Optical fiber-capillary optical microfluidic sensor and method of manufacture and use

Abstract

The application discloses a kind of optical fiber-capillary optical microfluid sensor and manufacturing method and application, sensor includes quartz optical fiber and quartz capillary, wherein quartz optical fiber and quartz capillary are integrally drawn under parallel synchronous high-temperature hot melting condition, sensor whole structure is dumbbell type, the outer diameter of two end portions of sensor is greater than the outer diameter of the middle part of sensor, symmetric taper is formed between the middle part of sensor and the end of sensor;Sensor manufacturing method is: step 1, coating layer outside cladding is cleaned up;Step 2, it is fixed on the taper platform using clamp;Step 3, then draw until stretched to the designed size, close the drawing platform, close the flame;Step 4, optical fiber-capillary optical microfluid sensor is formed.Optical microfluid sensor can be applied in optical fiber-capillary optical microfluid detection system.Advantage: relatively simple structure, easy to realize in industry, manufacturing difficulty is small.

Description

Technical Field

[0001] This invention relates to an optical fiber sensor, its manufacturing method, and its application, and particularly to an optical fiber-capillary optical microfluidic sensor, its manufacturing method, and its application. Background Technology

[0002] Currently, fiber optic sensors are categorized into various types based on their functions, structures, and principles. Optical microfluidics sensors are a key research area in recent years. Optical microfluidics is an emerging field that organically combines optical and microfluidic systems, developing towards multifunctionality and miniaturization. More precisely, optical microfluidics provides an efficient fluid-fluid integration method by incorporating fluid as part of the optical waveguide. The fluid modulates the optical signal, enabling microfluidic systems to achieve high levels of structural compactness and reconfigurability. Optical microfluidics technology manipulates light and fluid at the micrometer or submicrometer scale, realizing the interaction between light and fluid, and integrating fluid and solid materials into an optical system—a perfect combination of microfluidics and optics.

[0003] Optical microfluidic sensors, by integrating optical units and microfluidic systems into one unit, retain the high sensitivity of optical sensors while combining the low sample consumption of microfluidic systems. Compared to conventional optical sensors, they are more compact and practical, providing a novel solution for chip-scale integration of microfluidic systems and functionalized optical structures. Aligning with the current trends in precision medicine and device miniaturization, optical microfluidic sensors have broad application prospects in biomedical detection, pharmaceutical research, and environmental monitoring, particularly showing great potential in tumor marker detection.

[0004] The key to optical microfluidic sensor systems is achieving the interaction between light and matter. This can be achieved in two ways: one is that the microfluidic itself is the main light transmission channel, interacting with the microfluidic through the whole optical field; the other is to effectively combine the microfluidic with the optical path, achieving the interaction between the evanescent field and the microfluidic. Based on these two modes of interaction, optical microfluidic sensors can be divided into two categories: liquid-core optical microfluidic sensors and evanescent field optical microfluidic sensors. While liquid-core optical microfluidic sensors maximize the interaction between light and matter, they are more difficult to manufacture and have relatively higher losses. Evanescent field optical microfluidic sensors can be mainly divided into three categories: micro / nano fiber optic optical microfluidic sensors, SPR (Sequential Reflection) optical microfluidic sensors, and resonant optical microfluidic sensors. The principle of micro / nano fiber optic optical microfluidic sensors is that light undergoes total internal reflection in a waveguide, allowing it to propagate along the waveguide. During total internal reflection, a portion of the evanescent field penetrates into the cladding, and the external fluid or matter modulates the light. Since this effect is very weak in an untreated waveguide, in order to achieve or enhance this effect, the original optical fiber needs to be thinned so that the light distribution penetrates the cladding and interacts with the external material, thus modulating the light. Summary of the Invention

[0005] The purpose of this invention is to inject the substance to be measured into a quartz capillary. When the light in the single-mode optical fiber passes through the corresponding region, it will couple into the quartz capillary and generate interference. The substance in the quartz capillary will change the phase characteristics of the light and change the interference conditions, thereby enabling the sensing of the liquid composition in the capillary through interference. This invention provides an optical fiber-capillary optical microfluidic sensor, its manufacturing method, and its application.

[0006] The fiber-capillary microfluidic sensor provided by this invention includes a quartz fiber and a quartz capillary. The quartz fiber and quartz capillary are integrally drawn under parallel synchronous high-temperature thermal fusion conditions. The overall structure of the sensor is dumbbell-shaped, with the outer diameter of the two ends of the sensor being larger than the outer diameter of the middle part of the sensor. A symmetrical cone shape is formed between the middle part of the sensor and the ends of the sensor. An optical path is provided inside the quartz fiber, and a microfluidic channel is provided inside the quartz capillary. When the light transmitted by the optical path in the quartz fiber is transmitted to the gradually tapering region and the uniform middle part, it is coupled into the microfluidic channel in the quartz capillary. The light transmitted by the optical path in the quartz fiber interacts with the material in the microfluidic channel in the quartz capillary, and the sensing of the material in the microfluidic channel in the quartz capillary is achieved through the interference of the coupled optical field.

[0007] The lengths of the quartz optical fiber and the quartz capillary are equal, and the outer diameter deviation between the quartz optical fiber and the quartz capillary does not exceed ±25% of the diameter of the quartz optical fiber.

[0008] Quartz optical fiber can be single-mode or multimode, and its diameter ranges from 50 to 500 micrometers.

[0009] Quartz capillaries have a single or multiple inner holes. The inner hole of the quartz capillary may be coaxial with or non-coaxial with the outer contour of the quartz capillary. The inner hole diameter d of the quartz capillary is smaller than the outer diameter D of the quartz capillary, and the inner hole diameter d > 0.2 micrometers.

[0010] The method for manufacturing an optical fiber-capillary optical microfluidic sensor provided by the present invention includes the following steps:

[0011] Step 1: Remove the coatings from the quartz optical fiber and quartz capillary respectively, and clean up any coating debris outside the cladding.

[0012] Step 2: Align the quartz optical fiber and quartz capillary tube, place them parallel and tightly together, and fix them on the tapered platform using a clamp.

[0013] Step 3: Turn on the hydrogen flame. The flame temperature needs to reach 1600-2000℃. Preheat for 1-2 minutes, then stretch until the desired size is reached. After that, turn off the stretching platform and the flame.

[0014] Step 4: Remove the drawn sensor from the platform. Since the sensor is brittle and easily damaged, it is encapsulated in a chip for storage, thus forming an optical fiber-capillary microfluidic sensor.

[0015] The fiber-capillary optical microfluidic sensor provided by this invention can be applied in fiber-capillary optical microfluidic detection systems.

[0016] The fiber-capillary microfluidic detection system includes a light source, a syringe pump, a spectrometer, a liquid storage container, a polarization controller, a polarizing mirror, and a sensor. The light source, sensor, polarization controller, polarizing mirror, and spectrometer are connected in sequence to form an optical path, while the syringe pump, sensor, and liquid storage container are connected in sequence to form a microfluidic channel. Both the optical path and the microfluidic channel pass through the sensor, and the light passing through the optical path can couple with the substance flowing in the microfluidic channel within the sensor.

[0017] The light source, syringe pump, spectrometer, liquid storage container, polarization controller and polarizing mirror mentioned above are all assemblies of existing equipment, therefore, the specific models and specifications are not described in detail.

[0018] Working principle of the invention:

[0019] The fiber-capillary microfluidic sensor provided by this invention involves injecting the liquid to be measured into a quartz capillary and connecting one end of the quartz fiber to a light source. When the 1550nm light source passes through a gradually tapered region and the middle section at the end of the sensor, the light from the quartz fiber couples into the quartz capillary in these two regions and interacts with the substance being measured. Part of the light propagates along the quartz capillary, while the other part is recoupled back into the quartz fiber, propagates along the fiber, and finally enters other optical elements. The interference light is then analyzed to study its phase characteristics. Finally, based on the change in the light phase and by changing the interference conditions, the sensor can achieve the sensing of the substance being measured in the quartz capillary through interference.

[0020] like Figure 5 The figure shows the mode field distribution of the fiber-capillary optical microfluidic sensor. The diameters of both the quartz fiber and the quartz capillary are 3.1 μm, which is the mode field distribution located at the dispersion inflection point of the sensor. Figure 5 (a) and (b) are the odd-mode and even-mode diagrams polarized along the x-direction, respectively. A clear difference in the mode field distribution between the odd-mode and even-mode modes can be observed. The curves in the diagram represent the contour lines of the mode field energy; the denser the contour lines, the higher the energy. It can be seen that the energy of the odd-mode diffuses towards the quartz capillary, while the energy of the even-mode is mostly concentrated in the single-mode fiber. This indicates that the odd-mode plays a dominant role in the sensor.

[0021] A quartz optical fiber and a quartz capillary tube are placed parallel to each other and fixed together. After being drawn at high temperature, they are stored in a chip to create a sensor. A light source, sensor, polarization controller, polarizer, and spectrometer are sequentially connected to form an optical path. A syringe pump, sensor, and reservoir are sequentially connected to form a microfluidic channel. Both the optical path and the microfluidic channel pass through the sensor, allowing light passing through the optical path to couple with the material flowing within the microfluidic channel. The light output from the light source passes through the sensor, where it is adjusted by the polarization controller and polarizer before being input to the spectrometer. The syringe pump injects the analyte into the sensor, which then flows out and is stored in the reservoir. Samples with different refractive indices are added to the syringe pump and injected into the sensor. Changes in the refractive index of the internal environment are detected based on the spectral changes observed by the spectrometer.

[0022] The sensor's sensitivity to the refractive index of the analyte in the liquid was tested. Five solutions with different refractive indices (1.3263, 1.3264, 1.3265, 1.3266, and 1.3267) were mixed and measured. Under constant conditions, a significant change in the spectrum was observed.

[0023] like Figure 4 The image shows the spectrum of the refractive index change of the internal test solution and the wavelength shift of the transmission tilt angle relative to the refractive index of the internal test solution provided by the fiber-capillary microfluidic sensor of the present invention (fiber diameter is 3.1 μm, coupling length is 6.5 mm, wavelength is 1550 nm). Figure 4 In (a), it can be observed that as the refractive index of the solution being tested increases, the interference peaks on both sides gradually approach the dispersion inflection point. As they approach, one peak gradually disappears, and the troughs on both sides closest to the dispersion inflection point gradually merge into a large trough. Figure 4 (b) Describing the relationship between wavelength and the refractive index of the internal test solution at selected positions in the spectrum, two situations can be observed: at point a, the wavelength gradually decreases with increasing refractive index of the internal test solution; at the other four points, the wavelength gradually increases with increasing refractive index of the internal test solution, with point b showing a significant increase and the other three points showing a slower increase. This demonstrates that different refractive indices of the internal test solution result in different spectra. The spectrum continuously changes depending on the internal test solution.

[0024] The beneficial effects of this invention are:

[0025] The sensor provided by this invention integrates a quartz optical fiber and a quartz capillary tube into a single, parallel structure for sensing the analyte within the quartz capillary. This structure is relatively simple, easily implemented industrially, and easy to manufacture. The quartz capillary provides a relatively independent microfluidic channel, reducing sample contamination and minimizing sample consumption. Experiments show that this structure requires minimal manufacturing processes, ensuring consistent sensor characteristics. The sensor has three dispersion inflection points where the refractive index sensitivity approaches infinity, allowing for further improvement of sensor characteristics. The fiber-capillary optical microfluidic sensor is manufactured using a simultaneous fusion taper technique involving the quartz optical fiber and quartz capillary tube. This manufacturing method is highly commercialized, technologically advanced, and cost-effective. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall structure of the fiber-capillary optical microfluidic sensor described in this invention.

[0027] Figure 2 This is a schematic diagram of the cross-sectional structure of the fiber-capillary optical microfluidic sensor described in this invention.

[0028] Figure 3 This is a schematic diagram of the fiber-capillary optical microfluidic detection system described in this invention.

[0029] Figure 4 This is a schematic diagram of the spectrum of the refractive index change of the liquid being detected according to the present invention.

[0030] Figure 5 This is a mode field distribution diagram of the fiber-capillary optical microfluidic sensor described in this invention.

[0031] The annotations in the image above are as follows:

[0032] 1. Sensor 2. Quartz optical fiber 3. Quartz capillary 4. Optical path 5. Microfluidic channel

[0033] 6. Light source 7. Syringe pump 8. Spectrometer 9. Liquid storage container 10. Polarization controller

[0034] 11. Polarizing mirror. Detailed Implementation

[0035] Please see Figures 1 to 5 As shown:

[0036] The fiber-capillary microfluidic sensor provided by this invention includes a quartz fiber 2 and a quartz capillary 3, wherein the quartz fiber 2 and the quartz capillary 3 are integrally drawn under parallel synchronous high-temperature thermal fusion conditions. The overall structure of the sensor 1 is dumbbell-shaped, and the outer diameter of the two ends of the sensor 1 is larger than the outer diameter of the middle part of the sensor 1. A symmetrical cone is formed between the middle part of the sensor 1 and the ends of the sensor 1. An optical path 4 is provided in the quartz fiber 2, and a microfluidic channel 5 is provided in the quartz capillary 3. When the light transmitted by the optical path 4 in the quartz fiber 2 is transmitted to the gradually tapering region and the uniform middle part, it will couple into the microfluidic channel 5 in the quartz capillary 3. The light transmitted by the optical path 4 in the quartz fiber 2 interacts with the material in the microfluidic channel 5 in the quartz capillary 3, and the sensing of the material in the microfluidic channel 5 in the quartz capillary 3 is achieved through the interference of the coupled optical field.

[0037] The lengths of the quartz optical fiber 2 and the quartz capillary tube 3 are equal, and the outer diameter deviation between the quartz optical fiber 2 and the quartz capillary tube 3 does not exceed ±25% of the diameter of the quartz optical fiber 2.

[0038] Quartz fiber 2 is a single-mode or multimode fiber, and its diameter is 50-500 micrometers.

[0039] The quartz capillary 3 has a single or several inner holes. The inner hole of the quartz capillary 3 is coaxial with or non-coaxial with the outer contour of the quartz capillary 3. The inner hole diameter d of the quartz capillary 3 is smaller than the outer diameter D of the quartz capillary 3, and the inner hole diameter d of the quartz capillary 3 is greater than 0.2 micrometers.

[0040] The method for manufacturing an optical fiber-capillary optical microfluidic sensor provided by the present invention includes the following steps:

[0041] Step 1: Remove the coatings from the quartz optical fiber 2 and the quartz capillary tube 3 respectively, and clean up the coating debris outside the cladding.

[0042] Step 2: Align the quartz optical fiber 2 and the quartz capillary tube 3, place them parallel and tightly together, and fix them on the tapered platform using a clamp.

[0043] Step 3: Turn on the hydrogen flame. The flame temperature needs to reach 1600-2000℃. Preheat for 1-2 minutes, then stretch until the desired size is reached. After that, turn off the stretching platform and the flame.

[0044] Step 4: Remove the drawn sensor 1 from the platform. Since sensor 1 is relatively brittle and easily damaged, it is encapsulated in a chip for storage, thus forming an optical fiber-capillary microfluidic sensor.

[0045] The fiber-capillary optical microfluidic sensor provided by this invention can be applied in fiber-capillary optical microfluidic detection systems.

[0046] The fiber-capillary microfluidic detection system includes a light source 6, a syringe pump 7, a spectrometer 8, a liquid storage container 9, a polarization controller 10, a polarizing mirror 11, and a sensor 1. The light source 6, sensor 1, polarization controller 10, polarizing mirror 11, and spectrometer 8 are connected in sequence to form an optical path 4. The syringe pump 7, sensor 1, and liquid storage container 9 are connected in sequence to form a microfluidic channel 5. Both the optical path 4 and the microfluidic channel 5 pass through the sensor 1. The light passing through the optical path 4 can couple with the substance flowing in the microfluidic channel 5 within the sensor 1.

[0047] The light source 6, syringe pump 7, spectrometer 8, liquid storage container 9, polarization controller 10 and polarizing mirror 11 mentioned above are all assemblies of existing equipment, therefore, their specific models and specifications are not described in detail.

[0048] Working principle of the invention:

[0049] The fiber-capillary microfluidic sensor provided by this invention injects the liquid to be measured into a quartz capillary 3 and connects one end of the quartz fiber 2 to a light source. When the 1550nm light source passes through the gradually tapered region and the middle part of the sensor 1, the light in the quartz fiber 2 is coupled into the quartz capillary 3 in these two regions and interacts with the substance being measured in the quartz capillary 3. Part of the light propagates along the quartz capillary 3, and the other part of the light is recoupled back into the quartz fiber 2, propagates along the quartz fiber 2, and finally enters other optical elements. Then, the light that has passed through the interference is analyzed to study the phase characteristics of the light. Finally, based on the change of the light phase and the change of the interference conditions, the sensing of the substance being measured in the quartz capillary 3 is achieved through interference.

[0050] like Figure 5The figure shows the mode field distribution of the fiber-capillary optical microfluidic sensor. The diameters of both the quartz fiber 2 and the quartz capillary 3 are 3.1 μm, which corresponds to the mode field distribution at the dispersion inflection point of sensor 1. Figure 5 (a) and (b) are the odd-mode and even-mode diagrams polarized along the x-direction, respectively. A clear difference in the mode field distribution between the odd-mode and even-mode modes can be observed. The curves in the figure represent the contour lines of the mode field energy; the denser the contour lines, the higher the energy. It can be seen that the energy of the odd-mode diffuses towards the direction of the quartz capillary 3, while the energy of the even-mode is mostly concentrated in the single-mode fiber. This indicates that the odd-mode plays a dominant role in sensor 1.

[0051] A quartz optical fiber 2 and a quartz capillary tube 3 are placed parallel to each other and fixed together. After being drawn at high temperature, they are stored in a chip to form sensor 1. A light source 6, sensor 1, polarization controller 10, polarizer 11, and spectrometer 8 are sequentially connected to form an optical path 4. A syringe pump 7, sensor 1, and liquid storage container 9 are sequentially connected to form a microfluidic channel 5. Both optical path 4 and microfluidic channel 5 pass through sensor 1, and the light passing through optical path 4 can couple with the substance flowing in microfluidic channel 5 within sensor 1. The light output from the light source passes through sensor 1, and after being adjusted by polarization controller 10 and polarizer 11, it is finally input into spectrometer 8. The syringe pump 7 injects the analyte into sensor 1, and then flows out of sensor 1 and is stored in liquid storage container 9. Samples with different refractive indices are added to syringe pump 7 and injected into sensor 1. The changes in the refractive index of the internal environment are detected based on the spectral changes of spectrometer 8.

[0052] Sensor 1 was used to detect the refractive index sensitivity of the analyte in the liquid. Five different refractive indices (1.3263, 1.3264, 1.3265, 1.3266, and 1.3267) were measured by mixing different proportions of the analyte solution. During the measurement, with all other conditions unchanged, a significant change in the spectrum was observed.

[0053] like Figure 4 The image shows the spectrum of the refractive index change of the internal test solution and the wavelength shift of the transmission tilt angle relative to the refractive index of the internal test solution provided by the fiber-capillary microfluidic sensor of the present invention (fiber diameter is 3.1 μm, coupling length is 6.5 mm, wavelength is 1550 nm). Figure 4 In (a), it can be observed that as the refractive index of the solution being tested increases, the interference peaks on both sides gradually approach the dispersion inflection point. As they approach, one peak gradually disappears, and the troughs on both sides closest to the dispersion inflection point gradually merge into a large trough. Figure 4(b) Describing the relationship between wavelength and the refractive index of the internal test solution at selected positions in the spectrum, two situations can be observed: at point a, the wavelength gradually decreases with increasing refractive index of the internal test solution; at the other four points, the wavelength gradually increases with increasing refractive index of the internal test solution, with point b showing a significant increase and the other three points showing a slower increase. This demonstrates that different refractive indices of the internal test solution result in different spectra. The spectrum continuously changes depending on the internal test solution.

Claims

1. A fiber-optic-capillary optical microfluidic sensor, characterized in that: The sensor comprises a quartz optical fiber and a quartz capillary tube, which are integrally drawn under parallel and synchronous high-temperature thermal fusion conditions. The overall sensor structure is dumbbell-shaped, with the outer diameter of the two ends of the sensor being larger than the outer diameter of the middle part. A symmetrical cone shape is formed between the middle part and the ends of the sensor. An optical path is set inside the quartz optical fiber, and a microfluidic channel is set inside the quartz capillary tube. When the light transmitted through the optical path in the quartz optical fiber reaches the gradually tapering region and the uniform middle part, it couples into the microfluidic channel in the quartz capillary tube. The interaction of substances within the microfluidic channel enables sensing of the substances within the microfluidic channel in the quartz capillary through interference of coupled optical fields. The quartz optical fiber and the quartz capillary are of equal length, and the outer diameter deviation between the two does not exceed ±25% of the diameter of the quartz optical fiber. The light transmitted in the quartz optical fiber is coupled into the inner hole of the quartz capillary in the waist region of the sensor, and propagates using the measured liquid in the inner hole of the quartz capillary as the main transmission medium, forming a liquid core waveguide structure. After interacting with the measured liquid, the light is recoupled back into the quartz optical fiber.

2. The fiber-optic-capillary optical microfluidic sensor according to claim 1, characterized in that: The quartz optical fiber is a single-mode or multimode optical fiber, and the diameter of the quartz optical fiber is 50-500 micrometers.

3. The fiber-optic-capillary optical microfluidic sensor according to claim 1, characterized in that: The quartz capillary has a single inner hole or several inner holes, and the inner hole of the quartz capillary is coaxial or non-coaxial with the outer contour of the quartz capillary; the inner hole diameter d of the quartz capillary is smaller than the outer diameter D of the quartz capillary, and the inner hole diameter d of the quartz capillary is greater than 0.2 micrometers.

4. A method for manufacturing an optical fiber-capillary optical microfluidic sensor, employing the optical fiber-capillary optical microfluidic sensor as described in any one of claims 1 to 3, characterized in that: The method includes the following steps: Step 1: Remove the coatings from the quartz optical fiber and quartz capillary respectively, and clean up any coating debris outside the cladding. Step 2: Align the quartz optical fiber and quartz capillary tube, place them parallel and tightly together, and fix them on the tapered platform using a clamp. Step 3: Turn on the hydrogen flame. The flame temperature needs to reach 1600-2000℃. Preheat for 1-2 minutes, then stretch until the desired size is reached. After that, turn off the stretching platform and the flame. Step 4: Remove the drawn sensor from the platform. Since the sensor is brittle and easily damaged, it is encapsulated in a chip for storage, thus forming an optical fiber-capillary microfluidic sensor.

5. The method for manufacturing an optical fiber-capillary optical microfluidic sensor according to claim 4, characterized in that: The fiber-capillary microfluidic detection system includes a light source, a syringe pump, a spectrometer, a liquid storage container, a polarization controller, a polarizing mirror, and a sensor. The light source, sensor, polarization controller, polarizing mirror, and spectrometer are connected in sequence to form an optical path, and the syringe pump, sensor, and liquid storage container are connected in sequence to form a microfluidic channel. Both the optical path and the microfluidic channel pass through the sensor, and the light passing through the optical path can couple with the substance flowing in the microfluidic channel within the sensor.

Images