Patent Publication Number: US-8534176-B2

Title: Method and apparatus for braiding micro strands

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the National Stage of International Application No. PCT/US2009/065156, filed Nov. 19, 2009, which claims the benefit of U.S. Provisional Application No. 61/199,699, filed Nov. 19, 2008. This application is related to U.S. patent application Ser. No. 12/065,697, filed on Oct. 9, 2008, which claims the benefit of PCT Patent Application Serial No. PCT/US2006/035028, filed Sep. 8, 2006, which claims the benefit of U.S. Patent Application Ser. No. 60/715,228, filed on Sep. 8, 2005, the disclosure of each of which is hereby incorporated by reference as if set forth in its entirety herein. 
    
    
     GOVERNMENT RIGHTS 
     This invention was made with U.S. government support under Contract Nos. NS054894 and NS044564 awarded by the National Institutes of Health (NIH). The U.S. government has certain rights in the invention. 
    
    
     BACKGROUND 
     Braids, also known as plaits, are complex structures or patterns formed by intertwining or interweaving a plurality of strands of flexible material. Conventional devices exist that are capable of braiding large strands for clothing, rope, decorative objects, hairstyles, and the like. These large strands are possess strength sufficient to absorb applied stresses during operation, for instance as the strands are unspooled during the braiding operation. Such stresses, however, would cause finer strands to fail. 
     What is therefore needed is a method and apparatus for braiding finer strands, such as strands of microfibers. 
     SUMMARY 
     A braiding device is provided that is suitable for making microbraids. The braiding device includes a first carrier including at least a first shelter, and a second carrier disposed proximate to the first carrier such that at least one of the carriers is movable with respect to the other carrier. The second carrier includes at least a second shelter. The braiding device includes at least one shuttle configured to retain one of a plurality of strands. A mover is configured to move the shuttle between the first and second shelters. The mover includes a first biasing member configured to impart a first retention force onto the shuttle that biases the shuttle against the mover, and one of the first and second carriers includes a second biasing member configured to impart a second retention force that biases the shuttle into the corresponding shelter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view of a braiding device including a plurality of braiding stations constructed in accordance with one embodiment. 
         FIG. 1B  is a perspective view of the braiding device illustrated in  FIG. 1A , during operation; 
         FIG. 1C  is a perspective view of a braiding device similar to the braiding device illustrated in  FIGS. 1A-B , but devoid of a core; 
         FIG. 2  is an enlarged perspective view of one of the braiding stations illustrated in  FIG. 1A ; 
         FIG. 3A  is a schematic top plan view of the braiding device illustrated in  FIG. 1A  at an initial stage of operation; 
         FIG. 3B  is a schematic top plan view of the braiding device similar to  FIG. 3A , but showing the braiding device at a first stage of operation; 
         FIG. 3C  is a schematic top plan view of the braiding device similar to  FIG. 3B , but showing the braiding device at a second stage of operation; 
         FIG. 3D  is a schematic top plan view of the braiding device similar to  FIG. 3C , but showing the braiding device at a third stage of operation; 
         FIG. 3E  is a schematic top plan view of the braiding device similar to  FIG. 3D , but showing the braiding device at a fourth stage of operation; 
         FIG. 3F  is a schematic top plan view of the braiding device similar to  FIG. 3E , but showing the braiding device at a fifth stage of operation; 
         FIG. 3G  is a schematic top plan view of the braiding device similar to  FIG. 3F , but showing the braiding device at a sixth stage of operation; 
         FIG. 3H  is a schematic top plan view of the braiding device similar to  FIG. 3G , but showing the braiding device at a seventh stage of operation; 
         FIG. 3I  is a schematic top plan view of the braiding device similar to  FIG. 3H , but showing the braiding device at a eighth stage of operation; 
         FIG. 4  is a side elevation view of a braided structure, braided about a form; 
         FIG. 5  is a top plan view of a braiding device constructed in accordance with an alternative embodiment; and 
         FIG. 6  is a top plan view of a braiding device constructed in accordance with another alternative embodiment. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     Referring to  FIG. 1A , a braiding device  20  is provided for producing microbraids, or braided strands  21  of micro fibers of the type described in U.S. patent application Ser. No. 12/065,697, filed on Oct. 9, 2008, the disclosure of which is incorporated by reference as if set forth in its entirety herein. For instance, the micro strands can be formed from any suitable flexible material such as textile, fiber, wire, spider or other silk strands, and the like on the order of scale of a human hair or finer. The strands can be electrically conductive. 
     For example, the braided strands may be provided as conductors that comprise metals, such as nichrome or stainless steel. Nichrome wires can be provided having an average diameter of 13 um. The conductors may also comprise conductive polymers such as lithium doped polyaniline and polyethylene dioxythiophene. In some embodiments, the conductors may comprise conductive proteins. In yet others, the conductors may be conductive nanotubes or nanofilaments, for example, carbon nanotubes or nanowires. These materials may be microscale, nanoscale, or combinations of both microscale and nanoscale materials. In some embodiments, the conductors may be hollow. In preferred embodiments, at least one conductor has a length that is at least 100 times greater than its diameter and, in some embodiments may be monofilaments. 
     The conductors can be insulated with a material such as with Teflon or Parylene C. The insulating material can be any polyimide or other electrical insulator. In embodiments of the present invention, the conductors may comprise intermittent insulation along the length of the conductors, providing a plurality of sites along the length of the braided structure for use in sensing or stimulation of the central or peripheral nervous system. 
     The braiding device  20  will now be described with initial reference to  FIG. 1A . As illustrated, the device  20  includes a first, or outer, carrier member  22  and a second, or inner, carrier member  24  disposed adjacent or proximate to the outer carrier member  22 . The carrier members  22  and  24  can be made from transparent glass or any suitable alternative material. In the illustrated embodiment, the outer carrier member  22  can be provided as a plate that defines a circumferentially inner end  31  that, in turn, defines a central cylindrical opening  26 . The inner carrier member  24  can be provided as a cylindrical plate that defines an outer cylindrical end  29  sized to fit within the opening  26 . The braiding device  20  can include a plurality of legs  25  that extend downward from the outer and inner carrier members  22  and  24  include and rest on a support surface  23 , which can be a floor or tabletop, or the like. 
     A radial gap  27  (for instance a quarter inch gap illustrated in  FIG. 2 ) can be disposed between the outer circumferential end  29  of the inner carrier member  24  and the radially inner end  31  of the outer carrier member  22 . The gap can allow the inner and outer carrier members to easily move relative to each other. As illustrated, the outer carrier member  22  is square plate dimensioned 24 inches by 24 inches or as otherwise desired, and the inner carrier member  24  can define a diameter of 10 inches or as otherwise desired. 
     The inner carrier member  24  defines a central hub  28  that is attached at its lower end to a motor  30  configured to rotate the inner carrier member  24  inside and relative to the outer carrier member  22 . The outer carrier member  22  can remain stationary as the inner carrier member  104  rotates in accordance with the illustrated embodiment. Alternatively, the outer carrier member  22  could rotate about the stationary inner carrier member  24 . Alternatively still, both carrier members  22  and  24  could rotate such that carriers rotate relative to one another. 
     The braiding device  20  further includes a plurality of shelters that allow for movement of the strands between locations at the outer carrier member  22  and locations at the inner carrier member  24 . The outer carrier member  22  supports a plurality of outer shelters  34  that are equidistantly spaced circumferentially about the opening  26 . As illustrated, six outer shelters  34  are equidistantly spaced on the outer carrier member  22  and circumferentially about the opening  106  such that 60° separates each shelter  34 . 
     As will be described in more detail below, the shelters  34  are divided into two groups of shelters  34 A and  34 B arranged in an alternating relationship such each shelter  34 A is disposed circumferentially between shelters  34 B, and each shelter  34 B is disposed circumferentially between shelters  34 A. Hence, each of the first group of shelters  34 A may be located at positions defined by angles 0°, 120°, and 240°, while each of the second group of shelters  34 B may be located at positions defined by angles 60° 180°, and 300°. 
     The inner carrier member  24  supports a plurality of inner shelters  42  that are equidistantly spaced circumferentially at the outer circumferential end  29  of the inner carrier member  24 . In accordance with the illustrated embodiment, the braiding device  20  includes twice the number of outer shelters  34  than inner shelters  42 . Thus, in the embodiment illustrated in  FIG. 1A , three inner shelters  42  are equidistantly spaced circumferentially about the radially outer end of the inner carrier member  104 , such that 120° separates each shelter  34 . Thus, the inner shelters  42  can be disposed at 0°, 120°, and 240° about the outer end  29  of the inner carrier member  24 . The inner carrier member  24  can thus be rotated to a position whereby the inner shelters  42  can be selectively radially aligned with the first group of shelters  34 A and the second group of shelters  34 B. 
     Referring now to  FIG. 2 , each outer shelter  34  constructed in accordance with the illustrated embodiment is provided as a groove  37  extending vertically through the outer carrier member  22 , and extending radially outward from the inner end  31  into the carrier member  22 . Thus, the groove  37  defines a proximal end  39  disposed at the inner end  31 , and terminates at a distal end  41  that is disposed radially outward with respect to the proximal end  39 . 
     Each inner shelter  42  is provided as a groove  43  extending vertically through the inner carrier member  24 , and extending radially outward from the radially outer end  29  into the inner carrier member  24 . Thus, the groove  43  defines a proximal end  45  that is disposed at the outer end  29 , and terminates at a distal end  47  that is disposed radially inward with respect tot the proximal end  45 . Thus, the proximal end  39  of each outer shelter  34  is configured to face the proximal end  45  of each inner shelter  42 . While the shelters  34  and  42  are illustrated as grooves extending into the associated carrier member, it should be appreciated that any alternative structure suitable for retaining strands to be braided during operation of the device  20  are contemplated. 
     The shelters  34  and  42  permit one of the carrier members to define an outer location of a first group of strands  21 , and the other carrier member to define an inner location of a second group of strands  21 . Accordingly, the first and second groups of strands can be braided as the inner carrier member  24  rotates relative to the outer carrier member  22 . 
     It should be appreciated in accordance with an alternative embodiment that the six shelters could be provided on the inner carrier member, and three shelters could be provided on the outer carrier member. Accordingly, one carrier member can include a number of shelters equal to the number of strands to be braided, while the other carrier member can include a number of shelters equal to one-half the number of strands to be braided. 
     The braiding device  20  further includes a plurality of transfer stations  32  that allow for movement of the strands  21  between the outer shelters  34  and radially aligned inner shelters  42 . Each transfer station  32  includes a shuttle  36  configured to retain one of the strands  21 , a mover  38  configured to move the shuttle  36  between radially aligned shelters  34  and  42 , and a force transfer member  40  configured to provide a biasing force to the mover  38  that cause the mover  38  to translate forward and backward, thereby moving the shuttle  36  between the radially aligned shelters  36  and  42 . 
     In the illustrated embodiment, the outer carrier member  22  includes a transfer station  32  operatively coupled to each outer shelter  34 . Thus, six transfer stations  32  are circumferentially disposed about the outer carrier member. The transfer stations  32  can be substantially identically constructed, such that a description of one transfer station  32  applies to all other transfer stations unless otherwise indicated. Each of the transfer stations  32  will now be described with respect to one of the transfer stations  32  illustrated in  FIG. 2 . 
     In particular, each shuttle  36  can be provided as a metallic grommet including a body  50  that defines an opening  52  extending vertically through the body  50 , and a flange  54  extending radially out from the upper end of the body  50 . The opening  52  can be cylindrical, and can have a diameter between about 0.5 inch and about 2 inches, for instance approximately 1 inch. It should be appreciated that the geometry of the shuttle  36  can be configured to minimize fiber stress. The flange  54  is sized greater than the circumferential thickness of the grooves that define the shelters  34  and  42 , and is configured to rest on the upper surface of the carrier members  22  and  24  under gravitational forces. If desired, a second flange can extend radially out from the bottom end of the body  50  such that the pair of vertically spaced flanges captures the carrier members  24  and  24  therebetween. The body  50  can be cylindrical, and has a thickness or diameter that is less than the circumferential thickness of the grooves that define the shelters  34  and  42 . Accordingly, when the shuttle  36  is disposed at one of the shelters  34  or  42 , the body  50  extends vertically below the flange  54  and through the groove that corresponds to the shelter. The shuttle  36  can then translate along and between radially aligned shelters  34  and  42 , thereby moving the retained strand  21  between the outer carrier member  22  and the inner carrier member  24 . 
     Each transfer assembly  32  further includes a mover  38  mounted onto a rectangular support housing  56 . The support housing  56  defines opposing radially inner and outer end walls  58  and  60 , and opposing upper and lower walls  62  and  64 , respectively, and opposing side walls  66  extending between the inner and outer end walls  58  and  60 . Both the mover  38  and the housing  56  are radially elongate, and the mover is slidably mounted onto the upper wall  62  of the housing  56 . The mover  38  defines a groove  68  that extends vertically through the upper surface of the mover  38 . The groove  68  is radially elongate in a direction parallel to the corresponding outer shelter  34 . The groove  68  extends between a radially inner end  67  and a radially outer end  69 . 
     The upper wall  52  further carries a pair of guide members  70  that are radially aligned in a direction parallel with respect to the corresponding shelter  34 . In the illustrated embodiment, the guide members  70  are aligned with the corresponding shelter  34 . Each guide member  70  includes central rod  71  extending through an aperture  73  that extends vertically through the outer carrier member  22 . Thus, the position of the rod  71  is fixed with respect to the outer carrier member  22 . A lower nut  74  and an upper nut  76  are carried by the rod  71 , such that the outer carrier member  22  is captured between the nuts  74  and  76 . 
     The rod  71  further extends into the groove  68 , and has a diameter substantially equal to the thickness of the groove  68  such that the pair of guide members  70  permits the mover to slide radially as the groove  68  passes along the rods  71 . Thus, the mover  38  is slidable with respect the support housing  56  and the outer carrier member  22 . In particular, the mover  38  is slidable between a first retracted, or radially inward, position whereby a magnet  97  carried by the mover  38  is aligned with the outer shelter  34 , and a second extended, or radially outward, position whereby the magnet is aligned with the inner shelter  42 . 
     The transfer station  32  further includes a force transfer member  40  supported by the outer carrier member  22  via a support rod  80  that carries upper and lower nuts  82  that capture the outer carrier member  22  therebetween. The force transfer member  40  includes a drive mechanism  83  illustrated as including a force transfer motor housing  84  that retains a stepping motor, and a rotating drive shaft  86  extending vertically up from the housing  84 . 
     The drive shaft  86  carries a drive mechanism  88  in the form of a pinion that presents teeth  90  that intermesh with complementary teeth  92  of a rack  94  that extends radially along the side wall of the mover  28 . The drive shaft  86  and pinion  88  is rotatable about a vertical axis, for instance in a first direction (clockwise as illustrated) that causes the mover  38  to translate in a radially inward direction toward the aligned inner shelter  42 , while rotation of the pinion  88  in an opposing second direction (counterclockwise as illustrated) causes the mover  38  to translate in a radially outward direction away from the aligned inner shelter  42 . The maximum stroke length of the mover  38  can be configured as desired based, for instance, on the radial lengths of the shelters  34  and  42 . 
     While the force transfer member  40  has been illustrated and described in accordance with one embodiment, it should be appreciated that the force transfer member could be constructed in accordance with numerous alternative configurations that allow the mover  66  to translate with respect to the outer carrier member  22 . For instance, mover  38  could include a rotatable pinion that intermeshes with a rack supported by the outer carrier member  22 . 
     With continuing reference to  FIG. 2 , the radially inner end wall  58  of the mover  38  carries a biasing member  96  can be provided as a magnet  97 , such as a permanent magnet, that is configured to apply a retention force onto the shuttle  36 . The magnet  97  can be attached to the radially inner surface of the end wall  58  external to the mover  38 , or can be attached to the radially outer surface of the end wall  58  insider the mover  38 , which can be made from a plastic that allows the magnetic field from the magnet  97  to pass through. The magnet  97  can be positioned in vertical alignment with the body  50  of the shuttle  36 , such that the magnet  97  can provide a biasing retention force that force that biases the body  50  in a radially outward direction against the radially inner end wall  58  of the mover  38 . 
     The inner carrier member  24  also includes a biasing member  100  associated with each of the inner shelters  42 . The biasing member  100  can be provided as a magnet  102 , such as a permanent magnet, extending down from the undersurface of the inner carrier member  24  at a location in alignment with the corresponding shelter  42  at a location radially inward of the radially inner end  47  of the shelter  42 . The magnet  102  is vertically aligned with the body  50  of the shuttle  36 , and is thus configured to apply a retention force onto the body  50  that biases the body radially inward direction. 
     A vertical dampening wall  104  can extend down from the inner carrier member  24  at a location between the magnet  102  and the corresponding shelter  42 . The wall  104  can be made of a nonmagnetic material, and can dampen the magnetic force of the magnet  102  that passes through the wall  104 . In this regard, the vertical wall  104  provides a dampener that reduces the magnetic force provided by the magnet  102 , such that the corresponding retention force that acts on the shuttle  36  from the magnet  102  is less than the retention force that acts on the shuttle  36  from the magnet  97 , even when the magnets  97  and  102  are similarly constructed with the same magnetic force. Alternatively, the inner carrier member  24  can be devoid of dampeners, and the magnet  102  can be constructed to provide a reduced magnetic force with respect to the magnet  97 . 
     As will be more appreciated from the description below, when the shelter  34  is aligned with an inner shelter  42 , the transfer station  32  can iterate or “push” the shuttle  36 , and thus the retained strand  21 , from a first radially outward position in the outer shelter  34  to a second radially inward position in the inner shelter  42 . Furthermore, because the magnet  97  of the transfer station  32  applies a biasing force onto the shuttle  36  that is greater than the biasing force applied from the magnet  102  of the inner shelter  42  onto the shuttle  36 , the transfer station  32  can likewise iterate, or “pull” the shuttle  36  radially outward from the inner shelter  42  into the outer shelter  34 . 
     Referring now to  FIGS. 1A-B  and  FIG. 4 , the strands  21  to be braided can be supported at a location above the inner carrier member  24  at the center of the carrier member  24 , at a position in radial alignment with each shelter  34  and  42 . For instance, a central shaft that can provide a core holder  110  extends up from the motor  30 , and is attached to a substantially cylindrical braiding core  112  about which the strands  21  can be braided. The strands  21  each define a proximal end  51  attached to the braiding core  112 , a terminal distal end  53 , and a middle portion  55  disposed between the proximal and distal ends. The middle portion  55  of each strand  21  extends through a corresponding shuttle  36 , and the distal end  53  of each strand  21  can be fastened to a small weight  35 , such as tape, clay, or the like, that induces tension in the strands  21  that is sufficient to prevent slack from occurring in the strands  21 , but insufficient to break the strands  21 . Accordingly, the legs  25  are of a sufficient height such that the distal end  53  of each strand  21  is suspended above the support surface  23 . It should thus be appreciated that one or more, up to all, of the strands  21  can be spool-less. Otherwise stated, the braiding device  20  can be devoid of spools while at the same time ensuring sufficient tension in the strands  21  without causing the strands  21  to fail. 
     The braiding device  20  can be referred to as a micro braiding device suitable for braiding strands  21  of microfibers that have a diameter or thickness between about 0.3 mm and about 600 nm. For instance, the strands  21  can have average diameters on the order of from about 0.1 mm to about 50 um. In other applications, average strand diameters can range from about 0.1 mm to about 1 um, such as about 13 um. It should be appreciated, of course, that while the braiding device  20  is capable of braiding strands of microfibers as described above, a braiding device of the type describer herein is further capable of braiding strands of any desired composition and diameter. 
     The strands  21  spaced circumferentially equidistantly about the device  20 , and each strand  21  extends through a corresponding shuttle  36 . The strands  21  are divided into two groups of strands  21 A and  21 B arranged in an alternating relationship such that each strand  21 A is disposed circumferentially between strands  21 B, and each strand  21 B is disposed circumferentially between strands  21 A. Hence, each of the first group of strands  21 A may be located at positions defined by angles 0°, 120°, and 240°, while each of the second group of strands  21 B may be located at positions defined by angles 60°, 180°, and 300°. Likewise, the shuttles  36  are divided into two first and second respective groups of shuttles  36 A and  36 B that retain the first and second groups of strands  21 A and  21 B, respectively. 
     A method for operating the braiding device to fabricate a microbraid structure will now be described with initial reference to FIGS.  1  and  3 A-M. Throughout the description of the method of operation below, a description of the position of the shuttles  36 A and  36 B likewise pertains to position of the strands  21 A and  21 B retained therein. In particular, as illustrated in  FIGS. 1A and 3A , when the device  20  is in an initial position, the first group of shuttles  36 A and the second group of shuttles  36 B are disposed in a first radially outward position in the first group of outer shelters  34 A and the second group of outer shelters  34 B, respectively, of the outer carrier member  22 . Each strand  21  is then attached at its proximal end to the upper end of the braiding core  112 , and fed through the opening of its associated shuttle  36 , and provided with a weight  35  in the manner described above. The shelters  42  are then radially aligned with the first group of shelters  34 A, while the second group of shelters  34 B is not radially aligned with any inner shelters  42 . 
     Referring to  FIGS. 1 and 3B , the method iterates the braiding device  20  to a first position, whereby the pinions  88  associated with the first group of transfer assemblies  32 A are driven in a predetermined direction (clockwise as illustrated) that causes the corresponding mover  38  to translate radially inwardly. Each mover  38  thus correspondingly translates or “pushes” the associated shuttle  36 A radially inwardly along the direction of Arrow A from the shelter  34 A, across the gap  27  that separates the carrier members  22  and  24 , and along the aligned inner shelter  42  until each mover  38  reaches a second position, whereby the associated shuttle  36 A (and strand  21 A extending through the shuttle  36 A) is delivered to the radially inner end of the shelter  42 . The gap  27  has a thickness less than the diameter of the body  50  of the shuttle  36 A such that each shuttle  36 A remains in its proper position as it crosses between shelters  34 A and  42 . Thus, both the mover  38  and the retention forces of the magnets  102  stabilize the shuttles  36 A in the radially inner ends of the shelters  42 . As the first group of shuttles  36 A is delivered to the aligned shelters  42 , each of the first group of strands  21 A “crosses over” the second group of strands  21 B. 
     Next, referring to  FIGS. 1 and 3C , the method iterates the braiding device to a second position, whereby the inner carrier member  24  is rotated relative to the outer carrier member  22  in a first direction along the direction of Arrow B, which is clockwise as illustrated in  FIG. 3C . It should be appreciate that the first direction could alternatively be counterclockwise if desired. The carrier member  22  is rotated 120° such that the inner shelters  42  and retained shuttles  36 A become radially aligned with the subsequent shelters of the first group  34 A in clockwise sequence. As the inner carrier member rotates 120° clockwise, each of the first group of strands  21 A is intertwined with each of the second group of strands  21 B. The motor  30  that rotates the inner carrier member  24  and the motors  84  that drive the movers  38  can be controlled by a controller or PC software. 
     It should be appreciated that as the inner carrier member  24  rotates, the first group of shuttles  36 A disposed in the shelters  42  moves tangentially with respect to the magnets  97  carried by the movers  38  of the first transfer station  32 A. Because the radial retention force of the magnets  102  associated with the shelters  42  is greater than the tangential retention force provide by the magnets  97  of the transfer stations  32 A, the shuttles  36 A become disengaged from the movers  38  as the inner carrier member  24  rotates relative to the outer carrier member  22 . Furthermore, the movers  38  can remain in place as the forces exerted by the rotating carrier member  24  overcome the magnetic attraction of the transfer assembly  32 . Alternatively, if desired, the mover  38  of the first group of transfer stations  32 A can retract radially outward if desired as the inner carrier member  24  rotates to avoid possible interference between the magnets  97  of the transfer assembly  32 A and the rotating shuttles  36 A. 
     Next, referring to  FIG. 3D , once the inner carrier member  24  has completed the 120° rotation, the shuttles  36 A are again aligned with the movers  38  of the first transfer stations  32 A. If the movers  38  remained positioned at their radially innermost positions illustrated in  FIG. 3B , then the shuttles  36 A are brought into contact with the magnets  97  carried by the movers  38 . Alternatively, if the movers  38  are retracted radially outward upon rotation of the inner carrier member  24 , then the movers are extended radially inward after rotation of the inner carrier member  24  until the magnets  97  are brought into contact with the shuttles  36 A. The movers  38  of the first group of transfer stations  32 A are then retracted radially outward along the direction of Arrow C. Because the radial retention force of each magnet  97  is greater than the radial retention force of each magnet  102 , retraction of the movers  38  of the first group of transfer stations  32  causes the associated shuttles  36 A to become disengaged from the magnets  102  and move radially outward along with the movers  38 . The movers  38  associated with the transfer stations  32 A thus “pull” the shuttles  36 A from the shelters  42  to the shelters  34 A. It should be appreciated that the shuttles  36 A are positioned in different shelters  34 A of the second group of shelters  34 A with respect to the initial shelter that the shuttles  36 A were disposed in prior to being moved into the shelters  42 . 
     Next, referring to  FIG. 3E , once the shuttles  36 A are disposed in the shelters  34 A, such that the inner shelters  42  are devoid of shuttles, the inner carrier member  24  is then rotated 180° in a second direction (counterclockwise as illustrated) along the direction of Arrow D, which is opposite the direction of Arrow B. It should be appreciated that the second direction could alternatively be clockwise if so desired. After the inner carrier member  24  has completed the 180° rotation, each of the second group of shuttles  36 B that carry the second group of strands  21 B is radially aligned with inner shelters  42 . The movers  38  associated with the transfer stations  32 B are disposed in a first radially outward position such that the magnet  120  is aligned with the shelter  34 B. 
     Next, referring to  FIG. 3F , the pinions  88  associated with the second group of transfer assemblies  32 A are driven in a predetermined direction (clockwise as illustrated) that causes the corresponding movers  38  to translate radially inwardly. Each mover  38  thus correspondingly translates or “pushes” the associated shuttle  36 B radially inwardly along the direction of Arrow A from the shelter  34 B, and along the aligned inner shelter  42  until each mover  38  reaches a second position, whereby the associated shuttle  36 B (and strand  21 B extending through the shuttle  36 B) is delivered to the radially inner end of the shelter  42 . Thus, both the mover  38  and the retention forces of the magnets  102  stabilize the shuttles  36 B in the radially inner ends of the shelters  42 . As the second group of shuttles  36 B is delivered to the aligned shelters  42 , the each of the second group of strands  2 B “crosses over” the first group of strands  21 A. 
     Next, referring to  FIG. 3G , the inner carrier member  24  is rotated relative to the outer carrier member  22  in a first direction along the direction of Arrow B, which is clockwise as illustrated in  FIG. 3G . It should be appreciate that the first direction could alternatively be counterclockwise if desired. The carrier member  22  is rotated 120° such that the inner shelters  42  and retained shuttles  36 B become radially aligned with the subsequent shelters of the first group  34 B in clockwise sequence. As the inner carrier member  24  rotates 120° clockwise, each of the second group of strands  21 B is intertwined with each of the first group of strands  2 A. 
     It should be appreciated that as the inner carrier member  24  rotates, the second group of shuttles  36   b  disposed in the shelters  42  moves tangentially with respect to the magnets  97  carried by the movers  38  of the second transfer station  32 B. Because the radial retention force of the magnets  102  associated with the shelters  42  is greater than the tangential retention force provide by the magnets  97  of the transfer stations  32 B, the shuttles  36 B become disengaged from the movers  38  as the inner carrier member  24  rotates relative to the outer carrier member  22 . Furthermore, the movers  38  can remain in place as the forces exerted by the rotating carrier member  24  overcome the magnetic attraction of the transfer assembly  32 B. Alternatively, if desired, the movers  38  of the second group of transfer stations  32 B can retract radially outward if desired as the inner carrier member  24  rotates to avoid possible interference between the magnets  97  of the transfer assembly  32 B and the rotating shuttles  36 B. 
     Next, referring to  FIG. 3H , once the inner carrier member  24  has completed the 120° rotation, the shuttles  36 B are again aligned with the movers  38  of the second transfer stations  32 B. If the movers  38  remained positioned at their radially innermost positions, then the shuttles  36 B are brought into contact with the magnets  97  carried by the movers  38 . Alternatively, if the movers  38  are retracted radially outward upon rotation of the inner carrier member  24 , then the movers  38  are extended radially inward after rotation of the inner carrier member  24  until the magnets  97  are brought into contact with the shuttles  36 B. The movers  38  of the second group of transfer stations  32 B are then retracted radially outward along the direction of Arrow C. Because the radial retention force of each magnet  97  is greater than the radial retention force of each magnet  102 , retraction of the movers  38  of the second group of transfer stations  32 B causes the associated shuttles  36 B to become disengaged from the magnets  102  and move radially outward along with the movers  38 . The movers  38  associated with the transfer stations  32 B thus “pull” the shuttles  36 B from the shelters  42  to the shelters  34 B. It should be appreciated that the shuttles  36 B are positioned in different shelters  34 B of the second group of shelters  34 B with respect to the initial shelter that the shuttles  36 B were disposed in prior to being moved into the shelters  42 . 
     Finally, referring to  FIG. 3I , once the shuttles  36 B are disposed in the shelters  34 B, such that the inner shelters  42  are devoid of shuttles, the inner carrier member  24  is then rotated 180° in the second direction (counterclockwise as illustrated) along the direction of Arrow D. After the inner carrier member  24  has completed the 180° rotation, each of the first group of shuttles  36 A that carry the first group of strands  21 A is radially aligned with inner shelters  42 . Accordingly, the steps illustrated in  FIGS. 3A-3D  can be repeated to cross the first group of strands  21 A over the second group of strands  21 B, step  3 E can be repeated to align the inner shelters  42  with the second group transfer stations  32 B, and steps  3 F- 3 I can be repeated to cross the second strands  21 B over the first group of strands  21 A. These method steps can be repeated as desired until the braiding method is completed. 
     It should thus be appreciated that the braiding device  20  includes a pair of biasing members (e.g., springs  97  and  102 ) configured to iteratively move a first group of strands  21 A to be braided from a first position that is circumferentially aligned with a second group of strands  21 B to be braided, to a second position circumferentially offset with respect to the second group of strands, and subsequently return the first group of strands  21  to the first position. Furthermore, the pair of biasing members is configured to iteratively move the second group of strands  21 B from the first position to the second position circumferentially offset with respect to the first group of strands  21 A, and subsequently return the second group of strands  21 B to the first position. 
     Referring now to  FIGS. 1A-B  and  4 , the core holder  110  and core  112  are movably mounted onto the motor  30 . In particular, the motor  30  can provide a linear actuator that, translates the core  112  vertically upward along the direction of Arrow V during the braiding method described above. Thus, when the braiding method begins, the core  112  is in a vertically depressed position, and the strands  21  are attached to the upper end of the core. As the core  112  translates vertically upward during operation, the strands  21  are braided successively down the length of the core  112  to define a braided structure  122 . It should be appreciated that the vertical distance that separates successive turns of each strand  21  of the braided structure  122  in combination with the form diameter defines a braid pitch P. The braid pitch P increases as the speed of vertical translation of the core  112  increases during the braiding operation. The braid pitch P decreases as the speed of vertical translation of the core  112  decreases during the braiding operation. 
     It should be appreciated that the angle between the strands  21  and the core  112  tends to gradually increase during the braiding operation without adjusted translation of the core. As a result, the pitch P tends to gradually decrease along the braided structure. Accordingly, the braiding device  20  can include a linear actuator that adjusts the height of the core holder according to time during the braiding operation such that the braided structure can have an equal or substantially equal pitch along the braided structure  122 . 
     In the illustrated embodiment, the core holder  110  receive the core  112  such that the core  112  extends vertically up from the core holder if, for instance, the strands  21  are to be braided about a core. Alternatively, as illustrated in  FIG. 1C , the strands  21  can be braided with no core. In particular, the braiding device  20  is constructed similar to  FIGS. 1A-B , however the proximal ends  51  of the strands  21  are fixed to a cantilevered support  300 . The support  300  includes a leg  302  that can extend up from a fixed location, such as the outer carrier member  22 . The leg  302  is connected at its upper end to a boom  304  that extends radially to a location above the inner carrier member  24 , and terminates at a location coincident with the axis of rotation of the inner carrier member  24 . An attachment rod  306  extends down from the distal end of the boom  304  toward the inner carrier member  24 , and defines a distal and  307  that provides an attachment location that is suspended above the inner carrier member to which the proximal ends  51  of the strands  21  are attached. The rod  36  can include an outer rod portion  308  extending down from the boom  304 , and a telescoping inner rod portion  310  nested in the outer rod portion  308  and extending down from the outer rod portion  308 . A motor (not shown) can cause the inner rod portion  310  to move vertically upward along the direction of Arrow V relative to the outer rod portion  308 , and also relative to the carrier members  22  and  24 . Accordingly, as the inner rod portion  310 , and thus the attachment location  307  is translated upward during operation of the braiding device  20  in the manner described above, the strands  21  are braided below the inner rod portion  310  without a core. 
     While the braiding device  20  is described with reference to a capability of providing a symmetrical braid structure with six strands  21 , it should be appreciated that the principles of the illustrated embodiment are applicable to braiding any number of strands as desired. By way of example, the device  20  includes six outer shelters  34  corresponding to six strands to be braided, and three inner shelters  42  corresponding to the size of the two groups of strands. However, if it is desired to braid a greater or lesser number of strands  21 , carrier member  104  can be provided with a number of shelters corresponding to the number of strands to be braided, and the inner carrier member  104  can be provided with half the shelters as the outer carrier member  102 . 
     For instance,  FIG. 5  illustrates a braiding device  120  constructed in accordance with an alternative embodiment, whereby reference numerals corresponding to like structure of the braiding device are incremented by 100. The braiding device  120  is identically constructed as described above with respect to the braiding device  20 , however the device  120  is configured to braid four strands  221  about the core  212  as a tetrode, and thus includes four outer shelters  134  and two inner shelters  142 . Accordingly, the braiding device  120  is configured to provide a four-strand braided structure, also referred to as a tetrode. 
     Embodiments also contemplate that multiple braided structures  122  can be provided in sequence on the same core  112 . For instance, a plurality of tetrodes can be created by the braiding device  120 , and each tetrode can be braided into a multi-tetrode structure. In one embodiment, four tetrodes can be created using the device  120 , and each tetrode can be braided into a four-tetrode braided structure. 
     Referring to  FIG. 6 , it should be appreciated that a microbraiding device  20 ′ constructed in accordance with another embodiment can be expandable. The device  20 ′ constructed in accordance with the structure and methods described above includes the inner carrier member  24 , and the outer carrier member  22  is replaced with a ring of discrete individually rotatable outer carrier members  24 A tangential to each other and to the inner carrier member  24 . The carrier members  24  and  24 A can have any number of transfer stations and shuttles as desired. The device  20 ′ can further comprise second outer ring of outer carrier members  24 B, in addition to any number of additional outer rings of carrier members as desired. Thus, it should be appreciated that the device  20 ′ is expandable to include as many strands to be braided as desired. As illustrated, each carrier member  24 ,  24 A, and  24 B includes three shuttles  36  that iterate between six equidistantly spaced transfer stations and shelters in the manner described above. Accordingly, the shuttles can deliver the corresponding strands between adjacent carrier members  24 ,  24 A, and  24 B, and can further deliver the strands between adjacent outer carrier members of a given ring. The device  20 ′ can operate in any desired sequence to create a braided structure as the carrier member  24  and rings of carrier members  24 A and  24 B rotate relative to each other as the shuttle  36  are transferred between carrier members. 
     While embodiments have been shown in the figures, it is to be understood that other similar embodiments may be used or modifications and additions may be made to the described embodiment without deviating from the spirit and scope of the subject matter recited in the appended claims. Therefore, the following claims should not be deemed limited to the illustrated embodiment, but rather should be construed in breadth and scope to encompass all such variations and modifications to the disclosed embodiment