Flexible wearable composite material with conductive stability and method of making the same

Abstract

The present application relates to the technical field of conductive stable functional materials, and particularly relates to a flexible wearable composite material with conductive stability and a preparation method thereof, which comprises a flexible substrate, conductive fillers filled in the flexible substrate, a bonding member for encapsulating the conductive fillers in the flexible substrate, and a flexible top layer; the flexible substrate is provided with a filler groove, the filler groove comprises mutually-communicating Tesla valve grooves, circular grooves and rectangular grooves, the circular grooves are three, two of the circular grooves are symmetrically arranged on one side of the rectangular groove, and the other circular groove is arranged on the other side of the rectangular groove, the Tesla valve grooves are two, and the two Tesla valve grooves are symmetrically arranged on two sides of a single circular groove, and the conductive fillers can be filled in the filler groove in a flowable manner. The flexibility of the composite material is improved through the flexible substrate and the flexible top layer, the mechanical energy absorption of the composite material is improved through the combination of the Tesla valve grooves, and the strain rate of the material is increased.

Description

Technical Field

[0001] This invention relates to the technical field of conductive and stable functional materials, specifically to a flexible wearable composite material with conductive stability and its preparation method. Background Technology

[0002] With the rise of health monitoring systems and non-invasive human-machine interfaces, flexible wearable electronic devices have attracted considerable attention. Flexible wearable electronic devices mainly consist of electronic components, wearable conductive materials, and power supplies. Among these, conductive materials play a crucial role, primarily for transmitting electrical energy and signals. In practical applications of flexible wearable electronic devices, human activity often subjects the flexible conductive materials to large deformation environments. Most wearable conductive materials reported in existing research exhibit significant conductivity changes under large deformation conditions, leading to unstable operation of the corresponding wearable electronic components and directly affecting the tracking and real-time monitoring effectiveness of flexible wearable electronic devices. Therefore, researchers have conducted in-depth research and application development based on flexible wearable composite materials with conductive stability.

[0003] Compared to traditional conductive materials such as conductive polymers, stainless steel fibers, and silver wires, flexible wearable composite materials with stable conductivity can be easily compressed, stretched, folded, and twisted into complex shapes. Simultaneously, they overcome the shortcomings of traditional conductive materials in terms of wearing comfort, feel, breathability, and flexibility. Most importantly, they address the issue of significant conductivity variations in wearable conductive materials under large deformation conditions, greatly expanding their application in wearable electronic devices. With the rapid increase in interest in novel soft devices, the requirements for flexible wearable conductive materials are becoming increasingly stringent, aiming to replace traditional conductive wearable materials. Summary of the Invention

[0004] One of the objectives of this invention is to provide a flexible wearable composite material with conductive stability. The elasticity of the composite material is improved by using a flexible substrate and a flexible top layer. The mechanical energy absorption of the composite material is improved by combining a Tesla valve groove, while the strain rate of the material is increased.

[0005] The second objective of this invention is to provide a method for preparing a flexible wearable composite material with conductive stability, which is simple and easy to adjust.

[0006] One of the solutions adopted to achieve the objective of this invention is: a flexible wearable composite material with conductive stability, comprising a flexible substrate, a conductive filler filling the flexible substrate, an adhesive for encapsulating the conductive filler in the flexible substrate, and a flexible top layer; the flexible substrate is provided with filler grooves, the filler grooves including interconnected Tesla valve grooves, circular grooves and rectangular grooves, there are three circular grooves, two of which are located on one side of the rectangular groove and are symmetrically arranged, and the other circular groove is located on the other side of the rectangular groove; there are two Tesla valve grooves, the two Tesla valve grooves are respectively located on both sides of a single circular groove and are symmetrically arranged; the conductive filler is flowably filled in the filler grooves.

[0007] The function of the Tesla valve structure is as follows: when the flexible material is deformed by external force, the eutectic gallium indium alloy enters the Tesla valve structure with difficulty, thus consuming a certain amount of energy. When the flexible material returns to its original shape, the eutectic gallium indium alloy can easily flow back into the circular and rectangular grooves.

[0008] Preferably, both the flexible substrate and the flexible top layer are polydimethylsiloxane cuboids.

[0009] Preferably, the conductive filler is a eutectic gallium-indium alloy.

[0010] Using eutectic gallium-indium alloy as a conductive filler can improve the conductivity of composite materials.

[0011] Preferably, the adhesive is a transparent tape.

[0012] Preferably, each of the Tesla valves consists of four sets of identical structural units.

[0013] Preferably, a first electrode and a second electrode are respectively provided at both ends of the rectangular groove, one end of the first electrode and the second electrode are both immersed in the conductive filler, and the other end of the first electrode and the second electrode are both used to connect electronic devices.

[0014] The second objective of this invention is achieved through a method for preparing the aforementioned flexible wearable composite material with conductive stability, comprising the following steps:

[0015] (1) Polydimethylsiloxane and polydimethylsiloxane curing agent components are mixed and stirred to obtain a mixture, which is then poured into a mold. After curing, a flexible top layer and a flexible base layer are obtained respectively. The flexible base layer is provided with a filling groove. The filling groove includes interconnected Tesla valve grooves, circular grooves and rectangular grooves. There are three circular grooves, two of which are located on one side of the rectangular groove and are symmetrically arranged, and the other circular groove is located on the other side of the rectangular groove. There are two Tesla valve grooves, which are located on both sides of a single circular groove and are symmetrically arranged.

[0016] (2) Inject the conductive filler into the filler groove of the flexible substrate;

[0017] (3) Lay an adhesive on the surface of the filling groove, and lay a flexible top layer on the surface of the adhesive to bond the flexible top layer to the flexible substrate.

[0018] Preferably, in step (1), the mass ratio of polydimethylsiloxane to polydimethylsiloxane curing agent is 10-15:1.

[0019] Preferably, step (2) further includes setting a first electrode and a second electrode at both ends of the rectangular groove, with one end of the first electrode and the second electrode immersed in the conductive filler and the other end being a free end for connecting electronic equipment.

[0020] In this invention, conductive filler is filled into the filler grooves of a flexible structural substrate in the composite material, and then encapsulated by an adhesive and a flexible top layer. When subjected to tensile deformation, the filler groove structure in the flexible substrate also deforms, causing the conductive filler in the circular grooves to flow into the Tesla valve grooves through horizontal rectangular grooves. The horizontal rectangular grooves are always filled with conductive filler, ensuring stable conductivity of the flexible wearable composite material. When subjected to external impact deformation, some conductive filler flows into the unfilled Tesla valve grooves, absorbing some of the energy generated by the external force and preventing injury to the user. Simultaneously, it prevents excessive pressure due to the conductive filler failing to flow away, which could damage the flexible substrate, thus improving the strain rate of the flexible wearable composite material.

[0021] The present invention has the following advantages and beneficial effects:

[0022] (1) From the perspective of performance optimization, the flexible wearable composite material with conductive stability of the present invention achieves stable conductivity under different deformation conditions, overcoming the problem that other conductive flexible wearable composite materials cannot have both conductive stability and good energy absorption.

[0023] (2) From the perspective of structural features, the flexible wearable composite material with conductive stability of the present invention proposes a more novel multi-channel structure compared with the traditional single structure. By storing conductive filler through three circular grooves, excess eutectic gallium gallium indium alloy can flow into the Tesla valve groove during structural deformation, thereby dissipating some of the energy.

[0024] (3) From the perspective of manufacturing cost, the composite material prepared by the method of preparing the conductive stable flexible wearable composite material of the present invention has good conductive stability and energy absorption capacity. At the same time, its simple processing method and low material cost make the cost performance of the conductive stable wearable composite material of the present invention have an order of magnitude advantage compared with other traditional wearable composite materials. Attached Figure Description

[0025] Figure 1 This is a three-dimensional view of the flexible wearable composite material with conductive stability according to Embodiment 1 of the present invention.

[0026] Figure 2 This is a schematic diagram showing the tensile force values ​​of the flexible wearable composite material with conductive stability in Embodiment 2 of the present invention.

[0027] Figure 3 This is a numerical schematic diagram of the flexible wearable composite material with conductive stability under different deformation conditions in Embodiment 3 of the present invention.

[0028] Symbol explanation:

[0029] 1—Flexible top layer, 2—Adhesive, 3—Conductive filler, 4—Flexible substrate, 5—Horizontal rectangular groove, 6—Circular groove, 7—Tesla valve groove; 8—Connecting structure. Detailed Implementation

[0030] To better understand the present invention, the following embodiments are further illustrations of the present invention, but the content of the present invention is not limited to the following embodiments.

[0031] The purpose of this invention is to provide a flexible wearable composite material with conductive stability, utilizing polydimethylsiloxane with structural channels as an elastomer to encapsulate conductive fillers. A eutectic gallium-indium alloy serves as the conductive filler, providing high conductivity. When the composite material is subjected to deformation, the eutectic gallium-indium alloy can flow well within the channels. Simultaneously, it effectively absorbs some of the external force, improving the tensile properties of the material.

[0032] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] Example 1

[0034] like Figure 1 As shown, this embodiment provides a flexible wearable composite material with conductive stability, comprising four different components: a flexible top layer 1, an adhesive 2, a conductive filler 3, and a flexible substrate 4. The flexible top layer is a standard cuboid composed of polydimethylsiloxane, used to prevent the conductive filler from leaking out. The adhesive is an adhesive material; in this embodiment, the adhesive is a transparent adhesive tape, used to connect the flexible top layer and the flexible structural substrate layer. The conductive filler is a eutectic gallium-indium alloy, filled in the filler grooves of the flexible substrate, used for conducting electricity and transmitting signals. The flexible substrate is a standard cuboid composed of polydimethylsiloxane, and the cuboid has channels consisting of two identical Tesla valve grooves 7, three circular grooves 6, one horizontal rectangular groove 5, and three connecting structures 8.

[0035] The specific preparation process of flexible wearable composite materials with electrical conductivity stability is as follows:

[0036] Step S1: Based on the form of the flexible structure base layer, process the template to obtain the mold for the flexible structure base layer structural component; specifically, this includes: using a CNC machine tool to process an acrylic sheet according to the designed drawings.

[0037] Step S2: Prepare a flexible elastomer material; the flexible elastomer material is for making flexible wearable composite materials; mix and stir polydimethylsiloxane and polydimethylsiloxane curing agent components to obtain a mixture. Specifically, this includes: mixing polydimethylsiloxane and polydimethylsiloxane curing agent at a mass ratio of 10:1, letting it stand for a period of time, placing it in a vacuum drying oven, evacuating the vacuum at room temperature, and removing the mixture after all air bubbles have been expelled to obtain the elastomer material.

[0038] Step S3: After the elastomer material is laid into the flexible substrate forming mold, vacuum heating treatment is performed to obtain the flexible substrate; specifically, this includes: after the elastomer material is evenly laid into the flexible substrate forming mold, vacuum degassing and heat curing treatment are performed. After curing, the elastomer material is removed from the flexible substrate forming mold to obtain the flexible substrate; specifically, the flexible substrate forming mold with the elastomer material laid in it is first placed in a drying oven for vacuum degassing treatment, and then heated and cured at 60°C for 2 hours. After removing it from the forming mold, the flexible substrate is obtained.

[0039] Step S4: Inject the eutectic gallium-indium alloy into the channel consisting of three circular grooves, one horizontal rectangular groove, and the connecting structure of the flexible substrate. Then, lay a layer of transparent adhesive tape on top of the channel. Finally, lay a flexible top layer made of flexible elastomer material.

[0040] Step S5: Cover the flexible substrate, which has been covered with a layer of transparent adhesive tape, with a flexible top layer. Press the flexible top layer firmly onto the flexible substrate.

[0041] Example 2

[0042] like Figure 2 As shown, the difference between the flexible wearable composite material with conductive stability provided in this embodiment and the previous embodiment is that, in step 2 of preparing the flexible wearable composite material with conductive stability, copper electrodes are added to both ends of the horizontal structure 5, namely the first electrode and the second electrode. One end of both the first electrode and the second electrode is immersed in a eutectic gallium indium alloy, and the other end of the first electrode and the second electrode are connected to various flexible wearable electronic devices for the transmission of electrical energy and signals.

[0043] In this embodiment, the tensile electromechanical properties of the flexible wearable composite material with conductive stability of the present invention are tested using an electrochemical workstation and a universal tensile testing machine, thereby specifically demonstrating the specific conductive stability properties of the present invention.

[0044] Specifically, the flexible wearable composite material with conductive stability is placed in the clamp of a universal tensile testing machine; to ensure the composite material is clamped tightly and does not fall off, the thickness of the clamp is 5% of the deformation of the sensor component; after the composite material is clamped, the first and second electrodes of the composite material are connected to the positive and negative electrodes of the electrochemical workstation respectively using wires, such as... Figure 2 As shown in the simplified diagram (b), the electrochemical workstation and the universal tensile testing machine are started simultaneously. The tensile testing machine stretches the composite material at a speed of 1 mm / min. Meanwhile, the electrochemical workstation applies a stable, fixed voltage to the composite material and records the current magnitude every 0.01 seconds. Once the composite material breaks, the tensile testing machine and the electrochemical workstation are paused. Finally, the relevant data is exported and calculated to obtain the corresponding data graph, as shown in Figure b. Figure 2 As shown in a; during the entire tensile deformation process, the rate of change of resistance ((R-R0) / R0) does not exceed 2%.

[0045] When the flexible wearable composite material with stable conductivity is stretched and deformed, all the channel structures in the flexible substrate will deform to some extent. This deformation causes the eutectic gallium indium alloy to flow into the two Tesla valve channels with space. The Tesla valve channels impede the flow of the eutectic gallium indium alloy, thus consuming some energy. When the flexible material returns to its original shape, the eutectic gallium indium alloy can easily flow back into the three circular channel channels. Throughout the entire deformation and recovery process, the horizontal rectangular channel 5 remains filled with eutectic gallium indium alloy, resulting in a very small change in the resistance of the entire flexible wearable composite material, not exceeding 2%, enabling stable transmission of electrical energy and signals.

[0046] In this embodiment, the first electrode and the second electrode are connected to other flexible wearable electronic devices, thereby achieving stable transmission of electrical energy and signals to the flexible wearable electronic devices through the high conductivity and fluidity of the eutectic gallium indium alloy.

[0047] Example 3

[0048] like Figure 3As shown, the difference between the flexible wearable composite material with conductive stability provided in this embodiment and that in Embodiment 1 is that, in step 2 of preparing the flexible wearable composite material with conductive stability, copper electrodes are added to both ends of the horizontal structure 5, which are respectively the first electrode and the second electrode. One end of both the first electrode and the second electrode is immersed in a eutectic gallium-indium alloy, and the other end of the first electrode and the second electrode are connected to various flexible wearable electronic devices for the transmission of electrical energy and signals.

[0049] In this embodiment, the flexible wearable composite material with conductive stability of the present invention is stretched, bent, twisted, and continuously pressed by both hands, thereby specifically demonstrating the specific resistance change rate of the present invention under different deformation conditions.

[0050] Specifically, the composite material of the present invention is placed on a horizontal table; then, the first and second electrodes of the composite material are connected to the positive and negative terminals of an electrochemical workstation, respectively, and the electrochemical workstation is started; simultaneously, the electrochemical workstation applies a stable fixed voltage to the composite material and records the current magnitude every 0.01 seconds. Data for stretching, bending, torsion, and continuous pressing are recorded respectively; finally, the corresponding data are exported and calculated to obtain the corresponding data graph, as shown below. Figure 3 As shown in a; throughout the entire process of stretching, bending, torsion, and continuous pressing, the rate of change of resistance ((R-R0) / R0) does not exceed 2%. Figure 3 (a) represents the energy absorption values ​​of two different composite materials of the present invention; Figure 3 (b) is a simplified schematic diagram of the connection between the composite material of the present invention and the circuit of the electrochemical workstation.

[0051] This invention utilizes a channel composed of three circular grooves 6, one horizontal rectangular groove 5, and three connecting structures 8 to fill a eutectic gallium-indium alloy. Two identical Tesla valve grooves 7 are left unfilled. The horizontal rectangular groove 5 fills with eutectic gallium-indium alloy when the composite material is subjected to various forces such as tension, bending, torsion, and continuous pressure, thus ensuring electrical stability. The Tesla valve groove 7 stores eutectic gallium-indium alloy flowing in due to external forces during deformation, preventing the composite material from cracking due to increased internal pressure caused by the eutectic gallium-indium alloy's inability to flow. Specifically, when the invention is subjected to various forces such as tension, bending, torsion, and continuous pressure, the composite material deforms, causing the eutectic gallium-indium alloy to flow with difficulty into the Tesla valve groove 7, consuming some energy and acting as a buffer to absorb energy, while simultaneously increasing the strain rate of the composite material. The horizontal rectangular groove 5 remains filled with eutectic gallium-indium alloy, maintaining a stable resistivity of the composite material; throughout the entire deformation process, the resistivity of the composite material does not exceed 2%.

[0052] The above description is merely a preferred embodiment of the present invention, and should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A flexible wearable composite material with electrical conductivity stability, characterized in that: The invention includes a flexible substrate, conductive filler filling the flexible substrate, an adhesive for encapsulating the conductive filler in the flexible substrate, and a flexible top layer. The flexible substrate has a filler groove, which includes interconnected Tesla valve grooves, circular grooves, and rectangular grooves. There are three circular grooves, two of which are located on one side of the rectangular groove and symmetrically arranged, and the other circular groove is located on the other side of the rectangular groove. There are two Tesla valve grooves, each located on one side of a single circular groove and symmetrically arranged. The conductive filler is flowably filled within the filler groove.

2. The flexible wearable composite material with conductive stability according to claim 1, characterized in that: Both the flexible substrate and the flexible top layer are polydimethylsiloxane cuboids.

3. The flexible wearable composite material with conductive stability according to claim 1, characterized in that: The conductive filler is a eutectic gallium-indium alloy.

4. The flexible wearable composite material with conductive stability according to claim 1, characterized in that: The adhesive is a transparent tape.

5. The flexible wearable composite material with conductive stability according to claim 1, characterized in that: Each of the Tesla valves consists of four identical structural units.

6. The flexible wearable composite material with conductive stability according to claim 1, characterized in that: A first electrode and a second electrode are respectively disposed at both ends of the rectangular groove. One end of the first electrode and the second electrode are both immersed in the conductive filler, and the other end of the first electrode and the second electrode are both used to connect electronic devices.

7. A method for preparing a flexible wearable composite material with conductive stability as described in any one of claims 1-6, characterized in that, Includes the following steps: (1) Polydimethylsiloxane and polydimethylsiloxane curing agent components are mixed and stirred to obtain a mixture, which is then poured into a mold. After curing, a flexible top layer and a flexible base layer are obtained respectively. The flexible base layer is provided with a filling groove. The filling groove includes interconnected Tesla valve grooves, circular grooves and rectangular grooves. There are three circular grooves, two of which are located on one side of the rectangular groove and are symmetrically arranged, and the other circular groove is located on the other side of the rectangular groove. There are two Tesla valve grooves, which are located on both sides of a single circular groove and are symmetrically arranged. (2) Inject the conductive filler into the filler groove of the flexible substrate; (3) Lay an adhesive on the surface of the filling groove, and lay a flexible top layer on the surface of the adhesive to bond the flexible top layer to the flexible substrate.

8. The method for preparing the flexible wearable composite material with conductive stability according to claim 7, characterized in that: In step (1), the mass ratio of polydimethylsiloxane to polydimethylsiloxane curing agent is 10-15:

1.

9. The method for preparing the flexible wearable composite material with conductive stability according to claim 7, characterized in that: In step (2), a first electrode and a second electrode are respectively set at both ends of the rectangular groove. One end of the first electrode and the second electrode are both immersed in the conductive filler, and the other end is a free end for connecting electronic equipment.

Images