Microcavity integrated electronic nose and application thereof in volatile gas sensing

Abstract

The application discloses a micro-cavity integrated electronic nose and application thereof in volatile gas sensing, and the micro-cavity integrated electronic nose comprises a screw with a gasket and a nut, a polytetrafluoroethylene joint, a stainless steel clamp, a polytetrafluoroethylene pipe, a chamber formed by laser direct writing technology, a laser-induced graphene interdigital electrode (LIGIE) sensing array, a bent needle and a rubber ring. The application can load various gas-sensitive materials on the interdigital electrode array prepared on the flexible polyimide film by laser direct technology; the micro-cavity integrated electronic nose does not need any glue bonding, the LIGIE sensing array is in contact with the chamber and is conductive without welding, each component part can be simply replaced, batch quantitative preparation is easy, and the volume is small and the electronic nose can be plugged and used.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sensing devices, in particular to a micro-cavity integrated electronic nose and its application in volatile gas sensing. BACKGROUND

[0002] Volatile organic compounds (VOCs) have wide application prospects in health detection, environmental monitoring, food safety and other fields. Traditional gas sensors mainly target selective detection of a certain type of gas ("lock-key" sensing). However, they lack high sensitivity, high selectivity and reliability in detecting multiple gases (such as VOCs) in complex environments. Electronic nose, a sensing system of an olfactory mimic system, is a sensing array composed of different sensing units. It can form a gas fingerprint by cross-response to multiple gases and achieve identification of VOCs in complex environments by combining with pattern recognition methods. Most of the current electronic nose systems have the disadvantages of large size, high cost, difficult preparation technology and inconvenience for carrying, which limits their wide application in volatile gas sensing due to poor expandability. SUMMARY

[0003] The present application aims to overcome the disadvantages of traditional electronic nose, such as large size, high cost, difficult preparation technology and inconvenience for carrying, and to provide a low-cost and simple-to-prepare micro-cavity integrated electronic nose and its application in volatile gas sensing.

[0004] The specific technical solution to achieve the purpose of the present application is as follows:

[0005] A micro-cavity integrated electronic nose, characterized in that the micro-cavity integrated electronic nose comprises a screw with a gasket and a nut, a polytetrafluoroethylene joint comprising a polytetrafluoroethylene tube, a stainless steel clamp, a top chamber, a bottom chamber, an LIGIE sensing array and a rubber ring, wherein the LIGIE sensing array comprises a flexible polyimide film, an interdigital electrode (flexible LIGIE) composed of interdigital electrodes engraved on the film and lead wires, and an LIGIE silver conductive area formed by coating conductive silver paste at the lead wire position of the flexible LIGIE;

[0006] The bottom chamber is a piece of organic glass plate, one side of which is pasted with kraft paper, and the organic glass plate on the side of the kraft paper is cut with the same number of through-welding holes as the lead wires of the LIGIE sensing array, the same number of non-through I-shaped patterns as the lead wires, and 4-6 through-screw holes, and is engraved with a streamlined groove; a bent needle is inserted into the through-welding hole to form a connection circuit;

[0007] The top chamber is a piece of organic glass plate, and a through-screw hole is cut on one side of the organic glass plate, the number and size of which correspond to the through-screw holes of the bottom chamber, and a plurality of through-gas holes and a plurality of through-recessed openings are cut.

[0008] The LIGIE sensor array is covered on the upper surface of the bottom chamber, wherein the silver conductive area in the LIGIE sensor array is in contact with the connecting circuit of the bottom chamber to form a contact circuit connection; and the rubber ring is covered on the upper surface of the LIGIE sensor array.

[0009] The top chamber is covered on the rubber ring, wherein the through screw holes of the top chamber and the through screw holes of the bottom chamber correspond to each other in the vertical direction.

[0010] The screw with a gasket and a nut is screwed into the aligned through screw holes to form a tightly fitted microcavity; the tightly fitted microcavity is placed in a stainless steel clamp, and a polytetrafluoroethylene joint containing a polytetrafluoroethylene tube is placed in the stainless steel clamp and tightened, wherein the joint of the polytetrafluoroethylene joint corresponds to the through gas hole of the top chamber, and is used for directional guiding of gas in and out.

[0011] The LIGIE sensor array is prepared by the following process:

[0012] Step 1: Preparation of flexible LIGIE, using a laser to engrave interdigital electrodes including interdigital electrodes and leads on a flexible polyimide film, i.e. flexible LIGIE;

[0013] Step 2: Attach a PET tape as a mask plate to the flexible LIGIE, use a doctor blade to coat the conductive silver paste, after heating at 60~90 ℃ for 2~4 h, remove the PET tape, and the conductive silver paste is fixed at the lead position of the LIGIE, i.e. the silver conductive area of the LIGIE;

[0014] Step 3: Laser cutting of the PI tape, the size of the cut PI tape matches the flexible LIGIE, and the interdigital area of the PI tape corresponding to the flexible LIGIE is removed; vertically align the PI tape and attach it to the flexible LIGIE, and finally drop the gas sensitive material in the interdigital area; i.e. the LIGIE sensor array is prepared.

[0015] The bottom chamber is prepared by the following process:

[0016] Step 1: Select a piece of organic glass plate with a length of 8~20 cm, a width of 8~20 cm and a thickness of 2~4 mm, and optionally the largest area of the surface as the front surface, and attach a kraft paper;

[0017] Step 2: using a laser to cut through the organic glass plate containing the kraft paper side to cut out the same number of lead wires as the LIGIE sensor array, a diameter of 0.8 mm ~ 1 mm through the welding hole, the same number of lead wires as the LIGIE sensor array, a non-through I type pattern and 4~6 through screw holes with a diameter of 3 mm~4 mm; at the same time, using a laser to engrave a streamlined groove in the organic glass plate containing the kraft paper side;

[0018] Step 3: remove the kraft paper corresponding to the I type pattern area, use a scraper to scrape the conductive silver paste in the I type pattern area; at the same time, insert the corresponding number of bent needles into the through welding hole; heat the organic glass plate to 60 ℃~90 ℃ for 2~4 h to obtain a circuit for connecting the LIGIE sensor array and the bent needle; finally, remove all the kraft paper to form a bottom chamber.

[0019] The preparation process of the top chamber comprises:

[0020] Select another organic glass plate with a length of 8~20 cm, a width of 8~20 cm and a thickness of 2~4 mm, optionally the largest area of which is used as the front surface, and use a laser to cut through the screw hole on the surface, the number and size of which correspond to the through screw hole prepared in the bottom chamber; cut several through air holes with a diameter of 2mm~3 mm and several through concave openings.

[0021] An application of the microcavity integrated electronic nose in volatile gas sensing.

[0022] The microcavity integrated electronic nose has the following advantages: 1) the gas inlet and outlet interfaces introduced by the polytetrafluoroethylene tube are connected by a stainless steel clamp and a polytetrafluoroethylene joint, without the need for any glue to assist in fixing, which meets the needs of disassembly and replacement at any time; 2) the circuit connection mode of the LIGIE sensor array and the bottom chamber is a contact connection under the assistance of a silicone rubber ring, which forms a conductive loop without the need for high-temperature welding, facilitating the replacement of the LIGIE sensor array and the reuse of the chamber, and providing more opportunities for the study of the performance of various gas-sensitive materials; 3) the LIGIE sensor array, the chamber and the rubber ring can be adjusted by adjusting the power and function of the laser during the whole process, without the need for traditional PCB board, and the process is simple, batchable, and low in raw material cost. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The preparation flowchart of the LIGIE sensor array of the application;

[0024] Figure 2 The preparation flowchart of the bottom chamber of the application;

[0025] Figure 3A schematic diagram of the top chamber of the present application;

[0026] Figure 4 An exploded view of the microcavity integrated electronic nose of the present application;

[0027] Figure 5 A perspective view of the microcavity integrated electronic nose of the present application;

[0028] Figure 6 PCA plot of the microcavity integrated electronic nose of the present application for the identification of 13 VOCs. DETAILED DESCRIPTION

[0029] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the described embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the protection scope of the present application.

[0030] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and the values are approximate values and should be understood as including values approximately near these ranges and values within these ranges. For ranges of values, the endpoints of the ranges are included in the ranges, and the endpoints and the individual points within the ranges are combinable to form new ranges, which are also within the scope of the present application.

[0031] Unless otherwise defined, technical terms or scientific terms used in the present disclosure shall have the ordinary meaning commonly understood by one of ordinary skill in the art to which the present application pertains.

[0032] Referring to Figures 1-5 The microcavity integrated electronic nose of the present application comprises a screw 3 with a gasket 4 and a nut 11, a PTFE joint 2, a stainless steel clamp 8, a PTFE tube 1, a top chamber 5, a bottom chamber 9, an LIGIE sensor array 7 and a rubber ring 6, wherein the LIGIE sensor array 7 comprises a flexible polyimide film 12, interdigital electrodes, i.e. flexible LIGIE, composed of interdigital electrodes 13 engraved on the film and lead wires 14, and LIGIE silver conductive areas 18 formed by coating conductive silver paste at the lead wire positions of the flexible LIGIE.

[0033] The bottom chamber 9 is a piece of organic glass plate 22, one side is pasted with kraft paper 23, the organic glass plate on the kraft paper side is cut with the same number of through welding holes 25 as the lead 14 of the LIGIE sensing array 7, the same number of non-through I-shaped patterns 24 as the lead 14, and 4-6 through screw holes 26, and a streamlined groove 27 is engraved at the same time; the bent needle 10 is inserted into the through welding hole 25 to form a connecting circuit 28;

[0034] The top chamber 5 is a piece of organic glass plate, and the through screw hole 29 is cut on one side, the number and size of which correspond to the through screw hole 26 of the bottom chamber 9, and a plurality of through air holes 30 and a plurality of through concave mouths 31 are cut;

[0035] The LIGIE sensing array 7 is covered on the upper surface of the bottom chamber 9, wherein the silver conductive area 18 in the LIGIE sensing array 7 is attached to the connecting circuit 28 of the bottom chamber 9 to form a contact circuit connection; the rubber ring 6 is covered on the upper surface of the LIGIE sensing array 7;

[0036] The top chamber 5 is covered on the rubber ring 6, wherein the through screw hole 29 of the top chamber 5 corresponds to the through screw hole 26 of the bottom chamber 9 in the vertical direction one by one;

[0037] The screw 3 with gasket and nut is inserted into the aligned through screw hole and tightened to form a tightly fitted microcavity; the tightly fitted microcavity is placed in the stainless steel clamp 8, the polytetrafluoroethylene joint 2 of the polytetrafluoroethylene tube 1 is placed in the stainless steel clamp 8 and tightened, wherein the joint of the polytetrafluoroethylene joint 2 corresponds to the through air hole 30 of the top chamber 5, which is a directional guide for gas in and out.

[0038] Example 1: Preparation of LIGIE sensing array, see Figure 1 ;

[0039] 1.1: Using a CO2 laser 21, adjust its power to 3.5 W, and the scanning speed is 150 mm / s, 8 graphene electrodes are manufactured on a polyimide film 12 with a size of 25 mm * 18 mm * 1 mm, each electrode has two leads 14 and 4 pairs of interdigital electrodes, wherein the interdigital electrode width is 200 μm, and the spacing is 200 μm; that is, a flexible LIGIE;

[0040] 1.2: Use PET tape (thickness 80 μm) as a mask plate attached to the flexible LIGIE, use a doctor blade 16 to coat conductive silver paste 17, after heating at 80℃ for 2 h, remove the PET tape 15, and the conductive silver paste is fixed at the lead position of the LIGIE, that is, the LIGIE silver conductive area 18;

[0041] 1.3: Laser cutting of PI tape (thickness 55 μm), the size of the cut PI tape 19 matches the flexible LIGIE, and the PI tape 19 corresponding to the interdigital 13 area of the flexible LIGIE is removed; the tape is vertically aligned and attached to the flexible LIGIE, and finally 8 different performance gas sensitive materials 20 are dropped on the 8 interdigital areas respectively to prepare a LIGIE sensor array 7 containing 8 sensing units.

[0042] Example 2: Preparation of bottom chamber and top chamber, see Figure 2 and Figure 3 ;

[0043] 2.1: Select a piece of organic glass plate 22 with a length of 10 cm, a width of 10 cm and a thickness of 2 mm, and optionally the largest area of the surface as the front surface to paste the kraft paper 23 with a thickness of 80 μm;

[0044] 2.2: Use CO2 laser 21 to carve a streamlined groove 27 in the organic glass plate 22 containing the kraft paper 23 side; At the same time, cut out 16 through-welding holes 25 with a diameter of 0.8 mm, and each 8 holes as a group, two groups are divided into two sides of the streamlined groove 27; 16 non-through I-shaped patterns 24, each 8 as a group, two groups are divided into two sides of the streamlined groove 27; 4 through-screw holes 26 with a diameter of 4 mm;

[0045] 2.3: Remove the kraft paper corresponding to the I-shaped pattern 24 area, and use the doctor blade 16 to scrape the conductive silver paste 17 in the I-shaped pattern 24 area to obtain the circuit structure 28 of the I-shaped pattern; At the same time, insert the pin array 10 formed by 8 bent pins into the two groups of through-welding holes 25 respectively; Heat the organic glass plate to 80 ℃ for 2 h, and then remove all the kraft paper 23 to form the bottom chamber 9;

[0046] 2.4: Select another piece of organic glass plate with a length of 10 cm, a width of 10 cm and a thickness of 2 mm, and optionally the largest area of the surface as the front surface, and use the CO2 laser 21 to cut out 4 through-screw holes 29 with a diameter of 4 mm and two through-air holes 30 with a diameter of 3 mm on the surface; Two symmetrical through-recessed openings 31, forming the top chamber 5.

[0047] Example 3: Assembly of microcavity integrated electronic nose, see Figure 4 and Figure 5 ;

[0048] 3.1: Align the silver paste conductive area 18 of the LIGIE sensor array 7 in Example 1 with the circuit structure 28 of the I-shaped pattern 24 in the bottom chamber 9 in Example 2 one by one, and cover the LIGIE sensor array 7 on the upper surface of the bottom chamber 9;

[0049] 3.2: Cover the LIGIE sensor array 7 with the rubber ring 6 and align it vertically with the position of the streamlined groove 27 in the bottom chamber 9;

[0050] 3.3: Cover the rubber ring 6 with the top chamber 5 in Example 2, wherein the four through screw holes 29 in the top chamber 5 are aligned vertically with the four through screw holes 26 in the bottom chamber 9; four screws 3 with washers and nuts are respectively inserted into the four aligned through screw holes, and the screws are tightened to form a tightly fitting microcavity;

[0051] 3.4: The tightly fitting microcavity is placed in two stainless steel clamps 8, and the threaded holes of the two stainless steel clamps 8 are aligned with the two through air holes 30 respectively;

[0052] 3.5: Two PTFE connectors 2 with PTFE tubes 1 are screwed into the threaded holes of the stainless steel clamps 8 and connected to the through air holes 30. One end serves as the air inlet and the other end serves as the air outlet.

[0053] Example 4: Application of microcavity integrated electronic nose in volatile gas sensing, see [reference]. Figure 6 ;

[0054] 4.1: First, N2 is introduced into the microcavity integrated electronic nose cavity through one of the polytetrafluoroethylene tubes 1 for baseline stabilization. Then, 13 VOCs at a concentration of 25 ppm are introduced respectively. The resistance change of each sensing unit (a total of 8) in the microcavity integrated electronic nose before and after the introduction of each VOC is tested by a multi-channel benchtop multimeter. Finally, N2 is introduced to flush out the VOCs.

[0055] 4.2: The resistance change rate of the microcavity integrated electronic nose composed of 8 sensing units in response to 13 VOCs was extracted as a feature value. The obtained feature value was used to identify the 13 VOCs by principal component analysis (PCA). The microcavity integrated electronic nose can identify and distinguish 13 VOCs and has high-performance volatile gas sensing capability.

Claims

1. A microcavity integrated electronic nose, characterized in that, The microcavity integrated electronic nose comprises a screw (3) with a gasket (4) and a nut (11), a polytetrafluoroethylene joint (2) containing a polytetrafluoroethylene tube (1), a stainless steel clamp (8), a top cavity (5), a bottom cavity (9), an LIGIE sensor array (7), and a rubber ring (6), The LIGIE sensor array (7) comprises a flexible polyimide film (12), interdigital electrodes (13) engraved on the film, and lead wires (14), that is, a flexible LIGIE, and an LIGIE silver conductive area (18) formed by coating conductive silver paste at the position of the lead wire of the flexible LIGIE; The bottom cavity (9) is a piece of organic glass plate (22), one side of which is pasted with kraft paper (23), and the organic glass plate on the side of the kraft paper is cut to have the same number of through-welding holes (25) as the lead wires (14) of the LIGIE sensor array (7), the same number of non-through I-shaped patterns (24) as the lead wires (14), and 4-6 through-screw holes (26), and is engraved with a streamlined groove (27); a bent needle (10) is inserted into the through-welding hole (25) to form a connection circuit (28); The top cavity (5) is a piece of organic glass plate, and a through-screw hole (29) is optionally cut on one side of the top cavity (5), the number and size of the through-screw hole (29) correspond to those of the through-screw hole (26) of the bottom cavity (9), and a plurality of through-air holes (30) and a plurality of through-recesses (31) are cut; The LIGIE sensor array (7) is covered on the upper surface of the bottom cavity (9), wherein the silver conductive area (18) in the LIGIE sensor array (7) is attached to the connection circuit (28) of the bottom cavity (9) to form a contact circuit connection; and the rubber ring (6) is covered on the upper surface of the LIGIE sensor array (7); The top cavity (5) is covered on the rubber ring (6), wherein the through-screw hole (29) of the top cavity (5) corresponds to the through-screw hole (26) of the bottom cavity (9) in the vertical direction one by one; The screw (3) with the gasket (4) and the nut (11) is inserted into the aligned through-screw holes and tightened to form a tightly fitted microcavity; the tightly fitted microcavity is placed in the stainless steel clamp (8), the polytetrafluoroethylene joint (2) containing the polytetrafluoroethylene tube (1) is placed in the stainless steel clamp (8) and tightened, wherein the joint of the polytetrafluoroethylene joint (2) corresponds to the through-air hole (30) of the top cavity (5) for directional guiding of gas in and out.

2. The microcavity integrated electronic nose according to claim 1, wherein, The preparation process of the LIGIE sensor array (7) comprises: Step 1: preparation of a flexible LIGIE, using a laser (21) to engrave an interdigital electrode, that is, a flexible LIGIE, including interdigital electrodes (13) and lead wires (14) on a flexible polyimide film (12); Step 2: using a PET tape (15) as a mask plate attached to the flexible LIGIE, using a doctor blade (16) to apply conductive silver paste (17), after heating at 60-90 ℃ for 2-4 h, removing the PET tape (15), and fixing the conductive silver paste (17) at the position of the lead wire (14) of the LIGIE, that is, the LIGIE silver conductive area (18); Step 3: laser cutting the PI tape (19) to match the size of the flexible LIGIE, and the interdigital region of the PI tape (19) corresponding to the flexible LIGIE is removed; the PI tape (19) is vertically aligned and attached to the flexible LIGIE, and finally the interdigital region is dropped with a gas sensitive material (20); that is, the LIGIE sensing array (7) is prepared.

3. The microcavity integrated electronic nose according to claim 1, wherein, The preparation process of the bottom chamber (9) includes: Step 1: select a piece of organic glass plate (22) with a length of 8-20 cm, a width of 8-20 cm and a thickness of 2-4 mm, and optionally the largest area of the surface as the front surface, and paste the kraft paper (23); Step 2: use a laser (21) to cut through the soldering hole (25) with a diameter of 0.8 mm-1 mm in the organic glass plate containing the kraft paper on one side, which is the same as the number of lead (14) of LIGIE sensing array (7), and the same number of non-penetrating I-shaped pattern (24) of lead (14) of LIGIE sensing array (7) and 4-6 through screw holes (26) with a diameter of 3 mm-4 mm; At the same time, use the laser (21) to engrave a streamlined groove (27) in the organic glass plate containing the kraft paper on one side; Step 3: remove the kraft paper corresponding to the I-shaped pattern area, and use a squeegee (16) to scrape the conductive silver paste (17) in the I-shaped pattern area; At the same time, insert the corresponding number of bent needles (10) into the through soldering hole (25); heat the organic glass plate to 60-90℃ for 2-4h to obtain the circuit (28) for connecting the LIGIE sensing array (7) and the bent needle (10); Finally, remove all the kraft paper to form the bottom chamber (9).

4. The microcavity integrated electronic nose according to claim 1, wherein, The preparation process of the top chamber (5) includes: Select another piece of organic glass plate with a length of 8-20 cm, a width of 8-20 cm and a thickness of 2-4 mm, and optionally the largest area of the surface as the front surface, and use a laser (21) to cut through the screw hole (29) on the surface, which corresponds to the number and size of the through screw hole (26) prepared in the bottom chamber (9); cut several through air holes (30) with a diameter of 2 mm-3 mm and several through concave openings (31).

5. The application of the microcavity integrated electronic nose of claim 1 in volatile gas sensing.

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