CN117849006A - A detection device based on the acidity of hydrogel-coated optical fiber misaligned splicing solution - Google Patents

Abstract

The present invention discloses a detection device based on the acidity of the solution of the hydrogel-coated optical fiber misaligned splicing. The device adopts the hydrogel-coated optical fiber misaligned splicing structure. The optical fiber misaligned splicing structure is as follows: a section of single-mode optical fiber is laterally offset and embedded into the joint of the coreless optical fiber; the hydrogel is dip-coated on the surface of the silanized misaligned splicing structure fiber to obtain a liquid pH sensing device stably adsorbed by the hydrogel; the detection device includes two major parts: a coreless optical fiber-single-mode optical fiber-coreless optical fiber misaligned fusion structure and a hydrogel coated on the surface of the silanized fiber. The present invention enhances the sensitivity and structural stability of the optical fiber solution pH detection device, improves the embeddability of the sensing structure and the ability of the system to detect in harsh liquid environments.

Description

A detection device based on the acidity of hydrogel-coated optical fiber misaligned splicing solution

Technical Field

The invention relates to the technical field of optical fiber sensing detection, and in particular to a detection device based on the acidity of a hydrogel-coated optical fiber misaligned splicing solution.

Background technique

Fiber optic liquid sensing is widely used in the analysis and detection of toxic and harmful liquids in industries such as environmental management, chemical production, and biomedicine due to its advantages of small size, high sensitivity, low cost, corrosion resistance, and anti-electromagnetic interference. Compared with the sensing splicing structure coated with hydrogel materials, the traditional splicing structure fiber optic liquid sensing system has a poor effect between the light field and the liquid medium to be measured, resulting in a decrease in the detection sensitivity of the system.

Summary of the invention

In order to enhance the sensitivity and structural stability of the optical fiber solution acidity detection device, improve the embeddability of the sensing structure and the ability of the system to detect in harsh liquid environments, the present invention proposes a solution acidity detection device based on a hydrogel-coated optical fiber mis-splicing structure by coating hydrogel on the surface of the silanized fiber, as described below:

A device for detecting the acidity of a hydrogel-coated optical fiber misaligned splicing solution, wherein the device adopts a hydrogel-coated optical fiber misaligned splicing structure.

The optical fiber dislocation splicing structure is as follows: a section of single-mode optical fiber is laterally offset and embedded into the joint of the coreless optical fiber; a hydrogel is dip-coated on the surface of the silanized dislocation splicing structure fiber to obtain a liquid pH sensing device stably adsorbed by the hydrogel;

The detection device comprises two major parts: a coreless optical fiber-single-mode optical fiber-coreless optical fiber dislocation fusion structure and a hydrogel coated on the surface of the silanized fiber.

Among them, the detection device is placed in the detection liquid. When the signal light output by the broadband light source with a working band of 1500-1600nm is emitted through the introduction of single-mode optical fiber and the introduction of coreless optical fiber, the light is separated into two parts and reaches the laterally offset single-mode optical fiber core and the hydrogel-coated microcavity area respectively. After the light field signal interacts with the liquid medium in this area, it is coupled to the lead-out coreless optical fiber and generates an interference spectrum output in the lead-out single-mode optical fiber.

Wherein, the ratio and implementation process of the hydrogel are as follows:

A 30% solution of acrylamide AAm polymerization monomer and methylene bisacrylamide BAAM crosslinker was prepared in a ratio of 29:1, and 5.5 mL of deionized water and 1.2 mL of AAm/BAAM mixed solution were mixed evenly.

Take 0.1 mL of methacrylic acid liquid and add it to the liquid mixed in the previous step, then add 0.1 mL of N,N,N',N'-tetraethylethylenediamine TEMED and mix well; take 0.25 mL of 5% ammonium persulfate APS aqueous solution and add it to the above mixed liquid and stir well; pour the mixed liquid into a sealed bottle, expel the air in the bottle and seal it;

The polymerization reaction is completely completed under the condition of 20 hours of light exposure, and the polymerized hydrogel is rinsed in deionized water to obtain a non-toxic, odorless and transparent hydrogel.

Wherein, the ratio and implementation process of the silanization are as follows:

Mix anhydrous ethanol and deionized water in equal volumes at a ratio of 1:1, add an appropriate amount of glacial acetic acid to adjust the pH of the ethanol solution to 3.5, and add a certain amount of silane coupling agent KH-570 to the above solution to prepare a mixed solution of 3%-4% KH-570 by volume;

The configured solution was mechanically stirred for 2 hours, and the optical fiber hydrogel-coated section was immersed in the solution for 10 minutes to achieve silanization. The optical fiber structure was then taken out and the surface of the structure was properly cleaned with a mixture of equal volumes of deionized water and ethanol. The cleaned optical fiber structure was dried and placed for 1 hour to complete the silanization.

The beneficial effects of the technical solution provided by the present invention are:

1. The present invention adopts a single-mode optical fiber coreless optical fiber staggered splicing structure combined with hydrogel coating to construct a sensor device. The staggered splicing structure can effectively increase the effect between the light field and the liquid to be measured, and the pH-sensitive coated hydrogel film can effectively increase the sensitivity of system detection; the staggered splicing structure can effectively reduce the manufacturing cost of the liquid sensing device, improve the system's embeddability and the possibility of deployment in harsh environments;

2. The present invention can detect the pH value of acidic liquids simply and quickly. It has a stable structure, a simple implementation method, and a good foundation for technological transformation. It is expected to be widely used in monitoring liquid components such as industrial wastewater, microbial environmental testing, and agricultural environmental testing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of a hydrogel-coated staggered optical fiber liquid sensing structure;

FIG2 is a schematic cross-sectional view of a dislocation welding structure;

FIG3 is a schematic diagram of a broadband light source spectrum and corresponding transmission spectra of solutions with different pH values.

In the accompanying drawings, the components represented by the reference numerals are listed as follows:

1. Introducing single-mode optical fiber; 2. Introducing coreless optical fiber; 3. Single-mode optical fiber cladding;

4. Single-mode optical fiber core; 5. Lead out coreless optical fiber; 6. Lead out single-mode optical fiber;

7. Hydrogel coating area.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention are described in further detail below.

Compared with the traditional optical fiber splicing structure, the design of the hydrogel-coated optical fiber staggered splicing structure sensing system can effectively improve the sensitivity of liquid detection and reduce the use cost of the optical fiber liquid pH detection system.

Ordinary single-mode fiber (SMF) and coreless fiber (NCF) are commonly used fiber types based on fiber splicing modal interferometers. The fiber microsensing structure using coreless-single-mode-coreless sequential splicing can be easily embedded in liquid detection systems for chemical, biological and industrial applications. By simply offsetting a section of single-mode fiber 1 laterally and embedding it into the connector of the coreless fiber, an open fiber microcavity based on the offset fusion modal interferometer is constructed. While effectively enhancing the interaction between the fiber light field and the liquid medium to be measured, it has great application potential in improving the sensitivity of the liquid detection system. Figure 2 is a cross-sectional schematic diagram of the offset fusion structure based on single-mode fiber and coreless fiber.

Due to the swelling and shrinkage characteristics of the pH-sensitive membrane of the hydrogel, its refractive index can be changed by the pH of the external solution. Polyacrylamide (PAAm) hydrogel is widely used due to its wide pH response range and high sensitivity. By controlling the material ratio and combining the polymerization reaction, non-toxic, odorless and transparent hydrogel materials can be easily and quickly prepared. The specific ratio and implementation process of the hydrogel are as follows: acrylamide AAm (polymerization monomer) and methylene bisacrylamide BAAM (cross-linking agent) are configured into a 29:1 solution with a concentration of 30%, and 5.5 mL of deionized water and 1.2 mL of AAm/BAAM mixed solution are absorbed and mixed evenly. Take 0.1 mL of methacrylic acid (polymerization monomer) liquid and add it to the liquid mixed in the previous step, and then add 0.1 mL of N,N,N',N'-tetraethylethylenediamine TEMED (catalyst) and mix evenly; absorb 0.25 mL of 5% (mass fraction) ammonium persulfate APS (initiator) aqueous solution and add it to the above mixed solution and stir it quickly and evenly, and quickly pour the mixed solution into a sealed bottle, expel the air in the bottle and seal it. The polymerization reaction is completely completed under the condition of 20 hours of light exposure. The polymerized hydrogel is rinsed in deionized water to wash away the unreacted residual substances. A non-toxic, odorless and transparent hydrogel can be obtained. Silanization will establish chemical bonds between organic and inorganic substances to enhance the adsorption of hydrogel on the fiber surface; the specific operation process of silanization is: first, anhydrous ethanol and deionized water are mixed in equal volumes of 1:1, and then an appropriate amount of glacial acetic acid is added to adjust the pH of the ethanol solution to 3.5, and a certain amount of silane coupling agent KH-570 is added to the above solution to prepare a 3%-4% KH-570 mixed solution. The solution after configuration is mechanically stirred for 2 hours, and then the optical fiber hydrogel coating section is placed in the solution and immersed for 10 minutes to achieve silanization, and then the optical fiber structure is taken out and the surface of the structure is properly cleaned with an equal volume mixture of deionized water and ethanol. The cleaned optical fiber structure is dried and placed for 1 hour to complete the silanization. By dip-coating the hydrogel on the surface of the silanized dislocation splicing structure fiber, a liquid pH sensing device with stable hydrogel adsorption can be easily obtained. In the near future, with the development and use of advanced layer-by-layer self-assembled micro/nano coating tools, the parameters of the sensing system can be further optimized by precisely controlling the position, thickness and uniformity of the hydrogel coating, and a highly sensitive liquid pH detection device can be realized, which will promote the widespread application of the hydrogel-coated optical fiber staggered splicing structure in the field of optical fiber sensing. Figure 1 is a schematic diagram of the staggered splicing optical fiber liquid sensing structure based on hydrogel coating.

Compared with ordinary optical fiber sensors, the optical fiber solution detection system using hydrogel combined with offset fusion structure can greatly reduce the volume of the sensing system while achieving a stable sensing structure, effectively improving the solution detection sensitivity of the system, and has the advantages of simple structure, convenient preparation, and small size. At the same time, the optical fiber solution sensing system has good embeddability and stability, and can be deployed in various harsh liquid environments. It is of great significance to improve the performance of the optical fiber liquid sensing system and expand the pH detection coverage of the optical fiber sensing system.

The embodiment of the present invention mainly utilizes the tiny core offset caused by the misaligned splicing of coreless optical fiber and single-mode optical fiber, which leads to the response law of the cladding mode excited by mode field mismatch to the external refractive index, and the refractive index response law of the hydrogel coating to the external solution pH, and effectively improves the sensitivity of the liquid detection device through misaligned splicing and hydrogel coating. Due to the existence of the misaligned splicing structure of the coated hydrogel, the effect between the light field and the liquid medium can be effectively increased. This device can effectively increase the sensitivity of liquid pH detection and greatly enrich the applicable environment of liquid sensors.

First, the coating of the single-mode fiber and the coreless fiber are stripped and the end faces are cut to construct the structural basis of the offset fusion. A small section of the coreless fiber and the lead-in single-mode fiber are spliced by simple discharge fusion by a fusion splicer, and then the processed single-mode coreless section is non-coaxially spliced with a small section of single-mode fiber, and the offset is about half of the fiber diameter to expose the core part of the single-mode fiber; then the other end face of the spliced single-mode fiber is offset again with the coreless fiber-lead-out single-mode fiber structure to achieve a symmetrical distribution of the two offset splicing points, as shown in Figure 1. Subsequently, the prepared fiber microstructure is silanized to ensure the stable coating of the hydrogel. The offset spliced fiber sensing structure with hydrogel coating is shown in Figure 1. The offset single-mode fiber sandwiched between the coaxial coreless fibers forms an open optical microcavity, which is filled with coated hydrogel and its length is determined by the length of the offset single-mode fiber. When light is emitted through the introduction of the coreless fiber, the light is separated into two parts, transmitted in the offset single-mode fiber and the microcavity hydrogel, and then coupled to the lead-out coreless fiber part, where the two light beams produce an interference spectrum output. Due to the high refractive index response of the hydrogel to the solution pH, the change in the external solution pH can effectively change the refractive index at the microcavity hydrogel, thereby affecting the optical path difference of the two light transmission paths, thereby causing the shift of the interference spectrum. Therefore, by detecting the one-to-one correspondence between the solution pH change and the spectral shift point, the shift amount and the corresponding solution pH change can be detected.

As shown in Figure 1, the hydrogel-coated optical fiber misaligned splicing solution acidity detection device of the embodiment of the present invention mainly includes: a coreless optical fiber-single-mode optical fiber-coreless optical fiber misaligned fusion structure and a hydrogel coated on the surface of the silanized fiber. The organic combination of the two realizes the liquid pH high-sensitivity detection device proposed in the embodiment of the present invention.

As shown in Figure 1, the offset fusion structure includes: single-mode optical fibers (1, 4 and 6) with a core/cladding diameter of 10/125μm, and coreless optical fibers (2 and 5) with a cladding diameter of 125μm. Among them, the length of the coreless optical fiber is about 2mm, the length of the single-mode optical fiber with an offset splicing structure is 803.7μm, and the lateral offset distance of the core is about 62.5μm. The spliced fiber structure needs to be immersed in the silanization liquid for about 10 minutes, and after cleaning, it is taken out and dried for 1 hour to complete the silanization of the fiber surface. The coated hydrogel is prepared in the laboratory by a polymerization reaction using a fixed ratio of polymerization monomers and cross-linking agents, and is coated on the silanized fiber surface by dip coating, and the uniformity of the coating layer is ensured by a mold. The thickness of the film after coating is about 4mm.

As shown in FIG1 , the working process of the hydrogel-coated optical fiber misaligned splicing solution acidity detection device according to an embodiment of the present invention is as follows:

The sensing structure is placed in the detection liquid. When the signal light output by the broadband light source with a working band of 1500-1600nm is emitted through the introduction single-mode optical fiber 1 and the introduction coreless optical fiber 2, the light is separated into two parts and reaches the laterally offset single-mode optical fiber core 4 and the hydrogel-coated microcavity 7 respectively. After the light field signal interacts with the liquid medium in this area, it is coupled to the lead-out coreless optical fiber 5 and generates an interference spectrum output in the lead-out single-mode optical fiber 6.

Due to the pH sensitivity of the hydrogel film, different pH values correspond to different degrees of swelling and contraction of the hydrogel, resulting in the refractive index response of the hydrogel at different pH values, which causes the change of the light field transmission path in the misaligned structure, thereby causing the shift response of the transmitted light spectrum trough point to different solution pH values, as shown in Figure 3. Since there is a one-to-one correspondence between the different spectrum trough offset points and the pH value, the sensing detection of the pH value of the liquid to be tested can be achieved by monitoring the trough offset points of the transmitted light spectrum. Based on this structure, the solution pH detection with a maximum sensitivity of about 40nm/pH can be achieved.

Unless otherwise specified, the models of the components in the embodiments of the present invention are not limited, and any device that can perform the above functions may be used.

Those skilled in the art will appreciate that the accompanying drawing is only a schematic diagram of a preferred embodiment, and the serial numbers of the embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (4)

1. A detection device based on the acidity of a hydrogel-coated optical fiber misaligned splicing solution, characterized in that the device adopts a hydrogel-coated optical fiber misaligned splicing structure, The optical fiber dislocation splicing structure is as follows: a section of single-mode optical fiber is laterally offset and embedded into the joint of the coreless optical fiber; a hydrogel is dip-coated on the surface of the silanized dislocation splicing structure fiber to obtain a liquid pH sensing device stably adsorbed by the hydrogel; The detection device comprises two major parts: a coreless optical fiber-single-mode optical fiber-coreless optical fiber dislocation fusion structure and a hydrogel coated on the surface of the silanized fiber. 2. A detection device for the acidity of a solution of a hydrogel-coated optical fiber misaligned splicing according to claim 1, characterized in that the detection device is placed in the detection liquid, and when the signal light output by a broadband light source with a working band of 1500-1600nm is emitted through the introduction of a single-mode optical fiber and an introduction of a coreless optical fiber, the light is separated into two parts, reaching the laterally offset single-mode optical fiber core and the hydrogel-coated microcavity area respectively, and after the light field signal interacts with the liquid medium in this area, it is coupled to the lead-out coreless optical fiber and generates an interference spectrum output in the lead-out single-mode optical fiber. 3. A detection device for the acidity of a solution for dislocation splicing of hydrogel-coated optical fibers according to claim 1, characterized in that the ratio and implementation process of the hydrogel are as follows: A 30% solution of acrylamide AAm polymerization monomer and methylene bisacrylamide BAAM crosslinker was prepared in a ratio of 29:1, and 5.5 mL of deionized water and 1.2 mL of AAm/BAAM mixed solution were mixed evenly. Take 0.1 mL of methacrylic acid liquid and add it to the liquid mixed in the previous step, then add 0.1 mL of N,N,N',N'-tetraethylethylenediamine TEMED and mix well; take 0.25 mL of 5% ammonium persulfate APS aqueous solution and add it to the above mixed liquid and stir well; pour the mixed liquid into a sealed bottle, expel the air in the bottle and seal it; The polymerization reaction is completely completed under the condition of 20 hours of light exposure, and the polymerized hydrogel is rinsed in deionized water to obtain a non-toxic, odorless and transparent hydrogel. 4. A device for detecting the acidity of a solution for dislocated splicing of hydrogel-coated optical fibers according to claim 1, characterized in that the ratio and implementation process of the silanization are as follows: Mix anhydrous ethanol and deionized water in equal volumes at a ratio of 1:1, add an appropriate amount of glacial acetic acid to adjust the pH of the ethanol solution to 3.5, and add a certain amount of silane coupling agent KH-570 to the above solution to prepare a mixed solution of 3%-4% KH-570 by volume; The configured solution was mechanically stirred for 2 hours, and the optical fiber hydrogel-coated section was immersed in the solution for 10 minutes to achieve silanization. The optical fiber structure was then taken out and the surface of the structure was properly cleaned with a mixture of equal volumes of deionized water and ethanol. The cleaned optical fiber structure was dried and placed for 1 hour to complete the silanization.