CN111073024A - Porous dielectric material, preparation method thereof and capacitive pressure sensor - Google Patents
Porous dielectric material, preparation method thereof and capacitive pressure sensor Download PDFInfo
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- 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
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- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/0066—Use of inorganic compounding ingredients
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/14—Measuring force or stress, in general by measuring variations in capacitance or inductance of electrical elements, e.g. by measuring variations of frequency of electrical oscillators
- G01L1/142—Measuring force or stress, in general by measuring variations in capacitance or inductance of electrical elements, e.g. by measuring variations of frequency of electrical oscillators using capacitors
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- 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
- G01L9/12—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 capacitance, i.e. electric circuits therefor
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- C08J2201/00—Foams characterised by the foaming process
- C08J2201/04—Foams characterised by the foaming process characterised by the elimination of a liquid or solid component, e.g. precipitation, leaching out, evaporation
- C08J2201/042—Elimination of an organic solid phase
- C08J2201/0422—Elimination of an organic solid phase containing oxygen atoms, e.g. saccharose
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- 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
- C08J2201/00—Foams characterised by the foaming process
- C08J2201/04—Foams characterised by the foaming process characterised by the elimination of a liquid or solid component, e.g. precipitation, leaching out, evaporation
- C08J2201/044—Elimination of an inorganic solid phase
- C08J2201/0444—Salts
- C08J2201/0446—Elimination of NaCl only
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- 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
- C08J2383/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen, or carbon only; Derivatives of such polymers
- C08J2383/04—Polysiloxanes
Abstract
The invention discloses a porous dielectric material, a preparation method thereof and a capacitive pressure sensor, wherein the preparation method comprises the following steps: mixing a liquid metal and a liquid prepolymer of a polymer according to a predetermined ratio to form a mixed solution; adding a curing agent for the polymer to the mixed solution to form a liquid mixture of the liquid metal and the polymer; fully mixing the liquid mixture with a soluble filling material and carrying out curing treatment to form a curing structure; the soluble filling material is dissolved by using a specific solvent, and finally the solid porous dielectric material with the variable dielectric constant is formed. The capacitive pressure sensor comprises two electrode plates and a flexible dielectric layer positioned between the two electrode plates, wherein the flexible dielectric layer is made of a porous dielectric material. The porous dielectric material has variable dielectric constant and good flexibility; the capacitance type pressure sensor has high sensitivity.
Description
Technical Field
The invention belongs to the technical field of capacitive pressure sensors, and particularly relates to a porous dielectric material, a preparation method of the porous dielectric material and a capacitive pressure sensor.
Background
A pressure sensor is an electronic device that converts a pressure signal into an electric signal, and is widely used in the fields of robots, health care, and the like. The capacitive pressure sensor is a pressure sensor which converts the measured pressure into electric quantity in a certain relation with the measured pressure by using a capacitive sensing element and outputs the electric quantity, and is widely researched in the field of pressure sensors due to the advantages of high sensitivity, independent temperature and the like.
The capacitive pressure sensor is generally composed of a dielectric layer and two electrodes, and external pressure acts on the surface of the sensor to compress the dielectric layer, reduce the distance between two capacitive plates, and change the capacitance between the two capacitive plates, thereby realizing the measurement of the pressure.
For capacitive pressure sensors, sensitivity is an important indicator. The sensitivity is usually increased by using a high compression elastomer with a low young's modulus and by constructing a special structure, the dielectric layer becomes more compressible. However, the dielectric constant of the dielectric substance in the prior art is generally small, and the requirement of improving the sensitivity of the capacitive pressure sensor cannot be further met.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a porous dielectric material, a preparation method thereof and a capacitive pressure sensor. The technical problem to be solved by the invention is realized by the following technical scheme:
one aspect of the present invention provides a method of preparing a porous dielectric material, comprising:
mixing a liquid metal and a liquid prepolymer of a polymer according to a predetermined ratio to form a mixed solution;
adding a curing agent for the polymer to the mixed solution to form a liquid mixture of the liquid metal and the polymer;
fully mixing the liquid mixture with a soluble filling material and carrying out curing treatment to form a curing structure;
and dissolving the soluble filling material in the solidified structure by using a specific solvent to finally form the solid porous dielectric material with the variable dielectric constant.
In one embodiment of the invention, the liquid metal is eutectic gallium indium or gallium indium tin alloy; the polymer is a platinum catalyzed silicone rubber, polydimethylsiloxane, or silicone, and the polymer includes a liquid prepolymer and a cooperating curing agent.
In one embodiment of the invention, if the polymer is a platinum catalyzed silicone rubber or silicone, the ratio of the liquid metal to the liquid prepolymer is from 1:4.5 to 18: 1; if the polymer is polydimethylsiloxane, the ratio of the liquid metal to the liquid prepolymer is 1:9 to 9: 1.
In one embodiment of the present invention, mixing a liquid metal with a liquid prepolymer of a polymer in a predetermined ratio to form a mixed solution includes:
adding the liquid metal to a dispersion solution;
carrying out ultrasonic treatment on the liquid metal in the dispersion solution at the temperature of between 0 and 10 ℃ and with the ultrasonic power of between 40 and 60w for 10min to obtain nano liquid metal droplets;
adding the nano liquid metal droplets into the liquid prepolymer according to a preset proportion;
physically stirring the mixed solution of the liquid metal and the liquid prepolymer at the speed of 1000-2000rpm for 5-10 min;
and standing for more than 24 hours to volatilize the dispersion solution to form a mixed solution of the liquid metal and the liquid prepolymer.
In one embodiment of the present invention, adding a curing agent for the polymer to the mixed solution to form a liquid mixture of the liquid metal and the polymer comprises:
adding a curing agent matched with the liquid prepolymer into the mixed solution of the liquid metal and the liquid prepolymer, and stirring for 5-20min to form a liquid mixture of the liquid metal and the polymer.
In one embodiment of the present invention, the liquid mixture is fully mixed with a soluble filling material and subjected to a curing process to form a cured structure, including:
providing a soluble filling material which can be dissolved in the specific solvent;
intimately mixing the liquid mixture of liquid metal and polymer with the soluble filler material;
heating to solidify the mixture of the liquid mixture and the soluble filler material to form a solidified structure.
In one embodiment of the invention, the soluble filler material is one of sugar particles, wax particles, sodium chloride particles, citric acid particles, or polystyrene particles.
In one embodiment of the invention, when the soluble filler material is sugar particles, wax particles, sodium chloride particles or citric acid particles, the specific solvent is water; when the soluble filler material is polystyrene particles, the specific solvent is toluene.
Another aspect of the present invention provides a porous dielectric material formed by mixing a liquid metal and a polymer and prepared by the preparation method as described in any one of the above embodiments.
Yet another aspect of the present invention provides a capacitive pressure sensor based on porous dielectric material, comprising two electrode plates and a flexible dielectric layer located between the two electrode plates, wherein the flexible dielectric layer is made of the porous dielectric material according to the above embodiment.
Compared with the prior art, the invention has the beneficial effects that:
1. the porous dielectric material is prepared by mixing liquid metal and polymer according to a predetermined ratio, has high dielectric constant and good flexibility, can obviously change the dielectric constant under the condition of pressure, and is suitable for the dielectric layer of the capacitive pressure sensor.
2. The porous dielectric material has variable dielectric constant, and compared with the traditional flexible capacitance sensor based on polymer, the capacitance pressure sensor based on the porous dielectric material can have higher sensitivity and signal-to-noise ratio. In addition, the porous dielectric material has a porous structure and low density, and can be applied to the fields sensitive to quality, such as aerospace, wearable equipment and the like. In addition, the material has good flexibility and compressibility, and can be used in a bending interface and a narrow space.
3. In the preparation process of the porous dielectric material, the liquid mixture of the liquid metal polymer and the soluble filling material are fully mixed and then cured to form a cured structure, and then the soluble filling material in the cured structure is dissolved by a specific solvent to form the porous dielectric material with uniform pores.
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Drawings
FIG. 1 is a flow chart of a method for preparing a porous dielectric material according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a process for preparing a porous dielectric material according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a solidified structure of a mixture of liquid metal, polymer and soluble filler material after solidification according to an embodiment of the present invention;
FIG. 4 is a schematic structural diagram of a porous dielectric material according to an embodiment of the present invention;
FIG. 5 is a graph of the relationship between the volume fraction of liquid metal in a porous dielectric material and the dielectric constant of the resulting porous dielectric material provided by an embodiment of the present invention;
FIG. 6 is a graph of the mechanical properties of a porous dielectric material provided in accordance with an embodiment of the present invention;
FIG. 7 is a graph of the dielectric constant versus pressure for a porous dielectric material according to an embodiment of the present invention;
fig. 8 is a performance graph of a capacitive voltage sensor based on porous dielectric material according to an embodiment of the present invention.
Detailed Description
In order to further illustrate the technical means and effects of the present invention adopted to achieve the predetermined objects, a porous dielectric material, a method for preparing the same, and a capacitive pressure sensor according to the present invention are described in detail below with reference to the accompanying drawings and the detailed description.
The foregoing and other technical matters, features and effects of the present invention will be apparent from the following detailed description of the embodiments, which is to be read in connection with the accompanying drawings. The technical means and effects of the present invention adopted to achieve the predetermined purpose can be more deeply and specifically understood through the description of the specific embodiments, however, the attached drawings are provided for reference and description only and are not used for limiting the technical scheme of the present invention.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or device that comprises a list of elements does not include only those elements but may include other elements not expressly listed. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of additional like elements in the article or device comprising the element.
Example one
Referring to fig. 1, fig. 1 is a flow chart of a method for preparing a porous dielectric material according to an embodiment of the present invention.
The preparation method of the porous dielectric material comprises the following steps:
s1: mixing a liquid metal and a liquid prepolymer of a polymer according to a predetermined ratio to form a mixed solution;
in this embodiment, eutectic gallium indium or gallium indium tin alloy is selected as the liquid metal; platinum catalyzed silicone rubber, Polydimethylsiloxane (PDMS) or silicone is selected as the polymer, and the polymer comprises a liquid prepolymer and a matched curing agent. It should be noted that the silica gel polymer material (e.g., platinum-catalyzed silicone rubber, Polydimethylsiloxane (PDMS), silicone, etc.) used in this example includes two parts before mixing: the prepolymer and the curing agent (cross-linking agent) are used in combination, the two parts are kept in a liquid state for a period of time after being mixed, the mixture gradually becomes a solid state along with the increase of the time, and the curing process can be accelerated by increasing the temperature. In this embodiment, eutectic gallium indium is preferred as the liquid metal component. The metal and the polymer selected in this embodiment are both liquid at room temperature.
And mixing the liquid metal and the prepolymer of the polymer in a liquid state, and keeping the mixed substance in a liquid state to form a mixed solution of the liquid metal and the liquid prepolymer.
Specifically, the S1 includes:
s11: adding the liquid metal into the liquid prepolymer in proportion and stirring to form a mixed solution;
s12: the mixed solution of the liquid metal and the liquid prepolymer is physically stirred at the speed of 1000-.
Further, if the polymer is a platinum catalyzed silicone rubber or silicone, the ratio of the liquid metal to the liquid prepolymer is 1:4.5 to 18:3, preferably 12: 1. Specifically, eutectic gallium indium liquid metal and platinum catalyzed silicone rubber or a liquid prepolymer of a silicone polymer are uniformly mixed in a ratio of 12: 1.
If the polymer is polydimethylsiloxane, the ratio of the liquid metal to the liquid prepolymer is 1:9 to 9:1, preferably 6: 1. Specifically, eutectic gallium indium liquid metal and a liquid prepolymer of Polydimethylsiloxane (PDMS) polymer were mixed uniformly in a ratio of 6: 1.
When the above preferred belgium is selected, the prepared mixed material can be ensured to have higher dielectric constant and better flexibility and stretchability.
In this example, the liquid metal was mixed with the prepolymer of the polymer by means of ultrasonic vibration.
Specifically, the S1 includes:
step 1 a: adding the liquid metal to a dispersion solution;
step 1 b: carrying out ultrasonic treatment on the liquid metal in the dispersion solution for 10min at the temperature of between 0 and 10 ℃ and with the ultrasonic power of between 40 and 60w to obtain nano liquid metal droplets;
step 1 c: adding the nano liquid metal droplets into the liquid prepolymer according to a preset proportion;
step 1 d: physically stirring the mixed solution of the liquid metal and the liquid prepolymer at the speed of 1000-2000rpm for 5-10 min;
step 1 e: and standing for more than 24 hours to volatilize the dispersion solution, thereby forming a mixed solution of the liquid metal and the liquid prepolymer.
The dispersion solution can be selected from volatile solutions such as ethanol, deionized water, toluene and the like.
S2: adding a curing agent for the polymer to the mixed solution to form a liquid mixture of the liquid metal and the polymer;
specifically, a curing agent compounded with the liquid prepolymer is added into a mixed solution of the liquid metal and the liquid prepolymer, and the mixture is stirred for 5 to 20min to form a liquid mixture of the liquid metal and the polymer.
It will be appreciated that for selected silicone based polymeric materials, the mass ratio of prepolymer to curative is generally known in the art, for example for PDMS the cured polymeric material is optimal when the mass ratio of prepolymer to curative is 10: 1; for platinum catalyzed silicone rubbers and silicones, the cured polymer material is best when the prepolymer to curing agent mass ratio is 1: 1. The recommended proportions of prepolymer and curing agent for each polymeric material are selected in this example and are not described herein. Preferably, appropriate heating can be performed in a high temperature oven to accelerate the curing process.
S3: fully mixing the liquid mixture with a soluble filling material and carrying out curing treatment to form a curing structure;
further, the S3 includes:
s31: providing a soluble filling material which can be dissolved in a specific solvent;
specifically, referring to fig. 2, fig. 2 is a schematic view of a process for preparing a porous dielectric material according to an embodiment of the present invention. And mechanically stirring the soluble filling material with a specific volume fraction and the liquid mixing material uniformly. The soluble filling material of the embodiment accounts for 30-70% of the total volume of the soluble filling material and the liquid mixed material. It should be noted that too low a volume fraction of the soluble filler material results in a porous dielectric material with low porosity, and the porous dielectric material with low porosity has a low dielectric constant change under pressure. Too high a volume fraction of the soluble filler material can result in a porous dielectric material that is ultimately formed having a relatively high porosity. The overall structure of the porous dielectric material with higher porosity is unstable, and therefore, in this embodiment, the soluble filler material preferably accounts for 30% -70% of the total volume of the mixture of the liquid mixture and the soluble filler material.
S32: intimately mixing the liquid mixture of liquid metal and polymer with the soluble filler material;
specifically, in this embodiment, the liquid mixture of liquid metal and polymer is mixed with the soluble filler material by mechanical stirring. The soluble filler material is preferably sugar particles, wax particles, sodium chloride particles, citric acid particles or polystyrene particles. It should be noted that, during the mixing process of the liquid mixture and the soluble filling material, the soluble filling material always remains in the form of solid particles, i.e., the solid particles of the soluble filling material are uniformly filled in the liquid mixture of the liquid metal and the polymer.
S33: heating to solidify the mixture of the liquid mixture and the soluble filler material to form a solidified structure.
Preferably, the mixture of the liquid mixture and the soluble filler material may be heated appropriately in a high temperature oven to accelerate the curing process. It is noted that the heating temperature at this time should not exceed the melting temperature of the soluble filler material, so as to prevent the soluble filler material from melting and damaging during the solidification of the liquid mixed solution, thereby affecting the pore uniformity of the finally formed porous dielectric material. Referring to fig. 3, fig. 3 is a schematic view of a solidified structure of a mixture of a liquid metal, a polymer and a soluble filler material, wherein light gray represents the soluble filler material, and dark gray represents a solid mixture of the liquid metal and the polymer.
In this embodiment, the solidification temperature is 50 ℃ to ensure that the liquid mixture of liquid metal and polymer is completely solidified and the soluble filler material does not melt during the solidification process.
S4: and dissolving the soluble filling material by using a specific solvent to form the solid porous dielectric material with the variable dielectric constant.
Specifically, the cured structure formed after curing is placed in a specific solvent in which the soluble filler material is soluble. And heating the specific solvent to dissolve the soluble filling material to form the solid mixed material with uniform holes. In this example, the soluble filler material is polystyrene, the corresponding solvent is toluene, the polystyrene material can be dissolved in toluene, and the mixture of metal and polymer can not be dissolved in toluene, so that a solid mixed material with uniform pores is finally formed after the dissolution of the polystyrene material is completed. In other embodiments, the soluble filler material is sugar particles, wax particles, sodium chloride particles or citric acid particles, and accordingly, the specific solvent is water. Referring to fig. 4, fig. 4 is a schematic structural diagram of a porous dielectric material according to an embodiment of the present invention. The liquid mixture of the liquid metal polymer and the soluble filling material are fully mixed and then solidified to form a solidified structure, and then the soluble filling material in the solidified structure is dissolved by a specific solvent to form the porous dielectric material with uniform pores.
In other embodiments, the soluble filler material may be selected from other soluble materials, so long as the soluble material is soluble in a particular solvent under particular conditions. It is noted that the specific solvent cannot dissolve the solidified mixture of the liquid metal and the polymer. Preferably, the dissolution of the soluble filler material may be accelerated by stirring or heating.
Referring to fig. 5, fig. 5 is a graph illustrating the relationship between the volume fraction of liquid metal in a porous dielectric material and the dielectric constant of the formed porous dielectric material according to an embodiment of the present invention. In the parameter testing process, the liquid metal component is eutectic gallium indium, and the polymer component is platinum-catalyzed silicone rubber. As shown in fig. 5, the relative dielectric constant of the porous dielectric material as a whole gradually increases as the volume fraction of the liquid metal increases. The mass ratio of the liquid metal to the liquid metal polymer mixed material may be 10% to 95%. However, too much liquid metal content can affect the flexibility and tensile behavior of the formed porous dielectric material, while too little liquid metal can result in an insignificant increase in the dielectric constant of the formed porous dielectric material. Thus, in this embodiment, when the liquid metal comprises 92% of the total volume of the liquid metal polymer mixture, the resulting porous dielectric material has more balanced properties.
Referring to fig. 6, fig. 6 is a graph illustrating mechanical properties of a porous dielectric material according to an embodiment of the present invention. As can be seen from fig. 6, as the content of the liquid metal forming the porous dielectric material increases, the young's modulus of the formed porous dielectric material gradually increases. It is well known that the larger the Young's modulus, the less deformable, and therefore, the excessive liquid metal content affects the flexibility and tensile behavior of the formed porous dielectric material.
In this embodiment, the selected polymer is platinum-catalyzed silicone rubber, the liquid metal is eutectic gallium indium, and preferably, the ratio of the platinum-catalyzed silicone rubber to the eutectic gallium indium is 6:1, which can ensure that the prepared porous dielectric material has a high dielectric constant, and also has good flexibility and stretchability.
Referring to fig. 7, fig. 7 is a graph showing a relationship between a dielectric constant and a pressure applied to a porous dielectric material according to an embodiment of the present invention, wherein different curves represent different volume ratios of liquid metal in the porous dielectric material, and the volume ratios of the liquid metal are 0%, 10%, 20%, 30% and 40%, respectively. As shown, in the process of compressing the porous dielectric material formed by the liquid metal polymer, the original air in the porous material is replaced by the liquid metal polymer mixed material with high dielectric constant, resulting in the improvement of the overall dielectric constant of the material. And, as the volume fraction of the liquid metal in the porous dielectric material increases (from 0% by volume to 40% by volume), the relative dielectric constant of the porous dielectric material gradually increases.
The porous dielectric material of the embodiment is prepared by mixing liquid metal and polymer according to a predetermined ratio, has high dielectric constant and good flexibility, can obviously change the dielectric constant under the condition of pressure, and is suitable for the dielectric layer of the capacitive pressure sensor. In the preparation process of the porous dielectric material, the liquid mixture of the liquid metal and the polymer and the soluble filling material are fully mixed and then solidified, and then the soluble filling material is dissolved by the specific solvent, so that the porous dielectric material with uniform pores is formed.
Example two
On the basis of the first embodiment, the present embodiment provides a porous dielectric material for a capacitive pressure sensor, and the porous dielectric material can be prepared by the preparation method described in the first embodiment.
Specifically, in this embodiment, eutectic gallium indium or gallium indium tin alloy is selected as the liquid metal; platinum-catalyzed silicone rubber, Polydimethylsiloxane (PDMS) or silicone is selected as the polymer, and the polymer comprises a liquid prepolymer and a corresponding curing agent.
Further, the liquid metal accounts for 10-95% of the total mass of the porous dielectric material. As shown in example one and fig. 5, the dielectric constant of the dielectric material as a whole gradually increases as the volume fraction of the liquid metal increases. However, too much liquid metal content may affect the flexibility and tensile behavior of the resulting hybrid material, while too little liquid metal may result in an insignificant increase in the dielectric constant of the resulting hybrid material. Therefore, in this embodiment, the ratio of the liquid metal to the total mass of the polymer (including the prepolymer and the curing agent) is preferably about 6:1, so that the properties of the resulting hybrid material are more balanced.
EXAMPLE III
On the basis of the above embodiments, the present embodiment provides a porous dielectric material-based capacitive pressure sensor, which includes two electrode plates and a flexible dielectric layer located between the two electrode plates, wherein the flexible dielectric layer is made of the above porous dielectric material.
Referring to fig. 8, fig. 8 is a performance graph of a capacitive voltage sensor based on a porous dielectric material according to an embodiment of the present invention, in which an abscissa represents a compressive stress and an ordinate represents a capacitance, and different curves represent volume ratios of liquid metals in the porous dielectric material, where the liquid metals are 0%, 10%, 20%, 30% and 40% by volume, respectively. In the parameter testing process, the liquid metal component is eutectic gallium indium, and the polymer component is platinum-catalyzed silicone rubber. As can be seen from fig. 8, the pressure sensitivity and the signal-to-noise ratio based on the capacitive voltage sensor are improved as the volume fraction of the liquid metal in the dielectric material is increased. Specifically, when the porous dielectric material is compressed, the mixture of the liquid metal polymer with a higher dielectric constant can replace air with a lower dielectric constant in the original porous dielectric material, so that the overall dielectric constant is increased, and the improvement of pressure sensitivity and signal-to-noise ratio is realized.
In summary, the porous dielectric material of the present embodiment has a variable dielectric constant and good flexibility, and compared with the conventional flexible capacitive sensor based on a polymer material, the flexible capacitive sensor based on the porous dielectric material can have higher sensitivity and signal-to-noise ratio. In addition, the dielectric material has a porous structure and low density, and can be applied to the fields sensitive to quality, such as aerospace, wearable equipment and the like. In addition, the material has good flexibility and compressibility, and can be used in a bending interface and a narrow space.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.
Claims (10)
1. A method of preparing a porous dielectric material, comprising:
mixing a liquid metal and a liquid prepolymer of a polymer according to a predetermined ratio to form a mixed solution;
adding a curing agent for the polymer to the mixed solution to form a liquid mixture of the liquid metal and the polymer;
fully mixing the liquid mixture with a soluble filling material and carrying out curing treatment to form a curing structure;
and dissolving the soluble filling material in the solidified structure by using a specific solvent to finally form the solid porous dielectric material with the variable dielectric constant.
2. The method of claim 1, wherein the liquid metal is eutectic gallium indium or gallium indium tin alloy; the polymer is a platinum catalyzed silicone rubber, polydimethylsiloxane, or silicone, and the polymer includes a liquid prepolymer and a cooperating curing agent.
3. The method of claim 2, wherein if the polymer is a platinum catalyzed silicone rubber or silicone, the ratio of the liquid metal to the liquid prepolymer is 1:4.5 to 18: 1; if the polymer is polydimethylsiloxane, the ratio of the liquid metal to the liquid prepolymer is 1:9 to 9: 1.
4. The method of claim 2, wherein mixing a liquid metal with a liquid prepolymer of a polymer in a predetermined ratio to form a mixed solution comprises:
adding the liquid metal to a dispersion solution;
carrying out ultrasonic treatment on the liquid metal in the dispersion solution at the temperature of between 0 and 10 ℃ and with the ultrasonic power of between 40 and 60w for 10min to obtain nano liquid metal droplets;
adding the nano liquid metal droplets into the liquid prepolymer according to a preset proportion;
physically stirring the mixed solution of the liquid metal and the liquid prepolymer at the speed of 1000-2000rpm for 5-10 min;
and standing for more than 24 hours to volatilize the dispersion solution to form a mixed solution of the liquid metal and the liquid prepolymer.
5. The method of claim 1, wherein adding a curing agent for the polymer to the mixed solution to form a liquid mixture of the liquid metal and the polymer comprises:
adding a curing agent matched with the liquid prepolymer into the mixed solution of the liquid metal and the liquid prepolymer, and stirring for 5-20min to form a liquid mixture of the liquid metal and the polymer.
6. The method of claim 1, wherein the step of thoroughly mixing the liquid mixture with a soluble filler material and curing the mixture to form a cured structure comprises:
providing a soluble filling material which can be dissolved in the specific solvent;
intimately mixing the liquid mixture of liquid metal and polymer with the soluble filler material;
heating to solidify the mixture of the liquid mixture and the soluble filler material to form a solidified structure.
7. The method of claim 1, wherein the soluble filler material is one of sugar particles, wax particles, sodium chloride particles, citric acid particles, or polystyrene particles.
8. The method of claim 7, wherein when the soluble filler material is sugar particles, wax particles, sodium chloride particles, or citric acid particles, the specific solvent is water; when the soluble filler material is polystyrene particles, the specific solvent is toluene.
9. A porous dielectric material formed by mixing a liquid metal and a polymer, and produced by the production method according to any one of claims 1 to 8.
10. A porous dielectric material based capacitive pressure sensor comprising two electrode plates and a flexible dielectric layer between the two electrode plates, wherein the flexible dielectric layer is made of the porous dielectric material of claim 9.
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