Abstract:
Fluidic conductors deliver electrical signals to targeted locations within an organ. Both the insulating materials and conductive media components of the fluidic conductors are ultra-flexible. The small size of the fluidic conductors makes the technology particularly applicable to auditory prostheses, for example, cochlear implants, that deliver electrical signals to very discrete locations within the cochlea.

Description:
BACKGROUND 
       [0001]    Implantable medical devices can deliver electrical charges or signals to specific targeted areas, typically neural structures, within a body tissue or organ. Electrical conductors include an outer insulating material that surrounds a conductive material, typically a wire or other solid conductive medium. Differences in thermal expansion characteristics, flexibility, surface roughness, robustness, and other material characteristics can often lead to failure of such conductors due to breakdown of either or both of the insulating material and conductive element. 
       SUMMARY 
       [0002]    Embodiments disclosed herein relate to fluidic conductors for electronics. The technologies disclosed herein have particular application in medical devices implanted within a bodily tissue (human, mammalian, or otherwise). Such devices include stimulating electrode arrays. However, any type of electronics requiring ultra-flexible electrical conductors also can benefit from these technologies. Such electronics can include those subject to excessive vibration or movement (due to, for example, articulation of machine parts or levers). The small size of the fluidic conductors makes the technology applicable to auditory prostheses, for example, cochlear implants, that deliver electrical signals to very discrete locations within the cochlea. 
         [0003]    This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    The same number represents the same element or same type of element in all drawings. 
           [0005]      FIG. 1  is a partial view of a behind-the-ear auditory prosthesis worn on a recipient. 
           [0006]      FIG. 2  is a side view of an embodiment of an implantable portion of an auditory prosthesis. 
           [0007]      FIG. 3  is a side view of another embodiment of an implantable portion of an auditory prosthesis. 
           [0008]      FIG. 4A  is a partial perspective view of an adapter body utilized in an internal component of an auditory prosthesis. 
           [0009]      FIG. 4B  is a partial perspective view of an intracochlear body utilized in an internal component of an auditory prosthesis. 
           [0010]      FIG. 5  is a partial top view of another embodiment of an internal component of an auditory prosthesis. 
           [0011]      FIG. 6A  is a cross-sectional view of the adapter body of  FIG. 5 . 
           [0012]      FIG. 6B  is a cross-sectional view of the intracochlear body of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    The technologies disclosed herein can be used in conjunction with various types of implantable electronics, or other electronics that require small and/or extremely flexible conductive pathways for the transmission of electrical signals. For clarity, however, the technology will be described in the context of an auditory prosthesis such as a cochlear implant that utilizes both an external portion and an implantable portion. Of course, one of skill in the art will appreciate that the flexible conductive pathways can also be utilized with totally implantable cochlear implants as well. 
         [0014]    Referring to  FIG. 1 , cochlear implant system  100  includes an implantable component  144  typically having an internal receiver/transceiver unit  132 , a stimulator unit  120 , and an elongate lead  118 . The internal receiver/transceiver unit  132  permits the cochlear implant system  100  to receive and/or transmit signals to an external device  126  and includes an internal coil  136 , and preferably, a magnet (not shown) fixed relative to the internal coil  136 . These signals generally correspond to external sound  103 . Internal receiver unit  132  and stimulator unit  120  are hermetically sealed within a biocompatible housing, sometimes collectively referred to as a stimulator/receiver unit. The magnets facilitate the operational alignment of the external and internal coils, enabling internal coil  136  to receive power and stimulation data from external coil  130 . Elongate lead  118  has a proximal end connected to stimulator unit  120 , and a distal end implanted in cochlea  140 . Elongate lead  118  extends from stimulator unit  120  to cochlea  140  through mastoid bone  119 . 
         [0015]    In certain examples, external coil  130  transmits electrical signals (e.g., power and stimulation data) to internal coil  136  via a radio frequency (RF) link, as noted above. Internal coil  136  is typically a wire antenna coil comprised of multiple turns of electrically insulated single-strand or multi-strand platinum or gold wire. The electrical insulation of internal coil  136  is provided by a flexible silicone molding. Various types of energy transfer, such as infrared (IR), electromagnetic, capacitive and inductive transfer, can be used to transfer the power and/or data from external device to cochlear implant. In the depicted embodiment, the implantable component  144  also includes an adapter  123  disposed outside of the cochlea  140 . The adapter  123  and flexible conductors extending therefrom (that form a stimulating assembly  146 ) are described in further detail below. 
         [0016]    There are a variety of types of intra-cochlear stimulating assemblies including short, straight and peri-modiolar. Stimulating assembly  146  is configured to adopt a curved configuration during and or after implantation into the recipient&#39;s cochlea  140 . To achieve this, in certain arrangements, stimulating assembly  146  is pre-curved to the same general curvature of a cochlea  140 . Such examples of stimulating assembly  146 , are typically held straight by, for example, a stiffening stylet (not shown) or sheath which is removed during implantation, or alternatively varying material combinations or the use of shape memory materials, so that the stimulating assembly can adopt its curved configuration when in the cochlea  140 . Other methods of implantation, as well as other stimulating assemblies which adopt a curved configuration, can be used. 
         [0017]    Stimulating assembly can be a perimodiolar, a straight, or a mid-scala assembly. Alternatively, the stimulating assembly can be a short electrode implanted into at least in basal region. The stimulating assembly can extend towards apical end of cochlea, referred to as cochlea apex. In certain circumstances, the stimulating assembly can be inserted into cochlea via a cochleostomy. In other circumstances, a cochleostomy can be formed through round window, oval window, the promontory, or through an apical turn of cochlea. 
         [0018]    As apparent from the above description, it is important that the internal components of the cochlear implant display flexibility. This is especially desirable for the components that are subject to bending stress (e.g., the stimulating assembly  146 ) or that must flex due to recipient movement (e.g., the elongate lead  118 ). Often, the flexibility of a particular component can be limited by the materials that are utilized in the manufacture of said component. In known cochlear implants, fiber optics or conductive wires that conduct signals from the stimulator unit  120  are often significantly less flexible than the plastic or silicone bodies or sheathing in which those components are contained. Accordingly, the technologies described further below utilize conductive fluids or other highly deformable conductive media to deliver electrical signals from the stimulator unit  120  to a contact array disposed within the cochlea  140 . 
         [0019]      FIG. 2  is a simplified side view of an internal component  344  having a combined stimulator/receiver unit  302  that receives encoded signals from an external component of the cochlear implant system. Internal component  344  terminates in a stimulating assembly  318  that includes an extracochlear region  310  and an intracochlear region  312 . Intracochlear region  312  is configured to be implanted in the recipient&#39;s cochlea and has disposed thereon a contact array  316 . Each discrete contact in the array  316  is operatively connected to the stimulator/receiver unit  302  as described below. 
         [0020]    Internal component  344  further includes a lead region  308  coupling stimulator/receiver unit  302  to stimulating assembly  318 . Lead region  308  includes a region  304  which is commonly referred to as a helix region, however, the required property is that the lead accommodate movement and is flexible, it does not need to be formed from wire wound helically. Lead region also comprises a transition region  306  which connects helix region  304  to stimulating assembly  318 . Electrical stimulation signals generated by stimulator/receiver unit  302  are delivered to contact array  316  via lead region  308 . Helix region  304  prevents lead region  308  and its connection to stimulator/receiver  302  and stimulating assembly  318  from being damaged due to movement of internal component  344  (or part of  344 ) which can occur, for example, during mastication. 
         [0021]    The extracochlear region  310 , in this embodiment, includes an adapter body  350  that contains a plurality of electrode contacts or other conductive element termination points (described below). The adapter  350  is connected to the stimulator/receiver unit  302  via the lead region  308  and the structures and components included therein. Each electrode contact is connected to a wire or other conductive element so as to be operatively linked to the stimulator/receiver unit  302 . A plurality of microtubes  352  extend from the adapter  350  to the intracochlear region  312 . Individual microtubes  352  can be bound together or discrete from adjacent microtubes  352 . In embodiments where the microtubes are discrete from each other, each microtube may move as required, with minimal, if any, effect on the movement of adjacent microtubes. The ends of the microtubes  352  form a contact array  316  in the intracochlear region  312  that delivers electrical signals to locations within the cochlea. The contact array  316  is disposed in an intracochlear body  370  that is inserted into the cochlea. In an alternative embodiment, the adapter body  350  and intracochlear body  370  can be an integral component (as depicted, for example, in  FIG. 5 ). 
         [0022]      FIG. 3  depicts another embodiment of an internal component  444  for use with a cochlear implant system. Certain of the components utilized in the embodiment of  FIG. 2  are not described again, unless otherwise noted. In this embodiment, an adapter body  450  containing a plurality of electrode contacts or conductive element termination points is fixed to a stimulator/receiver unit  402 . The stimulating assembly  418  includes a plurality of elongate structures  452 , which may be microtubes, extending from the adapter  450 . The lengths of the structures  452  are determined as required or desired for a particular application. The elongate structures  452  can be bound together or discrete from adjacent elongate structures  452 , as described above. The ends of the elongate structures  452  form a contact array  416  in the intracochlear region  412  that delivers electrical signals to discrete locations within the cochlea. The contact array  416  can be disposed within an intracochlear body  470  that is inserted into the cochlea. With these different internal assemblies in mind, the structure of the adapter bodies, elongate structures, and intracochlear bodies depicted in  FIGS. 2 and 3  are described further below. 
         [0023]      FIG. 4A  depicts an embodiment of an adapter body  550  utilized in an internal component of an auditory prosthesis. The adapter  550  includes an outer surface  554  which can be any shape as required or desired for a particular application. Given the implantable nature of the adapter  550 , however, low-profile shapes can be particularly desirable. Additionally, an elongate shape that provides a sufficient volume for the accommodation of a number of electrode contacts can also be desirable. The adapter  550  of  FIG. 4A  is simplified, and shows only a single electrode contact  556  substantially contained therein. A wire or other conductive element (not shown) connects the electrode contact  556  to the associated stimulator/receiver unit. The adapter  550  defines a void  558  that includes, in this embodiment, an electrode chamber  560  and a channel  562 . In the depicted embodiment, the electrode chamber  560  is substantially cylindrical, but other geometries are contemplated. For example, the electrode chamber can be pyramidal, frustoconical, or conical in shape. In such embodiments, the electrode contact  556  is located proximate the wider base of the chamber  560 . The electrode chamber  560  exposes a portion of the electrode contact  556  to the void  558 . The channel  562  is connected to the electrode chamber  560  and terminates at an opening  564  defined by the outer surface  554  of the adapter  550 . The depicted embodiment also includes an elongate structure  552  that extends from the adapter  550 . The elongate structure  552  can have a circular, oval, square, or other cross-sectional shape. The elongate structure  552  is also disposed within the adapter  550  and terminates at the electrode chamber  560 . Thus, an interior lumen of the elongate structure  552  is in fluidic communication with the electrode chamber  560 . Alternatively, the elongate structure  552  can extend completely to the electrode  556 . In other embodiments, the elongate structure  552  can penetrate the body  550  to a depth that enables the elongate structure  552  to be secured to the body  550 . In the depicted embodiment, an end of the elongate structure  552  defines an electrical contact opening  566  when the void  558  and elongate structure  552  are filled with a conductive medium. This contact opening  566  acts as a stimulation site for a neural structure when the end of the elongate structure  552  is inserted directly into the cochlea. In other embodiments (described below), the elongate structure  552  terminates at an intracochlear body, which is inserted into the cochlea. 
         [0024]      FIG. 4B  depicts an embodiment of an intracochlear body  570  utilized in an internal component of an auditory prosthesis. Like the adapter  550  of  FIG. 4A , the intracochlear body  570  is simplified, and shows only a single internal channel  572  formed therein. An outer surface  574  of the intracochlear body  570  defines an electrical contact opening  576  when the internal channel  572  is filled with a conductive medium. This contact opening  576  acts as a stimulation site for a neural structure when the intracochlear body  570  is inserted into the cochlea. In that regard, the intracochlear body  570  is typically elongate in shape. Existing commercially-available cochlear implants can have up to twenty-two electrode contacts to stimulate neural structures located within the cochlea. Accordingly, embodiments of the intracochlear bodies  570  described herein may include an equivalent number of contact openings  576 . Of course, embodiments having any number of contact openings  576  are contemplated. 
         [0025]    One or more elongate structures  552  can extend at least partially into the channels  572  of the intracochlear body  570 . In certain embodiments, the elongate structures  552  terminate at the same or different distances into the intracochlear body  570 . In other embodiments, the elongate structure  552  may extend completely to the contact opening  576 . These elongate structures  552  can extend from the adapter  550  described above in  FIG. 4A . Thus, signals output by stimulator are transmitted, via a conductive medium, to the intracochlear body  570 . The conductive medium transmits the signals through the channel  572  of the intracochlear body  570  to a stimulation site (e.g., the contact opening  576 ). 
         [0026]    In the depicted embodiment, the opening  576  is covered by a cover layer  578 . The cover layer  578  can be used to retain a conductive medium within the channel  572 , thus preventing leakage thereof. This can be useful in embodiments when the conductive medium is saline or other medical-grade fluid that is disposed within the adapter  550  and/or intracochlear body  570  prior to implantation. It should be noted that the adapter body  550  depicted in  FIG. 4A  can also utilize a cover layer at the contact opening  566  located at the end of the elongate structure  552 . In order to ensure electrical signals sent from the electrode contact  556  ( FIG. 4A ) to the contact opening  576  are delivered to the targeted neural structure, in embodiments, it is desirable for the cover layer  578  to be made of a charge transfer material, such as TYVEK or TEFLON. Other suitable materials include polymeric materials, ionically conductive elastomers, or hydrogels such as polyacrylic acids, poly(meth)acrylic acids, polyalkylene oxides, polyvinyl alcohols, poly(N-vinyl lactams), polyacrylamides, poly(meth) acrylamides, or pressure sensitive adhesives such as a N-vinyl-pyrrolidone/acrylic acid copolymer. Additionally, the cover layer  578  need not be entirely solid, but can be of a mesh construction. Surface tension of the conductive medium contained within the channel  572  can be sufficient to prevent the conductive medium from leaking from the channel  572 . In addition to preventing leakage of the conductive medium from the channel  572 , utilization of a cover layer  578  can also prevent tissue ingrowth into the channel. 
         [0027]    A cover layer is not required, however, to prevent certain embodiments of the adapter body  550  or intracochlear body  570  from retaining the conductive medium within the channel or elongate structure. In embodiments where the channel is of microtube or nanotube dimensions, surface tension of the conductive medium can prevent any fluid from leaking from the opening. For embodiments utilized in the above-described cochlear implants, channels and openings having cross-sectional areas of about 0.001 mm 2  to about 0.1 mm 2  are contemplated, as are cross-sectional areas of about 0.01 mm 2  to about 0.075 mm 2 . In other embodiments, the cross-sectional area can be about 0.05 mm 2 . 
         [0028]    Additionally, there can be circumstances where it is desirable to encourage tissue growth into the contact opening, so as to ensure contact with the targeted neural structure. In such a case, the adapter body, the intracochlear body, and/or the elongate structure can include a cell growth factor or cytokine located proximate to the contact opening. Additionally, drugs such as dexamethasone or other classes of steroid drugs that have anti-inflammatory and/or immunosuppressant properties can be delivered via the devices described herein. In such an embodiment, an electrical charge can render a target cell wall porous, thus allowing the drug to enter. Gene therapies can be similarly delivered. Further, the bodies or elongate structures can be manufactured from materials that enable their use as reservoirs for active molecules such as medicaments, growth factors, or DNA. Additionally, the cover layer can serve to host and release, when appropriate, beneficial chemical and/or bioactive agents at the site of implantation of the flexible conductor. For example, anti-inflammatory, anti-bacterial, and/or anti-viral agents could be released from the cover layer. In another embodiment, cellular growth factors could be released from the cover layer. 
         [0029]    Materials utilized in the flexible conductors described herein can be those that are biocompatible, flexible, robust, and that can be sterilized during or after manufacture. Flexible conductors include any of the adapters, elongate structures, microtubes, and intracochlear bodies that include a hollow structure adapted to receive a conductive medium. In embodiments, materials that stretch without deformation can be used. Examples of materials that can be utilized for the adapter body include silicone elastomeric material such as Silastic material, polyamide, PVC, polyurethane blends, or other types of polymers or elastomers that are typically used for implantable insulators. The elongate structure and intracochlear body can be manufactured from similar materials. Additionally, electrically conductive materials such as polymeric materials, ionically conductive elastomers, or hydrogels such as polyacrylic acids, poly(meth)acrylic acids, polyalkylene oxides, polyvinyl alcohols, poly(N-vinyl lactams), polyacrylamides, poly(meth) acrylamides, or pressure sensitive adhesives such as a N-vinyl-pyrrolidone/acrylic acid copolymer can also be utilized. Suitable materials for electrode contacts include platinum, stable platinum iridium, or other highly conductive metals or conductive plastics. Of course, flexible conductors that are not utilized within a human or mammalian body can utilize different types of materials. 
         [0030]    Existing implantable conductors incorporate a metallic structure such as a wire to act as an electrical conductor and metallic surfaces to deliver charge to a neuron. Typically, these metallic elements are embedded in the softer flexible elastomer. Thus, the finished component may not be as flexible as desired. To address these and other issues, the flexible conductors described herein utilize highly deformable conductive media to transfer electrical signals from the electrode contact to a target neuron in a cochlea. In certain embodiments, the conductive media is characterized by a viscosity. Examples of such media include liquids, fluids, colloids, suspensions, or solutions. Mobile fluids and viscous fluids can be utilized. The conductive media can include discrete metallic structures, such as carbon nanotubes, to increase electrical conductivity. The conductive media can also be metallic or ionic. In certain embodiments, saline is used. Additionally, the flexible conductors described herein can be further configured such that body fluids located in the area in which the flexible conductor is implanted can be drawn into the void and/or the channel to serve as the conductive medium. For example, the void can contain, or have disposed thereon, a hydrophilic material that facilitates the drawing of the desired fluid into the body. In embodiments where the interior void is defined by a channel and an electrode chamber, the hydrophilic material can be disposed in one or both of those structures. Certain embodiments include hydrophilic material within the entire void and/or channel, so as to facilitate the drawing of the desired fluid into contact with an electrode. In certain embodiments, the elongate structure itself can be formed of a hydrophilic material so as absorb the desired fluid. In addition to holding the fluid in a hydrophilic material of the elongate structure, the elongate structure can be constructed of material that otherwise promotes transfer of electrical charge along the walls thereof. Bodily fluids that display sufficient conductivity for particular applications include cerebral spinal fluid, perilymph, blood, and others. 
         [0031]      FIG. 5  depicts a partial top view of another embodiment of an internal component  644  of an auditory prosthesis. Additionally,  FIGS. 6A and 6B  depict cross-sectional views of an adapter body  650  and an intracochlear body  670 , respectively. Accordingly,  FIGS. 5-6B  are described simultaneously. Here, multiple electrode contacts  656  are embedded within the adapter  650 . Each electrode contact  656  is exposed to a void  658 . In the depicted embodiment, the portion of the void  658  proximate the electrode contact  656  is an electrode chamber  660  sized to expose nearly the entire surface area of the electrode contact  656 , though exposure of smaller areas of the electrode contact  656  is also contemplated. The electrode chamber  660  is in fluidic communication with a channel  662  defined by the body  650 . In this embodiment, an elongate structure  652  is disposed within the channel  662  and terminates, at one end, at the electrode chamber  660 . The elongate structure  652  extends through the channel  662  and out of an opening  664  defined by an outer surface  654  of the adapter  650 . Each elongate structure  652  connects to the intracochlear body  670 . In the depicted embodiment, the elongate structures  652  are bundled into a shape and size consistent with that of the intracochlear body  670 . 
         [0032]    The intracochlear body  670  also includes a plurality of internal channels  672  formed therein. The elongate structures  652  can extend through the channels  672  and terminate at an outer surface  674  of the intracochlear body  670 . Each channel  672  in the intracochlear body  670  terminates at the outer surface  674  thereof, at a contact opening  676 . Each contact opening  676  acts as a stimulation site that is used to stimulate a neural structure within the cochlea, once the intracochlear body  670  is implanted therein. Signals output by the electrode  656  propogate through the conductive medium as described above with regard to  FIGS. 4A and 4B . Although the depicted embodiment depicts an elongate structure  652  extending through both the channel  662  and the channel  672 , other embodiments need not utilize such elongate structures. 
         [0033]      FIGS. 5-6B  depict the elongate structures  652  and channels  662 ,  672  generally disposed along a single linear axis Al. This depiction is for clarity only. Orientation and spacing of the elongate structures  652  and the channels  662 ,  672  can be as desired along either of the x-axis or y-axis so as to conserve space within the adapter or intracochlear body  670 . Additionally, the electrode contacts  656  need not be disposed along an axis A 2 , as depicted in  FIG. 6A . Instead, the electrode contacts  656  can be disposed and oriented within the adapter  650  based on space considerations, contact area optimization, or other factors. Similarly, contact openings  676  can be arranged in any orientation to form a contact array. In certain embodiments, a single channel  662 ,  672  can be in fluidic communication with a plurality of electrodes, and thus be able to transmit electrical signals from more than a single electrode contact. 
         [0034]    This disclosure described some embodiments of the present technology with reference to the accompanying drawings, in which only some of the possible embodiments were shown. Other aspects can, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments were provided so that this disclosure was thorough and complete and fully conveyed the scope of the possible embodiments to those skilled in the art. 
         [0035]    Although specific embodiments were described herein, the scope of the technology is not limited to those specific embodiments. One skilled in the art will recognize other embodiments or improvements that are within the scope of the present technology. Therefore, the specific structure, acts, or media are disclosed only as illustrative embodiments. The scope of the technology is defined by the following claims and any equivalents therein.