situ detection of a flexible electromagnetic metamaterial biosensor according to an exemplary embodiment of the present application. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions of this application in conjunction with the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0036] It is particularly important to note that similar substitutions and modifications made with respect to the present application are obvious to those skilled in the art and are considered to be included in the present application. Relevant persons can obviously modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of the present application to implement and apply the technology of the present application. Obviously, the embodiments described are only some of the embodiments of the present application, and not all of them.

[0037] If no specific conditions are specified in this application, the preparation shall be carried out in accordance with conventional conditions or the conditions recommended by the manufacturer. The raw materials or excipients used, as well as the reagents or instruments used, for which the manufacturers are not specified, are all conventional products that can be obtained commercially.

[0038] The following is a detailed description of this application.

[0039] Existing terahertz metamaterial biochemical sensing technologies primarily use rigid-substrate metamaterials that cannot conform to curved surfaces. This requires dripping sweat test substances onto the metamaterial, making in-situ detection of biochemical substances in sweat impossible. The flexible electromagnetic metamaterial biosensor provided in this application has a simple structure and is fabricated using femtosecond laser processing technology, making it easy to process. It uses a flexible substrate that can conform to curved surfaces and can be attached to the skin to facilitate the collection of sweat samples and in-situ detection.

[0040] like Figure 1 、 Figure 2 As shown, the metamaterial sensor prepared in this application is a classic sandwich structure, in which the middle layer is a dielectric layer, the material of which is a polyimide film; the upper layer is a metal microstructure layer, the material of which is gold; the lower layer is a metal reflective layer, the material of which is gold; the coating of the upper and lower layers can be operated using an ion beam metal sputtering device.

[0041] Among them, flexible polymer polyimide has a low dielectric constant of 3.4. Choosing a flexible polymer material with a low dielectric constant as the dielectric layer will greatly reduce the loss of the metamaterial to terahertz waves, greatly improve the sensitivity, and improve the performance of the sensor.

[0042] This application also uses femtosecond laser processing technology to pattern the metal microstructure layer. Femtosecond laser processing does not require mask operation, has high processing efficiency, ultra-short pulse width, ultra-strong instantaneous peak power, high processing precision, and can achieve one-time molding preparation.

[0043] This application utilizes femtosecond laser technology to replace commonly used photolithography and wet etching techniques. This overcomes the complexities of photolithography, which requires masking, developing, and stripping, as well as the poor fidelity and uneven line width of wet etching. Femtosecond laser processing technology enables one-step device fabrication with fewer steps, simple operation, and high precision. This eliminates the need for complex masking, developing, and stripping operations, reducing manufacturing costs.

[0044] Example

[0045] Flexible electromagnetic metamaterial biosensor fabrication for this application:

[0046] Step 1: Take a 2cm*2cm, 100μm thick polyimide film, clean the film surface with ethanol, then place the film in ultrapure water for ultrasonic cleaning, and then blow dry with a blower;

[0047] Step 2: Use an ion beam sputtering device to metal-plate the cleaned polyimide film, and plate 200nm of gold on the upper and lower surfaces of the polyimide film respectively; the upper surface gold layer serves as the periodic structure layer, the polyimide serves as the dielectric layer, and the lower surface gold layer serves as the metal ground layer;

[0048] Step 3: Place the gold-plated sample on the femtosecond laser processing platform, draw the graphics to be processed on the CAD software, import the drawn graphics into the femtosecond laser processing software, and then debug the laser processing parameters. The femtosecond laser wavelength is 1030nm, the power is 21mw, the repetition frequency is 20kHz, the objective lens magnification is 10 times, and the scanning speed is 5mm / s for processing.

[0049] Experimental example

[0050] The metamaterial absorber is simulated by CST software. The metamaterial absorber is a typical three-layer structure. The metal ground layer and the metal metamaterial layer are composed of low-loss gold with a thickness of 200 nanometers. The middle dielectric layer is a flexible polyimide with a thickness of 100 microns. The unit structure of the metal metamaterial layer is elliptical, such as Figure 1 shown.

[0051] From the surface electromagnetic field distribution of the metamaterial, it can be seen that obvious charge accumulation and magnetic field enhancement can be observed at both ends of the elliptical major axis at the resonant frequency. The metamaterial sensor couples to the terahertz frequency to produce an obvious terahertz resonance peak. This near-field enhancement will improve the interaction between the electromagnetic field and matter, thereby achieving high-sensitivity detection, such as Figure 4 shown.

[0052] Metamaterial sensors are prepared by femtosecond laser processing, and the image of the device under a light microscope is as follows: Figure 5 shown.

[0053] As the simulated refractive index increases, R2 will undergo an obvious red shift, such as Figure 6 shown.

[0054] The spectrum of the bare sensor is shown in the figure. Compared with the simulation results, the position of the resonance peak has a slight shift, such as Figure 7 shown.

[0055] Among them, red shift refers to the center frequency of the resonance peak moving toward lower frequencies. If the sensor has sensing performance, the center frequency will move when the simulated refractive index increases. When the refractive index changes, the more obvious the red shift, the higher the sensitivity. Due to inevitable processing errors, the measured resonance peak of the prepared device will have a slight deviation from the simulation result.

[0056] Sensor performance test of the embodiment of this application:

[0057] Step 1: First, prepare solutions of the test substance with different concentrations, from low to high, namely concentration 1, concentration 2, concentration 3, and concentration 4. First, use a pipette to drop the solution of concentration 1 onto the metamaterial sensor. Then, place the metamaterial with the solution on a heating table to evaporate the water. After removing the water, place the metamaterial in a frequency domain terahertz spectrometer for testing to obtain the spectral curve of concentration 1.

[0058] Step 2: Place the metamaterial sensor tested in step 1 in ultrapure water for immersion and ultrasonic cleaning to completely remove the object to be tested.

[0059] Step 3: Repeat the above two steps to obtain the spectral curves of concentration 2, concentration 3, and concentration 4 respectively (as shown in Figure 3). Figure 8 shown).

[0060] The experimental results show that when the sample to be tested is added, the resonance peak shows an obvious red shift as the concentration increases. The experimental results are consistent with the simulation results, such as Figure 8 shown.

[0061] When the bending radius of the metamaterial is changed, it is found that the position of its resonance peak does not change, such as Figure 9 As shown in the figure, the position of the resonance peak does not change, and the center frequency remains unchanged, indicating that when the bending radius of the sensor of the present application is changed, it is guaranteed that when it is applied to a wearable device integrated on the skin, regardless of the bending radius, the frequency shift is the same when the concentration changes, and the sensing ability is stable.

[0062] Therefore, the characteristic that the position of the absorption peak does not change with different bending can be used for biochemical detection on curved surfaces. After adding samples of the same concentration, no matter how the curvature of the metamaterial changes, the frequency shift of the resonance peak remains unchanged when a substance of a specific concentration is added. It can be used to attach to the skin to detect biochemical substances in sweat, realizing the function of flexible wearability. One or more through holes are processed in the metamaterial structure for sweat transmission and in-situ detection, such as Figure 10 Electrochemical methods require sample labeling and modification, which can damage the activity of the analyte; chromatography-mass spectrometry requires sample pretreatment and is subject to significant environmental interference. The terahertz spectroscopy analysis method of this application is convenient to operate, does not require labeling and modification, and has high detection resolution and fast detection speed.

[0063] In addition, this application found that the surface current formed by the terahertz wave in the elliptical structure has a higher energy density, and is enriched and charged at both ends of the ellipse to produce obvious electric dipoles. Obvious charge accumulation and magnetic field enhancement can be observed at both ends of the ellipse. No similar terahertz photoelectric conversion effect was found in other shapes, such as circular structures. The resonant coupling response of the terahertz wave and the elliptical structure is stronger than that of the circular structure.

[0064] The above embodiments are only intended to help understand the method and core concept of the present application. It should be noted that, for those skilled in the art, without departing from the principles of the present application, several improvements and modifications may be made to the present application, and such improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A flexible electromagnetic metamaterial biochemical sensor, characterized in that: From top to bottom, it includes: metal microstructure layer, dielectric layer, metal reflective layer; Wherein, the metal microstructure layer is composed of periodically arranged unit structures, and the unit structures are elliptical; The dielectric layer is a polyimide film.

2. The flexible electromagnetic metamaterial biochemical sensor according to claim 1, characterized in that: The material of the metal microstructure layer is gold.

3. The flexible electromagnetic metamaterial biochemical sensor according to claim 1, characterized in that: The material of the metal reflective layer is gold.

4. The flexible electromagnetic metamaterial biochemical sensor according to claim 1 or 2, characterized in that: The thickness of the metal microstructure layer is 200-500 nm.

5. The flexible electromagnetic metamaterial biochemical sensor according to claim 1 or 3, characterized in that: The thickness of the metal reflective layer is 200-500 nm.

6. The flexible electromagnetic metamaterial biochemical sensor according to claim 1, characterized in that: The thickness of the dielectric layer is 100 μm.

7. The flexible electromagnetic metamaterial biochemical sensor according to claim 4, characterized in that: The major axis of the elliptical unit structure of the metal microstructure layer is 300 μm, and the minor axis is 150 μm.

8. The flexible electromagnetic metamaterial biochemical sensor according to claim 4 or 7, characterized in that: The period of the periodic arrangement is 400 μm.

9. A method for preparing the flexible electromagnetic metamaterial biochemical sensor according to any one of claims 1 to 8, characterized in that: include: pre-treating the polyimide film to obtain the dielectric layer; Using an ion beam sputtering device to grow the metal microstructure layer and the metal reflective layer respectively on the upper and lower surfaces of the dielectric layer; The metal microstructure layer is processed by adopting femtosecond laser technology.

10. The preparation method according to claim 9, characterized in that Pre-treating the polyimide film to obtain the dielectric layer includes: The polyimide film was cleaned with ethanol and then placed in ultrapure water for ultrasonic cleaning to obtain the dielectric layer.

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