A fast response heat-driven spiral-wound artificial muscle

Abstract

A fast-response, heat-driven, spirally wound artificial muscle is disclosed. The artificial muscle is composed of spirally wound artificial muscle fibers, which have a three-layer structure: a supporting sensing layer, a heat insulation layer, and a driving layer, from the inside out. The driving layer is connected to an external circuit, which heats the driving layer to achieve contraction movement of the artificial muscle. The heat insulation layer prevents heat transfer to the supporting sensing layer, enabling rapid temperature changes in the driving layer. The supporting sensing layer supports the artificial muscle fibers and also functions as a sensing layer. The muscle fibers of this invention are composed of inner, middle, and outer layers, which respectively serve the functions of supporting sensing, heat insulation, and driving. This minimizes the heat transfer from the driving layer to the interior of the material, reducing energy waste and ensuring rapid heat dissipation from the outer layer, thereby improving the response frequency of the artificial muscle.

Description

Technical Field

[0001] This invention relates to the field of artificial muscle technology, and more particularly to a fast-response, heat-driven, spiral-wound artificial muscle. Background Technology

[0002] As a flexible actuator, artificial muscles can convert external energy into mechanical energy. They have attracted widespread attention due to their low noise, long stroke, and better biocompatibility, and have broad and enormous application potential in devices such as exoskeletons, prostheses, and biomimetic robots. Currently, many functional materials have been used as artificial muscles, such as pneumatic porous materials, shape memory alloys (SMA), shape memory polymers (SMP), nylon fibers, dielectric elastomers (DEA), ionomer-metal composites (IPMC), carbon nanotubes (CNT), and magnetorheological fluids. According to the driving principle, common artificial muscles are mainly divided into five categories: pneumatic response, temperature response, chemical response, electrical response, and magnetic response. Among them, temperature-responsive, i.e., thermally driven artificial muscles, are the most common type.

[0003] One important type of thermodynamically driven artificial muscle is the helical coil type. Helical coil artificial muscles are typically driven by heating (electrochemical, photonic, thermal, or electrothermal) contraction, exhibiting excellent torsional and tensile actuation performance. Their maximum contraction rate can generally reach 40-50%, and they possess high energy density. Electrothermally driven helical coil artificial muscles are widely used due to their ease of operation and control.

[0004] Typically, thermally driven helical coiled artificial muscles contract when electrically heated and expand when power is cut off; both heating and cooling processes affect the actuation frequency. The heating process can be shortened by increasing the input power, while the cooling process is largely uncontrollable in ambient air. Therefore, the actuation frequency of electrothermally driven artificial muscles tends to be low, generally below 3Hz, and is primarily limited by cooling time, restricting their application as fast-response actuators. One way to improve the heat dissipation rate is to improve the heat dissipation conditions, such as forced air cooling or water cooling, but this usually requires higher energy consumption.

[0005] To solve this problem, we must begin by analyzing the specific driving principle of helical wound artificial muscles. In helical wound artificial muscles, the yarn constituting the muscle is made of twisted fibers such as nylon. The wound yarn expands in volume when heated, causing untwisting, which in turn leads to muscle contraction. From a structural perspective, the ability of fiber expansion to drive yarn untwisting increases with the yarn offset angle (the angle between the yarn axis and the fiber axis). Since the offset angle gradually decreases from the yarn surface to the center, the portion closer to the yarn center contributes less to the driving force, resulting in lower energy utilization efficiency. Furthermore, in electrothermal helical wound artificial muscles, the internal structure cannot effectively exchange heat with the external environment, making it more difficult to lower the temperature. This is one of the reasons for the low driving frequency of electrothermal driven artificial muscles.

[0006] The above analysis shows that if we want to effectively improve the response frequency and energy utilization of spiral-wound artificial muscles, we can improve their design by utilizing their structural characteristics.

[0007] CN112201744A discloses the preparation and application of an electrostrictive helical coiled artificial muscle. The muscle fiber in this invention consists of a sheath and a core. The sheath is made of a carbon nanotube film, and the core is made of nylon thread. The entire muscle contracts by heating the sheath with an electric current. Although carbon nanotubes are excellent thermally driven materials with good electrical conductivity and mechanical properties, their high cost makes the manufactured artificial muscle very expensive, hindering large-scale commercial applications. Furthermore, because the sheath and core of the muscle fiber are in direct contact, heat can be fully transferred to the core during heating. However, during heat dissipation, the poor radial heat dissipation capacity of the external carbon nanotubes prevents rapid heat dissipation, creating a relatively high-temperature zone inside the muscle fiber. This hinders the rapid cooling of the carbon nanotubes and negatively impacts the increase in the driving frequency of the manufactured artificial muscle.

[0008] CN115142267A discloses a method for preparing a bidirectionally driven biomimetic muscle fiber. The fiber comprises a substrate material encapsulated by a guest material, and the muscle fiber is then wound into a spiral shape to ultimately achieve its driving function. The driving principle of this invention is achieved by energizing the electrothermal fibers of the substrate inside the artificial muscle fiber. Summary of the Invention

[0009] To address the issue of low response frequency in helical coiled artificial muscles, this invention designs a fast-response, heat-driven helical coiled artificial muscle. By improving the structure of the helical coiled artificial muscle fibers, it achieves better heat dissipation compared to traditional coiled artificial muscles, thereby enabling higher-frequency actuation.

[0010] The technical solution adopted in this invention is: a fast-response, heat-driven, spirally wound artificial muscle, wherein the artificial muscle is formed by twisting and spirally winding artificial muscle fibers. The artificial muscle fibers have a three-layer structure, consisting of a support sensing layer, a heat insulation layer, and a driving layer from the inside out. The driving layer is connected to an external circuit, which heats the driving layer to achieve the contraction movement of the artificial muscle. The heat insulation layer prevents heat from being transferred to the support sensing layer, thereby achieving rapid temperature changes in the driving layer. The support sensing layer supports the artificial muscle fibers and also functions as a sensing layer.

[0011] Furthermore, the cross-section of the artificial muscle fiber is a three-layer concentric circle structure, consisting of a circular support sensing layer, an annular heat insulation layer, and an annular driving layer from the inside out.

[0012] Furthermore, the driving layer is made of silver-plated nylon film.

[0013] Furthermore, the heat insulation layer is made of polyimide film.

[0014] Furthermore, the supporting sensing layer is made of shape memory alloy wire or Kevlar fiber.

[0015] Furthermore, the total thickness of the artificial muscle fibers is between 20 and 200 μm.

[0016] Furthermore, the thickness of the driving layer is 4-40 μm.

[0017] Furthermore, the thickness of the heat insulation layer is 1-10 μm.

[0018] Furthermore, the thickness of the sensing support layer is 10-120 μm.

[0019] Furthermore, the thickness of the support layer is greater than the thickness of the driving layer.

[0020] The beneficial effects of this invention are:

[0021] (1) The present invention uses a heat-driven spiral wound artificial muscle, which has a simple driving principle, low noise and low impact.

[0022] (2) The muscle fiber designed in this invention is composed of three layers of material: inner, middle and outer, which respectively play the roles of supporting sensing, heat insulation and driving. This makes the heat of the driving layer conduct to the interior of the material as little as possible, reducing energy waste and ensuring the rapid dissipation of heat in the outer layer, thereby improving the response frequency of the artificial muscle.

[0023] (3) The internal support and sensing layer of the artificial muscle unit designed in this invention can achieve both support and sensing functions by selecting appropriate materials such as shape memory alloy wires, so that the artificial muscle fibers formed have a higher degree of integration and save space.

[0024] (4) The artificial muscle fiber designed in this invention is composed of three layers of materials, thus offering greater freedom in the selection of materials and thicknesses for each layer. Appropriate materials and thicknesses can be chosen based on specific working conditions. Specifically, for example, the outer layer can be made of nylon, which, compared to other thermally responsive materials, provides advantages such as high energy density, low displacement hysteresis, and good cycle performance. It can be electrically heated by plating its surface with metals such as silver. Furthermore, nylon has a significant price advantage over materials such as carbon nanotubes used in other patents, which helps reduce the overall cost of the artificial muscle.

[0025] (5) The designed artificial muscles can work alone or multiple muscles can be used in parallel or in series to achieve greater force or deformation. Attached Figure Description

[0026] Figure 1 This is a cross-sectional schematic diagram of the fiber of the present invention.

[0027] Figure 2 This is a schematic diagram of the fiber spiral winding of the present invention.

[0028] Figure 3 This is a schematic diagram of the present invention during heat shrinkage.

[0029] Figure 4 This is the vision of the proposed coiled artificial muscle-driven mechanical finger applied in Embodiment 1 of the present invention. Figure 1 .

[0030] Figure 5 This is the vision of the coiled artificial muscle-driven mechanical finger proposed in Embodiment 1 of the present invention. Figure 2 .

[0031] Figure 6 This is a schematic diagram of the parallel application of the proposed coiled artificial muscle as presented in Embodiment 2 of the present invention.

[0032] Explanation of reference numerals in the attached figures: 1-driving layer, 2-insulation layer, 3-supporting sensing layer, 4-finger tip of the mechanical finger, 5-proposed coiled artificial muscle 1, 6-middle of the mechanical finger, 7-proposed coiled artificial muscle 2, 8-root of the mechanical finger. Detailed Implementation

[0033] The technical solution of this invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0034] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0035] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0036] Example 1

[0037] See attached document Figure 1 and attached Figure 2 As can be seen, a fast-response, heat-driven, spirally wound artificial muscle is formed by winding artificial muscle fibers. The artificial muscle fibers designed in this invention are a three-layer composite structure composed of three materials, and the cross-section of the muscle fibers is as shown in the attached figure. Figure 1 The concentric circle structure shown has fibers with diameters ranging from 20 to 200 μm.

[0038] The outermost layer of the muscle fiber is the driving layer 1, which is composed of a fiber film that can conduct electricity and generate heat, such as carbon fiber, graphene fiber, silver-plated nylon fiber, etc., with a thickness ranging from 4 to 40 μm.

[0039] The middle layer of the muscle fiber is a heat insulation layer 2, which is made of a thin film material with good heat insulation effect and has a thickness range of 1-10μm.

[0040] The innermost layer of the muscle fibers is a supporting sensing layer 3, which is made of a material with good supporting properties, such as shape memory alloy wire or Kevlar fiber, with a thickness ranging from 10 to 120 μm. Preferably, a material with sensing properties, such as shape memory alloy wire, can be selected to improve the system's integration.

[0041] After obtaining composite biomimetic muscle fibers that meet the requirements, the resulting fibers are wound and twisted, as shown in the attached diagram. Figure 2As shown, in some implementations, multiple strands can be twisted.

[0042] The artificial muscle designed in this invention only requires heating the outermost driving layer when driven. Furthermore, due to the presence of an insulating layer in the middle, it ensures that as little heat as possible is transferred to the interior, thereby improving the utilization rate of the input heat and increasing the heat dissipation rate of the surface layer. This overcomes the disadvantage of slow heat dissipation of traditional wound materials and improves the response rate of the bionic muscle.

[0043] Example 2:

[0044] This embodiment proposes a mechanical finger driven by a proposed helical coiled artificial muscle, which has the following characteristics: Figure 1 Heshi Figure 2 See attached for details. Figure 4 and attached Figure 5 As shown, the mechanical finger includes a first phalanx 4, a second phalanx 6, and a third phalanx 8 hinged sequentially, and a first fast-response, heat-driven spiral-wound artificial muscle 5 and a second fast-response, heat-driven spiral-wound artificial muscle 7. The hinge point between the first phalanx 4 and the second phalanx 6 is the first phalanx, and the hinge point between the second phalanx 6 and the third phalanx 8 is the second phalanx. The two ends of the first fast-response, heat-driven spiral-wound artificial muscle 5 are respectively connected to the inner sides of the first phalanx 4 and the second phalanx 6, and the two ends of the second fast-response, heat-driven spiral-wound artificial muscle 7 are respectively connected to the inner sides of the second phalanx 6 and the third phalanx 8. The first and second phalanges are driven by the two artificial muscles.

[0045] The fast-response, heat-driven spiral-wound artificial muscle used in this embodiment is as described in Example 1. The diameter of the spiral-wound artificial muscle fiber is 65 μm, and the driving layer is a silver-plated nylon film with a thickness of 10 μm.

[0046] The insulation layer is made of polyimide film with a thickness of 5μm.

[0047] The supporting sensing layer is made of shape memory alloy wire with a diameter of 35μm.

[0048] The artificial muscle contracts by electrically heating the driving layer wrapped with artificial muscle fibers, thereby driving the finger to perform various movements. The insulating layer in the middle of the artificial muscle minimizes heat transfer to the interior, allowing for rapid temperature changes in the external driving layer and achieving a fast response. The supporting sensing layer inside the artificial muscle primarily provides structural support, but can also be made of materials with sensing properties to perform sensing functions. Different circuits are used to drive and control artificial muscle 1 and artificial muscle 2 to achieve greater finger dexterity.

[0049] Changes in physical quantities such as temperature can be obtained by detecting changes in the physical properties of the shape memory alloy wire supporting the sensing layer.

[0050] To facilitate the return of different parts of the fingers to their original positions, mechanisms such as torsion springs can be used at the joints to help the fingers quickly return to their original positions when power is cut off.

[0051] To facilitate the demonstration of the principle and structure of the proposed coiled artificial muscle-driven mechanical finger, the circuitry and wiring required for heating and control are not shown in this embodiment. This invention is used for driving mechanisms such as joints in microrobots and has the advantages of fast response, low cost, full functionality, and low noise.

[0052] Example 3:

[0053] like Figure 6 As shown, this embodiment provides a parallel artificial muscle, which includes multiple fast-response, heat-driven, spirally wound artificial muscles connected in parallel. Each fast-response, heat-driven, spirally wound artificial muscle is formed by spirally winding artificial muscle fibers. The artificial muscle fibers have a three-layer structure, consisting of a support sensing layer, a heat insulation layer, and a driving layer from the inside out. The driving layer is connected to an external circuit, which heats the driving layer to achieve the contraction movement of the artificial muscle. The heat insulation layer reduces heat transfer to the support sensing layer to achieve rapid temperature changes in the driving layer. The support sensing layer supports the artificial muscle fibers and can achieve sensing functions by selecting appropriate materials.

[0054] Based on the single fast-response spiral-wound artificial muscle used in Example 1, multiple artificial muscles can be connected in parallel to increase the overall force output. This can be achieved simply by keeping the power supply voltage constant and increasing the current output accordingly, based on the previous circuit.

[0055] In this embodiment, multiple artificial muscles are used in parallel to achieve greater force or deformation.

[0056] Example 4:

[0057] This embodiment provides a series artificial muscle, comprising multiple rapidly responding, heat-driven, spirally wound artificial muscles connected in series. Each rapidly responding, heat-driven, spirally wound artificial muscle is formed by spirally winding artificial muscle fibers. The artificial muscle fibers have a three-layer structure, consisting of a support sensing layer, a heat insulation layer, and a driving layer from the inside out. The driving layer is connected to an external circuit, which heats the driving layer to achieve the contraction movement of the artificial muscle. The heat insulation layer reduces heat transfer to the support sensing layer, thereby enabling rapid temperature changes in the driving layer. The support sensing layer supports the artificial muscle fibers and can achieve sensing functionality by selecting appropriate materials.

[0058] Based on the single fast-response spiral-wound artificial muscle used in Example 1, multiple artificial muscles can be connected in series to increase the overall displacement output. This can be achieved simply by keeping the power supply output current unchanged and increasing the power supply voltage accordingly.

[0059] In this embodiment, multiple artificial muscles are used in series to achieve greater force or deformation.

[0060] The following are comparative examples of the present invention and the prior art: Comparative Example 1

[0061] The artificial muscle fiber described in CN112201744A consists of a two-layer structure: a sheath and a core. The sheath is made of expensive carbon nanotube film, while the core is made of nylon thread. In contrast, this invention uses nylon film as the driving layer, a material that meets performance requirements while maintaining low cost. The support layer can use materials like shape memory alloy wire, which combine support and sensing properties, offering the potential for high integration. Furthermore, in CN112201744A, the sheath and core layers of the muscle fiber are in direct contact. During heating and driving, heat is quickly and fully transferred to the core layer. However, during heat dissipation, the poor radial heat dissipation capacity of carbon nanotubes prevents rapid heat dissipation, hindering rapid cooling and thus impeding the increase of the artificial muscle's driving frequency. In this invention, using polyimide, a material with good thermal insulation properties, as the insulation layer can maximally prevent heat transfer to the internal support and sensing layer, ensuring rapid temperature rise and fall of the driving layer and enabling a higher driving frequency.

[0062] Comparative Example 2

[0063] CN115142267A discloses a bidirectional driven spiral-wound artificial muscle, in which the biomimetic muscle fibers are composed of a guest material encapsulating a matrix material, and the artificial muscle is driven by energizing the electrothermal fibers inside the matrix. This invention, however, relies on heating the outermost driving layer to achieve high-frequency actuation, which is fundamentally different.

[0064] The embodiments described in this specification are merely examples of implementations of the inventive concept. The scope of protection of this invention should not be considered as limited to the specific forms stated in the embodiments. The scope of protection of this invention also extends to equivalent technical means that can be conceived by those skilled in the art based on the inventive concept.

Claims

1. A fast-response, heat-driven, spiral-wound artificial muscle, characterized in that: The artificial muscle is formed by spirally winding artificial muscle fibers. The artificial muscle fibers have a three-layer structure. The cross-section of the artificial muscle fibers forms a three-layer concentric circle structure, which consists of a circular support sensing layer, an annular heat insulation layer, and an annular driving layer from the inside to the outside. The driving layer is connected to an external circuit, which heats the driving layer to achieve the contraction movement of the artificial muscle; the heat insulation layer reduces the transfer of heat to the supporting sensing layer to achieve rapid temperature changes in the driving layer. The supporting sensing layer supports artificial muscle fibers, and the supporting sensing layer is made of shape memory alloy wire; The driving layer is made of a silver-plated nylon film; The heat insulation layer is a polyimide film; The diameter of the artificial muscle fibers is between 20-200 μm; The thickness of the supporting sensing layer is greater than the thickness of the driving layer; The thickness of the driving layer is 4-40 μm; The thickness of the heat insulation layer is 1-10 μm; The thickness of the supporting sensing layer is 10-120 μm.

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