Patent Publication Number: US-2022228300-A1

Title: Cylindrical structure

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of International application No. PCT/JP2020/043597, filed Nov. 24, 2020, which claims priority to Japanese Patent Application No. 2019-212117, filed Nov. 25, 2019, the entire contents of each of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a cylindrical structure that generates an electric field. 
     BACKGROUND OF THE INVENTION 
     Patent Document 1 discloses a thread that generates an electric field. The thread disclosed in Patent Document 1 includes charge-generating fibers that generate an electric charge from the input of external energy. The thread disclosed in Patent Document 1 exerts an antibacterial effect by an electric field or an electric current generated between the threads. 
     Patent Document 1: Japanese Patent Application Laid-Open No. 2018-090950 
     SUMMARY OF THE INVENTION 
     The thread disclosed in Patent Document 1 locally generates an electric field in a micro space between the threads. Therefore, the area where the antibacterial effect can be obtained by the electric field is narrow. 
     An object of the present invention is to provide a cylindrical structure that exhibits an antibacterial effect in a wide area. 
     The cylindrical structure of the present invention includes a first cloth including a piezoelectric thread that generates an electric potential from external energy, a second cloth including a piezoelectric thread that generates an electric potential from external energy, and a connection portion connecting the first cloth and the second cloth, wherein the first cloth and the second cloth forms a side face of the cylindrical structure. 
     When the cylindrical structure according to the present invention is given energy from the outside, the first cloth generates a positive charge and the second cloth generates a negative charge. Because the first cloth and the second cloth are arranged on the side face of the cylindrical structure, they face each other. As a result, an electric field is generated between the first cloth and the second cloth. Therefore, the cylindrical structure can exert an antibacterial effect in a wide area between the first cloth and the second cloth. 
     According to the present invention, the antibacterial effect can be exhibited in a wide area. 
    
    
     
       BRIEF EXPLANATION OF THE DRAWINGS 
         FIG. 1(A)  is a perspective view showing a configuration of a cylindrical structure according to a first embodiment,  FIG. 1(B)  is sectional view of the cylindrical structure cut perpendicularly to the axial direction of  FIG. 1(A) , and  FIG. 1(C)  is a partial enlarged view of a first cloth and a second cloth according to the first embodiment. 
         FIG. 2(A)  is a partial enlarged view for explaining a configuration of a first piezoelectric thread according to the first embodiment, and  FIG. 2(B)  is a sectional view taken along line I-I in  FIG. 2(A) . 
         FIGS. 3(A) and 3(B)  are views showing the relationship between a uniaxial drawing direction of a polylactic acid film, an electric field direction, and a deformation of the polylactic acid film. 
         FIG. 4(A)  is a view showing shear stress generated in each piezoelectric fiber when a tension is applied to the first piezoelectric thread, and  FIG. 4(B)  is a view showing shear stress generated in each piezoelectric fiber when a tension is applied to a second piezoelectric thread. 
         FIG. 5  is a sectional view schematically showing a part of a cylindrical structure for explaining an electric charge generated in the cylindrical structure. 
         FIG. 6(A)  is a perspective view showing a configuration of a cylindrical structure according to a second embodiment, and  FIG. 6(B)  is a sectional view of the cylindrical structure cut perpendicularly to the axial direction of  FIG. 6(A) . 
         FIG. 7(A)  is a perspective view showing a configuration of a cylindrical structure according to a third embodiment, and  FIG. 7(B)  is sectional view of the cylindrical structure cut perpendicularly to the axial direction of  FIG. 7(A) . 
         FIG. 8(A)  is a perspective view showing a configuration of a cylindrical structure according to a fourth embodiment, and  FIG. 8(B)  is a sectional view of the cylindrical structure cut in the axial direction of  FIG. 8(A) . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1(A)  is a perspective view showing a configuration of a cylindrical structure  10  according to a first embodiment,  FIG. 1(B)  is a sectional view of the cylindrical structure  10  cut perpendicularly to the axial direction, and  FIG. 1(C)  is a partial enlarged view of a first cloth  101  and a second cloth  102  according to the first embodiment.  FIG. 1(C)  is an enlarged view of the area R shown in  FIG. 1(A) . Hereinafter, description is made in which the axial direction of the cylindrical structure  10  is a Z direction, the radial direction is an r direction, and the circumferential direction is a θ direction. 
     As shown in  FIGS. 1(A) and 1(B) , the cylindrical structure  10  is a cylindrical structure having a hollow  13  inside. The cylindrical structure  10  includes a first cloth  101  and a second cloth  102 . The first cloth  101  and the second cloth  102  form a side face of the cylindrical structure  10 . The first cloth  101  is connected to the second cloth  102  at an end portion  103  in the  8  direction of the cylindrical structure  10 . As a result, in the cylindrical structure  10 , the first cloth  101  faces the second cloth  102  with the hollow  13  interposed therebetween. 
     As shown in  FIG. 1(C) , the first cloth  101  includes a first piezoelectric thread  11 . The first cloth  101  is a flat knitted fabric in which the first piezoelectric thread  11  is knitted. The first cloth  101  has a structure in which loops made of the first piezoelectric thread  11  are hooked in order along the  8  direction. The second cloth  102  includes a second piezoelectric thread  12 . The second cloth  102  is a flat knitted fabric in which the second piezoelectric thread  12  is knitted, similarly to the first cloth  101 . At the end portion  103 , the first piezoelectric thread  11  and the second piezoelectric thread  12  are knitted together. The first cloth  101  may be stitched and connected to the second cloth  102  at the end portion  103 , or may be connected by an adhesive or a pressure-sensitive adhesive. In the description of the area R, the area R is assumed to be a plane face. The area R is curved along the  8  direction in practice. The first cloth  101  may be formed from a plurality of first piezoelectric threads  11 , and the second cloth  102  may be formed from a plurality of second piezoelectric threads  12 . Both the first cloth  101  and the second cloth  102  may be formed from the first piezoelectric thread  11 , and both the first cloth  101  and the second cloth  102  may be formed from the second piezoelectric thread  12 . 
     In the present specification, “cylindrical” means a so-called tubular shape, and the shape includes for example a shape in which a part of the side face is flat, a shape in which the whole side face is flat, and a solid shape without the hollow  13 . Because the first cloth  101  and the second cloth  102  are made of knitted fabrics, they are highly stretchable and easily deformed as compared with the case of being made of woven fabrics. Therefore, the cylindrical structure  10  easily curves as a whole as compared with the case of being made of a woven fabric. However, the cylindrical structure  10  of the present invention may be made of a woven fabric. 
     Further, a structure having a section like a corrugated board structure is also a continuum of a cylindrical structure, and is included in “cylindrical structure” of the present specification. The cylindrical structure  10  also includes, for example, a sectional shape formed from a double raschel (warp knitting), a double weave, or the like. 
     The plurality of first piezoelectric threads  11  are restrained from each other by being entangled with each other. When the first cloth  101  is stretched in the Z direction or the θ direction, the plurality of first piezoelectric threads  11  are pulled in the Z direction or the θ direction. When the plurality of first piezoelectric threads  11  are pulled with a force of a certain degree or more, the flexure of the loops disappears. At this time, because the plurality of first piezoelectric threads  11  are restrained from each other, each of the first piezoelectric threads  11  itself is stretched in its axial direction. Similarly, the plurality of second piezoelectric threads  12  are restrained from each other by being entangled with each other. Therefore, when the second cloth  102  is stretched in the Z direction or the  8  direction with a force of a certain degree or more, each of the second piezoelectric threads  12  itself is stretched in its axial direction. 
     The first piezoelectric thread  11  generates a negative charge on the surface from external energy, for example, stretching. The second piezoelectric thread  12  generates a positive charge on the surface from external energy, for example, stretching. 
       FIG. 2(A)  is a partial enlarged view for explaining a configuration of the first piezoelectric thread  11  according to the first embodiment, and  FIG. 2(B)  is a sectional view taken along line I-I in  FIG. 2(A) . Hereinafter, the first piezoelectric thread  11  will be described, and for the second piezoelectric thread  12 , only differences from the first piezoelectric thread  11  will be described. 
     As shown in  FIG. 2(A)  and  FIG. 2(B) , the first piezoelectric thread  11  is a twisted thread (multifilament thread) formed by twisting a plurality of piezoelectric fibers  110 . In  FIG. 2(A)  and  FIG. 2(B) , the first piezoelectric thread  11  in which seven piezoelectric fibers  110  are twisted is shown as one example, but the number of the piezoelectric fibers  110  is not limited to this, and the number is set appropriately in consideration of the usage and the like in practice. 
     The piezoelectric fiber  110  is one example of a charge-generating fiber that generates an electric charge from external energy. The piezoelectric fiber  110  is made of a functional polymer, for example, a piezoelectric polymer. Examples of the piezoelectric polymer include PVDF and polylactic acid (PLA). Polylactic acid (PLA) is a piezoelectric polymer that does not have pyroelectricity. Polylactic acid becomes piezoelectric by being uniaxially drawn. Polylactic acid includes PLLA in which an L-form monomer is polymerized and PDLA in which a D-form monomer is polymerized. The piezoelectric fiber  110  may further contain a component other than the functional polymer as long as it does not inhibit the function of the functional polymer. 
     Polylactic acid is a chiral polymer, whose main chain has a spiral structure. Polylactic acid exhibits piezoelectricity when it is uniaxially drawn and the molecules are oriented. When a heat treatment is further applied to increase the crystallinity, the piezoelectric constant increases. The piezoelectric fiber  110  made of uniaxially drawn polylactic acid has tensor components of d 14  and d 25  as piezoelectric strain constants where the thickness direction is defined as a first axis, a drawing direction  900  is defined as a third axis, and the direction orthogonal to both the first axis and the third axis is defined as a second axis. Therefore, polylactic acid most efficiently generates an electric charge when strain occurs in the direction of 45 degrees with respect to the uniaxially drawn direction. 
       FIG. 3(A)  and  FIG. 3(B)  are views showing the relationship between a uniaxial drawing direction of a polylactic acid film  30 , an electric field direction, and a deformation of the polylactic acid film  30 . The polylactic acid film  30  of  FIG. 3(A)  and  FIG. 3(B)  is a model case in which the piezoelectric fiber  110  is assumed to have a film shape. As shown in  FIG. 3(A) , when the polylactic acid film  30  shrinks in the direction of a first diagonal line  910 A and stretches in the direction of a second diagonal line  910 B orthogonal to the first diagonal line  910 A, it generates an electric field in the direction from the back side to the front side of the plane of paper. That is, the polylactic acid film  30  generates a negative charge on the front side of the paper. As shown in  FIG. 3(B) , the polylactic acid film  30  also generates an electric charge when it stretches in the direction of the first diagonal line  910 A and shrinks in the direction of the second diagonal line  910 B, but the polarity is reversed and an electric field is generated in the direction from the front side to the back side of the plane of paper. That is, the polylactic acid film  30  generates a positive charge on the front side of the paper. 
     Because polylactic acid obtains piezoelectricity by the molecular orientation treatment by drawing, there is no need of a polling treatment unlike other piezoelectric polymers such as PVDF or piezoelectric ceramics. The uniaxially drawn polylactic acid has a piezoelectric constant of about 5 to 30 pC/N, which is a very high piezoelectric constant among polymers. Furthermore, the piezoelectric constant of polylactic acid does not fluctuate with time and is extremely stable. 
     The piezoelectric fiber  110  is a fiber having a circular section. The piezoelectric fiber  110  is produced by, for example, a method of extrusion-molding a piezoelectric polymer into fibers, a method of melt-spinning a piezoelectric polymer into fibers (for example, a spinning/drawing method in which a spinning step and a drawing step are performed separately, a straight drawing method in which a spinning step and a drawing step are connected, a POY-DTY method in which a drew texturizing step can also be performed at the same time, an ultra-high speed spinning method that aims speeding up, or the like), a method of fiberizing a piezoelectric polymer by dry or wet spinning (for example, a phase separation method or a dry-wet spinning method in which a polymer as a raw material is dissolved in a solvent and extruded from a nozzle to form fibers, or a gel spinning method in which a polymer is uniformly fiberized into a gel while containing a solvent, a method of fiberizing with a liquid crystal solution or a melt, or the like), a method of fiberizing a piezoelectric polymer by electrostatic spinning, or the like. The sectional shape of the piezoelectric fiber  110  is not limited to a circular shape. 
     The first piezoelectric thread  11  is a right swirl thread (hereinafter referred to as S thread) twisted by swirling a plurality of PLLA piezoelectric fibers  110  to the right. The second piezoelectric thread  12  is a left swirl thread (hereinafter referred to as Z thread) twisted by swirling a plurality of PLLA piezoelectric fibers  110  to the left. The first piezoelectric thread  11  and the second piezoelectric thread  12  may be spun threads, non-twisted threads, or drew texturized threads. 
     The drawing direction  900  of each piezoelectric fiber  110  coincides with the axial direction  21  of each piezoelectric fiber  110 . In the first piezoelectric thread  11 , the drawing direction  900  of each piezoelectric fiber  110  is in a state of being tilted 45 degrees to the left with respect to an axial direction  111  of the first piezoelectric thread  11 . In the second piezoelectric thread  12 , the drawing direction  900  of each piezoelectric fiber  110  is in a state of being tilted 45 degrees to the right with respect to the axial direction of the second piezoelectric thread  12 . The angle of tilt of the drawing direction  900  with respect to the axial direction  111  of the first piezoelectric thread  11  depends on the number of twists of the piezoelectric fiber  110 . As the number of twists of the piezoelectric fibers  110  increases, the angle of tilt of the drawing direction  900  of each piezoelectric fiber  110  with respect to the axial direction  111  of the first piezoelectric thread  11  increases. Therefore, in the first piezoelectric thread  11  or the second piezoelectric thread  12 , the angle of tilt of the piezoelectric fiber  110  with respect to the axial direction  111  of the first piezoelectric thread  11  or the second piezoelectric thread  12  can be adjusted by adjusting the number of twists of the piezoelectric fiber  110 . 
       FIG. 4(A)  shows shear stress generated in each piezoelectric fiber  110  when a tension is applied to the first piezoelectric thread  11 , and  FIG. 4(B)  shows shear stress generated in each piezoelectric fiber  110  when a tension is applied to the second piezoelectric thread  12 . 
     As shown in  FIG. 4(A) , when an external force (tension) in the axial direction  111  is applied to the first piezoelectric thread  11 , the piezoelectric fiber  110  reaches a state as shown in  FIG. 3(A)  and generates a negative charge on the surface. The first piezoelectric thread  11  generates a negative charge on the surface when an external force is applied. As shown in  FIG. 4(B) , when an external force (tension) is applied to the second piezoelectric thread  12 , the piezoelectric fiber  110  reaches a state as shown in  FIG. 3(B)  and generates a positive charge on the surface. The second piezoelectric thread  12  generates a positive charge on the surface when an external force is applied. 
       FIG. 5  is a sectional view schematically showing a part of the cylindrical structure  10  cut perpendicularly to the Z direction for explaining an electric charge generated in the cylindrical structure  10 . The cylindrical structure  10  includes the first cloth  101  including a plurality of first piezoelectric threads  11  and the second cloth  102  having a plurality of second piezoelectric threads  12 . When the cylindrical structure  10  stretches in the  8  direction or the Z direction, the first cloth  101  and the second cloth  102  stretch. The plurality of first piezoelectric threads  11  and the plurality of second piezoelectric threads  12  stretch in their respective axial directions. The plurality of first piezoelectric threads  11  stretched in the axial direction generate a negative charge on the surface. The plurality of second piezoelectric threads  12  stretched in the axial direction generate a positive charge on the surface. Therefore, when the cylindrical structure  10  stretches, it generates a negative charge on the surface of the first cloth  101  and a positive charge on the surface of the second cloth  102 , as shown in  FIG. 5 . 
     The end portion  103  where the first cloth  101  and the second cloth  102  contact each other has the same potential. At this time, the portion other than the end portion  103  of the first cloth  101  has a lower negative potential in order to maintain the original potential difference from the second cloth  102  as a whole of the first cloth  101 . The portion of the second cloth  102  other than the end portion  103  has a higher positive potential in order to maintain the original potential difference from the first cloth  101  as a whole of the second cloth  102 . Therefore, the first cloth  101  and the second cloth  102  generate an electric field at a portion where they face each other except the end portion  103 . That is, a strong electric field is formed in the hollow  13  which is a wide area surrounded by the first cloth  101  and the second cloth  102 . Therefore, the cylindrical structure  10  can generate an electric field in a wide area. 
     It has been known that electric fields can suppress the growth of bacteria and fungi (see, for example, Tetsuaki Tsuchido, Hiroki Kourai, Hideaki Matsuoka, Jun-ichi Koizumi,  Microorganism Control - Science and Engineering , Kodansha. See also, for example, Koichi Takaki, Agricultural and Food Processing Applications of High-Voltage and Plasma Technologies, J. HTSJ, Vol. 51, No. 216). In addition, due to the electric potential that causes an electric field, an electric current may flow through a current path formed by moisture or the like, or through a circuit formed by a local micro discharge phenomenon or the like. It is considered that this electric current weakens bacteria and suppresses the growth of bacteria. The bacteria referred to in this embodiment includes bacteria, fungi, and a microorganism such as mites and fleas. 
     Therefore, the cylindrical structure  10  directly exerts an antibacterial effect by the electric field formed in the hollow  13 . That is, the cylindrical structure  10  exerts an antibacterial effect against the bacteria taken into the hollow  13 . As a result, the cylindrical structure  10  can exert an antibacterial effect in a wide area between the first cloth  101  and the second cloth  102  where the faces of the first cloth  101  and the second cloth  102  face each other. 
     In addition, the cylindrical structure  10  exerts an antibacterial effect directly by an electric field formed in the vicinity of the cylindrical structure  10  or by an electric field generated when the cylindrical structure  10  comes close to an object having a predetermined potential such as a human body. Alternatively, the cylindrical structure  10  passes an electric current through moisture such as sweat when the cylindrical structure  10  comes close to another nearby fiber or an object having a predetermined potential such as a human body. The cylindrical structure  10  directly exerts an antibacterial effect by this electric current as well in some cases. Alternatively, the cylindrical structure  10  indirectly exerts an antibacterial effect by reactive oxygen species in which oxygen contained in water is changed by the action of electric current or voltage, radical species generated by interaction or catalysis with additives contained in fibers, or other antibacterial chemical species (amines derivatives, etc.), in some cases. Alternatively, in some cases, oxygen radicals are generated in the cells of bacteria by the stress environment due to the presence of an electric field or an electric current, and the cylindrical structure  10  indirectly exerts an antibacterial effect by the oxygen radicals in some cases. As the radical, generation of superoxide anion radical (reactive oxygen) or hydroxyl radical can be considered. “Antibacterial” as used in the present embodiment is a concept including both an effect of suppressing the growth of bacteria and an effect of killing bacteria. 
     As the thread that generates a negative charge on the surface, the Z thread using PDLA can be considered in addition to the S thread using PLLA. As the thread that generates a positive charge on the surface, the S thread using PDLA can be considered in addition to the Z thread using PLLA. 
     The first cloth  101  and the second cloth  102  may include a non-piezoelectric thread. Here, the non-piezoelectric thread includes a thread made of natural fibers or synthetic fibers typically used as a thread and which does not generate an electric charge from external energy. Examples of the natural fiber include cotton, wool, and hemp. Examples of the synthetic fiber include polyester, polyurethane, rayon, cupra, and acetate. The non-piezoelectric thread may be a twisted thread obtained by twisting natural fibers or synthetic fibers. The strength or the degree of stretch of the first cloth  101  and the second cloth  102  can be adjusted by selecting the material of the non-piezoelectric thread or the amount of the non-piezoelectric thread to be included. 
     The first cloth  101  may have a structure in which the loops of the first piezoelectric thread  11  are hooked in order along the Z direction. Similarly, the second cloth  102  may have a structure in which loops of the second piezoelectric thread  12  are hooked in order along the Z direction. 
     The first cloth  101  or the second cloth  102  may be a woven fabric. In this case, the first piezoelectric thread  11  is included in the warp or weft of the first cloth  101 . The second piezoelectric thread  12  is included in the warp or weft of the second cloth  102 . When the cylindrical structure  10  is stretched, the first piezoelectric thread  11  or the second piezoelectric thread  12  is pulled in the axial direction of each piezoelectric thread. As a result, the cylindrical structure  10  can exert an antibacterial effect. Further, the first cloth  101  or the second cloth  102  may be a non-woven fabric. 
     Hereinafter, a cylindrical structure  60  according to a second embodiment will be described.  FIG. 6(A)  is a perspective view showing a configuration of the cylindrical structure  60  according to the second embodiment, and  FIG. 6(B)  is a sectional view of the cylindrical structure  60  cut perpendicularly to the axial direction. In the description of the cylindrical structure  60 , only the points different from those of the first embodiment will be described, and the same points will be omitted. 
     As shown in  FIG. 6(A)  and  FIG. 6(B) , the cylindrical structure  60  includes a joint portion  61 . The joint portion  61  is located between the first cloth  101  and the second cloth  102 . The joint portion  61  connects an end portion  106  of the cylindrical structure  60  in the first cloth  101  in the  8  direction and an end portion  107  of the cylindrical structure  60  in the second cloth  102  in the  8  direction. 
     The joint portion  61  includes an inner face  63  that is inside the cylindrical structure  60 . The joint portion  61  joins the first cloth  101  and the second cloth  102  such that a hollow  64  is formed between the first cloth  101  and the second cloth  102 . The cylindrical structure  60  generates an electric field between the first cloth  101  and the second cloth  102 . As a result, the cylindrical structure  60  can exert an antibacterial effect by the electric field generated in the hollow  64 . 
     When the joint portion  61  is made of a material that does not get electrified, the cylindrical structure  60  also generates an electric field at the joint portion  61 . That is, the cylindrical structure  60  also generates an electric field between the end portion  106  of the first cloth  101  and the end portion  107  of the second cloth  102 . Therefore, the cylindrical structure  60  can generate an electric field in a wider range than in the case where the joint portion  61  is not provided. As a result, the cylindrical structure  60  can exert an antibacterial effect in a wide range. 
     The joint portion  61  is preferably made of a material having a higher friction coefficient than the first cloth  101  and the second cloth  102 . When a user wears the cylindrical structure  60  on the body, for example, when the cylindrical structure  60  is attached to the arm, the inside of the cylindrical structure  60  comes into contact with the user&#39;s body. At this time, when the friction coefficient of the joint portion  61  is high, the inner face  63  of the joint portion  61  can exert an anti-slip effect on the user&#39;s body or the like. 
     When the cylindrical structure  60  receives a deforming force from the outside, the joint portion  61  is less likely to be deformed than the first cloth  101  and the second cloth  102  because it is difficult to slip on the user&#39;s body or the like. That is, when the cylindrical structure  60  receives a deforming force from the outside, the first cloth  101  and the second cloth  102  are more likely to be deformed than the joint portion  61 . As a result, the cylindrical structure  60  can deform the first cloth  101  and the second cloth  102  with a small force. Therefore, the first cloth  101  and the second cloth  102  can generate an electric field with a small force. 
     The stretchability of the joint portion  61  and the first cloth  101  and the second cloth  102  may be similar, but when the joint portion  61  is less stretchable than the first cloth  101  and the second cloth  102 , it is preferable that the joint portion  61  is formed from a woven fabric, and the first cloth  101  and the second cloth  102  are formed from knitted fabrics. For example, woven fabrics are usually less stretchable than knitted fabrics. When the joint portion  61 , the first cloth  101 , and the second cloth  102  are formed from knitted fabrics, the stretchability may be changed by changing the knitting structure. The joint portion  61 , which is difficult to stretch, restrains the end portion  106  of the first cloth  101  and the end portion  107  of the second cloth  102 . Therefore, when the cylindrical structure  60  receives a deforming force from the outside, the first cloth  101  and the second cloth  102  are greatly distorted as compared with the case of knitted fabric alone. As a result, the cylindrical structure  60  can efficiently generate an electric field when it receives a small force. 
     The joint portion  61  is preferably made of a material having a higher hydrophilicity than the first cloth  101  and the second cloth  102 , for example, ordinary thread. That is, the joint portion  61  is made of a material having a higher hydrophilicity than the first cloth  101  and the second cloth  102  containing PLLA. Because the joint portion  61  has a higher hydrophilicity than the first cloth  101  and the second cloth  102 , moisture easily permeates into the inside of the joint portion  61 . Therefore, the joint portion  61  easily absorbs moisture or fine particles. Therefore, the cylindrical structure  60  can easily take in moisture or fine particles into the joint portion  61  from the outside. In addition, the cylindrical structure  60  can easily take in moisture or fine particles from the outside into the hollow  64  through the joint portion  61 . Because of this, the cylindrical structure  60  can exert an antibacterial effect more efficiently than when a material having a low hydrophilicity is used for the joint portion  61 . 
     When the hydrophilicity of the joint portion  61  is high, moisture quickly wets and spreads inside the joint portion  61 . Moisture that has spread over a wide area inside the joint portion  61  has a large surface area and is easily vaporized. Usually, hydrophilic fiber aggregates have high drying properties. Because moisture evaporates quickly inside the joint portion  61 , the cylindrical structure  60  can quickly exert an antibacterial effect. 
     Hereinafter, a cylindrical structure  70  according to a third embodiment will be described.  FIG. 7(A)  is a perspective view showing a configuration of the cylindrical structure  70  according to the third embodiment, and  FIG. 7(B)  is a sectional view of the cylindrical structure  70  cut perpendicularly to the axial direction. In the description of the cylindrical structure  70 , only the points different from the cylindrical structure  10  of the first embodiment will be described, and the same points will be omitted. 
     As shown in  FIG. 7(A)  and  FIG. 7(B) , the cylindrical structure  70  has a plurality of first cloths  101  and second cloths  102 . The first cloths  101  face each other and the second cloths  102  face each other. Therefore, the cylindrical structure  70  can exert an antibacterial effect by an electric field generated between the first cloths  101  and the second cloths  102 . 
       FIG. 8(A)  is a perspective view showing a configuration of a cylindrical structure  80  according to a fourth embodiment, and  FIG. 8(B)  is a sectional view of the cylindrical structure  80  cut in the axial direction. In the description of the cylindrical structure  80 , only the points different from the cylindrical structure  10  of the first embodiment will be described, and the same points will be omitted. 
     As shown in  FIG. 8(A)  and  FIG. 8(B) , the cylindrical structure  80  has a plurality of first cloths  101  and second cloths  102 . Each first cloths  101  and each second cloths  102  are arranged alternately along the Z direction. The first cloths  101  and the second cloths  102  are slanted as shown by arrows  81  shown in  FIG. 8(B) . In this case as well, the cylindrical structure  80  forms an electric field between the first cloths  101  and the second cloths  102 . Therefore, the cylindrical structure  80  can exert an antibacterial effect by the electric field generated between the first cloths  101  and the second cloths  102 . 
     The cylindrical structure  10 , the cylindrical structure  60 , the cylindrical structure  70 , or the cylindrical structure  80  described above can be applied to various clothing or products such as medical components. For example, the cylindrical structure  10 , the cylindrical structure  60 , the cylindrical structure  70 , or the cylindrical structure  80  may be applied to masks, gloves, clothing, underwear (especially socks and belly bands), towels, headbands, wristbands, general sportswear, hats, bedclothes (including duvets, mattresses, sheets, pillows, and pillowcases), filters for water purifiers, air conditioners, and air purifiers, pet-related products (pet mats, pet clothes, pet inner clothes), various mats (for feet, hands, toilet seats, etc.), bags such as tote bags, laundry nets, packaging materials such as tangerine nets, seats (seats for cars, trains, planes, etc.), sofa covers, bandages, gauze, sutures, clothes for doctors and patients, supporters, sanitary goods, sports goods (clothes, inner gloves, gauntlets used in martial arts, etc.), artificial blood vessels, medical components for operations, and the like. 
     Finally, the description of this embodiment should be considered to be exemplary in all respects and not restrictive. The scope of the invention is indicated by the claims, not by the embodiments described above. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope of the claims. 
     DESCRIPTION OF REFERENCE SYMBOLS 
     
         
         
           
               10 ,  60 ,  70 ,  80 : Cylindrical structure 
               11 : First piezoelectric thread 
               12 : Second piezoelectric thread 
               61 : Joint portion 
               101 : First cloth 
               102 : Second cloth