CN117309940A - Flexible self-powered humidity sensor based on zinc oxide piezoelectricity and preparation method thereof - Google Patents
Flexible self-powered humidity sensor based on zinc oxide piezoelectricity and preparation method thereof Download PDFInfo
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- XIOUDVJTOYVRTB-UHFFFAOYSA-N 1-(1-adamantyl)-3-aminothiourea Chemical compound C1C(C2)CC3CC2CC1(NC(=S)NN)C3 XIOUDVJTOYVRTB-UHFFFAOYSA-N 0.000 claims description 11
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Abstract
The invention discloses a flexible self-powered humidity sensor based on zinc oxide piezoelectricity and a preparation method thereof, and belongs to the technical field of sensors. The method comprises the following steps: preparing a flexible substrate and a first functional layer: preparing a positive electrode and a negative electrode; preparing a second functional layer; preparing a packaging layer: the packaging layer is prepared by mixing PDMS material and carboxymethyl chitosan cross-linking agent, uniformly mixing PDMS and carboxymethyl chitosan cross-linking agent according to a proportion to obtain packaging layer mixed solution, preparing a film-shaped packaging layer on the obtained film growing with ZnO nano-rods through spin coating or knife coating technology, and heating and annealing. Compared with the prior art, the invention has the advantages that: the flexible self-powered humidity sensor based on zinc oxide piezoelectricity does not need external power supply, but converts water vapor in a plant growth environment into a voltage signal, so that the cost of later maintenance is reduced, and the environment is protected; the device has simple structure, high fitting degree with plants and good biocompatibility.
Description
Technical Field
The invention relates to the technical field of sensors, in particular to a flexible self-powered humidity sensor based on zinc oxide piezoelectricity and a preparation method thereof.
Background
Plants play a vital role in the ecosystem, and are closely related to human survival. However, biological factors such as pathogens, pests and the like and abiotic factors such as water stress, drought stress and the like are continuously generated, so that crops are threatened by the diseases, the ecological system can be destroyed, and agricultural deterioration can be caused, so that stable development of human beings is not facilitated. Therefore, grasping the health status of plants is important.
A plant sensor is a device for monitoring the physiological condition and growth environment of plants, which can measure and record in real time the environmental parameters such as illumination, temperature, humidity, etc. in which the plants are located. These parameters are critical to the growth and development of plants. Wherein humidity is one of the key factors affecting plant growth, plants require proper humidity to maintain normal physiological function and moisture balance. Humidity sensors can help measure the humidity level of the plant's body surface and surrounding environment to ensure that the plant is subjected to the proper humidity conditions. The accuracy and reliability of humidity sensors have a significant impact on the health of plants. Currently, humidity sensor research has been advanced to some extent. Many research teams have focused on developing new humidity sensors that employ different principles of operation and materials to improve the sensitivity, measurement range, and stability of the sensor. However, humidity sensor research still faces some challenges and problems. For example, the current detection method for the surface humidity information of many plants still has the problems of low response speed, easy damage to plant leaves in the detection process and the like. Meanwhile, along with the continuous development of the agricultural sensor, the problem of energy supply becomes one of important factors limiting the development of the agricultural sensor, and the batteries used by the current plant humidity sensor are all disposable dry batteries, so that the energy cannot be stably provided for a long time, the environment pollution is easy to be caused, and a large amount of resources such as manpower are consumed for replacing the batteries.
In the related art, as disclosed in chinese patent document CN111486904a, a resonant surface acoustic wave wireless passive temperature/humidity sensor is disclosed, and the temperature/humidity sensor is formed by integrating a temperature sensor and a humidity sensor in parallel and coplanar manner, and includes a composite piezoelectric substrate layer, an interdigital transducer, a reflective grating array, and a surface piezoelectric waveguide layer, wherein the reflective grating array forms a resonant cavity, the temperature sensor and the humidity sensor have the same resonator structure and surface piezoelectric waveguide layer structure, and a nano humidity sensitive material is integrated above the surface piezoelectric waveguide layer of the humidity sensor. The disadvantage is that the solution does not solve the problem of slow response and recovery speed of the humidity sensor.
In summary, the slow response and recovery speed of the conventional humidity sensor are the problems to be solved in the prior art.
Disclosure of Invention
1. Technical problem to be solved
Aiming at the problems of low response and recovery speed of the existing humidity sensor in the prior art, the invention provides the flexible self-powered humidity sensor based on zinc oxide piezoelectricity and the preparation method thereof, which can realize effective lamination with curved leaf surfaces, and can spontaneously adsorb moisture in plant growth environment to generate voltage without an external power supply system, thus having low post maintenance cost and being environment-friendly. Meanwhile, the response and recovery speed of the humidity sensor are improved by utilizing the characteristic that the polyimide material swells under different humidity environments and has high recovery speed.
2. Technical proposal
The aim of the invention is achieved by the following technical scheme.
The flexible self-powered humidity sensor based on zinc oxide piezoelectricity comprises a flexible substrate, a positive electrode, a first functional layer, a negative electrode, a second functional layer and a packaging layer, wherein the positive electrode is integrated on the flexible substrate, the first functional layer is integrated on the positive electrode, the negative electrode is integrated on the first functional layer, the second functional layer is prepared on the negative electrode, and the positive electrode and the negative electrode are of vertical structures.
Further, the flexible substrate, the positive electrode, the second functional layer and the packaging layer are all in a flexible film form.
Still further, the flexible substrate is made of a flexible polymeric material.
Still further, PET is used as the flexible polymeric material.
The preparation method of the flexible self-powered humidity sensor based on the zinc oxide piezoelectricity comprises the following steps:
preparing a flexible substrate and a first functional layer:
sputtering a transparent ITO conductive film coating on the PET base material, performing high-temperature annealing treatment to obtain a flexible substrate, and growing and preparing ZnO nano rods by a hydrothermal method to obtain a first functional layer;
preparing a positive electrode and a negative electrode:
the positive electrode and the negative electrode are composed of ITO and carbon nanotube materials, and the ITO electrode is integrated on the substrate PET;
preparing a second functional layer:
the second functional layer is made of polyimide material;
preparing a packaging layer:
the packaging layer is prepared by mixing PDMS material and carboxymethyl chitosan cross-linking agent, uniformly mixing PDMS and carboxymethyl chitosan cross-linking agent according to a proportion to obtain packaging layer mixed solution, preparing a film-shaped packaging layer on the obtained film growing with ZnO nano-rods through spin coating or knife coating technology, and heating and annealing.
Further, the steps for preparing the flexible substrate are specifically as follows:
cutting a PET-ITO film and fixing the PET-ITO film on a glass slide by using a double-sided adhesive tape;
placing the fixed PET-ITO film into a plasma etching machine to clean the surface of the substrate to obtain a hydrophilic ITO surface;
growing ZnO nano rods on the PET-ITO film substrate subjected to plasma cleaning by adopting a hydrothermal growth method;
taking down the PET-ITO film growing with the ZnO nano-rods, and repeatedly flushing with deionized water, wherein the treated PET-ITO film growing with the ZnO nano-rods is taken as a sample;
the sample is put on a heating table to be annealed at 80 ℃ to dry the sample or the sample is dried by nitrogen.
Furthermore, the first functional layer is ZnO nano-rod prepared by hydrothermal growth, and the preparation of the first functional layer comprises the following steps:
weighing anhydrous zinc acetate, preparing an anhydrous zinc acetate solution with the concentration of 10mmol/L, and adopting absolute ethyl alcohol as a solvent; weighing zinc nitrate hexahydrate, and preparing an equimolar mixed solution of the zinc nitrate hexahydrate and the hexamethylenetetramine by using deionized water as a solvent;
spin-coating 0.15mL of zinc acetate solution on an ITO substrate at 1500rpm for 45s, then heating and annealing on a heating table at 140-150 ℃ for 2-3 minutes, and repeating the actions for 10 times to obtain a seed crystal layer;
reversely immersing PET-ITO coated with a seed crystal layer after spin coating into a mixed solution of zinc nitrate hexahydrate and hexamethylenetetramine for 4-6 hours to grow ZnO nano rods;
and taking the prepared sample out of the growth liquid, flushing the sample with deionized water, and then placing the sample on a heating table for annealing and drying or drying the sample with nitrogen.
Further, the steps for preparing the positive electrode and the negative electrode are specifically as follows:
attaching the annealed PET-ITO film with the ZnO nanorods growing thereon to an interdigital electrode mask, placing the mask on a heating table, and spraying a carbon nanotube electrode by a spray gun while heating to prepare a carbon nanotube electrode;
the electrode spraying preparation process is as follows:
mixing the carbon nano tube conductive paint with deionized water according to the weight ratio of 1: and uniformly mixing the components according to the mass ratio of 20 to form a carbon nanotube suspension, filling the mixed carbon nanotube suspension into a spray gun, and spraying the carbon nanotube suspension onto a film attached to the interdigital electrode mask for 20-30 minutes to obtain the carbon nanotube interdigital electrode.
Further, the step of preparing the second functional layer specifically includes:
taking down the sample of the spray electrode from the heating table, taking down the interdigital electrode mask plate, uniformly dripping polyimide solution on the surface of the sample, and then putting the sample on the heating table again for annealing to obtain a polyimide film, namely the second functional layer;
the polyimide film is prepared as follows:
and dissolving polyimide in organic solution acetone to form film-forming slurry, then dripping the slurry on a film, and placing the film-forming slurry on a heating table for annealing to obtain the polyimide film.
Further, the step of preparing the encapsulation layer specifically includes:
uniformly mixing PDMS and carboxymethyl chitosan cross-linking agent according to a certain proportion to obtain packaging layer mixed liquor, preparing film form packaging layer on the obtained sample by means of spin coating or knife coating process, and heating and annealing.
3. Advantageous effects
Compared with the prior art, the invention has the advantages that:
the flexible self-powered humidity sensor based on zinc oxide piezoelectricity does not need external power supply, but converts water vapor in a plant growth environment into a voltage signal, so that the cost of later maintenance is reduced, and the environment is protected; the device has simple structure, high fitting degree with plants and good biocompatibility; meanwhile, the deformation of the polyimide layer under different humidity conditions can be increased by increasing the thickness of the polyimide layer, and the voltage generated by the ZnO layer due to the piezoelectric effect is larger, so that the output performance of the self-powered device, such as voltage signals, response and recovery speed, is improved.
Drawings
FIG. 1 is a schematic diagram of the overall structure of a flexible self-powered humidity sensor based on zinc oxide piezoelectricity in an embodiment of the present invention;
FIG. 2 is a schematic diagram of the working principle of a flexible self-powered humidity sensor based on zinc oxide piezoelectricity according to an embodiment of the present invention;
FIG. 3 is a representation of a ZnO nano-rod electron microscope of a flexible self-powered humidity sensor based on zinc oxide piezoelectricity in an embodiment of the invention;
fig. 4 is a schematic diagram of a bubbling method humidity testing system of a flexible self-powered humidity sensor based on zinc oxide piezoelectricity according to an embodiment of the present invention.
The reference numerals in the figures illustrate:
1. a flexible substrate; 2. a positive electrode; 3. a first functional layer; 4. a negative electrode; 5. a second functional layer; 6. and an encapsulation layer.
Detailed Description
The invention will now be described in detail with reference to the drawings and the accompanying specific examples.
As shown in fig. 1 to 3, the present solution provides a flexible self-powered humidity sensor based on zinc oxide piezoelectricity, comprising a flexible substrate 1, a positive electrode 2, a first functional layer 3, a negative electrode 4, a second functional layer 5 and an encapsulation layer 6. The positive electrode 2 is integrated on the flexible substrate 1, the first functional layer 3 is integrated on the positive electrode 2, the negative electrode 4 is integrated on the first functional layer 3, the positive electrode 2 and the negative electrode 4 are of a vertical structure, the negative electrode 4 is provided with a second functional layer 5 for water absorption expansion, and the second functional layer 5 for water absorption expansion is integrated with a packaging layer 6. Wherein the flexible substrate 1, the positive electrode 2, the second functional layer 5 and the packaging layer 6 are all in the form of flexible films.
The flexible substrate 1 is made of a flexible polymer material, and the flexible substrate 1 has good deformability and can be attached to any curved surface.
In particular, the flexible polymeric material is a flexible stretchable polymeric material having good resistance to chemical attack, and PET is used for the flexible polymeric material in this embodiment.
Specifically, the positive electrode 2 is ITO integrated on the flexible substrate 1. The flexible substrate 1 and the positive electrode 2 are integrated to obtain the finished PET-ITO film.
The first functional layer 3 is a ZnO nano rod on a flexible substrate PET-ITO through a hydrothermal growth method, the first functional layer 3 has good piezoelectric effect, when the ZnO nano rod is bent under pressure, the outer surface is stretched (positive strain occurs), the inner surface is compressed (negative strain occurs), and then an electric field E and a potential difference are generated in the ZnO nano rod body, so that an electric signal is output, and the sensing and self-power supply of humidity are realized.
The positive and negative electrodes 2, 4 are respectively positioned at the lower layer and the upper layer of the functional layer 3. In this embodiment, the negative electrode 4 is formed by attaching the mask plate of the interdigital electrode to a PET-ITO film on which uniform ZnO nanorods are grown, placing the mask plate on a heating table, and spraying the carbon nanotube electrode by using a spray gun while heating. Wherein the temperature of the heating table is set to 80-90 ℃, and the carbon nano tube conductive coating and deionized water are mixed according to the proportion of 1: and uniformly mixing the components according to the mass ratio of 20 to form the carbon nano tube suspension.
Specifically, the polyimide solution in the second functional layer 5 is polyimide dissolved in an organic solution to form a film-forming slurry, the slurry is dripped on a film, and the film is placed on a heating table for heating at 350-400 ℃ for 45-60 minutes to obtain a polyimide film. The organic solution is acetone. The polyimide expands with water to transmit the downward force generated to the functional layer 3, and a potential difference is generated by the piezoelectric effect. The method has wider measurement range and faster response and recovery speed than a general flexible humidity sensor.
The encapsulation layer 6 is made of PDMS, and after the PDMS stock solution and the carboxymethyl chitosan cross-linking agent are uniformly mixed to form a mixed solution, the mixed solution is spin-coated or knife-coated on the second functional layer 5, so that the encapsulation layer 6 is obtained. The encapsulation layer 6 is used for improving the environmental stability of the sensor and preventing external environmental factors from affecting the stability of polyimide.
The mechanism of the flexible self-powered humidity sensor based on zinc oxide piezoelectricity that this scheme provided is polyimide and takes place the swelling phenomenon under different humidity environment, and it makes ZnO piezo-resistor produce the potential difference because of deformation produces decurrent power, forms the signal of telecommunication from this, consequently compares other humidity sensor, and humidity sensor of this scheme has wider measuring range, and response and recovery speed are also faster.
The embodiment discloses a preparation method of a flexible self-powered humidity sensor based on zinc oxide piezoelectricity, which comprises the following steps:
preparing a flexible substrate and a first functional layer:
the flexible substrate is made of a stretchable polymer material PET, the surface of which is deposited with a layer of ITO electrodes. The specific steps for preparing the flexible substrate are as follows:
sputtering a transparent ITO conductive film coating on the PET base material, and performing high-temperature annealing treatment to obtain the flexible substrate.
Specifically, a PET-ITO film is cut and fixed on a glass slide by using a double-sided tape;
more specifically, the PET-ITO film can be cut into the size of 2cm multiplied by 2cm, the larger the area of the device is, the higher the voltage output of the device is, and the self-power supply can be better realized, but the photosynthesis on the surface of the plant leaf is hindered due to the fact that the actual size of the leaf is considered, so that the size of 2cm multiplied by 2cm is selected;
placing the fixed PET-ITO film into a plasma etching machine to clean the surface of the substrate to obtain a hydrophilic ITO surface, wherein the ITO substrate can be subjected to subsequent spin coating to prepare a ZnO seed crystal layer only after the ITO substrate has hydrophilicity;
and the ZnO nano rod is grown on the obtained PET-ITO film substrate after plasma cleaning by adopting a hydrothermal growth method, and the ZnO nano rod is prepared by adopting the hydrothermal method, so that the material is cheap, the process is simple, and the grown ZnO nano rod is uniform and compact.
And taking down the obtained PET-ITO film with the ZnO nano rod, repeatedly flushing with deionized water to remove impurities and grow the unstable ZnO nano rod, obtaining the treated PET-ITO film with the ZnO nano rod, namely a sample, and then placing the sample on a heating table for annealing and drying the sample at 80 ℃ or drying the sample with nitrogen.
The first functional layer is the ZnO nano rod prepared by the growth of a hydrothermal method.
The specific steps for preparing the first functional layer are as follows:
13mg of anhydrous zinc acetate is weighed, 6ml of anhydrous zinc acetate solution with the concentration of 10mmol/L is prepared, and the solvent is absolute ethyl alcohol;
371mg of zinc nitrate hexahydrate and 175mg of hexamethylenetetramine are weighed, 50ml of deionized water is used as a solvent, and an equimolar mixed solution of zinc nitrate hexahydrate and hexamethylenetetramine is prepared;
specifically, the zinc nitrate hexahydrate is 25mmol/L, and the hexamethylenetetramine is 25mmol/L;
spin-coating 0.15mL of zinc acetate solution on an ITO substrate at 1500rpm for 45s, then heating and annealing on a heating table at 140-150 ℃ for 2-3 minutes, and repeating the actions for 10 times to obtain a seed crystal layer;
and (3) reversely immersing the PET-ITO coated with the seed crystal layer after spin coating into a mixed solution of zinc nitrate hexahydrate and hexamethylenetetramine for 4-6 hours, and growing the ZnO nano rod. The longer the growing time in the mixed solution of zinc nitrate hexahydrate and hexamethylenetetramine, the longer and denser the length of the grown ZnO nano rod, the higher the voltage output of the piezoelectric effect;
and taking the prepared sample out of the growth liquid, washing the part which is not firm in growth by deionized water, and placing the sample on a heating table for annealing and drying at 80 ℃ or drying the sample by nitrogen.
Preparing a positive electrode and a negative electrode:
the positive electrode and the negative electrode are composed of ITO and carbon nanotube materials, and the ITO electrodes are integrated on the flexible substrate PET.
Specifically, the carbon nanotube electrode is manufactured by attaching the annealed PET-ITO film growing with ZnO nanorods to an interdigital electrode mask plate, placing the PET-ITO film on a heating table, and spraying the carbon nanotube electrode by using a spray gun while heating;
more specifically, the electrode spray preparation process is as follows:
mixing the carbon nano tube conductive paint with deionized water according to the weight ratio of 1: and (3) uniformly mixing the materials according to the mass ratio of 20 to form a carbon nanotube suspension, filling the mixed carbon nanotube suspension into a spray gun, spraying the film attached to the interdigital electrode mask for 20-30 minutes to obtain the carbon nanotube interdigital electrode, wherein the longer the spraying time is, the thicker the electrode is, the better the stability is but the relatively larger the resistance is, and the carbon nanotube interdigital electrode is obtained through multiple experiments: the electrode obtained by spraying for 20-30 minutes is optimal.
Preparing a second functional layer:
the second functional layer on the carbon nanotube electrode is made of polyimide material. The specific steps for preparing the second functional layer are as follows:
taking down the obtained sample sprayed with the electrode from the heating table, slowly taking down the interdigital electrode mask, uniformly dripping polyimide solution on the surface of the sample, and then putting the sample on the heating table again for annealing to obtain a polyimide film, namely a second functional layer;
specifically, the polyimide film is prepared as follows:
polyimide is dissolved in organic solution acetone to form film-forming slurry, the slurry is then dripped on a film, and the film is placed on a heating table for annealing at 350-400 ℃ for 45-60 minutes to obtain a polyimide film, wherein the annealing temperature and the annealing time are critical to the water absorption expansion performance of the polyimide film; neither the heating temperature nor the annealing time is too low nor the swelling phenomenon is exhibited.
Preparing a packaging layer:
the packaging layer is prepared by mixing a PDMS material and a carboxymethyl chitosan cross-linking agent. The preparation method of the packaging layer comprises the following specific steps:
uniformly mixing PDMS and carboxymethyl chitosan cross-linking agent according to a certain proportion to obtain packaging layer mixed liquor, preparing film form packaging layer on the obtained sample by means of spin coating or knife coating process, and heating and annealing.
Specifically, uniformly mixing PDMS stock solution and carboxymethyl chitosan cross-linking agent according to the mass ratio of 10:1 to form a mixed solution, placing the mixed solution into a vacuum box to remove bubbles generated in the mixed solution, then spin-coating or knife-coating the mixed solution on a ZnO nano rod functional layer, and then placing a sample in a vacuum environment to anneal for at least 24 hours at the temperature of 60-80 ℃, thereby coating and preparing the packaging layer in a film form on the ZnO nano rod functional layer.
According to the prepared flexible self-powered humidity sensor based on zinc oxide piezoelectric effect, performance test is carried out according to the method disclosed in the field. The specific method comprises the following steps: the voltage signals of the prepared flexible self-powered humidity sensor based on zinc oxide piezoelectricity are collected by using a universal meter and uploaded to a computer, different humidity environments are obtained by a bubbling method, and the bubbling method humidity testing system mainly comprises a humidity adjusting module, a humidity calibrating module and an experimental data recording module, as shown in fig. 4. The humidity adjusting module consists of a valve, a gas flowmeter and flowing dry and wet nitrogen. The valve is used for controlling the flow of nitrogen, and the magnitude of the flow of the nitrogen is manually controlled through the indication of the gas flow meter; after passing through the flask with water, the nitrogen can introduce water vapor into the test box and improve the relative humidity in the test box, and the nitrogen is introduced into the test box to reduce the relative humidity in the test box, so that the effective adjustment range of the relative humidity in the test box is 10-90%. The humidity calibration module consists of a commercial hygrometer, a test box and a computer. The commercial hygrometer is connected with a computer and used for detecting the humidity inside the test box and displaying the humidity in real time. The experimental data recording module consists of a universal meter and a computer. The universal meter is connected with the flexible self-powered humidity sensor to be tested and is used for monitoring voltage signals generated by the sensor in real time and uploading the signals to a computer so as to realize real-time monitoring and recording. When the humidity is 10%, the voltage output of the device is 100-150 mV, and when the humidity in the test box is 90%, the voltage output of the device is 800-900 mV; when the humidity is controlled to be increased from 10% to 90% by the humidity adjusting module, the recovery voltage output curve of the sensor can be increased from 100 mV to 150mV to 800 mV to 900mV within 5-10 seconds; when humidity is controlled to be reduced from 90% to 10% by the humidity adjusting module, the recovery voltage output curve of the sensor can be reduced from 800-900 mV to 100-150 mV within 5-10 s, and the process voltage changes linearly with the humidity.
The flexible self-powered humidity sensor based on zinc oxide piezoelectricity and the preparation method thereof can be effectively attached to curved leaf surfaces, an external power supply system is not needed, namely, moisture in a plant growth environment is spontaneously adsorbed to generate voltage, and the sensor is low in later maintenance cost and environment-friendly. Meanwhile, the invention improves the response and recovery speed of the humidity sensor by utilizing the characteristic that the polyimide material swells under different humidity environments and has high response and recovery speed.
In addition, the flexible self-powered humidity sensor based on zinc oxide piezoelectricity converts the moisture information in the plant growth environment into a voltage signal, so that the monitoring of the moisture information in the plant growth environment is realized, the purpose of mastering the condition of the plant growth environment is further achieved, the rapid development of intelligent agriculture is promoted, the crop yield and quality are improved, the economic benefit is ensured, and the agricultural water is saved through reasonable irrigation.
The foregoing has been described schematically the invention and embodiments thereof, which are not limiting, but are capable of other specific forms of implementing the invention without departing from its spirit or essential characteristics. The drawings are also intended to depict only one embodiment of the invention, and therefore the actual construction is not intended to limit the claims, any reference number in the claims not being intended to limit the claims. Therefore, if one of ordinary skill in the art is informed by this disclosure, a structural manner and an embodiment similar to the technical scheme are not creatively designed without departing from the gist of the present invention, and all the structural manners and the embodiment are considered to be within the protection scope of the present patent. In addition, the word "comprising" does not exclude other elements or steps, and the word "a" or "an" preceding an element does not exclude the inclusion of a plurality of such elements. The various elements recited in the product claims may also be embodied in software or hardware. The terms first, second, etc. are used to denote a name, but not any particular order.
Claims (10)
1. The utility model provides a flexible self-powered humidity transducer based on zinc oxide piezoelectricity, includes flexible substrate, positive electrode, first functional layer, negative electrode, second functional layer and encapsulation layer, its characterized in that:
the positive electrode is integrated on the flexible substrate, the first functional layer is integrated on the positive electrode, the negative electrode is integrated on the first functional layer, the second functional layer is prepared on the negative electrode, and the positive electrode and the negative electrode are of vertical structures.
2. The flexible self-powered humidity sensor of claim 1 wherein:
wherein the flexible substrate, the positive electrode, the second functional layer and the packaging layer are all in a flexible film form.
3. The flexible self-powered humidity sensor of claim 1 wherein:
the flexible substrate is made of a flexible polymeric material.
4. A flexible self-powered humidity sensor according to claim 3 wherein:
the flexible polymer material adopts PET.
5. A method of manufacturing a flexible self-powered humidity sensor based on zinc oxide piezoelectricity as claimed in any one of claims 1-4, comprising the steps of:
preparing a flexible substrate and a first functional layer:
sputtering a transparent Indium Tin Oxide (ITO) conductive film coating on a PET base material, performing high-temperature annealing treatment to obtain a flexible substrate, and growing and preparing ZnO nano rods by a hydrothermal method to obtain a first functional layer;
preparing a positive electrode and a negative electrode:
the positive electrode and the negative electrode are composed of ITO and carbon nanotube materials, and the ITO electrode is integrated on the substrate PET;
preparing a second functional layer:
the second functional layer is made of polyimide material;
preparing a packaging layer:
the packaging layer is prepared by mixing PDMS material and carboxymethyl chitosan cross-linking agent, uniformly mixing PDMS and carboxymethyl chitosan cross-linking agent according to a proportion to obtain packaging layer mixed solution, preparing a film-shaped packaging layer on the obtained film growing with ZnO nano-rods through spin coating or knife coating technology, and heating and annealing.
6. The method of manufacturing according to claim 5, wherein:
the preparation method of the flexible substrate comprises the following steps:
cutting a PET-ITO film and fixing the PET-ITO film on a glass slide by using a double-sided adhesive tape;
placing the fixed PET-ITO film into a plasma etching machine to clean the surface of the substrate to obtain a hydrophilic ITO surface;
growing ZnO nano rods on the PET-ITO film substrate subjected to plasma cleaning by adopting a hydrothermal growth method;
taking down the PET-ITO film growing with the ZnO nano-rods, and repeatedly flushing with deionized water, wherein the treated PET-ITO film growing with the ZnO nano-rods is taken as a sample;
the sample is put on a heating table to be annealed at 80 ℃ to dry the sample or the sample is dried by nitrogen.
7. The method of manufacturing according to claim 6, wherein:
the first functional layer is ZnO nano-rod prepared by hydrothermal growth, and the preparation of the first functional layer comprises the following steps:
weighing anhydrous zinc acetate, preparing an anhydrous zinc acetate solution with the concentration of 10mmol/L, and adopting absolute ethyl alcohol as a solvent; weighing zinc nitrate hexahydrate, and preparing an equimolar mixed solution of the zinc nitrate hexahydrate and the hexamethylenetetramine by using deionized water as a solvent;
spin-coating 0.15mL of zinc acetate solution on an ITO substrate at 1500rpm for 45s, then heating and annealing on a heating table at 140-150 ℃ for 2-3 minutes, and repeating the actions for 10 times to obtain a seed crystal layer;
reversely immersing PET-ITO coated with a seed crystal layer after spin coating into a mixed solution of zinc nitrate hexahydrate and hexamethylenetetramine for 4-6 hours to grow ZnO nano rods;
and taking the prepared sample out of the growth liquid, flushing the sample with deionized water, and then placing the sample on a heating table for annealing and drying or drying the sample with nitrogen.
8. The method of manufacturing according to claim 7, wherein:
the preparation of the positive electrode and the negative electrode comprises the following steps:
attaching the annealed PET-ITO film with the ZnO nanorods growing thereon to an interdigital electrode mask, placing the mask on a heating table, and spraying a carbon nanotube electrode by a spray gun while heating to prepare a carbon nanotube electrode;
the electrode spraying preparation process is as follows:
mixing the carbon nano tube conductive paint with deionized water according to the weight ratio of 1: and uniformly mixing the components according to the mass ratio of 20 to form a carbon nanotube suspension, filling the mixed carbon nanotube suspension into a spray gun, and spraying the carbon nanotube suspension onto a film attached to the interdigital electrode mask for 20-30 minutes to obtain the carbon nanotube interdigital electrode.
9. The method of manufacturing according to claim 8, wherein:
the preparation of the second functional layer comprises the following steps:
taking down the sample of the spray electrode from the heating table, taking down the interdigital electrode mask plate, uniformly dripping polyimide solution on the surface of the sample, and then putting the sample on the heating table again for annealing to obtain a polyimide film, namely the second functional layer;
the polyimide film is prepared as follows:
and dissolving polyimide in organic solution acetone to form film-forming slurry, then dripping the slurry on a film, and placing the film-forming slurry on a heating table for annealing to obtain the polyimide film.
10. The method of manufacturing according to claim 9, wherein:
the preparation method of the packaging layer comprises the following steps:
uniformly mixing PDMS and carboxymethyl chitosan cross-linking agent according to a certain proportion to obtain packaging layer mixed liquor, preparing film form packaging layer on the obtained sample by means of spin coating or knife coating process, and heating and annealing.
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| CN117589833A (en) * | 2024-01-18 | 2024-02-23 | 中国矿业大学 | Self-powered low-humidity sensor and preparation method thereof |
| CN117589833B (en) * | 2024-01-18 | 2024-04-16 | 中国矿业大学 | Self-powered low-humidity sensor and preparation method thereof |
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