fig1 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 fig2 a - 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 . as shown in fig2 c 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 . 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 fig3 a ), 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 . 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 . 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 . 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 fig3 c , 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 fig3 a and 3b , the first material does not extend beyond the outer ring 124 . 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 a silicone and has a first elastic modulus . although only one hole is depicted in fig3 a and 3b , elongated structures and first material desirably are provided for the other holes in the same manner . 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 fig3 b . 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 . 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 . 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 . 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 pass - 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 . in some embodiments , these force limiting effects of the present invention may be further supported by attachment of an at least one ring element 131 to the exterior surface of elongated structure 118 , as shown in fig3 a - b . at least one ring element 131 may be a rigid element with an outer diameter greater than the outer diameter of opening 114 so as to require one - way insertion of the flexible structure therein . alternatively , the at least one ring element 131 may be deformable to permit insertion through opening 114 in an insertion direction , yet non - deformable , or at least rigid enough , to provide a redundant means of resisting the stress and / or strains when elongated structure 118 is advanced in a removal direction . although depicted in fig3 a - b as flat , ring element 131 may assume alternate shapes , for example , ring element 131 may have a curvilinear surface area with a triangular profile oriented for insertion into opening 116 . in a further variant , a third material may be applied to 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 . 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 . 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 .
a pass - through assembly including a first wall 110 d having oppositely - directed inner and outer sides , 112 , 114 , the first wall 110 d defining a first opening 116 extending from the inner side 112 to the outer side 114 ; an elongated structure 118 extending into the opening 116 from the outer side 114 of the first wall 110 d ; a first material 130 contacting the first wall 110 d and the elongated structure 118 so as to at least partially seal the opening 116 , and a second material 140 different from the first material 130 , the second material 140 overlying the first material 130 on the outer side 114 of the wall 110 d , the second material 140 adhering to the elongated structure 118 and the first wall 110 d , the second material 140 having at least one physical property different than a corresponding physical property of the first material 130 .