CN112924316A - Humidity-sensitive film based on chitosan and polypyrrole and preparation method and application thereof - Google Patents
Humidity-sensitive film based on chitosan and polypyrrole and preparation method and application thereof Download PDFInfo
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Abstract
The invention relates to the technical field of humidity-sensitive materials, in particular to a humidity-sensitive film based on chitosan and polypyrrole and a preparation method and application thereof. The humidity-sensitive film is a composite humidity-sensitive film based on Chitosan (CS) and polypyrrole (PPy), and the CS/PPy composite humidity-sensitive film is of a porous, high-specific-surface-area, laminated and staggered incomplete coating structure. The prepared CS/PPy-QCM humidity sensor. The obtained sensor has the advantages of high sensitivity (52.91 Hz/% RH), low wet hysteresis (1.68% RH), short response/recovery time (4s/2s), good selectivity, good repeatability and stability and the like. The invention constructs a human breath detection system. According to the system, a breathing mask constructed by a humidity sensor is used for sensing a breathing humidity signal, a QCM tester is used for collecting signals, an App with a human-computer interaction interface is used for extracting characteristic parameters of the breathing signal as required, the breathing type is judged, the breathing frequency is calculated, a corresponding breathing type detection report is generated, and the potential breathing monitoring value is displayed.
Description
Technical Field
The invention relates to the technical field of humidity-sensitive materials, in particular to a humidity-sensitive film based on chitosan and polypyrrole and a preparation method and application thereof.
Background
Humidity is an important physical parameter for measuring the dryness and humidity of air, and is closely related to the production and life of human beings. On the one hand, the humidity has important significance for industrial and agricultural production, food industry, drug storage and biomedicine. Too high humidity can cause the durability and safety of the electrical equipment to be reduced, and can also accelerate the growth of bacteria and the mildew of food; too low a humidity can cause electrostatic interference and also can lead to reduced yield of crops. On the other hand, the environmental humidity also has a significant impact on human health. Research shows that when the environmental humidity is too low, respiratory diseases such as asthma, bronchitis and the like are easily caused; when the environmental humidity is too high, rheumatoid arthritis is easily caused. Therefore, the requirement of humidity detection is wide, and the research of the rapid and accurate humidity sensor has important significance.
The normal respiratory frequency of an adult in a resting state is 12-20Hz/min, and the period of each respiration is 3-5 s. Abnormal breathing can be divided into respiratory rate abnormalities including tachypnea (respiratory rate >24Hz/min) and bradypnea (respiratory rate <10Hz/min) respiratory rhythm abnormalities including cheyne-stokes breathing and diopsis. At present, there are various methods for breath detection, which can be classified into a pressure method, a temperature method, a flow method, an impedance method, and a humidity method according to the operating principle of a sensor and the difference of detected physical quantities. The humidity method is a detection means which is recently developed at present abroad and detects a respiratory signal by using a humidity sensor. The humidity method utilizes the humidity change before and after the air is exhaled and inhaled from the nostrils of the human body to carry out the breath detection, and has the characteristics of low cost, small interference, non-contact, high sensitivity, quick response, high comfort level and the like. The breath detection requires that the sensor can quickly sense the humidity signal and quickly respond and recover.
In recent years, many materials have been used to detect respiratory humidity, such as carbon materials, metal oxides, sulfides, polymers, and the like. The hydrophilic polymer has good film-forming property and abundant active sites, and has great application prospect in the aspect of humidity-sensitive detection. However, at higher relative humidity, the polymer may swell, reducing the stability of the QCM sensor. The humidity-sensitive performance of the polymer is changed and improved by modifying and changing the preparation method, and a humidity sensor taking the polymer as a sensitive material is one of important research directions for detecting humidity at home and abroad. The humidity method is used for respiratory detection, and the sensor is required to have the capability of quickly, accurately and stably capturing respiratory humidity signals.
There is a need for a humidity sensor that is low in cost, high in sensitivity, good in stability, and fast in response and recovery.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a humidity-sensitive film based on chitosan and polypyrrole and a preparation method and application thereof, so as to solve the problems in the background technology.
The technical scheme adopted by the invention for realizing the purpose is as follows: the humidity-sensitive film is a composite humidity-sensitive film based on Chitosan (CS) and polypyrrole (PPy), and the CS/PPy composite humidity-sensitive film is a porous, high-specific-surface-area, laminated and staggered incomplete coating structure.
Furthermore, the thickness of the CS/PPy composite humidity-sensitive film is 50-70 nm, and the water contact angle is 21.07 degrees.
The invention comprises a method for preparing a humidity-sensitive film based on chitosan and polypyrrole, comprising the following steps:
(1) adding chitosan powder into the acetic acid solution, stirring while adding, magnetically stirring for 10 hours, and standing for defoaming to obtain a light yellow transparent chitosan solution;
(2) adding pyrrole and ammonium sulfate into deionized water, continuously stirring for 4h, then filtering, and centrifugally washing for several times by using the deionized water to obtain a black precipitate;
(3) drying the black precipitate obtained in the step (2), and grinding into fine black polypyrrole powder;
(4) adding the polypyrrole powder obtained in the step (3) into the chitosan solution obtained in the step (1), carrying out physical blending by magnetic stirring, and carrying out ultrasonic treatment on the obtained solution for 40min to form uniform CS/PPy suspension;
(5) and (4) transferring the suspension obtained in the step (4) to a spraying device, depositing a sensitive material on the surface of the base material by adopting a spraying method, and drying at 40-60 ℃ for 1-2 h to obtain the humidity sensitive film.
Further, in the step (1), the acetic acid solution is 0.05M and 100mL, the mass of the chitosan powder is 0.4-0.6 g, and the concentration of the obtained chitosan solution is 4-6 mg/mL-1，
Or, in the step (2), the centrifugal rotating speed is 6000 to 8000r/min, washing is carried out for 3 to 5 times, the single washing time is 3 to 4min, the molar ratio of pyrrole to ammonium sulfate is 1:1,
or, the drying temperature in the step (3) is 50-60 ℃, the drying time is 10-12 h,
or, the base material in the step (5) is an electrode single surface of the quartz crystal microbalance, the spraying distance is fixed to be 50-70 mm, and the spraying time is set to be 3-5 s.
The invention includes the use of moisture-sensitive films based on chitosan and polypyrrole,
the humidity sensitive film is applied to a humidity sensor;
the humidity sensor comprises a CS/PPy humidity-sensitive film, a Quartz Crystal Microbalance (QCM) element and a lead;
the humidity sensitive film is coated on one side of the electrode of the QCM element.
Further, the humidity detection range of the humidity sensor is 0-97% RH.
Further, in the above-mentioned case,
the humidity sensitive sensing mechanism is as follows: CS contains a plurality of hydrophilic functional groups, can provide active sites for water molecule adsorption for the composite membrane, increases the specific surface area of the composite membrane, and clusters of the PPy nanospheres are distributed to bring more gaps for the composite membrane, so that a supporting effect is achieved, in a low-humidity environment, water molecules are combined with hydroxyl and amino groups of the composite membrane through hydrogen bonds to form a chemical adsorption layer, and the main reason of frequency shift change is the increase of water molecule adsorption quality; in a high-humidity environment, water molecules are increased, a physical adsorption layer is formed among the water molecules through hydrogen bonds, more water molecules enter the composite membrane to cause expansion of the composite membrane, the frequency shift can be influenced by the quality effect and the viscosity effect after the membrane is expanded, the response of the sensor is obviously increased, the stability is reduced, the mechanical property of the CS membrane can be improved through the PPy microspheres, and the quality factor of the sensor is improved.
The invention comprises the use of a moisture-sensitive film based on chitosan and polypyrrole in a breath detection system whose sensor is a humidity sensor according to any one of claims 5 to 7;
the system also comprises a breathing detection mask, a QCM oscillator, a QCM frequency tester and a breathing detection APP.
Furthermore, humidity transducer locates on breathing the detection face guard to link to each other with QCM oscillator, QCM tester through the wire.
The breathing detection APP can extract characteristic parameters of breathing signals, judge 5 breathing types of tidal breathing, Biaorespiration, normal breathing, tachypnea and bradypnea, calculate breathing frequency and generate a corresponding breathing type detection report.
Further, the system carries out signal acquisition through QCM frequency tester through humidity transducer response breathing humidity signal on the respirator, detects the characteristic parameter that APP drawed respiratory signal through breathing, judges respiratory type, calculates respiratory frequency and generates corresponding respiratory type and detects the report.
Further, the method for extracting the breathing signal characteristics and judging the type of the breathing detection App comprises the following steps: according to the characteristics of the respiratory humidity signal collected by the sensor, 3 characteristic parameters are selected:
1) number of effective peaks (N)
2) Standard deviation (sigma) of effective peak value
Wherein xiIs the peak value of the effective peak of the respiratory signal,
the average of the effective peaks is N, the number of the effective peaks represents the inspiration frequency and reflects the breathing frequency, and sigma is the standard deviation of the effective peaks.
3) Instantaneous frequency variation Range (R)
The instantaneous frequency is estimated using a phase-difference method based on the hubert transform. Assuming that the respiration signal is x (n),
the Hilbert transform is x (n), n is the number of sampling points, and the Hilbert transform is performed on x (n):
the analysis signal z (n) is constructed as follows,
a (n) is the amplitude of the analysis signal,
to analyze the phase of the signal.
The instantaneous frequency ω (n) of the signal is further calculated using the forward difference of the phase sequence as,
normalized to the instantaneous frequency omega of 0-0.5 Hznor(n) is a group of,
the variation range R of the instantaneous frequency is the difference value between the maximum value and the minimum value of the instantaneous frequency.
The method mainly comprises the following steps:
firstly, smoothing the collected respiratory humidity signal by using a mobile median Method (MAD) to ensure the effectiveness of peak searching; calculating the standard deviation of the effective peak value of the signal, wherein the standard deviation is larger due to unstable tidal breathing and unstable Biao breathing rhythm, so that the breathing is divided into two categories of unstable rhythm type (tidal breathing and Biao breathing) and stable frequency type (including normal breathing, over-breathing and over-breathing slow breathing); calculating the number of effective peak values, wherein the number of the effective peak values is the respiratory frequency, so that normal respiration, over-fast respiration and over-slow respiration are distinguished; a phase difference method based on Hilbert transform is used for estimating the change range of the instantaneous frequency of the signal, and the change range of the instantaneous frequency of tidal breathing is larger, so that tidal breathing and Biao breathing are distinguished.
The moisture-sensitive film based on chitosan and polypyrrole and the preparation method and the application thereof have the beneficial effects that:
the invention utilizes the film forming property and the hydrophilicity of chitosan and the stability of polypyrrole to prepare the material with hydrophilicity by a simple and easy-to-operate blending modification method. And obtaining the humidity-sensitive film by a spraying method, and preparing the CS/PPy-QCM humidity sensor. The obtained sensor has the advantages of high sensitivity (52.91 Hz/% RH), low wet hysteresis (1.68% RH), short response/recovery time (4s/2s), good selectivity, good repeatability and stability and the like.
The invention constructs a human body respiration detection system, which induces a respiration humidity signal through a respiration mask constructed by a humidity sensor, performs signal acquisition through a QCM tester, extracts characteristic parameters of the respiration signal as required through an App with a human-computer interaction interface, judges the respiration type, calculates the respiration frequency and generates a corresponding respiration type detection report, and displays the potential clinical respiration monitoring value.
Drawings
FIG. 1 is a schematic diagram of a breath detection system test based on a CS/PPy QCM humidity sensor according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a QCM humidity sensor cell configuration according to an embodiment of the present invention;
FIG. 3a is a high magnification scanning electron microscope image of a CS/PPy film prepared in accordance with an example of the present invention;
b is a low-magnification scanning electron microscope image of the CS/PPy film prepared by the embodiment of the invention;
FIG. 4a is a water contact test chart of the CS/PPy film of the embodiment of the present invention
b is a Fourier infrared spectrogram of the CS/PPy film in the embodiment of the invention;
FIG. 5 is a dynamic response curve of a CS/PPy composite film QCM humidity sensor according to an embodiment of the present invention;
FIG. 6 is a response/recovery curve of a CS/PPy composite film QCM humidity sensor at 97% RH in accordance with an embodiment of the present invention;
FIG. 7 is a hysteresis curve of a CS/PPy composite film QCM humidity sensor according to an embodiment of the present invention;
FIG. 8a is a repeating graph of a CS/PPy composite film QCM humidity sensor of an embodiment of the present invention at 0%, 23%, 52% and 85% RH;
b is a long-term stability plot of a sensor according to an embodiment of the present invention;
c is an alternative diagram of a sensor according to an embodiment of the present invention;
d is a graph of the frequency shift and mass change of the sensor under different humidity according to the embodiment of the invention;
FIG. 9 is a conductance spectrum of a CS/PPy composite film QCM humidity sensor of an embodiment of the present invention at different humidities;
FIG. 10 is a graph showing the quality factor of a CS/PPy composite film QCM humidity sensor at different humidities in accordance with an embodiment of the present invention;
FIG. 11 is a flowchart of the respiratory signal feature extraction and type determination of the respiratory detection system according to the present invention;
fig. 12 is a graph showing the results of determining the tachypnea and cheyne-stokes respiration by the breath test App according to the embodiment of the present invention.
Detailed Description
The invention is further explained in detail with reference to the drawings and the specific embodiments;
example 1:
as shown in fig. 1 to 12, a moisture-sensitive film based on chitosan and polypyrrole, which is a composite moisture-sensitive film based on Chitosan (CS) and polypyrrole (PPy), wherein the CS/PPy composite moisture-sensitive film has a porous, high specific surface area, and stacked and staggered incomplete coating structure.
The CS/PPy composite humidity-sensitive film is 50-70 nm in thickness and 21.07 degrees in water contact angle.
The invention comprises a method for preparing a humidity-sensitive film based on chitosan and polypyrrole, comprising the following steps:
(1) adding chitosan powder into the acetic acid solution, stirring while adding, magnetically stirring for 10 hours, and standing for defoaming to obtain a light yellow transparent chitosan solution;
(2) adding pyrrole and ammonium sulfate into deionized water, continuously stirring for 4h, then filtering, and centrifugally washing for several times by using the deionized water to obtain a black precipitate;
(3) drying the black precipitate obtained in the step (2), and grinding into fine black polypyrrole powder;
(4) adding the polypyrrole powder obtained in the step (3) into the chitosan solution obtained in the step (1), carrying out physical blending by magnetic stirring, and carrying out ultrasonic treatment on the obtained solution for 40min to form uniform CS/PPy suspension;
(5) and (4) transferring the suspension obtained in the step (4) to a spraying device, depositing a sensitive material on the surface of the base material by adopting a spraying method, and drying at 40-60 ℃ for 1-2 h to obtain the humidity sensitive film.
In the step (1), the acetic acid solution is 0.05M and 100mL, the mass of the chitosan powder is 0.4-0.6 g, and the obtained chitosan solutionHas a concentration of 4 to 6 mg/mL-1，
Or, in the step (2), the centrifugal rotating speed is 6000 to 8000r/min, washing is carried out for 3 to 5 times, the single washing time is 3 to 4min, the molar ratio of pyrrole to ammonium sulfate is 1:1,
or, the drying temperature in the step (3) is 50-60 ℃, the drying time is 10-12 h,
or, the base material in the step (5) is an electrode single surface of the quartz crystal microbalance, the spraying distance is fixed to be 50-70 mm, and the spraying time is set to be 3-5 s.
The invention includes the use of moisture-sensitive films based on chitosan and polypyrrole,
the humidity sensitive film is applied to a humidity sensor;
the humidity sensor comprises a CS/PPy humidity-sensitive film, a Quartz Crystal Microbalance (QCM) element and a lead;
the humidity sensitive film is coated on one side of the electrode of the QCM element.
The humidity detection range of the humidity sensor is 0-97% RH.
The humidity sensitive sensing mechanism is as follows: CS contains a plurality of hydrophilic functional groups, can provide active sites for water molecule adsorption for the composite membrane, increases the specific surface area of the composite membrane, and clusters of the PPy nanospheres are distributed to bring more gaps for the composite membrane, so that a supporting effect is achieved, in a low-humidity environment, water molecules are combined with hydroxyl and amino groups of the composite membrane through hydrogen bonds to form a chemical adsorption layer, and the main reason of frequency shift change is the increase of water molecule adsorption quality; in a high-humidity environment, water molecules are increased, a physical adsorption layer is formed among the water molecules through hydrogen bonds, more water molecules enter the composite membrane to cause expansion of the composite membrane, the frequency shift can be influenced by the quality effect and the viscosity effect after the membrane is expanded, the response of the sensor is obviously increased, the stability is reduced, the mechanical property of the CS membrane can be improved through the PPy microspheres, and the quality factor of the sensor is improved.
The invention comprises the use of a moisture-sensitive film based on chitosan and polypyrrole in a breath detection system whose sensor is a humidity sensor according to any one of claims 5 to 7;
the system also comprises a breathing detection mask, a QCM oscillator, a QCM frequency tester and a breathing detection APP.
The humidity sensor is arranged on the breathing detection mask and is connected with the QCM oscillator and the QCM tester through wires.
The breathing detection APP can extract characteristic parameters of breathing signals, judge 5 breathing types of tidal breathing, Biaorespiration, normal breathing, tachypnea and bradypnea, calculate breathing frequency and generate a corresponding breathing type detection report.
The system carries out signal acquisition through QCM frequency tester through humidity transducer response breathing humidity signal on the respirator, detects the characteristic parameter that APP drawed respiratory signal through breathing, judges respiratory type, calculates respiratory frequency and generates corresponding respiratory type and detects the report.
The method for extracting the breathing signal characteristics and judging the type of the breathing detection App comprises the following steps: according to the characteristics of the respiratory humidity signal collected by the sensor, 3 characteristic parameters are selected:
1) number of effective peaks (N)
2) Standard deviation (sigma) of effective peak value
Wherein xiIs the peak value of the effective peak of the respiratory signal,
the average of the effective peaks is N, the number of the effective peaks represents the inspiration frequency and reflects the breathing frequency, and sigma is the standard deviation of the effective peaks.
3) Instantaneous frequency variation Range (R)
The instantaneous frequency is estimated using a phase-difference method based on the hubert transform. Assuming that the respiration signal is x (n),
hilbert of x (n)And (3) performing a Hilbert transform on x (n), wherein n is the number of sampling points:
the analysis signal z (n) is constructed as follows,
a (n) is the amplitude of the analysis signal,
to analyze the phase of the signal.
The instantaneous frequency ω (n) of the signal is further calculated using the forward difference of the phase sequence as,
normalized to the instantaneous frequency omega of 0-0.5 Hznor(n) is a group of,
the variation range R of the instantaneous frequency is the difference value between the maximum value and the minimum value of the instantaneous frequency.
The method mainly comprises the following steps:
firstly, smoothing the collected respiratory humidity signal by using a mobile median Method (MAD) to ensure the effectiveness of peak searching; calculating the standard deviation of the effective peak value of the signal, wherein the standard deviation is larger due to unstable tidal breathing and unstable Biao breathing rhythm, so that the breathing is divided into two categories of unstable rhythm type (tidal breathing and Biao breathing) and stable frequency type (including normal breathing, over-breathing and over-breathing slow breathing); calculating the number of effective peak values, wherein the number of the effective peak values is the respiratory frequency, so that normal respiration, over-fast respiration and over-slow respiration are distinguished; a phase difference method based on Hilbert transform is used for estimating the change range of the instantaneous frequency of the signal, and the change range of the instantaneous frequency of tidal breathing is larger, so that tidal breathing and Biao breathing are distinguished.
Example 2:
as shown in fig. 1, a breath detection system based on QCM humidity sensor, the system comprises a QCM humidity sensor based on Chitosan (CS) and polypyrrole (PPy) composite film, a breath detection mask, a QCM oscillator, a QCM frequency tester, and a breath detection APP. The system senses a breathing humidity signal through a breathing mask constructed by a humidity sensor, performs signal acquisition through a QCM tester, extracts characteristic parameters of the breathing signal as required through App with human-computer interaction, judges breathing type, calculates breathing frequency and generates a corresponding breathing type detection report.
The QCM humidity sensor of the CS/PPy composite film comprises a humidity sensitive film, a QCM element and a lead; the humidity sensitive film is coated on one side of the electrode of the QCM element.
The breathing detection mask comprises a mask and the QCM humidity sensor.
And the humidity sensor wire is connected with the QCM oscillator and the QCM tester.
The respiration detection APP has a friendly man-machine interaction interface, can extract characteristic parameters of respiration signals, judges 5 respiration types (tidal respiration, Biaoch respiration, normal respiration, tachypnea and bradypnea), calculates respiration frequency and generates a corresponding respiration type detection report.
The humidity detection range of the CS/PPy QCM sensor is 0-97% RH, the sensitivity is 52.91 Hz/% RH, the wet retardation is 1.68% RH, the response/recovery time is 4s/2s, and the CS/PPy QCM sensor has excellent selectivity, repeatability and stability. The invention has the advantages of providing guarantee for accurate and rapid detection of human respiration. The CS/PPy-QCM humidity sensor prepared by the invention can still stably work in a high-humidity environment due to the supporting effect of PPy, and keeps a higher quality factor.
The QCM device coated with the humidity sensitive thin film has a structure as shown in fig. 2, wherein silver electrodes 2 are sputtered on both sides of a quartz crystal 1, a CS/PPy humidity sensitive thin film coating 3 is sprayed on one side of the silver electrodes 2, and 4 is a base of the quartz crystal. The thickness of the coating 3 is 50-70 nm.
A scanning electron microscope image of the CS/PPy humidity-sensitive film is shown in FIG. 3, and the film has a porous, high specific surface area, and a laminated and staggered incomplete coating structure.
Fig. 4(a) is a result of a water contact angle test of the film, the water contact angle being 21.07 °, demonstrating that the film has good hydrophilicity. Fourier infrared spectrum of the film As shown in FIG. 4(b), the composite film had an absorption peak of the hydrophilic group.
The dynamic response curve of the QCM humidity sensor of CS/PPy composite film is shown in FIG. 5. As can be seen, the frequency shift of the humidity sensitive element increases with increasing humidity, with a maximum frequency shift of up to five kilohertz. In 9 consecutive reaction cycles, the device has good response reversibility to different humidities.
The response/recovery curves of the device at 97% RH are shown in fig. 6, with short response/recovery times of 4s and 2s, respectively.
FIG. 7 shows the hysteresis curve of the device, with a maximum hysteresis of 1.68% RH occurring at 67% RH.
In FIG. 8, a is the repeatability of the CS/PPy humidity sensor at 0%, 23%, 52% and 85% RH, b is the long term stability of the sensor, c is the selectivity of the sensor and d is the frequency shift and mass change at different humidities.
The conductance spectrum of the CS/PPy composite film QCM humidity sensor is shown in FIG. 9. As the relative humidity increases, the water adsorption capacity increases, the center frequency decreases, the curve moves to the left, the conductance peak value decreases, the half-bandwidth widens, and the quality factor decreases. At high relative humidity, the viscosity of the film increases and the energy loss increases.
The figure of merit of the device at different humidities is shown in fig. 10. PPy is introduced to support the CS membrane, so that the mechanical property of the composite membrane is improved, the quality factor is improved, and the energy dissipation is reduced.
A preparation method of a CS/PPy composite humidity-sensitive film comprises the following steps:
add 0.5g CS powder to acetic acid solution (0.05M, 100mL) with stirring and stir magnetically for 10 h. After standing and defoaming, a pale yellow transparent CS solution (5 mg. mL) was obtained-1)；
Adding pyrrole (0.1M) and APS (0.1M) into 100mL of deionized water, continuously stirring for 4h, then filtering, washing for 3 times by using the deionized water, wherein the rotating speed is 8000r/min, and the single washing time is 3 min;
thirdly, drying the black precipitate obtained in the second step at 60 ℃ for 12 hours, and then grinding the black precipitate into fine black PPy powder;
and fourthly, adding the PPy powder obtained in the third step into the CS solution, and stirring by magnetic force to carry out physical blending. Carrying out ultrasonic treatment on the obtained solution for 40min to form a uniform CS/PPy suspension;
transferring the suspension obtained in the step (iv) to a spray coating device, covering a non-electrode part of a quartz crystal microbalance (abbreviated as QCM) by using a self-made baffle, depositing a sensitive material on one side of a QCM electrode by using a spray coating method, wherein the spray coating distance is fixed to be 70mm, and the spray coating time is set to be 5 s;
and (c) drying the QCM obtained in the fifth step for 1-2 hours at the temperature of 40-60 ℃ to obtain the humidity sensitive film.
The mechanism of the humidity-sensitive sensor of the CS/PPy humidity-sensitive film is as follows: CS contains a plurality of hydrophilic functional groups, can provide active sites for water molecule adsorption for the composite membrane, increases the specific surface area of the composite membrane, and the cluster distribution of the PPy nanospheres brings more gaps for the composite membrane, thereby playing a supporting role. In a low humidity environment, water molecules are combined with hydroxyl and amino groups of the composite membrane through hydrogen bonds to form a chemical adsorption layer, and the main reason of frequency shift change is the increase of the adsorption quality of the water molecules. In a high-humidity environment, water molecules are increased, a physical adsorption layer is formed among the water molecules through hydrogen bonds, more water molecules enter the composite membrane, and the composite membrane is expanded. Mass effects and viscosity effects after expansion of the membrane can affect the frequency shift, resulting in a significant increase in sensor response and a decrease in stability. The PPy microspheres can improve the mechanical property of the CS membrane and improve the quality factor of the sensor.
A method for extracting respiratory signal features and judging types, the flow of which is shown in fig. 11, the main steps are as follows:
the breath detection App relates to a method for extracting and judging the type of a breath signal feature, and can extract and judge the type of five types of breath (normal breath, over-rapid breath, over-slow breath, tidal breath and belaoh breath). According to the characteristics of the respiratory humidity signal collected by the sensor, 3 characteristic parameters are selected:
1) number of effective peaks (N)
2) Standard deviation (sigma) of effective peak value
Wherein xiIs the peak value of the effective peak of the respiratory signal,
the average of the effective peaks is N, the number of the effective peaks represents the inspiration frequency and reflects the breathing frequency, and sigma is the standard deviation of the effective peaks.
3) Instantaneous frequency variation Range (R)
The instantaneous frequency is estimated using a phase-difference method based on the hubert transform. Assuming that the respiration signal is x (n),
the Hilbert transform is x (n), n is the number of sampling points, and the Hilbert transform is performed on x (n):
the analysis signal z (n) is constructed as follows,
a (n) is the amplitude of the analysis signal,
to analyze the phase of the signal.
The instantaneous frequency ω (n) of the signal is further calculated using the forward difference of the phase sequence as,
normalized to the instantaneous frequency omega of 0-0.5 Hznor(n) is a group of,
the variation range R of the instantaneous frequency is the difference value between the maximum value and the minimum value of the instantaneous frequency.
The method mainly comprises the following steps:
firstly, smoothing the collected respiratory humidity signal by using a mobile median Method (MAD) to ensure the effectiveness of peak searching; calculating the standard deviation of the effective peak value of the signal, wherein the standard deviation is larger due to unstable tidal breathing and unstable Biao breathing rhythm, so that the breathing is divided into two categories of unstable rhythm type (tidal breathing and Biao breathing) and stable frequency type (including normal breathing, over-breathing and over-breathing slow breathing); calculating the number of effective peak values, wherein the number of the effective peak values is the respiratory frequency, so that normal respiration, over-fast respiration and over-slow respiration are distinguished; a phase difference method based on Hilbert transform is used for estimating the change range of the instantaneous frequency of the signal, and the change range of the instantaneous frequency of tidal breathing is larger, so that tidal breathing and Biao breathing are distinguished.
The respiration detection system based on the QCM humidity sensor is applied to a respiratory mask sensing respiration humidity signal constructed by the system through the humidity sensor, signal acquisition is carried out through a QCM tester, and through an App with a human-computer interaction interface, a method for extracting and judging the type of the respiration signal according to requirements is used for extracting characteristic parameters of the respiration signal, judging the respiration type, calculating the respiration frequency and generating a corresponding respiration type detection report. Fig. 12 shows the determination of the breath tachypnea and cheyne-stokes respiration by the breath test App.
Example 3:
a preparation method of a CS/PPy composite humidity-sensitive film comprises the following steps:
add 0.4g CS powder to acetic acid solution (0.05M, 100mL) with stirring and stir magnetically for 10 h. After standing and defoaming, a pale yellow transparent CS solution (4 mg. mL) was obtained-1)；
Adding pyrrole (0.1M) and APS (0.1M) into 100mL of deionized water, continuously stirring for 4 hours, then filtering, washing for 4 times by using the deionized water, wherein the rotating speed is 7000r/min, and the single washing time is 3 min;
thirdly, drying the black precipitate obtained in the second step at 50 ℃ for 12 hours, and then grinding the black precipitate into fine black PPy powder;
and fourthly, adding the PPy powder obtained in the third step into the CS solution, and stirring by magnetic force to carry out physical blending. Carrying out ultrasonic treatment on the obtained solution for 40min to form a uniform CS/PPy suspension;
transferring the suspension obtained in the step (iv) to a spray coating device, covering a non-electrode part of a quartz crystal microbalance (abbreviated as QCM) by using a self-made baffle, depositing a sensitive material on one side of a QCM electrode by using a spray coating method, wherein the spray coating distance is fixed to be 50mm, and the spray coating time is set to be 3 s;
and (c) drying the QCM obtained in the fifth step for 1-2 hours at the temperature of 40-60 ℃ to obtain the humidity sensitive film.
Through detection, the QCM humidity sensor for the CS/PPy film prepared by the embodiment has good response and recovery performance under 0-97% RH.
Example 4:
a preparation method of a CS/PPy composite humidity-sensitive film comprises the following steps:
add 0.6g CS powder to acetic acid solution (0.05M, 100mL) with stirring and stir magnetically for 10 h. After standing and defoaming, a pale yellow transparent CS solution (6 mg. mL) was obtained-1)；
Adding pyrrole (0.1M) and APS (0.1M) into 100mL of deionized water, continuously stirring for 4h, filtering, washing with deionized water for 5 times, wherein the rotating speed is 6000r/min, and the single washing time is 4 min;
thirdly, drying the black precipitate obtained in the second step at 60 ℃ for 10 hours, and then grinding the black precipitate into fine black PPy powder;
and fourthly, adding the PPy powder obtained in the third step into the CS solution, and stirring by magnetic force to carry out physical blending. Carrying out ultrasonic treatment on the obtained solution for 40min to form a uniform CS/PPy suspension;
transferring the suspension obtained in the step (iv) to a spray coating device, covering a non-electrode part of a quartz crystal microbalance (abbreviated as QCM) by using a self-made baffle, depositing a sensitive material on one side of a QCM electrode by using a spray coating method, wherein the spray coating distance is fixed to be 50mm, and the spray coating time is set to be 3 s;
and (c) drying the QCM obtained in the fifth step for 1-2 hours at the temperature of 40-60 ℃ to obtain the humidity sensitive film.
Through detection, the QCM humidity sensor for the CS/PPy film prepared by the embodiment has good response and recovery performance under 0-97% RH.
The invention utilizes the film forming property and hydrophilicity of chitosan and the stability of polypyrrole to prepare the hydrophilic humidity sensitive material by a simple and easy-to-operate blending modification method. The CS/PPy humidity-sensitive film with the thickness of 50-70 nm, the high specific surface area and the overlapped and staggered incomplete coating structure is obtained by a spraying method, and the CS/PPy-QCM humidity sensor is prepared. The obtained sensor has the advantages of high sensitivity (52.91 Hz/% RH), low wet hysteresis (1.68% RH), short response/recovery time (4s/2s), good selectivity, good repeatability and stability and the like. The invention designs a breath detection App and constructs a human breath detection system. The system senses a breathing humidity signal through a breathing mask constructed by a humidity sensor, performs signal acquisition through a QCM tester, extracts characteristic parameters of the breathing signal as required through an App with a human-computer interaction interface, judges breathing type, calculates breathing frequency and generates a corresponding breathing type detection report.
The pyrrole (more than or equal to 98 percent), the Ammonium Persulfate (APS) (more than or equal to 98 percent), the chitosan (80 to 95 percent of deacetylation degree) and the acetic acid (more than or equal to 99.5 percent) used in the invention are provided by Shanghai Chinese medicine group chemical reagent company Limited in China.
The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention accordingly, and not to limit the protection scope of the present invention accordingly. All equivalent changes or modifications made in accordance with the spirit of the present disclosure are intended to be covered by the scope of the present disclosure.
Claims (10)
1. A moisture-sensitive film based on chitosan and polypyrrole, which is characterized in that: the humidity-sensitive film is a composite humidity-sensitive film based on Chitosan (CS) and polypyrrole (PPy), and the CS/PPy composite humidity-sensitive film is of a porous, high-specific-surface-area, laminated and staggered incomplete coating structure.
2. The chitosan and polypyrrole-based moisture-sensitive film according to claim 1, wherein: the CS/PPy composite humidity-sensitive film is 50-70 nm in thickness and 21.07 degrees in water contact angle.
3. A method for preparing the moisture-sensitive film based on chitosan and polypyrrole according to any one of claims 1 to 2, characterized by comprising the steps of:
(1) adding chitosan powder into the acetic acid solution, stirring while adding, magnetically stirring for 10 hours, and standing for defoaming to obtain a light yellow transparent chitosan solution;
(2) adding pyrrole and ammonium sulfate into deionized water, continuously stirring for 4h, then filtering, and centrifugally washing for several times by using the deionized water to obtain a black precipitate;
(3) drying the black precipitate obtained in the step (2), and grinding into fine black polypyrrole powder;
(4) adding the polypyrrole powder obtained in the step (3) into the chitosan solution obtained in the step (1), carrying out physical blending by magnetic stirring, and carrying out ultrasonic treatment on the obtained solution for 40min to form uniform CS/PPy suspension;
(5) and (4) transferring the suspension obtained in the step (4) to a spraying device, depositing a sensitive material on the surface of the base material by adopting a spraying method, and drying at 40-60 ℃ for 1-2 h to obtain the humidity sensitive film.
4. The method for preparing a moisture-sensitive film based on chitosan and polypyrrole according to claim 3, wherein: in the step (1), the acetic acid solution is 0.05M and 100mL, the mass of the chitosan powder is 0.4-0.6 g, and the concentration of the obtained chitosan solution is 4-6 mg/mL-1，
Or, in the step (2), the centrifugal rotating speed is 6000 to 8000r/min, washing is carried out for 3 to 5 times, the single washing time is 3 to 4min, the molar ratio of pyrrole to ammonium sulfate is 1:1,
or, the drying temperature in the step (3) is 50-60 ℃, the drying time is 10-12 h,
or, the base material in the step (5) is an electrode single surface of the quartz crystal microbalance, the spraying distance is fixed to be 50-70 mm, and the spraying time is set to be 3-5 s.
5. Use of a moisture-sensitive film based on chitosan and polypyrrole, having a structure according to any of claims 1 to 2 or prepared according to the process of any of claims 3 to 4, characterized in that:
the humidity sensitive film is applied to a humidity sensor;
the humidity sensor comprises a CS/PPy humidity-sensitive film, a Quartz Crystal Microbalance (QCM) element and a lead;
the humidity sensitive film is coated on one side of the electrode of the QCM element.
6. Use of a moisture-sensitive film based on chitosan and polypyrrole according to claim 5, characterized in that:
the humidity detection range of the humidity sensor is 0-97% RH.
7. Use of a moisture-sensitive film based on chitosan and polypyrrole according to claim 5, characterized in that:
the humidity sensitive sensing mechanism is as follows: CS contains a plurality of hydrophilic functional groups, can provide active sites for water molecule adsorption for the composite membrane, increases the specific surface area of the composite membrane, and clusters of the PPy nanospheres are distributed to bring more gaps for the composite membrane, so that a supporting effect is achieved, in a low-humidity environment, water molecules are combined with hydroxyl and amino groups of the composite membrane through hydrogen bonds to form a chemical adsorption layer, and the main reason of frequency shift change is the increase of water molecule adsorption quality; in a high-humidity environment, water molecules are increased, a physical adsorption layer is formed among the water molecules through hydrogen bonds, more water molecules enter the composite membrane to cause expansion of the composite membrane, the frequency shift can be influenced by the quality effect and the viscosity effect after the membrane is expanded, the response of the sensor is obviously increased, the stability is reduced, the mechanical property of the CS membrane can be improved through the PPy microspheres, and the quality factor of the sensor is improved.
8. Use of a moisture-sensitive film based on chitosan and polypyrrole, said moisture-sensitive material having a structure according to any one of claims 1 to 2, or being prepared according to the method of any one of claims 3 to 4, characterized in that: the humidity sensitive film is applied to a respiration detection system, and a sensor of the respiration detection system is a humidity sensor as claimed in any one of claims 5 to 7;
the system also comprises a breathing detection mask, a QCM oscillator, a QCM frequency tester and a breathing detection APP.
9. Use of a moisture-sensitive film based on chitosan and polypyrrole according to claim 8, characterized in that: the humidity sensor is arranged on the breathing detection mask and is connected with the QCM oscillator and the QCM tester through wires.
The breathing detection APP can extract characteristic parameters of breathing signals, judge 5 breathing types of tidal breathing, Biaorespiration, normal breathing, tachypnea and bradypnea, calculate breathing frequency and generate a corresponding breathing type detection report.
10. Use of a moisture-sensitive film based on chitosan and polypyrrole according to claim 8, characterized in that: the system carries out signal acquisition through QCM frequency tester through humidity transducer response breathing humidity signal on the respirator, detects the characteristic parameter that APP drawed respiratory signal through breathing, judges respiratory type, calculates respiratory frequency and generates corresponding respiratory type and detects the report.
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