CN115406564A - A capacitive flexible pressure sensor with adjustable range and sensitivity - Google Patents

Abstract

The invention discloses a capacitive flexible pressure sensor with adjustable range and sensitivity, which comprises a first pole plate, a second pole plate and an elastic medium, the elastic medium is used to isolate and support the first pole plate and the second pole plate, and the elastic The medium is a heat-sensitive material and equipped with a heat source. The higher the temperature of the elastic medium, the lower the elastic modulus. The present invention energizes the conductive silica gel, uses Joule heat to increase the temperature of the conductive silica gel, changes the elastic modulus of the elastic medium inside the capacitive pressure sensor, and then realizes the adjustment of the detection range and sensitivity of the pressure sensor; the preparation process of the pressure sensor of the present invention and The process is simple, and has the advantages of low cost and high reliability.

Description

A capacitive flexible pressure sensor with adjustable range and sensitivity

technical field

The invention relates to the technical field of heating and cooling, in particular to a capacitive flexible pressure sensor with adjustable range and sensitivity.

Background technique

In recent years, with the discovery of new materials and the advancement of technology, significant progress and development have been made in the research and development of flexible sensors, which can be applied to human motion detection, health diagnosis, smart clothing, electronic skin, automobile industry, man-machine Interface, mobile communication and other fields, especially in wearable electronic devices, medical equipment, electronic skin and other fields. However, in practical applications, due to the limitations of materials and spatial structure design, the sensitivity performance parameters of the existing flexible pressure sensor cannot be adjusted after the preparation is completed, and only have a single, limited measurement range, and its range is fixed. It is difficult to achieve high sensitivity and wide linear range at the same time.

Patent document CN113091961A discloses an adjustable range capacitive flexible pressure sensor and its preparation method. A magnetorheological medium layer is arranged between the two electrodes of the capacitor, and the mechanical properties of the magnetorheological medium layer are adjusted by an external magnetic field. The advantage is that the capacitor The disadvantage of realizing the adjustment of the sensor pressure detection range is that only the adjustment of the range can be realized, and the preparation of the magnetorheological medium layer is relatively complicated, which affects its popularization and application.

Contents of the invention

In order to improve the performance of the flexible pressure sensor and increase its application range, the invention provides a capacitive flexible pressure sensor with adjustable range and sensitivity.

The technical solution adopted by the present invention is as follows: a capacitive flexible pressure sensor with adjustable range and sensitivity, including a first pole plate, a second pole plate and an elastic medium, and the elastic medium is used to isolate and support the first pole plate and the second pole plate. For the polar plate, the elastic medium is a heat-sensitive material and equipped with a heat source. The higher the temperature of the elastic medium, the lower the elastic modulus.

Preferably, the elastic medium is a box-shaped structure of resin material with a cavity inside, and the heat source is placed in the cavity.

Preferably, the heat source is conductive silica gel, which generates Joule heat after being electrified.

Preferably, the conductive silica gel is formed by adding conductive powder to liquid silica gel and curing it.

Preferably, the liquid silica gel is Ecoflex type platinum-catalyzed silica gel produced by Smooth-On Company.

Preferably, the conductive powder is selected from one or more of carbon-based fillers, metal fillers or metal compounds.

Preferably, it is applied to the measurement of high pressure at normal temperature; it is applied to the measurement of small pressure and high sensitivity under the state of heating by a heat source.

A method for preparing a capacitive flexible pressure sensor with adjustable range and sensitivity, the steps are as follows:

Step 1, prepare the heat source, add conductive powder to the liquid silica gel and stir evenly, introduce it into the mold for plasticity, and obtain conductive silica gel after curing and molding, and fix the heating wire on the upper and lower surfaces;

Step 2, prepare the resin box, pour the resin particles into the mold after melting, and obtain the box body and the upper cover respectively;

Step 3, assemble the elastic medium, put the box body, heat source and upper cover in the assembly mold in sequence, and heat for packaging and shaping;

Step 4, assembling the pole plates, attaching the first pole plate and the second pole plate to the upper and lower surfaces of the elastic medium respectively, and connecting the capacitor wires.

Preferably, in step 1, the heating wire is fixed on the upper and lower surfaces of the conductive silica gel with copper tape, and the area of the copper tape is the same as that of the upper and lower surfaces of the conductive silica gel.

Preferably, in step 2, copper tape is used for the first pole plate and the second pole plate.

The present invention has the following beneficial effects: the present invention uses Joule heat to increase the temperature of the conductive silica gel by electrifying the conductive silica gel, thereby changing the elastic modulus of the elastic medium inside the capacitive pressure sensor, thereby realizing the adjustment of the detection range and sensitivity of the pressure sensor; The preparation flow and process of the inventive pressure sensor are simple, and have the advantages of low cost and high reliability.

Description of drawings

Fig. 1 is a three-dimensional schematic diagram of a pressure sensor in an embodiment of the present invention.

Fig. 2 is a schematic explosion diagram of the pressure sensor in the embodiment of the present invention.

Fig. 3 is a diagram of the preparation process of the box-shaped elastic medium in the embodiment of the present invention.

Fig. 4 is a diagram of the preparation process of conductive silica gel in the embodiment of the present invention.

Fig. 5 is a schematic diagram of the assembly of the pressure sensor in the embodiment of the present invention.

Fig. 6 is the stress-strain relationship of the resin at different temperatures in the embodiment of the present invention.

Fig. 7 shows the elastic modulus relationship of the resin when the strain amount is 30% in the embodiment of the present invention.

Fig. 8 shows the rate of change of pressure and capacitance of the sensor of this embodiment under the conditions of 25°C and 40°C in the embodiment of the present invention.

In the figure, 1-upper cover, 2-lower box body, 3-silica gel blank, 4-conductive silica gel, 5-first copper tape, 6-second copper tape, 7-heating wire, 8-heat source, 9-elasticity Medium, 10-third copper tape, 11-fourth copper tape, 12-capacitor wire, 13-first mold, 14-second mold, 15-third mold, 16-fourth mold.

Detailed ways

The present invention will be further described below in conjunction with the embodiments and accompanying drawings.

1. Sensor structure.

As shown in Figures 1 and 2, it is a capacitive flexible pressure sensor with adjustable range and sensitivity. It has a sandwich structure as a whole, with a first plate and a second plate above it, and an elastic medium between the two plates. 9. The first pole plate and the second pole plate are composed of the third copper tape 10 and the fourth copper tape 11 respectively, and are electrically connected with the capacitor wire 12 . The elastic medium 9 is a silicone box composed of an upper cover 1 and a lower box body 2. A heat source 8 is placed inside the silicone box. The heat source 8 is formed by laminating the first copper tape 5, the second copper tape 6 and the conductive silica gel 4. The first copper tape The adhesive tape 5 and the second copper adhesive tape 6 are electrically connected to the heating wire 7, and the conductive silica gel 4 emits Joule heat after being electrified. The principle of this embodiment is: by energizing the conductive silica gel 4 and using Joule heat to increase the temperature, the elastic modulus of the elastic medium 9 inside the capacitive pressure sensor is changed, thereby realizing the adjustment of the detection range and sensitivity of the pressure sensor. By adjusting the current, the control of Joule's heat can be easily realized, and the temperature of the elastic medium 9 can be accurately controlled.

Second, the sensor preparation method.

As shown in Figures 3 to 5, the process of preparing such a capacitive flexible pressure sensor with adjustable range and sensitivity for the laboratory environment conditions is to design the three-dimensional model of the pressure sensor and the model of each mold by using three-dimensional software in advance, and use the 3D Printer prints. The preparation process mainly includes three steps: preparing the upper cover 1 and the lower box body 2, preparing the heat source 8, and overall assembling. The preparation method of this embodiment has the advantages of low cost, high efficiency and less pollution.

As shown in Figure 3, it is the preparation steps of the upper cover 1 and the lower box body 2:

(1) Take an appropriate amount of resin particles in a beaker, heat in an oven at 60°C for 10 minutes to melt;

(2) Pour the molten resin into the first mold 13 and the second mold 14 for plasticity;

(3) Take it out after it cools down and trim it to get the upper cover 1 and the lower box body 2 .

As shown in Figure 4, it is the preparation steps of heat source 8:

(1) Mix Ecoflex and graphene at a ratio of 10:1 and stir evenly;

(2) Pour the mixed solution into the third mold 15, trim the surface, put it on one side and let it solidify naturally to obtain the silica gel blank 3;

(3) Take out the silica gel blank 3, trim burrs and other defects, and obtain the conductive silica gel 4;

(4) Fix the heating wire 7 on the upper and lower surfaces of the conductive silica gel 4 through the first copper tape 5 and the second copper tape 6, wherein the size of the first copper tape 5 and the second copper tape 6 is required to be the same as the surface of the conductive silica gel 4 The size is the same, and finally presents the structure of the first copper tape 5-heating wire 7-conductive silica gel 4-heating wire 7-second copper tape 6.

As shown in Figure 5, the preparation steps for the overall assembly:

(1) Put the lower box body 2, the heat source 8, and the lower box body 2 into the fourth mold 16 in sequence;

(2) Heat the fourth mold 16 in an oven at 60°C for encapsulation and shaping, take out the mold after about 20 minutes and wait for it to cool;

(3) Take out the plastic finished product, trim the edge burrs, and obtain the elastic medium 9, that is, the intermediate medium layer of the sensor is prepared;

(4) Fix the capacitance wire 12 on the upper and lower surfaces of the elastic medium 9 by passing the third copper tape 10 and the fourth copper tape 11, the sensor is prepared, and finally form the third copper tape 10-capacitance wire 12-elastic medium 9-capacitance wire 12 - The structure of the fourth copper tape 11 .

3. Experimental analysis.

Figure 6 shows the stress-strain relationship of the resin at different temperatures. The elastic modulus is the ratio of the stress to the strain. It can be seen from Figure 6 that the strain of the resin has a good linear relationship in the range of 20%-40%. Elastic Modulus.

Figure 7 shows the elastic modulus relationship of the resin when the strain is 30%. In this embodiment, the elastic modulus of the Ecoflex and graphene composite material (conductive silica gel 4) is significantly smaller than that of the resin (the upper cover 1 and the lower box body 2), so the elastic modulus of the elastic medium 9 is mainly determined by the resin. Therefore, only the resin is considered when considering the modulus of elasticity of the elastic medium 9 . It can be seen from FIG. 7 that the elastic modulus of the elastic medium 9 inside the sensor decreases with the increase of temperature.

Fig. 8 shows the rate of change of pressure and capacitance of the sensor of this embodiment at 25°C and 40°C. At 25°C, the elastic modulus of the elastic medium 9 is large, and the sensor has the function of measuring large pressure; when the temperature reaches 40°C, the elastic modulus of the elastic medium 9 decreases significantly, and the sensor has high sensitivity characteristics, and can detect small The change of pressure, according to this characteristic, can choose the appropriate sensor range according to the needs of users.

In addition, since the resin will enter a melting state when the temperature is higher than 50°C, if the temperature is higher than 50°C during use, the sensor will lose its detection function due to the melting of the resin, so the upper limit of the sensor’s operating temperature is set to 40°C. It can effectively avoid sensor failure due to temperature rise caused by external factors.

Apparently, the above-mentioned embodiments of the present invention are only examples for illustrating the present invention, rather than limiting the implementation of the present invention. Other obvious changes or changes derived from the essence and spirit of the present invention still fall within the protection scope of the present invention.

Claims (10)

1. A capacitive flexible pressure sensor with adjustable range and sensitivity, comprising a first pole plate, a second pole plate and an elastic medium, and the elastic medium is used to isolate and support the first pole plate and the second pole plate, characterized in that , the elastic medium is a heat-sensitive material and equipped with a heat source, the higher the temperature of the elastic medium, the lower the elastic modulus. 2. A capacitive flexible pressure sensor with adjustable range and sensitivity according to claim 1, characterized in that the elastic medium is a box-shaped structure of resin material, with a cavity inside, and the heat source is placed in the cavity. 3. A capacitive flexible pressure sensor with adjustable range and sensitivity according to claim 2, characterized in that the heat source is conductive silica gel, which generates Joule heat after being electrified. 4. A capacitive flexible pressure sensor with adjustable range and sensitivity according to claim 3, characterized in that the conductive silica gel is formed by adding conductive powder to liquid silica gel and then solidified. 5 . A capacitive flexible pressure sensor with adjustable range and sensitivity according to claim 4 , wherein the liquid silica gel is Ecoflex platinum-catalyzed silica gel produced by Smooth-On Company. 6. A capacitive flexible pressure sensor with adjustable range and sensitivity according to claim 4, characterized in that the conductive powder is selected from one or more of carbon-based fillers, metal fillers or metal compounds. 7. A capacitive flexible pressure sensor with adjustable range and sensitivity according to claim 1, characterized in that, under normal temperature, it is applied to the measurement of large pressure; under the state of heating by a heat source, it is applied to small pressure and high sensitivity Measurement. 8. A method for preparing a capacitive flexible pressure sensor with adjustable range and sensitivity, characterized in that the steps are as follows: Step 1, prepare the heat source, add conductive powder to the liquid silica gel and stir evenly, introduce it into the mold for plasticity, and obtain conductive silica gel after curing and molding, and fix the heating wire on the upper and lower surfaces; Step 2, prepare the resin box, pour the resin particles into the mold after melting, and obtain the box body and the upper cover respectively; Step 3, assemble the elastic medium, put the box body, heat source and upper cover in the assembly mold in sequence, and heat for packaging and shaping; Step 4, assembling the pole plates, attaching the first pole plate and the second pole plate to the upper and lower surfaces of the elastic medium respectively, and connecting the capacitor wires. 9. the preparation method of a kind of range and sensitivity-adjustable capacitive flexible pressure sensor according to claim 8, is characterized in that, in step 1, the upper and lower surfaces of conductive silica gel are fixed heating wire by copper tape, and the copper tape area and The upper and lower surface areas of conductive silicone are the same. 10 . The method for preparing a capacitive flexible pressure sensor with adjustable range and sensitivity according to claim 8 , wherein in step 2, copper tape is used for the first pole plate and the second pole plate. 11 .

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