Microbubble lens sensor chip for liquid concentration detection, preparation method and detection system

Abstract

The present invention belongs to the field of optical sensor technology, specifically a microbubble lens sensor chip for liquid concentration detection, a preparation method, and a detection system. The sensor chip of the present invention includes a quartz capillary tube with microbubbles in the middle, a single-mode optical fiber, a sensor packaging bracket, and a cover glass; the microbubble is a hollow structure; the end face of the single-mode optical fiber is flat, the optical fiber core is vertically aligned with the center of the microbubble, and the distance between the optical fiber end face and the microbubble is the focal length of the microbubble lens; the sensor packaging bracket is used to fix the capillary quartz tube and the single-mode optical fiber; the cover glass covers the packaging bracket. The present invention is based on the lens effect of microbubbles to achieve collimation of the output light spot of the single-mode optical fiber. When the concentration of the solution inside the microbubble is changed, the focal length of the microbubble lens changes. By measuring the size of the collimated light spot output by it, the concentration of the solution inside the microbubble can be determined; the sensor chip has a simple structure, is easy to prepare, and has a high reuse rate. It also includes a liquid concentration detection system based on the sensor chip.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical sensors, and in particular relates to a microbubble lens sensor chip for liquid concentration detection, a preparation method thereof, and a liquid concentration detection system. Background Art

[0002] Common liquid concentration detection technologies include liquid chromatography, absorption spectroscopy, fiber optic interferometers, and optical microcavity sensors. Although optically based sensing technologies have advantages such as rapid real-time detection, non-destructiveness, and strong resistance to electromagnetic interference, most of the above technologies still require complex detection systems or instruments. For example, fiber optic interferometers require tunable lasers or broadband coherent light sources, and absorption spectroscopy requires not only a spectrum analyzer but also a laser with stable output light intensity. As a result, various existing liquid concentration detection instruments are bulky and expensive.

[0003] Microlenses are currently widely used in technologies such as beam shaping, imaging, beam shrinkage and expansion, and optical tweezers. However, there are few reports on technologies for detecting liquid concentration by monitoring the size of the microlens output light spot. Tunable focal length microlenses are susceptible to changes in focusing performance due to the lens size or the contrast between the lens and the ambient refractive index. Based on this principle, monitoring the size of the output light spot can be used to detect physical parameters such as the ambient refractive index or the lens's own refractive index. In most cases, the refractive index is linearly related to the liquid concentration. Therefore, by monitoring the size of the lens output light spot in real time, liquid concentration can be measured. This not only overcomes the need for complex light sources and detectors, but also significantly reduces the size of the sensor. Summary of the Invention

[0004] The purpose of the present invention is to provide a microbubble lens sensor chip and its preparation method that can achieve low-cost, portable and real-time monitoring of liquid concentration. In addition, a real-time detection system for liquid concentration (such as alcohol concentration and sugar concentration) based on the microbubble lens sensor chip is also provided.

[0005] The microbubble lens sensor chip provided by the present invention for detecting liquid concentration (such as alcohol concentration, sugar concentration) has a structure as follows: Figure 1 (i) shown; comprising: a quartz capillary 1 with microbubbles 6 prepared in the middle portion, a single-mode optical fiber 2, a sensor packaging bracket 3 and a cover glass 5; wherein:

[0006] The microbubbles 6 are hollow structures. When the microbubbles are filled with liquid, they form spherical lenses.

[0007] The end face of the single-mode optical fiber 2 is flat; one end of the single-mode optical fiber is connected to an external laser for introducing light into the single-mode optical fiber, and the other end outputs the light and irradiates the surface of the microbubble 6;

[0008] The core of the single-mode optical fiber 2 is vertically aligned with the center of the quartz microbubble spherical lens, and the distance between the output end face of the single-mode optical fiber 2 and the quartz microbubble lens is the focal length of the microbubble lens;

[0009] The microbubble 6 is placed perpendicular to the single-mode optical fiber 2, and the center of the microbubble 6 coincides with the core of the single-mode optical fiber 2. The light output by the single-mode optical fiber 2 is collimated parallel light after passing through the microbubble lens;

[0010] The sensor packaging bracket 3 is made of glass splicing or 3D printing, and is used to fix the quartz capillary 1 with microbubbles 6 in the middle and the single-mode optical fiber 2 to ensure that the relative positions of the two are not offset;

[0011] The cover glass 5 covers the sensor packaging bracket 3 to protect the relative positions of the sensor core component quartz microbubble 6 and the single-mode optical fiber 2 from being disturbed;

[0012] The quartz capillary 1 (ie, on the left and right sides of the microbubble 6) is open at both ends, one end is connected to an external microfluidic system through a Teflon tube, and the other end is connected to the analyte to be measured through a Teflon tube.

[0013] In the present invention, the diameter of the quartz capillary 1 is 50-1000 μm.

[0014] In the present invention, the diameter of the quartz microbubbles 6 is 100-2000 μm, the wall thickness is 5-15 μm, and the shape of the microbubbles is spherical.

[0015] In the present invention, the material of the quartz capillary 1 is preferably silicon dioxide.

[0016] In the present invention, the core diameter of the single-mode optical fiber 2 is 4-10 μm; the optical wavelength transmission range of the single-mode optical fiber 2 is visible light of 380-780 nm.

[0017] In the present invention, the diameter of the light spot outputted from the core of the single-mode optical fiber 2 is a Gaussian light spot of 4-10 μm, which can be regarded as an ideal point light source relative to the quartz microbubble lens.

[0018] In the present invention, the sensor packaging bracket fixes the single-mode optical fiber 2 through a raised platform and fixes the quartz microbubble 6 through a glass groove.

[0019] In the present invention, the quartz microbubble 6 and the single-mode optical fiber are fixed to the sensor packaging bracket 3 through UV glue 4; the capillary quartz tubes on both sides of the quartz microbubble are fixed in the glass groove on the sensor packaging support frame 3 through UV glue; the end face of the single-mode optical fiber 2 is suspended in the air with a length of 2-10 mm, and the remaining parts are fixed to the glass boss of the sensor packaging support frame 3 through UV glue.

[0020] In the present invention, the sensor packaging bracket is covered with a transparent cover glass 5 to protect the relative positions of the sensor core components, the quartz microbubbles and the single-mode optical fiber, from being disturbed.

[0021] In the present invention, when the liquid concentration inside the quartz microbubble 6 is different, the effective refractive index of the quartz microbubble lens changes, resulting in a change in the focusing performance of the microbubble, and the collimation effect of the light output from the end face 11 of the single-mode optical fiber after passing through the quartz microbubble lens changes, such as Figure 1 (ii) as shown; wherein:

[0022] When the liquid concentration inside the microbubble lens is low, the microbubble focal length is long, the numerical aperture is small, the ability to collect incident light is weak, and the number of light spot pixels detected by the detection end face 12 of the CCD imaging device 16 is small;

[0023] When the liquid concentration inside the microbubble lens is a high concentration of 10, the microbubble focal length is short, the numerical aperture is large, the incident light collection capability is strong, and the number of light spot pixels detected by the detection end face 12 of the CCD imaging device 16 is large.

[0024] Here, high and low concentrations, long and short focal lengths, large and small apertures, and large and small number of light spot pixels are all relative.

[0025] The microbubble lens sensor chip provided by this invention can be used to detect liquid concentrations (such as alcohol and sugar concentrations). During detection, based on the refraction effect of light on the target object at different concentrations, combined with the CCD imaging device to measure the size of the collimated light spot, it can achieve real-time, rapid, and quantitative detection of liquid concentration based on optical means.

[0026] The present invention also provides a method for preparing the microbubble lens sensor chip, such as Figure 2 As shown, the specific steps are:

[0027] (1) Select a section of capillary quartz microtube and prepare spherical microbubbles on it by melt blowing, wherein the number of microbubbles is 1;

[0028] (2) Assembling the sensor package bracket 3 with a glass sheet or using 3D printing technology;

[0029] (3) Clean the end face of the single-mode optical fiber and cut it flat with a fiber cleaver. Then fix it horizontally on the boss of the sensor packaging bracket with UV glue, ensuring that the end face of the single-mode optical fiber is suspended in the air for 2-10 mm.

[0030] (4) Use a five-dimensional adjustment frame to adjust the pitch angle of the quartz microbubble to ensure that the microbubble (axis) is placed perpendicular to the single-mode optical fiber. Then adjust the position of the microbubble along the plane perpendicular to the optical axis to ensure that the center of the microbubble coincides with the core of the single-mode optical fiber. Finally, adjust the position of the microbubble along the optical axis to ensure that the light output from the single-mode optical fiber is collimated parallel light after passing through the microbubble lens.

[0031] (5) Using UV glue, fix the capillary quartz tubes at both ends of the quartz microbubble lens into the grooves of the sensor packaging bracket;

[0032] (6) Covering the surface of the sensor package bracket with a cover glass to protect the relative position of the microbubble lens and the single-mode optical fiber from being disturbed by environmental disturbances;

[0033] (7) Teflon tubes are connected to both ends of the capillary quartz microtube to connect to the microfluidic system to extract the liquid to be tested.

[0034] The present invention uses the lens effect of microbubbles to collimate the output light spot of a single-mode optical fiber. Changing the concentration of the solution inside the microbubble changes the focal length of the microbubble lens. By measuring the size of the collimated light spot, the concentration of the solution inside the microbubble can be determined. The sensor chip measures liquid concentration by changing the focusing performance of the lens itself. The hollow structure of the microbubble also allows for sufficient interaction between light and matter, enabling the detection of trace amounts of liquid analytes. The sensor chip has a simple structure, is easy to prepare, and has a high reusability rate.

[0035] The present invention also provides an application of the microbubble lens sensor chip, which is used to construct a system for detecting liquid concentration (such as alcohol concentration, sugar concentration), see Figure 3 As shown, the detection system includes: a single-frequency laser 13, an optical fiber jumper 14, a microbubble lens sensor chip 15, a CCD imaging device 16, a computer 17, and a microfluidic system 18 connected in sequence; wherein:

[0036] The single-frequency laser 13 is used to emit a monochromatic detection laser;

[0037] The optical fiber jumper 14 is used to transmit the monochromatic laser output by the single-frequency laser to the single-mode optical fiber of the microbubble lens sensor chip 15, wherein the optical fiber jumper 14 and the single-mode optical fiber 2 are connected together through an optical fiber flange;

[0038] In the microbubble lens sensor chip 15, one end of the capillary quartz tube 1 is connected to the microfluidic system 18, and the other end is connected to the analyte to be measured through a Teflon tube; the divergent light output from the end face of the single-mode optical fiber 2 passes through the quartz microbubble lens 1 and is shaped into collimated parallel light and transmitted to the CCD imaging device 16 at the far end;

[0039] The CCD imaging device 16 receives the output optical signal and converts it into an electrical signal and transmits it to the computer 17;

[0040] The computer 17 is used to display the size of the light spot in real time and perform real-time processing and analysis on the light spot size or light spot pixels;

[0041] The microfluidic system 18 includes a syringe pump, a syringe, and a Teflon tube, which are used to extract the analyte to be tested into the quartz microbubble lens.

[0042] The detection process of the above-mentioned detection system is as follows: turn on the single-frequency laser to emit a monochromatic detection laser; use a microfluidic system (including a syringe pump, a syringe, and a Teflon tube) to extract the analyte to be tested into the microbubble. The process is as follows: one end of the microfluidic system is connected to one port of the quartz microbubble, and the other port of the quartz microbubble is connected to a test tube containing the analyte to be tested through the Teflon tube; a CCD imaging device is used to collect the collimated light spot output by the microbubble lens sensor chip and convert it into an electrical signal and transmit it to a computer; the computer is used to perform statistical analysis on the size or pixel points of the light spot, measure the concentration of multiple sets of standard analytes to be tested, and fit a calibration curve to complete the sensing performance calibration of the liquid concentration sensor.

[0043] The technical principle implemented by the present invention is as follows: quartz microbubbles are spherical hollow structures. Therefore, when the quartz microbubbles are filled with liquid, their effective refractive index is higher than that of air, which is equivalent to a spherical microlens. When the liquid concentration inside the quartz microbubbles is changed, the effective refractive index of the quartz microbubble lens changes, resulting in a change in the focusing performance of the microbubbles, and the collimation effect of the divergent light output from the end face of the single-mode optical fiber after passing through the lens also changes accordingly. Specifically, when the liquid concentration inside the microbubble lens is low, the microbubble focal length is long, the numerical aperture is small, the ability to collect incident light is weak, and the number of light spot pixels detected by the CCD imaging device is small. When the liquid concentration inside the microbubble lens is high, the microbubble focal length is short, the numerical aperture is large, the ability to collect incident light is strong, and the number of light spot pixels detected by the CCD imaging device is large. Therefore, the concentration of the liquid introduced into the quartz microbubble can be detected by detecting the number of collimated light spot pixels detected by the CCD imaging device.

[0044] The present invention has the following characteristics:

[0045] (1) The present invention is significantly different from conventional liquid sensors. The present invention uses a lens effect based on microbubbles to sense liquid concentration. This method does not require complex and expensive excitation light (such as a tunable laser) or detectors (spectrum analyzers). Instead, the liquid concentration can be detected by detecting the size of the collimated light spot, and the light source intensity stability requirement is low. Due to the hollow structure of the microbubbles themselves, the liquid concentration inside the microbubbles can be flexibly changed, while also achieving changes in the focusing performance of the quartz microbubbles.

[0046] (2) The present invention is significantly different from conventional microlenses; the quartz microbubble lens in the present invention is a hollow structure, while conventional microlenses are solid structures;

[0047] (3) The present invention is significantly different from conventional microlenses; the quartz microbubble lens in the present invention is a lens with tunable focusing performance, while most conventional microlenses have non-tunable focusing performance;

[0048] (4) The present invention is significantly different from conventional microlenses; the quartz microbubble lens of the present invention is prepared by heating and blowing on a capillary quartz tube, requiring only a fiber fusion splicer. The preparation method is simple, the surface roughness is low, and the process is superior to conventional microlens preparation processes.

[0049] (5) The microbubble lens provided by the present invention is itself a microlens with a microfluidic channel, which can simultaneously achieve the convergence of incident light and the transmission of liquid analytes;

[0050] (6) The microbubble lens sensor chip provided by the present invention integrates a microbubble lens and a single-mode optical fiber. The divergent light output by the single-mode optical fiber is collimated by the microbubble lens, thereby enabling remote measurement of the collimated light spot size.

[0051] (7) The center of the quartz microbubble in the microbubble lens sensor chip provided by the present invention is vertically aligned with the core of the single-mode optical fiber. The relative position of the two is the focal length of the microbubble lens, and both are fixed to the sensor packaging bracket by ultraviolet glue. The relative position is fixed and the robustness is strong;

[0052] (8) The sensor chip provided in the present invention has a simple structure, is easy to prepare, and has a high reuse rate;

[0053] (9) The sensor chip detection system provided in the present invention is easy to build and highly integrated, and the detection method is simple, low-cost, and convenient for practical application. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 (i) is a schematic diagram of the structure of the microbubble lens sensor chip of the present invention; Figure 1 (ii) is a schematic diagram of the principle of the microbubble lens sensor chip of the present invention.

[0055] Figure 2 It is a diagram showing the preparation process of the microbubble lens sensor chip of the present invention.

[0056] Figure 3 It is a diagram of the detection system of the microbubble lens sensor chip of the present invention.

[0057] Figure 4 1 is a diagram of the collimated light spot of the microbubble lens sensor chip of the present invention.

[0058] Figure 5 This is a diagram showing the relationship between the measured light spot pixel points of the microbubble lens sensor chip of the present invention and the change in alcohol concentration.

[0059] Figure 6 1 is a diagram showing the actual alcohol sample test results of the microbubble lens sensor chip of the present invention.

[0060] Numbers in the figure: 1 is a quartz capillary tube; 2 is a single-mode optical fiber; 3 is a sensor packaging bracket; 4 is a UV adhesive; 5 is a cover glass; 6 is a quartz microbubble; 7 is a hollow channel of a capillary quartz tube; 8 is a wall of a capillary quartz tube; 9 is a low-concentration liquid; 10 is a high-concentration liquid; 11 is a single-mode optical fiber end face; 12 is a detection end face of a CCD imaging device; 13 is a single-frequency laser; 14 is an optical fiber jumper; 15 is a microbubble lens sensor chip; 16 is a CCD imaging device; 17 is a computer; and 18 is a microfluidic system. DETAILED DESCRIPTION

[0061] The present invention will be further described in detail below with reference to the accompanying drawings and examples, but the present invention is not limited to these examples.

[0062] Example 1

[0063] In this embodiment, the microbubble lens sensor chip (see Figure 1 ), specifically including: a capillary quartz tube prepared with microbubbles, a single-mode optical fiber, a sensor packaging bracket and a cover glass; the microbubble is a hollow structure, and when the microbubble is filled with liquid, a spherical lens is formed; the end face of the single-mode optical fiber is flat, wherein one end of the single-mode optical fiber can be connected to a laser to guide light into the single-mode optical fiber, and the other end outputs the light and irradiates the surface of the microbubble; the sensor packaging bracket is prepared by glass splicing or 3D printing, and is used to fix the capillary quartz tube prepared with microbubbles and the single-mode optical fiber to ensure that the relative positions of the two will not shift; the cover glass is used to further protect the quartz microbubbles and the single-mode optical fiber from disturbances in the surrounding environment; the capillary quartz tube is open at both ends, one end can be connected to the microfluidic system through a Teflon tube, and the other end can be connected to the analyte to be measured through a Teflon tube; the diameter of the quartz microbubble is about 370μm, the wall thickness is 10μm, and the shape is spherical.

[0064] In this device, a preparation process of the microbubble lens sensor chip is provided (see Figure 2 ),include:

[0065] (1) Select a section of capillary quartz microtube and prepare spherical microbubbles on it by melt blowing, wherein the number of microbubbles is 1;

[0066] (2) Assembling the sensor package bracket using glass sheets or using 3D printing technology;

[0067] (3) Clean the end face of the single-mode optical fiber and cut it flat with a fiber cleaver. Then fix it horizontally on the boss of the sensor packaging bracket with UV glue, ensuring that the end face of the single-mode optical fiber is suspended in the air for 2-10 mm.

[0068] (4) Use a five-dimensional adjustment frame to adjust the pitch angle of the quartz microbubble to ensure that the microbubble is placed perpendicular to the single-mode optical fiber. Then adjust the position of the microbubble along the plane perpendicular to the optical axis to ensure that the center of the microbubble coincides with the core of the single-mode optical fiber. Finally, adjust the position of the microbubble along the optical axis to ensure that the light output from the single-mode optical fiber is collimated parallel light after passing through the microbubble lens.

[0069] (5) Using UV glue, fix the capillary quartz tubes at both ends of the quartz microbubble lens into the grooves of the sensor packaging bracket;

[0070] (6) Covering the surface of the sensor package bracket with a cover glass to protect the relative position of the microbubble lens and the single-mode optical fiber from being disturbed by environmental disturbances;

[0071] (7) Teflon tubes are connected to both ends of the capillary quartz microtube to connect to the microfluidic system to extract the liquid to be tested.

[0072] This device provides a detection method for a microbubble lens sensor chip. The single-frequency output laser is connected to the single-mode optical fiber of the microbubble lens sensor chip via an optical fiber flange. The relative position of the microbubble lens sensor chip and the CCD imaging device is adjusted to ensure that the light spot output by the microbubble lens is imaged at the center of the pixel unit of the CCD imaging device. The relative position of the two is then fixed. Deionized water is introduced into the quartz microbubble using a syringe and Teflon tube. The output light spot detected by the CCD imaging device is then displayed on a computer, as shown in the following example. Figure 4 shown.

[0073] Example 2

[0074] This embodiment also proposes a detection system for a microbubble lens sensor chip, such as Figure 3 As shown in the figure, a single-frequency laser is turned on to emit a monochromatic detection laser. A microfluidic system (including a syringe pump, syringe, and Teflon tubing) is used to extract the analyte to be tested into the microbubble. The process involves connecting one end of the microfluidic system to one port of the quartz microbubble, and the other port of the quartz microbubble is connected to a test tube containing the analyte to be tested via the Teflon tubing. A CCD imaging device collects the collimated light spot output by the microbubble lens sensor chip and converts it into an electrical signal, which is transmitted to a computer. The computer then performs statistical analysis on the size or pixel count of the light spot, measures the concentration of multiple sets of standard analytes to be tested, and fits a calibration curve to complete the sensing performance calibration of the liquid concentration sensor.

[0075] Based on the detection system of the microbubble lens sensor chip and combined with the structural parameters of Example 1, the standard alcohol solution concentration of the microbubble lens sensor chip was measured in this example. In the actual test, different concentrations of alcohol solutions were injected into the quartz microbubbles in sequence through a syringe, and the spot pixels collected by the CCD imaging device were calculated and analyzed simultaneously, and finally the following was obtained: Figure 5 The test results are shown in the black circles. The results show that as the alcohol concentration increases, the focusing performance of the microbubble lens is enhanced, and the collection or collimation effect of the incident light is further enhanced, and ultimately the number of light spot pixels detected on the CCD imaging device increases. Further fitting of the tested data points yields Figure 5 The calibration fitting curve is in medium gray. In subsequent practical applications, this calibration fitting curve is all that is needed to perform inverse measurements for different alcohol concentrations.

[0076] Based on the above alcohol concentration calibration curve, in this embodiment, any alcohol concentration was actually tested, such as Figure 6 As shown. Actual tests of any alcohol concentration were conducted using a standard alcohol concentration refractometer and the aforementioned microbubble lens sensor chip. The test results showed that the alcohol concentration detected by the microbubble lens sensor chip was close to that measured by the standard alcohol concentration refractometer, with a detection error of less than 0.2%, demonstrating that this method can accurately and real-timely detect alcohol samples of any concentration.

Claims

1. A microbubble lens sensor chip for liquid concentration detection, characterized in that: include: A quartz capillary (1) with microbubbles (6) prepared in the middle, a single-mode optical fiber (2), a sensor packaging bracket (3) and a cover glass (5); wherein: The microbubble (6) is a hollow structure, and when the microbubble is filled with liquid, a spherical lens is formed; The end face of the single-mode optical fiber (2) is flat; one end of the single-mode optical fiber is connected to an external laser to guide light into the single-mode optical fiber, and the other end outputs the light and irradiates the surface of the microbubble (6); The core of the single-mode optical fiber (2) is vertically aligned with the center of the quartz microbubble spherical lens, and the distance between the output end face of the single-mode optical fiber (2) and the quartz microbubble lens is the focal length of the microbubble lens; The microbubble (6) is placed perpendicular to the single-mode optical fiber (2), the center of the microbubble (6) coincides with the core of the single-mode optical fiber (2), and the light output by the single-mode optical fiber (2) is collimated parallel light after passing through the microbubble lens; The sensor packaging bracket (3) is made of glass splicing or prepared by 3D printing, and is used to fix the quartz capillary (1) with microbubbles (6) prepared in the middle and the single-mode optical fiber (2) to ensure that the relative positions of the two will not shift; The cover glass (5) covers the sensor packaging bracket (3) and is used to protect the relative positions of the sensor core component quartz microbubble (6) and the single-mode optical fiber (2) from being disturbed; The quartz capillary (1) is open at both ends, one end is connected to an external microfluidic system via a Teflon tube, and the other end is connected to an analyte to be measured via a Teflon tube; The core diameter of the single-mode optical fiber (2) is 4-10 μm; the optical wavelength transmission range is visible light of 380-780 nm; The light spot outputted from the core of the single-mode optical fiber (2) has a Gaussian light spot diameter of 4-10 μm, which is a point light source relative to the quartz microbubble lens; When the liquid concentration inside the quartz microbubble (6) is different, the effective refractive index of the quartz microbubble lens changes, resulting in a change in the focusing performance of the microbubble, and a change in the collimation effect of the light output from the end face (11) of the single-mode optical fiber after passing through the quartz microbubble lens; wherein: When the liquid concentration inside the microbubble lens is low (9), the microbubble focal length is long, the numerical aperture is small, the ability to collect incident light is weak, and the number of light spot pixels detected by the detection end face (12) of the CCD imaging device (16) is small; When the liquid concentration inside the microbubble lens is high (10), the microbubble focal length is short, the numerical aperture is large, the incident light collection capability is strong, and the number of light spot pixels detected by the detection end face (12) of the CCD imaging device (16) is large; Here, high and low concentrations, long and short focal lengths, large and small apertures, and large and small number of light spot pixels are all relative.

2. The microbubble lens sensor chip for liquid concentration detection according to claim 1, characterized in that: The diameter of the quartz capillary (1) with microbubbles (6) is 50-1000 μm; the diameter of the quartz microbubbles (6) is 100-2000 μm, the wall thickness is 5-15 μm, and the shape of the microbubbles is spherical.

3. The microbubble lens sensor chip for liquid concentration detection according to claim 1, characterized in that: The material of the quartz capillary (1) is silicon dioxide.

4. The microbubble lens sensor chip for liquid concentration detection according to claim 1, characterized in that: The sensor packaging bracket (3) fixes the single-mode optical fiber (2) via a boss and fixes the quartz microbubble (6) via a glass groove.

5. The microbubble lens sensor chip for liquid concentration detection according to claim 1, characterized in that: The quartz microbubble (6) and the single-mode optical fiber (2) are fixed to the sensor packaging bracket (3) by ultraviolet glue (4); the quartz capillaries (1) on both sides of the quartz microbubble (6) are fixed to the glass grooves on the sensor packaging bracket (3) by ultraviolet glue; the end face of the single-mode optical fiber (2) is suspended 2-10 mm, and the remaining part is fixed to the glass boss of the sensor packaging bracket (3) by ultraviolet glue.

6. A method for preparing a microbubble lens sensor chip for liquid concentration detection according to any one of claims 1 to 5, characterized in that: The specific steps are: (1) A section of capillary quartz microtube is selected and spherical microbubbles are prepared in the middle of the tube by melt blowing, wherein the number of microbubbles is one; (2) Assembling the sensor package bracket using glass sheets or 3D printing technology (3); (3) Clean the end face of the single-mode optical fiber and cut it flat with a fiber cleaver. Then fix it horizontally on the boss of the sensor package bracket with UV glue, ensuring that the end face of the single-mode optical fiber is suspended in the air for 2-10 mm. (4) Use the five-dimensional adjustment frame to adjust the pitch angle of the quartz microbubble to ensure that the microbubble is placed vertically with the single-mode optical fiber. Then adjust the position of the microbubble along the plane perpendicular to the optical axis to ensure that the center of the microbubble coincides with the core of the single-mode optical fiber. Finally, adjust the position of the microbubble along the optical axis to ensure that the light output from the single-mode optical fiber is collimated parallel light after passing through the microbubble lens. (5) Use UV glue to fix the capillary quartz tubes at both ends of the quartz microbubble lens into the grooves of the sensor packaging bracket; (6) Covering the surface of the sensor package bracket with a cover glass to protect the relative position of the microbubble lens and the single-mode optical fiber from being disturbed by environmental disturbances; (7) Teflon tubes are connected to both ends of the capillary quartz microtube to connect to the microfluidic system to extract the liquid to be tested.

7. A system for detecting liquid concentration based on the microbubble lens sensor chip for detecting liquid concentration according to any one of claims 1 to 5, characterized in that: include: A single-frequency laser (13), an optical fiber jumper (14), a microbubble lens sensor chip (15), a CCD imaging device (16), a computer (17), and a microfluidic system (18) are connected in sequence; wherein: The single-frequency laser (13) is used to emit monochromatic detection laser; The optical fiber jumper (14) is used to transmit the monochromatic laser output by the single-frequency laser to the single-mode optical fiber of the microbubble lens sensor chip (15), wherein the optical fiber jumper (14) and the single-mode optical fiber (2) are connected together via an optical fiber flange; In the microbubble lens sensor chip (15), one end of the quartz capillary (1) is connected to the microfluidic system (18), and the other end is connected to the analyte to be measured through a Teflon tube; the divergent light output from the end face of the single-mode optical fiber (2) passes through the quartz capillary (1) and is shaped into collimated parallel light and transmitted to the CCD imaging device (16) at the far end; The CCD imaging device (16) receives the output light signal and converts it into an electrical signal and transmits it to the computer (17); The computer (17) is used to display the size of the light spot in real time and to perform real-time processing and analysis of the light spot size or light spot pixel points; The microfluidic system (18) includes a syringe pump, a syringe and a Teflon tube, which are used to extract the analyte to be tested into the quartz microbubble lens.

8. The liquid concentration detection system according to claim 7, characterized in that: The detection process of the detection system is: Turn on the single-frequency laser to emit a monochromatic laser for detection; use the microfluidic system to extract the analyte to be tested into the quartz microbubble. The process is as follows: one end of the microfluidic system is connected to one port of the quartz microbubble, and the other port of the quartz microbubble is connected to a test tube containing the analyte to be tested through a Teflon tube; a CCD imaging device is used to collect the collimated light spot output by the quartz microbubble lens sensor chip, and it is converted into an electrical signal and transmitted to a computer; the computer is used to perform statistical analysis on the size of the light spot or the pixel points, measure the concentration of multiple groups of standard analytes to be tested, and fit a calibration curve to complete the sensing performance calibration of the liquid concentration sensor.

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