[oooi ] This claims the benefit of U.S. Provisional Patent Application Serial Nos. 62/334,072, filed May 10, 2016, and 62/329,420, filed April 29, 2016, each of which is hereby incorporated by reference in its entirety.

Background of the Invention

[0002 ] This disclosure relates generally to microactuators (sometimes referred to as transducers). More particularly it relates to microactuators for use with fully implantable hearing aid systems.

[0003 ] Various different types of semi-implantable and fully-implantable hearing aids have been developed or proposed over the years. Cochlear implants utilize a direct electrical stimulation of the human cochlea to convey a perceivable signal to a human subject. Middle ear implants use mechanical stimulation of the ossicles or middle ear bones to convey a perceivable signal to a human subject. Air conduction hearing aids use a speaker element to create perceivable sound pressure signals in the air of the ear. Some implantable hearing aids have used a piezoelectric stack or pre-stressed piezoelectric materials to form a piezoelectric transducer having sufficient displacement to convey a perceivable signal to a human subject.

[0004 ] What is needed is an improved fully implantable hearing aid microactuator.

Summary of the Invention

[0005 ] A microactuator has a proximal end configured to receive an electrical signal and a distal end configured to be inserted into a fenestration of an otic bone to provide access through the lateral wall of the cochlea of a subject. The microactuator may include a piezoelectric transducer assembly having a piezoelectric transducer disposed on a membrane (the piezoelectric transducer having a smaller dimension than a corresponding dimension of the membrane), a silicone elastomer filled cavity with a seal at a first end to a first side of the piezoelectric transducer assembly and open at a second end, a second cavity containing a vacuum or a gas sealed at a first end to a second side of the piezoelectric transducer assembly and at a second end to an end cap. Brief Description of the Drawings

[0006 ] The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

[0007 ] FIG. 1 is a front elevational drawing of a fully implantable hearing aid microactuator in an implantable sleeve in accordance with an embodiment;

[0008 ] FIG. 2 is a cross-sectional drawing of the fully implantable hearing microactuator in an implantable sleeve of FIG. 1 taken along line 2-2 thereof;

[0009 ] FIG. 3 is an exploded front perspective view of a microactuator in accordance with an embodiment;

[0010 ] FIG. 4 is another exploded view of the microactuator of FIG. 3 from another perspective;

[0011 ] FIG. 5 is a front elevational view of a microactuator in accordance with an embodiment;

[0012 ] FIG. 6 is a cross-sectional view of the microactuator taken along line 6- 6 of FIG. 5;

[0013 ] FIG. 6A is a cross-sectional view similar to FIG. 6 of an alternative embodiment of the microactuator according to this invention;

[0014 ] FIG. 7 is a top plan view of a microactuator sleeve in accordance with an embodiment;

[0015 ] FIG. 8 is a cross-sectional view of the microactuator sleeve taken along line 8-8 of FIG. 7;

[0016 ] FIG. 9 is a cross-sectional view of the microactuator sleeve taken along line 9-9 of FIG. 7;

[0017 ] FIG. 10 is a top plan view of a microactuator in accordance with an embodiment;

[0018 ] FIG. 11 is a side elevational view of a microactuator in accordance with an embodiment;

[0019 ] FIG. 12 is a top plan view of a microactuator sleeve in accordance with an embodiment; [0020 ] FIG. 13 is a side elevational view of a microactuator sleeve in accordance with an embodiment;

[0021 ] FIG. 14 is a top plan view of a microactuator situated in an implantable sleeve in accordance with an embodiment;

[0022 ] FIG. 15 is a cut-away view of a microactuator in accordance with an embodiment; and

[0023 ] FIG. 16 is a process flow diagram illustrating steps for assembly of a microactuator in accordance with an embodiment.

Detailed Description of the Invention

[0024 ] Example embodiments are described herein in the context of a microactuator for use with a fully implantable hearing aid. Those of ordinary skill in the art will realize that the following description is illustrative only and is not intended to be in any way limiting. Other embodiments will readily suggest themselves to such skilled persons having the benefit of this disclosure. Reference will now be made in detail to implementations of the example embodiments as illustrated in the accompanying drawings. The same reference indicators will be used to the extent possible throughout the drawings and the following description to refer to the same or like items.

[0025 ] In the interest of clarity, not all of the routine features of the implementations described herein are shown and described. It will, of course, be appreciated that in the development of any such actual implementation, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with application and business-related constraints, and that these specific goals will vary from one implementation to another and from one developer to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking of engineering for those of ordinary skill in the art having the benefit of this disclosure.

[0026 ] Turning to the figures, FIG. 1 is a front elevational drawing of one embodiment of a fully implantable microactuator 10 having a proximal end 10a and a distal end 10b in accordance with an embodiment situated in an implantable sleeve 12. The implantable sleeve may be formed in a number of ways and implanted into the head of a subject so as to receive the microactuator 10.

[0027 ] FIG. 2 is a cross-sectional drawing of the microactuator 10 and sleeve 12 of FIG. 1 taken along line 2-2 thereof. Sleeve 12 is configured to have its narrow (or distal) end 14 inserted into a hole drilled into the otic bone within the cochlea of a subject and to be held in place there with an appropriate technology (e.g., adhesives, mechanical locking, interference fit, and the like). Microactuator 10 is locked to sleeve 12 in one embodiment with a biased bayonet-type locking structure comprising one or more pins 16 extending from microactuator 10 to engage one or more corresponding receiving slots 18 of sleeve 12. A partially compressed O-ring 20 (in one embodiment fabricated of silicone) is configured to provide an outward bias between microactuator 10 and sleeve 12 to hold the pin-slot bayonet-type locking structure engaged as well as to provide a liquid-tight seal. Sleeve 12 may therefore be installed first providing a microactuator receptacle, then microactuator 10 is installed into the receptacle and replaced from time to time as required for repair,

maintenance, and/or upgrades. A first gap 22 between sleeve 12 and microactuator 10 at the narrow end 14 of sleeve 12 may be, in one embodiment, about 0.05 mm. A second gap 24 between microactuator 10 and sleeve 12 in the area of compressed O- ring 20 may, in one embodiment, be about 0.24 mm (in this case with an O-ring having a nominal cross-sectional diameter of 0.051 mm and a nominal inner diameter of 1.21 mm.

[0028 ] Microactuator 10 further comprises a piezoelectric transducer membrane assembly 26 with a hot lead 28 coupled to a first electrical contact 30 and a ground lead 32 coupled to the case 34 of microactuator 10 and through that to a second electrical contact 36. First electrical contact 30 is insulated from case 34 of microactuator 10. Piezoelectric transducer membrane assembly 26 may comprise a cylindrical (circular axial cross-section) piezoelectric transducer 26a such as a lead zirconate titanate (PZT) crystal or stack of crystals (or other suitable piezoelectric material or materials) having a first diameter and a thin titanium membrane 26b of circular axial cross-section having a second, larger diameter to which piezoelectric transducer 26a is fixed. Making the piezoelectric transducer of smaller dimension than the membrane on which it is fixed provides an improved response by decoupling somewhat the piezoelectric transducer 26a from the case 34 through the flexible action of membrane 26b.

[0029 ] FIG. 3 is an exploded front perspective view of a microactuator 10 in accordance with an embodiment. From bottom to top the primary parts of the microactuator 10 are: feed through flange 38, microactuator end cap 40, piezoelectric transducer membrane assembly 26 (comprising piezoelectric transducer 26a and membrane 26b), microactuator flange 42 with pins 16 and plugs 44 (for plugging ports in pins 16), microactuator distal diaphragm 46 (formed in one embodiment of thin (19 microns +/-1 microns thick) titanium (a thickness range of about 5 microns to about 100 microns being appropriate), and O-ring 20. Distal Diaphragm 46 may be omitted in certain embodiments of this invention. Microactuator end cap 40 may be a ceramic feed-through that will form a hermetically sealed, back cavity 60 with the piezoelectric transducer membrane assembly 26 to isolate the piezoelectric transducer 26a electrically and so that it does not come into contact with the tissue of the subject. Back cavity 60 may be partially or totally evacuated or may alternatively contain a gas such as air, nitrogen, argon, helium or the like or a combination thereof. Microactuator flange 42 comprises in one embodiment a first proximal cylindrical portion 42a and a second cylindrical portion 42b coupled together, as, for example, with metal disk portion 42c. The second distal cylindrical portion 42b has a smaller diameter than the first proximal cylindrical portion 42a so that it can fit into sleeve 12 which is disposed through a fenestration in an otic bone to reach through the lateral wall of the cochlea of a subject. This arrangement allows the microactuator to stop at a predetermined amount of insertion into the sleeve which also has corresponding cylindrical portions of different diameters. The first proximal cylindrical portion 42a has a pair of ports 42d through pins 16 which allow liquid to be placed into cavity 54 formed inside microactuator flange 42 and then sealed with plugs 44 as described in more detail below.

[0030 ] Placing the piezoelectric transducer membrane assembly 26 between the back cavity 60 and the cavity 54 allows the piezoelectric transducer 26a to directly drive the relatively incompressible contents 54a contained in cavity 54 to, in turn, drive distal diaphragm 46, if included, the outside wall of which is in contact with the inside wall of the cochlea, to thereby impart the sensation of sound to the subject. Disposing a gas or vacuum in the back cavity 60 (on the opposite side of the piezoelectric transducer membrane assembly 26 from the cavity 54) reduces resistance to the vibratory motion of the piezoelectric transducer membrane assembly 26 to improve performance and reduce power draw.

[0031 ] FIG. 4 is another exploded view of microactuator 10 from another perspective.

[0032 ] FIG. 5 is a front elevational view of microactuator 10. FIG. 6 is a cross- sectional view thereof taken along line 6-6 of FIG. 5.

[0033 ] FIG. 7 is a top plan view of sleeve 12. FIG. 8 is a cross-sectional view taken along lines 8-8 of FIG. 7. FIG. 9 is a cross-sectional view taken along lines 9-9 of FIG. 7.

[0034 ] FIG. 10 is a top plan view of microactuator 10 in accordance with an embodiment.

[0035 ] FIG. 11 is a side elevational view of microactuator 10 in accordance with an embodiment.

[0036 ] FIG. 12 is a top plan view of sleeve 12 in accordance with an

embodiment.

[0037 ] FIG. 13 is a side elevational view of sleeve 12 in accordance with an embodiment.

[0038 ] FIG. 14 is a top plan view of microactuator 10 situated in sleeve 12 in accordance with an embodiment.

[0039 ] FIG. 15 is a cut-away view of microactuator 10 in accordance with an embodiment.

[0040 ] A sealant cavity 48 (initially open at the top) is defined at an outer periphery by the inside of feed-through flange 38 and is in one embodiment filled with a silicone sealant material (although those of ordinary skill in the art will now realize that other suitable sealant materials may be used instead). This sealant material protects first and second electrical contacts (30, 36), provides strain relief for microactuator lead wires 50 which couple microactuator 10 to other hearing aid component (not shown) and seals the proximal end 52 of microactuator 10 from moisture infiltration.

[0041 ] Cavity 54 configured to contain body 54a as discussed above is defined at an outer periphery by the inside wall of narrow portion 56 of microactuator 10 at a distal end 58 of microactuator 10, and at a proximal end by piezoelectric transducer membrane assembly 26. Cavity 54 may be filled as described in more detail below in order to improve performance of the microactuator in conveying the impression of sound to the inner ear of a subject.

[0042 ] In one embodiment the piezoelectric transducer 26a has a thickness along a longitudinal axis in a range of from about 25 microns to about 500 microns with 100 microns used in one example, the membrane 26b has a thickness in a range of from about 5 microns to about 100 microns with 25 microns used in one example, and the diaphragm 46, if included, has a thickness in a range of from about 5 microns to about 100 microns with 19 microns +/-1 microns used in one example. In one embodiment the piezoelectric transducer 26a is soldered to the membrane 26b.

[0043 ] FIG. 16 a process flow diagram illustrating a method for constructing microactuator 10. First (62), form microactuator flange 42 as described above out of an appropriate biocompatible material such as titanium.

[0044 ] Second (64), laser weld microactuator distal diaphragm 46 to the distal (narrow) end of microactuator flange 42 along the outside edge of diaphragm 46. This step maybe omitted in some embodiments.

[0045 ] Third (66), attach (which may be accomplished with a laser weld) one end of hot lead (which may comprise gold such as gold wirebond) 28 to piezoelectric transducer membrane assembly 26 and a second end of hot lead 28 to first electrical contact 30 on microactuator end cap 40 which is nearest to piezoelectric transducer membrane assembly 26.

[0046 ] Fourth (68), assemble the flange assembly 42, the piezoelectric transducer membrane assembly 26 and the microactuator end cap 40 to form a partial microactuator assembly 42, 26, 40. This step may be performed by

sandwiching the piezoelectric transducer membrane assembly 26 with (on one side) the microactuator end cap 40 and (on the other side) the flange assembly 42 in a fixture to hold them together during a laser welding operation. This laser weld may be performed by rotating the fixture while welding along the intersection of the microactuator end cap 40, the piezoelectric transducer membrane assembly 26 and the flange assembly 42. This completes the back cavity which is a cavity filled as described and located between the piezoelectric transducer membrane assembly 26 and microactuator end cap 40. It also creates the cavity 54. The back cavity may be evacuated, partially evacuated or filled with a selected gas or gasses at this time by conducting the operation in an environment which is evacuated or filled with the selected gas or gasses.

[0047 ] Fifth (70), mount the partial microactuator assembly 42, 26, 40 and feed-through flange 38 into a fixture and perform a circumferential weld joining these two components. The feed-through flange 38 provides strain relief for the microactuator lead wires 50, defines the sealant cavity 48 and provides a retainer for the silicone sealant used to electrically isolate the connection between the microactuator lead wires 50 and microactuator end cap 40.

[0048 ] Sixth (72), fill the cavity 54 with a silicone elastomer using a suitable method (see FIG. 6A). If the diaphragm 46 is omitted as in some embodiments of this invention as shown in FIG. 6A, the silicone elastomer in the cavity 54 retains its shape within the cavity 54. The silicone elastomer proximate the distal end 58 of microactuator 10 is in proximity to or contact with the inner ear of the wearer or the inside wall of the cochlea to thereby impart the sensation of sound to the subject without interference or attenuation by the diaphragm 46. The silicone elastomer retains its shape in the cavity 54 so diaphragm 46 is not needed.

[0049 ] Seventh (74), seal the fluid cavity as follows. Plugs 44 are inserted into the ports 42d and laser welded to hermetically seal them. The laser welding forms a seal before the heat from the welding can appreciably heat the content in the cavity 54. A single port 42d and corresponding plug 44 could be used as could more than two ports 42d and corresponding plugs 44 as will now be apparent to those of ordinary skill in the art having the benefit of this disclosure.

[0050 ] Eighth (76), attach the microactuator lead wires 50 to first and second electrical contacts 30, 36 at the outside of the microactuator. This may be performed by a laser weld.

[0051 ] Ninth (78), fill the sealant cavity 48 with silicone sealant material and cure it.

[0052 ] Tenth (80), place the silicone O-ring 20 on the narrow portion 56 of microactuator flange 42 so it is at the location where the outer diameter of the microactuator flange 42 changes from a smaller diameter to a larger diameter (as shown). O-ring 20 is configured to create a moisture-tight seal between the microactuator 10 and the sleeve 12 which holds it in place within the cochlea of the subject. This step may be performed at any time prior to installation. [0053 ] While steps 1-10 above have been set forth in one order, those of ordinary skill in the art having the benefit of this disclosure will now realize that the steps could be broken down into sub-steps and that the steps and/or sub-steps may be performed in any convenient order in a production environment.

[0054 ] As described above, all surfaces in contact with the body of the subject may be of medical grade titanium except the medical grade silicone which may be used in the sealant cavity and Ethylene Tetrafluoroethylene (ETFE) which is a biocompatible material which may be used for insulating the microactuator lead wires 50.

[0055 ] While embodiments and applications have been shown and described, it would be apparent to those skilled in the art having the benefit of this disclosure that many more modifications than mentioned above are possible without departing from the inventive concepts disclosed herein. The invention, therefore, is not to be restricted except in the spirit of the appended claims.

[0056 ] From the above disclosure of the general principles of this invention and the preceding detailed description of at least one embodiment, those skilled in the art will readily comprehend the various modifications to which this invention is susceptible. Therefore, I desire to be limited only by the scope of the following claims and equivalents thereof.

[0057 ] I claim: