CN115435912A - Flexible temperature sensor and preparation method thereof - Google Patents
Flexible temperature sensor and preparation method thereof Download PDFInfo
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- CN115435912A CN115435912A CN202210989445.1A CN202210989445A CN115435912A CN 115435912 A CN115435912 A CN 115435912A CN 202210989445 A CN202210989445 A CN 202210989445A CN 115435912 A CN115435912 A CN 115435912A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D1/00—Processes for applying liquids or other fluent materials
- B05D1/002—Processes for applying liquids or other fluent materials the substrate being rotated
- B05D1/005—Spin coating
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/05—Metallic powder characterised by the size or surface area of the particles
- B22F1/054—Nanosized particles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/17—Metallic particles coated with metal
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Abstract
The invention relates to the technical field of flexible sensing, in particular to a flexible temperature sensor and a preparation method thereof. The invention provides a flexible temperature sensor comprising: a base film; a sensing material electrode embedded in the base film; and an encapsulation layer; the sensing electrode material is silver gallium alloy. The sensing electrode of the flexible temperature sensor provided by the invention is almost completely embedded in the substrate film, can be better tightly combined with the substrate, and improves the mechanical performance and the measurement stability of the flexible sensor. Meanwhile, the embedded substrate type flexible temperature sensor is simple in structure and can be prepared in a large area at low cost.
Description
Technical Field
The invention relates to the technical field of flexible sensing, in particular to a flexible temperature sensor and a preparation method thereof.
Background
In recent years, with the increasing living standard of people, the requirements of people on sensors are increasing. The traditional rigid sensor is difficult to meet the current increasingly diversified application scenes due to the defects of large volume, incapability of bending and the like. The flexible sensor has good bending performance, can be tightly attached to an irregular surface, is light and thin in structure, and enhances the wearing comfort and universality of the sensor. Due to the characteristics, the flexible sensor has wide application prospects in the aspects of wearable electronics, health care, agricultural monitoring and the like.
The key to the flexible sensor technology is the sensing material and the manufacturing process. At present, common flexible sensing materials comprise liquid metal, graphene oxide, silver nanowires, copper nanowires and the like, but still have the defects of high cost, poor stability and the like; the key fabrication process technologies mainly include patterning fabrication technology, transfer printing technology, etc., however, the current fabrication process still has the disadvantages of high cost, high sintering temperature, inability of large-area fabrication, poor mechanical properties, etc.
Disclosure of Invention
In order to solve the technical problems, the invention provides a flexible temperature sensor and a preparation method thereof.
In a first aspect, the present invention provides a flexible temperature sensor comprising:
a base film;
a sensing material electrode embedded in the base film;
and an encapsulation layer;
the sensing electrode material is silver gallium alloy.
The invention provides a flexible temperature sensor based on liquid metal gallium cladding. The sensing electrode of the flexible temperature sensor provided by the invention is almost completely embedded in the substrate film, can be better tightly combined with the substrate, and improves the mechanical performance and the measurement stability of the flexible sensor. The embedded substrate type flexible temperature sensor has a simple structure, and can be conveniently prepared in a large area with low cost.
Preferably, the sensing electrode material is a liquid metal gallium-coated silver electrode, and the thickness of the sensing electrode material is 5-10 um, preferably 7-10 um; preferably, the base film is a polyimide film; the thickness of the base film is not more than 40um, preferably 23 to 40um, and more preferably 25 to 40um.
According to the invention, the base film adopts a polyimide film as the base of the flexible sensor, the flexible sensing material adopts gallium-silver alloy formed by liquid metal gallium with high surface activity and coating silver particles, and the flexible sensing material is better embedded into the ultrathin polyimide base film by combining transfer printing modes such as silk-screen printing and the like, so that the problems of high sintering temperature, poor stability, easiness in damage, high preparation cost, incapability of large-area preparation and the like of the flexible sensor can be better solved. Particularly, the liquid metal gallium coated silver electrode with a specific thickness is combined with the polyimide film with a specific thickness, so that the flexible sensor is combined more tightly, and meanwhile, the mechanical performance and the measurement stability of the flexible sensor can be better improved, and the cost is reduced.
Further preferably, the sensing electrode material is embedded in the base film, and a (upper) surface of the sensing electrode material is preferably flush with a (upper) surface of the base film, and preferably the (upper) surface of the sensing electrode material is exposed outside the base film. Further preferably, a transparent encapsulating layer is used for encapsulating the (upper) surface part of the sensing electrode material (exposed out of the base film); preferably, the sensing electrode material is embedded in the base film and interdiffused. The invention adopts the optimized sensor structure, thereby further improving the performance.
Further preferably, the upper surface of the sensing electrode material and/or the upper surface of the substrate film are/is encapsulated by the encapsulation layer, the encapsulation layer is preferably a transparent encapsulation layer, and the material of the transparent encapsulation layer is selected from one or more of PDMS, ecoflex00-30 and Casterp-2577.
Further preferably, the sensor further comprises a lead and conductive silver adhesive, wherein the lead is connected to the sensing electrode material through the conductive silver adhesive, and the conductive silver adhesive and/or the lead are/is preferably packaged by adopting a transparent packaging layer.
According to the invention, the flexible temperature sensor can be better used in different application scenes by optimizing and screening the sensor material and the structure of the flexible temperature sensor.
In a second aspect, the present invention provides a method for preparing a (embedded substrate type) flexible temperature sensor, comprising:
1) Mixing the nano silver powder, the liquid metal gallium and the alkaline solution, introducing current, and centrifuging to obtain nano silver gallium particles with a silver gallium alloy shell structure;
2) Mixing the nano silver-gallium particles with a dispersing agent, and performing ultrasonic dispersion treatment to obtain liquid metal gallium-coated silver particle ink;
3) Printing the silver particle ink coated with the liquid metal gallium on a printing plate through screen printing, after the dispersing agent is volatilized, spin-coating a polyimide solution, and after solidification, putting the polyimide solution into water to obtain a base film precursor embedded with a silver-gallium alloy;
4) Carrying out microwave heating sintering treatment on the base film precursor embedded with the silver-gallium alloy to obtain a base film embedded with the silver-gallium alloy;
5) And welding a lead on the circular electrode of the sensing electrode material subjected to microwave heating and sintering, and then packaging. The preparation process of the flexible temperature sensor provided by the invention can be used for preparing the flexible temperature sensor with excellent mechanical property and stability, is convenient to prepare, and can be used for realizing large-area preparation with low cost.
Further preferably, in the step 1), a current of 1-2A is introduced for 5-10 min through a graphite electrode; the centrifugation adopts differential centrifugation, and the rotating speed is 10000-20000 rpm; preferably, the particle size of the nano silver powder is 20-50 nm; the alkaline solution is selected from one or more of sodium hydroxide solution, potassium hydroxide solution and calcium hydroxide solution, preferably the alkaline solution is strong alkaline solution, and the concentration of the alkaline solution is preferably 1-5 mol/L; the mass ratio of the nano silver powder to the liquid metal gallium is preferably 2:1 to 1:9.
further preferably, in the step 2), the power of the ultrasonic dispersion treatment is 150-200W, and the ultrasonic dispersion treatment preferably adopts circulating ultrasound for 10-20 times; preferably, the ultrasonic switch is switched on for 2s and switched off for 2s for 4min each time, the total ultrasonic time is 20-40 min, and water bath cooling is preferably carried out between each cycle; preferably, the dispersing agent is selected from one or more of a PVP aqueous solution with the mass fraction of 10-15%, a PVP n-hexanol solution with the mass fraction of 3-5% and a PVP n-hexanol solution with the mass fraction of 3-5%, and the mass ratio of the nano silver-gallium particles to the dispersing agent is 2. According to the invention, the silver particle ink coated with the liquid metal gallium, which is uniform in dispersion and better in stability, can be obtained by mixing the nanoparticles with the silver gallium shell structure and the dispersing agent in a specific ratio and carrying out the ultrasonic dispersion treatment.
Further preferably, in the step 3), the screen size of the screen printing is preferably 200 to 500 meshes; the spin coating is set to have the pre-rotation speed of 300-500 rpm and rotate for 15-20 s, and then the rotation speed is increased to 1500-2200 rpm and rotates for 15-20 s; the solidification is carried out under the condition of vacuum heating, the vacuum degree is preferably-0.85 to-0.95 MPa, the temperature is preferably 150 to 220 ℃, and the solidification time is preferably 2 to 3 hours. According to the invention, by optimizing the modes and conditions of screen printing, spin coating and vacuum heating curing, the sensing electrode is better embedded in the substrate film, so that the close combination of the sensing electrode and the substrate is further improved, the stability of the substrate film embedded with the silver-gallium alloy is improved, and the comprehensive performance of the flexible sensor is better.
More preferably, in the step 4), the microwave heating sintering treatment is performed for 1s to 3s at a sintering temperature of 70 ℃ to 90 ℃. According to the invention, the specific microwave heating sintering method and conditions are adopted, so that the base film embedded with the liquid metal gallium-coated silver nanoparticle electrode can be solidified more quickly, and the mechanical property of the manufactured sensor is further improved.
Further preferably, in step 5), the encapsulated material is selected from one or more of PDMS, ecoflex00-30, casterp-2577; and welding the lead by adopting conductive silver adhesive. The transparent packaging layer and the conductive silver adhesive are adopted, so that the influence of the environment on the measurement precision of the flexible temperature and humidity sensor is improved.
The invention has the beneficial effects that: the embedded substrate type flexible temperature sensor provided by the invention adopts the silver-gallium alloy as the sensing electrode, has the advantages of good stability, high surface activity and the like, can effectively reduce the energy required by ink excitation and is better tightly combined with the substrate material; the sensing electrode is almost completely embedded into the base film, and the upper surface of the sensing electrode is almost flush with the surface of the base film, so that the mechanical property and the measurement stability of the flexible temperature sensor are greatly enhanced; the microwave heating sintering method is adopted to quickly solidify the basement membrane embedded with the liquid metal gallium-coated silver nanoparticle electrode and improve the performance. The preparation method provided by the invention has the advantages of simple process, convenience in preparation and capability of realizing low-cost large-area preparation.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments or the prior art descriptions will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic structural diagram of an embedded substrate type ultrathin flexible temperature sensor provided by the invention;
FIG. 2 isbase:Sub>A cross-sectional view at A-A of the embedded substrate ultra-thin flexible temperature sensor provided by the present invention;
fig. 3 is a schematic diagram of a substrate film model with embedded ag electrode provided by the present invention;
FIG. 4 is a structural dimension diagram of the embedded ultra-thin flexible temperature sensor provided by the invention;
FIG. 5 is a microstructure diagram of the conductive Ag-Ga ink printed on the glass substrate in example 1 of the present invention in three states of (a), (b) after being spin-coated with polyimide and cured and separated, and (c) after being sintered by microwave heating;
FIG. 6 shows the results of 15 temperature tests performed in an incubator by the flexible temperature and humidity sensor prepared in example 1, wherein FIG. a shows the corresponding resistance of the test performed for 15 consecutive cycles, and FIG. b shows the response of the resistance at different temperatures
Fig. 7 is a curve fit of 15 temperature tests performed in an incubator by the flexible temperature and humidity sensor prepared in example 1.
Fig. 8 is a resistance change of the flexible temperature sensor prepared in example 1 in 15000 bending experiments.
Reference numerals:
1. a silver gallium electrode; 2. a base film; 3. a transparent encapsulation layer; 4. conductive silver paste; 5. a lead wire; 6. an embedded electrode film structure.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and the following embodiments are used for illustrating the present invention and are not intended to limit the scope of the present invention. The examples do not show the specific techniques or conditions, according to the technical or conditions described in the literature in the field, or according to the product specifications. The reagents or instruments used are conventional products available from regular distributors, not indicated by the manufacturer.
The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
In the description of the present invention, unless otherwise specified, the terms "upper", "lower", "inside", "outside", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the system or element referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention.
As shown in fig. 1 and 2, an embodiment of the present invention provides an embedded substrate type flexible temperature sensor. The flexible embedded substrate type flexible temperature sensor comprises a silver gallium electrode 1, a basement membrane 2 (PI), a transparent packaging layer 3, conductive silver adhesive 4 and a lead 5. The embedded substrate type flexible temperature sensor is an embedded electrode thin film structure 6, a silver gallium electrode 1 is completely embedded in a base film 2 to form the embedded electrode thin film structure, 4 leads 5 are connected to the silver gallium electrode 1 through conductive silver adhesive 4, and a transparent packaging layer 3 is packaged on the silver gallium electrode 1, the base film 2, the conductive silver adhesive 4 and the leads 5. As shown in fig. 3, the ag-ga electrode 1 is embedded in the base film 2 in the whole structure, and the polyimide solution diffuses and permeates with the nano ag-ga particles in the curing process, so that the formed ag-ga electrode is more tightly combined with the base film 2, and the mechanical property and the measurement stability of the flexible sensor are greatly improved.
The embodiment of the invention also provides a preparation method of the embedded substrate type flexible temperature sensor, which comprises the following steps:
step S11: putting the nano silver powder and the liquid gallium into a strong alkaline solution, introducing 1A-2A current through a graphite electrode for 5 min-10 min, and then obtaining silver gallium nanoparticles through differential centrifugation;
step S12: adding silver gallium nano particles into a dispersing agent, and performing ultrasonic dispersion until no obvious granular sensation exists to obtain conductive silver gallium ink;
step S13: printing conductive silver-gallium ink on a printing substrate through screen printing, after a dispersing agent is volatilized, spin-coating a layer of polyimide solution on the surface of the printing substrate, curing for 2-3 h under a vacuum heating condition, and then putting the polyimide solution into deionized water to obtain a base film precursor embedded with silver-gallium alloy;
step S14: placing the base film precursor embedded with the silver-gallium alloy into a microwave chamber to perform microwave heating sintering treatment, and performing microwave induction to obtain shell-shell sintering through the silver-gallium shell heat effect of particles; obtaining a basement membrane embedded with a silver-gallium alloy electrode;
step S15: and welding a conducting wire used for measurement on a circular electrode of a sensing electrode in a base film embedded with a silver-gallium alloy electrode after sintering is finished, and packaging the upper surface after welding is finished.
As shown in fig. 4, in the embodiment of the present invention, the diameter of the ag-ga electrode 1 is 0.3mm, the ag-ga electrode 1 is serpentine, two ends of the ag-ga electrode 1 are connected to a lead through a conductive silver paste 3, the diameter of the conductive silver paste 3 is 3mm, and the overall structural dimensions of the ag-ga electrode 1 and the conductive silver paste 3 are as follows: the length is 17.4mm, and the width is 10.84mm.
In the embodiment of the invention, the main materials are as follows: the base film is made of polyimide solution, the transparent packaging layer is made of PDMS solution, and the sensing electrode is made of silver-gallium alloy. The preparation and test conditions in the embodiment without special description are normal temperature and normal pressure.
The above-mentioned embedded substrate type flexible temperature sensor will be further described in detail with reference to the manufacturing process of the embedded substrate type flexible temperature sensor of each embodiment.
Example 1
(1) And putting the nano silver powder (with the particle size of 20 nm) and the liquid gallium (the mass ratio of the nano silver powder to the liquid gallium is 1.
(2) Weighing 127.5g of deionized water in a 200ml conical flask, heating and stirring at 50 ℃, adding 22.5g of PVP particles in total weight for a plurality of times in small amount, and stirring until the solution is colorless and transparent to form a PVP water solution with the mass fraction of 15%.
(3) And taking 10ml of disposable centrifuge tube, weighing 5g of the prepared silver-gallium nanoparticles and 2.5g of the prepared dispersant solution, respectively adding into the centrifuge tube, and stirring with a glass rod for primary dispersion to enable the dispersant to gradually permeate into the bottom of the centrifuge tube.
(4) Mechanically dispersing by using an ultrasonic crusher, selecting a 3mm ultrasonic drill bit, setting the parameter to be 150W power, setting an ultrasonic switch to be 2s on and 2s off, circulating for 4min for one time, circulating for 15 times in total, and controlling the total ultrasonic time to be 30min; after each cycle, the centrifuge tube was cooled in a water bath using cold water.
(5) A serpentine pattern having the size shown in FIG. 4 was printed on a glass plate using a 300 mesh screen, and a layer of polyimide solution was spin-coated on the glass using a spin coater set to a pre-spin speed of 500rpm for 20 seconds, then raised to 2200rpm for 20 seconds.
(6) After the spin coating is finished, the substrate is placed into a vacuum drying oven with the vacuum degree of-0.88 MPa and the temperature of 200 ℃ for curing for 3 hours, and then is placed into deionized water to form a substrate film embedded with a silver-gallium alloy electrode. And then placing the basement membrane embedded with the silver-gallium alloy electrode into a microwave chamber to be heated and sintered for 2s, wherein the sintering temperature is 80 ℃.
(7) And after the treatment is finished, welding two enamelled wires with the diameter of 0.1mm on the two circular electrodes of the snake-shaped electrode respectively by using conductive silver colloid for measuring the resistance change of the sensor caused by the temperature change.
(8) And finally, covering a layer of PDMS solution on the surface by using an inclined flow leveling method to prepare a transparent packaging layer, further protecting the embedded substrate type flexible temperature sensor and reducing the influence of the environment on the measurement result. FIG. 5 is a microstructure diagram of the embodiment, in which the average thickness of the sensing electrode material after microwave sintering is about 7um; the substrate film had an average thickness of about 25um over the whole.
Example 2
(1) And putting the nano silver powder (with the particle size of 20 nm) and the liquid gallium (the mass ratio of the nano silver powder to the liquid gallium is 1.
(2) 142.5g of hexanol solution were weighed into a 200ml Erlenmeyer flask, heated and stirred at 90 ℃ and a small amount of PVP particles with a total weight of 7.5g were added several times, and the solution was stirred until colorless and transparent.
(3) And taking 10ml of disposable centrifuge tube, weighing 5g of the prepared silver-gallium nanoparticles and 2.5g of the prepared dispersant solution, respectively adding into the centrifuge tube, and stirring with a glass rod for primary dispersion to enable the dispersant to gradually permeate into the bottom of the centrifuge tube.
(4) Mechanically dispersing by using an ultrasonic crusher, selecting a 3mm ultrasonic drill bit, setting parameters to be 200W power, setting an ultrasonic switch to be 2s on and 2s off, circulating for 4min for one time, and circulating for 10 times in total, wherein the total ultrasonic time is 20min; after each cycle, the centrifuge tube was cooled in a water bath using cold water.
(5) A serpentine pattern having the dimensions shown in FIG. 4 was printed on a glass plate using a 300 mesh screen, and a layer of polyimide solution was spun onto the glass using a spin coater set to a pre-spin speed of 500rpm for 20 seconds, then ramped up to 2200rpm for 20 seconds.
(6) After the spin coating is finished, the substrate is placed into a vacuum drying oven with the vacuum degree of-0.88 MPa and the temperature of 200 ℃ for solidification for 3 hours, and then the substrate is placed into deionized water to form a substrate film embedded with a silver-gallium alloy electrode. And then placing the basement membrane embedded with the silver-gallium alloy electrode into a microwave chamber to be heated and sintered for 2s, wherein the sintering temperature is 80 ℃.
(7) And after the treatment is finished, welding two enamelled wires with the diameter of 0.1mm on the two circular electrodes of the snake-shaped electrode respectively by using conductive silver colloid for measuring the resistance change of the sensor caused by the temperature change.
(8) And finally, covering a layer of Ecoflex00-30 solution on the surface by using an inclined flow method to prepare a transparent packaging layer, so as to further protect the embedded substrate type flexible temperature sensor and reduce the influence of the environment on the measurement result.
Comparative example
(1) And putting the nano silver powder (with the particle size of 20 nm) and the liquid gallium (the mass ratio of the nano silver powder to the liquid gallium is 1.
(2) Weighing 127.5g of deionized water in a 200ml conical flask, heating and stirring at 50 ℃, adding 22.5g of PVP particles in total weight for a plurality of times in small amount, and stirring until the solution is colorless and transparent to form a PVP water solution with the mass fraction of 15%.
(3) And taking 10ml of disposable centrifuge tube, weighing 5g of the prepared silver-gallium nanoparticles and 2.5g of the prepared dispersant solution, respectively adding into the centrifuge tube, and stirring with a glass rod for primary dispersion to enable the dispersant to gradually permeate into the bottom of the centrifuge tube.
(4) Mechanically dispersing by using an ultrasonic crusher, selecting a 3mm ultrasonic drill bit, setting the parameter to be 150W power, setting an ultrasonic switch to be 2s on and 2s off, circulating for 4min for one time, circulating for 15 times in total, and controlling the total ultrasonic time to be 30min; after each cycle, the centrifuge tube was cooled in a water bath using cold water.
(5) Spin coating a layer of polyimide solution on the glass by a spin coater, setting the parameters of the spin coater to be 500rpm, rotating for 20s, then raising to 2500rpm, and rotating for 20s. After the spin coating is finished, the substrate is placed into a vacuum drying oven with the vacuum degree of-0.88 MPa and the temperature of 200 ℃ for curing for 3 hours, and then the substrate film is placed into deionized water to form a substrate film.
(6) And printing a serpentine pattern with the size shown in fig. 4 on the glass plate by using a 300-mesh silk screen, and sintering the glass plate by using a traditional low-temperature heating mode after printing. Namely sintering for 24 hours in air atmosphere by using a heating table at 250 DEG C
(7) And after the treatment is finished, respectively welding two enamelled wires with the diameter of 0.1mm on the two circular electrodes of the snake-shaped electrode by using conductive silver colloid for measuring the resistance change of the sensor caused by the temperature change.
(8) And finally, covering a layer of PDMS solution on the surface by using an inclined flow method to prepare a transparent packaging layer, so as to further protect the embedded substrate type flexible temperature sensor and reduce the influence of the environment on the measurement result. The flexible sensor prepared by the method has the advantages that the sensing electrode and the base film are easy to break and fall off under the bending condition, and the service life is greatly reduced. And the process of printing on the glass substrate is easier to implement than printing on the base film. In this comparative example, a slightly higher spin-coating rotation speed than in example 1 was used to prepare a thinner substrate, but the thinner substrate prepared at a rotation speed outside the preferred range exhibited stronger brittleness rather than flexibility during sintering, resulting in some degree of cracking of a portion of the substrate.
Experimental example 1
The flexible temperature sensor obtained in the embodiment 1 is subjected to a cycle test, the whole temperature sensor is flatly placed in a programmable constant temperature and humidity test box, the periphery of the temperature sensor is fixed by an adhesive tape, four led-out leads are connected with a Keysight 34420A desk-top digital multimeter, and the digital multimeter is connected with a computer, so that data change can be recorded in the computer in real time.
The temperature range manufactured by the set procedure of the test chamber is-10-50 ℃, the frequency of test data is 1 time per minute, the time length of temperature change set by the program in the test chamber is 30min, and the temperature is continuously kept for testing for 60min after the set temperature is reached. We take the last 30min data of each temperature during the stabilization period as a sample (n = 30), and take the average to define the resistance value at this temperature in this cycle. The experimental results are shown in fig. 6 and 7, and the results show that the flexible temperature sensor prepared by the invention has good measurement accuracy, repeatability and linear characteristics.
In order to test the fatigue durability of the embedded electrode, the humidity and temperature sensor obtained in example 1 was cut out and subjected to a bending test. The angle tested was 180 ° and a total of 15000 cycles of bending were performed and the resistance change was measured by the four-wire method. The experimental results are shown in fig. 8, and it was found through testing that the resistance of the sample exhibited a course that first increased slightly, then approached a plateau, and then gradually decreased. This phenomenon occurs because during rapid bending, the internal particles of the sensing electrode rub against each other causing a slight increase in resistance due to an increase in temperature, which gradually decreases after 15000 bends have been completed, and the resistance returns to the initial state. During the bending experiment, the actual resistance change is only changed between 306 and 308m omega, and good mechanical performance and test stability are shown.
Although the invention has been described in detail hereinabove with respect to a general description and specific embodiments thereof, it will be apparent to those skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.
Claims (10)
1. A flexible temperature sensor, comprising:
a base film;
a sensing material electrode embedded in the base film;
and an encapsulation layer;
the sensing electrode material is silver gallium alloy.
2. The flexible temperature sensor according to claim 1, wherein the sensing electrode material is a liquid metal gallium-coated silver electrode, and the thickness of the sensing electrode material is 5-10 um, preferably 7-10 um; preferably, the base film is a polyimide film; the thickness of the base film is not more than 40um, preferably 23 to 40um, and more preferably 25 to 40um.
3. The flexible temperature sensor according to claim 2, wherein the sensing electrode material is embedded in the base film, and a surface of the sensing electrode material is preferably flush with a surface of the base film, and preferably the surface of the sensing electrode material is exposed outside the base film.
4. The flexible temperature sensor according to any one of claims 1 to 3, further comprising a lead wire and a conductive silver paste, wherein the lead wire is connected to the sensing electrode material through the conductive silver paste; preferably, the conductive silver paste and the lead are encapsulated by a transparent encapsulating layer, and preferably, the surface part of the sensing electrode material exposed outside the base film is encapsulated by the transparent encapsulating layer.
5. A method of manufacturing a flexible temperature sensor according to any one of claims 1 to 4, comprising:
1) Mixing the nano silver powder, the liquid metal gallium and the alkaline solution, introducing current, and centrifuging to obtain nano silver gallium particles;
2) Mixing the nano silver-gallium particles with a dispersing agent, and performing ultrasonic dispersion treatment to obtain liquid metal gallium-coated silver particle ink;
3) Printing the silver particle ink coated with the liquid metal gallium on a printing plate through screen printing, after the dispersing agent is volatilized, spin-coating a polyimide solution, and after curing, putting the polyimide solution into water to obtain a base film precursor embedded with a silver-gallium alloy;
4) Carrying out microwave heating sintering treatment on the base film precursor embedded with the silver-gallium alloy to obtain a base film embedded with the silver-gallium alloy;
5) And welding a lead on the circular electrode of the sensing electrode material subjected to microwave heating and sintering, and then packaging.
6. The preparation method of the flexible temperature sensor according to claim 5, wherein in the step 1), 1-2A current is introduced through the graphite electrode for 5-10 min; the centrifugation adopts differential centrifugation, and the rotating speed is 10000-20000 rpm; preferably, the particle size of the nano silver powder is 20-30 nm; the alkaline solution is selected from one or more of sodium hydroxide solution, potassium hydroxide solution and calcium hydroxide solution, preferably the alkaline solution is strong alkaline solution, and the concentration of the alkaline solution is preferably 1-5 mol/L.
7. The method for preparing the flexible temperature sensor according to claim 5 or 6, wherein in the step 2), the power of the ultrasonic dispersion treatment is 150-200W, and the ultrasonic dispersion treatment preferably adopts 10-20 times of circulating ultrasound; preferably, the ultrasonic switch is switched on for 2s and switched off for 2s for 4min each time, the total ultrasonic time is 20-40 min, and water bath cooling is preferably carried out between each cycle; preferably, the dispersing agent is selected from one or more of a PVP aqueous solution with the mass fraction of 10-15%, a PVP n-hexanol solution with the mass fraction of 3-5% and a PVP n-hexanol solution with the mass fraction of 3-5%, and the mass ratio of the nano silver-gallium particles to the dispersing agent is 2.
8. The method for manufacturing a flexible temperature sensor according to any one of claims 5 to 7, wherein in the step 3), the screen-printed screen size is preferably 200 to 500 mesh; setting the rotation speed of the spin coating to be 300-500 rpm in advance, rotating for 15-20 s, then increasing the rotation speed to 1500-2200 rpm, and rotating for 15-20 s; the curing is carried out under the condition of vacuum heating, the vacuum degree is preferably-0.85 to-0.95 MPa, the temperature is preferably 150 to 220 ℃, and the curing time is preferably 2 to 3 hours.
9. The method for preparing a flexible temperature sensor according to any one of claims 5 to 8, wherein in the step 4), the microwave heating treatment time is 1s to 3s, and the sintering temperature is 70 ℃ to 90 ℃.
10. The method of any one of claims 5-9, wherein in step 5) the encapsulated material is selected from one or more of PDMS, ecoflex00-30, casterp-2577; the wires are preferably soldered using conductive silver paste.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117091727A (en) * | 2023-08-24 | 2023-11-21 | 哈尔滨理工大学 | PEO-based implantable battery temperature sensor and preparation method and application thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117091727A (en) * | 2023-08-24 | 2023-11-21 | 哈尔滨理工大学 | PEO-based implantable battery temperature sensor and preparation method and application thereof |
| CN117091727B (en) * | 2023-08-24 | 2024-04-23 | 哈尔滨理工大学 | PEO-based implantable battery temperature sensor and preparation method and application thereof |
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