The present invention relates to the field of implantable hearing instruments, and in particular, to implantable electret microphones employable in fully- and semi-implantable hearing instrument systems.
Traditional hearing aids are placed in a user's ear canal. The devices function to receive and amplify acoustic signals within the ear canal to yield enhanced hearing. In some devices, “behind-the-ear” units have been utilized which comprise a microphone to transduce the acoustic input into an electrical signal, some type of signal processing circuitry to modify the signal appropriate to the individual hearing loss, an output transducer (commonly referred to in the field as a “receiver”) to transduce the processed electrical signal back into acoustic energy, and a battery to supply power to the electrical components.
Increasingly, a number of different types of fully- or semi-implantable hearing instruments have been developed. By way of example, implantable devices include instruments which employ implanted electromechanical transducers for stimulation of the ossicular chain and/or oval window, instruments which utilize implanted exciter coils to electromagnetically stimulate magnets fixed within the middle ear, and instruments which utilize an electrode array inserted into the cochlea to transmit electrical signals for sensing by the auditory nerve.
In these, as well as other implanted devices, acoustic signals are received by an implantable microphone, wherein the acoustic signal is converted to an electrical signal that is employed to generate a signal to drive an actuator that stimulates the ossicular chain and/or oval window or that is applied to selected electrodes of a cochlear electrode array. As may be appreciated, such implantable hearing instrument microphones must necessarily be positioned at a location that facilitates the receipt of acoustic signals and effective signal conversion/transmission. For such purposes, implantable microphones are most typically positioned in a surgical procedure between a patient's skull and skin, at a location rearward and upward of a patient's ear (e.g., in the mastoid region).
Given such positioning, the size and ease of installation of implantable hearing instrument microphones are primary considerations in the further development and acceptance of implantable hearing instrument systems. Further, it is important that a relatively high sensitivity and flat frequency response be provided to yield a high fidelity signal. Relatedly, the componentry cost of providing such a signal is of importance to achieving widespread use of implantable systems.
In view of the foregoing, a primary objective of the present invention is to provide an implantable microphone having a relatively small profile.
An additional objective of the present invention is to provide an implantable microphone that is reliable and cost effective.
Yet further objectives of the present invention are to provide an implantable microphone that provides high-sensitivity and relatively flat frequency response in acoustic signal conversion.
One or more of the above-noted objectives and additional advantages are realized by an implantable microphone of the present invention. The implantable microphone includes a hermetically-sealed, enclosed volume, and an electret member and back plate disposed with a space therebetween within the enclosed volume. The electret member and back pate are capacitively coupleable to provide an output signal indicative of acoustic signals incident upon at least one of the electret member and back plate. The electret arrangement yields a compact, and relatively low cost arrangement, while also providing a high quality output signal for use by an implantable hearing instrument.
As employed herein, an “electret member” is meant to refer to a microphone component having a dielectric material portion with a permanently-embedded static electric charge and an electrically-conductive material portion, or electrode. Further, a “back plate” is meant to refer to a microphone component having an electrically-conductive material portion, or electrode. When employed together in a microphone, the electret member and back plate may be disposed with the dielectric material portion of the electret member and the electrically-conductive material portion of the back plate located in opposing spaced relation and capacitively coupled, and with at least one of the electret member and back plate being moveable in response to acoustic signals incident thereupon, wherein electrical outputs from the electret member and back plate (e.g. from each of the electrodes) may be utilized to provide an electret output signal.
By way of example only, in a common source configuration, the electret member and back plate may be interconnected to a preamplifer (e.g., a FET) that is powered by a separate power source (e.g., an implantable, rechargeable battery). In turn, the preamplifier output may provide the electret output signal. The electret output signal may be processed and/or otherwise utilized to generate a drive signal applied to a transducer to stimulate a middle ear and/or inner ear component of a patient.
In one aspect, the back plate of the implantable microphone may be disposed so as to define at least a peripheral portion of the enclosed volume. For example, the back plate may be defined as a part of a flexible diaphragm that extends across a housing aperture for receiving external acoustic signals (e.g., transcutaneous signals emanating from outside the body and generating acoustic signals within the enclosed volume in response thereto).
In another aspect, a first portion of the enclosed volume of the implantable microphone may be located on a first side of the electret member and a second portion thereof may be located on a second side of the electret member. In turn, at least one vent may fluidly interconnect the first and second portions, thereby yielding enhanced sensitivity.
In one approach, the vent(s) may extend through the electret member. For example, a plurality of vents may extend through the electret member to fluidly interconnect the first and second portions of the hermetically-sealed, enclosed volume. In such an embodiment, the vents may be spaced in a symmetric manner about a center axis of the electret member.
In a further aspect, the implantable microphone may include a flexible, biocompatible diaphragm that defines a peripheral portion of the enclosed volume. Relatedly, the electret member may be spaced from the diaphragm and be of a flexible construction, wherein the output signal is indicative of acoustic signals that are generated by the diaphragm and incident upon the flexible electret member within enclosed volume of the microphone.
In such an arrangement, a first portion of the enclosed volume may be located on a first side of the back plate and a second portion of the enclosed volume may be located on a second side of the back plate. In turn, at least one vent may be provided through the back plate to fluidly interconnect the first and second portions. In one embodiment, a plurality of vents may extend through the back plate to fluidly interconnect the first and second portions. For example, the plurality of vents may be spaced in a symmetric manner about a center axis of the electret member.
In certain embodiments, the electret member may be provided so that the dielectric material displays a low surface conductance, e.g. a surface resistance of at least about 10 gigaohms, and preferably at least about 100 gigaohms. Additionally, the electret member and back plate may be provided to yield a capacitive coupling therebetween of at least 1 picofarad, and preferably at least 5 picofarad.
In yet another aspect, at least one of the electret member and the back plate may comprise a carrier, or support member. In this regard, the support member may be integrally defined by or separate from the electrically-conductive material portion and/or the dielectric material portion of the electret member, and/or integrally defined by or separate from the electrically conductive material portion of the back plate. For example, a dielectric material and/or electrically conductive material may be supportably disposed upon a support member (e.g. in layers applied thereto).
In some approaches, the electret member may be defined by applying a layer of electrically-conductive material (e.g. via a metallization process) on to a support substrate (e.g. a printed circuit board), and by applying a layer dielectric material (e.g. a Teflon-based material or glass) on to the support substrate or the electrically conductive layer (e.g. via a process in which the dielectric material is applied in a viscous or particulate state and then cured or dried). Similar techniques may be employed to define the electrically-conductive portion of the back plate. As may be appreciated, such approaches may facilitate the provision of an electret member and/or back plate having a desired thickness and/or profile.
In another aspect, the electret member may be defined by applying a dielectric material on to an electrically-conductive support member or on to a separate support member, and charging the dielectric material. In one embodiment, the charging step may occur at least partially contemporaneously with the applying step. For example, the dielectric material may be disposed via radio frequency (RF) sputtering to simultaneously complete the applying and charging steps.
In other embodiments, the dielectric material may be applied to an electrically-conductive support member or a separate support member via spraying, dipping, coating or chemical vapor deposition. In turn, the dielectric material may be charged by heating the dielectric material to a predetermined temperature (e.g. at or above a corresponding Curie temperature), applying a voltage to the heated material (e.g. at or above the corresponding Curie temperature), and then cooling the material. Alternatively, ion implantation and/or charged particle (e.g. bipolar or monopolar particles) corona spray techniques may be employed.
In a related aspect, the back plate may be advantageously positioned relative to a support member of the electret member prior to or immediately after charging of the dielectric material of the electret member, thereby enhancing maintenance of the static charge imparted to the electret member. For example, in one approach the electret member and back plate may be preassembled prior to charging the electret member, then charged and assembled with the balance of the implantable microphone componentry.
Additional aspects and corresponding advantages will be apparent to those skilled it the art upon consideration of the further description that follows.
As shown in
By way of example only, in a common source configuration, the electret member 10 and back plate of the diaphragm 20 may each be electrically interconnected to a preamplifier (e.g., a FET) that is powered by a separate power source (e.g., an implantable, rechargeable battery). In turn, the preamplifier output may provide an electret output signal. In turn, such output signal may be utilized to generate a drive signal for an implanted hearing aid instrument (e.g., an electromechanical or electromagnetic transducer for middle ear stimulation or a cochlear electrode array).
The electret member 10 may be of a non-flexible construction and disposed in fixed relation to the housing 30. Further, the electret member 10 may be electrically insulated from the housing 30 and back plate of flexible diaphragm 20 by one or more peripheral insulating member(s) 32. Such, peripheral member(s) 32, or other components, may also be disposed to engage and thereby facilitate positioning and tensioning of the diaphragm 20 at a desired distance h from the electret member 10, as shown in
The electret member 10 may comprise a charged dielectric material layer 12 and an electrode 14 (e.g., a metal plate or metallized support member). By way of example, the dielectric material layer 12 may comprise a permanently-charged, halocarbon polymer such as polyfluoroethylenepropylene. The diaphragm 20 may comprise an electrically-conductive material, e.g., a biocompatible metal such as titanium, wherein the diaphragm 20 may integrally define the back plate. In other arrangements, a separate metal layer defining the electrode of the back plate may be provided on an internal side of the diaphragm 20.
Referring now to
In one implementation, one side of an interconnection layer 16 may be adhesively interconnected to a T-shaped electrode 14, and a dielectric layer 12 may be adhesively interconnected to another side of the interconnection layer 16, wherein, the T-shaped electrode 14 supports the dielectric layer 12 and an interconnection layer 16 on a top portion 14a thereof, and further provides a bottom leg portion 14b for advantageously handling the electret member 10 free from user contact with an exposed top surface of the dielectric layer 12 during assembly.
The dielectric layer 12, electrode 14 and interconnection layer 16 may have interfacing portions of a coincidental configuration as illustrated in
In the latter regard, and as is best shown in
As shown in
A third portion 46 of the enclosed volume 40 may be utilized to house additional componentry of the implantable microphone 1, including for example electronic componentry for generating and/or conditioning an electret output signal. In this regard, and as shown in
In one method of assembly, the diaphragm 20 may be captured between the first and second clamp rings 34a and 34b upon interconnection therebetween (e.g. via laser welding), and such interconnected sub-assembly may be flipped relative to the orientation shown in
At some point in the assembly process, the assembled electret member 10 may be located relative to the mount member 60, as shown in
In turn, such interconnected subassembly may be flipped and located relative to the flipped sub-assembly comprising the interconnected first and second clamp rings 34a and 34b, diaphragm 20 and second peripheral member 32a. As may be appreciated, such an approach facilates positioning of the electret member 10 free from user contact with the dielectric material layer 12 of the electret member 10. After flipped positioning of the electret member 10, the first peripheral member 32b may be positioned to capture the mount 60 between the first peripheral member 32b and second peripheral member 32a. More particularly, complimentary threading 72 on the outer periphery of first peripheral member 32b and internal periphery of the second clamp ring 34b may be provided, wherein the first peripheral member 32b may be threadably advanced relative to the second clamp ring 34b so as to securely capture an outer annular portion 62 provided on the mount member 60. Subsequently, after disposing any desired additional componentry within the third portion 46 of the cup-shaped bottom 36, the top member 34 comprising peripheral members 34a and 34b, and the various componentry interconnected thereto described above, may be interconnected to the bottom member 36 (e.g. via laser welding).
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Various modifications and other embodiments to those described hereinabove will be apparent to those skilled in the art and are intended to be within the scope of the present invention.
This application claims priority to U.S. Provisional Application Ser. No. 60/989,179, filed Nov. 20, 2007, entitled “IMPLANTABLE ELECTRET MICROPHONE”, the entirety of which is hereby incorporated by reference.
Number | Date | Country | |
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60989179 | Nov 2007 | US |