Optical fiber biosensor for multi-parameter measurement

Abstract

The invention belongs to the technical field of optical fiber biosensors, and discloses an optical fiber biosensor for multi-parameter measurement, which comprises a sensor main body, the sensor main body is a fiber core made of a photonic crystal material, and the periphery of the fiber core is wrapped with a cladding. A plurality of circular air holes of two different sizes are etched in the cladding, two pairs of elliptical holes perpendicular to each other are formed in the portion, close to the fiber core, of the cladding, a first sensing channel is formed by a pair of elliptical holes which are symmetrical left and right, and a second sensing channel is formed by a pair of elliptical holes which are symmetrical up and down. By generating surface plasma resonance (SPR) and loss mode resonance (LMR) effects and utilizing coupling of a waveguide mode and a specific loss mode, simultaneous measurement of multiple parameters such as temperature, solution refractive index, biological solution concentration and the like is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber biosensors, in particular to an optical fiber biosensor for multi-parameter measurement. Background Art

[0002] Optical sensing technology, especially fiber optic biosensors, has attracted wide attention from researchers. Fiber optic biosensors not only have many advantages such as light weight, safety, easy integration, remote real-time detection, corrosion resistance and anti-electromagnetic interference, but also can be widely used in the detection of various physical parameters and biochemical substances, such as temperature, humidity, pressure and ethanol, etc. In particular, fiber optic biosensors based on electromagnetic resonance have the advantages of high sensitivity and strong anti-interference ability, and are widely used in engineering monitoring, medical treatment, environmental monitoring and other fields. Electromagnetic resonance in fiber optic biosensors is mainly divided into surface plasmon resonance (SPR), localized surface plasmon resonance (LSPR), loss mode resonance (LMR), etc. Surface plasmon resonance and localized surface plasmon resonance are a resonance phenomenon caused by surface plasmons. When metal nanoparticles (such as gold or silver) are excited by light, their free electrons resonate with the electromagnetic field of the incident light. This resonance leads to strong light absorption and scattering. Similarly, LMR can also be used as an effective method for label-free sensing, biochemical analyte detection and environmental monitoring. However, the difference is that LSPR occurs in metal nanoparticles, while LMR occurs in metal films. In recent years, many fiber optic biosensors based on loss mode resonance have been reported using different materials and structures, indicating that LMR has a wide range of application potential. For example, Nidhi et al. proposed a ZnO-coated U-shaped fiber optic sensor based on LMR. The device has a sensitivity that is more than 3 times higher than that of conventional optical fiber sensors. LMR can be made of various materials, such as metal oxides (SnO2, ITO, TiO2, etc.) or various polymers, and the LMR transverse TE and TM polarization directions can be generated simultaneously. Compared with SPR, LMR not only maintains the same or even higher sensitivity, but also produces multiple resonance peaks when the film thickness increases and is tuned at a specific wavelength. In addition, optical fiber sensors based on LMR can be manufactured using many different methods, such as layer self-assembly, chemical vapor deposition, wet chemical deposition technology, etc., and have great potential in optical sensing. Although photonic crystal fiber sensors have a series of advantages, there are currently widespread problems such as low sensing accuracy and large crosstalk of sensing signals when measuring multiple parameters simultaneously, which cannot meet the market demand for high-precision, high-reliability, and long-distance temperature and refractive index detection. In response to the existing problems, the present invention proposes an optical fiber biosensor for multi-parameter measurement. Summary of the invention

[0003] In order to solve the problems raised in the above background technology, the present invention provides a fiber optic biosensor for multi-parameter measurement, which adopts different sensing principles of LMR and LSPR and mutually isolated sensing channels to effectively solve the problems of sensor detection reliability and detection accuracy.

[0004] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: an optical fiber biosensor for multi-parameter measurement, comprising a sensor body, wherein the sensor body is a core made of a photonic crystal material, the core is wrapped with a cladding, a plurality of circular air holes of two different sizes are etched inside the cladding, and a portion close to the core has two pairs of mutually perpendicular elliptical holes, wherein a pair of elliptical holes that are symmetrical left and right are temperature sensing elliptical channels for measuring solution temperature, and a pair of elliptical holes that are symmetrical up and down are sensing elliptical channels for measuring solution refractive index and biomass concentration, the first layer of the portion of the refractive index sensing elliptical channel close to the core that contacts the inner wall of the elliptical hole is an indium gallium doped zinc oxide film, a layer of molybdenum disulfide film is plated on the indium gallium doped zinc oxide film, the first layer of the portion of the temperature sensing elliptical channel close to the core that contacts the inner wall of the elliptical hole is a gold film, and the outer wall of the gold film is plated with a layer of gold nanospheres.

[0005] Preferably, the diameter of the core is 9-13 um, and the diameter of the cladding is 100-106 um.

[0006] Preferably, among the plurality of circular air holes, the radius of the circular air holes closer to the fiber core is 12 um, and the radius of the circular air holes farther from the fiber core is 3 um.

[0007] Preferably, the thickness of the indium gallium doped zinc oxide film is 100-140 nm.

[0008] Preferably, the thickness of the MoS film is 5-9 nm.

[0009] Preferably, the diameter of the circular air hole is 10-12 um and the interior of the circular air hole is filled with a thermo-optical sensitive material.

[0010] Compared with the prior art, the present invention has the following beneficial effects: The invention can be used for simultaneous measurement of multiple parameters through the sensor body, and provides an efficient and convenient means for comprehensive detection of solution characteristics. By generating a surface plasma resonance effect, utilizing the coupling of a waveguide mode and a specific loss mode, the refractive index of the solution is accurately measured according to the film layer thickness and the refractive index of the surrounding medium, thereby measuring different biomasses. When LMR is generated, photon energy is absorbed by free electrons of the metal film, destroying total reflection, causing light intensity attenuation in the transmission spectrum, and accurately obtaining the solution refractive index by calculating the displacement of the resonance wavelength. At the same time, due to the generation of the localized surface plasma resonance effect, after the metal nanoparticles are excited by light, the free electron cloud resonates with the incident photoelectric magnetic field, absorbing photon energy, causing the light energy reflected back to the fiber core to be greatly attenuated, changing the optical transmission characteristics of the optical fiber, and realizing real-time detection of external parameters. In addition, utilizing two pairs of mutually perpendicular dual sensing channels inside the photonic crystal fiber, the concentration of a certain object to be measured is calculated by the displacement of the resonance center wavelength in the X polarization direction of the core mode, and the concentration of another object to be measured is calculated by the displacement of the resonance center wavelength in the Y polarization direction of the core mode in another channel, thereby realizing synchronous and accurate measurement of dual parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a structural schematic diagram of the sensor of the present invention; Figure 2 It is a schematic structural diagram of the amplified fiber core part of the sensor of the present invention; Figure 3 Schematic diagram of the loss spectrum of transmitted light changing with different refractive indices; Figure 4 Schematic diagram of the loss spectrum of transmitted light changing with different temperatures.

[0012] In the figure: 1. Fiber core; 2. Cladding; 3. Circular air hole; 4. Temperature sensing elliptical channel; 5. Refractive index sensing elliptical channel; 6. Indium gallium doped zinc oxide film; 7. Molybdenum disulfide film; 8. Gold film; 9. Gold nanospheres. DETAILED DESCRIPTION

[0013] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0014] The embodiment of the present invention provides a fiber optic biosensor for multi-parameter measurement. By introducing structures such as photonic crystal materials, doped thin films, and metal nanoparticles into the fiber optic biosensor, the refractive index and temperature of the solution can be accurately measured, and the sensing technology can be extended to biological tissue analysis, especially for inferring the concentration of colon tissue and liver tissue.

[0015] like Figures 1 to 4 As shown, the optical fiber biosensor provided by the present invention includes a sensor body, the body is a core 1 made of photonic crystal material, the core 1 is wrapped with a cladding 2, a plurality of circular air holes 3 of two different sizes are etched inside the cladding 2, and two pairs of mutually perpendicular elliptical holes are arranged near the core 1. The left-right symmetrical pair of elliptical holes are temperature sensing elliptical channels 4 for measuring the temperature of the solution, and the top-bottom symmetrical pair of elliptical holes are refractive index sensing elliptical channels 5 for measuring the refractive index of the solution. The first layer of the refractive index sensing elliptical channel 5 near the core 1 in contact with the inner wall of the elliptical hole is an indium gallium doped zinc oxide film 6, and a layer of MoS is plated on the indium gallium doped zinc oxide film 6. 2 Film 7. The first layer of the temperature sensing elliptical channel 4 near the fiber core 1 that contacts the inner wall of the elliptical hole is a gold film 8, and the outer wall of the gold film 8 is plated with a layer of gold nanospheres 9.

[0016] Through the optical properties of the fiber optic biosensor, the sensor can simultaneously measure the refractive index and temperature of the solution. Its working principle utilizes the local surface plasmon resonance (LSPR) and local mode resonance (LMR) effects. When the refractive index of the solution or biological tissue changes, the resonant wavelength of the reflection spectrum of the fiber optic biosensor will change significantly, thereby achieving accurate monitoring of the concentration of the solution or biological tissue. The sensor body can be used for dual-parameter measurement, in which the LMR effect is mainly generated by coupling between the waveguide mode and a specific loss mode. This coupling mainly depends on the thickness of the film layer and the refractive index of the surrounding medium. The coupling conditions are mode field overlap and phase matching. When LMR is generated, the energy of the photon will be absorbed by the free electrons in the metal film, which destroys the total reflection and greatly attenuates the energy of the reflected light. The resonance is reduced, causing the light intensity to attenuate in the transmission spectrum. The position of the resonance in the spectrum depends on the optical properties of the LMR supporting film, the film thickness and the refractive index (SRI) of the surrounding medium. The refractive index of the solution can be measured by calculating the displacement of the resonance wavelength. In addition, the LSPR effect is mainly caused by the excitation of metal nanoparticles such as gold or silver by light. At the LSPR resonance wavelength, its free electron cloud resonates with the electromagnetic field of the incident light, and the energy of the photons is absorbed by the free electrons in the metal, causing the light energy reflected back to the fiber core 11 to be greatly attenuated, thereby changing the optical transmission characteristics of the optical fiber. By monitoring the changes in the light intensity, wavelength or other parameters of the optical fiber output light, real-time detection of external parameters can be achieved. The present invention utilizes two pairs of mutually perpendicular double elliptical sensing channels inside the photonic crystal fiber to achieve simultaneous measurement of dual parameters.

[0017] Example 1 like Figure 1 to Figure 2 As shown, the diameter of the core 1 is 9-13um, the diameter of the cladding 2 is 100-106um, the radius of the circular air holes 3 closer to the core 1 among the multiple circular air holes 3 is 5um and the radius of the circular air holes 3 farther from the core 1 is 6um, the thickness of the indium gallium doped zinc oxide 6 film is 100-140nm, the thickness of the molybdenum disulfide film 7 is 5-9nm, the diameter of the circular air holes 3 is 10~12um and the interior of the circular air holes 3 is filled with thermo-optical sensitive materials.

[0018] By adopting photonic crystal optical fiber, the outer diameter of the core 1 is 100um, the material is fused quartz, the center of the core 1 is solid, the diameter of the core 1 is 9um, and 4 pairs of mutually perpendicular elliptical holes are provided in the cladding 2 as sensing channels, with a major semi-axis of 12um and a minor semi-axis of 3um. In addition, the cladding 2 is also provided with 28 circular air holes 3, of which 12 circular air holes 3 closer to the core 1 have a radius of 5um, and 16 circular air holes 3 farther from the core 1 have a radius of 6um.

[0019] Example 2 like Figure 3 to Figure 4 As shown, we first need to detect the response of the fiber optic biosensor to the refractive index of the solution. We tested the sensitivity performance of the solution refractive index between 1.333-1.373. The experimental results show that with the increase of the refractive index, the central wavelength of the resonance peak moves to the right long wavelength direction, and the sensitivity gradually increases, with the highest sensitivity reaching 8250nm / RIU. On this basis, the sensor can infer the concentration of salt water based on the change of the refractive index of the solution. In addition, we also tested the temperature response of the solution, and the test temperature range was 0℃ to 20℃. The experimental results show that with the increase of temperature, the central wavelength of the resonance peak moves to the left short wavelength direction, and the temperature sensitivity reaches 9nm / ℃.

[0020] By adopting the two sensing principles of LMR and LSPR, the dual parameters of solution refractive index and temperature are simultaneously measured on two different sensing channels. The left-right symmetrical elliptical holes of the optical biosensor serve as temperature sensing channels, and their inner walls are plated with indium gallium zinc oxide and MoS2 film 7 to produce LMR effect; and the other pair of elliptical holes that are symmetrical up and down serve as refractive index sensing channels, and their inner walls are plated with gold film 8 and gold nanospheres to produce LSPR effect. Through different sensing principles and channel combinations, the sensor can simultaneously measure the refractive index and temperature of the solution, effectively reducing the mutual interference between the refractive index and salinity, and reducing the overlap problem of the LMR and LSPR resonance peaks, thereby improving the measurement accuracy. In addition, the sensor can not only be used to measure the concentration of saline, but also can infer the concentration of colon tissue and liver tissue based on the refractive index of the solution. By studying the refractive index characteristics of these biological tissues, the optical biosensor can provide more accurate tissue analysis in the medical field, which helps to improve the diagnosis and treatment effects. The combination of two-dimensional material molybdenum disulfide and indium gallium doped zinc oxide film further enhances the refractive index sensitivity of the sensor, making it have a wider application potential.

[0021] Working steps: First, in the preparation process, the precursor material of the photonic crystal fiber can be prepared by pulsed laser deposition, and then the precursor material is heated and stretched into an optical fiber on a drawing tower, and the circular air hole 3 can be formed by hydrofluoric acid (HF) etching. For the deposition method of the LMR excitation film in the vertically symmetrical refractive index sensing elliptical channel 5, the first layer is a 120nm indium gallium doped zinc oxide film 6, and a sol-gel method (Sol-Gel) can be used. In this method, the optical fiber is immersed in a solution containing a precursor of the indium gallium doped zinc oxide material, and then the solution enters the hole through capillary action. Subsequently, the precursor can be converted into the desired indium gallium doped zinc oxide film 6 material by heat treatment, and then the MoS2 film 7 is deposited on the indium gallium doped zinc oxide film 6 by atomic layer deposition to improve the sensor performance, and the interior of the vertically symmetrical refractive index sensing elliptical channel 5 is used to excite the LSPR. The thin film deposition method of the effect is also divided into two steps. The first is the deposition of gold thin film 8. The optical fiber is pretreated first, using nitrogen purge or vacuum suction to ensure that the air holes inside the optical fiber are dry and free of impurities. The optical fiber is then immersed in a solution containing a gold precursor, and then a chemical reducing agent is used to deposit gold on the inner wall of the hole. After the deposition is completed, the optical fiber can be rinsed in pure water to remove any residual chemicals. This is followed by the deposition of gold nanospheres Aunanospheres9. One end of the optical fiber is immersed in a suspension of gold nanospheres Aunanospheres9 to allow the liquid to fill the holes by capillary action. A slight negative pressure or micropump can be used to help the liquid enter, and heat treatment is performed to increase the binding force between Aunanospheres9 and the gold thin film 8. The optical fiber is then rinsed with a pure solvent such as deionized water to remove unfixed or outside the hole gold nanospheres 9.

[0022] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0023] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An optical fiber biosensor for multi-parameter measurement, characterized in that: The invention comprises a sensor body, wherein the sensor body is a fiber core (1) made of a photonic crystal material, the fiber core (1) is wrapped with a cladding (2) on the outside, a plurality of circular air holes (3) of two different sizes are etched inside the cladding (2), and a portion close to the fiber core (1) has two pairs of mutually perpendicular elliptical holes, wherein a pair of elliptical holes that are symmetrical left and right are elliptical sensing channels one (4), and a pair of elliptical holes that are symmetrical up and down are elliptical sensing channels two (5), the first layer of the portion of the refractive index sensing elliptical channel (5) close to the fiber core (1) that contacts the inner wall of the elliptical hole is an indium gallium doped zinc oxide film (6), and a layer of molybdenum disulfide film (7) is plated on the surface of the indium gallium doped zinc oxide film (6), and the first layer of the portion of the temperature sensing elliptical channel (4) close to the fiber core (1) that contacts the inner wall of the elliptical hole is a gold film (8), and the outer wall of the gold film (8) is plated with a layer of gold nanospheres (9).

2. The optical fiber biosensor for multi-parameter measurement according to claim 1, characterized in that: The diameter of the fiber core (1) is 9-13 um, and the diameter of the cladding (2) is 100-106 um.

3. The optical fiber biosensor for multi-parameter measurement according to claim 1, characterized in that: Among the plurality of circular air holes (3), the radius of the circular air holes (3) that are closer to the fiber core (1) is 5 um, and the radius of the circular air holes (3) that are farther from the fiber core (1) is 6 um.

4. The optical fiber biosensor for multi-parameter measurement according to claim 1, characterized in that: The thickness of the indium gallium doped zinc oxide (6) film is 100-140 nm.

5. The optical fiber biosensor for multi-parameter measurement according to claim 1, characterized in that: The thickness of the molybdenum disulfide film (7) is 5-9 nm.

6. The optical fiber biosensor for multi-parameter measurement according to claim 1, characterized in that: The circular air hole (3) has a diameter of 10-12 um and the interior of the circular air hole (3) is filled with a thermo-optical sensitive material.

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