Chip sensor for soil nutrient analysis

Abstract

The utility model relates to the technical field of chip sensors, in particular to a chip sensor for soil nutrient analysis, which is formed by arranging three chip sensor units along the same direction. Each chip sensor unit comprises a chip structure, a micro-channel, two buffer solution inlets and a C4D detection electrode; the first laminated board is provided with a sample adding hole, the second laminated board is provided with a sample injection port, the sample injection port is communicated with the first end of the sample adding hole, and a polycarbonate track etching film is arranged at the communication part; the micro-channel is arranged on the upper surface of the MCE chip, and the sample injection port is communicated with the micro-channel; the two buffer solution inlets penetrate through the first laminated board and the second laminated board and are respectively communicated with two ends of the microchannel; the C4D detection electrode is disposed on the corrosion-resistant film. According to the utility model, the to-be-detected sample can be prevented from flowing into the chip in the detection process, and the number of connections between the chip and operation equipment is reduced to three.

Description

Technical Field

[0001] The utility model relates to the technical field of chip sensors, in particular to a chip sensor for soil nutrient analysis. Background Art

[0002] Macronutrients in soil, such as nitrogen, phosphorus, and potassium, play a vital role in crop growth and agricultural production. Rapid, quantitative, on-site detection of their content is crucial for guiding precise fertilization. Many researchers have attempted to simplify extraction procedures, allowing for on-site measurement of soil sample extracts and subsequent measurement using portable devices. Artigas et al., Kim et al., Shaw et al., and Wang Hongren have used ion-selective sensors or ion-selective field-effect transistors to detect soil nutrients. These sensors offer advantages such as high sensitivity, rapid response, and simplified sample pretreatment. However, ion-selective electrodes require static operation and cannot achieve online nutrient detection. Researchers have also investigated the use of colorimetric test strips with optical readouts for nutrient labeling. These techniques must adapt to the analyte ions by selecting appropriate ion-selective membranes or test strips. Consequently, simultaneous measurement of various nutrients is complex or requires the use of multiple instruments.

[0003] In recent years, the Institute of Intelligent Technology of the Hefei Institute of Physical Science, Chinese Academy of Sciences, and Anhui University of Science and Technology have collaborated to develop a new type of capacitive-coupled contactless conductivity detection microfluidic chip with integrated 3D microelectrodes, which has achieved the separation and rapid quantitative detection of multiple nutrients in soil, solving the traditional C 4 D. The problem of insufficient sensitivity of the sensing electrodes in microfluidic devices. When testing soil, the soil to be tested is prepared into a sample solution and then tested using the above-mentioned chip. However, due to the pressure caused by non-horizontal directions during the test, the chip is subjected to pressure, causing some sample solution to flow into the chip, which seriously affects the accuracy of the test. To reduce this effect, the method of increasing the number of chips is usually adopted, so that the number of connections between the chip and the detection device is at least four. However, this does not truly improve the accuracy of the test and also reduces work efficiency. Utility Model Content

[0004] In order to solve the above problems, the utility model provides a chip sensor for soil nutrient analysis.

[0005] To achieve the above objectives, the specific technical solutions of the present utility model are as follows.

[0006] A chip sensor for soil nutrient analysis, wherein the chip sensor for soil nutrient analysis is composed of three chip sensor units arranged in the same direction;

[0007] Each of the chip sensor units comprises:

[0008] The chip structure includes a first laminate, a second laminate, an MCE chip, an anti-corrosion film, and a glass layer arranged in order from top to bottom; the first laminate is provided with a sample loading hole, the second laminate is provided with a sample injection port, the sample injection port is connected to the first end of the sample loading hole, and a polycarbonate track etching film is provided at the connection point;

[0009] A microchannel is configured on the upper surface of the MCE chip;

[0010] Two buffer inlets, both of which penetrate the first laminate and the second laminate and are respectively connected to two ends of the microchannel;

[0011] The C 4 The D detection electrode is configured on the anti-corrosion film and is located at a side away from the sample injection port.

[0012] The chip structure of the present invention adopts a multi-layer chip structure, in which a polycarbonate track-etched membrane is provided between the sample injection port and the sample addition hole. This membrane can serve as a barrier between the soil fluid to be detected and the microchannel, thereby precisely controlling the soil fluid to be detected and preventing the leakage of the soil fluid to be detected into the chip due to pressure caused by non-horizontal directions. This effectively improves the accuracy and stability of detection and reduces the number of connections between the chip sensor and the operating equipment from four to three.

[0013] In another preferred embodiment, the second end of the sample addition hole is connected to a sample storage chamber for disposing a soil sample to be tested.

[0014] In another preferred embodiment, a first Pt electrode is disposed in the sample storage cavity.

[0015] In another preferred embodiment, near the C 4 The buffer inlet on one side of the D detection electrode is connected to a pressure bottle, and the other buffer inlet is connected to a collection bottle.

[0016] In another preferred embodiment, a second Pt electrode is disposed in both the collecting bottle and the pressure bottle.

[0017] In another preferred embodiment, the C 4 The length of the microchannel between the D detection electrode and the sample injection port is 44 mm to 64 mm.

[0018] In another preferred embodiment, the microchannel has a width of 100 μm to 100.5 μm and a height of 55 μm to 55.5 μm.

[0019] In another preferred embodiment, the size of the MCE chip is 16 mm to 16.5 mm × 26 mm to 26.5 mm.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The chip sensor for soil nutrient analysis provided by the present invention has a multi-layer chip structure, a polycarbonate track etched membrane is provided between the sample injection port and the sample addition hole, and the nanoporous polycarbonate track etched membrane is used as a barrier between the soil fluid to be detected and the microchannel, so as to accurately control the soil fluid to be detected, thereby preventing the sample from leaking into the chip due to pressure from a non-horizontal direction during the detection process, effectively improving the detection accuracy, and thus reducing the number of connections between the chip and the device. The chip sensor for soil nutrient analysis in the present invention not only ensures detection accuracy, but also meets the requirement of performing at least three sets of parallel experiments during the detection process, that is, the number of connections between the chip sensor and the operating device is only three, effectively improving work efficiency.

[0022] (2) The sample injection method of the utility model is to insert a pipette into the sample storage chamber, which can ensure the precise control of the sample. This expands the technology for measuring ion concentration in soil sample extracts. This chip sensor for on-site soil nutrient analysis is characterized by portability and high sensitivity. It can quickly detect the nutrient content in the soil on-site, providing strong support for precision agriculture. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A three-dimensional structural diagram of a chip sensor for soil nutrient analysis.

[0024] Figure 2 Schematic top view of the chip sensor unit.

[0025] Figure 3 Schematic diagram of the chip sensor unit structure, where L1 is 900μm.

[0026] Figure 4 for Figure 3 Enlarged view of point B in the figure, where L2 is 100 μm.

[0027] Figure 5 Schematic diagram of the detection process of the chip sensor for soil nutrient analysis.

[0028] Description of the accompanying drawings: 1-chip sensor unit, 11-microchannel, 12-C 4D detection electrode, 13-sample injection port, 14-buffer inlet, 15-polycarbonate track etching membrane, 16-first laminate, 17-second laminate, 18-anti-corrosion membrane, 19-glass layer, 2-sample storage chamber, 3-pressure bottle, 4-collecting bottle, 5-first Pt electrode, 6-second Pt electrode. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0030] Unless otherwise specified, the experimental methods described in the following examples are all conventional methods; the reagents and materials described are all commercially available unless otherwise specified.

[0031] like Figure 1 As shown, the soil nutrient analysis chip sensor consists of three chip sensor units 1 arranged in the same direction. The MCE chip measures 16 mm x 26 mm, and the long sides of the three chip sensor units are interconnected. The MCE chip is a microchip capillary electrophoresis chip purchased from Hanwei Technology Group.

[0032] like Figure 2 As shown, each chip sensor unit includes a chip structure, a microchannel 11, two buffer inlets 14 and C 4 D detection electrode 12. Among them, C 4 The D detection electrode 12 is an electrode used for capacitive coupling non-contact conductivity measurement, and is purchased from Hanwei Technology Group.

[0033] like Figure 3 and Figure 4 As shown, the chip structure includes, from top to bottom, a first laminate 16, a second laminate 17, an MCE chip, an anti-corrosion film 18, and a glass layer 19. The thickness of the first laminate 16 is 125 μm, and the thickness of the second laminate 17 is 55 μm. Both the first and second laminates 16 and 17 are made of polymethyl methacrylate. The polycarbonate track etched film 15 is a nanoporous polycarbonate track etched film. The anti-corrosion film 18 is an Odell dry film. The MCE chip measures 16 mm x 26 mm.

[0034] A sample loading hole is provided on the first laminate 16, and a sample injection port 13 is provided on the second laminate 17. The sample injection port 13 is connected to the first end of the sample loading hole, and a polycarbonate track etching film 15 is provided at the connection point; wherein, the diameter of the sample injection port 13 is 100 μm, and the diameter of the sample loading hole is 900 μm.

[0035] The microchannel 11 is configured on the upper surface of the MCE chip. The width of the microchannel is 100 μm and the height is 55 μm. The sample injection port 13 is connected to the microchannel 11. The two buffer inlets 14 both pass through the first laminate 16 and the second laminate 17 and are respectively connected to the two ends of the microchannel 11; among them, the diameter of the buffer inlet 14 is 900 μm.

[0036] C 4 The D detection electrode 12 is disposed on the anti-corrosion film 18 and is located on the side away from the sample injection port 13. 4 The length of the microchannel 11 between the D detection electrode 12 and the sample injection port 13 is 44 mm to 64 mm.

[0037] The second end of the sample adding hole is connected to the sample storage chamber 2 for disposing the soil sample to be tested; the sample storage chamber 2 is provided with a first Pt electrode 5. 4 The buffer inlet 14 on one side of the D detection electrode 12 is connected to the pressure bottle 3 , and the other buffer inlet 14 is connected to the collection bottle 4 . The second Pt electrode 6 is disposed in both the collection bottle 4 and the pressure bottle 3 .

[0038] The present invention uses a nanoporous polycarbonate track-etched membrane 15 as a barrier between the sample storage cavity 2 and the microchannel 11, thereby preventing the pressure caused by the non-horizontal direction of the chip sensor from causing the sample to leak into the chip and affect the detection results.

[0039] The use process of this utility model is as follows:

[0040] 1. Preparation of buffer

[0041] A 200 mmol / L buffer solution with a pH of 6.5 is prepared by mixing 30 mmol / L DL-histidine, 30 mmol / L 2-(N-morpholino)ethanesulfonic acid, 4 mmol / L crown-6-ether, and 0.1% methylcellulose. The high background concentration of the buffer solution improves sample conductivity and reduces the effect of sample composition changes on the injected sample volume. Furthermore, the addition of the buffer solution stabilizes the sample pH.

[0042] The calibration sample was prepared by mixing 200mmol / L KNO3, 200mmol / L NH4H2PO4, 200mmol / L CaCl2 and Na2SO4 to make a 30mmol / L calibration sample.

[0043] 2. Sample processing

[0044] After the collected soil sample was sieved through a 1 mm mesh, 15 g was taken and mixed with 30 mL of deionized water in a 50 mL plastic container, and oscillated for 15 minutes using an orbital micro-oscillator with a rotation frequency of 1 Hz to obtain a suspension.

[0045] The suspension was filtered using a 0.22 μm syringe filter, wherein the 0.22 μm syringe filter was a glass and polymer combination filter, to obtain 11 mL of filtered sample.

[0046] Take 1 mL of the filtered sample and mix it with 0.18 mL of 200 mmol / L buffer to obtain the sample to be tested.

[0047] 3. Sensor calibration

[0048] The sensor was tested by extracting soil nutrients with deionized water.

[0049] The concentrations of the four nutrient ions in the deionized water extract were named CNO3, CNH4, CK and CPO4. 3- NH 4+ , K + and PO 4- The standard concentrations are 5mol / L±0.25mol / L, 10mol / L±0.5mol / L, 50mol / L±2.5mol / L, 100mol / L±5mol / L, 200mol / L±10mol / L, and 500mol / L±25mol / L. Calibration is required multiple times during full-day measurements.

[0050] 4. Measurement process

[0051] like Figure 5 As shown, the inflation syringe output port of the syringe pump is connected to the buffer inlet 14. The overpressure generated by the inflation syringe is used to introduce the buffer into the microchannel 11. A 0.16 mL sample to be tested is injected into the sample storage chamber 2 using a manual pipette. The two buffer inlets 14 of the chip sensor are connected to flexible tubes, one end of which leads to the collection bottle 4 and the pressure bottle 3, respectively. The pressure of the pressure bottle 3 is switched to 100 kPa to transfer the buffer in the microchannel 11 to the collection bottle 4.

[0052] The first Pt electrode 5 is immersed in the sample storage cavity 2, and the second Pt electrode 6 is respectively immersed in the collection bottle 4 and the pressure bottle 3. By applying a voltage between the first Pt electrode 5 and the second Pt electrode 6, the sample to be detected in the sample storage cavity 2 is ionized into anions and cations by the electrophoresis effect. The anions enter the microchannel 11 in the chip sensor, and the cations continue to remain in the sample storage cavity 2.

[0053] After the anions enter the microchannel 11, a high voltage is applied between the collecting bottle 4 and the pressure bottle 3. In order to suppress the cations from flowing into the microchannel 11, the voltage in the sample storage chamber 2 is adjusted to obtain a small current flowing back to the sample storage chamber 2, thereby pulling the remaining cations back into the sample storage chamber 2. The voltage in the sample storage chamber 2 is detected by the first Pt electrode 5 to be -1600V and -2000V in the pressure bottle 3 at this time. The applied voltage pattern causes the anions injected into the microchannel 11 to migrate toward the second Pt electrode 6 in the collecting bottle 4. The second Pt electrode 6 in the collecting bottle 4 is connected to the detection device for detecting signals. During the movement, due to the different types of individual anions, their electrophoretic mobility is split, thereby achieving the separation of different types of anions, and these different types of anions can pass through the detection device independently, and the signal generated by the detection device is recorded, that is, the electrophoresis diagram, and the peak surface is evaluated by the baseline and peak as well as the peak area through the integration algorithm. Since three sets of parallel experiments are usually required during the detection process to eliminate the influence of external factors on the detection results, the peak surface evaluations of the three chip sensor units are averaged to obtain the content of different ions in the soil nutrients in the sample to be tested.

[0054] The above voltage pattern is suitable for detecting the injection and separation of anions in soil samples. For the detection of cations in soil samples, all voltages can be applied in reverse.

[0055] After the injection voltage is turned off, the sample enters the microchannel 11, forming a sample liquid flow. The length of the sample liquid flow, i.e., the sample plug, is controlled by time. The duration of the high injection voltage defines the length of the sample plug in the microchannel. The voltage between the sample reservoir 2 and the pressure bottle 3 is -2000V. By adjusting the plug length, the sensor characteristics can be adjusted, extending the injection time and thereby increasing the injected sample volume, thereby improving the sensor's sensitivity.

[0056] In the absence of voltage, the nanoporous polycarbonate track-etched membrane 15 blocks cations in the sample to be tested from flowing into the microchannel 11, preventing self-driven injection due to pressure differences caused by unequal liquid levels in the sample storage chamber 2 or diffusion. If a high injection voltage is applied between the sample storage chamber 2 and the pressure bottle 3, cations in the sample to be tested can enter the microchannel 11 through the pores of the nanoporous polycarbonate track-etched membrane 15 and undergo electrophoretic movement.

[0057] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0058] Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if such modifications and variations fall within the scope of the claims of the present invention and their equivalents, the present invention is intended to include such modifications and variations.

Claims

1. A chip sensor for soil nutrient analysis, characterized in that: The chip sensor for soil nutrient analysis is composed of three chip sensor units (1) arranged in the same direction; Each of the chip sensor units (1) comprises: A chip structure comprising a first laminate (16), a second laminate (17), an MCE chip, an anti-corrosion film (18), and a glass layer (19) arranged in sequence from top to bottom; a sample loading hole is provided on the first laminate (16), a sample injection port (13) is provided on the second laminate (17), the sample injection port (13) is connected to a first end of the sample loading hole, and a polycarbonate track etching film (15) is provided at the connection point; A microchannel (11) is arranged on the upper surface of the MCE chip, and the sample injection port (13) is connected to the microchannel (11); Two buffer inlets (14) are configured to penetrate the first laminate (16) and the second laminate (17) and are respectively connected to the two ends of the microchannel (11); The C 4 The D detection electrode (12) is arranged on the anti-corrosion film (18) and is located on a side away from the sample injection port (13).

2. The chip sensor for soil nutrient analysis according to claim 1, characterized in that: The second end of the sample addition hole is connected to a sample storage cavity (2).

3. The chip sensor for soil nutrient analysis according to claim 2, characterized in that: A first Pt electrode (5) is arranged in the sample storage cavity (2).

4. The chip sensor for soil nutrient analysis according to claim 1, characterized in that: Close to the C 4 The buffer inlet (14) on one side of the D detection electrode (12) is connected to a pressure bottle (3), and the other buffer inlet (14) is connected to a collection bottle (4).

5. The chip sensor for soil nutrient analysis according to claim 4, characterized in that: The collecting bottle (4) and the pressure bottle (3) are both provided with a second Pt electrode (6).

6. The chip sensor for soil nutrient analysis according to claim 1, characterized in that: The C 4 The length of the microchannel (11) between the D detection electrode (12) and the sample injection port (13) is 44 mm to 64 mm.

7. The chip sensor for soil nutrient analysis according to claim 1, characterized in that: The microchannel has a width of 100 μm to 100.5 μm and a height of 55 μm to 55.5 μm.

8. The chip sensor for soil nutrient analysis according to claim 1, characterized in that: The size of each MCE chip is 16mm-16.5mm×26mm-26.5mm.

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