CN111473724A - Capacitive flexible strain sensor and preparation method thereof - Google Patents
Capacitive flexible strain sensor and preparation method thereof Download PDFInfo
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- CN111473724A CN111473724A CN202010407569.5A CN202010407569A CN111473724A CN 111473724 A CN111473724 A CN 111473724A CN 202010407569 A CN202010407569 A CN 202010407569A CN 111473724 A CN111473724 A CN 111473724A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/16—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge
- G01B7/22—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge using change in capacitance
Abstract
The invention provides a capacitive flexible strain sensor and a preparation method thereof, wherein the capacitive flexible strain sensor comprises the following steps: the packaging structure comprises a conductive polar plate, a dielectric layer, a polar plate lead and a packaging layer; the number of the conductive polar plates is more than or equal to three; the dielectric layer, the electrode plate lead and the packaging layer are arranged between the conductive electrode plates; the conductive plate includes: an intermediate electrode plate and an outer electrode plate; the polarity of the middle layer electrode plate is opposite to that of the outer layer electrode plate; the area of the middle layer electrode plate is smaller than or equal to that of the outer layer electrode plate. The invention has the advantages of reliable structure, simple preparation process, less working procedures, loose preparation environment requirement, high repeatability and low cost of raw materials and preparation process.
Description
Technical Field
The invention relates to the technical field of flexible electronics, in particular to a capacitive flexible strain sensor and a preparation method thereof, and particularly relates to a capacitive flexible large strain sensor.
Background
Currently, flexible electronic devices are used in the field of sensors. The sensor is connected into a matched circuit and a signal processor, and the electrical property of the flexible sensor is changed under the external load and the specific environment, so that the signal feedback effect is achieved. With the development of flexible electronic technology and wearable equipment, the stretchable large strain sensor is more and more concerned by people due to excellent stretchability and comfort, and has wide application prospects in the fields of human health/motion monitoring, human body auxiliary rehabilitation systems, robots, human-computer interaction and the like. The flexible sensor has great development potential in the fields of wearable electronic materials and future human-computer interaction, and mainly takes a capacitance sensor and a resistance sensor as main components. The flexible capacitive sensor is usually made of rubber silica gel elastic material as a dielectric layer. The electrode layer is a composite electrode, that is, a conductive network or a conductive film is prepared from a conductive material, and then an organic rubber material with high elasticity is attached to the conductive network or the conductive film to support the electrode layer. The selected conductive materials mainly comprise nano metal wires, carbon fillers (carbon nano tubes, graphene and carbon fibers) and some inorganic conductive particles. In the aspect of preparation process, common preparation methods include spin coating, mold casting, spray coating, 3D printing, photoetching process and the like, and the mixed liquid composite adhesive is prepared into a target structure and a shape by utilizing the processes, so that the flexible conductive structure is obtained. The prior art needs a capacitive flexible large strain sensor.
Patent document CN109883582A discloses a flexible capacitive sensor based on conductive rubber. The sensor takes flexible conductive rubber as a conductive polar plate and flexible pure rubber as a dielectric layer, and each layer of the capacitive sensor is prepared by a spraying process to assist in surface microstructure. The prepared flexible capacitive sensor generates obvious signal response to external load and can be used for tension, compression and motion tests. Wherein the pure rubber of the dielectric layer is prepared by mixing 80-90 wt% of liquid rubber and 10-20 wt% of curing agent; the conductive rubber is prepared by mixing 40-60 wt% of liquid rubber, 10-15 wt% of curing agent, 20-30 wt% of conductive filler and 10-20 wt% of diluent, and the flexible capacitive sensor with good mechanical signal response is obtained after layered spraying and step-by-step or integral curing. The conductive electrode plate layer of the capacitor is made of conductive rubber, and the dielectric layer is made of pure liquid rubber, so that the sensor is a truly completely flexible sensor. The technology and performance of the patent still need to be improved.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a capacitive flexible strain sensor and a preparation method thereof.
According to the present invention there is provided a capacitive flexible strain sensor comprising: the packaging structure comprises a conductive polar plate, a dielectric layer, a polar plate lead and a packaging layer; the number of the conductive polar plates is more than or equal to three; the dielectric layer, the electrode plate lead and the packaging layer are arranged between the conductive electrode plates; the uppermost layer and the lowermost layer of the conductive electrode are used as electrodes with the same polarity, namely, the electrodes are both anodes or both cathodes; the conductive plate includes: an intermediate electrode plate and an outer electrode plate; the polarity of the middle layer electrode plate is opposite to that of the outer layer electrode plate; the area of the middle layer electrode plate is smaller than or equal to that of the outer layer electrode plate. In particular, the polarity of the intermediate layer electrode is opposite to the polarity of the two electrodes of its outer layer. The uppermost layer and the lowermost layer of conductive electrodes are in conductive communication or are in conductive wire communication during fabrication. The area of the middle layer electrode plate is not larger than the area of the uppermost layer electrode plate and the area of the lowermost layer electrode plate.
Preferably, the conductive electrode plate is made of an elastic material.
Preferably, the conductive polar plate is made of silver fiber elastic knitted fabric.
Preferably, the intermediate dielectric layer is made of ecoflex silicone rubber.
Preferably, the intermediate dielectric layer is made of ecoflex silicone rubber added with a dielectric filler.
Preferably, the conductive plate comprises: a rubber matrix, a conductive filler; the conductive filler is added to the rubber matrix.
Preferably, the conductive filler is any one of the following fillers: -a carbon-based filler; -a metal powder; -metal-coated powders.
Preferably, the size scale of the conductive filler is nano-size scale or micron-size scale; the micron-sized conductive filler is any one of the following types: -fibrous; -sheet-like; -spherical.
Preferably, the number of layers of the conductive polar plate is an odd number of more than three layers; the positive and negative polarities of every two adjacent conductive polar plates are opposite; namely, the electrode plate of the current layer adjacent to the electrode plate of the upper layer has different polarity from the electrode plate of the upper layer.
The preparation method of the capacitive flexible strain sensor provided by the invention comprises the following steps: a conductive electrode manufacturing step: silver fibers and spandex fibers are made into the conductive fabric by a knitting machine through a weft knitting process, so that the fabric is elastic in both the radial direction and the weft direction. Wherein, the silver fiber is prepared by a manufacturing process that the nylon fiber inner core of the inner core is plated with silver on the surface; the weight proportion of the silver fiber is 70-90%; the weight proportion of the spandex fiber is 10-30%; a preform manufacturing step: cutting the knitting needle conductive fabric into two parts which are respectively used as an outer layer electrode plate and an intermediate layer electrode plate; i.e., the uppermost and lowermost electrodes and the interlayer electrodes; the areas of the uppermost layer electrode fabric and the lowermost layer electrode fabric are slightly larger than the area of the middle layer electrode fabric. Compounding a polyurethane hot-melt adhesive film to the front or the back of the fabric of the outer electrode plate; folding the fabric compounded with the polyurethane hot-melt adhesive film along the middle line towards one side with the adhesive film to form a folding structure; meanwhile, the fabric of the middle-layer electrode plate is arranged in the middle of the folding structure to form a laminated preformed body; the fabric of the outer electrode plate can completely wrap the fabric of the middle electrode plate; i.e. finally the uppermost and lowermost electrode fabrics are able to completely wrap the middle electrode fabric. Hot press molding: putting the laminated preformed body into a flat ironing press to carry out a hot-pressing gluing process to form a hot-pressed formed product; wherein the hot pressing temperature is between 120 ℃ and 180 ℃, the time is between 30 and 120 seconds, and the pressure is between 0.1 and 0.8 MPa; adding a lead and an insulating sheet: separating the uppermost layer and the middle layer at one end of the hot-press molded product far away from the folding central line, respectively cleaning the glue layers at the separated parts of the uppermost layer and the middle layer, coating a binder at the originally separated parts, and respectively binding the positive lead and the negative lead to the corresponding electrodes of the outer-layer electrode plate and the middle-layer electrode plate; simultaneously, placing hard insulating sheets in the stripping positions of the outer electrode plate and the middle electrode plate, closing and pressurizing the stripped conductive fabrics, and curing according to an adhesive process to finally clamp the hard insulating sheets between the conductive fabrics respectively bonded with the leads;
preferably, the method further comprises the following steps: and (3) packaging: the elastic part of the conductive fabric is encapsulated by the following materials: -ecoflex silica gel; -PDMS silica gel. The elastic part of the laminated fabric structure product which is added with the conducting wire and the insulating sheet in the previous step is encapsulated by ecoflex silica gel or PDMS silica gel and the like according to the conventional process. The non-stretching part of the laminated fabric structure product with the hard insulation sheet sandwiched inside is covered with insulation plastic.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention has the advantages of reliable structure, simple preparation process, less working procedures, loose preparation environment requirement, high repeatability and low cost of raw materials and preparation process.
2. The invention has the function of detecting large tensile strain and has excellent antistatic interference effect. The method can be used for detecting the motion strain of the human body, and the detection accuracy is not influenced by the static electricity of the human body and clothes and the electric field of the environment.
3. Compared with the traditional structure that a shielding conductive layer is added for preventing electrostatic interference, namely the structure that at least four conductive electrodes are needed, the invention can realize the function of preventing electrostatic interference only by three conductive electrodes. The invention reduces the manufacturing cost, improves the preparation efficiency, has thinner thickness and lighter whole body, and is more suitable for being used as a flexible electronic device.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
fig. 1 is a schematic structural diagram of a capacitive sensor with a three-layer conductive electrode plate structure in an embodiment of the present invention.
Fig. 2 is a schematic structural diagram of a capacitive sensor with a seven-layer conductive electrode plate structure according to an embodiment of the present invention.
Fig. 3 is a schematic diagram of an anti-electrostatic interference process of a capacitive sensor with a three-layer conductive electrode plate structure according to an embodiment of the present invention.
In the figure:
1-upper conductive electrode plate; 2-intermediate conductive electrode plate; 3-lower conductive electrode plate; 4-a dielectric layer; 5, packaging layer; 6-conducting wires of positive and negative plates; 7-seven-layer structured outer conductive electrode plate; 8-seven-layer structured inner conductive electrode plate; 9-a dielectric layer of seven-layer structure; 10-a seven-layer structured encapsulation layer; 11-seven layers of conducting wires of positive and negative plates.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.
As shown in fig. 1 to 3, there is provided a capacitive flexible strain sensor according to the present invention, including: the packaging structure comprises a conductive polar plate, a dielectric layer, a polar plate lead and a packaging layer; the number of the conductive polar plates is more than or equal to three; the dielectric layer, the electrode plate lead and the packaging layer are arranged between the conductive electrode plates; the uppermost layer and the lowermost layer of the conductive electrode are used as electrodes with the same polarity, namely, the electrodes are both anodes or both cathodes; the conductive plate includes: an intermediate electrode plate and an outer electrode plate; the polarity of the middle layer electrode plate is opposite to that of the outer layer electrode plate; the area of the middle layer electrode plate is smaller than or equal to that of the outer layer electrode plate. In particular, the polarity of the intermediate layer electrode is opposite to the polarity of the two electrodes of its outer layer. The uppermost layer and the lowermost layer of conductive electrodes are in conductive communication or are in conductive wire communication during fabrication. The area of the middle layer electrode plate is not larger than the area of the uppermost layer electrode plate and the area of the lowermost layer electrode plate.
Preferably, the conductive electrode plate is made of an elastic material.
Preferably, the conductive polar plate is made of silver fiber elastic knitted fabric.
Preferably, the intermediate dielectric layer is made of ecoflex silicone rubber.
Preferably, the intermediate dielectric layer is made of ecoflex silicone rubber added with a dielectric filler.
Preferably, the conductive plate comprises: a rubber matrix, a conductive filler; the conductive filler is added to the rubber matrix.
Preferably, the conductive filler is any one of the following fillers: -a carbon-based filler; -a metal powder; -metal-coated powders.
Preferably, the size scale of the conductive filler is nano-size scale or micron-size scale; the micron-sized conductive filler is any one of the following types: -fibrous; -sheet-like; -spherical.
Preferably, the number of layers of the conductive polar plate is an odd number of more than three layers; the positive and negative polarities of every two adjacent conductive polar plates are opposite; namely, the electrode plate of the current layer adjacent to the electrode plate of the upper layer has different polarity from the electrode plate of the upper layer.
The preparation method of the capacitive flexible strain sensor provided by the invention comprises the following steps: a conductive electrode manufacturing step: silver fibers and spandex fibers are made into the conductive fabric by a knitting machine through a weft knitting process, so that the fabric is elastic in both the radial direction and the weft direction. Wherein, the silver fiber is prepared by a manufacturing process that the nylon fiber inner core of the inner core is plated with silver on the surface; the weight proportion of the silver fiber is 70-90%; the weight proportion of the spandex fiber is 10-30%; a preform manufacturing step: cutting the knitting needle conductive fabric into two parts which are respectively used as an outer layer electrode plate and an intermediate layer electrode plate; i.e., the uppermost and lowermost electrodes and the interlayer electrodes; the areas of the uppermost layer electrode fabric and the lowermost layer electrode fabric are slightly larger than the area of the middle layer electrode fabric. Compounding a polyurethane hot-melt adhesive film to the front or the back of the fabric of the outer electrode plate; folding the fabric compounded with the polyurethane hot-melt adhesive film along the middle line towards one side with the adhesive film to form a folding structure; meanwhile, the fabric of the middle-layer electrode plate is arranged in the middle of the folding structure to form a laminated preformed body; the fabric of the outer electrode plate can completely wrap the fabric of the middle electrode plate; i.e. finally the uppermost and lowermost electrode fabrics are able to completely wrap the middle electrode fabric. Hot press molding: putting the laminated preformed body into a flat ironing press to carry out a hot-pressing gluing process to form a hot-pressed formed product; wherein the hot pressing temperature is between 120 ℃ and 180 ℃, the time is between 30 and 120 seconds, and the pressure is between 0.1 and 0.8 MPa; adding a lead and an insulating sheet: separating the uppermost layer and the middle layer at one end of the hot-press molded product far away from the folding central line, respectively cleaning the glue layers at the separated parts of the uppermost layer and the middle layer, coating a binder at the originally separated parts, and respectively binding the positive lead and the negative lead to the corresponding electrodes of the outer-layer electrode plate and the middle-layer electrode plate; simultaneously, placing hard insulating sheets in the stripping positions of the outer electrode plate and the middle electrode plate, closing and pressurizing the stripped conductive fabrics, and curing according to an adhesive process to finally clamp the hard insulating sheets between the conductive fabrics respectively bonded with the leads;
preferably, the method further comprises the following steps: and (3) packaging: the elastic part of the conductive fabric is encapsulated by the following materials: -ecoflex silica gel; -PDMS silica gel. The elastic part of the laminated fabric structure product which is added with the conducting wire and the insulating sheet in the previous step is encapsulated by ecoflex silica gel or PDMS silica gel and the like according to the conventional process. The non-stretching part of the laminated fabric structure product with the hard insulation sheet sandwiched inside is covered with insulation plastic.
Specifically, in one embodiment, as shown in FIG. 1 and FIG. 2, a capacitive flexible large strain sensor is comprised of three or more layers of conductive plates and a dielectric layer between the conductive plates. The conductive pole plate is made of an elastic material or structure, the silver fiber elastic knitted fabric is a silver fiber and spandex fiber mixed knitted fabric, the middle dielectric layer is ecoflex silicon rubber, and the silicon rubber can be added with dielectric fillers. In addition, the conductive electrode can be a rubber matrix and conductive filler, and is characterized in that the conductive electrode is carbon filler, metal powder or metal-coated powder, the size of the conductive filler is nano-scale or micron-scale, and the shape of the micron-scale filler is divided into fibrous shape, sheet shape and spherical shape. The uppermost layer and the lowermost layer of the conductive electrode are used as the same polarity electrode, namely, the same anode or the same cathode. As shown in fig. 1, in the capacitive sensor structure using three layers of conductive electrodes, the polarity of the middle layer electrode 2 is opposite to the polarities of the two outer layers, i.e., the upper layer conductive electrode plate 1 and the lower layer conductive electrode plate 3. The uppermost layer and the lowermost layer of conductive electrodes are in conductive communication or are in conductive wire communication during fabrication. The area of the middle layer electrode plate is not larger than the area of the uppermost layer electrode plate and the area of the lowermost layer electrode plate. The outermost packaging layer 5 of the capacitive sensor is an insulating elastic material. The leads 6 of the positive and negative electrode plates are respectively connected with the positive and negative conductive electrode plates and led out through the packaging layer 5.
In order to further improve the response performance of the sensor, the number of the conductive electrodes is an odd number of more than three layers, so that the response sensitivity of the capacitor is improved. The polarity of the conductive polar plate is determined by that the positive and negative polarities of every two adjacent polar plates are opposite, namely the polarity of the polar plate of the current layer adjacent to the upper layer polar plate is different from that of the upper layer polar plate. Since the number of layers of the conductive electrodes is an odd number of three or more, the polarity of the uppermost electrode plate is inevitably the same as that of the lowermost electrode plate. In addition, the electrode plates of the same polarity are made to be in a conductive communication state or in a wire communication state at the time of production. As shown in fig. 2, the polarity of the outer conductive electrode plate 7 is opposite to that of the inner conductive electrode plate 8, the outer conductive electrode plate 7 itself is composed of 4 conductive electrode plates, and the inner conductive electrode plate 8 itself is composed of 3 conductive electrode plates, i.e. the present sensor is a seven-layer conductive electrode plate structure. All the conductive electrode plates are filled with a dielectric layer 9. The outermost packaging layer 10 of the capacitance type sensor with the seven-layer structure is the outermost layer of an insulating elastic material. The leads 11 of the positive and negative electrode plates 78 are connected to the positive and negative conductive electrode plates, respectively, and lead out through the encapsulation layer 10.
Taking three layers of conductive electrode plates as an example, the preparation process is as follows:
manufacturing a conductive electrode:
silver fibers and spandex fibers are made into the conductive fabric by a knitting machine through a weft knitting process, so that the fabric is elastic in both the radial direction and the weft direction. The silver fiber material is prepared by a manufacturing process that the nylon fiber inner core of the inner core is plated with silver on the outer surface. The weight proportion of the silver fiber is 70-90%, and the weight proportion of the spandex fiber is 10-30%.
Preparing a preformed body:
the knitting needle conductive fabric is cut into two parts which are respectively used as an uppermost layer electrode, a lowermost layer electrode and an intermediate layer electrode. The areas of the uppermost layer electrode fabric and the lowermost layer electrode fabric are slightly larger than the area of the middle layer electrode fabric. And (3) compounding the polyurethane hot-melt adhesive film to the front or back of the fabric of the uppermost layer and the lowermost layer of the electrode, folding the fabric compounded with the polyurethane hot-melt adhesive film along the middle line towards the surface with the adhesive film, and simultaneously placing the intermediate layer of the electrode fabric in the middle of the folding structure, so that the uppermost layer and the lowermost layer of the electrode fabric can completely wrap the intermediate layer of the electrode fabric.
Hot-press molding:
the laminated preformed body is put into a flat plate ironing press to carry out a hot pressing and gluing process, the hot pressing temperature is between 120 ℃ and 180 ℃, the time is between 30 and 120 seconds, and the pressure is between 0.1 and 0.8 MPa.
Adding a lead and an insulating sheet:
and peeling a part of the uppermost layer and the middle layer of the end of the hot-press molded product far away from the folding middle line. Cleaning up the glue layers of the peeling parts of the uppermost layer and the middle layer respectively, coating a binder on the original peeling parts, bonding the positive electrode lead and the negative electrode lead to respective electrodes respectively, simultaneously placing a hard insulating sheet on the peeling parts of the uppermost layer and the middle layer, closing and pressurizing the peeled uppermost layer and the middle layer fabric, and curing according to a binder process, so that the hard insulating sheet is clamped between the electrode fabrics which are bonded with the leads respectively.
Packaging:
and (3) packaging the elastic part of the laminated fabric structural product with the conducting wire and the insulating sheet in the last step by using ecoflex silica gel or PDMS silica gel and the like according to a conventional process. The non-stretching part of the laminated fabric structure product with the hard insulation sheet sandwiched inside is covered with insulation plastic.
Description of antistatic Process:
the capacitive sensor with the three-layer conductive electrode plate structure is taken as an example to illustrate the anti-electrostatic interference process of the capacitive sensor with the structure, and the thickness of the sensor is thin enough, and the edge effect is ignored. In the absence of an external electric field or static charge, for example, if the upper and lower electrode plates 1 and 3 are negative electrode plates and the intermediate layer 2 is a positive electrode plate, the negative charge is distributed on the lower surface of the upper electrode plate 1 and the lower electrode plate 2 due to the attraction of the positive and negative chargesOn the upper surface, positive charges are distributed on the upper and lower surfaces of the positive plate of the intermediate layer 3, respectively. Because the inside of the conductive polar plate is an equipotential body, positive and negative charges are not distributed in the inside of the polar plate but distributed on the outer surface of the polar plate, and a charge distribution schematic diagram is shown in fig. 3. QAFor the amount of electric charge, Q, distributed on the lower surface of the upper electrode plateBThe quantity of charge distributed on the upper surface of the positive electrode plate as an intermediate layer is equal to that of the positive electrode plate as determined by Gauss's law, i.e., QA＝QB(ii) a In the same way, QCFor the quantity of electric charge, Q, distributed on the lower surface of the intermediate positive plateDFor the amount of electric charge distributed on the upper surface of the lower electrode plate, QC＝QD。UABIs the potential difference between the lower surface of the upper electrode plate and the upper surface of the middle positive electrode plate, EABIs the electric field between the lower surface of the upper electrode plate and the upper surface of the middle positive electrode plate, dABThe distance between the lower surface of the upper electrode plate and the upper surface of the middle positive electrode plate is UAB＝EAB×dAB。UCD、ECDAnd dCDThe potential difference, the electric field and the distance between the upper surface of the lower electrode plate and the lower surface of the middle positive electrode plate are respectively UCD＝ECD×dCD. The three-layer conductive electrode plate structure with the upper and lower layers conducted is equivalent to a two-layer capacitor CABAnd a two-layer capacitor CCDConnected in parallel, the capacitors are connected in parallel, and the capacitor is defined as C ═ Q/U, so that C ═ C can be obtainedAB+CCD＝QA/UAB+QD/UCD. Usually, the external electric field affects the potential difference and the charge amount between the capacitor electrode plates, which causes the capacitance detection circuit to misjudge the capacitance of the capacitor itself, resulting in the change of the detected capacitance value, however, the capacitance of the capacitor is determined by the geometric dimension and the material property, and is not related to the external electric field, as known from the parameter formula C of the capacitor, which is S/4 pi kd.
When positive charges exist above the capacitor or the capacitor is in a positive electric field, the electrostatic shielding phenomenon is generated due to the structure of the three-layer conductive electrode plate with the upper layer and the lower layer conducted, and the positive electric field outside the upper electrode plate enables the lower surface of the lower electrode plate to be under the lower surface of the lower electrode plateThe electrons migrate to the outer surface of the upper electrode plate along the conducted part of the upper and lower electrode plates, and finally reach an electrostatic balance state. In the whole process, an equipotential body is arranged between the outer surface of the upper electrode plate and the outer surface of the lower electrode plate, and external charges or electrostatic fields above the capacitor do not influence the charge amount and the electric field distribution in the equipotential body, so that Q is realizedA、QDAnd UABAnd UCDAll do not receive the influence of outside electric field, can not cause the change of electrical parameter among the electric capacity detection circuitry, adopt the condenser of this three-layer conductive electrode plate structure to have excellent antistatic interference effect promptly.
Similarly, for a capacitive sensor with an odd number of conductive electrodes having more than three layers, because the uppermost layer and the lowermost layer have the same polarity and are in a conductive communication state, the two outermost electrodes can generate electrostatic shielding for all internal electrodes (including all internal positive plates and negative plates). Therefore, the external electric field can not change the charge quantity of all the inner positive plates and the negative plates and the potential difference between the inner positive plates and the inner negative plates, the change of electrical parameters in the capacitance detection circuit can not be caused, and the capacitor adopting the structure with more than three odd-numbered conductive electrode plates has an excellent antistatic interference effect.
The invention has the advantages of reliable structure, simple preparation process, less working procedures, loose preparation environment requirement, high repeatability and low cost of raw materials and preparation process. The invention has the function of detecting large tensile strain and has excellent antistatic interference effect. The method can be used for detecting the motion strain of the human body, and the detection accuracy is not influenced by the static electricity of the human body and clothes and the electric field of the environment. Compared with the traditional structure that a shielding conductive layer is added for preventing electrostatic interference, namely the structure that at least four conductive electrodes are needed, the invention can realize the function of preventing electrostatic interference only by three conductive electrodes. The invention reduces the manufacturing cost, improves the preparation efficiency, has thinner thickness and lighter whole body, and is more suitable for being used as a flexible electronic device.
In the description of the present application, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience in describing the present application and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present application.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.
Claims (10)
1. A capacitive flexible strain sensor, comprising: the packaging structure comprises a conductive polar plate, a dielectric layer, a polar plate lead and a packaging layer;
the number of the conductive polar plates is more than or equal to three;
the dielectric layer, the electrode plate lead and the packaging layer are arranged between the conductive electrode plates;
the conductive plate includes: an intermediate electrode plate and an outer electrode plate;
the polarity of the middle layer electrode plate is opposite to that of the outer layer electrode plate;
the area of the middle layer electrode plate is smaller than or equal to that of the outer layer electrode plate.
2. The capacitive flexible strain sensor of claim 1, wherein the conductive plate is made of an elastic material.
3. The capacitive flexible strain sensor of claim 2, wherein the conductive plate is made of a silver fiber elastic knitted fabric.
4. The capacitive flexible strain sensor of claim 1, wherein the intermediate dielectric layer is ecoflex silicone rubber.
5. The capacitive flexible strain sensor of claim 4, wherein the intermediate dielectric layer is ecoflex silicone rubber with added dielectric filler.
6. The capacitive flexible strain sensor of claim 2, wherein the conductive plate comprises: a rubber matrix, a conductive filler;
the conductive filler is added to the rubber matrix;
the conductive filler adopts any one of the following fillers:
-a carbon-based filler;
-a metal powder;
-metal-coated powders.
7. The capacitive flexible strain sensor of claim 6, wherein the conductive filler is on a nanometer scale or a micrometer scale;
the micron-sized conductive filler is any one of the following types:
-fibrous;
-sheet-like;
-spherical.
8. The capacitive flexible strain sensor according to claim 1, wherein the number of layers of the conductive plate is an odd number of three or more layers;
the positive and negative polarities of every two adjacent conductive polar plates are opposite.
9. A preparation method of a capacitive flexible strain sensor is characterized by comprising the following steps:
a conductive electrode manufacturing step: manufacturing silver fibers and spandex fibers into a conductive fabric;
wherein, the silver fiber is prepared by a manufacturing process that the nylon fiber inner core of the inner core is plated with silver on the surface;
the weight proportion of the silver fiber is 70-90%;
the weight proportion of the spandex fiber is 10-30%;
a preform manufacturing step: cutting the conductive fabric into two parts which are respectively used as an outer layer electrode plate and an intermediate layer electrode plate; compounding a polyurethane hot-melt adhesive film to the front or the back of the fabric of the outer electrode plate; folding the fabric compounded with the polyurethane hot-melt adhesive film along the middle line towards one side with the adhesive film to form a folding structure; meanwhile, the fabric of the middle-layer electrode plate is arranged in the middle of the folding structure to form a laminated preformed body;
the fabric of the outer electrode plate can completely wrap the fabric of the middle electrode plate;
hot press molding: putting the laminated preformed body into a flat ironing press to carry out a hot-pressing gluing process to form a hot-pressed formed product;
wherein the hot pressing temperature is between 120 ℃ and 180 ℃, the time is between 30 and 120 seconds, and the pressure is between 0.1 and 0.8 MPa;
adding a lead and an insulating sheet: stripping the upper layer and the middle layer at one end of the hot-press molded product far away from the folding central line to form a part, respectively cleaning the glue layers of the stripped parts of the upper layer and the middle layer, coating a binder on the originally stripped parts, and respectively binding the positive lead and the negative lead to electrodes corresponding to the outer-layer electrode plate and the middle-layer electrode plate; and simultaneously, placing hard insulating sheets in the stripping positions of the outer-layer electrode plate and the middle-layer electrode plate, closing and pressurizing the stripped conductive fabrics, and curing according to an adhesive process to enable the hard insulating sheets to be clamped between the conductive fabrics respectively bonded with the leads.
10. The method of making a capacitive flexible strain sensor of claim 9, further comprising: and (3) packaging: the elastic part of the conductive fabric is encapsulated by the following materials:
-ecoflex silica gel;
-PDMS silica gel.
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| CN202010407569.5A CN111473724A (en) | 2020-05-14 | 2020-05-14 | Capacitive flexible strain sensor and preparation method thereof |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113635817A (en) * | 2021-08-24 | 2021-11-12 | 艾福迈汽车***(上海)有限公司 | Seat capacitive sensor based on conductive fabric and measuring method |
| CN114160309A (en) * | 2021-11-25 | 2022-03-11 | 中山尚诚环保科技有限公司 | Manufacturing method of flexible electrostatic sheet main body, flexible electrostatic sheet main body and filter |
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| CN114160309B (en) * | 2021-11-25 | 2022-11-04 | 中山尚诚环保科技有限公司 | Manufacturing method of flexible electrostatic sheet main body, flexible electrostatic sheet main body and filter |
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