Flexible ammonia concentration and distance double-parameter sensing element and preparation method thereof

Abstract

The invention relates to a flexible ammonia concentration and distance double-parameter sensing element and a preparation method thereof, and belongs to the technical field of flexible sensors. According to the sensing element, a polyimide (PI) flexible substrate with a central electrode lead is used as a substrate, and a spiral carboxylated multi-walled carbon nanotube and dodecylbenzene sulfonic acid doped polyaniline composite material (MWCNT-COOH-DBSA-PANI) is used as a sensitive material; according to the sensing element, the distance is detected through an eddy current effect generated by a spiral sensitive material, and the ammonia gas concentration is detected by virtue of the synergistic gas-sensitive characteristics of MWCNT-COOH and DBSA-PANI; wherein the DBSA-PANI is used as a p-type semiconductor material and endows the sensor with the capability of detecting ammonia gas (NH3) at normal temperature, the MWCNT-COOH is used for constructing a three-dimensional conductive network and is connected with the DBSA-PANI, a rough surface structure formed by the MWCNT-COOH provides more active sites for NH3, and the NH3 adsorption capability of the sensing element is enhanced. The sensing element prepared by the invention has the advantages of flexibility, simple structure and convenience in attachment, and is suitable for synchronously sensing the ammonia concentration and distance between narrow curved surface layers of complex industrial equipment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of flexible sensors, and particularly relates to a flexible ammonia concentration and distance dual-parameter sensing element and a preparation method thereof. BACKGROUND

[0002] As a widely used substance in the industrial field, ammonia has high toxicity and corrosive properties, so accurate concentration monitoring is the key to personnel safety and stable operation of equipment. With the advent of the industrial 4.0 era, intelligentization and integration have become the mainstream trend of industrial equipment development. Under this background, traditional single ammonia concentration monitoring has been difficult to meet the safety needs in complex industrial scenarios. During the operation of precision equipment, mechanical failure risks caused by abnormal part gap are increasingly prominent, and real-time monitoring of the distance between equipment parts has also become an important part of industrial safety protection. Although there are currently a large number of research results on ammonia concentration and distance detection, existing sensors are mostly limited to single function. In addition, the internal space of industrial equipment is small and has many curved surfaces, and it is not only difficult to install multiple single-function sensors in it, but also will multiply the cost and maintenance burden. Therefore, developing a flexible dual-parameter sensing element that can simultaneously sense ammonia concentration and distance is crucial for realizing comprehensive evaluation and early fault warning of the internal state of equipment. SUMMARY

[0003] The application aims to overcome the shortcomings of the prior art and provide a flexible ammonia concentration and distance dual-parameter sensing element and a preparation method thereof. Unlike traditional metal eddy current distance sensors and metal oxide semiconductor gas sensors, the application uses a spiral carboxylated multi-walled carbon nanotube and dodecyl benzene sulfonic acid doped polyaniline composite material (MWCNT-COOH@DBSA-PANI) as a sensitive material, which can simultaneously detect ammonia concentration and distance at room temperature.

[0004] The flexible ammonia concentration and distance dual-parameter sensing element provided by the application is composed of a polyimide (PI) flexible substrate with a center electrode lead and a spiral MWCNT-COOH@DBSA-PANI composite material; the PI flexible substrate with a center electrode lead has a length of 50 mm and a width of 38.5 mm; the spiral MWCNT-COOH@DBSA-PANI composite material is deposited on the PI flexible substrate with a center electrode lead by a spraying method, using a coil mask plate with a length of 50 mm, a width of 38.5 mm, a thickness of 0.05 mm, a line width and a line spacing of 0.5 mm, and 10 turns as a forming mold.

[0005] Meanwhile, the application provides a preparation method of a flexible ammonia concentration and distance dual-parameter sensing element, including the following steps:

[0006] (1) Cleaning: PI flexible substrate with central electrode lead and coil mask plate are cleaned by ultrasonic cleaning (20 min) with ethanol and deionized water respectively, and then dried at 40 DEG C after completion;

[0007] (2) Preparation of MWCNT-COOH@DBSA-PANI dispersion: first, 50 mL of deionized water is weighed into a beaker, 0.100 g of sodium dodecyl benzene sulfonate (SDBS) powder is added, and it is fully dissolved by magnetic stirring for 10 minutes to obtain a SDBS solution; then, 0.100 g of MWCNT-COOH powder is added to the obtained SDBS solution, and it is dispersed by ultrasonic and electric stirring for 30 minutes, and then magnetic stirring for 30 minutes to obtain a uniform MWCNT-COOH dispersion; finally, 2.000 g of DBSA-PANI is added to the above MWCNT-COOH dispersion, and it is dispersed by ultrasonic and electric stirring for 30 minutes, and then magnetic stirring for 30 minutes to obtain a MWCNT-COOH@DBSA-PANI dispersion;

[0008] (3) Spraying: first, the coil mask plate is covered on the PI flexible substrate with central electrode lead to form an assembly; then, the assembly is placed on a heating table preheated to 80 DEG C; by adjusting the spray gun, the MWCNT-COOH@DBSA-PANI dispersion is sprayed in the form of atomization; the spraying is carried out at a distance of 20 cm, and the spraying is carried out in several times, each time for 5 seconds, and the next spraying is carried out after the coating is dried for 10 seconds, and the process is alternately cycled until the spraying is completed;

[0009] (4) Drying: after the spraying is completed, it is placed in a 40 DEG C environment and dried to complete dryness, and finally a flexible ammonia concentration and distance dual-parameter sensing element is obtained.

[0010] The main principle of the flexible ammonia concentration and distance dual-parameter sensing element prepared in the application for detecting ammonia concentration and distance is as follows:

[0011] Under direct current excitation, when DBSA-PANI contacts with NH3 and other reducing gases, the lone pair electrons in NH3 will obtain H + from DBSA-PANI to form NH4 + , which makes DBSA-PANI undergo a reduction reaction, thereby reducing the number of hole carriers and increasing the resistance; when the ammonia concentration decreases, NH4 + will decompose into NH3 and H +This process restores DBSA-PANI to its initial state. Simultaneously, MWCNT-COOH in the MWCNT-COOH@DBSA-PANI composite material forms a dense conductive network and connects to DBSA-PANI. The rough surface structure of both, along with the carboxyl (-COOH) active sites on their surface, endows the sensing element with the ability to adsorb NH3. Therefore, the synergistic effect between MWCNT-COOH and DBSA-PANI directly endows this sensing element with the ability to detect ammonia concentration.

[0012] The MWCNT-COOH@DBSA-PANI composite material is conductive. When it is made into a spiral structure, an alternating magnetic field is generated around it when an alternating current is passed through it. The metal target being measured will induce eddy currents under the action of the alternating magnetic field. The distance between the sensing element and the metal target being measured can be detected by using the eddy current effect.

[0013] Features and effects of the present invention:

[0014] (1) The flexible ammonia concentration and distance dual-parameter sensing element prepared by the present invention can detect ammonia concentration by resistance under DC excitation and detect distance by impedance mode / angle under AC excitation, thereby enabling synchronous detection of ammonia concentration and distance dual parameters based on a single sensing element.

[0015] (2) By using a commercial PI flexible substrate with pre-placed center electrode leads as the substrate, the present invention eliminates the complex step of independently preparing electrodes in the traditional process, significantly simplifies the manufacturing process, and improves the preparation efficiency, process consistency and feasibility of large-scale production.

[0016] (3) The sensing element of the present invention is constructed with a PI flexible substrate, which has the characteristics of being thin and flexible, and can be closely fitted to the complex curved surfaces in industrial equipment, making it suitable for direct state detection in narrow spaces. Attached Figure Description

[0017] Figure 1 Dimensional diagram of a PI flexible substrate with a central electrode lead;

[0018] Figure 2 Here is a dimensional drawing of the coil mask.

[0019] Figure 3 A schematic diagram of the spraying process for a flexible ammonia concentration and distance dual-parameter sensing element;

[0020] Figure 4 Top view and front view of a flexible ammonia concentration and distance dual-parameter sensing element;

[0021] Figure 5The image shown is a scanning electron microscope (SEM) image of the MWCNT-COOH@DBSA-PANI composite material deposited by spraying in Specific Example 1.

[0022] Figure 6 The dynamic curves of resistance, impedance mode, and impedance angle of a flexible ammonia concentration and distance dual-parameter sensing element under the conditions of 30±1℃ and 31±2%RH are as follows: resistance, impedance mode, and impedance angle vary with ammonia concentration (5, 10, 20, 30, 40, 50ppm), and impedance angle varies with distance (5mm-4mm-3mm-2mm-1mm-0mm-1mm-2mm-3mm-4mm-5mm) under a fixed ammonia concentration.

[0023] Figures 1-4 In the diagram, a represents a PI flexible substrate with a central electrode lead; b represents a coil mask; c represents a spiral MWCNT-COOH@DBSA-PANI composite material; and d represents a spray gun. Detailed Implementation

[0024] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0025] See Figure 1 As shown, the PI flexible substrate a with a central electrode lead has a length of 50 mm and a width of 38.5 mm; see also Figure 2 As shown, the coil mask b is 50mm long, 38.5mm wide, 0.05mm thick, with a line width and spacing of 0.5mm and 10 turns; see [link to documentation]. Figure 3 Figure 4 Using a coil mask plate b as a molding die, the MWCNT-COOH@DBSAPANI dispersion is sprayed out in a mist form by adjusting the spray gun d and deposited on a PI flexible substrate a with a central electrode lead to obtain a spiral MWCNT-COOH@DBSA-PANI composite material c.

[0026] This invention proposes a flexible dual-parameter sensing element for ammonia concentration and distance, and its preparation method, comprising the following steps:

[0027] (1) Cleaning: The PI flexible substrate a with the center electrode lead and the coil mask b are cleaned with ethanol and deionized water in sequence, and then dried.

[0028] (2) Preparation of MWCNT-COOH@DBSA-PANI dispersion: First, measure 50 mL of deionized water into a beaker, add a certain amount of sodium dodecylbenzenesulfonate (SDBS) powder, and stir magnetically for 10 minutes to dissolve it completely to obtain an SDBS solution; then, add a certain amount of MWCNT-COOH powder to the obtained SDBS solution, disperse it by ultrasonication and electric stirring, and then continue to stir magnetically to obtain a uniform MWCNT-COOH dispersion; finally, add a certain amount of DBSA-PANI to the above MWCNT-COOH dispersion, disperse it by ultrasonication and electric stirring, and then continue to stir magnetically to finally obtain the MWCNT-COOH@DBSA-PANI dispersion;

[0029] (3) Spraying: First, cover the coil mask b onto the PI flexible substrate a with the center electrode lead to form an assembly; then, place the assembly on the heating table; by adjusting the spray gun d, the MWCNT-COOH@DBSA-PANI dispersion is sprayed out in atomized form; the spraying method is adopted in multiple sprayings until the spraying is completed;

[0030] (4) Drying: After spraying, place it in an environment of 40℃ to dry completely, and finally obtain a flexible ammonia concentration and distance dual-parameter sensing element.

[0031] Example 1

[0032] See Figure 1 As shown, the PI flexible substrate with a central electrode lead has a length of 50 mm and a width of 38.5 mm; see also Figure 2 As shown, the coil mask is 50mm long, 38.5mm wide, 0.05mm thick, with a line width and spacing of 0.5mm and 10 turns; see also... Figures 3-4 Using a coil mask as a molding die, the MWCNT-COOH@DBSA-PANI dispersion was sprayed out in a mist form by adjusting the spray gun and deposited on a PI flexible substrate with a central electrode lead to obtain a spiral MWCNT-COOH@DBSA-PANI composite material.

[0033] This invention proposes a flexible dual-parameter sensing element for ammonia concentration and distance, and its preparation method, comprising the following steps:

[0034] (1) Cleaning: The PI flexible substrate with the central electrode lead and the coil mask plate were ultrasonically cleaned with ethanol and deionized water respectively (20 min), and then dried at 40℃.

[0035] (2) Preparation of MWCNT-COOH@DBSA-PANI dispersion: First, measure 50 mL of deionized water into a beaker, add 0.100 g of sodium dodecylbenzenesulfonate (SDBS) powder, and stir magnetically for 10 minutes to dissolve it completely to obtain an SDBS solution; then, add 0.100 g of MWCNT-COOH powder to the obtained SDBS solution, first ultrasonically disperse and stir electrically for 30 minutes, and then continue to stir magnetically for 30 minutes to obtain a uniform MWCNT-COOH dispersion; finally, add 2.000 g of DBSA-PANI to the above MWCNT-COOH dispersion, and similarly first ultrasonically disperse and stir electrically for 30 minutes, and then continue to stir magnetically for 30 minutes to finally obtain the MWCNT-COOH@DBSA-PANI dispersion;

[0036] (3) Spraying: First, cover the coil mask plate onto the PI flexible substrate with the center electrode lead to form an assembly; then, place the assembly on a heating table preheated to 80°C; by adjusting the spray gun, the MWCNT-COOH@DBSA-PANI dispersion is sprayed out in atomized form; the spraying is carried out at a distance of 20cm, using a multi-spraying method, each spraying lasts for 5 seconds, pauses for 10 seconds to allow the coating to dry, and then the next spraying is carried out. This process is repeated until the spraying is completed.

[0037] (4) Drying: After spraying, place it in an environment of 40℃ to dry completely, and finally obtain a flexible ammonia concentration and distance dual-parameter sensing element.

[0038] Figure 5 This is a scanning electron microscope image of the MWCNT-COOH@DBSA-PANI composite material. The results show that DBSA-PANI coats and connects to the dense conductive network composed of MWCNT-COOH, forming a composite structure with uniform porosity and a rough surface.

[0039] Figure 6 The test results of the flexible ammonia concentration and distance dual-parameter sensing element under the conditions of 30±1℃ and 31±2%RH are shown, including the dynamic curves of its resistance (DC), impedance mode (AC) and impedance angle (AC) as ammonia concentration changes (5, 10, 20, 30, 40, 50ppm), as well as the dynamic curves of distance changes (5mm-4mm-3mm-2mm-1mm-0mm-1mm-2mm-3mm-4mm-5mm) under a fixed ammonia concentration. Figure 6 (a) is the real-time monitoring curve of temperature and relative humidity inside the test chamber during the test. The temperature and relative humidity inside the test chamber were maintained at 30±1℃ and 31±2%RH, respectively. Figure 6 (b) Demonstrates the stepwise change process of ammonia concentration and the cyclical change process of target distance set in the test;Figure 6 (c) shows the curves of the resistance of the sensing element as the ammonia concentration and distance change; the data shows that when the ammonia concentration increases from 0 ppm to 50 ppm, the relative resistance changes are 26.276% (5 ppm), 41.079% (10 ppm), 53.341% (20 ppm), 60.000% (30 ppm), 65.740% (40 ppm) and 68.677% (50 ppm), respectively; however, the resistance of the sensing element does not change as the distance changes (5 mm - 4 mm - 3 mm - 2 mm - 1 mm - 0 mm - 1 mm - 2 mm - 3 mm - 4 mm - 5 mm). Figure 6 (d, e) show the impedance modulus and impedance angle curves of the sensing element as the ammonia concentration and the distance to the target object change. With increasing ammonia concentration, both the impedance modulus and impedance angle exhibit a monotonic trend; however, at a fixed ammonia concentration, the impedance modulus increases with decreasing distance, while the absolute value of the impedance angle decreases. Experimental results indicate that the resistance of the sensing element is unaffected by changes in the distance to the target object, while the impedance is affected by both the distance to the target object and the ammonia concentration. Based on this characteristic, the current ammonia concentration is first determined using the resistance-ammonia concentration calibration relationship; then, based on the impedance modulus / angle-distance calibration relationship at this ammonia concentration, the distance to the target object is calculated, thereby achieving simultaneous detection and signal separation of the two parameters.

[0040] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A flexible ammonia concentration and distance dual-parameter sensing element, characterized in that, A polyimide (PI) flexible substrate with a center electrode lead and a spiralized carboxylated multi-walled carbon nanotube and dodecylbenzenesulfonic acid doped polyaniline composite material (MWCNT-COOH@DBSA-PANI) are composed; the PI flexible substrate with a center electrode lead has a length and a width of 50 mm and 38.5 mm, respectively; the spiralized MWCNT-COOH@DBSA-PANI composite material is deposited on the PI flexible substrate with a center electrode lead by using a coil mask plate with a length of 50 mm, a width of 38.5 mm, a thickness of 0.05 mm, a line width and a line distance of 0.5 mm, and 10 turns as a forming mold through a spraying method.

2. A method for preparing a flexible ammonia concentration and distance dual-parameter sensing element, which uses the flexible ammonia concentration and distance dual-parameter sensing element according to claim 1, characterized in that, It comprises the following steps: (1) cleaning: ultrasonic cleaning (20 min) is performed on the PI flexible substrate with a center electrode lead and the coil mask plate using ethanol and deionized water, respectively, and then drying at 40℃ after completion; (2) preparation of MWCNT-COOH@DBSA-PANI dispersion liquid: first, 50 mL of deionized water is weighed into a beaker, 0.100 g of sodium dodecylbenzenesulfonate (SDBS) powder is added, and magnetic stirring is performed for 10 minutes to fully dissolve it, obtaining an SDBS solution; then, 0.100 g of MWCNT-COOH powder is added to the obtained SDBS solution, and ultrasonic dispersion and electric stirring are performed for 30 minutes, followed by magnetic stirring for 30 minutes, obtaining a uniform MWCNT-COOH dispersion liquid; finally, 2.000 g of DBSA-PANI is added to the above MWCNT-COOH dispersion liquid, and ultrasonic dispersion and electric stirring are performed for 30 minutes, followed by magnetic stirring for 30 minutes, finally obtaining a MWCNT-COOH@DBSA-PANI dispersion liquid; (3) spraying: first, the coil mask plate is covered on the PI flexible substrate with a center electrode lead to form an assembly; then, the assembly is placed on a heating table preheated to 80℃; by adjusting the spray gun, the MWCNT-COOH@DBSA-PANI dispersion liquid is sprayed in the form of atomization; spraying is carried out at a distance of 20 cm, and a multiple spraying mode is adopted, each time for 5 seconds, and the next spraying is carried out after the coating is dried for 10 seconds, and the process is alternately cycled until the spraying is completed; (4) drying: after the spraying is completed, it is placed in a 40℃ environment and dried to complete dryness, and finally a flexible ammonia concentration and distance dual-parameter sensing element is obtained.

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