CN109613075B - Flexible humidity sensor based on fibroin and preparation method thereof - Google Patents
Flexible humidity sensor based on fibroin and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a flexible humidity sensor based on fibroin and a preparation method thereof. The fibroin film has the unique characteristic of selective adsorption to water molecules, can detect the existence of liquid water molecules, and can even distinguish the liquid water molecules from the gaseous water molecules in specific occasions. Therefore, the flexible humidity sensor of the present invention can be used to detect whether the environment contains liquid water molecules, and further, can distinguish the existence of liquid water molecules from gaseous water molecules in some specific situations.
Description
Technical Field
The invention relates to the field of sensors, in particular to a fibroin-based flexible humidity sensor and a preparation method thereof.
Background
The humidity sensor is a sensor for detecting the humidity of the external environment, and generally, the humidity sensor is classified into a capacitive type, a resistive type, a piezoresistive type, an optical type, and the like, and more commonly, the capacitive type and the resistive type are used. Humidity sensors have important applications in a wide variety of fields, such as weather, military, agricultural, industrial control, precision measurement equipment, medical equipment, and the like. However, most of the traditional humidity sensors are made of silicon-based materials, have the characteristics of high rigidity and easiness in breaking, and cannot be bent and deformed according to application scenes, so that the application range of the traditional humidity sensors is limited.
In recent decades, with the rapid development of flexible electronic technology, more and more flexible sensors have been designed. Due to the importance of humidity detection in many fields such as health and environmental monitoring, flexible humidity sensors are receiving more and more attention. In recent years, flexible humidity sensors constructed using polymer materials have been reported based on resistive and capacitive principles. A paper Design and optimization of an ultra thin flexible capacitive humidity sensor published in the International famous journal Sensors & Actuators B Chemical discloses a capacitive-based flexible humidity sensor, and a paper Novel flexible resistive-type humidity sensor published in the journal discloses a resistive-based flexible humidity sensor. The chinese patent application with application number 201810182699.6 discloses a flexible humidity sensor and a method for making the same. However, the humidity sensor disclosed so far responds to both gas and liquid water molecules, since both of them adsorb water molecules to change their capacitance or resistance. Therefore, it is difficult for the conventional humidity sensor to distinguish the presence form of water in the air. For example, a conventional humidity sensor may respond significantly to exhaled air, but cannot predict whether it contains liquid water. For example, in a foggy day, the air contains a large amount of liquid water, and the traditional humidity sensor cannot detect the concentration of the liquid water in the air. This result is determined by the characteristics of the humidity-sensitive material, and the three disclosed humidity sensors respectively employ, as the humidity-sensitive material, three materials of bis-benzocyclobutene, methyl methacrylate, and 3- (methacrylamido) propyltrimethylammonium chloride polymer, and a polyvinyl alcohol film, which are all humidity sensors based on chemical reactions, and react with both gaseous water molecules and liquid water. Therefore, none of the three disclosed flexible humidity sensors can distinguish the existence form of water molecules in the air, and specifically, cannot detect whether liquid water exists in the air, which limits the application scenarios.
Disclosure of Invention
The invention aims to provide a fibroin-based flexible humidity sensor, which solves the problem that the existing flexible humidity sensor cannot identify the existence form of water molecules in air.
In addition, the invention also provides a preparation method of the flexible humidity sensor.
The invention is realized by the following technical scheme:
the utility model provides a flexible humidity transducer based on fibroin, includes flexible base, interdigital electrode and wet quick material, the interdigital electrode is located between flexible base and the wet quick material, wet quick material is the fibroin film.
Current humidity sensors mainly include resistive humidity sensors and capacitive humidity sensors. The flexible humidity sensor of the present invention is based on capacitive. The capacitive humidity sensor is generally made of a polymer film capacitor, and commonly used polymer materials include polystyrene, polyimide, cellulose acetate butyrate and the like. When the environmental humidity changes, the dielectric constant of the humidity sensitive capacitor changes, so that the capacitance of the humidity sensitive capacitor also changes, and the capacitance change quantity of the humidity sensitive capacitor is in direct proportion to the relative humidity. However, the accurate detection of the environmental humidity is still a scientific problem, and the humidity sensors made of the materials cannot distinguish gaseous water molecules and liquid water molecules in the air, and the liquid water molecules and the gaseous water molecules in the air can enable the existing humidity sensors to generate response.
The fibroin film is fibroin, and the unique characteristic of selective adsorption of the fibroin to water molecules enables the fibroin film to detect the existence of liquid water molecules and even distinguish the liquid water molecules from gaseous water molecules in specific occasions. The fibroin is a biocompatible natural polymer material, and the fibroin film is prepared by the fibroin in a spin coating mode. The interdigital electrode is a commonly used electrode pattern, and the interdigital electrode is used as the electrode pattern, so that the length of the electrode can be prolonged, and the humidity sensor is more sensitive.
The working principle of the invention is as follows:
when the humidity sensor is exposed in air with high humidity, the fibroin film (humidity sensitive material) can absorb water molecules in the air, and the dielectric constant of the humidity sensitive material is increased, so that the capacitance between interdigital electrodes is increased; conversely, when the humidity sensor is exposed to air with low humidity, the fibroin film desorbs water molecules in the fibroin material, and the dielectric constant of the humidity-sensitive material decreases, thereby resulting in a decrease in inter-interdigital electrode capacitance. More importantly, the fibroin film has selectivity for water molecule adsorption, gaseous water molecules in the air cannot be absorbed by fibroin, and liquid water molecules in the air can be rapidly absorbed by fibroin (as shown in fig. 3 and 4), in other words, fibroin only responds to liquid water molecules. Therefore, the flexible humidity sensor of the present invention can be used to detect whether the environment contains liquid water molecules, and further, can distinguish the existence of liquid water molecules from gaseous water molecules in some specific situations.
The invention adopts the natural high molecular material fibroin film which is biocompatible to biology as the humidity sensitive material of the humidity sensor, and the unique characteristic of selective adsorption of the fibroin film to water molecules enables the fibroin film to detect the existence of liquid water molecules and even distinguish the liquid water molecules from the gaseous water molecules in specific occasions. Therefore, the invention solves the problem that the existing flexible humidity sensor can not identify the existence form of water molecules in the air.
Further, the flexible humidity sensor can distinguish liquid water molecules from gaseous water molecules in the environment.
Further, the flexible substrate is a polydimethylsiloxane polymer substrate.
The polydimethylsiloxane polymer substrate has good flexibility.
Further, the polydimethylsiloxane polymer substrate is manufactured into regular stripes on the surface matched with the interdigital electrodes in a reverse mode.
I.e. regular stripes are provided in the mould.
Preferably, the regular stripes are 100 μm wide and 50 μm high, and the polydimethylsiloxane polymer substrate is 65 x 30 x 1mm in size3。
The invention can effectively increase the surface area of the polydimethylsiloxane polymer substrate by arranging the regular stripes on the polydimethylsiloxane polymer substrate, thereby greatly increasing the contact surface area of the humidity-sensitive material between the outside and the interdigital electrode and improving the sensitivity of the flexible humidity sensor.
Furthermore, the interdigital electrode is a graphite interdigital electrode, an extraction area of the electrode is reserved on the interdigital electrode, and the area of the extraction area is 5 × 5mm2。
The graphite interdigital electrode has good conductivity and low price, and the raw materials are easy to obtain.
Further, the graphite interdigital electrode is prepared by adopting a screen printing technology.
The screen printing technology is a mature process with the characteristics of universality, mass production, low cost and the like.
The ink with the graphite as the main component is used as the material for preparing the electrode, has economic benefit, can be easily processed on a large scale by matching with a screen printing technology, and solves the problem of large-scale preparation.
Further, the interdigital electrode comprises N interdigital overlapping units, wherein N is a positive integer greater than or equal to 1, and the effective overlapping length of each interdigital overlapping unit is 14.4-14.8 mm.
The distance between the reserved area and the interdigital electrode is 2mm, 2 lead-out areas are arranged, the 2 lead-out areas are bilaterally symmetrical, and the thickness of the reserved area is the same as that of the interdigital electrode.
Preferably, the width of the interdigital electrode is 500 μm, the interdigital length of the interdigital electrode is 15mm, and the gap of the interdigital electrode is 200-600 μm.
Further, the silk protein film completely covers the interdigital electrodes.
Preferably, the thickness of the fibroin film is 3-9 μm, and the length and width of the fibroin film are 45mm and 20mm, respectively.
A preparation method of a fibroin-based flexible humidity sensor comprises the following steps:
1) preparing a flexible substrate: adopting polydimethylsiloxane polymer to obtain a flexible substrate through 3D printing mould reverse mould;
specifically, first, the mold was drawn by SOLIDWORKS graphic software with a peripheral dimension of 75 × 3.5mm3Slot size 65 x 1mm3The bottom of the groove is provided with regular stripes, the width of the regular stripes is 100 mu m, the height of the regular stripes is 50 mu m, and then the mould is printed by a high-precision 3D printer.
Then, the ratio of base fluid and crosslinking agent 10: 1 to obtain liquid Polydimethylsiloxane (PDMS), pouring the PDMS into a printing mold, and then placing the PDMS into an oven at 80 ℃ for curing.
2) Preparing an interdigital electrode: printing ink with graphite as main component on a flexible substrate right below the mesh;
specifically, firstly, a screen plate mesh graph is drawn through CORELDRAW drawing software, wherein regular holes are formed in a screen plate, and the regular holes are electrode patterns to be printed. Then, enabling an agent to produce a screen printing plate;
the prepared flexible PDMS substrate is then placed directly under the mesh in a screen printing screen, preferably with a screen printing screen and flexible PDMS substrate spacing of 300 μm. Then pouring ink with the main component of graphite on a screen printing plate, scraping the ink through meshes with electrode patterns by using a scraper, then printing the conductive ink on a flexible PDMS substrate, and finally putting the flexible PDMS substrate into an oven at 80 ℃ for drying.
3) And preparing the fibroin film: and spin-coating the fibroin solution on the polydimethylsiloxane polymer substrate printed with the graphite interdigital electrode, and drying.
According to the invention, a natural pollution-free fibroin material is introduced as a humidity sensitive material for the first time, and fibroin is a natural protein and is completely harmless to a human body, so that the application range of the flexible humidity sensor is greatly expanded, and the flexible humidity sensor is integrated into wearable equipment.
The invention applies the screen printing technology to the preparation of the humidity sensor electrode for the first time, and the technology is a universal processing technology which can be produced in batch and has low cost.
The invention adopts graphite with low price and good conductivity as an electrode. All the materials are easy to obtain, the cost is low, the manufacture is simple, the flexible humidity sensor is beneficial to large-scale production, and the applicable range is enlarged. It is worth mentioning that the dimensions involved in the present invention are all adjustable, and the overall dimensions can be at least less than 5 x 0.5mm due to the simple and easy handling of the preparation steps3The method can be applied to some small-sized scenes.
Further, the preparation method of the fibroin solution comprises the following steps:
a) and extracting fibroin: shearing silkworm cocoon shells, putting the cut silkworm cocoon shells into a boiling sodium carbonate solution for 45-60 minutes, taking out the silk protein, washing the silk protein by using deionized water, and drying the silk protein;
b) and dissolving fibroin: adding a lithium bromide solution with the mass volume ratio of 20% into the dried fibroin, and putting the solution into an oven for 4 hours to obtain a fibroin-lithium bromide solution;
c) and (3) fibroin dialysis: pouring the fibroin-lithium bromide solution into a dialysis bag, and then putting the dialysis bag filled with the fibroin-lithium bromide solution into deionized water for dialysis for 48 hours;
d) and filtering the fibroin: the fibroin solution after dialysis was filtered twice with a 5 μm pore size millipore filter to obtain a fibroin solution.
Preferably, a circle of transparent adhesive tape is attached to the polydimethylsiloxane flexible substrate printed with the graphite interdigital electrode, and the size of the inner circle is 45-20 mm2Then, uniformly placing the filtered and purified fibroin solution on a polydimethylsiloxane flexible substrate pasted with an adhesive tape by using a glass rod; and (3) drying the device coated with the fibroin solution in an oven at 60 ℃ for 30 minutes, taking out the device, and removing the transparent adhesive tape.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. the invention adopts the natural high molecular material fibroin film which is biocompatible to biology as the humidity sensitive material of the humidity sensor, and the fibroin film has the unique characteristic of selective adsorption to water molecules, so that the existence of the liquid water molecules can be detected, and even the liquid water molecules and the gaseous water molecules can be distinguished in specific occasions. Therefore, the invention solves the problem that the existing flexible humidity sensor can not identify the existence form of water molecules in the air.
2. The polydimethylsiloxane polymer is used as the substrate, so that the flexible humidity sensor has good flexibility, is easy to prepare, can be prepared in a large scale, and is subjected to regular stripe treatment on the surface of the flexible substrate, so that the contact surface area is greatly increased, and the sensitivity of the flexible humidity sensor is improved.
3. According to the invention, a natural pollution-free fibroin material is introduced as a humidity sensitive material for the first time, and fibroin is a natural protein and is completely harmless to a human body, so that the application range of the flexible humidity sensor is greatly expanded, and the flexible humidity sensor is integrated into wearable equipment. The screen printing technology is applied to the preparation of the humidity sensor electrode for the first time, and the technology is a universal processing technology which can be produced in batch and has low cost. And graphite with low price and good conductivity is used as an electrode. All the materials are easy to obtain, the cost is low, the manufacture is simple, the flexible humidity sensor is beneficial to large-scale production, and the applicable range is enlarged.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:
FIG. 1 is a perspective view of a flexible humidity sensor;
FIG. 2 is an exploded view of the flexible humidity sensor;
FIG. 3 is a graph of the response of the flexible humidity sensor of the present invention to liquid water molecules;
FIG. 4 is a graph of the response of the flexible humidity sensor of the present invention to gaseous water molecules.
Reference numbers and corresponding part names in the drawings:
1-flexible substrate, 2-interdigital electrode, 3-reserved area, 4-humidity sensitive material.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.
Example 1:
as shown in fig. 1 and fig. 2, a flexible humidity sensor based on fibroin comprises a flexible substrate 1, interdigital electrodes 2 and a humidity-sensitive material 4, wherein the interdigital electrodes 2 are located between the flexible substrate 1 and the humidity-sensitive material 4, and the humidity-sensitive material 4 is a fibroin film; the flexible substrate 1 is made of an existing flexible material.
The flexible humidity sensor in the invention is based on a capacitance mechanism, so that an instrument for measuring capacitance is required to measure the flexible humidity sensor. In the embodiment, the manufactured flexible humidity sensor is measured by using the LCR bridge which is produced at the same cost. It should be mentioned that, preferably, for the convenience of measurement, the electrodes need to be led out from the reserved areas of the graphite interdigital electrodes by copper wires before measurement. In order to quantitatively change the humidity of the environment, a flexible humidity sensor to be measured is placed in a closed transparent box, and the environment is humidified by a commercial humidifier. For this embodiment, it is necessary to perform a comparative measurement in an environment filled with liquid and gaseous water molecules, respectively. Thus, two different humidifiers are required to humidify the enclosed environment. The liquid humidifier has the principle of ultrasonic humidification, the ultrasonic humidifier mainly adopts high-frequency oscillation, water in the humidifier is thrown away from the water surface through the high-frequency oscillation of the atomizing sheet to generate elegant water mist, the purpose of humidification is achieved, and the nature of the sprayed water mist is liquid water molecules. Then a gaseous humidifier, which uses cold evaporation technology. The principle is that the evaporation of water is accelerated by a fan and is filtered by a nano filter screen, and the evaporated water vapor is gaseous water molecules essentially.
The manufactured flexible humidity sensor is placed in a closed transparent box, the two humidifiers are respectively adopted to humidify a closed environment, and the variation trend of the response curve of the two humidifiers is compared. As shown in fig. 3, the fabricated flexible humidity sensor has a significant response to liquid water molecules. In fig. 3, the first 30 seconds are areas where the humidifier works, the capacitance of the flexible humidifier rises obviously, the humidification stops at 30 seconds, and the capacitance of the flexible humidity sensor drops rapidly when the humidity sensor is taken out to the ordinary environment. The reason for taking out the humidity sensor is because the closed environment is already filled with liquid water molecules, which can affect desorption of the humidity sensor. During the movement, the capacitance tends to change excessively.
Fig. 4 is a response curve of the manufactured flexible humidity sensor to gaseous water molecules, and it can be seen that the curve has no change trend, and similarly, the first 30 seconds are areas where the humidifier works, and the humidification is stopped at 30 seconds. At this time, the value of the general commercial humidity sensor is already higher than 90%, but the flexible humidity sensor according to the present invention does not have any change to the gaseous water molecules.
As can be seen from fig. 3 and 4, the humidity sensor of the present invention has a rapid response to liquid water molecules, but no response to gaseous water molecules. Therefore, the flexible humidity sensor can detect whether liquid water molecules exist in the environment or not, and further can distinguish the existence of the liquid water molecules from the existence of the gas water molecules in some specific occasions.
Example 2:
as shown in fig. 1 and fig. 2, the present embodiment is based on example 1, and the flexible substrate 1 is a polydimethylsiloxane polymer substrate; the polydimethylsiloxane polymer substrate is manufactured into regular stripes on one surface matched with the interdigital electrodes 2 in a reverse mode; the interdigital electrode 2 is a graphite interdigital electrode; the graphite interdigital electrode is prepared by adopting a screen printing technology; the interdigital electrode 2 comprises N interdigital overlapping units, N is a positive integer which is greater than or equal to 1, and the effective overlapping length of each interdigital overlapping unit is 14.4-14.8 mm; an electrode lead-out area 3 is reserved on the interdigital electrode 2, and the area of the lead-out area 3 is 5 × 5mm2(ii) a The fibroin film completely covers the interdigital electrode 2, and specifically, the area of the fibroin film is 45 × 20mm2The silk protein film thickness be 3 mu m, graphite interdigital electrode indicate that length is 15mm, graphite interdigital electrode's clearance be 200 mu m, graphite interdigital electrode's width be 500 mu m, flexible substrate 1 thickness is 1mm, length is 65mm, the width is 30 mm.
A preparation method of a fibroin-based flexible humidity sensor comprises the following steps:
1) preparing the flexible substrate 1: the mold was first drawn by SOLIDWORKS graphic software with a peripheral dimension of 75 x 3.5mm3Slot size 65 x 1mm3The bottom of the groove is provided with regular stripes, the width of each regular stripe is 100 micrometers, the height of each regular stripe is 50 micrometers, then a high-precision 3D printer is used for printing a mould and then reversing the mould, Polydimethylsiloxane (PDMS) needs to be blended, and the ratio of the base liquid to the cross-linking agent is preferably 10: 1 in a ratio of 90mm in a culture dish to prepare liquid Polydimethylsiloxane (PDMS), pouring the liquid Polydimethylsiloxane (PDMS) into a printed mould, then putting the mould into an oven at 80 ℃ for curing, and then taking out the cured Polydimethylsiloxane (PDMS);
2) preparing an interdigital electrode 2: printing ink with graphite as a main component on a flexible substrate 1 right below a mesh, wherein the basic principle of screen printing is as follows: the basic principle that the meshes of the image-text part of the screen printing plate are ink-permeable and the meshes of the non-image-text part are ink-impermeable is utilized for printing, wherein the image-text of the screen printing plate is the interdigital electrode pattern. When printing, graphite ink as main component is poured into one end of the screen plate, and a scraping scraper plate is used to apply a certain pressure on the ink part on the screen plate and move towards the other end of the screen plate. The ink is squeezed from the mesh of the graphic part onto a Polydimethylsiloxane (PDMS) substrate by a squeegee while moving. The printing mark is fixed in a certain range due to the viscous action of the printing ink, the scraper is always in line contact with the screen and the Polydimethylsiloxane (PDMS) substrate in the printing process, the contact line moves along with the movement of the scraper, and a certain gap is kept between the screen and the PDMS substrate, so that the screen generates a reaction force to the scraper through the self tension in the printing process, and the reaction force is called as a rebound force. Due to the action of the resilience force, the screen is only in movable line contact with the Polydimethylsiloxane (PDMS) substrate, and other parts of the screen are separated from the Polydimethylsiloxane (PDMS) substrate. The ink and the silk screen are fractured, the printing size precision is ensured, and the smearing of printing stocks is avoided. When the scraper scrapes the whole page, the screen plate is lifted, and the printing ink is slightly scraped back to the initial position. This is now a print stroke. Regarding the production of the screen plate, a screen plate mesh pattern of a printing screen plate is drawn through CORELDRAW drawing software, regular holes are formed in the screen plate, namely the interdigital electrode patterns to be printed, then a screen printing screen plate is produced by an agent, the produced flexible PDMS substrate is placed right below the mesh holes in the screen printing screen plate, and preferably, the distance between the screen printing screen plate and the flexible PDMS substrate is 300 mu m. Then pouring ink with the main component of graphite on a screen printing plate, scraping the ink through meshes with electrode patterns by using a scraper, then printing the conductive ink on a flexible PDMS substrate, and finally putting the flexible PDMS substrate into an oven at 80 ℃ for drying;
3) and preparing the fibroin film: spin-coating fibroin solution on a polydimethylsiloxane polymer substrate printed with a graphite interdigital electrode, drying, and preferably pasting a circle of transparent adhesive tape on the polydimethylsiloxane flexible substrate printed with the graphite interdigital electrode in order to ensure the regularity of the spin-coated humidity-sensitive material, wherein the size of an inner circle is 45 x 20mm2. And then uniformly putting the filtered and purified fibroin solution on a polydimethylsiloxane flexible substrate pasted with an adhesive tape by using a glass rod. Putting the device coated with the fibroin solution into a drying oven at 60 ℃ for drying for 30 minutes, taking out the device, and removing the transparent adhesive tape to obtain the egg fibroin film;
specifically, the preparation method of the fibroin solution comprises the following steps:
a) and extracting fibroin: preparation of 0.02mol/L sodium carbonate (Na)2CO3) The solution, preferably, the solvent is deionized water. Then the obtained sodium carbonate (Na)2CO3) Heating the solution to boiling; cutting silkworm cocoon shell, adding boiling sodium carbonate (Na)2CO3) Adding the solution, preferably, continuously boiling for 45 minutes, stirring with a glass rod for multiple times during boiling, taking out the fibroin after 45 minutes, washing with deionized water for 5 times, and drying;
b) and dissolving fibroin: a solution corresponding to 9.3mol/L of lithium bromide (LiBr) was prepared. Preferably, the volume of the lithium bromide (LiBr) solution is 5 times of that of the dried fibroin; putting the dried fibroin into a small 50ml beaker, pouring the prepared lithium bromide (LiBr) solution, and then putting the solution into a 60 ℃ oven to dissolve for 4 hours;
c) and (3) fibroin dialysis: and (3) sealing the dialysis bag and putting the dialysis bag into deionized water for 10 minutes, then transferring the fibroin-lithium bromide solution into the dialysis bag by using an injector, sealing the dialysis bag again and putting the dialysis bag into the deionized water for dialysis. Preferably, the dialysis session is changed 5 times with water at 2 hours, 4 hours, 16 hours, 28 hours and 40 hours, respectively;
d) and filtering the fibroin: filtering the obtained fibroin solution after dialysis for 2 times with microporous filter to obtain fibroin solution, preferably with pore diameter of 5 μm.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. The utility model provides a flexible humidity transducer based on fibroin, includes flexible base (1), interdigital electrode (2) and humidity sensitive material (4), interdigital electrode (2) are located between flexible base (1) and humidity sensitive material (4), its characterized in that, humidity sensitive material (4) are the fibroin film, the preparation method of fibroin film is as follows: and (3) directly spin-coating the fibroin solution on the flexible substrate (1) provided with the interdigital electrode (2) and drying.
2. A fibroin-based flexible humidity sensor according to claim 1, wherein said flexible humidity sensor is capable of distinguishing between liquid and gaseous water molecules in the environment.
3. A fibroin-based flexible humidity sensor according to claim 1, characterized in that said flexible substrate (1) is a polydimethylsiloxane polymer substrate.
4. A flexible fibroin-based humidity sensor according to claim 3, characterized in that said polydimethylsiloxane polymer substrate is reverse-molded to produce regular stripes on the surface cooperating with the interdigital electrodes (2).
5. A fibroin-based flexible humidity sensor according to claim 1, characterized in that said interdigital electrode (2) is a graphite interdigital electrode, said interdigital electrode (2) is reserved with an electrode lead-out area (3), said lead-out area (3) has an area of 5 x 5mm2。
6. A fibroin-based flexible humidity sensor according to claim 5, wherein said graphite interdigitated electrodes are prepared by screen printing.
7. A fibroin-based flexible humidity sensor according to claim 1, characterized in that said interdigital electrode (2) comprises N interdigital overlapping elements, N being a positive integer greater than or equal to 1, each of said interdigital overlapping elements having an effective overlapping length of 14.4-14.8 mm.
8. A fibroin-based flexible humidity sensor according to claim 1, characterized in that said fibroin film completely covers the interdigital electrodes (2).
9. A method for preparing a fibroin-based flexible humidity sensor according to any one of claims 1-8, comprising the steps of:
1) preparing a flexible substrate (1): adopting polydimethylsiloxane polymer, and obtaining a flexible substrate (1) through 3D printing mould reverse mould;
2) preparing an interdigital electrode (2): printing ink with graphite as a main component on a flexible substrate (1) right below a mesh by a screen printing technology;
3) and preparing the fibroin film: and spin-coating the fibroin solution on the polydimethylsiloxane polymer substrate printed with the graphite interdigital electrode, and drying.
10. A method for preparing a fibroin-based flexible humidity sensor as claimed in claim 9, wherein the fibroin solution is prepared by a method comprising the steps of:
a) and extracting fibroin: shearing silkworm cocoon shells, putting the cut silkworm cocoon shells into a boiling sodium carbonate solution for 45-60 minutes, taking out the silk protein, washing the silk protein by using deionized water, and drying the silk protein;
b) and dissolving fibroin: adding a lithium bromide solution with the mass volume ratio of 20% into the dried fibroin, and putting the solution into an oven for 4 hours to obtain a fibroin-lithium bromide solution;
c) and (3) fibroin dialysis: pouring the fibroin-lithium bromide solution into a dialysis bag, and then putting the dialysis bag filled with the fibroin-lithium bromide solution into deionized water for dialysis for 48 hours;
d) and filtering the fibroin: the fibroin solution after dialysis was filtered twice with a 5 μm pore size millipore filter to obtain a fibroin solution.
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| CN108414584A (en) * | 2018-03-05 | 2018-08-17 | 北京化工大学 | A kind of preparation method of flexible, wearable moisture sensor and its application in breathing detection |
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