Stretchable Multi-Core Conductive Element, Preparation Method Thereof, Stretchable Cable, and Stretchable Capacitive Sensor

Abstract

The present invention provides a stretchable multi-core conductive element, which includes two or more stretchable wires. The stretchable wires are insulated from each other and twisted together along the length direction. Each stretchable wire includes a liquid metal and a first elastic insulating layer coated on the periphery of the liquid metal. This stretchable multi-core conductive element has a simple structure and is easy to fabricate. It has high conductivity and high stretchability, and can be used as a stretchable cable and a stretchable capacitive sensor, having good application prospects.

Description

Technical Field

[0001] The present invention relates to the field of flexible electronics, and particularly to a stretchable multi-core conductive element, a preparation method thereof, a stretchable cable, and a stretchable capacitive sensor. Background Art

[0002] With the development of the Internet of Things and wearable technologies, flexible and stretchable devices are the mainstream trend of future electronic device development. Among them, elastic wires and elastic sensors are key units in the development of flexible devices, and have received extensive attention in recent years. In particular, multi-core cables for signal transmission and sensors for signal collection are very important for the miniaturization, portability, and comfort of electronic products.

[0003] Currently, elastic wires are mainly prepared in two ways. One is to wind multiple copper wires into a spiral structure. When stretched, the spiral structure is straightened, thus maintaining the continuity of conductivity. However, this spiral structure occupies a relatively large space, which is not conducive to the integration and miniaturization of devices. Moreover, the stiffness of copper wires is relatively large, resulting in a relatively strong foreign body sensation during wearing. The other is to weave conductive fiber wires into a fabric with stretching characteristics. However, this material has poor conductivity, poor stability, is not corrosion-resistant, and is not washable.

[0004] Elastic sensors mainly have two structures: resistive and capacitive. The resistive type is usually composed of a composite of a conductive nanomaterial and an elastomeric material. When stretched, the conductive path of the conductive particles changes, thus the resistance changes. The capacitive sensor generally has a sandwich structure composed of an electrode layer, a dielectric layer, and an electrode layer. When stretched, the thickness of the dielectric layer becomes smaller and the area of the electrode layer becomes larger, thus the capacitance increases. Although these two types of sensors have good responses to tensile deformation, they also have responses when subjected to bending deformation. Therefore, when the sensor is applied in an environment with both bending deformation and tensile deformation, the sensor cannot obtain accurate tensile changes, that is, the signal of tensile strain will be interfered by bending deformation. Summary of the Invention

[0005] In view of the above technical status quo, the present invention provides a stretchable multi-core conductive element with a simple structure, high conductivity, and high elasticity.

[0006] The technical solution provided by the present invention is: a stretchable multi-core conductive element, characterized in that it includes two or more stretchable wires, the stretchable wires are insulated from each other, and are arranged in parallel or stranded together along the length direction;

[0007] Each stretchable wire includes a central conductor and a first elastic insulating layer coated on the periphery of the central conductor, and the central conductor is a liquid metal.

[0008] The stranding means that along the length direction, each stretchable wire is twisted and wound together. Preferably, after twisting, each stretchable wire has an axially symmetric undulating structure.

[0009] Preferably, a second elastic insulating layer is coated on the periphery of the stretchable wires stranded together as an elastic protective layer. More preferably, an elastic conductive material is coated on the periphery of the stretchable wires stranded together as an elastic shielding layer, and a second elastic insulating layer is coated outside the elastic shielding layer as an elastic protective layer.

[0010] The first elastic insulating layer and the second elastic insulating layer are both made of elastomers. The elastomer refers to a non-conductive material that can be deformed under an external force and has a certain deformation recovery ability after the external force is removed, including but not limited to elastic fabrics, latex, silica gel, polyurethane (PU), polylactic acid (PLA), hydrogenated styrene-butadiene block copolymer (SEBS), polydimethylsiloxane (PDMS), polyethylene oxide (POE), aliphatic-aromatic random copolyester (Ecoflex), natural rubber, synthetic rubber and other elastic materials, or one or more of composite materials doped with carbon black, silica, carbon nanotubes, silver nanowires, silver-coated nickel particles and other materials based on them.

[0011] The materials of the first elastic insulating layer and the second elastic insulating layer can be the same or different.

[0012] The liquid metal refers to a metal material that is liquid at room temperature, including but not limited to mercury, gallium-indium alloy, gallium-indium-tin alloy, or a gallium-indium alloy or gallium-indium-tin alloy doped with one or several transition metal elements and solid non-metal elements.

[0013] The elastic shielding layer refers to an elastic conductive material with a certain electric field shielding effect, including but not limited to one or more of conductive fabrics, metal nanomaterials, graphene, carbon nanotubes, graphite, liquid metals, conductive adhesives, conductive gels, conductive silver pastes and other materials, and composite materials formed by one or more of them and elastic materials such as latex, silica gel, polyurethane (PU), polylactic acid (PLA), hydrogenated styrene-butadiene block copolymer (SEBS), polydimethylsiloxane (PDMS), polyethylene oxide (POE), aliphatic-aromatic random copolyester (Ecoflex), natural rubber, synthetic rubber. Metal nanomaterials include but not limited to gold, silver, copper, aluminum, zinc, etc. Conductive fabrics include but not limited to conductive materials woven from silver wires, copper wires, conductive fibers, etc.

[0014] The preparation method of the stretchable multi-core cable of the present invention can be as follows:

[0015] (1) Fill the first liquid metal into an elastic tube to form a stretchable wire;

[0016] (2) Arrange two or more stretchable wires side by side along the length direction or twist them together.

[0017] Preferably, it further includes the following step (3):

[0018] (3) Wrap the periphery of the stretchable wire twisted in step (2) with an elastic conductive material as a shielding layer, and wrap a second elastic insulating layer around the shielding layer as a protective layer.

[0019] The elastic tube refers to a non-conductive tubular material that can be deformed under an external force and has a certain deformation recovery ability after the external force is removed, including but not limited to latex, silica gel, polyurethane (PU), polylactic acid (PLA), hydrogenated styrene-butadiene block copolymer (SEBS), polydimethylsiloxane (PDMS), polyethylene oxide (POE), aliphatic aromatic random copolyester (Ecoflex), natural rubber, synthetic rubber and other elastic materials or a tubular structure composed of one or more of composite materials such as carbon black, silica white, carbon nanotubes, silver nanowires, silver-coated nickel particles doped on their bases. Preferably, the elastic tube is made of a silica gel tube.

[0020] In step (1), the method of filling the first liquid metal into the elastic tube is not limited, including one or more of injection, vacuum / negative pressure suction, 3D printing, extrusion and other methods. Preferably, the injection method is adopted.

[0021] In step (3), the coating method is not limited, including one or more of knitting, scraping, coating, extrusion, spraying, hot pressing and other methods. Preferably, the coating is realized by knitting.

[0022] The present invention uses a stretchable wire composed of a liquid metal and an elastic insulating layer coated around the liquid metal, and twists two or more stretchable wires together along the length direction to form a stretchable multi-core conductive element, which has the following advantages:

[0023] (1) The liquid metal has excellent electrical conductivity, and its electrical conductivity reaches 2×10 6 S / m; at the same time, the liquid metal has excellent "flexibility" and will not limit the stretching performance of the elastic body as a conductor. Therefore, the wire element of the present invention has both high electrical conductivity and high stretchability, and its electrical conductivity can reach 3.4×10 6 S / m, and the stretching ratio can be as high as 3200%.

[0024] (2) The wire element of the present invention can be used as a multi-core cable. At this time, both ends of each stretchable wire are connected to the circuit for transmitting electrical signals, having high electrical conductivity, high stretchability and high stability. Especially when the stretchable wires are twisted together, it has electromagnetic interference resistance and anti-bending performance, and makes the cable rounder and more beautiful in appearance.

[0025] (3) The wire element of the present invention is used as a capacitive sensor. At this time, the liquid metal in two adjacent stretchable wires serves as the electrode layer, and the elastic insulating layer between the liquid metals serves as the dielectric layer. The positive electrode of the circuit is electrically connected to the liquid metal in one stretchable wire, and the negative electrode of the circuit is electrically connected to the liquid metal in the other stretchable wire. Especially when these two stretchable wires are intertwined to form a twisted pair structure, when the sensor undergoes bending deformation, the local capacitance between the two electrode layers alternately increases and decreases, and the overall capacitance change values cancel each other out. That is, the capacitive sensor with this structure is not sensitive to bending strain, avoiding the problem that the signal of tensile strain is interfered by bending deformation.

[0026] (4) The structure of the present invention is simple and easy to manufacture. The outer insulating layer and shielding layer help to protect the electronic components and facilitate connection and integration with other circuits. Description of the Drawings

[0027] Figure 1 is a cross-sectional structural schematic diagram of the stretchable two-core conductive element in Embodiment 1 of the present invention;

[0028] Figure 2 is a sectional view of the stretchable two-core conductive element in the length direction in Embodiment 1 of the present invention;

[0029] Figure 3 is a cross-sectional structural schematic diagram of the stretchable two-core conductive element in Embodiment 2 of the present invention;

[0030] Figure 4 is a sectional view of the stretchable two-core conductive element in the length direction in Embodiment 2 of the present invention;

[0031] Figure 5 is a cross-sectional structural schematic diagram of the stretchable two-core conductive element in Embodiment 3 of the present invention;

[0032] Figure 6 is a sectional view of the stretchable two-core conductive element in the length direction in Embodiment 3 of the present invention;

[0033] Figure 7 is a cross-sectional structural schematic diagram of the stretchable two-core conductive element in Embodiment 4 of the present invention;

[0034] Figure 8 is a sectional view of the stretchable two-core conductive element in the length direction in Embodiment 4 of the present invention;

[0035] Figure 9 is a schematic diagram of the cross-sectional structure of a stretchable two-core conductive element in Example 5 of the present invention;

[0036] Figure 10 is a schematic cross-sectional view of a stretchable two-core conductive element in the length direction of Example 5 of the present invention;

[0037] Among them, the reference numerals are: 1 liquid metal, 2 elastic tube, 3 elastic tube, 4 elastic shielding layer, 5 elastic protective layer. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be pointed out that the embodiments described below are intended to facilitate the understanding of the present invention and do not have any limiting effect on the present invention.

[0039] Embodiment 1:

[0040] In this embodiment, Figure 1 , 2 As shown, liquid metal 1 is respectively filled in elastic tube 2 and elastic tube 3 to form two stretchable conductors, and along the length direction, the two stretchable conductors are intertwined and wound to form a stretchable multi-core conductive element with a twisted pair structure. Among them, the liquid metal is GaInSn alloy, and the elastic tube 2 and the elastic tube 3 are both made of thermoplastic elastic material SEBS.

[0041] The preparation method of the stretchable multi-core conductive element is as follows:

[0042] An extruder is used, and an extrusion die is used. The extrusion die is two hollow tubes with double needles connected on the outside. The SEBS elastic tube is directly extruded by the die; then liquid metal is directly injected into the tube; then the two wires are pulled by an external winding device to wind them together to form a Figure 2 The stretchable twisted pair structure shown.

[0043] The stretchable multi-core conductive element can be used as a multi-core cable. At this time, both ends of each stretchable wire are connected to the circuit for transmitting electrical signals. It has the advantages of high conductivity, high stretchability, and strong resistance to electromagnetic interference and bending.

[0044] The stretchable multi-core conductive element can be used as a capacitive sensor, in which the liquid metal in one stretchable wire serves as an electrode layer, the elastic tube between the liquid metals serves as a dielectric layer, the positive electrode of the circuit is electrically connected to the liquid metal in one stretchable wire, and the negative electrode of the circuit is electrically connected to the liquid metal in another stretchable wire. The sensor structure is sensitive to stretching deformation, but not to bending deformation.

[0045] Embodiment 2:

[0046] In this embodiment, Figure 3 , 4 As shown, liquid metal 1 is respectively filled in elastic tube 2 and elastic tube 3 to form two stretchable conductors. Along the length direction, the two stretchable conductors are intertwined and twisted together to form a twisted pair structure, and the outer periphery is covered with an elastic protective layer 5 to obtain a stretchable multi-core conductive element.

[0047] The liquid metal is made of GaInSn alloy, the elastic tube 2 and the elastic tube 3 are both made of SEBS, a thermoplastic elastic material, and the elastic protective layer 5 is made of polyester fiber filaments woven into an elastic structure.

[0048] The preparation method of the stretchable multi-core conductive element is as follows:

[0049] An extruder device and an extrusion die are used. The extrusion die is two hollow tubes with double needles connected on the outside. The SEBS elastic tube is directly extruded by using the die; then liquid metal is directly injected into the tube; then the two wires are pulled by an external winding device to wrap them around each other to form a stretchable twisted pair structure; finally, the elastic protective layer 5 is wrapped around the outer periphery of the twisted pair structure by weaving polyester fiber yarns into an elastic structure.

[0050] The stretchable multi-core conductive element can be used as a multi-core cable. At this time, both ends of each stretchable wire are connected to the circuit for transmitting electrical signals. It has the advantages of high conductivity, high stretchability, and strong resistance to electromagnetic interference and bending.

[0051] The stretchable multi-core conductive element can be used as a capacitive sensor, in which the liquid metal in one stretchable wire serves as an electrode layer, the elastic tube between the liquid metals serves as a dielectric layer, the positive electrode of the circuit is electrically connected to the liquid metal in one stretchable wire, and the negative electrode of the circuit is electrically connected to the liquid metal in another stretchable wire. The sensor structure is sensitive to stretching deformation, but not to bending deformation.

[0052] Embodiment 3:

[0053] In this embodiment, Figure 5 , 6 As shown, liquid metal 1 is respectively filled in the elastic tube 2 and the elastic tube 3 to form two stretchable conductors. Along the length direction, the two stretchable conductors are intertwined and twisted together to form a twisted pair structure, the outer periphery of which is covered with an elastic shielding layer 4, and the outer periphery of the shielding layer 4 is covered with an elastic protective layer 5 to obtain a stretchable multi-core conductive element.

[0054] The liquid metal is made of GaInSn alloy, the elastic tube 2 and the elastic tube 3 are both made of SEBS, a thermoplastic elastic material, the elastic shielding layer 4 is made of GaInSn alloy, and the elastic protective layer 5 is made of SEBS, a thermoplastic elastic material.

[0055] The preparation method of the stretchable multi-core conductive element is as follows:

[0056] An extruder device and an extrusion die are used. The extrusion die is two hollow tubes with double needles connected on the outside. The SEBS elastic tube is directly extruded by the die. Then liquid metal is directly injected into the tube. After that, the two wires are pulled by an external winding device to wrap them around each other to form a stretchable twisted pair structure. A liquid metal screen is coated on the outer periphery of the twisted pair structure, and finally an elastic protective layer 5 is coated.

[0057] The stretchable multi-core conductive element can be used as a multi-core cable. At this time, both ends of each stretchable wire are connected to the circuit for transmitting electrical signals. It has the advantages of high conductivity, high stretchability, and strong resistance to electromagnetic interference and bending.

[0058] The stretchable multi-core conductive element can be used as a capacitive sensor, in which the liquid metal in one stretchable wire serves as an electrode layer, the elastic tube between the liquid metals serves as a dielectric layer, the positive electrode of the circuit is electrically connected to the liquid metal in one stretchable wire, and the negative electrode of the circuit is electrically connected to the liquid metal in another stretchable wire. The sensor structure is sensitive to stretching deformation, but not to bending deformation.

[0059] Embodiment 4:

[0060] In this embodiment, Figure 7 , 8 As shown, liquid metal 1 is respectively filled in the elastic tube 2 and the elastic tube 3 to form two stretchable conductors. Along the length direction, the two stretchable conductors are arranged in parallel and in contact with each other to form a parallel line structure, and the outer periphery of the elastic shielding layer 4 is covered with an elastic protective layer 5, thereby obtaining a stretchable multi-core conductive element.

[0061] The liquid metal is made of GaInSn alloy, the elastic tube 2 and the elastic tube 3 are both made of SEBS, a thermoplastic elastic material, the elastic shielding layer 4 is made of GaInSn alloy, and the elastic protective layer 5 is made of SEBS, a thermoplastic elastic material.

[0062] The preparation method of the stretchable multi-core conductive element is as follows:

[0063] Using an extruder device and an extrusion die, the extrusion die is two hollow tubes sleeved outside side-by-side double needles, and the SEBS elastic tube is directly extruded using this die; then liquid metal is directly injected into the tube; afterwards, through the traction of external equipment, two wires are arranged in parallel in contact with each other along the length direction to form a parallel line structure; a liquid metal screen is coated on the periphery of the parallel line structure, and finally an elastic protective layer 5 is coated in a coating manner.

[0064] This stretchable multi-core conductive element can be used as a multi-core cable. At this time, both ends of each stretchable wire are connected to the circuit for transmitting electrical signals, and it has the advantages of high electrical conductivity, high stretchability, and electromagnetic interference resistance.

[0065] This stretchable multi-core conductive element can be used as a capacitive sensor. At this time, the liquid metal in one stretchable wire serves as the electrode layer, and the elastic tube between the liquid metals serves as the dielectric layer. The positive electrode of the circuit is electrically connected to the liquid metal in one stretchable wire, and the negative electrode of the circuit is electrically connected to the liquid metal in the other stretchable wire.

[0066] Example 5:

[0067] In this embodiment, as Figure 9 、 10 shown, liquid metal 1 is respectively filled in elastic tube 2 and elastic tube 3 to form two stretchable wires, and these two stretchable wires are intertwined with each other to form a twisted pair structure. Two such twisted pair structures are arranged in parallel along the length direction as the core layer, and an elastic shielding layer 4 is coated on the periphery of the core layer, and an elastic protective layer 5 is coated on the periphery of the elastic shielding layer 4 to obtain a stretchable multi-core conductive element.

[0068] Among them, the liquid metal is selected as GaInSn alloy, both elastic tube 2 and elastic tube 3 are made of the thermoplastic elastomer material SEBS, the elastic shielding layer 4 is made of GaInSn alloy, and the elastic protective layer 5 is made of the thermoplastic elastomer material SEBS.

[0069] The preparation method of this stretchable multi-core conductive element is as follows:

[0070] Using an extruder device and an extrusion die, the extrusion die is two hollow tubes sleeved outside side-by-side double needles, and the SEBS elastic tube is directly extruded using this die; then liquid metal is directly injected into the tube; afterwards, through the traction of external winding equipment, two wires are wound around each other to form a stretchable twisted pair structure as Figure 2 shown. Two such twisted pair structures are arranged in parallel along the length direction as the core layer, a liquid metal screen is coated on the periphery of the core layer, and finally an elastic protective layer 5 is coated in a coating manner.

[0071] The stretchable multi-core conductive element can be used as a multi-core cable. In this case, both ends of each stretchable wire are connected to a circuit for transmitting electrical signals, and it has the advantages of high electrical conductivity, high stretchability, and strong anti-electromagnetic interference and anti-bending performance.

[0072] The stretchable multi-core conductive element can be used as a capacitive sensor. In this case, the liquid metal in one stretchable wire serves as the electrode layer, and the elastic tube located between the liquid metals serves as the dielectric layer. The positive electrode of the circuit is electrically connected to the liquid metal in one stretchable wire, and the negative electrode of the circuit is electrically connected to the liquid metal in another stretchable wire. This sensor structure is sensitive to tensile deformation but insensitive to bending deformation.

[0073] The above-described embodiments have detailed the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications and improvements made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A stretchable capacitive sensor insensitive to bending strain, Characterized in that: It includes a stretchable multi-core conductive element, and the stretchable multi-core conductive element includes two stretchable wires, and the stretchable wires are insulated from each other and are intertwined along the length direction to form a twisted pair structure; Each stretchable wire includes a central conductor and a first elastic insulating layer coated on the periphery of the central conductor, and the central conductor is liquid metal; The positive electrode of the circuit is electrically connected to the liquid metal in one stretchable wire, and the negative electrode of the circuit is electrically connected to the liquid metal in the other stretchable wire.

2. The stretchable capacitive sensor according to claim 1, Characterized in that: A second elastic insulating layer is coated on the periphery of the stretchable wire as an elastic protective layer.

3. The stretchable capacitive sensor according to claim 2, Characterized in that: An elastic conductive material is coated on the periphery of the stretchable wire as an elastic shielding layer, and a second elastic insulating layer is coated on the outside of the elastic shielding layer as an elastic protective layer.

4. The stretchable capacitive sensor according to claim 1 or 2, Characterized in that: The first elastic insulating layer and the second elastic insulating layer are respectively composed of elastomers; The elastomers include one or more of elastic fabric, latex, silica gel, polyurethane, polylactic acid, hydrogenated styrene-butadiene block copolymer, polydimethylsiloxane, polyethylene oxide, aliphatic aromatic random copolyester, natural rubber, synthetic rubber, and composites doped with one or more of carbon black, white carbon black, carbon nanotubes, silver nanowires, silver-coated nickel particles based on them.

5. The stretchable capacitive sensor according to claim 3, Characterized in that: The elastic shielding layer material includes one or more of elastic conductive fabric, metal nanomaterials, graphene, carbon nanotubes, graphite, liquid metal, conductive glue, conductive gel, conductive silver paste, and composites formed by one or more of them and elastic materials.

6. A preparation method of the stretchable capacitive sensor according to any one of claims 1 to 5, Characterized in that: It includes the following steps: (1) Filling the first liquid metal into an elastic tube to form a stretchable wire; (2) Intertwining two stretchable wires along the length direction to form a twisted pair structure.

7. The preparation method of the stretchable capacitive sensor according to claim 6, Characterized in that: It also includes The following steps: (3) Coating an elastic shielding layer on the periphery of the stretchable wire after being intertwined in step (2), and coating an elastic protective layer on the outside of the elastic shielding layer.

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