A non-contact trace biochemical sensor based on magnetic surface plasmon

Abstract

The present invention discloses a non-contact trace biochemical sensor of magnetic surface plasmon, including an artificial surface plasmon resonant circuit and a microfluidic cavity; the artificial surface plasmon resonant circuit includes a first resonant pattern layer, a second resonant pattern layer and a dielectric substrate layer; the first resonant pattern layer includes a microstrip line and an artificial surface plasmon structure composed of a central circular sheet and a spiral line; the second resonant pattern layer is a circular hole structure on a large area of ​​metal ground; the artificial surface plasmon structure on the first resonant pattern layer and the circular hole center of the second resonant pattern layer coincide. The sensor realizes a high compression of the equivalent working wavelength through the extremely deep subwavelength field binding characteristics of the artificial surface plasmon resonator, thereby realizing high sensitivity resolution of trace biochemical quantities in the low frequency band; at the same time, through the evanescent field extended by the artificial surface plasmon resonator and the microfluidic cavity with a bottom plate and a cover plate, non-contact sensing of biochemical quantities is realized.

Description

Technical Field

[0001] The invention belongs to the field of sensors, and in particular relates to a non-contact trace biochemical sensor of magnetic surface plasmons. Background Art

[0002] A sensor is a device, module or system that responds to specific parameters in the environment and converts the parameter change information into electrical signals for subsequent information transmission and processing. Sensor technology, together with computer technology and communication technology, is known as the three pillars of information technology.

[0003] The development of resonant sensors in the microwave band can be traced back to the invention of the quartz crystal microbalance in 1959, which can be understood as an active resonant sensor. With the development of microwave printed circuits and microwave integrated circuits, more flexible passive resonant structures such as microstrip loops and radio frequency identification antennas are used for sensing. The concept and design methods of metamaterials bring richer and more flexible options for resonant structures, such as open rings, left-handed and right-handed transmission lines, etc.

[0004] Microwave resonant sensors are used for trace biochemical sensing. Compared with optical and terahertz frequencies, their advantages are: microwave planar circuits are easy to integrate with signal processing and communication circuits, are highly integrated and systematic, and are more robust to environmental noise. Their disadvantages or technical bottlenecks are: (1) the longer wavelength leads to lower resolution of trace biochemical quantities, and (2) the quality factor of microwave resonators is much lower than that of optical microcavities, so their detection capability is relatively low.

[0005] The commonly used solutions to the above two technical bottlenecks are: (1) using shorter waves, such as millimeter waves, for sensing. However, the difficulty, noise, and cost of higher frequency detection are greatly increased. (2) using active amplifier gain to compensate for the loss in the circuit, thereby improving the quality factor. However, the adjustment of the active circuit is more complicated, and the quality factor can only be significantly improved when the gain and loss are offset. If the gain is greater than the loss, the quality factor will also decrease. Summary of the invention

[0006] Purpose of the invention: The present invention aims to provide a non-contact trace biochemical sensor of magnetic surface plasmons. The sensor realizes extremely deep subwavelength field confinement by exciting an electric monopole-magnetic dipole hybrid mode through the interaction between the artificial surface plasmon structure of the first resonant pattern layer and the circular opening of the second resonant pattern layer and through microstrip line excitation. The high resolution of trace biochemical quantities is improved by highly compressing the equivalent wavelength; a high quality factor is achieved, and the detection capability of the resonance peak is improved; at the same time, non-contact biochemical sensing is realized by means of the evanescent field extended by the artificial surface plasmon and the microfluidic cavity with a bottom plate.

[0007] Technical solution: The present invention adopts the following technical solution:

[0008] A non-contact trace biochemical sensor of magnetic surface plasmon comprises an artificial surface plasmon resonant circuit and a microfluidic cavity.

[0009] The sensing signal comes from the resonant frequency of the artificial surface plasmon resonant circuit. The change of the surrounding equivalent dielectric constant causes the resonant frequency to change. The change signal of the surrounding equivalent dielectric constant comes from the change information of the biochemical quantity to be detected in the microfluidic cavity.

[0010] The artificial surface plasmon resonance circuit comprises a first resonance pattern layer, a second resonance pattern layer, and a dielectric substrate layer located between the first resonance pattern layer and the second resonance pattern layer.

[0011] The first resonant pattern layer includes a microstrip line and an artificial surface plasmon structure composed of a central circular piece and a spiral line; the second resonant pattern layer is a circular hole structure on a large-area metal ground.

[0012] The artificial surface plasmon structure on the first resonant pattern layer and the circular hole center of the second resonant pattern layer coincide with each other.

[0013] The geometric parameters involved in the present invention are usually optimized based on simulation results.

[0014] The microfluidic cavity comprises a bottom plate layer, a cavity pattern layer and a cover plate layer. The larger the overlap between the channel area of ​​the microfluidic cavity and the area of ​​the artificial surface plasmon structure, the better.

[0015] The dielectric substrate is a dielectric substrate of a printed circuit or microwave circuit such as FR4, F4B, RO4003, 3003, 4350, RT5880, 5870, 6002, 6006, 6010, 6035, 6202 produced by Rogers, or N4000-13, N4000-13EPSI produced by Nelco, or a semiconductor or dielectric material of Si, SiO2, Al2O3, GaAs, GaN, or a flexible organic dielectric material.

[0016] The first resonant pattern layer and the second resonant pattern layer are single materials or composite materials of copper, tin, gold, silver, chromium, lead, platinum, zinc, aluminum, magnesium or titanium.

[0017] The microfluidic cavity is made of materials such as polydimethylsiloxane and SiO2.

[0018] Beneficial effects: Compared with the prior art, the invention discloses a non-contact type trace biochemical sensor of magnetic surface plasmon, and its principle innovation lies in: (1) through the interaction between the artificial surface plasmon structure of the first resonant pattern layer and the circular hole of the second resonant pattern layer, as well as the microstrip line excitation, the electric monopole-magnetic dipole hybrid mode is excited; (2) extremely deep subwavelength field confinement is achieved, and the resolution ability of low-frequency microwaves for trace biochemical quantities is improved by highly compressing the equivalent wavelength; (3) a high quality factor is achieved, and the detection ability of the resonance peak is improved; (4) non-contact biochemical sensing is achieved by means of the large evanescent field extension space of the low-frequency artificial surface plasmon and the microfluidic cavity with a bottom plate.

[0019] Low-frequency band, passive circuit, convenient detection, low cost and high environmental robustness, based on which the sensing of trace biochemical quantities has practical application value; non-contact biochemical sensing avoids the contamination of sensor chips and has practical application significance. Its sensing sensitivity and detection limit breakthrough are more difficult than contact sensing. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the non-contact trace biochemical sensor disclosed in the present invention;

[0021] Figure 2 It is a schematic diagram of the structure of the artificial surface plasmon resonance circuit disclosed in the present invention;

[0022] Figure 3 1 is the field distribution of the resonant mode in the artificial surface plasmon resonant circuit disclosed in the present invention; a is the vector distribution diagram of the electric field, magnetic field and current, and b is the scalar distribution diagram of the z component of the electric field and magnetic field;

[0023] Figure 4 is a scalar distribution diagram of the electric field and magnetic field z components of the resonant mode in the artificial surface plasmon resonant circuit disclosed in the present invention in the xz plane;

[0024] Figure 5 Schematic diagram of the structure of the cover plate (a), the cavity pattern (b) and the bottom plate (c) of the microfluidic chamber in the embodiment disclosed in the present invention;

[0025] Figure 6 In the embodiment disclosed in the present invention, the artificial surface plasmon resonance circuit is transmitted through (S 21 ) Experimental measurement results of the spectrum;

[0026] Figure 7 A photo of an artificial surface plasmon resonant circuit and a microfluidic cavity in an embodiment disclosed in the present invention;

[0027] Figure 8The experimental data of the non-contact trace biochemical sensor used for measuring glucose solution in the embodiment disclosed in the present invention, where a is the permeability (S) at different glucose concentrations. 21 ) spectrum, and b is the scatter plot and linear fitting diagram of the resonance frequency changing with glucose concentration. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clear, specific implementation examples of the present invention are described below in conjunction with the accompanying drawings.

[0029] The present invention discloses a non-contact type trace biochemical sensor of magnetic surface plasmon, comprising an artificial surface plasmon resonant circuit and a microfluidic cavity, such as Figure 1 The structure of the artificial surface plasmon resonant circuit is shown in Figure 2 , Figure 2 (a) is a front view of the first resonant pattern layer, Figure 2 (b) is a front view of the second resonant pattern layer, Figure 2 (c) is a side view. The first resonant pattern layer includes an excitation microstrip line 1 and an artificial surface plasmon structure 2, both of which are printed metal patterns. The artificial surface plasmon structure 2 is composed of a central disk and two reverse Archimedean spiral structures. The second resonant pattern layer 3 is a circular hole structure on a large area of ​​metal ground, and the center of the circular hole coincides with the center of the artificial surface plasmon structure 2 of the first resonant pattern layer. Between the first resonant pattern layer and the second resonant pattern layer is a dielectric substrate 4.

[0030] The artificial surface plasmon resonant circuit can excite the electric monopole-magnetic dipole hybrid mode under microstrip line excitation through the interaction between the artificial surface plasmon structure of the first resonant pattern layer and the circular holes of the second resonant pattern layer. The mode field distribution is as follows: Figure 3 shown. Figure 3 (a) is the vector distribution of the electric field, magnetic field and circuit. From the vectors of the electric field and magnetic field, it can be seen that the electric field is a symmetrical electric monopole mode, and the magnetic field is a magnetic dipole mode pointing in the z direction; the current vector distribution is consistent with the magnetic field distribution. Figure 3 (b) is the scalar distribution diagram of the z component of the electric field and magnetic field, and its field distribution also shows a typical magnetic dipole mode.

[0031] Figure 4 is the scalar distribution diagram of the electric field and magnetic field z component of the resonant mode in the xz plane. Figure 4 It can be seen that this mode has a long evanescent field extension space. When a microfluidic chamber with a bottom plate is used to separate the artificial surface plasmon resonant circuit and the solution to be tested, while ensuring that the solution to be tested is still within the evanescent field range of the resonant mode, non-contact biochemical sensing can be achieved.

[0032] Figure 5 Schematic diagram of the structure of the microfluidic chamber. To achieve non-contact sensing, the microfluidic chamber consists of a cover plate 5, a cavity pattern layer 6 and a bottom plate 7. The cover plate 5 has two small holes aligned with the cavity pattern layer 6 for the liquid to flow into and out of the capillary.

[0033] Embodiment 1:

[0034] The artificial surface plasmon structure in Example 1 is as follows Figure 2 , where the geometric parameters are: a 0.5mm thick F4B dielectric substrate is used, the width of the 50 ohm microstrip line in the first resonant pattern layer is 1.34mm, the radius of the central disk is 0.5mm, the width of the Archimedean spiral is 0.15mm, and the spiral equation is x=r·t·cos(t), y=r·t·cos(t), where r=0.1, and t varies from 0 to 55. The diameter of the artificial surface plasmon structure formed in this way is 11.15mm measured at the end point of the spiral.

[0035] The above artificial surface plasmon resonance circuit, without loading the microfluidic cavity and the liquid to be tested, has a permeability in air (S 21 The experimental measurement results of the spectrum are as follows Figure 6 The measurement was performed using a Keysight E5063A vector network analyzer. Figure 6 Calculations show that its resonant frequency is 654MHz, the quality factor is 187, and the excitation efficiency is 0.45. Based on the resonant frequency and the diameter of the artificial surface plasmon structure, it can be seen that this resonant mode confines the electromagnetic field within 1 / 41 of the wavelength, achieving a significant compression of the equivalent working wavelength.

[0036] The microfluidic chamber structure in this embodiment is as follows Figure 5 , using polydimethylsiloxane, the bottom plate thickness is 0.5mm, the cavity graphic layer thickness is 0.3mm, the cover plate thickness is 2mm, and the liquid volume in the cavity is 15μL.

[0037] The experimental photos of this embodiment are shown in Figure 7 , including an artificial surface plasmon resonant circuit and a microfluidic cavity to be tested, and the artificial surface plasmon resonant circuit and the microfluidic cavity are bonded with double-sided tape. During the sensing measurement process, glucose solutions of different concentrations are placed in a culture dish, and the syringe is controlled by a syringe pump to extract the solution to be tested. To avoid the influence of the liquid level, the initial value of the amount of solution to be tested drawn each time is the same, and the extraction speed and extraction time are also the same. After extracting the solution to be tested, let it stand for 1 minute until the resonance peak is stable, and then perform the sensing test.

[0038] The curve of the artificial surface plasmon resonance peak changing with glucose concentration is shown in Figure 8Due to the loading of the microfluidic cavity and the sample to be tested, the resonant frequency is further compressed to a low frequency compared to the artificial surface plasmon resonant circuit in the air. In the experiment, deionized water, 10mg / mL, 20mg / mL, 30mg / mL, 40mg / mL and 50mg / mL glucose solutions were measured. Since the volume of the microfluidic cavity used is 15μL, it can be calculated that the measured molar number of glucose corresponding to 10mg / mL, 20mg / mL, 30mg / mL, 40mg / mL and 50 mg / mL solutions is 0.84μM, 1.68μM, 2.52μM, 3.36μM and 4.20μM, respectively. For clarity, Figure 8 (a) only gives the permeability (S) at the first three concentrations. 21 ) spectrum curve, the scattered points and linear fitting of all resonance frequencies changing with the glucose molar number are shown in Figure 8 (b) The resonance peak increases monotonically with the increase of the number of glucose moles. Based on the linear fitting results, the confidence factor value is 3.2, and the standard derivation value of the resonance frequency measurement is 0.1 MHz. It is calculated that the detection limit of glucose in this embodiment is 0.45 μM.

Claims

1. A non-contact trace biochemical sensor based on magnetic surface plasmon, characterized in that: It comprises an artificial surface plasmon resonant circuit; the artificial surface plasmon resonant circuit comprises a first resonant pattern layer, a second resonant pattern layer, and a dielectric substrate layer located between the first resonant pattern layer and the second resonant pattern layer; the first resonant pattern layer comprises a microstrip line and an artificial surface plasmon structure with a circular hole in the center; the second resonant pattern layer is a circular hole structure on a large-area metal ground; the artificial surface plasmon structure on the first resonant pattern layer and the circular hole center of the second resonant pattern layer coincide with each other; The artificial surface plasmon structure consists of a central disk and two reverse Archimedean spiral structures; It also includes a microfluidic cavity arranged above the first resonant pattern layer, which is used to separate the artificial surface plasmon resonant circuit and the solution to be tested during testing, while ensuring that the solution to be tested is still within the evanescent field range of the resonant mode, thereby realizing non-contact biochemical sensing.

2. The non-contact trace biochemical sensor of magnetic surface plasmon according to claim 1, characterized in that: The microfluidic cavity comprises a bottom plate layer, a cavity pattern layer and a cover plate layer, and the bottom plate layer is in contact with the first resonance pattern layer.

3. The non-contact trace biochemical sensor of magnetic surface plasmon according to claim 1, characterized in that: The dielectric substrate is a dielectric substrate of a printed circuit or microwave circuit of FR4, F4B, RO4003, 3003, 4350, RT5880, 5870, 6002, 6006, 6010, 6035, 6202 produced by Rogers, N4000-13, N4000-13EPSI produced by Nelco, or a semiconductor or dielectric material of Si, SiO2, Al2O3, GaAs, GaN, or a flexible organic dielectric material.

4. The non-contact trace biochemical sensor of magnetic surface plasmon according to claim 1, characterized in that: The material of the first resonant pattern layer and the second resonant pattern layer is a single material or a composite material of copper, tin, gold, silver, chromium, lead, platinum, zinc, aluminum, magnesium or titanium.

5. The non-contact trace biochemical sensor of magnetic surface plasmon according to claim 1, characterized in that: The material of the microfluidic cavity is polydimethylsiloxane or SiO2.

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