Patent Publication Number: US-2023138999-A1

Title: Soft actuator, artificial muscle including the same and artificial muscle driving method using the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This U.S. non-provisional patent application claims priority under 35 U.S.C. § 119 of Korean Patent Application Nos. 10-2021-0148654, filed on Nov. 2, 2021, and 10-2022-0099414, filed on Aug. 9, 2022, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     The present disclosure herein relates to a soft actuator, an artificial muscle including the same and an artificial muscle driving method using the same, and more particularly, to a soft actuator capable of being precisely controlled, an artificial muscle including the same, and an artificial muscle driving method using the same. 
     An artificial muscle refers to a material or device that is artificially created by imitation of a real muscle and exhibits movement in response to stimuli such as a voltage, current, a temperature, and a pressure. Artificial muscle technologies start with a McKibben air muscle, which is contracted and relaxed while supplying compressed air into a tube, and are being developed with various materials, such as a shape memory alloy (SMA), an electroactive polymer (EAP), a yarn-structured polymer nano-material composite, etc., and structures. An electroactive polymer is a material that is moved when a voltage is applied and has various advantages such as a fast response speed, large deformation, low power consumption, and excellent processability, and have principles and characteristics most similar to those of muscles of the human body. Therefore, in spite of a limitation of a low output, the electroactive polymer is widely studied for artificial muscle technologies. The electroactive polymer may be divided into an ionic electroactive polymer (ionic EAP) and a field activated electroactive polymer (field activated EAP) according to an operation method thereof. When a voltage is applied to the ionic polymer, bending deformation (bending) occurs due to a volume difference generated as ions are moved in a direction of an electrode having opposite charges. The field activated EAP may undergo electronic polarization by an applied electric field and deformation by electrostatic force caused by electric charges induced in both electrodes. Among them, a dielectric elastomer is an artificial muscle material that is attracting the most attention for its very large amount of deformation and stress, a fast response speed, durability, and excellent reproducibility compared to other electroactive polymers. 
     SUMMARY 
     The present disclosure provides a soft actuator capable of being precisely controlled, an artificial muscle including the same, and an artificial muscle driving method using the same. 
     The present disclosure also provides a slim soft actuator having a small volume, an artificial muscle including the same, and an artificial muscle driving method using the same. 
     The object of the present invention is not limited to the aforesaid, but other objects not described herein will be clearly understood by those skilled in the art from descriptions below. 
     An embodiment of the inventive concept provides a soft actuator including: a first support body; a second support body spaced apart from the first support body in a first direction; a yarn structure having one end coupled to the first support body and the other end coupled to the second support body; and a light source part spaced apart from the yarn structure in a second direction crossing the first direction, wherein the yarn structure includes: a polymer layer having a coil spring shape extending in the first direction; and a light absorption layer configured to surround an outer surface of the polymer layer. 
     In an embodiment, the polymer layer may include at least one of nylon, polyvinyl alcohol (PVA), cotton, silk, or cellulose. 
     In an embodiment, the light absorption layer comprises poly(3,4-ethylenedioxythiophene) (PEDOT) doped with p-toluenesulfonate (PEDOT-Tos). 
     In an embodiment, the light source part may include a plurality of LED light sources, wherein the plurality of LED light sources may be arranged in the first direction. 
     In an embodiment, the yarn structure may be provided in plurality, wherein the plurality of yarn structures may be disposed to be spaced apart from each other in a third direction crossing each of the first direction and the second direction. 
     In an embodiment, the soft actuator may further include a reflective cover extending from the first support body to the second support body, wherein the reflective cover may be configured to surround the yarn structure and the light source. 
     In an embodiment, the reflective cover may include: an elastic polymer layer configured to define an inner space in which the yarn structure and the light source are disposed; and a light reflective layer on an outer surface of the elastic polymer layer. 
     In an embodiment, the elastic polymer layer may include polydimethylsiloxane (PDMS). 
     In an embodiment of the inventive concept, an artificial muscle includes: a soft actuator; and a connection member configured to couple the soft actuator to a human body, wherein the soft actuator includes: a first support body; a second support body spaced apart from the first support body in a first direction; a yarn structure extending from the first support body toward the second support body, the yarn structure having a coil spring shape; and a light source part spaced apart from the yarn structure in a second direction crossing the first direction, wherein the connection member includes: a first connection member coupled to the first support body; and a second connection member coupled to the second support body. 
     In an embodiment, the yarn structure may include: a polymer layer having a coil spring shape extending in the first direction; and a light absorption layer configured to surround an outer surface of the polymer layer. 
     In an embodiment, the polymer layer may include at least one of nylon, polyvinyl alcohol (PVA), cotton, silk, or cellulose, and the light absorption layer may include poly(3,4-ethylenedioxythiophene) (PEDOT) doped with p-toluenesulfonate (PEDOT-Tos). 
     In an embodiment, each of the first connection member and the second connection member may have a ring shape. 
     In an embodiment, the light source part may include a plurality of LED light sources, wherein the plurality of LED light sources may be arranged in the first direction. 
     In an embodiment of the inventive concept, an artificial muscle driving method includes: irradiating light to a yarn structure from a light source part; allowing a light absorption layer of the yarn structure to absorb the light so as to generate heat; and heating a polymer layer of the yarn structure by the heat emitted from the light absorption layer to contract a length of the polymer layer, wherein the polymer layer has a coil spring shape extending in a first direction, and the light absorption layer is configured to surround the polymer layer. 
     In an embodiment, the light source part may be spaced apart from the yarn structure in a second direction crossing the first direction. 
     In an embodiment, the polymer layer may include at least one of nylon, polyvinyl alcohol (PVA), cotton, silk, or cellulose, and the light absorption layer may include poly(3,4-ethylenedioxythiophene) (PEDOT) doped with p-toluenesulfonate (PEDOT-Tos). 
     Particularities of other embodiments are included in the detailed description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The accompanying drawings are included to provide a further understanding of the inventive concept, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the inventive concept and, together with the description, serve to explain principles of the inventive concept. In the drawings: 
         FIG.  1    is a perspective view of an artificial muscle according to an embodiment of the inventive concept; 
         FIG.  2    is a front view illustrating a yarn structure of a soft actuator according to an embodiment of the inventive concept; 
         FIG.  3    is a cross-sectional view of the yarn structure, taken along line I-I′ of  FIG.  2   ; 
         FIG.  4    is a flowchart illustrating an artificial muscle driving method according to an embodiment of the inventive concept; 
         FIG.  5    is a perspective view illustrating the artificial muscle driving method according to the flowchart of  FIG.  4   ; 
         FIG.  6    is a perspective view of an artificial muscle according to an embodiment of the inventive concept; 
         FIG.  7    is a perspective view of an artificial muscle according to an embodiment of the inventive concept; 
         FIG.  8    is a cross-sectional view of a soft actuator, taken along line II-IF of  FIG.  7   ; and 
         FIG.  9    is a perspective view illustrating a state of use of the artificial muscle according to an embodiment of the inventive concept. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments of technical ideas of the inventive concept will be described with reference to the accompanying drawings so as to sufficiently understand constitutions and effects of the inventive concept. The technical ideas of the inventive concept may, however, be embodied in different forms and should not be construed as limited to the embodiment set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. Further, the present invention is only defined by scopes of claims. 
     Like reference numerals refer to like elements throughout. The embodiments in the detailed description will be described with exemplary block diagrams, perspective views, and/or cross-sectional views as ideal exemplary views of the inventive concept. In the figures, the dimensions of regions are exaggerated for effective description of the technical contents. Regions exemplified in the drawings have general properties and are used to illustrate a specific shape of a device. Thus, this should not be construed as limited to the scope of the inventive concept. Also, although various terms are used to describe various components in various embodiments of the inventive concept, the component are not limited to these terms. These terms are only used to distinguish one component from another component. The embodiments described and exemplified herein include complementary embodiments thereof. 
     In the following description, the technical terms are used only for explaining a specific embodiment while not limiting the present invention. In this specification, the terms of a singular form may comprise plural forms unless specifically mentioned. The meaning of ‘comprises’ and/or ‘comprising’ does not exclude other components besides a mentioned component. 
     Hereinafter, the present disclosure will be described in detail by explaining preferred embodiments of the technical ideas of the inventive concept with reference to the attached drawings. 
       FIG.  1    is a perspective view of an artificial muscle according to an embodiment of the inventive concept. 
     Hereinafter, a direction D 1  in  FIG.  1    will be referred to as a first direction, a direction D 2  intersecting the first direction D 1  will be referred to as a second direction, and a direction D 3  intersecting each of the first direction D 1  and the second direction D 2  will be referred to as a third direction. 
     Referring to  FIG.  1   , an artificial muscle M may be provided. The artificial muscle M may provide power that moves a human body, instead of a portion of human body&#39;s muscles. For example, the artificial muscle M may be coupled to a finger of the human body to provide power that moves the finger. However, the embodiment of the inventive concept is not limited thereto, and the artificial muscle M may be coupled to other portions of the human body. The details thereof will be described with reference to  FIG.  9   . 
     The artificial muscle M may include a soft actuator A. The soft actuator A may be a device that provides power. More particularly, the soft actuator A may be stretched in the first direction D 1  or contracted in the first direction D 1 . For this, the soft actuator A may include a first support body  11 , a second support body  13 , a yarn structure  3 , and a light source part  5 . 
     The first support body  11  may be connected to one side of the human body. For example, the first support body  11  may be coupled to the human body so as to be fixed to one side of a joint of the human body. The first support body  11  may have a disk shape as illustrated in  FIG.  1   , but is not limited thereto. 
     The second support body  13  may be connected to the other side of the human body. For example, the second support body  13  may be coupled to the human body so as to be fixed to the other side of the joint of the human body. The second support body  13  may have a disk shape as illustrated in  FIG.  1   , but is not limited thereto. The second support body  13  may be spaced apart from the first support body  11 . For example, as illustrated in  FIG.  1   , the second support body  13  may be spaced a predetermined distance from the first support body  11  in the first direction D 1 . 
     The yarn structure  3  may connect the first support body  11  to the second support body  13 . For example, one side of the yarn structure  3  may be coupled to one surface of the first support body  11 , and the other side of the yarn structure  3  may be coupled to one surface of the second support body  13 . When the first support body  11  and the second support body  13  are spaced apart from each other in the first direction D 1 , the yarn structure  3  may extend in the first direction D 1 . The yarn structure  3  may have a coil spring shape. That is, the yarn structure  3  may have a coil spring shape extending in the first direction D 1 . The yarn structure  3  may be stretched or contracted. More specifically, the yarn structure  3  may be stretched or contracted so that a length of the yarn structure  3  in the first direction D 1  varies. Thus, a distance between the first support body  11  and the second support body  13  may vary. The details thereof will be described later. 
     The light source part  5  may irradiate light to the yarn structure  3 . The light source part  5  may be spaced apart from the yarn structure  3  in a direction crossing the first direction D 1 . For example, as illustrated in  FIG.  1   , the light source part  5  may be spaced apart from the yarn structure  3  in the second direction D 2 . The light source part  5  may include an LED light source  51  and a light source support member  53 . 
     The LED light source  51  may be disposed to face the yarn structure  3 . For example, as illustrated in  FIG.  1   , the LED light source  51  may be disposed in a direction opposite to the second direction D 2 . The LED light source  51  may irradiate light toward the yarn structure  3 . A temperature of at least a portion of the yarn structure  3  may increase by the light irradiated by the LED light source  51 . The LED light source  51  may be provided in plurality. The plurality of LED light sources  51  may be arranged along the extension direction of the yarn structure  3 . For example, the plurality of LED light sources  51  may be arranged in the first direction D 1 . However, hereinafter, for convenience, the LED light source  51  will be described in the singular. 
     The light source support member  53  may support the LED light source  51 . The light source support member  53  may be connected to the first support body  11  or the second support body  13 . For example, as illustrated in  FIG.  1   , the light source support member  53  may extend from the second support body  13  in a direction opposite to the first direction D 1 . 
       FIG.  2    is a front view illustrating the yarn structure of the soft actuator according to an embodiment of the inventive concept, and  FIG.  3    is a cross-sectional view of the yarn structure, taken along line I-I′ of  FIG.  2   . 
     Referring to  FIGS.  2  and  3   , the yarn structure  3  may include a polymer layer  31  and a light absorption layer  33 . 
     The polymer layer  31  may have a coil spring shape. More specifically, the polymer layer  31  illustrated in  FIG.  3    may have a coil spring shape extending in the first direction D 1  as illustrated in  FIG.  2   . The polymer layer  31  may include a polymer fiber material. For example, the polymer layer  31  may include at least one of nylon, polyvinyl alcohol (PVA), cotton, silk, or cellulose. However, the embodiment of the inventive concept is not limited thereto, and the polymer layer  31  may include other types of materials, which vary in volume according to a temperature. 
     The light absorption layer  33  may surround the polymer layer  31 . More specifically, the light absorption layer  33  may surround an outer surface  31   s  of the polymer layer  31  as illustrated in  FIG.  3   . That is, the light absorption layer  33  may be in contact with the outer surface  31   s  of the polymer layer  31 . When the polymer layer  31  has a coil spring shape extending in the first direction as illustrated in  FIG.  2   , the light absorption layer  33  surrounding the polymer layer  31  may also have a coil spring shape similar to that of the polymer layer  31 . The light absorption layer  33  may absorb light. For example, when light is irradiated to an outer surface  33   s  of the light absorption layer  33 , the light absorption layer  33  may absorb the light. Thus, a temperature of the light absorption layer  33  may increase. For this, the light absorption layer  33  may include a material of which a temperature varies by absorbing the light. For example, the light absorption layer  33  may include poly(3,4-ethylenedioxythiophene) (PEDOT) doped with p-toluenesulfonate (PEDOT-Tos). However, the embodiment of the inventive concept is not limited thereto, and the light absorption layer  33  may include other types of materials capable of absorbing light. The light absorption layer  33  may be formed through various methods. For example, the light absorption layer  33  may be applied on the outer surface  31   s  of the polymer layer  31  through a spray coating and/or dip-coating process. However, the embodiment of the inventive concept is not limited thereto, and the light absorption layer  33  may be formed through other processes. 
     The details on a function of the yarn structure  3  will be described later. 
       FIG.  4    is a flowchart illustrating an artificial muscle driving method according to an embodiment of the inventive concept. 
     Referring to  FIG.  4   , an artificial muscle driving method S may be provided. The artificial muscle driving method S may be a method of driving the artificial muscle M described with reference to  FIGS.  1  to  3   . The artificial muscle driving method S may include a process (S 1 ) of irradiating light to a yarn structure, a process (S 2 ) of allowing a light absorption layer to absorb light so as to generate heat, and a process (S 3 ) of allowing a polymer layer to be contracted in length. 
     Hereinafter, the artificial muscle driving method S of  FIG.  4    will be described with reference to  FIGS.  5  and  3   . 
       FIG.  5    is a perspective view illustrating the artificial muscle driving method according to the flowchart of  FIG.  4   . 
     Referring to  FIGS.  5 ,  3  and  4   , the process (S 1 ) of irradiating light to the yarn structure may include a process of allowing a light source part  5  to irradiate light to the yarn structure. That is, the light emitted from the LED light source  51  may be irradiated to the yarn structure  3 . When the LED light source  51  is provided in plurality, light may be emitted from each of the plurality of LED light sources  51  so as to be irradiated to the yarn structure  3 . The light emitted from the LED light source  51  may be irradiated to an outer surface  33   s  of a light absorption layer  33 . 
     The light absorption layer absorbing light to generate heat (S 2 ) may include absorbing light irradiated to the outer surface  33   s  of the light absorption layer  33  by the light absorption layer  33 . When the light absorption layer  33  absorbs the light, a temperature of the light absorption layer  33  may increase. When the temperature of the light absorption layer  33  increases, the light absorption layer  33  may radiate heat to the surroundings. That is, due to a photo-thermal effect, the light absorbed by the light absorption layer  33  may be used to radiate heat to the surroundings. At least a portion of the heat emitted from the light absorption layer  33  may be transferred to a polymer layer  31 . 
     The process (S 3 ) of allowing the polymer layer to be contracted in length may include a process of heating the polymer layer  31  by the heat emitted from the light absorption layer  33 . When the polymer layer  31  is heated by the heat, the temperature of the polymer layer  31  may increase. When the temperature of the polymer layer  31  increases, the polymer layer  31  may be expanded. More specifically, as the temperature of the polymer layer  31  increases, the polymer layer  31  may be expanded in a thickness direction. That is, the polymer layer  31  may be expanded so that a cross-sectional area of the polymer layer  31  as illustrated in  FIG.  3    is widened. When the polymer layer  31  is expanded in the thickness direction, a length of the polymer layer  31  may be contracted. That is, the length of the polymer layer  31  in the first direction D 1  may be reduced. When the length of the polymer layer  31  is contracted, a gap between the first support body  11  and the second support body  13  may be narrowed. That is, the first support body  11  and the second support body  13  may approach each other. Thus, the entire soft actuator A may be contracted. 
     In the above description, the soft actuator A is used for an artificial muscle M, but is not limited thereto. That is, the soft actuator A may be applied to other technical fields other than the artificial muscle. 
     According to the soft actuator, the artificial muscle including the same, and the artificial muscle driving method using the same according to embodiments of the inventive concept, the soft actuator may operate using the light source. Therefore, the soft actuator may be reduced in volume and lighten in weight. Therefore, when the soft actuator is applied to the artificial muscle, a burden on the human body may be reduced. 
     According to the soft actuator, the artificial muscle including the same, and the artificial muscle driving method using the same according to embodiments of the inventive concept, the yarn structure may be contracted using the light source, and thus, the soft actuator may be precisely driven. That is, an intensity of light irradiated from the light source may be adjusted to control a degree of deformation of the soft actuator. Since the degree of deformation of the soft actuator is controlled using the intensity of light, the soft actuator may be precisely controlled. Therefore, the control precision of the artificial muscle may be improved. 
       FIG.  6    is a perspective view of an artificial muscle according to an embodiment of the inventive concept. 
     Hereinafter, descriptions of contents substantially the same as or similar to those described with reference to  FIGS.  1  to  5    may be omitted. 
     Referring to  FIG.  6   , an artificial muscle M′ may be provided. The artificial muscle M′ may include a soft actuator A′. However, unlike that described with reference to  FIG.  1   , the soft actuator A′ of  FIG.  6    may include a plurality of yarn structures  3 ′. For example, four yarn structures  3 ′ may be provided as illustrated in  FIG.  6   . However, the embodiment of the inventive concept is not limited thereto, and the number of yarn structures  3 ′ may be applied differently according to a specific design. The plurality of yarn structures  3 ′ may be spaced apart from each other in the third direction D 3 . 
     According to the soft actuator, the artificial muscle including the same, and the artificial muscle driving method using the same according to embodiments of the inventive concept, contractile force of the soft actuator may be improved by using the plurality of yarn structures. That is, when a sufficient output is not secured with only one yarn structure, a plurality of yarn structures may be applied. In this way, the output of the soft actuator may be adjusted. 
       FIG.  7    is a perspective view of an artificial muscle according to an embodiment of the inventive concept, and  FIG.  8    is a cross-sectional view of a soft actuator, taken along line II-II′ of  FIG.  7   . 
     Hereinafter, descriptions of contents substantially the same as or similar to those described with reference to  FIGS.  1  to  6    may be omitted. 
     Referring to  FIGS.  7  and  8   , an artificial muscle M″ may be provided. The artificial muscle M″ may include a soft actuator A″. However, unlike that described with reference to  FIG.  1   , the soft actuator A″ of  FIG.  7    may further include a reflective cover  7 . 
     The reflective cover  7  may surround a light source  5  and a yarn structure  3 . In embodiments, the reflective cover  7  may extend from a first support body  11  to a second support body  13 . That is, the reflective cover  7  may extend from the first support body  11  in the first direction D 1  so as to be connected to the second support body  13 . The reflective cover  7  may reflect light. More specifically, the reflective cover  7  may reflect light that is not absorbed by the yarn structure  3  among the light irradiated from the light source part  5 . For this, the reflective cover  7  may include an elastic polymer layer  71  and a light reflective layer  73 . 
     The elastic polymer layer  71  may provide an inner space  7   h . The yarn structure  3  and/or the light source part  5  may be disposed in the inner space  7   h . A length of the elastic polymer layer  71  in the first direction D 1  may vary. That is, when the first support body  11  and the second support body  13  are closer to each other due to the contraction of the yarn structure  3 , the length of the elastic polymer layer  71  in the first direction D 1  may vary. For this, the elastic polymer layer  71  may include a contractible material. For example, the elastic polymer layer  71  may include polydimethylsiloxane (PDMS). However, the embodiment of the inventive concept is not limited thereto, and the elastic polymer layer  71  may include other materials having a variable length. 
     The light reflective layer  73  may be disposed on an outer surface of the elastic polymer layer  71 . More specifically, the light reflective layer  73  may surround the elastic polymer layer  71 . The light reflective layer  73  may be formed on the elastic polymer layer  71  through various methods. For example, the light reflective layer  73  may be formed on the elastic polymer layer  71  through a process such as bar coating, meniscus dragging deposition (MDD), spray coating, evaporation, or sputtering. The light reflective layer  73  may include a material capable of reflecting light. More specifically, the light reflective layer  73  may include a thin metal material capable of reflecting visible light and/or infrared light. 
     According to the soft actuator, the artificial muscle including the same, and the artificial muscle driving method using the same according to embodiments of the inventive concept, the reflective cover including the light reflective layer may surround the yarn structure and the light source part. The light that is not absorbed by the yarn structure in the light irradiated from the light source may be reflected by the light reflective layer and then irradiated again to the yarn structure. Thus, an amount of light absorbed by the yarn structure may increase. Thus, energy efficiency may be improved. 
       FIG.  9    is a perspective view illustrating a state of use of the artificial muscle according to an embodiment of the inventive concept. 
     Referring to  FIG.  9   , the artificial muscle M may further include a connection member  9 . The connection member  9  may couple a soft actuator to a human body HF. The connection member  9  may include a first connection member  91  and a second connection member  93 . 
     The first connection member  91  may be coupled to a first support body  11 . The first connection member  91  may be fixed to one side of the human body HF. The first connection member  91  may have a ring shape as illustrated in  FIG.  9   , but is not limited thereto. 
     The second connection member  93  may be coupled to a second support body  13 . The second connection member  93  may be fixed to one side of the human body HF. The second connection member  93  may have a ring shape as illustrated in  FIG.  9   , but is not limited thereto. 
     According to the soft actuator, the artificial muscle including the same, and the artificial muscle driving method using the same according to embodiments of the inventive concept, one side of the artificial muscle may be fixed to one side of the human body, and the other side of the artificial muscle may be fixed to the other side of the human body. If the soft actuator is contracted in this state, a portion of the human body may be moved. For example, as illustrated in  FIG.  9   , when the soft actuator is contracted while the artificial muscle is coupled to a finger joint of the human body, the finger joint may be bent. 
     Although the above has been illustrated and described based on the artificial muscles used on the fingers of the human body, the embodiment of the inventive concept is not limited thereto. That is, the artificial muscle according to the inventive concept may be applied to other joints. 
     According to the soft actuator, the artificial muscle including the same, and the artificial muscle driving method using the same according to the embodiment, the soft actuator may be precisely controlled. 
     According to the soft actuator, the artificial muscle including the same, and the artificial muscle driving method using the same according to the embodiment, the soft actuator may have the small volume and be slim. 
     According to the soft actuator, the artificial muscle including the same, and the artificial muscle driving method using the same according to the embodiment, the soft actuator may be bent with the plurality of curvatures. 
     The effects of the present invention are not limited to the aforementioned objects, but other effects not described herein will be clearly understood by those skilled in the art from descriptions below. 
     Although the embodiment of the present invention is described with reference to the accompanying drawings, those with ordinary skill in the technical field of the present invention pertains will be understood that the present invention can be carried out in other specific forms without changing the technical idea or essential features. Thus, the above-disclosed embodiments are to be considered illustrative and not restrictive.