CN110849941B - Preparation method of resistance-type humidity sensing device based on loose carbon structure and hydrophilic polymer material composition - Google Patents
Preparation method of resistance-type humidity sensing device based on loose carbon structure and hydrophilic polymer material composition Download PDFInfo
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- CN110849941B CN110849941B CN201911300882.2A CN201911300882A CN110849941B CN 110849941 B CN110849941 B CN 110849941B CN 201911300882 A CN201911300882 A CN 201911300882A CN 110849941 B CN110849941 B CN 110849941B
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- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
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- G01N27/127—Composition of the body, e.g. the composition of its sensitive layer comprising nanoparticles
Abstract
A preparation method of a resistance-type humidity sensing device based on a loose carbon structure and a hydrophilic polymer material composite belongs to the technical field of humidity sensing devices. The device is a novel humidity sensor based on a loose carbon nano-film structure, and the surface of the loose carbon nano-film structure is covered with a hydrophilic polymer material. Under different humidity changes, the capacity of the composite material for adsorbing water molecules changes, and then resistance changes are caused to carry out humidity sensing. The device is manufactured by manufacturing a pair of parallel electrodes with a certain interval on a flexible substrate, depositing a layer of loose carbon nano-structure film in a gap between the parallel electrodes, and finally covering the surface of the loose carbon nano-structure film with a hydrophilic polymer. The sensor combines two substances which have small response to the change of the environmental humidity to form a resistance type sensor with high humidity change response amplitude. The invention has the advantages of simple manufacture, low cost, environmental protection, repeated use, strong practicability and the like.
Description
Technical Field
The invention relates to a resistance-type humidity sensing device compounded by a carbon nano structure and a polymer material, in particular to a resistance-type humidity sensing device compounded by a loose carbon structure and a hydrophilic polymer material, which is simple to prepare and has high stability and repeatability.
Background
As early as 1939, moisture sensors relying on changes in resistance have been studied, but they have not been widely accepted because of their small detection range and limited conditions of use. Later, as research has progressed, resistance humidity sensor technology has matured considerably. In 2016, Zou et al discovered a response characteristic of chitosan material resistance as a function of humidity based on a humidity responsive proton conduction sensor exposed to hydrogen gas with quartz as a substrate, platinum as an electrode, and chitosan as a sensing material. (J, Zou et al, IEEE Sensors Journal, 2016, vol 16, pp 8884-. In 2019, Dai et al studied a humidity sensor based on a chitosan/zinc oxide/single-walled carbon nanotube composite film, which was formed by drop-casting chitosan on a synthetic powder of zinc oxide and single-walled carbon nanotubes, using alumina as a substrate and metallic silver as an electrode. The sensor has the characteristics of good repeatability and good response recovery capability, but the sensitivity is not ideal. (H, Dai et al, Sensors and actors B-Chemical, 2019, vol 283, pp 786-792). In the same year, Wu et al conducted studies of fast response and flexible humidity sensors based on carbon nanocoils. The sensor deposits gold interdigital electrodes on Liquid Crystal Polymer (LCP), the carbon nano-coil is arranged in the gap of the gold electrodes, and the resistance value variation curve along with the humidity at two ends of the gold electrodes can be obtained after data processing. It is proved to be a resistance type humidity sensor having a high response amplitude and high stability, but has a disadvantage of a slow response speed. (J, Wu et al, Acs Applied Materials & Interfaces, 2019, vol 11, pp 4242-.
Disclosure of Invention
In order to overcome the defects that a carbon nano structure is weak in water absorption capacity and small in change caused by humidity, a polymer material with certain water absorption capacity is used as a modified material and covers the surface of the carbon nano structure, so that the response amplitude of the double-composite film to the environmental humidity is obviously increased.
The technical scheme adopted by the invention is as follows: a sensing device for measuring humidity based on resistance change is a novel resistance type humidity sensor based on a loose carbon nano film structure between parallel conductive electrodes, and the surface of the loose carbon nano film structure is covered with a hydrophilic polymer material.
A method for preparing a humidity sensing device based on the composition of a loose carbon structure and a polymer material comprises the following steps:
(1) preparing a flexible substrate and preparing parallel conductive electrodes on the substrate
Preparing polydimethylsiloxane, and preparing a 200 nm parallel gold electrode on the surface of the polydimethylsiloxane by a magnetron sputtering method, wherein the electrode gap is 100 mu m;
(2) the loose carbon nano-film structure is deposited in the parallel electrode gap
Fe2(SO4)3/SnCl2Dripping the solution as a catalyst precursor on a quartz substrate, drying, and calcining the substrate at 710 ℃ for 30 min; introducing acetylene gas with the flow rate of 15 sccm under the argon environment with the flow rate of 325 sccm by a thermal chemical vapor deposition method, calcining for 30 min at 710 ℃, and synthesizing a carbon nanocoil on the surface of the substrate; placing the substrate in ethanol, and then placing the substrate in an ultrasonic cleaning instrument for ultrasonic treatment to obtain a carbon nano-coil dispersion liquid; dropping the dispersed liquid of the carbon nano-coil between gold electrodes, and applying alternating current of 5V, 1 KHz on the gold electrodes to deposit the carbon nano-coil in an electrophoresis mode;
(3) the hydrophilic polymer material covers the surface of the loose carbon nano-film
Dripping and casting a hydrophilic polymer material solution on the carbon nano wire ring and drying to obtain the humidity sensing device; the hydrophilic polymer material adopts chitosan or polyvinyl alcohol.
The invention uses an electrophoresis method to deposit a loose carbon structure between parallel conductive electrodes, and a hydrophilic polymer material covers the surface of the loose carbon structure to manufacture a composite structure with a hydrophilic material attached on a porous network carbon structure.
The invention adopts a humidity sensor with a loose carbon structure and a hydrophilic polymer material covered on the surface as a device, and utilizes the composite structure to have stronger reversible adsorption capacity to water so as to test the change of the environmental humidity.
The loose carbon structure itself adsorbs water molecules, resulting in a change in sensor resistance with different degrees of adsorption of water molecules.
Hydrophilic polymer materials are also sensitive to water molecules, and the resistance changes correspondingly when humidity changes.
The combination of the loose carbon structure and the hydrophilic polymer material improves the humidity sensitivity and the detection limit of the sensing device.
The principle of the invention is that the loose carbon structure adsorbs water molecules to serve as an electron donor, thereby reducing the charge carrier concentration and increasing the resistance level. The hydrophilic polymer material permeates into the porous loose carbon structure mixed network, and the electronic transition difficulty of the carbon structure is improved, so that the resistance response amplitude is further increased. The composite structure has fast response to water adsorption and desorption and has little influence on the microstructure, so the invention has strong repeatability. The invention has low response delay and good stability when the humidity is changed in rising and falling.
The invention has the beneficial effects that: for more convenient and highly sensitive testing of humidity changes, the device is made by coating the surface of the loose carbon nanostructures with a hydrophilic polymer material. The loose carbon structure is used for adsorbing water molecules to serve as an electron donor, so that the concentration of charge carriers in the loose carbon structure is reduced, and the resistance level is increased; the hydrophilic polymer material permeates into the porous loose carbon structure mixed network, the electronic transition difficulty of the loose carbon structure is improved, and the resistance of a composite structure formed by the hydrophilic polymer material and the loose carbon structure is greatly increased. The device has improved sensitivity and hysteresis over conventional resistive humidity sensors. Through experimental tests, the sensor achieves 20% of resistance response amplitude when the humidity is increased from 45% to 85%.
Meanwhile, the invention also has the following advantages: the manufacturing is very simple and the cost is low; the device can work stably for a long time; the device has no pollution to the environment and can be repeatedly used.
Drawings
Fig. 1 is a schematic view of the humidity sensing device.
FIG. 2 is a graph of the fitted response of a humidity sensor based on carbon nanocoil surface coated with polyvinyl alcohol at different humidities.
FIG. 3 is a graph of the fitted response of a humidity sensor based on carbon nanocoil surface coated with chitosan at different humidities.
Detailed Description
The specific implementation method of the invention is as follows:
the following only describes an example of a humidity sensing device using a carbon nanocoil surface coated with chitosan/polyvinyl alcohol, and the scope of the present invention is not limited thereto.
Example 1
1. The preparation process of the carbon nano-coil dispersion liquid is as follows:
and measuring 20 ml of ethanol, and putting the carbon nano-coil substrate into an ultrasonic cleaner for ultrasonic treatment for 1 hour to obtain the carbon nano-coil dispersion liquid.
2. Preparing a chitosan solution. Weighing chitosan powder, and preparing with acetic acid solution to obtain 0.75% wt chitosan solution.
3. Preparation of Polydimethylsiloxane (PDMS) with dimensions of 3X 1.5 cm: mixing liquid PDMS and curing agent at a ratio of 10:1, stirring, pouring into a prepared cubic mold to make the thickness of the liquid PDMS 500 μm, placing the mold containing the liquid PDMS into a vacuum box, vacuumizing for 1 hr, taking out from the vacuum box, drying in a 60 deg.C constant temperature drying oven for 30 min to completely dry the liquid PDMS into solid to obtain a film-shaped flexible humidity sensor substrate, and cutting the substrate into 3 × 1.5 cm2The size of (c). Cutting is completed, and 200 nm parallel gold electrodes are prepared on the surface of each PDMS through a magnetron sputtering method, wherein the electrode gap is 100 mu m.
4. And applying 5V, 1 KHz alternating current to the gold electrode by using a signal generator, depositing the carbon nano coil in an electrophoresis mode, and measuring the resistance by using an ohmmeter until the measured resistance does not change, namely finishing the deposition.
5. The humidity sensor can be prepared by dropping and casting chitosan solution on the carbon nano wire ring until the carbon nano wire ring is fully paved (about 20 mu L) and drying.
Example 2
1. The preparation process of the carbon nano-coil dispersion liquid is as follows:
and measuring 20 ml of ethanol, and putting the carbon nano-coil substrate into an ultrasonic cleaner for ultrasonic treatment for 1 hour to obtain the carbon nano-coil dispersion liquid.
2. A3% wt polyvinyl alcohol (degree of polymerization 1788) solution was prepared.
3. Preparation of Polydimethylsiloxane (PDMS) with dimensions of 3X 1.5 cm: mixing liquid PDMS and curing agent at a ratio of 10:1, stirring, pouring into a prepared cubic mold to make the thickness of the liquid PDMS 500 μm, placing the mold containing the liquid PDMS into a vacuum box, vacuumizing for 1 hr, taking out from the vacuum box, drying in a 60 deg.C constant temperature drying oven for 30 min to completely dry the liquid PDMS into solid to obtain a film-shaped flexible humidity sensor substrate, and cutting the substrate into 3 × 1.5 cm2The size of (c). Cutting is completed, and 200 nm parallel gold electrodes are prepared on the surface of each PDMS through a magnetron sputtering method, wherein the electrode gap is 100 mu m.
4. And applying 5V, 1 KHz alternating current to the gold electrode by using a signal generator, depositing the carbon nano coil in an electrophoresis mode, and measuring the resistance by using an ohmmeter until the measured resistance does not change, namely finishing the deposition.
5. And dripping and casting a polyvinyl alcohol solution on the carbon nano wire ring until the carbon nano wire ring is fully paved (about 20 mu L) and drying to prepare the finished humidity sensor.
Example 3
1. Test procedure
Fig. 2 and 3 are related experimental data obtained by putting two humidity sensors manufactured in the above embodiment into a constant temperature and humidity chamber. The temperature set by the constant temperature and humidity box is 25 ℃, the humidity is increased from 45% to 85%, the adjustment is carried out once every 5%, and relevant resistance data are recorded through a resistance meter.
2. Test results
The recorded resistance value is subjected to data processing by adopting the following formula to obtain the response conditions of two humidity sensors, namely:
(wherein NR is normalizedResistance,. DELTA.R is the changing resistance value, R0Is initial resistance value)
3. In the humidity sensor based on the carbon nanocoil surface covered with polyvinyl alcohol, when the relative humidity changes from 45% to 85%, the resistance response amplitude is shown in fig. 2.
4. Based on the humidity sensor with the carbon nanocoil surface coated with chitosan, when the relative humidity changes from 45% to 85%, the resistance response amplitude is shown in fig. 3.
5. From the above images, it can be seen that: the humidity sensor based on the carbon nano coil with the surface covered by the chitosan has better response amplitude and repeatability than the humidity sensor based on the carbon nano coil with the surface covered by the polyvinyl alcohol.
Claims (1)
1. A preparation method of a resistance-type humidity sensing device based on a loose carbon structure and a hydrophilic polymer material is characterized by comprising the following steps:
the humidity sensing device is based on a loose carbon nano film structure between parallel conductive electrodes, and the surface of the loose carbon nano film structure is covered with a hydrophilic polymer material;
(1) preparing a flexible substrate and preparing parallel conductive electrodes on the substrate
Preparing polydimethylsiloxane, and preparing a 200 nm parallel gold electrode on the surface of the polydimethylsiloxane by a magnetron sputtering method, wherein the electrode gap is 100 mu m;
(2) the loose carbon nano-film structure is deposited in the parallel electrode gap
Fe2(SO4)3/SnCl2Dripping the solution as a catalyst precursor on a quartz substrate, drying, and calcining the substrate at 710 ℃ for 30 min; introducing acetylene gas with the flow rate of 15 sccm under the argon environment with the flow rate of 325 sccm by a thermal chemical vapor deposition method, calcining for 30 min at 710 ℃, and synthesizing a carbon nanocoil on the surface of the substrate; placing the substrate in ethanol, and then placing the substrate in an ultrasonic cleaning instrument for ultrasonic treatment to obtain a carbon nano-coil dispersion liquid; dropping the dispersed liquid of the carbon nano-coil between gold electrodes, and applying alternating current of 5V and 1 KHz on the gold electrodes to deposit the carbon nano-coil in an electrophoresis mode;
(3) the hydrophilic polymer material covers the surface of the loose carbon nano-film
Dripping and casting a hydrophilic polymer material solution on the carbon nano wire ring and drying to obtain the humidity sensing device; the hydrophilic polymer material adopts chitosan or polyvinyl alcohol.
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