Abstract:
A skin attachment member of plastic resin, includes a sheet-form backing, and an array of skin penetrating elements extending integrally from the backing. The skin penetrating elements are configured to penetrate into the epidermal skin layer and are sized to limit painful contact with nerves below the epidermal skin layer. At least many of the skin penetrating elements each include at least one retention barb extending from an outer surface of the skin penetrating element. The barbs are configured to cooperate to resist removal of the skin attachment member from skin. The skin penetrating elements have a cone-shaped body with a pointed tip. The skin penetrating elements can have a groove in their outer surface. The skin attachment member is formed by molding.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The invention relates to an attachment member for securing objects to skin.  
         [0002]     A patch with an array of microneedles which penetrate into the stratum corneum is known. The microneedles are made out of silicon using the same etching process used to manufacture computer chips.  
       SUMMARY OF THE INVENTION  
       [0003]     The attachment member of the invention, formed of plastic resin, includes a base layer from which extend an array of many tiny, integral skin-penetrating plastic elements having one or more barbs which lodge in the skin and resist removal of the attachment member. The member is configured such that the elements securely fasten to the skin without penetrating deeply enough to cause pain and discomfort.  
         [0004]     According to one aspect of the invention, a skin attachment member of plastic resin includes a sheet-form backing, and an array of skin penetrating elements extending integrally from the backing. The skin penetrating elements are configured to penetrate into the epidermal skin layer and are sized to limit painful contact with nerves below the epidermal skin layer. At least many of the skin penetrating elements each includes at least one retention barb extending from an outer surface of the skin penetrating element. The barbs are configured to cooperate to resist removal of the skin attachment member from skin.  
         [0005]     Embodiments of this aspect of the invention may include one or more of the following features.  
         [0006]     Each skin penetrating element has a cone-shaped body. The base of the cone-shaped body has a diameter of about 0.003″. Each skin penetrating element has a length of about 0.012″ and a pointed tip. The backing has a thickness in a range of about 0.003″ to 0.008″.  
         [0007]     In an illustrated embodiment, the retention barb is located about 0.008″ to 0.0095″ along a length of the skin penetrating element from the backing, has a length of about 0.0001″, and tapers from a thickness of about 0.0001″ to a point at an angle of about 72°. Each skin penetrating element includes, e.g., two barbs.  
         [0008]     The skin attachment member has a density of about 400 skin penetrating elements in a 0.01 in 2  area, i.e., 40,000/in 2 . The skin penetrating elements are spaced apart from each other a distance of about 0.003″.  
         [0009]     The skin attachment member is formed from nylon, polyethylene teraphthalate, or polyester. The skin attachment member is formed by molding.  
         [0010]     In an illustrated embodiment, at least many of the skin penetrating elements define at least one groove in an outer surface of the skin penetrating elements. The skin penetrating elements are oriented perpendicular to the backing.  
         [0011]     Other features and advantages of the invention will be apparent from the following description, and from the claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a highly magnified side view of a section of a skin attachment member according to the invention shown secured in the epidermis;  
         [0013]      FIG. 2  is a diagrammatic perspective view of the section of the skin attachment member of  FIG. 1 ;  
         [0014]      FIG. 3A  is a side view of a skin-penetrating element of the skin attachment member of  FIG. 1 ;  
         [0015]      FIG. 3B  is a another side view of the element of  FIG. 3A , rotated 90 degrees relative to  FIG. 3A ;  
         [0016]      FIG. 3C  is an end view of the element of  FIG. 3A  taken along lines  3 C- 3 C in  FIG. 3A ;  
         [0017]      FIG. 3D  is a cross-sectional view of the element of  FIG. 3A  taken along lines  3 D- 3 D in  FIG. 3B ;  
         [0018]      FIG. 4  is a perspective view of section A of  FIG. 3B  showing a barb of the element of  FIG. 3A ;  
         [0019]      FIG. 5  shows an alternative embodiment of a barb;  
         [0020]      FIG. 6A  is a diagrammatic representation of a molding machine for forming the skin attachment member of  FIG. 1 ;  
         [0021]      FIG. 6B  shows a mold roll, pressure roll, and trim roller of the molding machine of  FIG. 6A ;  
         [0022]      FIG. 6C  is an enlarged view of the mold roll and pressure roll of the molding machine;  
         [0023]      FIG. 7A  is a side view of the mold roll of  FIG. 6A ;  
         [0024]      FIG. 7B  is a cross-sectional view of the mold roll, taken along lines  7 B- 7 B in  FIG. 7A ;  
         [0025]      FIG. 7C  is an end view of the mold roll, taken along lines  7 C- 7 C in  FIG. 7B ;  
         [0026]      FIG. 7D  is a magnified side view of portion  7 D of the mold roll of  FIG. 7A ;  
         [0027]      FIG. 7E  shows laser machining of the mold roll; and  
         [0028]      FIG. 8  shows an alterative edge formation on a mold roll. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]     Referring to  FIGS. 1 and 2 , a skin attachment member  10 , formed of plastic resin, includes a backing  12  and multiple, parallel rows of integrally molded, pointed projections or elements  14  extending from backing  12  for penetrating into the epidermis  16 . The skin-penetrating elements  14  each include a cone-shaped body  18  with one or more discrete barbs  20  extending from the body for securing skin attachment member  10  to epidermis  16 .  
         [0030]     The length of elements  14  is selected such that they do not penetrate so far into the skin as to contact nerves located below the outer layers of the epidermis, as to cause significant pain and discomfort, but are long enough to cooperate with each other to provide sufficient adhesion to the skin. Elements  14  can be sized to extend into the portion of skin lying below the stratum corneum layer of the skin because of the small size of elements  14  and the spacing between nerves at this depth. For example, referring also to  FIG. 3A , plastic elements  14  have a length, L, of about 0.012″. Since the thickness of the epidermis varies, for example, with age, the location on skin, and the gender of the patient, the length of elements  14  can be selected for the particular use.  
         [0031]     Cone  18  tapers from a larger diameter proximal base  22  to a distal pointed tip  24 . The conical shape and sharp point of elements  14  ease their penetration into epidermis  16 . The diameter of base  22  is selected to be large enough to help prevent breaking off of the projecting elements  14  from backing  12 , while limiting the size of the opening made in the outer surface  16   a  of epidermis  16 . For example, cone  18  has a base diameter, D, of about 0.003″. Backing  12  has a thickness, T, in a range of about 0.003″ to 0.008″ to provide member  10  with sufficient handling characteristics.  
         [0032]     The skin-penetrating projecting plastic elements  14  can be other than conical in shape. For example, elements  14  can be in the shape of a pyramid, a tetrahedron, or may be elliptical or square in cross-section, tapering to points at their distal ends. Rather than taper distally, elements  14  can progressively step down in diameter. Regardless of the particular shape selected, the elements  14  include sharp pointed tips  24  to ease tissue penetration.  
         [0033]     Referring to  FIGS. 4A and 4B , projecting elements  14  are shown with two discrete barbs  20   a ,  20   b  for retaining elements  14  in the skin, though fewer or more barbs can be disposed on cone  28  to provide the desired retention characteristics. The location of barbs  20  can be selected to take advantage of the greater elasticity of the skin portions lying below the stratum corneum to provide greater holding force. For example, barb  20   a  has a top surface  23   a  located a distance, d 1 , of about 0.008″ from base  22 , and barb  20   b  has a top surface  23   b  located a distance, d 2 , of about 0.0095″ from base  22 .  
         [0034]     Referring to  FIG. 4 , which is an enlarged view of section A of  FIG. 3B , barbs  20   a ,  20   b  are roughly half-pyramids, each having a flat upper surface  23   a  which is perpendicular to a longitudinal axis, A, of the projecting element  14 , and sloped sides  28   a ,  28   b . Barbs  20   a ,  20   b  have a length, l, of about 0.0001″, and a thickness, t ( FIG. 3   d ), of about 0.0001″, which tapers to a point  26  at an angle, α, of about 72°.  
         [0035]     In use, due to the elasticity of the skin, member  10  is secured to skin surface  16   a  by surrounding of the barbs by the epidermis. To improve retention of member  10  to the skin, the barbs can be angled as shown in  FIG. 5 . Here, a barb  20   c  has a sloped upper surface  23   c.    
         [0036]     The density of projecting elements  14  on backing  12  depends on use. For example, in high strain applications, a higher density provides better skin attachment, whereas, in applications in which member  10  is not subjected to high strain, a lower density is better for limiting the possibility of inflammation. If the density is too high, it can require too much force for elements  14  to penetrate into the skin. A density of 400 projecting elements in a 0.1 in 2  area provides good skin attachment while not requiring excessive insertion force. In this case the projecting elements  14  are preferably spaced apart a distance, d ( FIG. 1 ), of about 0.003″.  
         [0037]     Member  10  and its projecting elements  14  are preferably formed from a thermoplastic, biocompatible polymer, which is stiff enough to penetrate skin but not brittle, and capable of filling a mold and retaining its molded form. Example of suitable polymers include nylon, polyethylene teraphthalate, and polyester.  
         [0038]     Referring to  FIGS. 3C and 3D , if desired for use in, for example, drug delivery, the projecting elements  14  include longitudinal grooves  30  in an outer surface  32  of cone  18 , here four grooves  30  being shown, which provide passages for drug delivery. The penetration of elements  14  into the epidermis facilitates the delivery of drugs through the epidermis by reducing the thickness of the skin barrier to the vascular layer below the epidermis.  
         [0039]     Other uses of member  10  include securing an intravenous or other catheter to the skin, such as securing in place a port for peritoneal dialysis, thus replacing a suture or a butterfly or acting secondary to a suture, acting as bandaid type wound closure to hold two sections of skin together, as wound covering, as a delivery system for self-delivery of drugs, in vetinary applications, as a reaction indicator, for time release vaccination, in agricultural applications such as bundle ties limiting damage to produce, and in geotextile applications. Incorporated in the polymer from which member  10  is formed can be bacteria killing agents or medication.  
         [0040]     Skin attachment member  10  can be molded as a continuous strip  10 ′ according to the principles described in Fischer, U.S. Pat. No. 4,794,028, hereby incorporated by reference.  
         [0041]     For example, referring to  FIGS. 6A-6C , a molding machine  40  includes an extruder  42  which delivers an extrusion of molten plastic material between a pair of rollers  44 ,  46  mounted for rotation in opposite directions. Roller  44  is a cooled mold roll having a set of stacked parallel plates  48  ( FIG. 7B ) in which edge formations  50  define rows of projecting element-mold cavities  52 . Roller  46  is a pressure roll which coacts with mold roll  44  for formation of continuous strip  10 ′.  
         [0042]     Molten resin is continuously extruded and applied with pressure against mold roll  44  using pressure roll  46 . Molten resin is forced into mold cavities  52  and between rolls  44 ,  46 , to form the projecting elements  14  integral with backing  12 . After cooling while on the roll, the continuous strip  10 ′ is stripped from mold roll  44 , the projecting elements  14  undergoing temporary elastic deformation to achieve release from the mold cavities  52 .  
         [0043]     A trim roller assembly  60  is mounted above mold roll  44  such that continuous strip  10 ′ is removed or stripped from mold roll  44  immediately upstream of trim roller assembly  60 . Trim roller assembly  60  can include two rollers, as shown  FIG. 6A , or one roller, as shown in  FIG. 6B . A tensioning roller assembly  62  creates tension in member  10  for effecting the removal of strip  10 ′ from mold roll  64 . Downstream of tensioning roller assembly  62  is a winder  64  for winding continuous strip  10 ′ on spools  66  for subsequent shipment, storage and use.  
         [0044]     Referring to  FIGS. 7A and 7B , mold roll  44  includes a series of stacked plates  48  having edge formations  50  on either side of each plate. When stacked, plates  48  together define projecting element-forming cavities  52  within which projecting elements  14  are formed. Plates  48  also define water passages  68  for cooling of member  10 ′.  
         [0045]     Referring to  FIG. 7D , which is an enlarged view of section  7 D of  FIG. 7A , plates  48  of mold role  46  can be formed by etching a cone shape  70  for a length of about 0.004″ from roll edge  72 . The remaining tip portion  74  of the cone is formed by laser machining ( FIG. 7E ) in which a laser  80 , under computer position control, is used to remove material from the plate to form the tip portion. Barb impressions  20   a ′ and  20   b ′ can also be formed using laser machining. The laser can also be controlled to form grooves  30  in cone  18 . The mold rolls are preferably formed of beryllium copper, the temperature of which is controlled during molding such that the resin does not cool too fast during application.  
         [0046]      FIG. 8  shows an alternative embodiment of a mold cavity in which a first plate  48  defines an edge formation  50  as described above, and a second plate  48 ′ defines an edge formation  50 ′ having a tip  94  terminating prior to a tip  92  of edge formation  50 . Thus, distal tip  24  of element  12  is defined by tip  92 .  
         [0047]     While skin attachment member  10  has been described as including multiple, parallel rows of projecting elements  14 , the mold rolls can be arranged such that the rows of elements  14  are offset or otherwise distributed on backing  12 . The projecting elements  14  can also be formed such that their longitudinal axes are not perpendicular to backing  12  or are distributed at various angles to backing  12 . While enough of the projecting elements  14  should include barbs  20  to provide the desired degree of securement to the skin, not all of projecting elements  14  need include barbs  20 .  
         [0048]     Other embodiments are within the scope of the following claims.