Abstract:
A pass-through assembly including a first wall having oppositely-directed inner and outer sides, the first wall defining a first opening extending from the inner side to the outer side; an elongated structure extending into the opening from the outer side of the first wall; a first material contacting the first wall and the elongated structure so as to at least partially seal the opening, and a second material different from the first material, the second material overlying the first material on the outer side of the wall, the second material adhering to the elongated structure and the first wall, the second material having at least one physical property different than a corresponding physical property of the first material.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of the filing date of U.S. Provisional Patent Application No. 61/871,046 filed Aug. 28, 2013, the disclosure of which is hereby incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    With the advancement of surgical techniques and electronic components, there is a greater desire to implant such electronic components within the body of a human or other animal. However, when electronic components are to be implanted, it is important to ensure secure and safe connections among such components. For example, an implantable electronic component may be mounted within a housing and connected to a remote component by an elongated structure such as wire or cable extending through a wall of the housing. The arrangement of an elongated structure extending through the wall is commonly referred to as a “pass-through.” The pass-through is intended to provide a fluid-tight seal around the elongated structure and, in some cases, should also hold the fluid-tight structure in place relative to the wall of the housing. Moreover, a pass-through used in an implantable housing ordinarily should be biocompatible. 
       BRIEF SUMMARY OF THE INVENTION 
       [0003]    One aspect of the invention provides pass-through assembly. An assembly according to this aspect of the invention desirably includes a first wall having oppositely-directed inner and outer sides. The first wall may define a first opening extending from the inner side to the outer side. The assembly desirably also includes an elongated structure extending into the opening from the outer side of the first wall, and a first material contacting the first wall and the elongated structure so as to at least partially seal the opening. The assembly also may include a second material different from the first material, the second material overlying the first material on the outer side of the wall, the second material adhering to the elongated structure and the first wall. 
         [0004]    The second material may one or more have physical properties different from those of the first material. For example, the second material may have an elastic modulus, tensile strength, toughness or adhesion greater than the corresponding property of the first material. Merely by way of example, the first material may be a relatively soft sealant such as a silicon, for example, a biocompatible silicon or a room temperature vulcanizing (“RTV”) silicone, whereas the second material may be a material such as an epoxy which forms a secure attachment between the elongated structure and the wall. Moreover, the second material may have greater biocompatibility than the first material. 
         [0005]    A further aspect of the invention provides methods of sealing an opening defined in a first wall of a housing. A method according to this aspect of the invention desirably includes; advancing an elongated structure through the opening; applying a first material to the first wall, the first material surrounding the elongated structure; and applying a second material atop the first material, the second material surrounding the elongated structure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a perspective view of a housing assembly according to one embodiment of the invention with certain elements omitted for clarity of illustration; 
           [0007]      FIGS. 2A-2C  are plan views of the housing assembly of  FIG. 1 ; 
           [0008]      FIG. 3A  is a fragmentary cross-sectional view of the housing of  FIGS. 1-2C  at a stage of a manufacturing process; and 
           [0009]      FIG. 3B  is a view similar to  FIG. 3A  depicting the housing assembly of  FIGS. 1-3A  in a completed state. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]      FIG. 1  is a perspective view of an implantable housing assembly  100  according to one aspect of the disclosure. The housing assembly  100  may be any shape, and in one example may have a generally rectangular shape from a plan view, with or without rounded edges, as shown in the plan view of  FIGS. 2A-C . The housing assembly  100  may have a plurality of walls  110   a - d  that may define a partially or completely enclosed area therebetween. Stated another way, a first wall  110   d,  together with additional walls  110   a - 110   c  cooperatively define a partially or completely enclosed interior space. Any of the walls  110   a - d  may be integrally formed with one another, or may be detachably secured to one or more of the other walls  110   a - d.    
         [0011]    As shown in  FIGS. 2C and 3A , a wall  110   d  of the housing assembly  100  may have an inner side  112  and an outer side  114 . Portions of the inner side  112  may be substantially flat. Wall  110   d  may define at least one opening  116  extending entirely through the wall from the inner side  112  to the outer side  114 . The opening  116  may be generally cylindrical, or may be any other shape to accommodate an elongate structure  118  discussed further below. 
         [0012]    The outer side  114  may define a recess  128  between ridges  129  of the housing assembly. Ridges  129  may be integral with wall  110   d  or may be defined by other walls of the housing. A base portion  120  forms a floor of the recess facing outwardly. The outer side may have at least one inner ring  122  around the opening  116 , and at least one outer ring  124  around the inner ring  122 . These rings project in outwardly from the base (toward the top of the drawings in  FIG. 3A ), such that an annular space  126  is formed between the inner ring and the outer ring. In the particular embodiment depicted, rings  124  and  122  are tapered in the outward direction, away from base  120 . Thus, the inner ring  122  defines a conical lead entrance to the opening  116 . The base portion  120 , rings  122 ,  124 , and annular space  126  may be disposed within the recess  128  between the ridges  129 , such that the rings  122  and  124  extend outwardly from the base portion  120  but do not extend outside the recess  128  or past the ridges  129 . 
         [0013]    The wall  110   d  may be assembled to the other of the walls  110  to define a partially or completely enclosed area. In one example, electronic components, schematically depicted at  111 , may be stored therein. Such electronic components may be, for example, components for the operation of an implantable medical device, such as an implantable ventricular assist device, an implantable battery, or an implantable transcutaneous energy transfer system. 
         [0014]    The elongated structure  118  extending though hole  116  may be a flexible wire or electrical cable that may be connected to electronic components  111  within the housing assembly  100 . Typically, the opposite end of elongated structure (not shown) is connected to other electronic components (not shown) either implanted within the body or positioned outside the body. 
         [0015]    In an assembly process according to one aspect of the invention, one or more elongate structures  118  are inserted through the openings  116 . A first material  130  may be applied to outer side  114 . For example, as shown in  FIG. 3C , the first material  130  may be applied to an exterior portion of the elongate structure  118 , atop the inner ring  122 , and at least partially within the annular space  126 . The first material  130  may also be applied at least partially within the opening  116  itself. In the embodiment shown in  FIGS. 3A and 3B , the first material does not extend beyond the outer ring  124 . 
         [0016]    The first material  130  may at least partially seal the opening  116  when the elongate structure  118  is disposed therein. The first material optionally may form a physical bond with the wall of the elongated structure  118 , with the portions of wall  110   d  defining opening  116 , or both. The first material may be an RTV silicone and has a first elastic modulus. 
         [0017]    Although only one hole is depicted in  FIGS. 3A and 3B , elongated structures and first material desirably are provided for the other holes in the same manner. 
         [0018]    A second material  140  may be applied atop the first material. The second material  140  may partially or completely cover the first material  130  within the recess  128 . In one example, the second material  140  may at least partially, but not completely, fill the recess  128  as depicted in  FIG. 3B . For example, a single continuous mass or layer of second material may cover the first material at all of the openings  116 . In other examples, discrete portions of the second material are proved at each opening  116 . The second material  140  may contact each of the elongated structures and also may contact the wall  110   d  as, for example, at the base portion  120 . The second material also may contact other walls of the housing. The second material  140  may form a bond with the outer surfaces of the elongated elements and with at least one wall of the housing. 
         [0019]    Typically, both the first material and the second material are applied in a flowable condition, such as in a liquid, gel or paste-like state. One or both of the materials may be cured to a solid state after application. The curing process may involve a chemical reaction. The conditions required for curing will depend on the compositions of the materials. The curing processes may be performed sequentially, so that the first material is cured before the second material is applied, or simultaneously. Application of the first and second materials desirably takes place after insertion of elongated elements  118  through the openings  116 , and may occur before or after the elongated elements are connected to the electronic components  111 . 
         [0020]    The second material may be different from the first material. For example, the second material may be an epoxy. The second material may have a second elastic modulus. In one example, the second elastic modulus may be different from the first elastic modulus. For example, the second elastic modulus may be greater than the first elastic modulus such that the second material is stiffer than the first material. Alternatively or additionally, the second material may have greater adhesion than the first material to the walls of the housing, to the elongated structures, or both. Also, the second material may have greater biocompatibility than the first material. 
         [0021]    This configuration provides a secure interface at the opening  116 . In particular, the first material may be selected to provide an effective seal around the elongated components, whereas the second material may be selected to provide a secure physical attachment between the elongated elements and the wall. Moreover, the second material may have a greater degree of biocompatibility than the first material. This allows the use of a first material which provides an effective seal but may not have the desired degree of biocompatibility. The bass-through assembly limits the localized, concentrated stress and/or strain that may be placed on the elongate structure  118  while it is disposed within the opening  116 . Limiting of the stress and/or strain may prevent damage to the elongate structure  118  while it is implanted within the body of a mammal and may also prevent the elongate structure  118  from becoming disengaged with the opening  116  of the wall  110   d.    
         [0022]    In a further variant, a third material may be applied wall  110   d,  and desirably to the entire housing assembly  110 , after application of the second material. In one example, the third material is a biocompatible material in the form of a coating as schematically depicted at  137 . In this example, the third material covers the second material. The third material may be selected primarily for its biocompatibility, rather than for physical properties. 
         [0023]    In the embodiments discussed above, the elongated structures  118  are wires or cables. However, other elongated structures such as tubes, rods or the like may be used. The pass-through assemblies can form secure attachments and seals even with flexible elongated elements which may pose difficulties with ordinary sealing and attachment techniques. 
         [0024]    Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.