Microfluidic liquid crystal sensor capable of real-time detection of organophosphorus pesticides and detection method thereof

Abstract

The present invention discloses a microfluidic liquid crystal sensor capable of real-time detection of organophosphorus pesticides and a detection method thereof. First, aluminum perchlorate is fixed on the surface of a carboxyl-modified substrate, and then the treated microchannel is combined on a glass slide. The organophosphorus pesticide, a cleaning solvent and liquid crystal are sequentially injected into the microchannel through an integrated device. The combination of organophosphorus and aluminum perchlorate causes the orientation of the liquid crystal molecules to change, resulting in an optical image change from "black" to "bright", thereby realizing the detection of the organophosphorus pesticide. The method combines liquid crystal detection technology with microfluidics to realize real-time, rapid and convenient detection of organophosphorus pesticides.

Description

Technical Field

[0001] The invention relates to liquid crystal detection technology, microfluidics, and the field of organophosphorus pesticide detection, and in particular to a microfluidic liquid crystal sensor capable of detecting organophosphorus pesticides in real time and a detection method thereof. Background Art

[0002] Organophosphorus pesticides are highly effective and have a broad spectrum, making them one of the most widely used pesticides in agriculture. However, organophosphorus pesticides inhibit the activity of acetylcholinesterase, which can cause pathological changes or even death in organisms. In recent years, excessive use of pesticides has caused serious pesticide residue problems, especially residues in fruits and vegetables, which seriously threaten people's health and cause great food safety problems. Therefore, real-time detection of organophosphorus pesticide residues is of great significance.

[0003] Currently reported methods for detecting organophosphorus pesticides include high performance liquid chromatography (HPLC), liquid chromatography-tandem mass spectrometry (LC-MS / MS), gas chromatography (GC), gas chromatography-mass spectrometry (GC-MS), gas chromatography-tandem mass spectrometry (GC-MS / MS), etc. However, these methods require complex sample processing, professional experimental personnel and sophisticated equipment, and are time-consuming to operate, and are not suitable for real-time and rapid detection.

[0004] In existing research, liquid crystal sensors have attracted widespread attention due to their simple operation, sensitive response, and low sample consumption. Microfluidic devices can miniaturize experimental processes and have the characteristics of short detection time and low cost. However, existing microfluidic detection designs still require complex signal detection and enhancement methods or equipment to assist in reading detection results. To solve these problems, the present invention combines the two and uses liquid crystals to report molecules detected in microfluidic devices, which is a significant work with broad application prospects. Summary of the invention

[0005] In order to achieve the above-mentioned invention object, the present invention adopts the following technical solutions:

[0006] A microfluidic liquid crystal sensor for detecting organophosphorus pesticides is assembled by loading a PDMS microchannel on a glass slide fixed with metal perchlorate; the organophosphorus pesticides and liquid crystals are injected into the microchannel.

[0007] Furthermore, the height of the microchannel is 10-50 μm, and the width is 100-500 μm; the metal perchlorate is one of Cu(ClO4)2, Al(ClO4)3, Zn(ClO4)2, and Fe(ClO4)3.

[0008] A method for visually detecting organophosphorus pesticides using a liquid crystal sensor comprises the following steps:

[0009] 1) Pretreatment of slides

[0010] Soak the cut glass slides in cleaning solution, clean and dry.

[0011] 2) Carboxylation of slides

[0012] 3) Fixing the slides with metal perchlorates

[0013] Add the metal perchlorate anhydrous ethanol solution to the center of the glass slide surface treated in step 2), spin-coat the metal perchlorate ethanol solution on the glass slide according to the set spin-coating parameters, dry it, and keep it dust-proof for later use.

[0014] 4) Preparation and cleaning of PDMS microchannels

[0015] 5) Assembly of microfluidic devices

[0016] The glass slide obtained in step 3) is combined with the PDMS microchannel obtained in step 4) after plasma treatment to form the desired microfluidic device.

[0017] 6) Assembly of microfluidic liquid crystal sensor

[0018] Inject organophosphorus pesticide, deionized water and liquid crystal into the device assembled in step 5) along the punched holes, and keep each substance for 30 minutes.

[0019] In the above detection method, further, in the step 1), the glass slide is immersed in a 1%-10% (V / V) decon-90 aqueous solution for 2-12 hours, and then the glass slide is washed with ultrapure water, blown dry with N2, and dust-proofed for use; in the step 2), the glass slide is carboxylated by soaking the glass slide pretreated in step 1) with a TESPSA solution at 60-100°C, rinsing with ultrapure water, blowing dry with N2, and dust-proofed for use.

[0020] In the above detection method, further, the volume fraction of the TESPSA solution is (0%-1%), and the immersion time is 2-8h.

[0021] In the above detection method, further, in the step 3), the spin coating parameters are set to 2000-6000 rpm, the spin coating time is 0.5-2 min, the metal perchlorate concentration is 5-20 mM, and the spin coating amount is 30-100 μL.

[0022] In the above detection method, further, the preparation and cleaning of the PDMS microchannel in step 4) is specifically to mix the PDMS prepolymer main agent and the curing agent in an amount of 10:1 (w / w), stir and degas, transfer the degassed mixture to the silicon master, degas, and cure in an oven at 80-110°C, and remove the microchannel from the silicon template. After cutting and punching, a microchannel with a hole is formed, and it is cleaned in isopropanol, then dried, and treated with a plasma process;

[0023] The stirring time is 5-15 minutes, the degassing time is 10-30 minutes, and the curing time is 2-6 hours.

[0024] In the above detection method, further, in the step 5), the plasma treatment time is 0.5-5 min, the power is 50-255 W, and the oxygen amount is 2-6 sccm.

[0025] In the above detection method, further, in the step 6), the concentration of the organophosphorus pesticide solution is 1-50 μg / mL, and the amounts of the absorbed liquid crystal, deionized water and organophosphorus pesticide solution are 2-6 μL, 4-12 μL and 2-6 μL respectively.

[0026] The present invention provides application of the aforementioned microfluidic liquid crystal sensor in the detection of organophosphorus pesticides.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention successfully combines a microfluidic device with liquid crystal for the detection of organophosphorus pesticides, and can detect organophosphorus pesticides in real time and quickly, with low sample consumption and no need for additional processing, thus solving the problem of complex operation of existing detection methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of liquid crystal microfluidic device for detecting organophosphorus pesticides

[0030] Figure 2 Optical photos of liquid crystals in microfluidic devices of different sizes modified with 20 mM Al(ClO4)3

[0031] Figure 3 The test result photo of Example 2

[0032] Figure 4 The test result photo of Example 3 DETAILED DESCRIPTION

[0033] The processing technology of the present invention is further described below in conjunction with specific embodiments.

[0034] Example 1

[0035] 1) Cut the slides into the required size, soak them in the prepared decon-90 solution, then wash them with ultrapure water, blow dry them with N2, dry them thoroughly, and keep them dust-free for later use;

[0036] 2) immersing the glass slide pretreated in step 1) in the TESPSA solution at 80° C., rinsing with ultrapure water, blowing dry with N2, fully drying, and dustproofing for standby use;

[0037] 3) Take 20mM Al(ClO4)3 anhydrous ethanol solution and add it dropwise to the center of the glass slide surface treated with carboxyl groups in step 2), spin-coat Al(ClO4)3 on the glass slide according to the set spin-coating parameters, dry it, and keep it dust-free for later use.

[0038] 4) Mix the polydimethylsiloxane (PDMS) prepolymer main agent and the curing agent in a ratio of 10:1 (w / w), stir and degas, transfer the degassed mixture to the silicon master, degas again, and cure in an oven at 80°C. Cut and punch the microchannel, clean it in isopropanol, and then dry it.

[0039] 5) Combining the glass slide obtained in step 3) with the PDMS microchannel obtained in step 4) after plasma treatment to form the desired microfluidic device.

[0040] 6) Use a syringe to absorb the liquid crystal, deionized water and glyphosate pesticide solution respectively, and then inject them into the device assembled in step 5) along the holes in sequence, leaving them for 30 minutes respectively. After the deionized water is injected, the deionized water will wash away the excess pesticide. After the liquid crystal is injected, the liquid crystal will squeeze out the deionized water, and finally only the liquid crystal will be left in the channel for observation.

[0041] Because the liquid crystal in the microchannel contacts the channel walls of four different length scales instead of the two surfaces of the liquid crystal pool, its orientation depends not only on its surface function but also on the geometric dimensions of the microchannel, so its dimensions must be optimized first. Four microchannels of different sizes were selected, with heights of 20μm and 50μm and widths of 200μm and 500μm, respectively. The specific parameters and results are shown in Figure 2. Figure 2 As shown, on a substrate modified with 20 mM aluminum perchlorate, its induction effect on a microchannel with a height of 20 μm is obvious, while its induction effect on a microchannel with a height of 50 μm is poor, so a microchannel with a height of 20 μm is used as the preferred microchannel design for the detection device.

[0042] Example 2

[0043] 1) Cut the slides into the required size, soak them in the prepared decon-90 solution, then wash them with ultrapure water, blow dry them with N2, dry them thoroughly, and keep them dust-free for later use;

[0044] 2) immersing the glass slide pretreated in step 1) in the TESPSA solution at 80° C., rinsing with ultrapure water, blowing dry with N2, fully drying, and dustproofing for standby use;

[0045] 3) Take 8-10mM Al(ClO4)3 anhydrous ethanol solution and add it dropwise to the center of the glass slide surface treated with carboxyl groups in step 2), spin-coat the Al(ClO4)3 ethanol solution on the glass slide according to the set spin-coating parameters, dry it, and keep it dust-free for later use.

[0046] 4) Mix the polydimethylsiloxane (PDMS) prepolymer main agent and the curing agent in a ratio of 10:1 (w / w), stir and degas, transfer the degassed mixture to the silicon master, degas again, and cure in an oven at 80°C. Cut and punch the microchannel, clean it in isopropanol, and then dry it.

[0047] 5) Combining the glass slide obtained in step 3) with the PDMS microchannel obtained in step 4) after plasma treatment to form the desired microfluidic device.

[0048] 6) Use a syringe to absorb liquid crystal, deionized water and glyphosate pesticide respectively, and then inject them into the device assembled in step 5) along the punched holes in sequence, leaving them for 30 minutes respectively. After deionized water is injected, the deionized water will wash away the excess glyphosate pesticide. After liquid crystal is injected, the liquid crystal will squeeze out the deionized water, and finally only the liquid crystal will be left in the channel for observation.

[0049] Figure 1 This is a schematic diagram of the liquid crystal microfluidic device for detecting organophosphorus pesticides. The specific test results are as follows: Figure 3 As shown in the figure, the microchannel with a height of 20μm has different induction abilities of aluminum perchlorate on liquid crystals at different widths, and the detection effects on pesticides are also different. Among them, the 500μm wide channel performs better when spin-coated with 8mM Al(ClO4)3 ethanol solution, and can detect glyphosate with a detection limit of 20μg / mL.

[0050] Example 3

[0051] 1) Cut the slides into the required size, soak them in the prepared decon-90 solution, then wash them with ultrapure water, blow dry them with N2, dry them thoroughly, and keep them dust-free for later use;

[0052] 2) immersing the glass slide pretreated in step 1) in the TESPSA solution at 80° C., rinsing with ultrapure water, blowing dry with N2, fully drying, and dustproofing for standby use;

[0053] 3) Take 8mM Al(ClO4)3 anhydrous ethanol solution and add it dropwise to the center of the glass slide surface treated with carboxyl groups in step 2), spin-coat the Al(ClO4)3 ethanol solution on the glass slide according to the set spin-coating parameters, dry it, and keep it dust-free for later use.

[0054] 4) Mix the polydimethylsiloxane (PDMS) prepolymer main agent and the curing agent in a ratio of 10:1 (w / w), stir and degas, transfer the degassed mixture to the silicon master, degas again, and cure in an oven at 80°C. Cut and punch the microchannel, clean it in isopropanol, and then dry it.

[0055] 5) Combining the glass slide obtained in step 3) with the PDMS microchannel obtained in step 4) after plasma treatment to form the desired microfluidic device.

[0056] 6) Use a syringe to absorb the liquid crystal, deionized water and malathion pesticide solution respectively, and then inject them into the device assembled in step 5) along the holes in sequence, leaving them for 30 minutes. After the deionized water is injected, the deionized water will wash away the excess malathion pesticide. After the liquid crystal is injected, the liquid crystal will squeeze out the deionized water, and finally only the liquid crystal will be left in the channel for observation.

[0057] Specific test results such as Figure 4 As shown, the present invention has a good detection effect on malathion and can detect malathion with a detection limit of 1 μg / mL.

[0058] For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention should still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A detection method of a microfluidic liquid crystal sensor for detecting organophosphorus pesticides, characterized in that: The liquid crystal sensor is assembled by loading a PDMS microchannel on a glass slide fixed with metal perchlorate; the organophosphorus pesticide and liquid crystal are injected into the microchannel; The microchannel has a height of 10-20 μm and a width of 200-500 μm; the metal perchlorate is Al(ClO4)3; The following steps are involved: 1) Pretreatment of slides Soak the cut glass slides in cleaning solution, clean and dry; 2) Carboxylation of slides 3) Fixing slides with metal perchlorates Add the metal perchlorate anhydrous ethanol solution dropwise to the center of the surface of the glass slide treated in step 2), spin-coat the metal perchlorate ethanol solution on the glass slide according to the set spin-coating parameters, dry it, and protect it from dust for later use; 4) Preparation and cleaning of PDMS microchannels The PDMS prepolymer main agent and the curing agent are mixed in a ratio of 10:1 (w / w), stirred and degassed, and the degassed mixture is transferred to the silicon master, degassed again, and cured in an oven at 80-110°C, and the microchannel is removed from the silicon template; after cutting and punching, a microchannel with hollow channels is formed, and the microchannel is cleaned in isopropanol, dried, and treated with a plasma process; The stirring time is 5-15 minutes, the degassing time is 10-30 minutes, and the curing time is 2-6 hours; 5) Assembly of microfluidic devices The glass slide obtained in step 3) is combined with the PDMS microchannel obtained in step 4) after plasma treatment to form the desired microfluidic device; 6) Assembly of microfluidic liquid crystal sensor Inject organophosphorus pesticide, deionized water and liquid crystal into the device assembled in step 5) along the punched holes, and keep each substance for 30 minutes; In the step 1), the glass slide is soaked in a 1%-10% (V / V) decon-90 aqueous solution for 2-12 hours, then the glass slide is cleaned with ultrapure water, blown dry with N2, and dust-proofed for standby use; in the step 2), the glass slide is carboxylated by soaking the glass slide pretreated in step 1) in a TESPSA solution at 60-100° C., rinsing with ultrapure water, blowing dry with N2, and dust-proofed for standby use; In step 3), the concentration of metal perchlorate is 8-20 mM; In the step 3), the spin coating parameters are set to 2000-6000 rpm, the spin coating time is 0.5-2 min, and the spin coating amount is 30-100 μL; In the step 5), the plasma treatment time is 0.5-5 min, the power is 50-255 W, and the oxygen amount is 2-6 sccm; In the step 6), the concentration of the organophosphorus pesticide solution is 1-50 μg / mL, and the amounts of the liquid crystal, deionized water and organophosphorus pesticide solution absorbed are 2-6 μL, 4-12 μL and 2-6 μL respectively.

2. The detection method of a microfluidic liquid crystal sensor for detecting organophosphorus pesticides according to claim 1, characterized in that: The volume fraction of the TESPSA solution is 0%-1%, excluding 0; and the immersion time is 2-8h.

3. Application of the detection method of the microfluidic liquid crystal sensor for detecting organophosphorus pesticides according to claim 1 in the detection of organophosphorus pesticides.

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