CN108896539A - Measure the optofluidic detector of phosphorus content in seawater - Google Patents

Abstract

The invention provides an optofluidic detector for measuring the phosphorus content in seawater, which can improve the stability of the detection process and ensure the accuracy and precision of the results. It is characterized in that it includes: three micro-flow pumps; the inlet part, Contains a first inlet flow channel, a second inlet flow channel, and a third inlet flow channel respectively connected to three micro-flow pumps; the mixing part includes: a plurality of longitudinal micro-flow channels arranged in parallel to each other, and a plurality of connected adjacent The transverse microfluidic channel of the longitudinal microfluidic channel, and a plurality of semicircular annular microstructures arranged in the longitudinal microfluidic channel and the transverse microfluidic channel; The outflow end of the channel is connected; the optical fiber part includes two optical fibers, the front ports of the two optical fibers are oppositely arranged on the left and right sides of the capillary colorimetric tube, and the front ports are coated with optical film to form a gap between the two ports. an optical resonator; and a laser source connected to the rear end of one optical fiber and the rear end of the other optical fiber to the spectrometer.

Description

Optofluidic Detector for Determination of Phosphorus in Seawater

technical field

The invention relates to an optofluidic detector for measuring phosphorus content in seawater.

Background technique

Seawater monitoring is an important part of environmental monitoring. Phosphate, as a typical seawater nutrient, plays a vital role in the growth of plankton in the ocean. Seawater nutrient monitoring is of great significance in understanding the material cycle in the environment and preventing the proliferation of harmful algal blooms in the ocean. There are mainly three kinds of artificial techniques for monitoring phosphate in seawater: electrochemical analysis, fluorescence labeling analysis and spectrophotometry. Electrochemical analysis has high accuracy in detecting liquids containing high concentrations of phosphate, but it is not suitable for measuring seawater with low phosphate concentrations. The fluorescent labeling method has good selectivity and high precision, but the fluorescence intensity is easily affected by the external environment. Spectrophotometric analysis is widely used in sensor development and seawater monitoring for its simplicity, effectiveness, high sensitivity, accuracy, and high reproducibility. At present, my country's marine nutrients are mainly analyzed by on-site sampling laboratories. The instruments and equipment have shortcomings such as large size and high energy consumption. Quantity control and other management needs. In recent years, with the development of microfluidic technology, these shortcomings have been overcome.

Optofluidic technology is a new interdisciplinary field, which has developed rapidly in recent years. Optofluidic technology combines optics and microfluidics to precisely control liquids on a microscopic scale. The microfluidic chip has the advantages of small size, low loss, and fast response, which can overcome the shortcomings of traditional spectrophotometric methods for measuring seawater nutrients. However, the molar coefficient of phosphate is low, the size of the optofluidic chip is small, and the signal is not stable during detection.

Contents of the invention

The present invention is carried out to solve the above problems, and the purpose is to provide an optofluidic detector for measuring phosphorus content in seawater, improve the stability of the detection process, and ensure the accuracy and accuracy of the detection results.

In order to achieve the above object, the present invention adopts the following means.

The present invention provides an optofluidic detector for measuring phosphorus content in seawater, which is characterized in that it comprises: three micro-flow pumps, respectively pumping the first indicator, the liquid to be detected, and the second indicator; Contains a first inlet flow channel, a second inlet flow channel, and a third inlet flow channel respectively connected to three micro-flow pumps; the mixing part includes: a plurality of longitudinal micro-flow channels arranged in parallel to each other, and a plurality of connected adjacent The transverse microfluidic channel of the longitudinal microfluidic channel, and a plurality of semicircular annular microstructures arranged in the longitudinal microfluidic channel and the transverse microfluidic channel, are arranged at the inflow end of the most upstream longitudinal microfluidic channel and the first The outlets of the inlet channel, the second inlet channel, and the third inlet channel are all connected; the capillary colorimetric tube, the inlet is connected with the outlet end of the longitudinal microfluidic channel arranged at the most downstream; the optical fiber part includes Two optical fibers, the front ports of the two optical fibers are oppositely arranged on the left and right sides of the capillary colorimetric tube, the two front ports are coated with optical film to form an optical resonant cavity between the two ports; and the laser source, with a The rear end of the optical fiber is connected to emit laser light, and the rear end of the other optical fiber is connected to the spectrometer, so that the spectrometer can record the output light intensity of the laser light passing through the capillary colorimetric tube, and compare it with the laser standard intensity to obtain the absorbance value .

Preferably, in the optofluidic detector for determining the phosphorus content in seawater involved in the present invention, it may also have such a feature: the second inlet channel is located between the first inlet channel and the third inlet channel, and the pump The micro flow pump sending the liquid to be tested is connected with the second inlet flow channel.

Preferably, in the optofluidic detector for determining the phosphorus content in seawater involved in the present invention, it also has such a feature: there are six longitudinal micro-flow channels, and they are sequentially set as the first to the second along the flow direction. Six vertical microfluidic channels, the length of the first vertical microfluidic channel is D1, the lengths of the second to sixth vertical microfluidic channels are equal to D2, D1:D2=1:1.5～3, and the horizontal microfluidic channel There are five channels in total, the length of which is B1, B1: D1 = 1: 1.5-3, and the width of all the longitudinal micro-fluid channels and the transverse micro-fluid channels are equal, all are W, W: D1 = 1: 15-20.

Preferably, in the optofluidic detector for determining the phosphorus content in seawater involved in the present invention, it may also have such a feature: the length D1 of the first vertical microfluidic channel=3256 μm, the length of the remaining vertical microfluidic channels D2 = 6512 μm, the length B1 of the lateral microfluidic channel = 1628 μm, and the width W of all the microfluidic channels = 200 μm.

Preferably, in the optofluidic detector for determining the phosphorus content in seawater involved in the present invention, it may also have such a feature: at least three The semicircular microstructure, the outer diameter of the semicircular microstructure is E, where E:W=3˜8:12.

Preferably, in the optofluidic detector for measuring the phosphorus content in seawater involved in the present invention, it may also have such features: the inner diameter of the semicircular ring microstructure is 30 μm, the outer diameter E=60 μm, and each transverse microfluidic groove There are 6 semicircular microstructures in the channel, 3 semicircular microstructures are arranged in the first vertical microfluidic channel, and 30 semicircular microstructures are respectively arranged in the second to sixth longitudinal microfluidic channels. In each longitudinal microfluidic channel and each transverse microfluidic channel, the center distances between adjacent semicircular microstructures are not equidistant, and the centers of adjacent semicircular microstructures are not on a straight line.

Preferably, in the optofluidic detector for determining the phosphorus content in seawater involved in the present invention, it may also have such a feature: the adjacent semi-circular microstructures are not equidistantly distributed with a center distance of 280 μm or 150 μm, and The opening line of the semi-circular microstructure forms an angle of 60° or 120° with the axial direction of the microfluidic channel.

Preferably, in the optofluidic detector for determining the phosphorus content in seawater involved in the present invention, it may also have such a feature: the longitudinal microfluidic channel is bent once every 1000 μm, the arc of the bend is 180°, and the curved part The inner diameter is 100μm, the outer diameter is 300μm, and the arc length is about 628μm, which works best.

Preferably, in the optofluidic detector for determining the phosphorus content in seawater involved in the present invention, it may also have such features: the optical film is a gold film, and the front ports of the two optical fibers are respectively fixed on the left side of the capillary colorimetric tube. , on the right side wall, and the end face of the front port is flush with the inner surface of the side wall.

Preferably, in the optofluidic detector for determining phosphorus content in seawater involved in the present invention, it may also have such a feature: the first indicator and the second indicator are respectively ammonium molybdate solution and antimony potassium tartrate solution.

Preferably, in the optofluidic detector for determining the phosphorus content in seawater involved in the present invention, it may further include: a waste liquid collecting part, which communicates with the outlet of the capillary colorimetric tube; and a spectrometer.

Function and Effect of Invention

The optofluidic detector for determining the phosphorus content in seawater provided by the present invention realizes the real-time quantitative detection of the phosphate content in seawater through microfluidic channels combined with spectrophotometry, and the optical resonant cavity reduces the size of the device while reducing the size of the device. The accuracy of the system is increased. The detection limit of the optofluidic detector provided by the invention can reach 0.1 μmol/L, the measurement range is 0.1-100 μmol/L, and the detection accuracy can reach ±10%. The invention combines the spectrophotometric analysis method, the optical resonant cavity and the microfluidic control, and utilizes the optical fluidic control technology to develop a highly integrated marine nutrient salt sensing chip, which has important research value.

Description of drawings

Fig. 1 is a schematic structural view of an optofluidic detector for measuring phosphorus content in seawater according to an embodiment of the present invention;

Fig. 2 is an enlarged view of the semi-circular microstructure in the microfluidic channel involved in the embodiment of the present invention;

Figure 3 is an effect diagram of liquid mixing in the mixing part of the embodiment of the present invention, wherein (a) is a plan view of the mixing part, (b) is a longitudinal section view of the channel and a plan view of the microstructure, (c) is a mixing 3D images of internal entrances and exits;

Fig. 4 is the spectrogram of laser incidence and emission after the indicator detected by the spectrometer in the embodiment of the present invention reacts with the liquid to be detected; and

Fig. 5 is a graph showing the relationship between the concentration of the phosphate standard solution and the absorbance involved in the embodiment of the present invention.

Detailed ways

The optofluidic detector for determining the phosphorus content in seawater involved in the present invention will be described in detail below with reference to the accompanying drawings.

<Example>

As shown in Figure 1, the optofluidic detector 10 for measuring phosphorus content in seawater comprises: three microflow pumps 21 to 23, an inlet part 30, a mixing part 40, a capillary colorimetric tube 50, an optical fiber part 60, and a laser source 70 , spectrometer 80 and waste liquid collection part 90.

The three micro-flow pumps 21 to 23 are sequentially used to pump the first indicator, the liquid to be detected, and the second indicator. In this embodiment, the pumping speed of the liquid to be tested is 200 μl/min, and the pumping speeds of the first indicator and the second indicator are respectively 40 μl/min. The liquid to be detected here is an aqueous solution containing phosphate ions, which can be a seawater sample or a phosphate standard solution prepared in the laboratory. The first indicator and the second indicator are ammonium molybdate solution and antimony potassium tartrate respectively. solution. In the present embodiment, the first indicator is the concentration of 0.14g/ml ammonium molybdate solution, 0.03g/ml antimony potassium tartrate solution, 0.92g/ml sulfuric acid solution according to 18%, 2%, 80% The volume ratio is mixed; the specific preparation method is as follows: slowly add 300ml of sulfuric acid to 600ml of water under stirring to obtain a sulfuric acid solution, weigh 28g of ammonium molybdate, dissolve it in 200ml of water to obtain an ammonium molybdate solution, and at the same time, dissolve 6g of antimony tartrate Potassium is dissolved in 200ml of water with antimony potassium tartrate. Finally, add 45ml of ammonium molybdate solution to 200ml of sulfuric acid solution under stirring, and add 5ml of antimony potassium tartrate solution to mix to obtain a mixed solution. Store it in a brown glass bottle. The solution becomes cloudy After that, reformulate. The second indicator is 0.01g/ml ascorbic acid solution. The specific preparation method is as follows: weigh 20g of ascorbic acid in 200ml of water, store in a brown reagent bottle or a polyethylene bottle, store it in the dark at 4°C, and reconstitute after the liquid becomes turbid.

The inlet portion 30 includes a first inlet channel 31 , a second inlet channel 32 , a third inlet channel 33 , and a confluence channel 34 .

The first inlet channel 31 and the third inlet channel 33 communicate with the micro-flow pumps 21 and 23 respectively for introducing the first indicator and the second indicator. In this embodiment, the width of the first inlet channel 31 and the third inlet channel 33 are both 200 μm, and the depth is 125 μm.

The second inlet flow channel 32 is connected with the micro-flow pump 22, and the liquid to be tested is introduced. When the liquid to be tested is a seawater sample, a polymer membrane filter 24 needs to be installed before the second inlet flow channel 32. The polymer membrane filter Device 24 refers to a filter made with a membrane with a certain aperture (multiple polymers are materials, such as cellulose acetate membrane and nylon membrane, etc.), which can remove microorganisms in seawater, materials such as silt and sediment. In this embodiment, a polymer membrane filter with a pore size of 50 μm is used for pretreatment of seawater, and the second inlet channel 32 has a width of 200 μm and a depth of 125 μm. In addition, the second inlet channel 32 is also used to introduce ultrapure water to clean the channel.

The inlet of the merged channel 34 is connected with the first inlet channel 31 , the second inlet channel 32 and the third inlet channel 33 . In this embodiment, the width is 200 μm, the depth is 125 μm, and the length is within 2000-5000 μm.

As shown in FIGS. 1 and 2 , the mixing part 40 includes a plurality of longitudinal microfluidic channels 41 , lateral microfluidic channels 42 , and semicircular annular microstructures 43 . All vertical microfluidic channels 41 are arranged parallel to each other. All the transverse microfluidic channels 42 are also arranged parallel to each other, and each transverse microfluidic channel 42 is located between two adjacent vertical microfluidic channels 41 . The semicircular microstructure 43 is arranged in the longitudinal microfluidic channel 41 and the lateral microfluidic channel 42, and at least three semicircular microstructures are arranged in each longitudinal microfluidic channel 41 and each lateral microfluidic channel 42 43.

In this embodiment, in order to fully react the liquid to be detected with the indicator and save reaction time, after repeated tests, six vertical microfluidic channels 41 and five horizontal microfluidic channels 42 are set in the mixing module.

Along the flow direction F, the six vertical microfluidic channels 41 are sequentially set as the first to sixth vertical microfluidic channels 41 . The inflow end of the first longitudinal microfluidic channel 41 is connected with the outlet of the confluent flow channel 34 and has a length D1. The lengths of the second to sixth vertical microfluidic channels 41 are equal to D2, D1:D2=1:1.5˜3. In this embodiment, the length D1 of the first vertical microfluidic channel 41 is 3256 μm, and the length D2 of the second to sixth vertical microfluidic channels 41 is 6512 μm. As shown in FIG. 3( a ), in this embodiment, the longitudinal microfluidic channel 41 is bent every 1000 μm with an arc of 180°. The inner diameter of the curved part is 100 μm, the outer diameter is 300 μm, and the arc length is about 628 μm.

The lengths of the five lateral microfluidic channels 42 are equal, all of which are B1, where B1:D1=1:1.5˜3. In this embodiment, the length B1 of the lateral microfluidic channel 42 is 1628 μm.

All the vertical microfluidic channels 41 and the lateral microfluidic channels 42 have the same width, which is W, W: D1 = 1: 15-20. In this embodiment, the width W of all microfluidic channels is 200 μm.

The outer diameter of the semicircular microstructure 43 is E, where E:W=3˜8:12. In this embodiment, the inner diameter of the semicircular microstructure 43 is 30 μm, and the outer diameter E=60 μm; three semicircular microstructures 43 are arranged in the first vertical microfluidic channel 41; Each channel 41 is provided with 30 semicircular microstructures 43 ; and each lateral microfluidic channel 42 is provided with 6 semicircular microstructures 43 .

In order to further promote the full mixing of the liquid to be detected and the indicator, and to speed up the reaction between the liquid to be detected and the indicator, the semicircular ring forms a certain angle with the channel in the microfluidic channel, and these microstructures are not in a straight line. The liquid to be detected and the indicator can be fully mixed in the mixer, and a color reaction occurs. Specifically, in this embodiment, in each vertical microfluidic channel 41 and each lateral microfluidic channel 42, the adjacent semicircular microstructures 43 are not equidistantly distributed with a center distance of 280 μm or 150 μm, and The line connecting the openings of the semicircular microstructures 43 forms an angle of 60° or 120° with the axial direction of the microfluidic channel, and the centers of the semicircular microstructures 43 are not on a straight line.

As shown in Figure 3, in order to have a more intuitive three-dimensional mixing effect, the liquid to be tested was stained with Rhodamine B reagent, and the indicator was stained with Rhodamine 6G reagent. The liquid to be tested and the indicator were pumped into the mixing module at a flow rate of 200 μl/min and 40 μl/min respectively by a microflow pump. It can be seen from the diagrams in Figure 3 that the liquid to be tested and the indicator are fully mixed in the mixing part, which greatly saves the reaction time.

The inlet of the capillary colorimetric tube 50 communicates with the outlet end of the most downstream longitudinal microfluidic channel 41 . The capillary colorimetric tube 50 has a depth of 125 μm and a width of 300 μm. The liquid to be detected and the indicator are introduced into the capillary colorimetric tube 50 after they are fully mixed in the liquid mixing part 40 to react.

In this embodiment, the templates of the mixing part 40 and the capillary colorimetric tube 50 are made of the organic material polydimethylsiloxane (Polydimethylsiloxane, referred to as PDMS) material, and are made by standard ultraviolet lithography technology: first draw according to the design software Make a mask with a good pattern, and then develop the pattern on the silicon wafer, that is, the PDMS mold, through ultraviolet lithography technology. Then pour unsolidified PDMS on the PDMS mold, and bake it at a temperature of 75 degrees Celsius for 1 hour to solidify to obtain a semi-finished product; after cutting and bonding with a glass slide through plasma flame processing, the finished product is obtained.

The optical fiber part 60 comprises two optical fibers 61 and 62, and the front ports of the two optical fibers 61 and 62 are oppositely arranged on the left and right sides of the capillary colorimetric tube 50, and the front ports are all coated with an optical film, so that between the two front ports form an optical resonant cavity. In this embodiment, the outer diameters of the two optical fibers 61 and 62 are both 125 μm; the optical film used is a gold film, and the front ports of the two optical fibers are respectively fixed on the left and right side walls of the capillary colorimetric tube 50, and the front ports The end face of the port is flush with the inner surface of the side wall, and the end faces of the two front ports are parallel to each other to form a Fabry-Perot cavity, and the length of the cavity is the width of the capillary colorimetric tube; specifically, the front port of the optical fiber 61 is A 40nm thick gold film is plated in a vacuum evaporation machine. The front port of the optical fiber 62 is plated with a 60nm thick gold film in a vacuum evaporation machine to form two mirrors with a high refractive index. Reflecting back and forth in the microcavity between them, the optical path length has been increased.

In this embodiment, we use a fiber aligner to align the optical fibers 61 and 62 . The fiber aligner consists of a grooved iron plate and a magnetic pressure block. First, put the fiber into the groove. Then, the base is carefully moved under the microscope to align the two optical fibers 61 and 62 . After alignment, add a small amount of UV-curable glue, and after 3-5 minutes of ultraviolet light irradiation, the optical fiber can be fixed. There is a channel reserved for the optical fiber in the PDMS, and the purple light curing glue is added into the reserved channel. The purple light curing glue can play a role of fixing and sealing, and prevent the liquid in the capillary colorimetric tube 50 from flowing out.

The laser source 70 is connected to the rear end of the optical fiber 61 and can emit laser light close to the absorption peak wavelength (882nm).

The spectrometer 80 is connected to the rear end of the optical fiber 62, records the output light intensity of the laser light passing through the capillary colorimetric tube 50, and compares it with the laser standard intensity to obtain an absorbance value.

The waste liquid collecting part 90 communicates with the outlet of the capillary colorimetric tube 50 to collect the discharged waste liquid.

The above is the specific structure of the optofluidic detector 10 provided in this embodiment. Based on the above structure, this embodiment further adopts the phosphorous molybdenum blue spectrophotometric method to measure the phosphorus content in seawater. In acidic medium, phosphate reacts with ammonium molybdate to form phosphomolybdenum yellow, which is reduced to phosphomolybdenum blue after adding ascorbic acid. The product is stable in acidic environment and has a strong absorption peak near the wavelength of 882nm, which is convenient for analysis by spectrophotometry. Its molar absorption coefficient is 3.6×10 ³ mol ^-1 cm ^-1 . According to the Lambert-Beer law, the proportion of light absorbed by the transparent medium has nothing to do with the intensity of the incident light. On the optical path, every medium of equal thickness absorbs the same proportion of light, so in dilute solution (concentration less than 0.01mol/L) Absorbance can be used to quantitatively calculate the phosphate concentration in a solution. This detection method not only has the advantages of good selectivity, high sensitivity, accuracy, stability and reliability, but also combines the micron-level detection precision structure, which can greatly reduce the size and energy consumption of the equipment, and use a small amount of reagent consumption (microliter, nanoliters) for rapid nutrient testing.

Specifically, in this embodiment, taking the measurement of the phosphorus content of the phosphate standard solution as an example, the operation method of the optofluidic detector 10 is described:

1. First use the micro-flow pump 22 to pump ultrapure water into the second inlet flow channel 32 at a flow rate of 200 μl/min for 1 min to clean the channel. At the same time, it can also be used as a reference background to start the laser source 70 and the spectrometer 80 , the spectrometer 80 records the light intensity signal received at this time.

2. After cleaning, the first indicator and the second indicator are pumped into the first inlet channel 31 and the third inlet channel 33 by using the micro-flow pumps 21 and 23, and then flow to the mixing part 40 at a flow rate of 40 μl /min, then the filtered liquid to be detected (especially for seawater samples) is pumped into the mixing part 40 from the second inlet channel 32 by using the microflow pump 22, and the flow rate is also 200 μl/min for 2min, so that the liquid to be detected The liquid and the indicator are fully mixed and reacted.

3. Record the light intensity signal again, and compare it with the light intensity signal in the first step to obtain the absorbance value. The phosphate concentration was quantitatively calculated using Lambert-Beer's law. It is also possible to use the method of first drawing the phosphate standard solution and the absorbance curve table, and obtain the phosphate concentration of the solution to be tested by querying the table and the curve.

In this example, phosphate standard solutions with concentrations of 10 μmol/L, 40 μmol/L, 60 μmol/L, and 100 μmol/L were prepared, and then the above-mentioned steps 1 to 3 were performed to record different concentrations of The light intensity signal detected after the phosphate standard solution passes through the optofluidic detector 10 is drawn into a spectrogram as shown in Figure 4; Figure 4 shows that the phosphate standard solution of different concentrations passes through the Fabry after color development. —The light intensity signal output by the Perot cavity. It can be seen from the figure that the light intensity signal will decrease with the increase of the phosphate concentration. With the maximum light intensity (0 μmol/L) as a reference, according to the Lambert-Beer law, the spectrometer can calculate the absorbance of each concentration of phosphate, as shown in Figure 5, there is a good linear relationship between the absorbance and the concentration of the liquid to be detected, and The error range is not more than 10%, which is consistent with the Lambert-Beer law, which proves that the scheme is effective. Compared with traditional detection devices, the detection range of the optofluidic detector 10 provided in this embodiment has been greatly improved. At the same time, through multiple experiments, it is confirmed that the detection limit of the optofluidic detector 10 in this solution can reach 0.1 μmol/L.

The above is only an illustration of the technical solution of the present invention. The optofluidic detector for determining the phosphorus content in seawater involved in the present invention is not limited to the structure described above, but is subject to the scope defined in the claims. Any modifications, supplements or equivalent replacements made by those skilled in the art of the present invention on this basis are within the scope of protection required by the claims of the present invention.

Claims (10)

1. An optofluidic detector for measuring phosphorus content in seawater, characterized in that it comprises: Three micro-flow pumps, respectively pumping the first indicator, the liquid to be detected, and the second indicator; The inlet part includes a first inlet flow channel, a second inlet flow channel, and a third inlet flow channel respectively connected to three micro-flow pumps; The mixing part includes: a plurality of longitudinal microfluidic channels arranged parallel to each other, a plurality of lateral microfluidic channels connecting adjacent said longitudinal microfluidic channels, and a plurality of longitudinal microfluidic channels and said lateral microfluidic channels A plurality of semi-circular microstructures in the microfluidic channel are arranged at the inflow end of the most upstream longitudinal microfluidic channel and the first inlet channel, the second inlet channel, and the third inlet The outlets of the runners are all connected; A capillary colorimetric tube, the inlet of which is in communication with the outflow end of the longitudinal microfluidic channel arranged at the most downstream; The optical fiber part includes two optical fibers. The front ports of the two optical fibers are oppositely arranged on the left and right sides of the capillary colorimetric tube. The two front ports are coated with an optical film to make the two ports form an optical resonant cavity between them; and a laser source connected to the rear end of one of said optical fibers for emitting laser light, Wherein, the rear end of the other optical fiber is connected to a spectrometer, so that the spectrometer records the output light intensity of the laser light passing through the capillary colorimetric tube, and compares it with the laser standard intensity to obtain an absorbance value. 2. the optofluidic detector of measuring phosphorus content in seawater according to claim 1, is characterized in that: Wherein, the second inlet channel is located between the first inlet channel and the third inlet channel, The micro-flow pump for pumping the liquid to be detected is connected with the second inlet channel. 3. the optofluidic detector of measuring phosphorus content in seawater according to claim 1, is characterized in that: Wherein, there are six vertical microfluidic channels, and they are sequentially set as the first to sixth vertical microfluidic channels along the flow direction, the length of the first vertical microfluidic channel is D1, and the length of the second to sixth vertical microfluidic channels is D1. The lengths of the sixth longitudinal microfluidic channel are equal to D2, D1:D2=1:1.5～3, There are five transverse microfluidic channels, all of which have a length of B1, B1:D1=1:1.5-3, All the longitudinal microfluidic channels and the lateral microfluidic channels have the same width, which is W, and W: D1 = 1:15-20. 4. the optofluidic detector of measuring phosphorus content in seawater according to claim 3, is characterized in that: Wherein, the length D1 of the first vertical microfluidic channel is 3256 μm, and the length D2 of the other vertical microfluidic channels is 6512 μm, The length B1 of the lateral microfluidic channel is 1628 μm, The width W=200 μm of all microfluidic channels. 5. the optofluidic detector of measuring phosphorus content in seawater according to claim 3, is characterized in that: Wherein, at least three of the semi-circular microstructures are arranged in each of the longitudinal microfluidic channels and each of the lateral microfluidic channels, The outer diameter of the semi-circular microstructure is E, where E:W=3˜8:12. 6. the optofluidic detector of measuring phosphorus content in seawater according to claim 5, is characterized in that: Wherein, the inner diameter of the semi-circular microstructure is 30 μm, the outer diameter E=60 μm, Each of the lateral microfluidic channels is provided with 6 semi-circular microstructures, Three semicircular microstructures are arranged in the first longitudinal microfluidic channel, and 30 semicircular microstructures are respectively arranged in the second to sixth longitudinal microfluidic channels, In each of the longitudinal microfluidic channels and each of the lateral microfluidic channels, the distances between the centers of adjacent semicircular microstructures are not equidistant, and the centers of adjacent semicircular microstructures Not in a straight line. 7. the optofluidic detector of measuring phosphorus content in seawater according to claim 6, is characterized in that: Wherein, the adjacent semicircular microstructures are not equidistantly distributed with a center distance of 280 μm or 150 μm, and the opening line of the semicircular microstructures forms an angle of 60° or 120° with the axial direction of the microfluidic channel . 8. the optofluidic detector of measuring phosphorus content in seawater according to claim 1, is characterized in that: Wherein, the optical film is a gold film, and the front ports of the two optical fibers are respectively fixed on the left and right side walls of the capillary colorimetric tube, and the end faces of the front ports are in contact with the inner surfaces of the side walls. flush. 9. the optofluidic detector of measuring phosphorus content in seawater according to claim 1, is characterized in that: Wherein, the first indicator and the second indicator are ammonium molybdate solution and antimony potassium tartrate solution respectively. 10. the optofluidic detector of measuring phosphorus content in seawater according to claim 1, is characterized in that, also comprises: A waste liquid collecting part communicates with the outlet of the capillary colorimetric tube; and The spectrometer.