Patent Description:
Implantable electronics must be protected from their liquid surrounding (body fluids) by a true hermetic barrier. True hermetic implies that the barrier material is impermeable to water and water vapor as well. This requirement is fulfilled by metals (such as titanium), glass or ceramic (e.g. alumina or zirconia). Along with the hermetic sealing requirement, electrical signals must be routed in and outside the hermetic package in order to satisfy the assembly's purpose. This is realized by electrical feedthroughs. Electrodes which serve as interface to the tissue are connected to these feedthroughs. The entire implant assembly of hermetic package, feedthrough and associated interconnected parts must be robust enough to withstand foreseeable mechanical impact loads when implanted in its intended location. Implant assemblies which are implanted in the skull are especially exposed to higher impact loads due to falls, external impacts or other. For this reason, such implants must fulfil normative requirements which are considerably higher when it comes to impact robustness, compared to other implants located in areas of the body less prone to impact exposure (e.g. pacemakers implanted in the patient's chest). State of the art standards for Cochlear implants (e.g. ISO <NUM>-<NUM> or EN <NUM>-<NUM>-<NUM>) demand impact robustness of <NUM> Joules for a striking element directly hitting the implants most sensitive part. Here, impact robustness also includes full device functionality after impact.

While metals offer sufficient impact strength to build mechanically robust implantable packages, they lack the possibility to allow radio-frequency (RF) signals, alternating magnetic fields (inductive power supply) and (infrared) light to pass through the package wall. Additionally, due to a metal's conductive nature, the embodiment of a high number of electrical feedthroughs including individual feedthrough insulation, results in larger overall package volumes. Ceramic and glass packages in turn are inherently more brittle than metal and hence less robust when exposed to impact loads. However, they are sufficiently transparent to signals described above and can be used for high-channel hermetic packages. Packages require to be overmolded with a polymer such as polydimethylsiloxane (e.g. PDMS, epoxy or polyurethane) in order to ensure electrical insulation of the feedthroughs outside the package after lead or connector assembly. However, depending on the nature of the overmold (especially when elastomeric materials are used) the overmold is not suitable to sufficiently buffer impacts as considered to happen in typical applications. To utilize the advantages of non-metal packages, the following invention offers possibilities to increase their impact strength.

<CIT> relates to an implantable medical device with the features of the preamble of claim <NUM>.

It is an objective to provide a hermetic sealed assembly which provides the effect of further improved impact absorption.

This object is achieved by the implantable assembly with the features of claim <NUM>.

Accordingly provided is an implantable assembly, comprising:.

Advantageously, the protective structure may further enclose the base portion.

Yet further, the protective structure may comprise a material which is at least one of polymer, metal, carbon, ceramic, and composite material.

Further, at least one section of the protective structure may be adapted to serve as electrically active contact area.

The interior hermetically sealed volume may enclose electronics.

The protective structure may further enclose electric components in particular at least one of feedthroughs, pins, headers, wires, coils, antennas, electrical components, cables, electrodes.

The polymer layer may be made from at least one of PDMS, epoxy, and polyurethane.

The protective structure comprises a number of openings, in particular holes, slits, for fixation by the polymer layer.

The assembly may further comprise a number of metal contacts embedded in the protective structure.

The metal contacts may comprise metal platelets, in particular at least one of platinum, platinum-iridium, titanium, MP35N, stainless steel, or Nitinol, inserted in the protective structure.

Further, the metal contacts may be embedded with one of PDMS epoxy, and polyurethane.

The assembly may further comprise an element adapted as a strain relieve for cables and/or connectors joined to the feedthroughs the element being integrally formed with the protective structure.

The contacts can be electrically connected to the feedthroughs beneath the protective structure.

The base portion and / or the lid portion may comprise at least one reinforced section serving as absorption or as contact points for the protective structure in particular chamfered edges, rounded edges, thicker walls.

Further provided may be attachment means for the protective structure, in particular at least one of notches, anchors, and snap fits.

Further, the protective structure may define at least one void-free space with the lid portion and/or with the base portion the at least one void-free space comprising at least one polymer.

The protective structure may further comprise a number of different polymer layers with respective Young's modulus different from each other.

The protective structure may cover additionally to the lid portion and the base portion but also a coil and parts of a cable, which are located outside the internal volume, and may additionally form a guiding structure for the cable to the outside to form a strain relief for the cable.

The protective structure may sit on side walls of the lid portion.

The protective structure may be completely encapsulated by a polymer layer.

The polymer layer may also encapsulate the lid portion, the base portion, the feedthrough, and the coil, thus providing for biocompatibility of the assembly.

Thus, an assembly is provided made of ceramic (or sapphire, glass-ceramic or glass or another non-metallic material) which is reinforced by an additional surrounding structure to significantly improve its impact strength. This additional structure can be a mechanical frame or scaffold of different designs which allows to absorb mechanical impact and distribute the loads from impact sensitive parts, such as the package's center in whole or part to less sensitive areas such as the sides. Another realization of impact improvement is provided by encapsulation of the package with different material layers with varying Young's moduli. Such layers could be polymers such as elastomers or thermoplastic materials.

The impact protection not only shields sensitive parts of the hermetic package, but also components such as feedthroughs, wires, pins, coils and cables or at least transitions to the same.

Thus, the invention provides an implantable assembly with a protective structure which surrounds the lid portion and the base portion (the hermetic package) and other impact sensitive parts of the active implantable assembly in part or in total.

The protective structure is designed and shaped to direct it from mechanically sensitive parts to more robust parts (e.g. from the center to the side walls), or to absorb kinetic energy leading to permanent or temporary deformation or to avoid demolition of the hermetic package and other parts (e.g. coils, antennas).

Since the hermetically sealed volume is in the core of the assembly it is best protected against deformation and thus against leakage. The parts which seal the interior volume are not for protecting against mechanical impact. That is, they will not deform and thus their hermetic sealing capability will not be reduced or destroyed. Only the protective structure is exposed to mechanical impacts but impacts and even a deformation thereof will not affect the sealing of the volume defined by the hermetic package.

The invention and embodiments thereof will be described in more detail with reference to the drawings, wherein.

Referring to <FIG>, an active implantable medical assembly is illustrated, comprising a hermetic package with a lid portion <NUM> and base portion <NUM>, feedthroughs <NUM>, interconnected components, e.g. a coil <NUM>, and a polymer encapsulation, e.g. made of PDMS <NUM>. The hermetic package <NUM>, <NUM> is covered by a protective structure <NUM>, on top of the lid portion <NUM> and parts of the base portion <NUM>.

The lid portion <NUM> and base portion <NUM> define a hermetically sealed internal volume <NUM> in which electronics <NUM> is housed. Lid portion <NUM> and base portion <NUM> together are also denoted here as the hermetic package.

The protective structure <NUM> encloses the lid portion <NUM> and is adapted for protecting the interior volume <NUM> against mechanical impacts. Since the protective structure <NUM> is in contact only with the vertical edge of the lid portion <NUM> and with the base portion <NUM> it can deflect impacts on its top side onto the side walls of the lid portion, thus protecting the horizontal top area of lid portion <NUM> from the impacts.

Not illustrated in <FIG> but also part of the invention is a protective structure <NUM> which also covers the backside of the implant building a share, oval or other enclosing shape.

<FIG> show different views of the assembly. Exploded and sectional views enable visibility in the enclosed electronics <NUM> inside the hermetic package10, <NUM>. Inside the hermetic package <NUM>, <NUM> the lid portion's <NUM> side walls are directly opposing the protective structure and in case of impact, the energy shall be distributed to the same. To additionally reinforce the walls, internal structures <NUM>, such as radii, chamfers, or similar can be added to the lid's inside as depicted in <FIG>.

<FIG> shows the additional embedding of a metal contact <NUM> in the protective structure <NUM>. The contact can be electrically connected to a feedthrough <NUM> beneath the protective structure <NUM>. Spacings within the protective structure <NUM> might be added as needed. Another option to embed a metallic contact is the realization of the protective structure <NUM> out of a conductive material, such as metal and leave parts of the structure exposed to the tissue when embedded in polymer.

The metal contact <NUM> can be for electrical stimulation, sensing neural signals or for other purposes.

In <FIG>, the protective structure <NUM> is shaped according to different designs, such as rings, spirals, honeycombs or openings of various shapes, crosshatches, parallel lines, meshes, random lines, solid planes with or without holes, poles, stacked layers. Theses designs can be adapted to the needs of application, shape of the assembly or to allow better mechanical anchoring within the surrounding polymer encapsulation <NUM>, <NUM> described below. The depicted designs are only examples and de8pending on the individual implant design, partial covering of the protective structure <NUM> might be desired.

To firmly secure the protective structure <NUM> and to ensure the implant assembly's biocompatibility for all materials in direct contact to the tissue, the protective structure is encapsulated in polymer <NUM>, such as PDMS. <FIG> illustrate the presence of the polymer encapsulation <NUM>. The protective structure <NUM> can be designed with particular gaps to facilitate void-free filling of spaces <NUM> beneath the protective structure <NUM> with polymer. If a metal contact <NUM> is embedded in the protective structure <NUM>, the polymer encapsulation <NUM> shall not cover the metal contact <NUM> to expose it to the tissue.

Electrical connections can be realized by attaching a wire to the metal contact <NUM> (e.g. backside) and routing it beneath the protective structure <NUM>.

In <FIG>, the protective structure <NUM> forms a space <NUM> on top of the lid portion <NUM>, which is completely filled up with layers <NUM>, <NUM> of different polymers. In <FIG> two polymers layers <NUM>, <NUM>, one layer <NUM> with Young's Modulus A and a second layer <NUM> with Young's Modulus B are illustrated. However, the layer stack is not limited to two layers <NUM>, <NUM> but whatever is suitable for application and design of the hermetic assembly and protective structure <NUM> which forms the side walls. The polymer layers <NUM>, <NUM> act as impact protection by absorbing the impact rather than deflecting it.

The polymer layers with respective different Young's modulus are to achieve a gradient soft-to-hard or vice versa across the layers. Preferably more than two such layers are provided. Typical polymer materials for these layers are PDMS, epoxies, polyurethanes. The polymers might be applied in liquid state or applied as foam or be mixed with fillers or particles to modify their Young's modulus. To achieve lateral gradients, different materials or amounts of fillers can be utilized in segments of one layer which are next to each other.

The assembly may further comprise additional layers of polymer mesh, sheets or foil. Polymer meshes, sheets and foils can be made of polyester (PE), polyether-etherketone (PEEK), polypropylene (PP), parylene or any other suitable polymer.

Yet further, the assembly may comprise marker elements for identification of the assembly, and/or of the protective structure <NUM>. The protective structure <NUM>; <NUM>, <NUM> may further comprise a transparent polymer which allows optically reading the marker elements.

Another possibility for device identification is the placement of an identification tag between protective structure and surrounding PDMS encapsulation or between layers of different polymers.

<FIG> shows a hermetic package <NUM>, <NUM> which is surrounded by a protective structure <NUM>, <NUM> entirely made from different layers of polymers. Again, in this example two layers of varying Young's Modulus <NUM>, <NUM> and a surrounding encapsulation of Young's Modulus C <NUM> are depicted. More layers are also conceivable. Again, the polymer layers <NUM>, <NUM> act as impact protection by absorbing the impact rather than deflecting it.

Depending on the configuration and implant design, the protective structure <NUM> might extend to the base portion <NUM> or only cover the lid portion <NUM> and some adjacent structures such as cables, wires, coil <NUM>, feedthroughs <NUM> etc..

<FIG> shows an assembly with a protective structure <NUM> covering not only the lid portion <NUM> and the base portion <NUM> but also the coil <NUM> and parts of the cable <NUM>, which are outside the internal volume <NUM> and additionally introduces a guiding structure for the cable or wire to the outside to form a strain relief <NUM>. The protective structure <NUM> sits on the side walls of the lid portion <NUM>. It is completely encapsulated by a polymer layer <NUM>. The polymer layer <NUM> also encapsulates the lid portion <NUM>, the base portion <NUM>, the feedthrough <NUM>, and the coil <NUM>, thus providing for biocompatibility of the assembly.

The protective structure <NUM> can be manufactured by means of additive or subtractive fabrication.

Claim 1:
Implantable assembly, comprising:
a base portion (<NUM>), and a lid portion (<NUM>) covering the base portion (<NUM>), the lid portion (<NUM>) and the base portion (<NUM>) defining an interior hermetically sealed volume (<NUM>),
a protective structure (<NUM>; <NUM>, <NUM>) which encloses the lid portion (<NUM>),
the protective structure (<NUM>; <NUM>, <NUM>) being adapted for protecting the interior volume (<NUM>) against mechanical impacts,
further comprising a polymer layer (<NUM>; <NUM>) which encapsulates the base portion (<NUM>), the lid portion (<NUM>), and the protective structure (<NUM>; <NUM>, <NUM>),
characterized in that
a space (<NUM>) is formed in the protective structure (<NUM>) on top of the lid portion (<NUM>) and a number of polymer layers (<NUM>, <NUM>) are arranged therein, each of the layers (<NUM>, <NUM>) having a respective Young's Modulus different from each other.