CN114323407A - Flexible film type self-driven multifunctional sensor and preparation method thereof - Google Patents
Flexible film type self-driven multifunctional sensor and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a flexible film type self-driven multifunctional sensor which comprises a flexible substrate, a gas conduit, a multifunctional sensitive film, interdigital electrodes and an elastic film. The self-driven multifunctional sensor combines the energy collection unit and the gas sensitive unit together, and the piezoelectric multifunctional sensitive film is deformed by utilizing the increase of air pressure when gas is introduced, so that energy is provided for the self-driven multifunctional sensor to spontaneously and actively measure the concentration and the pressure of the gas to be measured. The sensor adopts a centrosymmetric device structure to maximize the transduction efficiency of the electrostatic spinning with disordered distribution, and simultaneously actively loads the gas adsorption process into the output electric signal of the piezoelectric nano generator by utilizing the coupling effect of gas chemical adsorption and piezoelectric effect, so that the concentration and the air pressure of the gas to be measured can be measured simultaneously without an additional power supply system. The sensor provided by the invention has the advantages of simple preparation, low cost, novel structure and high practicability, and fully utilizes the kinetic energy of gas flow.
Description
Technical Field
The invention belongs to the field of energy collection technology and electronic polymer sensitive materials, and particularly relates to a flexible film type self-driven multifunctional sensor and a preparation method thereof.
Background
Ammonia gas is widely used as an industrial raw material in the fields of chemical industry, light industry, chemical fertilizers, pharmacy and the like. Meanwhile, ammonia gas is a highly toxic gas, and high-concentration ammonia gas has strong stimulation and even corrosion effects on human respiratory tracts. When exposed to a high-concentration ammonia gas atmosphere, people can generate symptoms such as eye lacrimation, dyspnea, dizziness, weakness and the like, and seriously can cause overhigh ammonia concentration in blood of a human body so as to endanger life. The concentration of the ammonia gas is detected in real time, so that the harm to human health caused by the fact that people are in a high-concentration ammonia gas environment can be avoided. Therefore, the research on the ammonia gas sensor is urgently carried out.
At present, most ammonia sensors are powered by batteries, and maintenance personnel are required to replace the batteries regularly to ensure that the equipment can operate continuously, so that the operating cost is increased and the life safety of the maintenance personnel is seriously threatened for sensor nodes in places where ammonia gas is easy to leak and in some extreme environments. Therefore, the maintenance of the continuous operation of the ammonia gas sensor by the regular replacement of the battery by maintenance personnel is difficult for equipment in high-risk places, and the self-powered technology is used for converting energy in the environment into electric energy, so that the wireless sensor node is an ideal scheme for solving the problem of power supply of the wireless sensor node.
In addition, ammonia gas as a marker can be used for detecting relevant reference indexes of human health diseases. For example, the generation of ammonia gas in exhaled breath is related to the metabolism of human nitrogen and has a certain linear relationship with blood urea nitrogen in blood, so that whether renal function is abnormal can be diagnosed by detecting the concentration of ammonia gas in exhaled breath of human body. Through combining together self-power ammonia sensor and wearable equipment, not only can realize the sustainable of the energy, can also feed back human healthy situation anytime and anywhere.
In order to solve the problems that the traditional ammonia gas sensor is short in service life, needs external energy to supply power and the like, a self-energy supply technology is necessary to be introduced into the research of the ammonia gas sensor. The piezoelectric material can convert mechanical energy into kinetic energy, has the advantages of miniaturization, high efficiency, simplicity and the like, and provides a new development direction for the research of the self-powered ammonia sensor.
Disclosure of Invention
The invention aims to solve the technical problems in the prior art, and provides a flexible film type self-driven multifunctional sensor and a preparation method thereof, so that the integration of energy collection and gas detection is realized. The self-driven multifunctional sensor has the advantages of simple process, low cost, small volume, light weight and batch production.
In order to solve the above technical problem, an embodiment of the present invention provides a flexible film type self-driven multifunctional sensor, which includes a flexible substrate 1, a gas conduit 2, a gas sensitive film 3, an interdigital electrode 4, and an elastic film 5;
the flexible substrate 1 is provided with a vent hole for inserting the gas conduit 2, the interdigital electrode 4 is a center-symmetrical interdigital electrode with a spiral structure, the interdigital electrode 4 is positioned on the elastic membrane 5, the gas-sensitive film 3 is positioned on one surface of the elastic membrane 5 with the interdigital electrode 4, the gas-sensitive film 3 is formed by interweaving a plurality of nano fibers with a core-shell structure, and the nano fibers with the core-shell structure are a piezoelectric layer 6, a PDA (polydopamine) layer 7 and a gas-sensitive layer 8 in sequence from inside to outside;
the edge of one surface, provided with the interdigital electrode 4, of the elastic membrane 5 is sealed and fixed with the edge of the flexible substrate 1, so that a cavity is formed between the flexible substrate 1 and the elastic membrane 5, when gas to be detected is introduced into the cavity through the gas conduit 2, the elastic membrane 5 expands and contracts under the action of airflow, and meanwhile, the gas-sensitive thin film 3 attached to the elastic membrane 5 is stretched and restored, so that polarization charges are generated at two ends of the piezoelectric layer 6, and further, the conversion from gas kinetic energy to device electric energy is realized, and the gas pressure and the gas concentration are detected spontaneously and actively.
Furthermore, the PDA layer 7 has excellent hydrophilicity and adhesiveness, and is beneficial to preparing the gas sensitive layer 8 on the PDA layer 7 so as to form a core-shell structure and enhance the stability of the core-shell structure nanofiber;
the gas sensitive layer 8 is made of a gas sensitive material with good conductivity (>5S/cm), can play a role in electrostatic shielding of polarization charges at two ends of the internal piezoelectric layer 6, and changes the electrostatic shielding effect on the piezoelectric core by utilizing the change of the conductivity of the gas sensitive layer 8 along with the concentration of the specific sensitive gas.
Further, the interdigital electrode 4 is in a centrosymmetric spiral structure to collect anisotropic air pressure sensitive film expansion mechanical energy, and the air pressure sensitive mechanism of the core-shell structured nanofiber is as follows: when the gas to be detected introduced into the gas conduit 2 is nonspecific sensitive gas or specific sensitive gas with constant concentration, the pressure in the cavity is increased, the elastic membrane 5 expands and stretches the gas-sensitive film 3, the piezoelectric layer 6 in the gas-sensitive film 3 generates polarization charges, and a small amount of induction charges are generated on the interdigital electrode 4 due to incomplete electrostatic shielding of the gas sensitive layer 8, so that an output electric signal is generated; along with the increase of the air pressure, the larger the stretching deformation degree of the air-sensitive film is, the more the generated polarization charges are, the larger the output electric signal is, and the measurement of the air pressure of the introduced air can be realized by detecting the output electric signals at the two ends of the interdigital electrode.
Further, the gas-sensitive mechanism of the nanofiber with the core-shell structure is as follows: when the gas to be detected introduced into the gas conduit 2 is a specific sensitive gas, the elastic membrane 5 expands under the action of the pressure difference, and accordingly the gas-sensitive film 3 is stretched, so that the piezoelectric layer 6 inside the gas-sensitive film generates polarization charges, only a small amount of induced charges are generated on the interdigital electrode due to the electrostatic shielding action of the conductive gas sensitive layer 8, and the gas to be detected reacts with the gas sensitive layer to change the conductivity of the gas sensitive layer and further change the electrostatic shielding effect of the gas sensitive layer, so that the amount of the induced charges generated on the interdigital electrode changes, the output electric signal changes, and the more the reaction between the gas to be detected and the gas sensitive layer 8 is along with the increase of the concentration of the gas to be detected in the introduced gas, the more the conductivity of the gas sensitive layer changes, the weakening change of the electrostatic shielding effect of the polarization charges is strengthened more greatly, the number of the induced charges generated on the interdigital electrode is increased, and the change range of the output electric signals is increased, so that when the gas to be measured is introduced, the concentration of the specific sensitive gas can be measured by measuring the output electric signals at the two ends of the interdigital electrode.
Further, the preparation method of the gas-sensitive film 3 comprises the following steps: firstly, preparing a piezoelectric layer 6 and a DA (dopamine) layer by adopting an electrostatic spinning method, then forming a PDA layer 7 by self-polymerization of DA in a Tris (Tris) buffer solution, and finally preparing a gas sensitive layer 8 by in-situ self-assembly of aniline monomers under an acidic condition.
Furthermore, the porosity of the spinning film can be adjusted by adjusting the electrostatic spinning time for 3-15min, so that the output response of the gas-sensitive film is adjusted; the thickness degree of the spinning fiber can be adjusted by adjusting the spinning voltage of 15-20kV and the advancing speed of 5-15 muL/min, and the thickness, the porosity and the surface area of the adsorbent of the gas sensitive layer are adjusted by adjusting the DA self-polymerization time of 15-20h, so that the thickness ratio of the piezoelectric layer core to the gas sensitive layer shell is adjusted.
Furthermore, the gas-sensitive film 3 can be prepared by using coaxial electrostatic spinning, the inner layer of the spinning equipment is used for preparing a core piezoelectric material, the outer layer of the spinning equipment is used for preparing a gas-sensitive shell, and the thickness ratio of the piezoelectric layer core to the gas-sensitive shell can be adjusted to be 0.2-0.8 through the size of the inner and outer layer needles, so that the optimized self-driven gas-sensitive test is realized.
Furthermore, the thickness of the interdigital electrode is 100nm-200nm, the radius is 3.0-3.6cm, the width of the interdigital is 0.05-0.2mm, the gap of the interdigital is 0.04-0.16mm, and the duty ratio of the interdigital electrode is 35-55%.
In order to solve the above technical problem, an embodiment of the present invention provides a method for manufacturing a flexible film type self-driven multifunctional sensor, including the following steps:
step 1: preparing an interdigital electrode 4 on an elastic membrane 5, wherein the interdigital electrode 4 is a centrosymmetric interdigital electrode with a spiral structure, and a vent hole is cut on a flexible substrate 1;
step 2: preparing a gas-sensitive film 3 on one surface of the elastic film 5 with the interdigital electrode 4, so that the gas-sensitive film 3 can be stretched while the elastic film expands when the air pressure in the cavity is increased, wherein the gas-sensitive film 3 is formed by interweaving a plurality of core-shell structure nanofibers, and the core-shell structure nanofibers are sequentially provided with a piezoelectric layer 6, a PDA layer 7 and a gas sensitive layer 8 from inside to outside;
and step 3: will elastic membrane 5 have the edge of the one side of interdigital electrode 4 with the edge seal of flexible basement 1 is fixed, inserts gas conduit 2 in the air vent of flexible basement 1, thereby flexible basement 1 with form the cavity between the elastic membrane 5, pass through gas conduit 2 to when the cavity lets in the gas that awaits measuring, make under the effect of air current elastic membrane 5 takes place to expand and contract, along with letting in the difference of the sensitive gas concentration of specificity in the gas that awaits measuring or the difference of atmospheric pressure, the output signal of telecommunication of interdigital electrode changes, through the output telecommunication number that detects interdigital electrode both ends, realizes the detection to the gas concentration that awaits measuring and atmospheric pressure.
Further, the preparation method of the gas-sensitive film 3 comprises the following steps:
step 11: using 10-50mL of a mixture with the volume ratio of 1: 1, taking DMAC and acetone as solvents, preparing PVDF (polyvinylidene fluoride) crystal into 10-30 wt% PVDF solution by using a magnetic stirrer to magnetically stir for 1-3h under the water bath heating condition of 40-60 ℃, adding dopamine hydrochloride (DA & HCL) powder into the PVDF solution, and stirring for 1-3h under the water bath heating condition of 40-60 ℃ to obtain DA/PVDF mixed solution, wherein the mass ratio of dopamine to PVDF is 1: 3-1: 1;
step 12: preparing the DA/PVDF mixed solution into a spinning film by adopting an electrostatic spinning method;
step 13: dissolving Tris (Tris hydroxymethyl aminomethane) in 250-1250mL of Ultrapure (UP) water to prepare 1.0-1.5mg/mL of Tris buffer solution, soaking the spinning film in the Tris buffer solution for 15-25h, then washing off redundant Tris solution by using ultrapure water and drying;
step 14: dissolving aniline monomer in 100-500mL dilute hydrochloric acid to prepare aniline solution with relative volume fraction of 0.25-0.75%, dissolving ammonium persulfate in 10-50mL dilute hydrochloric acid solution with 2mol/L to prepare ammonium persulfate solution with 0.25-0.75mol/L, placing the spinning film treated in the step 13 in the aniline solution under the condition of ice bath (0 ℃), dropwise adding ammonium persulfate solution until the solution is light blue, and taking out the spinning film after the solution becomes dark blue;
step 15: and (3) drying the spinning film treated in the step (14) in a drying oven at the temperature of 50-70 ℃ for 3-5h, and finishing the preparation of the gas-sensitive film.
Further, the electrospinning conditions were as follows: the distance between the needle and the aluminum foil collecting plate is 10-20cm, the speed of the propulsion pump is 5-15 muL/min, the voltage applied by an external high-voltage source is 15-20kV, and the spinning time is 3-15 min.
The working principle of the invention is as follows:
the self-driven multifunctional sensor can convert the kinetic energy of the introduced gas flow into the electrical signal of the piezoelectric nano generator to be output, and realizes the self-powered detection of the concentration and the air pressure of the gas to be detected. Specifically, when a gas to be measured, which is a non-specific sensitive gas or a specific sensitive gas with a constant concentration, is introduced into the gas conduit 2, the gas pressure in the cavity is increased, the elastic membrane 5 expands and stretches the gas sensitive membrane 3, the piezoelectric layer 6 inside the gas sensitive membrane 3 generates polarization charges, and a small amount of induced charges are generated on the interdigital electrode 4 due to incomplete electrostatic shielding of the gas sensitive layer 8, so that an output electric signal is generated. With the increase of the air pressure, the larger the stretching deformation degree of the air-sensitive film is, the more polarization charges are generated, and the larger the output electric signal is. The measurement of the gas pressure of the introduced gas can be realized by detecting the output electric signals at the two ends of the interdigital electrode. When a certain volume of gas to be detected of specific sensitive gas is introduced into the gas conduit 2, the elastic membrane 5 expands under the action of the pressure difference, and accordingly the gas sensitive film 3 is stretched, so that the piezoelectric layer 6 in the gas sensitive film generates polarization charges, and due to the electrostatic shielding effect of the conductive gas sensitive layer 8, only a small amount of induction charges are generated on the interdigital electrode, and the gas to be detected reacts with the gas sensitive layer to change the conductivity of the gas to change the electrostatic shielding effect of the gas to change the induction charge amount generated on the interdigital electrode, so that the output electric signal changes. Along with the increase of the concentration of the gas to be detected in the introduced gas, the more violent the reaction of the gas to be detected and the gas sensitive layer 8 is, the more the conductivity of the gas sensitive layer is changed, the more the weakening change of the electrostatic shielding effect on the polarization charges is enhanced, the variable quantity of the number of the induction charges generated on the interdigital electrode is increased, and the change amplitude of the output electric signal is increased. When specific sensitive gas with a certain volume is introduced, the concentration of the gas to be measured can be measured by measuring and outputting an electric signal.
The invention has the beneficial effects that: compared with the traditional gas sensor, the self-powered integrated structure does not need an additional external power supply system, and the self-powered integrated structure can directly utilize the kinetic energy of the gas flow introduced into the piezoelectric generator to drive the piezoelectric generator to work, so that the concentration and the gas pressure of the gas to be detected can be autonomously detected; in addition, the integrated structure successfully integrates the energy collection unit, the gas sensing unit and the detection circuit unit. The multifunctional self-driven sensor provided by the invention does not need external energy supply, and has the advantages of simple structure, low cost and easiness in integration.
Drawings
Fig. 1 is a schematic structural diagram of a flexible film type self-driven multifunctional sensor according to a first embodiment of the present invention;
fig. 2 is a schematic structural diagram of a gas-sensitive film in a flexible film self-driven multifunctional sensor according to a first embodiment of the present invention;
FIG. 3 is a process flow chart of a method for manufacturing a flexible thin film self-driven multifunctional sensor according to a second embodiment of the present invention;
fig. 4 is a schematic diagram of the mechanism of the flexible film self-driven multifunctional sensor according to the second embodiment of the present invention when dry air and ammonia gas are introduced, wherein (a) is when no gas is introduced, (b) is when dry air is introduced, and (c) is when ammonia gas is introduced.
In the drawings, the components represented by the respective reference numerals are listed below:
1. the gas sensor comprises a flexible substrate, 2, a gas conduit, 3, a gas-sensitive film, 4, interdigital electrodes, 5, an elastic film, 6, a piezoelectric layer, 7, a PDA layer, 8 and a gas-sensitive layer.
Detailed Description
The principles and features of this invention are described below in conjunction with the following drawings, the examples of which are set forth to illustrate the invention and are not intended to limit the scope of the invention.
Based on the piezoelectric effect and the electrostatic shielding principle, the invention utilizes the kinetic energy of introduced gas to enable the piezoelectric layer to generate polarization charges, and shields the piezoelectric layer through the gas sensitive layer, and only a small amount of polarization charges generate output electric signals on the interdigital electrode due to incomplete electrostatic shielding. When non-specific sensitive gas or specific sensitive gas with constant concentration is introduced, the output electric signal is increased along with the increase of the gas pressure of the introduced gas, so that the detection of the gas pressure is realized. When the specific sensitive gas is introduced, the specific sensitive gas reacts with the gas sensitive layer to weaken the electrostatic shielding effect, so that a larger output electric signal is generated on the interdigital electrode, and the output electric signal is increased along with the increase of the gas concentration, so that the detection of the gas concentration is realized. Therefore, the invention realizes a self-driven multifunctional sensor which converts mechanical energy into electric energy and integrates gas detection.
As shown in fig. 1-2, a first embodiment of the present invention provides a flexible film self-driven multifunctional sensor, which comprises a flexible substrate 1, a gas conduit 2, a gas-sensitive film 3, interdigital electrodes 4 and an elastic film 5;
the flexible substrate 1 is provided with a vent hole for inserting the gas conduit 2, the interdigital electrode 4 is a center-symmetrical interdigital electrode with a spiral structure, the interdigital electrode 4 is positioned on the elastic membrane 5, the gas-sensitive film 3 is positioned on one surface of the elastic membrane 5 with the interdigital electrode 4, the gas-sensitive film 3 is formed by interweaving a plurality of nano fibers with a core-shell structure, and the nano fibers with the core-shell structure are a piezoelectric layer 6, a PDA layer 7 and a gas sensitive layer 8 in sequence from inside to outside;
the edge of one surface, provided with the interdigital electrode 4, of the elastic membrane 5 is sealed and fixed with the edge of the flexible substrate 1, so that a cavity is formed between the flexible substrate 1 and the elastic membrane 5, when gas is introduced into the cavity through the gas conduit 2, the elastic membrane 5 expands and contracts under the action of airflow, and meanwhile, the gas-sensitive membrane 3 attached to the elastic membrane 5 is stretched and restored, so that polarization charges are generated at two ends of the piezoelectric layer 6 inside the gas-sensitive membrane 3, and further, the conversion from gas kinetic energy to device electric energy is realized, and the gas pressure and the gas concentration are spontaneously and actively detected.
In the embodiment, compared with the traditional gas sensor, the self-powered integrated structure does not need an additional external power supply system, and the self-powered integrated structure can directly utilize the kinetic energy of the gas flow introduced into the piezoelectric generator to drive the piezoelectric generator to work, so that the concentration and the gas pressure of the gas to be detected can be autonomously detected; in addition, the integrated structure successfully integrates the energy collection unit, the gas sensing unit and the detection circuit unit. The multifunctional self-driven sensor provided by the invention does not need external energy supply, and has the advantages of simple structure, low cost and easiness in integration.
The piezoelectric layer 6 in this embodiment has a piezoelectric effect, and when the gas sensitive film 3 is stretched by gas expansion, polarization charges are generated at both ends of the piezoelectric layer 6.
In addition, the interdigital electrode 4 is in a centrosymmetric spiral structure, so that the mechanical expansion energy of the anisotropic gas-sensitive film 3 can be collected, and the air pressure sensitivity mechanism of the nanofiber with the core-shell structure is as follows: when the gas to be detected which is introduced into the gas conduit 2 is nonspecific sensitive gas or specific sensitive gas with constant concentration, the air pressure in the cavity is increased, the elastic membrane 5 expands and stretches the gas-sensitive film 3 at the same time, the piezoelectric layer 6 in the gas-sensitive film 3 generates polarization charges, and a small amount of induction charges are generated on the interdigital electrode 4 due to incomplete electrostatic shielding of the gas-sensitive layer 8, so that an output electric signal is generated; along with the increase of the air pressure, the larger the stretching deformation degree of the air-sensitive film is, the more the generated polarization charges are, and the larger the output electric signal is, so that the measurement of the air pressure of the introduced air can be realized by detecting the output electric signals at the two ends of the interdigital electrode.
The gas-sensitive mechanism of the nanofiber with the core-shell structure is as follows: when the gas to be detected introduced into the gas conduit 2 is a specific sensitive gas, the elastic membrane 5 expands under the action of the pressure difference, and accordingly the gas-sensitive film 3 is stretched, so that the piezoelectric layer 6 in the gas-sensitive film generates polarization charges, only a small amount of induction charges are generated on the interdigital electrode due to the electrostatic shielding action of the conductive gas sensitive layer 8, and the gas to be detected reacts with the gas sensitive layer to change the conductivity of the gas sensitive layer and further change the electrostatic shielding effect of the gas sensitive layer, so that the amount of the induction charges generated on the interdigital electrode changes, the output electric signal changes, the more violent the reaction between the gas to be detected and the gas sensitive layer 8 is along with the increase of the concentration of the gas to be detected in the introduced gas, the more the conductivity change of the gas sensitive layer is, and the weakening change of the electrostatic shielding effect on the polarization charges is strengthened, the variation of the number of the induced charges generated on the interdigital electrode is increased, and the variation of the output electric signal is increased, so that when the gas to be measured is introduced, the concentration of the gas to be measured can be measured by measuring the output electric signal.
Optionally, the PDA layer 7 has excellent hydrophilicity and adhesiveness, which is beneficial to preparing the gas sensitive layer 8 on the PDA layer 7 and enhancing the stability of the core-shell structured nanofiber;
the gas sensitive layer 8 is made of a gas sensitive material with good conductivity (>5S/cm), can play a role in electrostatic shielding of polarization charges at two ends of the internal piezoelectric layer 6, and changes the electrostatic shielding effect on the piezoelectric core by utilizing the change of the conductivity of the gas sensitive layer 8 along with the concentration of the specific sensitive gas.
Optionally, the preparation method of the gas-sensitive film 3 comprises the following steps: firstly, preparing a piezoelectric layer 6 and a DA (dopamine) layer by adopting an electrostatic spinning method, then forming a PDA layer 7 in Tris (Tris) buffer solution) through self-polymerization of DA, and finally preparing a gas sensitive layer 8 through in-situ self-assembly of aniline monomers under an acidic condition.
Optionally, the porosity of the spinning film can be adjusted by adjusting the electrostatic spinning time for 3-15min, so that the output response of the gas-sensitive film is regulated and controlled; the thickness degree of spinning fibers can be adjusted by adjusting the spinning voltage of 15-20kV and the advancing speed of 5-15 muL/min, and the thickness, porosity and surface area of the adsorbent of the gas sensitive layer are adjusted by adjusting the self-polymerization time of DA for 15-20h, so that the thickness ratio of the piezoelectric layer core to the gas sensitive layer shell is adjusted.
Optionally, the gas-sensitive film 3 can be prepared by using coaxial electrospinning, the inner layer of the spinning equipment is used for preparing a core piezoelectric material, the outer layer of the spinning equipment is used for preparing a gas-sensitive shell, and the thickness ratio of the piezoelectric layer core to the gas-sensitive shell can be adjusted to be 0.2-0.8 through the size of the inner and outer layer needles, so that the optimized self-driven gas-sensitive test is realized.
Optionally, the thickness of the interdigital electrode is 100nm-200nm, the radius is 3.0-3.6cm, the width of the interdigital is 0.05-0.2mm, the gap of the interdigital is 0.04-0.16mm, and the duty ratio of the interdigital electrode is 35-55%.
Alternatively, the interdigital electrode 4 is prepared on the elastic membrane 5 by means of screen printing or evaporation.
Optionally, the material of the interdigital electrode 4 is silver, copper, gold, aluminum, or the like;
optionally, the material of the piezoelectric layer 6 is an organic polymer or organic composite material with piezoelectric properties, such as PVDF, PVDF-TrFE, BTO/PVDF, PZT/PVDF, or the like.
Optionally, the material of the gas sensitive layer 8 is an organic polymer, a metal oxide or an inorganic material having good gas selectivity for the gas to be detected and high conductivity, such as polyaniline, polypyrrole, graphene, reduced graphene oxide, a composite material of carbon nanotubes or MXene, and the like.
As shown in fig. 3, a second embodiment of the present invention provides a method for preparing a flexible film type self-driven multifunctional sensor, comprising the following steps:
(1) a piece of flexible substrate with the thickness of 1mm and a latex film with the thickness of 50um are cleaned by chemical reagents such as deionized water, ethanol and the like and dried.
(2) The washed latex film was cut into a square structure of 4cm × 4cm with a laser cutter, the flexible substrate was cut into a square structure of 4cm × 4cm and a circular vent hole having a diameter of 4mm was cut in the center.
(3) And evaporating a layer of interdigital electrode with a spiral structure on a latex film with the thickness of 4cm multiplied by 4cm by thermal evaporation.
(4) The gas-sensitive film is prepared on the surface of the latex film plated with the interdigital electrode, so that the latex film can be stretched while the latex film expands when the air pressure in the cavity is increased.
(5) Fixing one surface of the latex film plated with the interdigital electrode and the edge of the flexible substrate by using epoxy resin, inserting a gas conduit into a vent hole of the flexible substrate, and expanding and contracting the latex film under the action of air flow.
(6) When ammonia gas or other gases with constant concentration are introduced, the electric signals at the two ends of the interdigital electrode are changed along with the difference of the gas pressure; when certain volume of ammonia gas with different concentrations is introduced, the electric signals at the two ends of the interdigital electrode are increased along with the increase of the concentration of the ammonia gas. And detecting output electric signals at two ends of the interdigital electrode through a digital electrometer so as to deduce the pressure and concentration of the introduced ammonia.
In the above examples, the preparation process of the gas-sensitive film is as follows:
(1) taking laboratory wares such as beakers and the like, cleaning the laboratory wares with deionized water and industrial alcohol, and drying the laboratory wares for later use.
(2) 3.442g of PVDF crystals were added to 20mL of a mixture with a volume fraction of 1: 1 of Dimethylacetamide (DMAC) and acetone for 1 hour in a water bath condition at 50 ℃, then 1.721g of dopamine powder is added and stirred for 2 hours under the same condition, and a DA/PVDF mixed solution is obtained.
(3) Standing the DA/PVDF mixed solution for five minutes to remove bubbles, pouring the solution into a 10mL BD plastic syringe, completely discharging the air in the syringe, fixing the syringe on a propulsion pump of an electrostatic spinning universal machine, and connecting the syringe with a flat-head needle of 0.5mm by using polytetrafluoroethylene capillary tubes with the inner diameter and the outer diameter of 1.5mm and 1.9mm respectively. Then, the distance between the needle and the aluminum foil collecting plate was adjusted to 15cm, the speed of the propeller pump was adjusted to 10. mu.L/min, and the voltage applied by the external high voltage source was set to 18 kV. Under the above conditions, electrostatic spinning was performed for 6 minutes to prepare a DA/PVDF mixed solution into a spun film.
(4) Dissolving 500mg Tris (trihydroxy aminomethane) in 400mL Ultrapure (UP) water to prepare a Tris buffer solution, soaking the spinning film in the Tris buffer solution for 20h, taking out the spinning film, washing the spinning film with ultrapure water to remove the redundant Tris buffer solvent, and drying the spinning film in a drying oven for 4 h.
(5) 2.27g of ammonium persulfate was dissolved in 20mL of 2mol/L dilute hydrochloric acid solution to obtain an ammonium persulfate solution, and 1mL of aniline monomer was dissolved in 200mL of 2mol/L dilute hydrochloric acid to obtain an aniline solution. The dried film was placed in an aniline solution under ice bath (0 ℃), an ammonium persulfate solution was added dropwise until the solution became light blue, and the film was taken out after the solution became dark blue. And (5) drying the film in a drying oven at 60 ℃ for 4h to finish the preparation of the gas-sensitive film.
The self-driven multifunctional sensor prepared in the above example has a size of 4cm × 4cm × 0.2 cm.
The sensing mechanism of the self-driven multifunctional ammonia gas sensor prepared by the second embodiment of the invention is shown in fig. 4. When dry air is introduced, the cavity between the latex film and the flexible substrate is of a closed structure, so that the air pressure in the cavity is increased, and the latex film expands. The latex film expands and simultaneously drives the gas-sensitive film attached to the latex film to stretch together, so that the piezoelectric layer in the gas-sensitive film is polarized, and piezoelectric charges with opposite polarities are generated at two ends of the piezoelectric fibers. The gas sensitive layer on the outer layer of the gas sensitive film has larger conductivity, so that the electrostatic shielding effect on piezoelectric charges is achieved, and the charges at the two ends of the piezoelectric fibers can only form a small amount of induced charges on the interdigital electrodes to generate smaller output electric signals. The more polarization charges are generated by the piezoelectric layer along with the increase of the air pressure of the introduced dry air, the stronger the output electric signal is generated. The output electric signals at the two ends of the interdigital electrode are detected by a digital electrometer, and the gas pressure of the introduced gas can be deduced.
When the introduced gas contains ammonia, the ammonia can react with a gas sensitive layer on the outer layer of the gas sensitive film, and the conductivity of the gas sensitive layer is reduced after the gas sensitive layer is made of a P-type material and reacts with the ammonia, so that the electrostatic shielding effect on the piezoelectric spinning is weakened, induced charges are induced on the interdigital electrodes, and an output electric signal is generated. And with the increase of the concentration of the ammonia gas, the reaction with the outer gas sensitive layer is more violent, and the weakening of the electrostatic shielding is more obvious, so that more induced charges can be induced on the interdigital electrode to generate a stronger output electric signal. The concentration of the ammonia gas in the introduced gas can be deduced by detecting the output electric signals at the two ends of the interdigital electrode through a digital electrometer.
The invention discloses a flexible film type self-driven multifunctional sensor and a preparation method thereof.
The invention has the advantages that: compared with the traditional sensor, the sensor adopts a centrosymmetric structure to maximize the electromechanical transduction efficiency of the electrostatic spinning distributed in a disordered manner, and the gas adsorption process is actively reflected into the output electric signal of the piezoelectric nano generator by utilizing the coupling action of gas chemical adsorption and piezoelectric effect, so that the detection of the concentration and the air pressure of the gas to be detected can be realized without an additional power supply system. The multifunctional self-driven sensor provided by the invention has the advantages of simple preparation, low cost, novel structure and high practicability, and fully utilizes the kinetic energy of gas flow.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used merely for convenience of description and for simplicity of description, and do not indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention.
In the present invention, unless otherwise explicitly specified or limited, a first feature may be "on" or "under" a second feature in direct contact with the first and second features, or in indirect contact with the first and second features through an intermediate. Also, a first feature "on," "above," and "over" a second feature may be directly or obliquely above the second feature, or may simply mean that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, but rather as the subject matter of the invention is to be construed as broadly as the appended claims.
Claims (9)
1. A flexible film type self-driven multifunctional sensor is characterized by comprising a flexible substrate (1), a gas conduit (2), a gas-sensitive film (3), interdigital electrodes (4) and an elastic film (5);
the flexible substrate (1) is provided with a vent hole for inserting the gas conduit (2), the interdigital electrode (4) is a center-symmetrical interdigital electrode with a spiral structure, the interdigital electrode (4) is positioned on the elastic membrane (5), the gas-sensitive film (3) is positioned on one surface of the elastic membrane (5) with the interdigital electrode (4), the gas-sensitive film (3) is formed by interweaving a plurality of nano fibers with a core-shell structure, and the nano fibers with the core-shell structure are a piezoelectric layer (6), a PDA (poly dopamine) layer (7) and a gas sensitive layer (8) from inside to outside in sequence;
the edge of one surface, provided with the interdigital electrodes (4), of the elastic membrane (5) is sealed and fixed with the edge of the flexible substrate (1), so that a cavity is formed between the flexible substrate (1) and the elastic membrane (5), when gas is introduced into the cavity through the gas conduit (2), the elastic membrane (5) expands and contracts under the action of gas flow, and meanwhile, the gas-sensitive film (3) attached to the elastic membrane (5) is stretched and restored, so that polarization charges are generated at two ends of the piezoelectric layer (6), and further, the conversion from gas kinetic energy to device electric energy is realized, and the gas pressure and the gas concentration are spontaneously and actively detected.
2. The flexible thin film type self-driven multifunctional sensor according to claim 1, wherein the PDA layer (7) has excellent hydrophilicity and adhesiveness, which facilitates the preparation of the gas sensitive layer (8) on the PDA layer (7) and enhances the stability of the core-shell structure nanofiber;
the gas sensitive layer (8) is made of a gas sensitive material with the conductivity of more than 5S/cm, can play a role in electrostatic shielding of polarization charges at two ends of the internal piezoelectric layer (6), and changes the electrostatic shielding effect on the piezoelectric core by utilizing the change of the conductivity of the gas sensitive layer (8) along with the concentration of the specific sensitive gas.
3. The flexible film type self-driven multifunctional sensor according to claim 1, wherein the interdigital electrode (4) is in a centrosymmetric spiral structure to collect anisotropic air pressure sensitive film expansion mechanical energy, and the air pressure sensitive mechanism of the nanofiber with the core-shell structure is as follows: when the gas to be detected introduced into the gas conduit (2) is nonspecific sensitive gas or specific sensitive gas with constant concentration, the air pressure in the cavity is increased, the elastic membrane (5) expands and stretches the gas-sensitive membrane (3), the piezoelectric layer (6) in the gas-sensitive membrane (3) generates polarization charges, and a small amount of induction charges are generated on the interdigital electrode (4) due to incomplete electrostatic shielding of the gas-sensitive layer (8), so that an output electric signal is generated; along with the increase of the air pressure, the larger the stretching deformation degree of the air-sensitive film is, the more the generated polarization charges are, and the larger the output electric signal is, so that the measurement of the air pressure of the introduced air can be realized by detecting the output electric signals at the two ends of the interdigital electrode.
4. The flexible film type self-driven multifunctional sensor according to claim 2, wherein the gas-sensitive mechanism of the nanofibers with the core-shell structure is as follows: when the gas to be detected introduced into the gas conduit (2) is a specific sensitive gas, the elastic membrane (5) expands under the action of the gas pressure difference, and correspondingly the gas sensitive film (3) is stretched to cause the piezoelectric layer (6) inside the gas sensitive film to generate polarization charges, only a small amount of induction charges are generated on the interdigital electrode due to the electrostatic shielding effect of the conductive gas sensitive layer (8), and the gas to be detected reacts with the gas sensitive layer to change the conductivity of the gas sensitive layer and further change the electrostatic shielding effect of the gas sensitive layer, so that the induction charge generated on the interdigital electrode changes, the output electric signal changes, and the weakening change of the electrostatic shielding effect of the polarization charges is enhanced as the reaction of the gas to be detected and the gas sensitive layer (8) is increased along with the increase of the concentration of the gas to be detected in the introduced gas, the electric conductivity of the gas sensitive layer changes more violently, the number of the induced charges generated on the interdigital electrode is increased, and the change range of the output electric signal is increased, so that when the gas to be measured is introduced, the concentration of the gas to be measured can be measured by measuring the output electric signal.
5. The flexible film self-driven multifunctional sensor according to claim 2, wherein the preparation method of the gas-sensitive film (3) comprises the following steps: firstly, preparing a piezoelectric layer (6) and a DA (dopamine) layer by adopting an electrostatic spinning method, then forming a PDA layer (7) in Tris (Tris (hydroxymethyl aminomethane) buffer solution through self-polymerization of DA, and finally preparing a gas sensitive layer (8) through in-situ self-assembly of aniline monomers under an acidic condition.
6. The flexible film type self-driven multifunctional sensor as claimed in claim 5, wherein the porosity of the spun film can be adjusted by adjusting the time of electrostatic spinning for 3-15min, thereby adjusting the output response of the gas-sensitive film; the thickness degree of spinning fibers can be adjusted by adjusting the spinning voltage of 15-20kV and the advancing speed of 5-15 muL/min, and the thickness, porosity and surface area of the adsorbent of the gas sensitive layer are adjusted by adjusting the self-polymerization time of DA for 15-20h, so that the thickness ratio of the piezoelectric layer core to the gas sensitive layer shell is adjusted.
7. The flexible film type self-driven multifunctional sensor as claimed in claim 2, wherein the gas sensitive film (3) can be prepared by using coaxial electrospinning, the inner layer of the spinning device is used for preparing a core piezoelectric material, the outer layer of the spinning device is used for preparing a gas sensitive shell layer, and the thickness ratio of the piezoelectric layer core to the gas sensitive shell layer can be adjusted to be 0.2-0.8 through the size of the inner and outer layer needles, so as to realize the optimized self-driven gas sensitive test.
8. A preparation method of a flexible film type self-driven multifunctional sensor is characterized by comprising the following steps:
step 1: preparing an interdigital electrode (4) on an elastic membrane (5), wherein the interdigital electrode (4) is a centrosymmetric interdigital electrode with a spiral structure, and a vent hole is cut on a flexible substrate (1);
step 2: preparing a gas-sensitive film (3) on one surface of the elastic film (5) with the interdigital electrodes (4), so that the gas-sensitive film can be stretched while the elastic film expands when the air pressure in the cavity is increased, wherein the gas-sensitive film (3) is formed by interweaving a plurality of core-shell structure nanofibers, and the core-shell structure nanofibers are a piezoelectric layer (6), a PDA layer (7) and a gas sensitive layer (8) from inside to outside in sequence;
and step 3: will elastic membrane (5) have the edge of the one side of interdigital electrode (4) with the edge seal of flexible basement (1) is fixed, inserts gas conduit (2) in the air vent of flexible basement (1), thereby flexible basement (1) with form the cavity between elastic membrane (5), pass through gas conduit (2) to when the cavity lets in the gas that awaits measuring, make under the effect of air current elastic membrane (5) take place to expand and contract, along with letting in the difference of the sensitive gas concentration of specificity in the gas that awaits measuring or the difference of atmospheric pressure, the output signal of telecommunication of interdigital electrode changes, through the output signal of detecting interdigital electrode both ends, realizes the detection to the gas concentration that awaits measuring and atmospheric pressure.
9. The method for preparing a flexible film type self-driven multifunctional sensor according to claim 1, wherein the method for preparing the gas-sensitive film (3) comprises the following steps:
step 11: using 10-50mL of a mixture with the volume ratio of 1: 1, taking DMAC and acetone as solvents, preparing PVDF (polyvinylidene fluoride) crystal into 10-30 wt% PVDF solution by using a magnetic stirrer to magnetically stir for 1-3h under the water bath heating condition of 40-60 ℃, adding dopamine hydrochloride (DA & HCL) powder into the PVDF solution, and stirring for 1-3h under the water bath heating condition of 40-60 ℃ to obtain DA/PVDF mixed solution, wherein the mass ratio of dopamine to PVDF is 1: 3-1: 1;
step 12: preparing the DA/PVDF mixed solution into a spinning film by adopting an electrostatic spinning method;
step 13: dissolving Tris (Tris hydroxymethyl aminomethane) in 250-1250mL of Ultrapure (UP) water to prepare 1.0-1.5mg/mL of Tris buffer solution, soaking the spinning film in the Tris buffer solution for 15-25h, then washing off redundant Tris solution by using ultrapure water and drying;
step 14: dissolving aniline monomer in 100-500mL dilute hydrochloric acid to prepare aniline solution with relative volume fraction of 0.25-0.75%, dissolving ammonium persulfate in 10-50mL of 2mol/L dilute hydrochloric acid solution to prepare 0.25-0.75mol/L ammonium persulfate solution, placing the spinning film treated in the step 13 in the aniline solution under the condition of ice bath (0 ℃), dropwise adding the ammonium persulfate solution until the solution is light blue, and taking out the spinning film after the solution becomes dark blue;
step 15: and (3) drying the spinning film treated in the step (14) in a drying oven at the temperature of 50-70 ℃ for 3-5h, and finishing the preparation of the gas-sensitive film.
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