CN113670187A - Capacitive elastic strain sensor with high safety and high detection range and preparation method thereof - Google Patents
Capacitive elastic strain sensor with high safety and high detection range and preparation method thereof Download PDFInfo
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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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B25/00—Layered products comprising a layer of natural or synthetic rubber
- B32B25/04—Layered products comprising a layer of natural or synthetic rubber comprising rubber as the main or only constituent of a layer, which is next to another layer of the same or of a different material
- B32B25/08—Layered products comprising a layer of natural or synthetic rubber comprising rubber as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
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- B32B25/00—Layered products comprising a layer of natural or synthetic rubber
- B32B25/12—Layered products comprising a layer of natural or synthetic rubber comprising natural rubber
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- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
- B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/12—Layered products comprising a layer of synthetic resin next to a fibrous or filamentary layer
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- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
- B32B27/308—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising acrylic (co)polymers
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- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/40—Layered products comprising a layer of synthetic resin comprising polyurethanes
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- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B33/00—Layered products characterised by particular properties or particular surface features, e.g. particular surface coatings; Layered products designed for particular purposes not covered by another single class
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
- B32B5/02—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer
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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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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2255/00—Coating on the layer surface
- B32B2255/10—Coating on the layer surface on synthetic resin layer or on natural or synthetic rubber layer
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2255/00—Coating on the layer surface
- B32B2255/20—Inorganic coating
- B32B2255/205—Metallic coating
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2255/00—Coating on the layer surface
- B32B2255/26—Polymeric coating
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
- B32B2262/02—Synthetic macromolecular fibres
- B32B2262/0292—Polyurethane fibres
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2307/00—Properties of the layers or laminate
- B32B2307/50—Properties of the layers or laminate having particular mechanical properties
- B32B2307/51—Elastic
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Abstract
The invention provides a capacitive elastic strain sensor with high safety and high detection range and a preparation method thereof. The sensor comprises a substrate made of elastic textile materials, an elastic bonding layer, a first conductive layer, an elastic dielectric layer and a second conductive layer; the elastic dielectric layer consists of three layers which are stacked up and down, wherein one layer is a first elastic dielectric layer with high elastic modulus, the other layer is a second elastic dielectric layer with low elastic modulus, and the other layer is a swelling plastic fluid layer which is clamped between the first elastic dielectric layer and the second elastic dielectric layer; the swelling plastic fluid layer is composed of an elastic annular structure and swelling plastic fluid arranged inside the annular structure. The sensor can improve the safety protection effect, effectively broadens the range of detectable stress and has very good application prospect.
Description
Technical Field
The invention relates to the technical field of capacitive strain sensors, in particular to a capacitive elastic strain sensor with high safety and high detection range and a preparation method thereof.
Background
In recent years, flexible electronic technology is widely concerned, and particularly with the development of wearable technology, the demand for flexible elastic sensing devices is increasing, for example, smart clothes and smart wearing are rising, and the combination of elastic strain sensors and textile materials is the mainstream trend of future smart clothes and smart wearing.
CN 110657741 a discloses a capacitive elastic strain sensor, which sequentially comprises an elastic substrate, an elastic bonding layer, a first conductive layer, an elastic dielectric layer, a second conductive layer, and an elastic encapsulation layer, wherein the first conductive layer and the second conductive layer are respectively composed of a conductive liquid, a conductive paste, or a conductive gel. The sensor has an excellent elastic strain response function, and also has good wearability and comfort, and deforms when stressed to cause the change of the space or the relative area between the first conductive layer and the second conductive layer, so that the capacitance is changed, and the stress can be detected according to the change of the capacitance. However, this sensor has the following problems:
(1) the sensor has elasticity and is deformed under the action of stress, but the deformation range is limited and is related to the actual material of each layer, for example, when the external stress is larger, the actual deformation of the sensor under the stress exceeds the upper limit of the deformation detectable by the sensor, which can cause the problems of inaccurate detection of the sensor, reduced sensitivity, sensor damage and the like; when the external stress is small and the actual deformation of the sensor under the stress is lower than the lower deformation limit of the sensor, the sensor cannot detect the stress.
Therefore, how to improve the detectable stress range (i.e. detection range) of the sensor to make the sensor sensitive to weak stress and capable of detecting the micro stress, bearing deformation under the action of large stress and detecting large stress has important significance, and is beneficial to widening the application of the sensor and improving the sensitivity.
(2) In practical applications, the sensor may be subjected to a stress action of high-speed motion (i.e., the rate of the stress is high), such as bullet penetration in high-speed flight, rapid sword strike, high-speed slapping, striking, colliding, kneading, squeezing, etc., and even if the stress action is small in value, the sensor is high in momentum due to high rate, so that the destructiveness of the sensor is greatly improved, and even when the sensor is worn on a living body, the living body is seriously damaged.
Therefore, the popularization and application of the sensor must be based on reliable safety, especially in extreme cases and when the sensor is worn on a living body, important considerations are needed.
Disclosure of Invention
In view of the above technical situation, the present invention provides a capacitive elastic strain sensor, which not only has excellent sensing function, good wearability and comfort, but also has high safety and high detection range.
The technical scheme of the invention is as follows: a capacitive elastic strain sensor with high safety and high detection range sequentially comprises a substrate made of elastic textile materials, an elastic bonding layer, a first conductive layer, an elastic dielectric layer and a second conductive layer from bottom to top;
the substrate is made of elastic textile material;
the elastic bonding layer is positioned on the surface of the substrate and has conductive insulation property;
the first conducting layer is positioned on the surface of the elastic bonding layer, is composed of conducting liquid, conducting slurry or conducting gel and is connected with the first electrode;
the elastic dielectric layer is positioned on the surface of the first conductive layer and has conductive insulativity;
the second conducting layer is positioned on the surface of the elastic dielectric layer, is composed of conducting liquid, conducting slurry or conducting gel and is connected with the second electrode;
the method is characterized in that: the elastic dielectric layer consists of three layers which are stacked up and down, wherein one layer is a first elastic dielectric layer with high elastic modulus, the other layer is a second elastic dielectric layer with low elastic modulus, and the other layer is a swelling plastic fluid layer which is clamped between the first elastic dielectric layer and the second elastic dielectric layer; the swelling plastic fluid layer is composed of an elastic annular structure and swelling plastic fluid arranged inside the annular structure.
In the present invention, the term "flexible" means that deformation such as bending, stretching, twisting, etc. can be caused by an external force. Elasticity is one of flexibility, and refers to a property that can be deformed such as bending, stretching, twisting, etc. under an external force, and has a certain shape recovery capability when the external force is removed.
The upper and lower positions of the first elastic dielectric layer and the second elastic dielectric layer are not limited, and the first elastic dielectric layer is arranged on the surface of the first conductive layer, and the second conductive layer is arranged on the surface of the second elastic dielectric layer; or a second elastic dielectric layer is arranged on the surface of the first conductive layer, and a second conductive layer is arranged on the surface of the first elastic dielectric layer.
The elastic modulus is a measure of the resistance of an object to elastic deformation and is defined as the stress in a unidirectional stress state divided by the strain in that direction. The first elastic dielectric layer has a high elastic modulus and the second elastic dielectric layer has a low elastic modulus, i.e., the elastic modulus of the first elastic dielectric layer is higher than the elastic modulus of the second elastic dielectric layer.
Preferably, the elastic modulus of the first elastic dielectric layer is higher than that of the first conductive layer and higher than that of the second conductive layer, that is, the elastic modulus of the first elastic dielectric layer is highest among the first elastic dielectric layer, the second elastic dielectric layer, the first conductive layer, and the second conductive layer.
Preferably, the elastic modulus of the second elastic dielectric layer is lower than the elastic modulus of the first conductive layer and lower than the elastic modulus of the second conductive layer, that is, the elastic modulus of the second elastic dielectric layer is the lowest among the first elastic dielectric layer, the second elastic dielectric layer, the first conductive layer, and the second conductive layer.
The annular structure is used for limiting the flow of the dilatant fluid in a plane. In the invention, the annular structure, the first elastic dielectric layer and the second elastic dielectric layer form a closed space, and the plastic swelling fluid is packaged in the closed space, so that the plastic swelling fluid can be prevented from overflowing.
The ring structure has elasticity, and the material thereof is not limited and includes elastic polymer materials and the like. More preferably, the ring structure is one or more of thermoplastic elastomer (TPE), thermoplastic polyurethane elastomer (TPU), Polydimethylsiloxane (PDMS), aliphatic aromatic random copolyester (Ecoflex), high molecular polymer resin, silica gel, rubber, hydrogel, polyurethane, and polyethylene octene co-elastomer (POE).
The dilatant fluid is also called an dilatant fluid and is one of non-newtonian fluids. non-Newtonian fluids refer to fluids that do not conform to the laws of Newtonian motion. Dilatant fluid refers to a rheological material having a shear thickening phenomenon in which the shear stress is not linearly related to the shear strain rate, and the viscosity increases with increasing shear rate. That is, an infinitely small shear stress can cause it to start moving and the viscosity increases with increasing shear rate. Under high-speed impact, the viscosity of the material is changed greatly and even changed from a liquid phase to a solid phase; after the impact is removed, the liquid can be changed from the solid phase to the liquid phase.
The dilatant fluid material mainly comprises a main material and a solvent, wherein the main material comprises one or more of starch, honey, wet sand, D3O material and the like. Solvents include, but are not limited to, water.
The first elastic dielectric layer is not limited and includes elastic polymer material, such as one or more of gutta percha (hard natural rubber), rubber, high polymer, and high hardness polyurethane resin
The material of the second elastic dielectric layer is not limited, and includes an elastic polymer material, such as one or more of thermoplastic elastomer (TPE), thermoplastic polyurethane elastomer (TPU), Polydimethylsiloxane (PDMS), aliphatic and aromatic random copolyester (Ecoflex), polymer resin, silicone, rubber, hydrogel, polyurethane, and polyethylene octene co-elastomer (POE).
The cross-sectional shape of the ring-shaped structure is not limited, and includes regular shapes and irregular shapes, and the regular shapes include rectangles, circles, ellipses, other polygons, and the like.
The textile material layer is a fabric formed by one or more of cotton, hemp, wool, silk, wool fabric, fiber and the like.
The elastic textile material is an elastic textile material, which may be made elastic by structural design, for example, by a rib weave, or by itself.
The material of the elastic bonding layer is not limited and includes elastic polymer materials and the like. More preferably, the elastic adhesive layer is made of an elastic material having a good adhesive ability with a textile material, such as one or more of thermoplastic elastomer (TPE), thermoplastic polyurethane elastomer (TPU), Polydimethylsiloxane (PDMS), aliphatic aromatic random copolyester (Ecoflex), high molecular polymer resin, silicone rubber, hydrogel, polyurethane, and polyethylene octene co-elastomer (POE).
The conductive liquid is not limited, such as liquid metal, conductive ink, and the like.
The conductive gel is not limited, such as graphite conductive gel, silver gel, and the like.
The conductive paste is not limited and includes graphene paste, mixed paste of a conductive material and an elastomer, and the like. The mixed slurry of the conductive material and the elastomer includes, but is not limited to, a mixed slurry of a liquid metal and an elastomer, a mixed slurry of carbon powder and an elastomer, a mixed slurry of carbon fiber and an elastomer, a mixed slurry of graphene and an elastomer, a mixed slurry of a metal powder and an elastomer, and the like. Preferably, the liquid metal and the elastomer are mixed in a mass ratio of 100: (1-100) mixing to obtain slurry; the carbon powder and the elastomer are mixed according to the mass ratio of (1-100): 100 mixing into slurry; the carbon fiber and the elastomer are mixed according to the mass ratio of (1-100): 100 mixing into slurry; the graphene and the elastomer are mixed according to the mass ratio of (1-100): 100 mixing into slurry; the metal powder and the elastomer are mixed according to the mass ratio of (1-100): 100 are mixed into a slurry.
The first electrode is used for conducting and connecting an external device, and the materials of the first electrode are not limited, and include but not limited to metal materials, conductive cloth, graphene, graphite conductive adhesive, silver adhesive, liquid metal, circuit boards, polymer conductive materials and the like.
The second electrode is used for conducting and connecting with an external device, and the materials of the second electrode are not limited, and include but not limited to metal materials, conductive cloth, graphene, graphite conductive adhesive, silver adhesive, liquid metal, circuit boards, polymer conductive materials and the like.
Preferably, the first conductive layer has a thickness of less than 5mm, preferably less than 500 μm, and may even be less than 10 μm.
Preferably, the second conductive layer has a thickness of less than 5mm, preferably less than 500 μm, and may even be less than 10 μm.
Preferably, the conductive layer is connected to an electrode, and the conductive layer is in communication with an external circuit through the electrode.
Preferably, the first conductive layer is in a pattern or plane on the surface of the elastic adhesive layer. The pattern is not limited, and includes one or more patterns of straight lines, sine lines, wavy lines, sawtooth waves, triangular waves, ellipses, rings, coil shapes, heart shapes and the like, which are parallel, crossed, stacked and the like.
Preferably, the second conductive layer is patterned or planar on the surface of the elastic dielectric layer. The pattern is not limited, and includes one or more patterns of straight lines, sine lines, wavy lines, sawtooth waves, triangular waves, ellipses, rings, coil shapes, heart shapes and the like, which are parallel, crossed, stacked and the like.
Preferably, the capacitive elastic strain sensor further comprises an elastic encapsulation layer. The material of the elastic packaging layer is not limited and includes elastic polymer materials and the like. More preferably, the elastic adhesive layer is made of an elastic material having a good adhesive ability with a textile material, such as one or more of thermoplastic elastomer (TPE), thermoplastic polyurethane elastomer (TPU), Polydimethylsiloxane (PDMS), aliphatic aromatic random copolyester (Ecoflex), high molecular polymer resin, silicone rubber, hydrogel, polyurethane, and polyethylene octene co-elastomer (POE).
The invention also provides a method for preparing the capacitive elastic strain sensor, which comprises the following steps:
preparing a first elastic dielectric layer on the surface of the first conductive layer; preparing a ring-shaped structure on the surface of the first elastic dielectric layer; preparing a second elastic dielectric layer on the release film; bonding the second elastic dielectric layer with the annular structure in a hot pressing mode, wherein the first elastic dielectric layer, the second elastic dielectric layer and the annular structure form a closed structure; by means of injection, the closed structure is filled with a dilatant fluid. Or, the method comprises the following steps:
preparing a second elastic dielectric layer on the surface of the first conductive layer; preparing a ring-shaped structure on the surface of the second elastic dielectric layer; preparing a first elastic dielectric layer on the release film; bonding the first elastic dielectric layer and the annular structure in a hot pressing mode, wherein the first elastic dielectric layer, the second elastic dielectric layer and the annular structure form a closed structure; by means of injection, the closed structure is filled with a dilatant fluid.
Compared with the prior art, the elastic dielectric layer in the capacitive elastic strain sensor is designed into a three-layer laminated structure which comprises a first elastic dielectric layer with high elastic modulus, a second elastic dielectric layer with low elastic modulus and a dilatancy fluid layer arranged between the first elastic dielectric layer and the second elastic dielectric layer, and an elastic annular structure is arranged for preventing the dilatancy fluid from overflowing, and the capacitive elastic strain sensor with the structure has the following beneficial effects:
(1) improving the safety protection effect of the sensor
The elastic dielectric layer in the capacitive elastic strain sensor consists of three layers, and compared with a single-layer or double-layer elastic dielectric layer, the capacitive elastic strain sensor improves the protection effect when being subjected to external force. In particular, the present invention provides a first elastic dielectric layer having a high elastic modulus and a dilatant fluid layer in the elastic dielectric layer; the first elastic dielectric layer with high elastic modulus effectively improves the capability of resisting elastic deformation of the sensor, and can improve the safety protection effect when the sensor is impacted, flapped, collided, kneaded, extruded and the like by larger external force; the swelling plastic fluid layer effectively improves the protection of the sensor to high-speed stress, such as bullet penetration of high-speed flight, quick sword strike, high-speed slapping, impacting, colliding, kneading, extruding and the like, and when the swelling plastic fluid layer is applied to the sensor, the viscosity of the swelling plastic fluid layer is greatly changed due to the shear thickening characteristic of the swelling plastic fluid, and even the swelling plastic fluid layer is changed from a liquid phase to a solid phase, so that an effective safety protection barrier is formed to resist external force, and the damage of the external force to the sensor and the damage to a life body wearing the sensor are effectively protected.
(2) Improve the stress detection range of the sensor
When external force is applied to the sensor, the sensor deforms, so that the distance and/or the relative area between the first conducting layer and the second conducting layer are/is changed, and the capacitance is changed.
When the applied external force is large, the first elastic medium layer with high elastic modulus exists between the first conductive layer and the second conductive layer, so that the deformation quantity of the sensor is effectively reduced, particularly when the applied external force also has high speed, the viscosity of the dilatant fluid is greatly changed due to the shear thickening property of the dilatant fluid, even the viscosity of the dilatant fluid is changed from a liquid phase to a solid phase, and the deformation quantity of the sensor is further reduced, so that the actual deformation of the sensor is prevented from exceeding the detectable deformation upper limit of the sensor, namely, the detectable stress upper limit of the sensor is improved.
When the applied external force is small, the second elastic medium layer with low elastic modulus exists between the first conductive layer and the second conductive layer, so that the deformation quantity of the sensor is effectively improved, particularly when the applied external force has low speed, the plastic fluid has good fluidity due to small viscosity, can respond to small stress and has large deformation, and the deformation quantity of the sensor is further improved, so that the problem that the sensor cannot detect the stress due to small deformation caused by weak stress on the sensor is solved, the sensitivity of the sensor is improved, and the lower limit value of the detectable stress of the sensor is reduced.
Therefore, the structural design of the invention effectively widens the range of detectable stress of the capacitive elastic strain sensor, greatly improves the application range of the sensor, for example, the capacitive elastic strain sensor can be used for detecting weak stress such as pulse pulsation and the like, can be used for detecting large stress such as strong impact and the like, and can be used for detecting high-speed stress such as high-speed bullets and the like, and has very good application prospect.
Drawings
Fig. 1 is a schematic structural diagram of a capacitive elastic strain sensor in embodiment 1 of the present invention.
Fig. 2 is a schematic cross-sectional view of the ring structure of fig. 1.
The reference numerals in fig. 1 to 2 are: 1-an elastic textile material, 2-an elastic adhesive layer, 3-a first conductive layer, 4-a dilatant fluid, 5-a ring structure, 6-a second conductive layer, 7-an elastic encapsulation layer, 8-a first electrode, 9-a second electrode, 10-a first elastic dielectric layer of high elastic modulus, 11-a second elastic dielectric layer of low elastic modulus.
Detailed Description
The invention will be described in further detail below with reference to the accompanying drawings and examples, which are intended to facilitate the understanding of the invention and are not intended to limit the invention in any way.
Example 1:
the capacitive elastic strain sensor structure is shown in fig. 1 and comprises a substrate 1, an elastic bonding layer 2, a first conductive layer 3, an elastic dielectric layer, a second conductive layer 6 and an elastic packaging layer 7 from bottom to top in sequence.
The elastic adhesive layer 2 has a conductive insulating property and is located on the surface of the base.
The first conductive layer 3 is located on the surface of the elastic bonding layer 2, is formed by mixing liquid metal and polymer slurry, and is connected with the first electrode 8.
The elastic dielectric layer is located on the surface of the first conductive layer 3 and is composed of three layers stacked up and down, one layer is a first elastic dielectric layer 10 with high elastic modulus, one layer is a second elastic dielectric layer 11 with low elastic modulus, and the other layer is a dilatant fluid layer sandwiched between the first elastic dielectric layer 10 and the second elastic dielectric layer 11. The dilatant fluid layer is composed of an elastic ring structure 5 and a dilatant fluid 4 disposed inside the ring structure 5, that is, the ring structure 5, the first elastic dielectric layer 10 and the second elastic dielectric layer 11 constitute a closed space in which the dilatant fluid 4 is encapsulated.
In this embodiment, a first elastic dielectric layer 10 is disposed on the surface of the first conductive layer 3, and a second conductive layer 6 is disposed on the surface of the second elastic dielectric layer 11.
The second conductive layer 6 is located on the surface of the second elastic dielectric layer 11, is made of liquid metal and polymer mixed slurry, and is connected with the external second electrode 9. The elastic encapsulating layer 7 is used for encapsulating the first conductive layer 3 and the second conductive layer 6.
In this embodiment, the substrate 1 is made of spandex fabric, and the elastic adhesive layer 2, the ring structure 5, and the elastic encapsulating layer 7 are made of Thermoplastic Polyurethane (TPU) elastomer. The first conductive layer 3 and the second conductive layer 6 are both made of liquid metal GaInSn and TPU mixed slurry. The first electrode 8 and the second electrode 9 are copper sheets. The swelling fluid 4 is a starch solution and consists of corn starch and water, and the mass ratio of the corn starch to the water is (1.5-2): 1.
In this embodiment, the first elastic dielectric layer 10 is made of gutta percha, the second elastic dielectric layer 11 is made of thermoplastic elastomer, and the elastic modulus of the first elastic dielectric layer 10 is higher than that of the second elastic dielectric layer 11.
In this embodiment, as shown in fig. 2, the cross section of the ring structure 5 is rectangular.
In this embodiment, the thickness of the first conductive layer 3 and the second conductive layer 6 is 100 μm.
The preparation of the capacitive elastic strain sensor comprises the following steps:
forming an elastic bonding layer 2 on the elastic textile material by adopting a hot pressing process; uniformly coating the liquid metal GaInSn and TPU mixed slurry on the surface of the elastic bonding layer 2 by coating to obtain a first conductive layer 3; attaching thin copper sheets to two ends of the first conductive layer 3 to be used as first electrodes 8;
bonding the first conductive layer 3 and the first elastic dielectric layer 10 together by means of hot pressing; or coating the first elastic dielectric layer 10 in a liquid state before curing on an acrylic plate, then covering the first conductive layer 3 on the surface of the first elastic dielectric layer 10, rolling by using a roller, and then performing thermosetting adhesion;
coating hot-melt TPU on the edge of the surface of the first elastic dielectric layer 10 by adopting an injection method, and cooling to room temperature to obtain an annular structure shown in FIG. 2;
uniformly coating the release film with the mixed slurry of liquid metal GaInSn and TPU to obtain a second elastic dielectric layer 11;
bonding the second elastic dielectric layer 11 and the annular structure 5 in a hot pressing mode, and then peeling off the release film, wherein the first elastic dielectric layer 10, the second elastic dielectric layer 11 and the annular structure 5 form a sealing structure; filling a starch solution in the sealing structure in an injection mode;
adhering the second conductive layer 6 to the surface of the second elastic dielectric layer 11 by means of hot pressing; or coating the second elastic dielectric layer 11 in a liquid state before curing on the acrylic plate, then covering the second conductive layer 6 on the surface of the second elastic dielectric layer 11, and performing heat curing bonding after rolling by using a roller;
thin copper sheets are attached to both ends of the second conductive layer 6 as external second electrodes 9. And coating hot-melt TPU on the surface of the second conductive layer 6 to form an elastic packaging layer 7.
The capacitive elastic strain sensor prepared by the method not only has a stress sensing function and comfortable wearability, but also has the following excellent effects:
(1) in practical application, when the sensor is impacted by larger external force, slapped, collided, kneaded, extruded and the like, the safety protection effect can be improved due to the arrangement of the first elastic dielectric layer with high elastic modulus, and when the sensor is stressed at high speed, such as bullet piercing and rapid sword striking in high-speed flight, high-speed slapping, impacting, colliding, kneading, extruding and the like, an effective safety protection barrier can be formed due to the shear thickening characteristic of the swelling plastic fluid to resist the external force, so that the damage of the external force to the sensor and the damage to a life body wearing the sensor are effectively protected.
(2) When the sensor is acted by a large external force, the first elastic medium layer with high elastic modulus is arranged, so that the deformation quantity of the sensor is effectively reduced, particularly when the external force has high speed, such as high-speed slapping, impacting, colliding, kneading, extruding and the like, the viscosity of the swelling plastic fluid is greatly changed due to the shear thickening characteristic of the swelling plastic fluid, even the liquid phase is changed into the solid phase, and the deformation quantity of the sensor is further reduced, so that the actual deformation of the sensor can be prevented from exceeding the detectable deformation upper limit of the sensor, namely, the detectable stress upper limit of the sensor is improved.
When the sensor is subjected to weak external force, such as pulse beating and the like, the second elastic medium layer with low elastic modulus is arranged, so that the second elastic medium layer deforms greatly under the action of the external force, and particularly when the applied external force has low speed, the plastic fluid has good fluidity due to low viscosity, can respond to small stress and deforms greatly, so that the deformation quantity of the sensor is further improved, the sensitivity of the sensor is improved, and the lower limit value of the detectable stress of the sensor is reduced. Therefore, the sensor has a wide stress detection range.
Example 2:
in this embodiment, the structure of the capacitive elastic strain sensor is substantially the same as that of the capacitive elastic strain sensor in embodiment 1, except that: the dilatancy fluid is honey, and the cross section of the annular structure is round; a second elastic dielectric layer 11 is provided on the surface of the first conductive layer 3, and a second conductive layer 6 is provided on the surface of the first elastic dielectric layer 10.
In this embodiment, the method for manufacturing the capacitive elastic strain sensor is substantially the same as that in embodiment 1, except that:
adhering the second elastic dielectric layer 11 to the surface of the first conductive layer 3 by means of hot pressing; or coating the second elastic dielectric layer 11 in a liquid state before curing on an acrylic plate, then covering the first conductive layer 3 on the surface of the second elastic dielectric layer 11, rolling by using a roller, and then performing thermosetting adhesion;
coating hot-melt TPU on the edge of the surface of the second elastic dielectric layer 11 by adopting an injection method, and cooling to room temperature to obtain an annular structure;
uniformly coating the release film with the mixed slurry of liquid metal GaInSn and TPU to obtain a first elastic dielectric layer 10;
bonding the first elastic dielectric layer 10 and the annular structure 5 in a hot pressing mode, and then peeling off the release film, wherein the first elastic dielectric layer 10, the second elastic dielectric layer 11 and the annular structure 5 form a sealing structure; filling honey into the sealing structure in an injection mode;
adhering the second conductive layer 6 to the surface of the first elastic dielectric layer 11 by means of hot pressing; or coating the first elastic dielectric layer 10 in a liquid state before curing on an acrylic plate, then covering the second conductive layer 6 on the surface of the first elastic dielectric layer 10, rolling by using a roller, and then performing heat curing bonding.
The capacitive elastic strain sensor manufactured in the way of the embodiment has the stress sensing function, is comfortable and wearable, and has the safety protection function and a wide stress detection range.
Example 3:
in this embodiment, the capacitive elastic strain sensor structure is substantially the same as that of embodiment 1, except that the dilatational fluid is wet sand, and the cross section of the annular structure is elliptical; the first elastic dielectric layer 10 is made of a high hardness urethane resin, the second elastic dielectric layer 11 is made of polydimethylsiloxane, and the elastic modulus of the first elastic dielectric layer is higher than the elastic modulus of the second elastic dielectric layer 11, higher than the elastic modulus of the first conductive layer 3, and higher than the elastic modulus of the second conductive layer 6. The elastic modulus of the second elastic dielectric layer 11 is lower than that of the first elastic dielectric layer, lower than that of the first conductive layer 3, and lower than that of the second conductive layer 6.
Example 4:
in this embodiment, the capacitive elastic strain sensor structure is substantially the same as that of embodiment 1, except that the dilatant fluid is D3O material, and the cross section of the annular structure is elliptical; the first elastic dielectric layer 10 is made of high hardness silicone, the second elastic dielectric layer 11 is made of thermoplastic polyurethane elastomer, and the elastic modulus of the first elastic dielectric layer 10 is higher than that of the second elastic dielectric layer 11, higher than that of the first conductive layer 3, and higher than that of the second conductive layer 6. The elastic modulus of the second elastic dielectric layer 11 is lower than that of the first elastic dielectric layer, lower than that of the first conductive layer 3, and lower than that of the second conductive layer 6.
The above embodiments are described in detail to explain the technical solutions and advantages of the present invention, and it should be understood that the above embodiments are only specific examples of the present invention and are not intended to limit the present invention, and any modifications and improvements made within the scope of the principles of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The capacitive elastic strain sensor with high safety and high detection range sequentially comprises a substrate made of an elastic textile material, an elastic bonding layer, a first conductive layer, an elastic dielectric layer and a second conductive layer from bottom to top;
the substrate is made of elastic textile material;
the elastic bonding layer is positioned on the surface of the substrate and has conductive insulation property;
the first conducting layer is positioned on the surface of the elastic bonding layer, is composed of conducting liquid, conducting slurry or conducting gel and is connected with the first electrode;
the elastic dielectric layer is positioned on the surface of the first conductive layer and has conductive insulativity;
the second conducting layer is positioned on the surface of the elastic dielectric layer, is composed of conducting liquid, conducting slurry or conducting gel and is connected with an external second electrode;
the method is characterized in that: the elastic dielectric layer consists of three layers which are stacked up and down, wherein one layer is a first elastic dielectric layer with high elastic modulus, the other layer is a second elastic dielectric layer with low elastic modulus, and the other layer is a swelling plastic fluid layer which is clamped between the first elastic dielectric layer and the second elastic dielectric layer; the swelling plastic fluid layer is composed of an elastic annular structure and swelling plastic fluid arranged inside the annular structure.
2. A capacitive elastic strain sensor according to claim 1 wherein: a first elastic dielectric layer is arranged on the surface of the first conductive layer, and a second conductive layer is arranged on the surface of the second elastic dielectric layer;
or, a second elastic dielectric layer is arranged on the surface of the first conductive layer, and a second conductive layer is arranged on the surface of the first elastic dielectric layer.
3. A capacitive elastic strain sensor according to claim 1 wherein: among the first elastic dielectric layer, the second elastic dielectric layer, the first conductive layer and the second conductive layer, the elastic modulus of the first elastic dielectric layer is highest.
4. A capacitive elastic strain sensor according to claim 1 wherein: among the first elastic dielectric layer, the second elastic dielectric layer, the first conductive layer and the second conductive layer, the second elastic dielectric layer has the lowest elastic modulus.
5. A capacitive elastic strain sensor according to claim 1 wherein: the swelling plastic fluid material comprises a main material and a solvent, wherein the main material comprises one or more of starch, honey, wet sand and D3O material.
6. A capacitive elastic strain sensor according to claim 5 wherein: the solvent includes water.
7. A capacitive elastic strain sensor according to claim 1 wherein: the first elastic dielectric layer material comprises an elastic high polymer material;
preferably, the first elastic dielectric layer is made of one or more of hard natural rubber and high-hardness polyurethane resin.
8. A capacitive elastic strain sensor according to claim 1 wherein: the second elastic dielectric layer material comprises an elastic high polymer material.
9. A capacitive elastic strain sensor according to claim 8 wherein: the first elastic dielectric layer material is one or more of thermoplastic elastomer, thermoplastic polyurethane elastomer, polydimethylsiloxane, aliphatic aromatic random copolyester, high molecular polymer resin, silica gel, rubber, hydrogel, polyurethane and polyethylene octene co-elastomer.
10. A method of manufacturing a capacitive elastic strain sensor according to any one of claims 1 to 9, characterized by: the method comprises the following steps:
preparing a first elastic dielectric layer on the surface of the first conductive layer; preparing a ring-shaped structure on the surface of the first elastic dielectric layer; preparing a second elastic dielectric layer on the release film; bonding the second elastic dielectric layer with the annular structure in a hot pressing mode, wherein the first elastic dielectric layer, the second elastic dielectric layer and the annular structure form a closed structure; filling a swelling plastic fluid in the closed structure by means of injection;
or, the method comprises the following steps:
preparing a second elastic dielectric layer on the surface of the first conductive layer; preparing a ring-shaped structure on the surface of the second elastic dielectric layer; preparing a first elastic dielectric layer on the release film; bonding the first elastic dielectric layer and the annular structure in a hot pressing mode, wherein the first elastic dielectric layer, the second elastic dielectric layer and the annular structure form a closed structure; by means of injection, the closed structure is filled with a dilatant fluid.
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