Chromatography-imitating miniature integrated electronic nose and application thereof

Abstract

The invention discloses a chromatography-imitating miniature integrated electronic nose and application thereof, and the electronic nose comprises a nut, a screw, a polytetrafluoroethylene joint, a stainless steel clamp, a polytetrafluoroethylene tube, an organic glass chamber formed by a laser direct writing technology, a laser-induced graphene (LIG) interdigital electrode sensor array and a rubber sealing ring. According to the invention, an interdigital electrode array which can be directly connected to a commercial FPC interface is engraved on a flexible polyimide film through a laser direct technology; the sensor array is composed of a single sensing material and PDMS coatings with different thicknesses, the sensor with high repeatability is manufactured by adopting a simple dispensing method, and the whole LIG transmission interdigital electrode sensor array is simple in manufacturing process and low in cost; the electronic nose is formed by simply assembling all parts, so that the electronic nose is convenient to disassemble, replace and produce in batches; the electronic nose is small in size, simple in wiring and capable of being used after being connected.

Description

Technical Field

[0001] The invention relates to the technical field of sensor equipment, and in particular to a chromatographically imitating micro-integrated electronic nose and applications thereof. Background Art

[0002] Volatile organic compounds (VOCs) can be used as markers for explosives, environmental pollution, food corruption, fruit ripening, plant pests and diseases, health diagnosis, etc. Therefore, the detection of VOCs has great application potential in the fields of environmental pollution, agriculture, public safety, food, health monitoring and disease diagnosis. At present, most gas sensors are selective sensors based on metal oxides, which can only selectively detect a certain type or a certain type of gas, and generally lack accuracy and reliability for complex gas components in actual application scenarios. The electronic nose, a sensor system that mimics biological olfaction, has a sensor array composed of gas sensors with different chemical selectivities, which cross-respond to different gases to form a unique fingerprint spectrum. Combined with pattern recognition algorithms, it can detect and identify complex VOCs components. At present, the construction of such a sensor array often requires the design of complex and sufficient chemical diversity sensor elements to distinguish and identify various VOCs, resulting in high cost, large size, and complex manufacturing process of the electronic nose, which limits the application of the electronic nose in actual environments. Summary of the invention

[0003] The purpose of the present invention is to overcome the problems of high cost, large size and complex manufacturing process of electronic noses, and to provide a low-cost, simple manufacturing process, chromatographic-like micro-integrated electronic nose composed of a single gas-sensitive material conductive coating, and applied to the sensing of volatile gases.

[0004] The specific technical solution for achieving the purpose of the present invention is:

[0005] A chromatographic micro-integrated electronic nose, comprising a polytetrafluoroethylene (PTFE) tube, nuts and screws, a metal threaded fixture, a polytetrafluoroethylene tube adapter, a top chamber, a rubber sealing ring, a LIG interdigital electrode sensor array and a bottom chamber;

[0006] The LIG interdigital electrode sensor array is composed of a flexible polyimide (PI) film, grooves formed by laser etching on the PI film, a laser-induced graphene (LIG) interdigital electrode array circuit engraved by laser on the PI film, a gas-sensitive material conductive coating coated on the interdigital electrode area, and a polydimethylsiloxane (PDMS) coating with a thickness gradient covering the gas-sensitive sensing material;

[0007] The top chamber is a rectangular thin organic glass plate, on the surface of which 4 to 6 screw holes, air inlet holes and air outlet holes are symmetrically cut, and a streamlined shallow groove is carved;

[0008] The bottom chamber is a rectangular thin organic glass plate of the same size as the top chamber, and 4 to 6 through screw holes corresponding to the top chamber are symmetrically cut on its surface;

[0009] The rubber sealing ring is a rectangular rubber film with the same size as the top chamber, on which a portion with the same shape as the streamlined groove and 4 to 6 screw holes corresponding to the top chamber are cut out by laser;

[0010] Stack the top chamber, rubber seal, LIG ​​interdigital electrode sensor array, and bottom chamber from top to bottom, with their screw holes aligned one by one;

[0011] The screws are inserted from the two through screw holes on one side of the top chamber air outlet, and then tightened with nuts; the metal threaded clamp clamps the entire chamber fixed by screws and nuts from the top chamber air inlet side, and the center of the threaded hole of the metal threaded clamp is aligned with the center of the top chamber air inlet; then the polytetrafluoroethylene tube adapter connected to the polytetrafluoroethylene tube is connected to the metal threaded clamp and tightened; the air outlet of the polytetrafluoroethylene tube is aligned with the air inlet of the top chamber and inserted.

[0012] Furthermore, the preparation of the LIG interdigital electrode sensor array includes:

[0013] Step 1: Use a laser to carve a rectangular LIG pattern on a flexible polyimide (PI) film with a length of 4-10 cm, a width of 4-10 cm, and a thickness of 0.2-0.3 mm, and then use a mechanical method to remove the rectangular LIG to leave a rectangular groove, that is, the groove formed by laser etching on the PI film is obtained;

[0014] Step 2: Use a laser to engrave a LIG interdigital electrode array circuit on a flexible polyimide (PI) film with grooves, and the interdigital electrode area is located in the center of the grooves formed by laser etching, thus obtaining a LIG interdigital electrode array circuit;

[0015] Step 3: Apply gas-sensitive sensing material to the groove formed by laser etching;

[0016] Step 4: Apply a PDMS toluene solution with a concentration gradient to the grooves formed by laser etching and cover the surface of the gas-sensitive sensing material. Apply 2 to 3 sensors with each concentration of PDMS toluene solution. Then heat the sensor array with the PDMS solution in an oven at 80 to 100°C for 3 to 4 hours to solidify the PDMS. PDMS toluene solutions of different concentrations will form PDMS coatings of different thicknesses on the sensor surface as a stationary phase, thus obtaining a LIG interdigitated electrode sensor array.

[0017] Further, the preparation of the top chamber includes:

[0018] Step 1: Select a rectangular plexiglass plate with a length of 4~10cm, a width of 4~10cm, and a thickness of 1~3mm, and use a laser to carve a streamlined shallow groove on one side of the rectangular plexiglass plate;

[0019] Step 2: Use a laser to cut 4 to 6 through screw holes and through air inlet and outlet holes with a diameter of 1 mm to 3 mm on the organic glass plate engraved with streamlined shallow grooves, and cut the rectangular organic glass plate into a rectangle with a length of 3 to 5 cm and a width of 1 to 5 cm to obtain the top chamber.

[0020] Further, the preparation of the bottom chamber includes:

[0021] A rectangular plexiglass plate with a length of 4 to 10 cm, a width of 4 to 10 cm, and a thickness of 1 to 3 mm is selected, 4 to 6 through screw holes are cut in the rectangular plexiglass plate using a laser, and the rectangular plexiglass plate is cut into the size of the top chamber, thereby obtaining the bottom chamber.

[0022] An application of the above-mentioned chromatographic-like micro-integrated electronic nose in volatile gas sensing.

[0023] The advantages of the chromatographic-like micro-integrated electronic nose of the present invention are as follows: 1) the cavity as a whole is composed of various parts and components, which can be disassembled and replaced; 2) the LIG interdigital electrode sensor array can be directly connected to a commercial FPC adapter without welding, and is convenient for integration into a circuit board to collect signals; 3) the LIG interdigital electrode sensor array, chamber and rubber sealing ring are simple to manufacture and low in cost, and can be completed by laser engraving and cutting, without the need for other instruments and steps. The sensor can be manufactured by a simple drop coating method, and the manufacturing process is simple and efficient, and the cost of the raw materials used above is low; 4) grooves are engraved in the LIG interdigital electrodes, which can ensure that the sensing material remains consistent during the drop coating process, simplify the sensor array manufacturing process, and improve the repeatability of sensor manufacturing; 5) the LIG interdigital electrode sensor array uses only one gas-sensitive material and PDMS coatings of different thicknesses, and can realize the detection and identification of various VOCs, eliminating the need for complexly designed sensing elements with diverse chemical selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The figure is a flow chart of the preparation of the LIG interdigitated electrode sensor array of the present invention;

[0025] Figure 2 is a front schematic diagram of the top chamber of the present invention;

[0026] Figure 3 is a schematic diagram of the back side of the top chamber of the present invention;

[0027] Figure 4It is a schematic diagram of the rubber sealing ring of the present invention;

[0028] Figure 5 is a schematic diagram of the bottom chamber of the present invention;

[0029] Figure 6 A structural diagram of a micro-integrated electronic nose of the present invention;

[0030] Figure 7 A physical picture of the micro-integrated electronic nose of the present invention;

[0031] Figure 8 This is the PCA diagram of the micro-integrated electronic nose of the present invention for identifying 13 VOCs. DETAILED DESCRIPTION

[0032] The following is a complete, clear and detailed description of the technical solutions of the embodiments of the present invention in combination with the accompanying drawings and specific implementation methods. The described embodiments are partial embodiments of the present invention, rather than all embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] See also Figure 1-5 The present invention discloses a chromatography-like micro-integrated electronic nose comprising: a polytetrafluoroethylene (PTFE) tube 1, a nut 9 and a screw 4, a metal threaded clamp 3, a polytetrafluoroethylene tube adapter 2, a top chamber 5, a rubber gasket 6, a LIG interdigital electrode sensor array 7, and a bottom chamber 8.

[0034] The LIG interdigital electrode sensor array 7 includes a flexible polyimide (PI) film 15, grooves 17 formed by laser etching on the PI film, a laser induced graphene (LIG) interdigital electrode array circuit 18 engraved by laser on the PI film, a gas-sensitive sensing material 19 coated on the interdigital electrode area, and a polydimethylsiloxane (PDMS) coating 20 of different thicknesses covering the gas-sensitive sensing material 19.

[0035] The top chamber 5 is a rectangular thin organic glass plate with 4 to 6 through screw holes 12, air inlet holes 10 and air outlet holes 11 cut on any one side, and a streamlined shallow groove 13 engraved at the same time.

[0036] The bottom chamber 8 is a rectangular thin organic glass plate with 4 to 6 screw holes cut on any one side.

[0037] The rubber sealing ring 6 is a rectangular rubber film, which is cut by laser to remove a portion with the same shape as the streamlined groove 13 and four screw holes corresponding to the top chamber.

[0038] The top chamber 5, rubber sealing ring 6, LIG ​​interdigital electrode sensor array 7, and bottom chamber 8 are stacked from top to bottom, and their four screw holes 12 are aligned one by one. Two screws 4 are inserted from the two through screw holes 12 on one side of the top chamber air outlet 10, and then tightened with nuts 9. The metal threaded clamp 3 clamps the entire chamber fixed by screws 4 from the side of the top chamber air inlet, and the center of the threaded hole of the metal threaded clamp 3 is aligned with the center of the top chamber air inlet 10. Then, the polytetrafluoroethylene tube adapter 2 connected to the polytetrafluoroethylene tube 1 is connected to the metal threaded clamp 3 and tightened. The air outlet of the polytetrafluoroethylene tube 1 is aligned with the air inlet 10 of the top chamber and inserted.

[0039] Example 1: Preparation of LIG interdigitated electrode sensor array, see Figure 1 ;

[0040] 1.1: Cut a piece of PI film 15 of about 4 cm*4 cm in size and fix it on a glass plate with double-sided tape. First, use a CO2 laser 14 to engrave a rectangular groove pattern 16 on the PI film, using 50% power and an engraving speed of 150 mm / s and 30% power and an engraving speed of 150 mm / s respectively. Then, use a mechanical method (such as scraping with tweezers) to remove the loose LIG formed by the engraving, rinse with water to completely remove the LIG powder on the surface, leaving the groove 17 pattern, that is, the groove 17 on the LIG interdigital electrode array is engraved.

[0041] 1.2: Then, the PI film 15 with grooves engraved thereon is placed back into the original position of the laser engraving machine 14, and the interdigital electrode array circuit 18 is engraved at a power of 20% and an engraving speed of 200 mm / s, and screw holes and a rectangular cavity shape of 3.35 cm*1.85 cm are cut out, thereby obtaining the LIG interdigital electrode array circuit 18.

[0042] 1.3: Then use a pipette to take 2 µL of gas-sensitive conductive ink and apply it to each groove 17. After vacuum drying for 30 minutes at room temperature, the gas-sensitive sensing material 19 can be obtained. Then prepare PDMS toluene solutions of different concentrations. Add 4 ml of toluene and 0.4 g of curing agent to 4 g of PDMS to prepare PDMS stock solution. Dilute part of the stock solution with toluene to 0.2, 0.3, 0.4, and 0.5 times the original concentration. Then take 2 µL of these solutions and apply them to different grooves (the order of applying is as follows: Figure 1As shown, from left to right, the two sensors in the first column of electrodes are not dripped with PDMS, the two sensors in the second column are dripped with PDMS toluene solution with a concentration of 0.2 times the original solution, the two sensors in the third column are dripped with PDMS toluene solution with a concentration of 0.3 times the original solution, the two sensors in the fourth column are dripped with PDMS toluene solution with a concentration of 0.4 times the original solution, and the two sensors in the fifth column are dripped with PDMS toluene solution with a concentration of 0.5 times the original solution), and then cured in an oven at 80°C for 3 h to form PDMS coatings 20 of different thicknesses on different sensors, thereby obtaining a LIG interdigital electrode sensor array 7.

[0043] Example 2: Preparation of the top chamber 5, rubber sealing ring 6, and bottom chamber 8, see Figure 2-Figure 5 ;

[0044] 2.1: Take a 20cm*20cm plexiglass plate with a thickness of 2mm, and then use a CO2 laser 16 to carve a streamlined shallow groove 13 on one side of the plexiglass plate at a power of 50% and an engraving speed of 200mm / s.

[0045] 2.2: Then, a CO2 laser 16 is used to cut four through holes with a diameter of 4 mm as screw holes 15 and two through holes with a diameter of 2 mm as air inlet holes 10 and air outlet holes 11 on the organic glass plate 15 engraved with the streamlined groove 13 at 70% power and a cutting speed of 50 mm / s. Finally, a rectangular shape of 3.35 cm*1.85 cm of the top chamber 5 is cut at the same power and cutting speed. That is, the top chamber 5 is obtained.

[0046] 2.3: Take a piece of silicone film with a thickness of 0.2mm and a size of 10cm*10cm, and use a CO2 laser 14 with a power of 30% and a cutting speed of 200mm / s to cut a pattern identical to the streamlined groove 13 and four through holes with a diameter of 4mm as screw holes on the silicone film, thereby obtaining a rubber sealing ring 6.

[0047] 2.4: Take a 20cm*20cm plexiglass plate with a thickness of 2mm, and then use a CO2 laser 14 to cut four 4mm diameter through holes as screw holes and a 3.35cm*1.85cm rectangular shape of the chamber at 70% power and a cutting speed of 50mm / s, thereby obtaining the bottom chamber 8.

[0048] Example 3: Assembly of a micro-integrated electronic nose, see Figure 6-Figure 7 ;

[0049] The top chamber 5, rubber sealing ring 6, LIG ​​interdigital electrode sensor array 7, and bottom chamber 8 are stacked from top to bottom, and their four screw holes 12 are aligned one by one. Two M4 screws 4 are inserted from the two through screw holes 12 on one side of the top chamber air outlet 10, and then tightened and fixed with M4 screws 4 and nuts 9. The metal threaded clamp 3 clamps the entire chamber fixed by screws 4 from one side of the top chamber air inlet 10, and the center of the threaded hole of the metal threaded clamp 3 is aligned with the center of the top chamber air inlet 10. Then, the polytetrafluoroethylene tube adapter 2 connected to the polytetrafluoroethylene tube 1 is connected to the metal threaded clamp 3 and tightened. The air outlet of the polytetrafluoroethylene tube is aligned with the air inlet of the top chamber and inserted. The assembly of the micro-integrated electronic nose is completed.

[0050] Example 4: Application of micro-integrated electronic nose in volatile gas sensing, see Figure 8 ;

[0051] 4.1: First, connect the polytetrafluoroethylene tube 1 used for air intake to the N2 gas flow, flush the sensor array in the chamber with a flow rate of 1000sccm to stabilize the baseline of the sensor, and then expose the sensor array to 13 VOCs at a concentration of 10ppm for 3min. Use a multi-channel desktop multimeter to test the resistance change of each sensor (a total of 10) in the micro-integrated electronic nose, and finally pass N2 to flush the sensor array to flush the previously introduced VOCs.

[0052] 4.2: The resistance change rate of the micro-integrated electronic nose composed of 10 sensor units in response to 13 VOCs is extracted as the characteristic value, and the obtained characteristic values ​​are used to identify the 13 VOCs through the principal component analysis (PCA) method. The micro-integrated electronic nose can recognize and distinguish 13 VOCs and has high-performance volatile gas sensing capabilities.

Claims

1. A chromatographic micro-integrated electronic nose, characterized in that: The electronic nose comprises a polytetrafluoroethylene (PTFE) tube (1), a nut (9) and a screw (4), a metal threaded clamp (3), a polytetrafluoroethylene tube adapter (2), a top chamber (5), a rubber sealing ring (6), a LIG interdigital electrode sensor array (7), and a bottom chamber (8); The LIG interdigital electrode sensor array (7) is composed of a flexible polyimide (PI) film (15), grooves (17) formed by laser etching on the PI film, a laser induced graphene (LIG) interdigital electrode array circuit (18) engraved on the PI film by laser, a gas sensing material (19) coated on the interdigital electrode region, and a polydimethylsiloxane (PDMS) coating (20) with a thickness gradient covering the gas sensing material (19); The top chamber (5) is a rectangular thin organic glass plate (15), on the surface of which 4 to 6 through screw holes (12) and air inlet holes (10) and air outlet holes (11) are symmetrically cut, and a streamlined shallow groove (13) is carved; The bottom chamber (8) is a rectangular thin organic glass plate of the same size as the top chamber (5), and has 4 to 6 through screw holes corresponding to the top chamber symmetrically cut on its surface; The rubber sealing ring (6) is a rectangular rubber film of the same size as the top chamber (5), from which a portion having the same shape as the streamlined groove (13) and screw holes 4 to 6 corresponding to the top chamber are cut out by laser; The top chamber (5), the rubber sealing ring (6), the LIG interdigital electrode sensor array (7), and the bottom chamber (8) are stacked in sequence from top to bottom, and the screw holes thereof are aligned one by one; The screws (4) are inserted into two through screw holes (12) on one side of the air outlet (11) of the top chamber (5) and then tightened and fixed with nuts (9); the metal threaded clamp (3) clamps the entire chamber fixed by the screws (4) and nuts (9) from one side of the air inlet (10) of the top chamber, and the center of the threaded hole of the metal threaded clamp (3) is aligned with the center of the air inlet (10) of the top chamber; then the polytetrafluoroethylene tube adapter (2) connected to the polytetrafluoroethylene tube (1) is connected to the metal threaded clamp (3) and tightened and fixed; wherein the air outlet of the polytetrafluoroethylene tube (1) is aligned with the air inlet (10) of the top chamber and inserted.

2. The chromatographic micro-integrated electronic nose according to claim 1, characterized in that: The preparation of the LIG interdigital electrode sensor array (7) comprises: Step 1: using a laser (14) to engrave a rectangular LIG pattern (16) on a flexible polyimide (PI) film (15) having a length of 4-10 cm, a width of 4-10 cm, and a thickness of 0.2-0.3 mm, and then mechanically removing the rectangular LIG to leave a rectangular groove, thereby obtaining a groove (17) formed on the PI film by laser etching; Step 2: using a laser (14) to carve a LIG interdigital electrode array circuit (18) on a flexible polyimide (PI) film (15) having a groove (17) engraved thereon, wherein the interdigital electrode region is located in the center of the groove (17) formed by laser etching, thereby obtaining a LIG interdigital electrode array circuit (18); Step 3: applying a gas-sensitive sensing material (19) to the groove (17) formed by laser etching; Step 4: A PDMS toluene solution with a concentration gradient is dripped into the groove (17) formed by laser etching, and covered on the surface of the gas-sensitive sensing material (19). 2 to 3 sensors are dripped with each concentration of PDMS toluene solution, and then the sensor array dripped with the PDMS solution is heated in an oven at 80 to 100° C. for 3 to 4 hours to solidify the PDMS. PDMS toluene solutions of different concentrations will form PDMS coatings (20) of different thicknesses on the sensor surface as a stationary phase, thereby obtaining a LIG interdigitated electrode sensor array (7).

3. The chromatographic micro-integrated electronic nose according to claim 1, characterized in that: The preparation of the top chamber (5) comprises: Step 1: Select a rectangular organic glass plate with a length of 4-10 cm, a width of 4-10 cm, and a thickness of 1-3 mm, and use a laser (14) to carve a streamlined shallow groove (13) on one side of the rectangular organic glass plate; Step 2: Use a laser (14) to cut 4 to 6 through screw holes (12) and through air inlet holes (10) and air outlet holes (11) with a diameter of 1 mm to 3 mm on the organic glass plate engraved with streamlined shallow grooves (13), and cut the rectangular organic glass plate into a rectangle with a length of 3 to 5 cm and a width of 1 to 5 cm, thereby obtaining a top chamber (5).

4. The chromatographic micro-integrated electronic nose according to claim 1, characterized in that: The preparation of the bottom chamber (8) comprises: A rectangular organic glass plate with a length of 4 to 10 cm, a width of 4 to 10 cm, and a thickness of 1 to 3 mm is selected, 4 to 6 through screw holes are cut in the rectangular organic glass plate using a laser (14), and the rectangular organic glass plate is cut into the size of the top chamber, thereby obtaining a bottom chamber (8).

5. An application of the chromatographic micro-integrated electronic nose according to claim 1 in volatile gas sensing.

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