CN115058049A - Variable gradient structure flexible aerogel, preparation method thereof and flexible pressure sensor - Google Patents

Variable gradient structure flexible aerogel, preparation method thereof and flexible pressure sensor Download PDF

Info

Publication number
CN115058049A
CN115058049A CN202210651669.1A CN202210651669A CN115058049A CN 115058049 A CN115058049 A CN 115058049A CN 202210651669 A CN202210651669 A CN 202210651669A CN 115058049 A CN115058049 A CN 115058049A
Authority
CN
China
Prior art keywords
aerogel
flexible
gradient
layer
dimensional
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
CN202210651669.1A
Other languages
Chinese (zh)
Other versions
CN115058049B (en
Inventor
张开富
牛英杰
王春江
易城林
程晖
骆彬
程毅
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Shenzhen Institute of Northwestern Polytechnical University
Original Assignee
Shenzhen Institute of Northwestern Polytechnical University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Shenzhen Institute of Northwestern Polytechnical University filed Critical Shenzhen Institute of Northwestern Polytechnical University
Priority to CN202210651669.1A priority Critical patent/CN115058049B/en
Publication of CN115058049A publication Critical patent/CN115058049A/en
Application granted granted Critical
Publication of CN115058049B publication Critical patent/CN115058049B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/26—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a solid phase from a macromolecular composition or article, e.g. leaching out
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
    • G01L9/02—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning
    • G01L9/04—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning of resistance-strain gauges
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2329/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
    • C08J2329/02—Homopolymers or copolymers of unsaturated alcohols
    • C08J2329/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2375/00—Characterised by the use of polyureas or polyurethanes; Derivatives of such polymers
    • C08J2375/04—Polyurethanes
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K2201/00—Specific properties of additives
    • C08K2201/001—Conductive additives
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K2201/00—Specific properties of additives
    • C08K2201/011—Nanostructured additives
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/02—Elements
    • C08K3/04—Carbon
    • C08K3/042—Graphene or derivatives, e.g. graphene oxides
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/10—Metal compounds
    • C08K3/14—Carbides
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K7/00—Use of ingredients characterised by shape
    • C08K7/02—Fibres or whiskers
    • C08K7/04—Fibres or whiskers inorganic
    • C08K7/06—Elements
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/54—Improvements relating to the production of bulk chemicals using solvents, e.g. supercritical solvents or ionic liquids

Abstract

The invention relates to the technical field of sensors, and provides a gradient-structure-variable flexible aerogel, a preparation method thereof and a flexible pressure sensor. The method adopts a polymer matrix, a two-dimensional nano material and an organic solvent to prepare the aerogel liquid, and obtains the gradient-structure-variable flexible aerogel by changing the proportion of the polymer or the two-dimensional nano material in the aerogel liquid and based on a freeze-drying multilayer integrated forming technology, an ultrasonic dipping technology and a low-temperature annealing technology. This become flexible aerogel of gradient structure is multilayer body structure, and each layer has different density and structure, and the microcosmic aperture of each layer is also different, demonstrates different piezoelectric property, is applied to flexible pressure sensor with it, and gained sensor sensitivity is high, can accomplish the sensitive detection of gradient to the external stimulus of different pressure sizes. And the sensor has simple manufacturing process, convenient operation, light weight, no toxic substances and lower cost, and provides a technical basis for manufacturing wearable sensing equipment.

Description

Variable gradient structure flexible aerogel, preparation method thereof and flexible pressure sensor
Technical Field
The invention relates to the technical field of sensors, in particular to a gradient-variable structure flexible aerogel, a preparation method thereof and a flexible pressure sensor.
Background
With the rapid development of the flexible electronic field and the continuous popularization of the internet of things technology, wearable electronic devices which can be applied to the fields of medical diagnosis, physiological state monitoring, motion behavior assessment and the like gradually step into the production and life of human beings. The wearable electronic device can quantize related physical signals, converts external stimulation information into electrical signals such as resistance, capacitance and current which can be observed in real time, plays a vital role in establishing a bidirectional information channel of a man/machine control interface, and the rapid manufacturing of the related functional flexible sensing device gradually becomes a research hotspot in recent years.
Flexible pressure sensors can be classified into piezoresistive, capacitive, piezoelectric, and frictional types, depending on the sensing mechanism. The piezoresistive sensor is mainly characterized by measuring the change of resistance to represent external stimulation, mainly comprises a nano material deposited on a substrate or embedded in the substrate, and the nano material and a polymer generate slippage under the stimulation of external mechanical force to further cause the change of a conductive path so as to realize the change of the resistance value. In a capacitive sensor, an elastic dielectric medium is deformed by an external force, so that the distance between electrodes is shortened to change capacitance. The piezoelectric sensor is mainly based on the piezoelectric property of a non-centrosymmetric material, and when the piezoelectric sensor is acted by an external force, a material crystal generates dipole moment so as to generate a macroscopic potential in the material. The triboelectric sensors generate different positive and negative charges by different physical bonds mainly through contact or electrostatic induction.
The piezoresistive flexible pressure sensor has the remarkable advantages of simple structure, convenience in signal detection, low energy consumption and the like, and has wide application prospect in wearable electronic devices. In recent years, great progress is made in wearable flexible pressure sensors researched and developed to a certain extent, and the existing flexible pressure sensors are closer to production and life. However, the flexible pressure sensor currently under study generally has the following problems:
(1) the sensitivity is low; the working mode of the piezoresistive flexible pressure sensor mainly depends on the change of the material resistance of the piezoresistive flexible pressure sensor, a composite structure which fills a conductive material into a polymer body is generally adopted, and the change of the piezoresistive property of the composite material is analyzed to obtain external pressure information. Due to the fact that the Young modulus and the viscoelasticity of the polymer material are large, even if the conductive material is added, the flexible pressure sensor prepared based on the composite material is low in sensitivity and slow in response. The application prospect of the sensor is very limited due to the sensitivity problem, and particularly, the sensing capability of the sensor is greatly reduced aiming at the tiny pressure generated by the life activities of the human body, such as respiration, heartbeat, sounding and the like, so that the real-time monitoring and feedback of the physiological life of the human body cannot be realized.
(2) The gradient sensitive detection capability is not available; the detection range of the existing flexible pressure sensor is narrow, most of the flexible pressure sensors are used for detecting external stimulation in a specific pressure range, the sensors generally used for detecting small pressure lose the detection capability when being greatly stimulated, and the flexible pressure sensor capable of detecting large external stimulation cannot realize sensitive detection on the external small stimulation, so that the flexible pressure sensor of the type cannot be applied to the field of wearable electronics.
(3) The sensing layer is single and cannot be adjusted, so that the sensing effect is influenced; the sensing layer of a typical sandwich-structured flexible pressure sensor is of a single-layer structure, is prepared by fixed materials and proportions, has no controllability, and the final performance of the sensor is determined by the single microstructure and density of the sensor.
Therefore, how to design and prepare a flexible pressure sensor with a controllable structure and a variable gradient structure to ensure that the flexible pressure sensor has higher sensitivity and the gradient sensitive detection is still achieved aiming at external stimuli with different pressures becomes a problem worthy of research.
Disclosure of Invention
In view of the above, the invention provides a flexible aerogel with a variable gradient structure, a preparation method thereof and a flexible pressure sensor. The flexible aerogel provided by the invention has a variable gradient structure, each layer can present different piezoelectric characteristics, and the flexible aerogel is applied to a flexible pressure sensor, so that the obtained flexible pressure sensor has high sensitivity, and can perform gradient sensitive detection aiming at external stimulation with different pressures.
A preparation method of a flexible aerogel with a variable gradient structure comprises the following steps:
(1) pouring the aerogel collagen liquid into a mould to be frozen and then freeze-drying to obtain a polymer-nano material aerogel layer; the components of the aerogel collagen liquid comprise a polymer matrix, a two-dimensional nano material and an organic solvent;
(2) repeating the step (1) for more than or equal to 1 time to obtain the multilayer integrated polymer-nano material aerogel; in the multilayer integrated polymer-nano material aerogel, the content of polymer matrixes and/or two-dimensional nano materials in aerogel liquid adopted for preparing each layer of aerogel is different;
(3) carrying out first annealing on the multilayer integrated polymer-nano material aerogel to obtain a gradient-variable flexible three-dimensional piezoelectric framework;
(4) and ultrasonically dipping the gradient-variable flexible three-dimensional piezoelectric framework in a two-dimensional conductive material solution, and then carrying out secondary annealing and drying to obtain the gradient-variable structure flexible aerogel.
Preferably, the polymer matrix comprises one or more of polyurethane, polyvinyl alcohol and polydimethylsiloxane; the two-dimensional nano material comprises one or two of graphene and reduced graphene oxide; the organic solvent includes one or both of dioxane and N, N-dimethylformamide.
Preferably, in the aerogel collagen liquid used in the steps (1) to (2), the mass ratio of the polymer matrix to the organic solvent is (1-5): 50-100, and the mass ratio of the polymer matrix to the two-dimensional nanomaterial is (100-200): 1-10.
Preferably, the mass fraction of the polymer matrix or the two-dimensional nanomaterial in the aerogel collagen liquid used in each layer sequentially increases or decreases from bottom to top.
Preferably, the variation of the polymer matrix and the two-dimensional nanomaterial in the aerogel liquid used for preparing each layer of aerogel comprises the following three types in the order from bottom to top:
the first method is as follows: the content of the polymer matrix in the aerogel collagen liquid used in each layer is the same, and the content of the two-dimensional nano materials is increased or decreased in sequence;
the second method comprises the following steps: the content of the two-dimensional nano material in the aerogel collagen liquid used in each layer is the same, and the content of the polymer matrix is increased or decreased in sequence;
the third method comprises the following steps: the polymer matrix and the two-dimensional nano material in the aerogel collagen liquid used in each layer have the same proportion, and the content of the polymer matrix and the content of the two-dimensional nano material are sequentially increased or decreased simultaneously.
Preferably, the freezing includes liquid nitrogen freezing and pre-freezing in sequence, and the liquid nitrogen freezing specifically includes: placing the mould filled with the aerogel collagen liquid in liquid nitrogen to enable the aerogel original liquid to be instantly frozen; the pre-freezing temperature is-20 to-30 ℃, and the time is more than 12 hours;
the temperature of the freeze drying is-50 to-75 ℃, and the time is more than 72 hours.
Preferably, the two-dimensional conductive material comprises one or more of MXENE, graphene, reduced graphene oxide and silver nanowires.
The invention also provides the gradient-structure-variable flexible aerogel prepared by the preparation method in the scheme.
The invention also provides a flexible pressure sensor which comprises a lower packaging layer, a lower electrode layer, the gradient-structure-variable flexible aerogel, an upper electrode layer and an upper packaging layer which are sequentially stacked; the lower electrode layer and the upper electrode layer are connected with a lead; the lead is connected with an electric signal measuring device.
The invention also provides a preparation method of the flexible pressure sensor, which is characterized by comprising the following steps of:
preparing a lower electrode layer and an upper electrode layer on the surfaces of two sides of the flexible aerogel with the variable gradient structure by adopting an evaporation or sputtering method;
and connecting wires on the lower electrode layer and the upper electrode layer, connecting the wires with an electric signal measuring device, and preparing a lower packaging layer and an upper packaging layer on the surfaces of the lower electrode layer and the upper electrode layer by adopting a spin coating and curing method to obtain the flexible pressure sensor.
The invention provides a preparation method of a variable gradient structure flexible aerogel, which adopts a polymer matrix, a two-dimensional nano material and an organic solvent to prepare aerogel collagen liquid, and obtains the variable gradient structure flexible aerogel by changing the proportion of the polymer or the two-dimensional nano material in the aerogel collagen liquid and based on a freeze-drying multilayer integrated molding technology, an ultrasonic dipping technology and a low-temperature annealing technology. According to the invention, the mechanical property of the polymer is improved by using the two-dimensional nano material, and meanwhile, the controllable adjustment of the micro-pore size of the aerogel is realized by changing the adding proportion of the two-dimensional nano material in different layers and freeze-drying integrated molding, so that the structure controllability is realized, the pore structure and the number of layers of the aerogel can be flexibly adjusted and controlled according to actual requirements, and each layer has different piezoelectric properties, thereby realizing the sensing and accurate detection aiming at different pressure signals; in addition, the invention carries out freeze drying in the preparation process of each layer of aerogel, then carries out the preparation of the next layer of aerogel layer, and solves the problem of difficult molding when the aerogels with different characteristics are integrally molded based on freeze drying in the prior art through multi-step freeze drying, thereby avoiding the mutual solubility of different solvents; by means of the method of dipping the conductive solution by ultrasound, the piezoelectric property of the aerogel is greatly improved, the sensing detection range of the sensor is remarkably improved, and the gradient sensitive detection capability is realized. The preparation method of the variable gradient structure flexible aerogel provided by the invention is simple, convenient and fast, reasonable in scheme, convenient to operate and easy to realize mechanized production and popularization.
The invention also provides the variable gradient structure flexible aerogel prepared by the preparation method in the scheme, the variable gradient structure flexible aerogel provided by the invention has conductivity, compressibility and automatic recovery, and can be cut into any shape according to requirements, and meanwhile, the aerogel has a three-dimensional mesh porous structure, and the pore size of the aerogel is controllable; in addition, the gradient-structure-variable flexible aerogel is a multilayer integrated structure, each layer has different densities and structures, and the sizes of microscopic apertures of the structures of each layer are different, so that different piezoelectric properties are presented.
The invention also provides a flexible pressure sensor and a preparation method thereof, the flexible pressure sensor provided by the invention comprises a lower packaging layer, a lower electrode layer, the gradient-structure-variable flexible aerogel, an upper electrode layer and an upper packaging layer which are sequentially stacked, a lead and an electric signal measuring device. According to the invention, the gradient-variable structure flexible aerogel is applied to the flexible pressure sensor, the sensitivity of the obtained flexible pressure sensor is high, and the gradient sensitivity detection can be realized aiming at external stimuli with different pressures. The flexible pressure sensor provided by the invention does not contain any toxic substance, has the characteristics of biological friendliness and environmental friendliness, is based on the flexible aerogel, has light weight, and is suitable for monitoring human health signals and manufacturing a bionic structure; in addition, the flexible piezoelectric sensor is packaged by adopting a sandwich structure, so that the flexibility and the stretchability of the sensor are improved, and a technical basis is provided for manufacturing wearable sensing equipment.
Drawings
FIG. 1 is a process flow diagram for manufacturing a variable gradient flexible pressure sensor according to an embodiment of the present invention;
FIG. 2 is a flow chart of a process for manufacturing a gradient-variable flexible three-dimensional piezoelectric skeleton according to an embodiment of the present invention;
FIG. 3 is a schematic view of the microstructure of a variable gradient flexible three-dimensional piezoelectric skeleton;
FIG. 4 is an SEM image of the bottom, middle and top aerogels of the gradient flexible three-dimensional piezoelectric framework prepared in example 1;
FIG. 5 is a schematic illustration of an ultrasonic dipping process;
FIG. 6 is a schematic view of the microstructure of a flexible aerogel with a variable gradient structure;
FIG. 7 is a schematic structural diagram of a flexible pressure sensor provided by the present invention;
FIG. 8 is a graph of the rate of change of resistance at different pressures for the G-TPU-MXENE flexible pressure sensor prepared in example 1;
FIG. 9 is a graph of the rate of change of resistance at different pressures for the G-PVA-AgNWS flexible pressure sensor prepared in example 2;
FIG. 10 is a graph of the rate of change of resistance at different pressures for the RGO-TPU/PVA-MXENE flexible pressure sensor prepared in example 3;
in fig. 2, 5 and 7: 1-mould, 2-freeze drying equipment, 3-vacuum drying oven, 4-gradient-variable flexible three-dimensional piezoelectric skeleton, 5-two-dimensional conductive material solution, 6-briquetting, 7-gradient-structure-variable flexible aerogel, 8-lower electrode layer, 9-upper electrode layer, 10-lower packaging layer, 11-upper packaging layer and 12-electric signal measuring device.
Detailed Description
The invention provides a preparation method of a gradient-structure-variable flexible aerogel, which comprises the following steps:
(1) pouring the aerogel collagen liquid into a mould to be frozen and then freeze-drying to obtain a polymer-nano material aerogel layer; the components of the aerogel collagen liquid comprise a polymer matrix, a two-dimensional nano material and an organic solvent;
(2) repeating the step (1) for more than or equal to 1 time to obtain the multilayer integrated polymer-nano material aerogel; in the repeated process, the polymer matrix and/or the two-dimensional nano material in the aerogel collagen liquid adopted by each layer have different proportions;
(3) carrying out first annealing on the multilayer integrated polymer-nano material aerogel to obtain a gradient-variable flexible three-dimensional piezoelectric framework;
(4) and ultrasonically dipping the gradient-variable flexible three-dimensional piezoelectric framework in a two-dimensional conductive material solution, and then carrying out secondary annealing to obtain the gradient-variable structure flexible aerogel.
The invention pours the aerogel collagen liquid into a mould to be frozen and then carries out freeze drying to obtain the polymer-nano material aerogel layer. In the invention, the constituents of the aerogel collagen liquid comprise a polymer matrix, two-dimensional nano materials and an organic solvent, wherein the polymer matrix preferably comprises one or more of polyurethane, polyvinyl alcohol and polydimethylsiloxane; the two-dimensional nanomaterial preferably comprises one or two of graphene and reduced graphene oxide; the organic solvent preferably includes one or both of dioxane and N, N-dimethylformamide. In the present invention, the preparation method of the aerogel collagen liquid is preferably: adding a polymer matrix into an organic solvent, stirring under a water bath condition until the polymer matrix is completely dissolved, then adding a two-dimensional nano material, and carrying out ultrasonic crushing on the obtained mixed feed liquid to obtain the aerogel stock solution; the temperature of the water bath is preferably 45 ℃, the ultrasonic disruption is preferably carried out in a cell disruptor, the amplitude of the ultrasonic disruptor is preferably 20mm in diameter, the output power is preferably 80%, and the time of ultrasonic disruption is preferably 1.5 h.
The invention has no special requirements on the shape and the size of the die, and the die with any shape can be adopted. Preferably, the mould is firstly cooled to below 0 ℃ in a refrigerator, and then the aerogel stock solution is poured in; the amount of the aerogel collagen liquid to be added is preferably determined according to the size of the mold, and the present invention is not particularly limited. In the present invention, the freezing preferably includes liquid nitrogen freezing and pre-freezing in sequence, and the liquid nitrogen freezing is particularly preferably: placing the mould filled with the aerogel collagen liquid in liquid nitrogen to enable the aerogel original liquid to be instantly frozen; the pre-freezing temperature is preferably-20 to-30 ℃, and the time is preferably more than 12 hours, and more preferably 12 to 24 hours; in the embodiment of the invention, the step of freezing by liquid nitrogen can be omitted, and the mould is directly pre-frozen. In the invention, the freeze drying temperature is preferably-50 to-75 ℃, the time is preferably more than 60 hours, more preferably 60 to 84 hours, and more preferably 60 to 72 hours, and in the embodiment of the invention, the complete drying is specifically guaranteed; the freeze-drying is preferably carried out in a vacuum freeze-dryer. After freeze-drying, the resulting aerogel layer was directly subjected to the subsequent steps without taking it out.
After the polymer-nanomaterial aerogel layer is obtained, the steps of pouring the aerogel stock solution into the mold, and then freezing and freeze-drying are repeated, wherein the repetition frequency is more than or equal to 1 time, preferably 1-10 times, more preferably 1-5 times, and further preferably 2-3 times, specifically, when the aerogel stock solution is added each time, the stock solution is poured above the aerogel layer obtained by the last freeze-drying, and the aerogel with the multilayer integrated structure is obtained by adding the stock solution for multiple times and freeze-drying for multiple times. Specifically, when the number of repetitions is 1, bilayer structure's integration aerogel can be obtained, when the number of repetitions is 2, three layer structure's integration aerogel can be obtained, analogize in proper order.
In the present invention, the above repetition process is carried out under the same conditions as in the above step (1), except that the content of the polymer matrix and/or the two-dimensional nanomaterial in the aerogel liquid used in each layer is changed, preferably, the content of the polymer matrix and/or the two-dimensional nanomaterial in the aerogel liquid used in each layer is sequentially increased or sequentially decreased in the order from bottom to top, and the amount of the organic solvent used in the aerogel liquid used in each layer is preferably the same. In the embodiment of the present invention, the variation of the polymer matrix and the two-dimensional nanomaterial in the aerogel liquid used for preparing each layer of aerogel preferably includes the following three types in the order from bottom to top:
the first method is as follows: the content of the polymer matrix in the aerogel collagen liquid used in each layer is the same, and the content of the two-dimensional nano materials is increased or decreased in sequence;
the second method comprises the following steps: the content of the two-dimensional nano material in the aerogel collagen liquid used in each layer is the same, and the content of the polymer matrix is increased or decreased in sequence;
the third method comprises the following steps: the polymer matrix and the two-dimensional nano material in the aerogel collagen liquid used in each layer have the same proportion, and the content of the polymer matrix and the content of the two-dimensional nano material are sequentially increased or decreased simultaneously.
The invention does not specifically require the variation amplitude of the polymer matrix and/or the two-dimensional nano material in the aerogel collagen liquid adopted when the two adjacent layers are prepared, and the variation amplitude can be any amplitude.
In the invention, in the aerogel collagen liquid adopted in the preparation process, the mass ratio of the polymer matrix to the organic solvent is preferably (1-5): (50-100), more preferably (2-4): 60-80), and the mass ratio of the polymer matrix to the two-dimensional nanomaterial is preferably (100-200): 1-10, more preferably (120-160): 2-8), that is, in the preparation process, the contents of the polymer matrix and the organic solvent in the aerogel collagen liquid adopted in each layer are different, but are all within the above ratio range.
After the multilayer integrated polymer-nano material aerogel is obtained, the multilayer integrated polymer-nano material aerogel is preferably subjected to first annealing to obtain the gradient-variable flexible three-dimensional piezoelectric framework. In the invention, the temperature of the first annealing is preferably 40-50 ℃, the time is preferably 0.5-1 h, and the first annealing is preferably carried out in a vacuum drying oven; according to the invention, the aerogel obtained after freeze drying is subjected to secondary drying through first annealing, the interlayer distance is enlarged, the sensitivity is further improved, and the lower first annealing temperature is controlled, so that the TPU is prevented from melting.
After the gradient-variable flexible three-dimensional piezoelectric framework is obtained, the gradient-variable flexible three-dimensional piezoelectric framework is ultrasonically dipped in a two-dimensional conductive material solution and then subjected to secondary annealing, so that the gradient-variable structure flexible aerogel is obtained. In the invention, the two-dimensional conductive material preferably comprises one or more of MXENE, graphene, reduced graphene oxide and silver nanowires; the solvent of the two-dimensional conductive material solution is preferably pure water; the concentration of the two-dimensional conductive material solution is preferably 10-30 mg/mL. In the present invention, the ultrasonic power of ultrasonic dipping is preferably 100W, the ultrasonic dipping is preferably performed at room temperature, and in the specific embodiment of the present invention, it is preferable to put a part of ice cubes during ultrasonic dipping to prevent the temperature of the system from rising; in a specific embodiment of the invention, preferably, the gradient-changing flexible three-dimensional piezoelectric framework is placed in a two-dimensional conductive material solution, the pressing block is placed on the gradient-changing flexible three-dimensional piezoelectric framework, so that the gradient-changing flexible three-dimensional piezoelectric framework can be completely suspended in the two-dimensional conductive material solution, then ultrasonic dipping is performed for 1.5 hours, then the gradient-changing flexible three-dimensional piezoelectric framework is turned over, and then ultrasonic dipping is continued for 1.5 hours. After ultrasonic dipping is finished, taking out the gradient-variable flexible three-dimensional piezoelectric framework adsorbed with the two-dimensional conductive material solution for second annealing; the second annealing temperature is preferably 50-60 ℃, and the time is preferably 1 h; the second annealing is preferably performed in a vacuum drying oven.
The invention also provides the gradient-structure-variable flexible aerogel prepared by the preparation method in the scheme, and the gradient-structure-variable flexible aerogel prepared by the invention integrally comprises a gradient flexible three-dimensional piezoelectric framework and a two-dimensional conductive material loaded in the gradient flexible three-dimensional piezoelectric framework; the gradient flexible three-dimensional piezoelectric framework is composed of a plurality of layers of integrated polymer-nano material aerogel layers, the number of the layers is preferably more than 2, each layer has different density and structure, the sizes of microscopic apertures of the structures of the layers are different, and different piezoelectric characteristics are presented. In the invention, the variable gradient structure flexible aerogel has conductivity, compressibility and self-recovery property, and simultaneously has a three-dimensional net-shaped porous structure. In addition, the gradient-structure-variable flexible aerogel provided by the invention can be cut into any shape according to requirements, and is not limited to a rectangular parallelepiped shape.
The invention also provides a flexible pressure sensor, which comprises a lower packaging layer, a lower electrode layer, the gradient-variable structure flexible aerogel, an upper electrode layer and an upper packaging layer which are sequentially stacked; the lower electrode layer and the upper electrode layer are connected with a lead; the lead is connected with an electric signal measuring device. In the present invention, the material of the lower electrode layer and the upper electrode layer is preferably copper or nickel; the materials adopted by the lower packaging layer and the upper packaging layer are preferably high polymer materials, and more preferably one or more of polyurethane (TPU), Epoxy resin (Epoxy), Polydimethylsiloxane (PDMS) and silicon rubber; the electric signal measuring device is a device for measuring contact electric signals and changes thereof between the electrode and the gradient-variable flexible aerogel, and can be a device well known by the technical personnel in the field, and specifically can be a voltage, current or resistance measuring device; the present invention has no special requirements on the thickness of the electrode layer and the packaging layer, and the thickness is known to those skilled in the art.
The invention also provides a preparation method of the flexible pressure sensor, which comprises the following steps:
preparing a lower electrode layer and an upper electrode layer on the surfaces of two sides of the flexible aerogel with the variable gradient structure by adopting an evaporation or sputtering method;
and connecting wires on the lower electrode layer and the upper electrode layer, connecting the wires with an electric signal measuring device, and preparing a lower packaging layer and an upper packaging layer on the surfaces of the lower electrode layer and the upper electrode layer by adopting a spin coating and curing method to obtain the flexible pressure sensor.
The present invention has no special requirement for the specific operation conditions of evaporation or sputtering, and the operation conditions known to those skilled in the art can be selected according to the materials of the lower electrode and the upper electrode. The present invention has no special requirement on the specific operation conditions of the spin coating and curing, and the spin coating process and the curing conditions which are well known to those skilled in the art can be adopted.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention.
Fig. 1 is a process flow diagram of preparing a variable gradient flexible pressure sensor in an embodiment of the present invention, in which aerogel collagen liquid is first prepared, then a variable gradient three-dimensional piezoelectric skeleton is obtained through layered freezing and low-temperature annealing, then a variable gradient structure flexible aerogel is obtained through ultrasonic dipping and low-temperature annealing (that is), and finally an electrode layer and a packaging layer are sequentially prepared, so as to obtain the variable gradient flexible pressure sensor.
Example 1
In this embodiment, a three-layer gradient-variable flexible aerogel is prepared by using graphene (G) as a two-dimensional nanomaterial, thermoplastic polyurethane elastomer rubber (TPU) as a polymer matrix, and MXENE as a conductive material, and is packaged by PDMS to complete the manufacturing and molding of the flexible pressure sensor, where the manufacturing process flow is shown in fig. 1, and includes the following steps:
firstly, preparing a G and TPU mixed flexible aerogel liquid
Measuring 45mL of dipentane solution in a measuring cylinder, dividing into three equal parts, pouring into three clean beakers, three portions of TPU particles accounting for 1.5 percent of the mass of 15mL of dipentane solution are weighed and respectively added into a beaker, placing the beaker in a magnetic stirring water bath kettle, setting the water bath temperature to be 45 ℃, placing a magneton, carrying out magnetic stirring for 6 hours to fully dissolve TPU particles, respectively weighing G powder accounting for 0.5 percent (bottom stock solution), 1.5 percent (middle stock solution) and 5 percent (top stock solution) of the mass of the TPU particles by using a balance, respectively pouring the G powder into three beakers, fully and uniformly stirring by using a glass rod, then placing the beakers in a cell disruptor, using a variable amplitude rod with the diameter of 20mm, and (3) carrying out ultrasonic crushing for 1.5h under the parameter of output power density of 80%, respectively obtaining uniform G and TPU mixed gradient structure aerogel bottom, middle and top stock solutions, wherein the content of G powder in the bottom, middle and top stock solutions is increased in sequence.
Secondly, preparing a gradient-variable flexible three-dimensional piezoelectric framework
Placing a cuboid cavity mold with the length of 8cm, the width of 1cm, the height of 6cm and the wall thickness of 0.1cm in a refrigerator for refrigeration, then pouring a bottom aerogel collagen solution mixed by G and TPU into the mold, then pouring sufficient liquid nitrogen into a large beaker, clamping the mold by using tweezers, placing the mold in the liquid nitrogen for instant freezing, then placing the mold in an environment with the temperature of minus 20 ℃ to minus 30 ℃ for pre-freezing for more than 12 hours for molding, then placing the pre-frozen product into a vacuum freeze dryer, and drying the product at the temperature of minus 50 ℃ to minus 75 ℃ for more than 72 hours to remove a dipentane solvent to form bottom TPU-G aerogel; taking out the mold, pouring the middle aerogel collagen solution mixed with the G and the TPU into the low-temperature mold, putting the mold into a liquid nitrogen environment for instantaneous freezing, then putting the mold into an environment with the temperature of minus 20 ℃ to minus 30 ℃ for pre-freezing for more than 12 hours for forming, putting the pre-frozen product into a vacuum freeze dryer, and drying the product at the temperature of minus 50 ℃ to minus 75 ℃ for more than 72 hours to remove a dipentane solvent to form the middle TPU-G aerogel; taking out the mold again, pouring the top aerogel collagen solution mixed with the TPU into the low-temperature mold, repeating the steps to prepare the top TPU-G aerogel, taking out the integrated TPU-G aerogel after drying and forming, and placing the integrated TPU-G aerogel in a vacuum drying oven for annealing to obtain the gradient-variable flexible three-dimensional piezoelectric framework; the process flow of the preparation process of the gradient-variable flexible three-dimensional piezoelectric framework is shown in fig. 2, and the micro-apertures of the bottom aerogel, the middle aerogel and the top aerogel present different sizes due to the change of the addition proportion of the graphene. A schematic of the microstructure of a gradient flexible three-dimensional piezoelectric skeleton is shown in fig. 3, in which G powder is embedded inside the skeleton. SEM pictures of the bottom, middle and top aerogels of the gradient flexible three-dimensional piezoelectric skeleton obtained in the embodiment are shown in FIG. 4, scales of the SEM pictures are 200 μm, 100 μm and 10 μm in sequence from left to right, and it can be seen from FIG. 4 that the three layers of aerogels have different pore diameter structures.
Thirdly, preparing the flexible aerogel with the gradient-changing structure
Firstly, adding 500mg of MXENE nano sheets into a beaker filled with 20mL of pure water to prepare MXENE conductive solution, suspending a gradient-variable flexible three-dimensional piezoelectric framework in the solution by utilizing a pressing block with proper weight, carrying out ultrasonic dipping for 1.5h at room temperature, overturning the piezoelectric framework by using a clean forceps, continuing carrying out ultrasonic dipping for 1.5h at room temperature, placing the dipped piezoelectric framework in a vacuum drying box, and drying for 1h at 50-60 ℃ to prepare the gradient-variable structure flexible aerogel; the schematic diagram of the ultrasonic dipping process is shown in fig. 5, and the schematic diagram of the microstructure of the obtained variable gradient structure flexible aerogel is shown in fig. 6, wherein MXENE is attached in the holes of the variable gradient flexible three-dimensional piezoelectric skeleton.
The fourth step of preparing an electrode layer
Fixing the gradient-structure-variable flexible aerogel on a copper metal sputtering target platform, conveying the copper metal sputtering target platform into a sputtering chamber sample platform, opening a vacuum system, and vacuumizing to 8 x 10 -4 After Pa, argon gas was introduced to maintain the pressure at 0.6Pa, and pre-sputtering was performed. And after 5min, setting the heating temperature of the sample stage to 200 ℃, opening the heating switch of the sample stage, sputtering copper metal after the temperature is stable, stopping sputtering after 30min, and taking out the sample after the temperature is cooled to room temperature to obtain the aerogel with one end coated with the copper film electrode. The other end is placed upwards, and the process flow is repeated.
Step five, preparing a G-TPU-MXENE flexible pressure sensor
Two electrodes are led out from the electrode layer by a copper wire and are connected with an electric signal measuring device, then PDMS films with the thickness of 12 microns are spin-coated at the two ends of the piezoelectric device at the rotating speed of 5000rpm, and after the PDMS films are solidified, the G-TPU-MXENE flexible pressure sensor which is packaged is obtained, and the specific structure refers to FIG. 7.
Fig. 8 is a graph of the rate of change of resistance of the G-TPU-MXENE flexible pressure sensor prepared in example 1 under different pressures, wherein a small graph is an enlarged graph of a dotted line frame portion, and it can be seen from fig. 8 that the G-TPU-MXENE flexible pressure sensor prepared in this example can realize gradient sensitive detection in a pressure range of 0 to 2000kpa, and the sensitivity (S) is 0.0142 at 500kpa or less and 0.0006 at 500kpa or more.
Example 2
In the embodiment, graphene (G) is used as a two-dimensional nanomaterial, PVA is used as a polymer matrix, and a silver nanowire is used as a conductive material to prepare a two-layer gradient-variable flexible aerogel, and based on the two-layer gradient-variable flexible aerogel, the manufacturing and molding of the flexible pressure sensor are completed by epoxy resin encapsulation, and the preparation steps are as follows:
first, preparing a solution of G-PVA mixed flexible aerogel collagen
Measuring 30mL of N, N-Dimethylformamide (DMF) solution into two equal parts in a measuring cylinder, pouring the two parts into two clean beakers, weighing two parts of PVA particles accounting for 1.5% (bottom stock solution) and 3% (top stock solution) of 15mL of DMF solution by balance, respectively adding the two parts into the beakers, placing the beakers into a magnetic stirring water bath kettle, setting the water bath temperature to be 45 ℃, putting in magnetons, stirring for 6 hours to fully dissolve the PVA particles, weighing G powder accounting for 1.5% of the PVA by balance, respectively pouring the G powder into the two beakers, and fully and uniformly stirring by a glass rod. And then placing the aerogel into a cell disruptor, and ultrasonically disrupting the aerogel for 1.5 hours by using an amplitude transformer with the diameter of 20mm under the parameter of 80% of output power density to respectively obtain uniform raw solutions at the bottom and the top of the gradient structure aerogel of which the G and the PVA are mixed, wherein the proportion of the G powder to the PVA in the raw solutions at the bottom and the top is unchanged.
Secondly, preparing a gradient-variable flexible three-dimensional piezoelectric framework
Placing a cuboid cavity mold 1 with the length of 8cm, the width of 1cm, the height of 6cm and the wall thickness of 0.1cm in a refrigerator for refrigeration, then pouring a bottom aerogel collagen solution mixed by G and PVA into the mold, then pouring sufficient liquid nitrogen into a big beaker, clamping the mold by using tweezers, placing the mold in the liquid nitrogen for instantaneous solidification, then placing the mold in an environment with the temperature of-20 ℃ to-30 ℃ for pre-freezing for more than 12 hours for molding, then placing the pre-frozen product into a vacuum freeze-drying machine, drying the pre-frozen product at the temperature of-50 ℃ to-75 ℃ for more than 72 hours to remove DMF solvent to form bottom PVA-G aerogel, taking out the mold, pouring a top aerogel collagen solution mixed by G and PVA into a low-temperature mold, repeating the steps, preparing the top PVA-G aerogel, taking out the integrated PVA-G aerogel after drying molding, and placing the integrated PVA-G aerogel in a vacuum drying oven for annealing to obtain the gradient-variable flexible three-dimensional piezoelectric framework.
Thirdly, preparing the flexible aerogel with the gradient-changing structure
Pouring the purchased silver nanowire solution (with the concentration of 15mg/mL) into a beaker for later use, suspending the gradient-structure three-dimensional piezoelectric framework in the solution by using a pressing block with proper weight, ultrasonically dipping for 1.5h at room temperature, overturning the piezoelectric framework by using clean tweezers, continuously ultrasonically dipping for 1.5h at room temperature, placing the dipped piezoelectric framework in a vacuum drying oven, and drying for 1h at 50-60 ℃ to obtain the gradient-structure-variable flexible aerogel.
The fourth step of preparing an electrode layer
Fixing the flexible aerogel with the variable gradient structure on a nickel metal sputtering target platform, conveying the flexible aerogel into a sample platform of a sputtering chamber, opening a vacuum system, and vacuumizing to 8 multiplied by 10 -4 After Pa, argon gas was introduced to maintain the pressure at 0.6Pa, and pre-sputtering was performed. And after 5min, setting the heating temperature of the sample stage to 200 ℃, opening a sample stage heating switch, performing nickel metal sputtering after the temperature is stable, stopping sputtering after 30min, and taking out the sample after the temperature is cooled to room temperature to obtain the aerogel layer with one end coated with the nickel film electrode. The other end is placed upwards, and the process flow is repeated.
Step five, preparing the G-PVA-AgNWS flexible pressure sensor
Two electrodes are led out of the electrode layer by a copper wire and are connected with an electric signal measuring device, then epoxy resin films with the thickness of 12 microns are spin-coated at the two ends of the piezoelectric device at the rotating speed of 5000rpm, and after the epoxy resin films are solidified, the packaged G-PVA-AgNWS flexible pressure sensor is obtained, wherein the specific structure is shown in figure 7.
Fig. 9 is a graph of the resistance change rate of the G-PVA-AgNWS flexible pressure sensor prepared in example 2 under different pressures, wherein a small graph is an enlarged graph of a dashed line frame portion, and it can be seen from fig. 9 that the G-PVA-AgNWS flexible pressure sensor prepared in this example can realize gradient sensitive detection within a pressure range of 0-2000 kpa, the sensitivity (S) is 0.0138 when below 500kpa, and the sensitivity is 0.00058 when above 500 kpa.
Example 3
In this embodiment, a three-layer gradient-variable flexible aerogel is prepared by using Reduced Graphene Oxide (RGO) as a two-dimensional nanomaterial, a TPU-PVA composite material as a polymer matrix, and MXENE as a conductive material, and based on this, the flexible pressure sensor is manufactured and molded by PDMS encapsulation, and the preparation steps are as follows:
first, preparing a flexible aerogel collagen solution of RGO mixed with TPU-PVA
Measuring 45mL of N, N-Dimethylformamide (DMF) solution into three equal parts, pouring the three parts into three clean beakers, weighing 1 mass percent of PVA particles and 1 mass percent of TPU particles in 15mL of N, N-Dimethylformamide (DMF) solution by using a balance, respectively adding the three parts into the beakers, placing the beakers into a magnetic stirring water bath kettle, setting the water bath temperature to be 45 ℃, putting in a magneton, stirring for 6 hours to fully dissolve the TPU and PVA particles, weighing 3 mass percent (bottom stock solution), 5 mass percent (middle stock solution) and 8 mass percent (top stock solution) of RGO powder in the total mass of the TPU and the PVA by using a balance, respectively pouring the three beakers into the three beakers, and fully and uniformly stirring by using a glass rod. And then placing the mixture into a cell crusher, and ultrasonically crushing the mixture for 1.5h by using an amplitude transformer with the diameter of 20mm under the parameter of 80% of output power density to respectively obtain uniform RGO and TPU-PVA mixed gradient structure aerogel bottom, middle and top stock solutions.
Secondly, preparing a gradient-variable flexible three-dimensional piezoelectric framework
Placing a cuboid cavity mold 1 with the length of 8cm, the width of 1cm, the height of 6cm and the wall thickness of 0.1cm in a refrigerator for refrigeration, then pouring a proper amount of RGO and TPU-PVA mixed bottom aerogel liquid into the mold, then pouring sufficient liquid nitrogen into a large beaker, clamping the mold by using tweezers, placing the mold in the liquid nitrogen for instant solidification, then placing the mold in an environment with the temperature of-20 ℃ to-30 ℃ for pre-freezing for more than 12 hours for formation, then placing the pre-frozen product into a vacuum freeze-drying machine, drying the pre-frozen product for more than 72 hours at the temperature of-50 ℃ to-75 ℃ to remove a DMF solvent to form TPU-PVA-RGO aerogel, taking out the mold, pouring G and TPU-PVA mixed middle aerogel liquid into the low-temperature mold, placing the mold in a liquid nitrogen environment for instant freezing, then placing the pre-frozen environment with the temperature of-20 ℃ to-30 ℃ for formation for more than 12 hours, and then putting the pre-frozen product into a vacuum freeze dryer, drying at the temperature of-50 to-75 ℃ for more than 72 hours to remove the DMF solvent to form a middle TPU-PVA-RGO aerogel, taking out the mold again, pouring the top aerogel liquid mixed by G and TPU-PVA into a low-temperature mold, repeating the steps to prepare the top TPU-PVA-RGO aerogel, taking out the integrated TPU-PVA-RGO aerogel after drying and forming, and putting the integrated TPU-PVA-RGO aerogel into a vacuum drying box for annealing to obtain the gradient-variable flexible three-dimensional piezoelectric framework.
Thirdly, preparing the flexible aerogel with the gradient-changing structure
Firstly, adding 500mg of MXENE nanosheets into a beaker filled with 20mL of pure water to prepare MXENE conductive solution, suspending the gradient-structure three-dimensional piezoelectric framework in the solution by utilizing a pressing block with proper weight, ultrasonically dipping for 1.5h at room temperature, overturning the piezoelectric framework by using a clean forceps, continuously ultrasonically dipping for 1.5h at room temperature, placing the dipped piezoelectric framework in a vacuum drying box, and drying for 1h at 50-60 ℃ to prepare the gradient-structure flexible aerogel.
The fourth step of preparing an electrode layer
Fixing the flexible aerogel on a copper metal sputtering target platform, conveying the flexible aerogel into a sample platform of a sputtering chamber, opening a vacuum system, and vacuumizing to 8 x 10 -4 After Pa, argon gas was introduced to maintain the pressure at 0.6Pa, and pre-sputtering was performed. And after 5min, setting the heating temperature of the sample stage to 200 ℃, opening the heating switch of the sample stage, sputtering copper metal after the temperature is stable, stopping sputtering after 30min, and taking out the sample after the temperature is cooled to room temperature to obtain the aerogel with one end coated with the copper film electrode. The other end is placed upwards, and the process flow is repeated.
Fifthly, preparing the RGO-TPU/PVA-MXENE flexible pressure sensor
And leading out two electrodes from the electrode layer by using a copper wire, connecting the two electrodes with an electric signal measuring device, spin-coating a PDMS film with the thickness of 12 mu m at the rotating speed of 5000rpm at the two ends of the piezoelectric device, and curing to obtain the packaged RGO-TPU/PVA-MXENE flexible pressure sensor.
FIG. 10 is a graph of the rate of change of resistance of the RGO-TPU/PVA-MXENE flexible pressure sensor prepared in example 3 under different pressures, wherein a small graph is an enlarged graph of a dashed line frame part, and it can be seen from FIG. 10 that the RGO-TPU/PVA-MXENE flexible pressure sensor prepared in this example can realize gradient sensitive detection in a pressure range of 0-2000 kpa, the sensitivity (S) is 0.0135 at a pressure of below 500kpa, and the sensitivity is 0.0006 at a pressure of above 500 kpa.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (10)

1. The preparation method of the flexible aerogel with the variable gradient structure is characterized by comprising the following steps:
(1) pouring the aerogel collagen liquid into a mould to be frozen and then freeze-drying to obtain a polymer-nano material aerogel layer; the components of the aerogel collagen liquid comprise a polymer matrix, a two-dimensional nano material and an organic solvent;
(2) repeating the step (1) for more than or equal to 1 time to obtain the multilayer integrated polymer-nano material aerogel; in the multilayer integrated polymer-nano material aerogel, the content of polymer matrixes and/or two-dimensional nano materials in aerogel liquid adopted for preparing each layer of aerogel is different;
(3) carrying out first annealing on the multilayer integrated polymer-nano material aerogel to obtain a gradient-variable flexible three-dimensional piezoelectric framework;
(4) and ultrasonically dipping the gradient-variable flexible three-dimensional piezoelectric framework in a two-dimensional conductive material solution, and then carrying out secondary annealing and drying to obtain the gradient-variable structure flexible aerogel.
2. The preparation method of claim 1, wherein the polymer matrix comprises one or more of polyurethane, polyvinyl alcohol and polydimethylsiloxane; the two-dimensional nano material comprises one or two of graphene and reduced graphene oxide; the organic solvent includes one or both of dioxane and N, N-dimethylformamide.
3. The preparation method according to claim 1 or 2, wherein the aerogel collagen liquid used in the steps (1) to (2) has a mass ratio of the polymer matrix to the organic solvent of (1-5) to (50-100) and a mass ratio of the polymer matrix to the two-dimensional nanomaterial of (100-200) to (1-10).
4. The method according to claim 1 or 2, wherein the mass fraction of the polymer matrix or the two-dimensional nanomaterial in the aerogel liquid used in each layer is sequentially increased or decreased from bottom to top.
5. The method according to claim 1 or 2, wherein the aerogel liquid used for preparing each layer of aerogel is changed from bottom to top in such a way that the polymer matrix and the two-dimensional nanomaterial in the aerogel liquid are changed from the following three types:
the first method is as follows: the content of the polymer matrix in the aerogel collagen liquid used in each layer is the same, and the content of the two-dimensional nano materials is increased or decreased in sequence;
the second method comprises the following steps: the content of the two-dimensional nano material in the aerogel collagen liquid used in each layer is the same, and the content of the polymer matrix is increased or decreased in sequence;
the third method comprises the following steps: the polymer matrix and the two-dimensional nano material in the aerogel collagen liquid used in each layer have the same proportion, and the content of the polymer matrix and the content of the two-dimensional nano material are sequentially increased or decreased simultaneously.
6. The preparation method according to claim 1, wherein the freezing comprises liquid nitrogen freezing and pre-freezing in sequence, and the liquid nitrogen freezing is specifically as follows: placing the mould filled with the aerogel collagen liquid in liquid nitrogen to enable the aerogel original liquid to be instantly frozen; the pre-freezing temperature is-20 to-30 ℃, and the time is more than 12 hours;
the temperature of the freeze drying is-50 to-75 ℃, and the time is more than 60 hours.
7. The preparation method according to claim 1, wherein the two-dimensional conductive material comprises one or more of MXENE, graphene, reduced graphene oxide and silver nanowires.
8. The gradient-structure-variable flexible aerogel prepared by the preparation method of any one of claims 1 to 8.
9. A flexible pressure sensor comprises a lower packaging layer, a lower electrode layer, the variable gradient structure flexible aerogel of claim 8, an upper electrode layer and an upper packaging layer which are sequentially stacked; the lower electrode layer and the upper electrode layer are connected with a lead; the lead is connected with an electric signal measuring device.
10. A method of making a flexible pressure sensor according to claim 9, comprising the steps of:
preparing a lower electrode layer and an upper electrode layer on the surfaces of two sides of the flexible aerogel with the variable gradient structure by adopting an evaporation or sputtering method;
and connecting leads on the lower electrode layer and the upper electrode layer, connecting the leads with an electric signal measuring device, and then preparing a lower packaging layer and an upper packaging layer on the surfaces of the lower electrode layer and the upper electrode layer by adopting a spin coating and curing method to obtain the flexible pressure sensor.
CN202210651669.1A 2022-06-09 2022-06-09 Variable-gradient structure flexible aerogel, preparation method thereof and flexible pressure sensor Active CN115058049B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202210651669.1A CN115058049B (en) 2022-06-09 2022-06-09 Variable-gradient structure flexible aerogel, preparation method thereof and flexible pressure sensor

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202210651669.1A CN115058049B (en) 2022-06-09 2022-06-09 Variable-gradient structure flexible aerogel, preparation method thereof and flexible pressure sensor

Publications (2)

Publication Number Publication Date
CN115058049A true CN115058049A (en) 2022-09-16
CN115058049B CN115058049B (en) 2023-05-05

Family

ID=83200147

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202210651669.1A Active CN115058049B (en) 2022-06-09 2022-06-09 Variable-gradient structure flexible aerogel, preparation method thereof and flexible pressure sensor

Country Status (1)

Country Link
CN (1) CN115058049B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117030079A (en) * 2023-10-09 2023-11-10 之江实验室 Wide-range flexible pressure sensor and preparation method thereof

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130004761A1 (en) * 2011-06-28 2013-01-03 Lawrence Livermore National Security, Llc Methods of electrophoretic deposition for functionally graded porous nanostructures and systems thereof
US20140287641A1 (en) * 2013-03-15 2014-09-25 Aerogel Technologies, Llc Layered aerogel composites, related aerogel materials, and methods of manufacture
US20160243525A1 (en) * 2016-05-02 2016-08-25 LiSo Plastics, L.L.C. Multilayer Polymeric Membrane and Process
CN109097420A (en) * 2018-08-06 2018-12-28 华东交通大学 Graphene/bacterial cellulose composite material and preparation method with gradient-structure
CN109701494A (en) * 2018-12-28 2019-05-03 青岛海尔股份有限公司 Aerogel composite and preparation method thereof
CN109734950A (en) * 2018-12-28 2019-05-10 青岛海尔股份有限公司 Aerogel composite and preparation method thereof
CN112225942A (en) * 2020-10-13 2021-01-15 中南大学 Preparation method of strain-temperature dual-response flexible electronic sensor composite material, electronic sensor obtained by preparation method and composite material
CN112521716A (en) * 2020-12-15 2021-03-19 云南大学 Graphene aerogel-polyimide composite membrane material and preparation method thereof
CN113337000A (en) * 2021-05-24 2021-09-03 西安交通大学 Anisotropic heat conduction flexible piezoelectric sensor and preparation method thereof

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130004761A1 (en) * 2011-06-28 2013-01-03 Lawrence Livermore National Security, Llc Methods of electrophoretic deposition for functionally graded porous nanostructures and systems thereof
US20140287641A1 (en) * 2013-03-15 2014-09-25 Aerogel Technologies, Llc Layered aerogel composites, related aerogel materials, and methods of manufacture
US20160243525A1 (en) * 2016-05-02 2016-08-25 LiSo Plastics, L.L.C. Multilayer Polymeric Membrane and Process
CN109097420A (en) * 2018-08-06 2018-12-28 华东交通大学 Graphene/bacterial cellulose composite material and preparation method with gradient-structure
CN109701494A (en) * 2018-12-28 2019-05-03 青岛海尔股份有限公司 Aerogel composite and preparation method thereof
CN109734950A (en) * 2018-12-28 2019-05-10 青岛海尔股份有限公司 Aerogel composite and preparation method thereof
CN112225942A (en) * 2020-10-13 2021-01-15 中南大学 Preparation method of strain-temperature dual-response flexible electronic sensor composite material, electronic sensor obtained by preparation method and composite material
CN112521716A (en) * 2020-12-15 2021-03-19 云南大学 Graphene aerogel-polyimide composite membrane material and preparation method thereof
CN113337000A (en) * 2021-05-24 2021-09-03 西安交通大学 Anisotropic heat conduction flexible piezoelectric sensor and preparation method thereof

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
武志刚;高建峰;: "溶胶-凝胶法制备纳米材料的研究进展" *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117030079A (en) * 2023-10-09 2023-11-10 之江实验室 Wide-range flexible pressure sensor and preparation method thereof
CN117030079B (en) * 2023-10-09 2024-02-23 之江实验室 Wide-range flexible pressure sensor and preparation method thereof

Also Published As

Publication number Publication date
CN115058049B (en) 2023-05-05

Similar Documents

Publication Publication Date Title
Ding et al. Recent advances in flexible and wearable pressure sensors based on piezoresistive 3D monolithic conductive sponges
CN108318162B (en) A kind of flexible sensor and preparation method thereof
Ding et al. Flexible and compressible PEDOT: PSS@ melamine conductive sponge prepared via one-step dip coating as piezoresistive pressure sensor for human motion detection
Peng et al. Multimodal capacitive and piezoresistive sensor for simultaneous measurement of multiple forces
Wu et al. Channel crack-designed gold@ PU sponge for highly elastic piezoresistive sensor with excellent detectability
Huang et al. Three-dimensional light-weight piezoresistive sensors based on conductive polyurethane sponges coated with hybrid CNT/CB nanoparticles
Xia et al. Embedding variable micro-capacitors in polydimethylsiloxane for enhancing output power of triboelectric nanogenerator
CN106908176B (en) Multi-phase dielectric layer capacitive pressure sensor with micro-structure and manufacturing method thereof
Wu et al. A new approach for an ultrasensitive tactile sensor covering an ultrawide pressure range based on the hierarchical pressure-peak effect
Tannarana et al. 2D-SnSe2 nanosheet functionalized piezo-resistive flexible sensor for pressure and human breath monitoring
US20190228918A1 (en) Sensor and supercapacitor based on graphene polypyrrole 3d porous structure, and integrated device including the same
CN110108375B (en) MXene material-based electronic skin and preparation method thereof
CN111504520B (en) Integrated flexible stretchable touch sensor based on super-capacitor sensing principle
CN106461473A (en) Surface area-based pressure sensing
CN108225620B (en) Flexible touch sensor with multilayer structure and manufacturing method thereof
CN112816111B (en) Flexible touch sensor and manufacturing method thereof
CN115058049B (en) Variable-gradient structure flexible aerogel, preparation method thereof and flexible pressure sensor
Xue et al. Wearable and visual pressure sensors based on Zn 2 GeO 4@ polypyrrole nanowire aerogels
CN111504527B (en) Sea urchin-shaped oxide-based composite membrane bionic pressure sensor and preparation method thereof
CN110987246A (en) Flexible sensor and preparation and use methods thereof
CN113337000A (en) Anisotropic heat conduction flexible piezoelectric sensor and preparation method thereof
Xin et al. Transient electrically driven stiffness-changing materials from liquid metal polymer composites
CN114608716A (en) Flexible temperature and pressure bimodal sensor and preparation and test method thereof
Ge et al. Flexible pressure sensor based on a thermally induced wrinkled graphene sandwich structure
CN113667178B (en) Flexible degradable pressure sensing material with micro-channel structure and preparation method thereof

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant