Actuator with coupling plates

Abstract

An apparatus includes a piezoelectric element having a plurality of piezoelectric layers, a first portion, and a second portion spaced from the first portion along a longitudinal axis of the piezoelectric element that is substantially perpendicular to the piezoelectric layers. The apparatus further includes circuitry in electrical communication with the piezoelectric element and configured to apply non-zero voltage differences between the first portion and the second portion that induce time-varying changes of an attribute of the piezoelectric element. The apparatus further includes a first mount in mechanical communication with the first portion and a second mount in mechanical communication with the second end portion. The second mount is spaced from the first mount. The first mount is configured to be rigidly affixed to a first outer bone surface region and the second mount is configured to be rigidly affixed to a second outer bone surface region.

Description

COCLR.095WO PCT APPLICATION ACTUATOR WITH COUPLING PLATESBACKGROUNDField

[0001] The present application relates generally to an implantable actuator for generating vibrations, and more specifically, to implantable auditory prostheses for generating auditory vibrations.Description of the Related Art

[0002] Medical devices are devices that are intended to be used for medical purposes. They can vary in both their intended use and indications for use. Examples range from simple, low-risk medical supplies, such as tongue depressors, medical thermometers, disposable gloves, and bedpans, to complex, potentially high-risk devices that are implanted and / or sustain life, such as deep brain stimulators and cardiac stents. Other categories of medical devices include diagnostic equipment, such as x-ray machines and ultrasound scanners, life support equipment, such as mechanical ventilators and dialysis machines.

[0003] Hearing devices act on an actual or potential auditory perception of an individual, including to improve perception of sound signals, to reduce perception of sound signals, etc. In particular, a hearing device can deliver sound signals to a user in any form, including in the form of acoustical stimulation, mechanical stimulation, electrical stimulation, etc., and / or can operate to suppress all or some sound signals. As such, a hearing device can be a device for use by a hearing-impaired person (e.g., hearing aids, middle ear auditory prostheses, bone conduction devices, direct acoustic stimulators, electroacoustic hearing prostheses, auditory brainstem stimulators, bimodal hearing prostheses, bilateral hearing prostheses, dedicated tinnitus therapy devices, tinnitus therapy devices, etc.) or a device for use by a person with normal hearing (e.g., consumer devices that provide audio streaming, consumer headphones, earphones and other listening devices), a hearing protection device, etc.SUMMARY

[0004] In one aspect disclosed herein, an apparatus comprises a piezoelectric element comprising a plurality of piezoelectric layers. The piezoelectric element has a first portion and a second portion spaced from the first portion along a longitudinal axis of thepiezoelectric element that is substantially perpendicular to the piezoelectric layers. The apparatus further comprises circuitry in electrical communication with the piezoelectric element. The circuitry is configured to apply non-zero voltage differences between the first portion and the second portion. The non-zero voltage differences induce time-varying changes of an attribute of the piezoelectric element. The apparatus further comprises a first mount in mechanical communication with the first portion and a second mount in mechanical communication with the second end portion. The second mount is spaced from the first mount. The first mount is configured to be rigidly affixed to a first outer bone surface region and the second mount is configured to be rigidly affixed to a second outer bone surface region.

[0005] In another aspect disclosed herein, a method comprises providing an actuator comprising a plurality of piezoelectric layers and two end anchors spaced from one another along a direction substantially perpendicular to the piezoelectric layers. The method further comprises mounting the two end anchors to be in mechanical communication with corresponding portions of an outer bone surface of a recipient’s body with the direction substantially parallel to the portions of the outer bone surface.

[0006] In another aspect disclosed herein, an apparatus comprises a mass free actuator comprising a piezoelectric element configured to expand and contract along a longitudinal axis in response to applied voltages. The apparatus further comprises a first anchor in mechanical communication with a first end portion of the mass free actuator and a second anchor in mechanical communication with a second end portion of the mass free actuator opposite to the first end portion. The first anchor is configured to be rigidly affixed to a first cortical bone surface region having a surface area in a range of 6 mm2to 400 mm2and the second anchor is configured to be rigidly affixed to a second cortical bone surface region having a surface area in a range of 6 mm2to 400 mm2.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Implementations are described herein in conjunction with the accompanying drawings, in which:

[0008] FIG. 1A schematically illustrates a top view of an example apparatus in accordance with certain implementations described herein;

[0009] FIG. IB schematically illustrates a perspective view of an example apparatus configured to be implanted within a cavity at an outer bone surface in accordance with certain implementations described herein;

[0010] FIG. 1C schematically illustrates a perspective view of an example apparatus configured to be implanted within an implantable structure at an outer bone surface in accordance with certain implementations described herein;

[0011] FIG. ID schematically illustrates an example apparatus in which the piezoelectric element is contained within the housing and comprises a plurality of piezoelectric layers and a plurality of electrodes in accordance with certain implementations described herein;

[0012] FIGs. 2A-2D schematically illustrate various example first and second mounts in accordance with certain implementations described herein.

[0013] FIGs. 3A-3D schematically illustrate cross-sectional side views of example apparatus rigidly affixed to an outer bone surface in accordance with certain implementations described herein;

[0014] FIGs. 4A-4D schematically illustrate cross-sectional side views of portions of example apparatus rigidly affixed to the bone in accordance with certain implementations described herein; and

[0015] FIGs. 5A-5C are flow diagrams of examples of a method for implanting an apparatus in accordance with certain implementations described herein.DETAILED DESCRIPTION

[0016] Certain implementations described herein provide a bone conductor actuator (e.g., a mass free actuator) configured to be mechanically coupled to an outer bone surface (e.g., cortical bone tissue that is harder, has a higher bone mass density, and is more conducive to vibrational energy propagation than is deeper diploe bone tissue). Mounting plates on either end of the actuator are rigidly affixed to the outer bone surface and can provide a sufficiently large fixation area with the underlying bone surface to facilitate vibrational energy transfer from the piezoelectric element into the bone and to reduce the risk of shear failure. In addition, by using the mounting plates, implantation of the bone conductor actuator can be simpler (e.g., less complex) and less dependent on high surgical accuracy than other mounting configurations. One or more of these aspects are applicable tosenaory prosthesis systems (e.g., auditory prosthesis systems; visual implants such as bionic eyes), sleep disorder systems (e.g., sleep apnea systems), seizure systems (e.g., systems for monitoring and / or treating epileptic events), balance or movement disorder systems (e.g., vestibular stimulation systems), and / or tinnitus management systems.

[0017] There are a number of different types of devices in / with which the techniques presented herein can be implemented. Merely for ease of description, the techniques presented herein are primarily described with reference to a specific device. However, it is to be appreciated that the techniques presented herein can also be partially or fully implemented by any of a number of different types of devices or systems, including consumer electronic devices (e.g., consumer hearing devices, consumer computing devices such as mobile phones and tablets, audio equipment such as home theatre and car audio systems, etc.), computing systems (e.g., servers in data centers, Internet-of-Things (loT) devices), various types of software systems, such as databases, machine learning and artificial intelligence systems, other medical devices, such as diagnostic equipment or life sustaining equipment, etc. For example, the techniques presented herein could be used in or with sensory protheses, including hearing aids and cochlear implants, and various medical devices, such as pacemakers, drug delivery systems, implantable defibrillators, functional electrical stimulation devices, sleep disorder devices (e.g., sleep apnea devices), seizure devices (e.g., devices for monitoring and / or treating epileptic events), balance or movement disorder devices (e.g., vestibular stimulation devices), tinnitus management devices, visual implants (e.g., bionic eyes), etc.

[0018] The teachings detailed herein are applicable, in at least some implementations, to any type of implantable stimulation and / or measurement system or device (e.g., implantable vibration stimulation system or device; bone conduction auditory prosthesis) comprising a first portion implanted on or within the recipient’s body and configured to provide vibrations to a portion of the recipient’s body. Implementations can include any type of medical device that can utilize the teachings detailed herein and / or variations thereof. Furthermore, while certain implementations are described herein in the context of implantable auditory prosthesis devices, certain other implementations are compatible in the context of other implantable or non-implantable devices or systems (e.g.,bone conduction headphones; bone conduction speakers; bone conduction microphones; ultrasonic imaging).

[0019] Merely for ease of description, apparatus and methods disclosed herein are primarily described with reference to an illustrative medical device, namely an active transcutaneous or percutaneous bone conduction auditory prosthesis system. However, the teachings detailed herein and / or variations thereof may also be used with a variety of other medical or non-medical systems that provide a wide range of therapeutic benefits to recipients, patients, or other users. In some implementations, the teachings detailed herein and / or variations thereof can be utilized in other types of devices beyond auditory prostheses that may benefit from a vibration-generating actuator and / or other transducer assemblies including but not limited to: electro-acoustic electrical / acoustic systems, cochlear implant devices, implantable hearing aid devices, middle ear implant devices, bone conduction devices (e.g., active bone conduction devices; passive bone conduction devices, percutaneous bone conduction devices; transcutaneous bone conduction devices), Direct Acoustic Cochlear Implant (DACI), middle ear transducer (MET), electro-acoustic implant devices, other types of auditory prosthesis devices, and / or combinations or variations thereof, or any other suitable hearing prosthesis system with or without one or more external components. Implementations can include any type of auditory prosthesis that can utilize the teachings detailed herein and / or variations thereof. Certain such implementations can be referred to as “partially implantable,” “semi-implantable,” “mostly implantable,” “fully implantable,” or “totally implantable” auditory prostheses. In some implementations, the teachings detailed herein and / or variations thereof can be utilized in other types of prostheses beyond auditory prostheses.

[0020] While certain implementations are described herein in the context of auditory prosthesis devices configured to evoke a sensory percept (e.g., hearing), certain other implementations are compatible in the context of various types of sensory prosthesis systems that are configured to evoke corresponding other types of neural or sensory (e.g., sight, tactile, smell, taste) percepts are compatible with certain implementations described herein, including but are not limited to: vestibular devices (e.g., vestibular implants; balance or movement disorder system), tinnitus management system, visual devices (e.g., bionic eyes), visual prostheses (e.g., retinal implants), somatosensory implants, and chemosensoryimplants. Certain other implementations are compatible with other types of medical devices that can utilize the teachings detailed herein and / or variations thereof to provide a wide range of therapeutic benefits to recipients, patients, or other users (e.g., epilepsy or seizure monitoring systems; pain control systems; bladder control systems; sleep disorder or sleep apnea control systems; neurostimulators; pacemakers), to perform monitoring or measuring functionalities (e.g., electroencephalogram monitoring of brain function; electrocardiogram monitoring of heart function), or other medical implants comprising a rechargeable implanted power source. Certain other implementations are compatible with other non-medical devices or system (e.g., consumer electronic devices).

[0021] FIG. 1A schematically illustrates a top view of an example apparatus 100 in accordance with certain implementations described herein. FIG. IB schematically illustrates a perspective view of an example apparatus 100 configured to be implanted within a cavity 54 at an outer bone surface 52 of the at least one bone 50 in accordance with certain implementations described herein. FIG. 1C schematically illustrates a perspective view of an example apparatus 100 configured to be implanted within an implantable structure (e.g., housing 150) at an outer bone surface 52 of the at least one bone 50 in accordance with certain implementations described herein. The apparatus 100 comprises a piezoelectric element 110 (e.g., bone conduction actuator) comprising a plurality of piezoelectric layers 112, the piezoelectric element 110 having a first portion 114 and a second portion 116 spaced from the first portion 114 along a longitudinal axis 111 of the piezoelectric element 110 that is substantially perpendicular to the piezoelectric layers 112. For example, the longitudinal axis 111 of the piezoelectric element 110 can be an axis along a length of the piezoelectric element 110 or an axis about which the piezoelectric element 110 is at least partially symmetric. The apparatus 100 further comprises circuitry 120 in electrical communication with the piezoelectric element 110. The circuitry 120 is configured to apply non-zero voltage differences between the first portion 114 and the second portion 116, the non-zero voltage differences inducing time-varying changes of an attribute of the piezoelectric element 110. The apparatus 100 further comprises a first mount 130 in mechanical communication with the first portion 114 and a second mount 140 in mechanical communication with the second portion 116, the second mount 140 spaced from the first mount 130. The first mount 130 isconfigured to be rigidly affixed to a first outer bone surface region 52a and the second mount 140 configured to be rigidly affixed to a second outer bone surface region 52b.

[0022] In certain implementations, the apparatus 100 comprises an implantable component or portion of an active transcutaneous bone conduction device implanted in a recipient in accordance with certain implementations described herein. The transcutaneous bone conduction device can be configured to compensate for conductive hearing loss, mixed hearing loss, or single-sided deafness. In certain such implementations, the time-varying changes of the attribute of the piezoelectric element 110 generate vibrational signals 160 (e.g., vibrational energy; vibrations; auditory vibrations) over a range of vibrational frequencies (e.g., within a range of vibrational frequencies that are perceptible by the recipient as sound; a range of 20 Hz to 20 kHz). The vibrational signals 160 can be configured to propagate through the at least one bone 50 and to evoke a sensory percept (e.g., a hearing percept) by the recipient. For example, the vibrational signals 160 can propagate via bone conduction (e.g., in two substantially opposite directions) from the piezoelectric element 110 to an inner ear region (e.g., within the temporal bone and comprising the vestibule, the cochlea, and the semicircular canals) and / or a middle ear region (e.g., within the recipient’s head, partially bounded by the tympanic membrane and comprising the ossicles, the round window, the oval window, and the Eustachian tube) to be detected by the recipient as sound.

[0023] The transcutaneous bone conduction device can include an external component and an implantable component which comprises the apparatus 100. For example, the implantable component can include a vibrating actuator assembly in mechanical communication with bone tissue (e.g., skull) of the recipient’s body and configured to convert electrical signals generated by at least one sound input element of the transcutaneous bone conduction device into vibrational stimuli and to deliver the vibrational stimuli to the bone tissue. For example, the vibrating actuator assembly can be rigidly attached to (e.g., in direct contact with) the outer surface of the recipient’s skull bone such that vibrations generated by the vibrating actuator assembly are transmitted to the recipient’s bone and detected by the recipient’s ossicles and / or cochlea to evoke a hearing percept. The external component and the implantable component can be in wireless communication with one another via a magnetic inductance link (e.g., comprising a communication coil of the externalcomponent in wireless communication with a communication coil of the implantable component).

[0024] In certain implementations, the at least one sound input element comprises at least one microphone configured to generate the electrical signals in response to sound received by the at least one microphone. For example, the at least one microphone can comprise at least one external microphone located outside the recipient’s body (e.g., on an outer surface of the recipient’s skin) and / or at least one internal microphone located within the recipient’s body (e.g., beneath the outer surface recipient’s skin). In certain other implementations, the at least one sound input element comprises a device configured to receive signals indicative of sound from an audiovisual device.

[0025] The transcutaneous bone conduction device can include sound processing circuitry (e.g., in the external component, in the internal component, or divided among both the external and internal components) configured to process the electrical signals from the at least one sound input element, and to provide the processed signals to the vibrating actuator to be converted into the vibrational stimuli. For example, the sound processing circuitry can receive and process the electrical signals (e.g., applying one or more of digitization, shifting, shaping, amplification, compression, filtering, and / or other signal conditioning to the electrical signals).

[0026] In certain implementations, the apparatus 100 is configured to be in mechanical communication with at least one bone 50 (e.g., temporal bone area posterior to the ear canal) of a recipient’s body. In certain implementations, as shown in FIG. 1A, the apparatus 100 comprises a housing 150 (e.g., casing) containing the piezoelectric element 110 (e.g., oscillator; vibrating actuator) and the housing 150 is configured to be implanted on or within the at least one bone 50 of the recipient’s body. For example, as shown in FIG. IB, the apparatus 100 can be configured to be implanted with the housing 150 at least partially within a cavity 54 (e.g., machined during a surgical procedure; naturally-occurring) in the at least one bone 50 (e.g., temporal bone; skull bone). For another example, as shown in FIG.1C, the apparatus 100 can be configured to be implanted with the housing 150 on an outer bone surface 52 of the at least one bone 50.

[0027] In certain implementations, the housing 150 is configured to hermetically seal the piezoelectric element 110 from an environment surrounding the housing 150. Thehousing 150 can have a length (e.g., along the longitudinal axis 111) and / or a width (e.g., substantially perpendicular to the length) less than or equal to 30 millimeters (e.g., in a range of 15 millimeters to 25 millimeters; in a range of 10 millimeters to 30 millimeters), and / or a thickness less than or equal to 7 millimeters (e.g., in a range of less than or equal to 6 millimeters, in a range of less than or equal to 5 millimeters; in a range of less than or equal to 4 millimeters). In certain implementations, the housing 150 is at least partially symmetric about the longitudinal axis 111, while in certain other implementations, the housing 420 is non-symmetric relative to the longitudinal axis 111. The housing 150 of certain implementations comprises at least one biocompatible material (e.g., plastic; PEEK; silicone; titanium; titanium alloy; ceramic; zirconium oxide).

[0028] In certain implementations, the housing 150 is configured to be rigidly affixed to the piezoelectric element 110 and at least a portion of the housing 150 is configured to flex (e.g., expand and contract) in response to expansions and contractions of the piezoelectric element 110. For example, the housing 150 can comprise one or more walls that are sufficiently thin to be compliant (e.g., flexible; bendable; stretchable) in response to the expansion and / or contraction of the piezoelectric element 110 and one or more walls that are sufficiently thick to provide structural rigidity to support the piezoelectric element 110.

[0029] In certain implementations, the attribute having the time- varying changes comprises a length of the piezoelectric element 110 along the longitudinal axis 111. As shown in FIG. 1A, the first portion 114 can comprise a first end of the piezoelectric element 110, the second portion 116 can comprise a second end of the piezoelectric element 110 spaced from the first end along the longitudinal axis 111 of the piezoelectric element 110, and the attribute can comprise a length of the piezoelectric element 110 along the longitudinal axis 111. In certain implementations, as shown in FIGs. 1A-1C, the piezoelectric element 110 is configured to be implanted such that the longitudinal axis 111 of the piezoelectric element 110 is substantially parallel to the outer bone surface 52 (e.g., substantially parallel to the first outer bone surface region 52a and / or the second outer bone surface region 52b).

[0030] FIG. ID schematically illustrates an example apparatus 100 (e.g., a mass free bone conduction actuator) in which the piezoelectric element 110 (e.g., piezoelectric stack) is contained within the housing 150 and comprises a plurality of piezoelectric layers112 and a plurality of electrodes 118 in accordance with certain implementations described herein. The piezoelectric layers 112 and the electrodes 118 alternate with one another along the length of the piezoelectric element 110 (e.g., axially stacked along the longitudinal axis 111) such that each piezoelectric layer 112 (e.g., having a thickness along the longitudinal axis 111 in a range of 10 microns to 30 microns) of the plurality of piezoelectric layers 112 is sandwiched between a pair of electrodes 118 (e.g., electrically conductive layers having thicknesses along the longitudinal axis 111 in a range of 2 microns to 10 microns) of the plurality of electrodes 118.

[0031] In certain implementations, the piezoelectric element 110 comprises a piezoelectric stack (e.g., column, post, or cylinder) comprising a plurality of piezoelectric layers 112. Each piezoelectric layer 112 can be substantially perpendicular to the longitudinal axis 111 and configured to expand and contract along an axial direction (e.g., substantially parallel to the longitudinal axis 111) in response to electrical voltage signals applied to the piezoelectric element 110 (e.g., the non-zero voltage difference V). For example, as shown in FIG. ID, the circuitry 120 can be in electrical communication with the plurality of electrodes 118 and can be configured to apply the non-zero voltage differences V to induce the time-varying changes 124 of the length of the piezoelectric element 110 (e.g., the thicknesses of the piezoelectric layers 112 along the longitudinal axis 111) extending from the first portion 114 of the piezoelectric element 110 to the second portion 116 of the piezoelectric element 110. The non-zero voltage differences V can comprise a non-zero direct current (DC) voltage component VDC corresponding to an expansion of the length and an alternating current (AC) voltage component VAC corresponding to time-varying expansions and contractions of the length that generate vibrational signals 160 that propagate through the at least one bone 50.

[0032] In certain other implementations, the attribute having the time-varying changes comprises a curvature of the piezoelectric element 110 (e.g., curvature of the plurality of piezoelectric layers 112). For example, the piezoelectric element 110 can comprise a slab, sheet, or plate comprising one or more piezoelectric layers 112. Each piezoelectric layer 112 can be substantially perpendicular to the longitudinal axis 111 and configured to expand and contract along a radial direction (e.g., substantially orthogonal to the longitudinal axis 111 ) in response to electrical voltage signals applied to the piezoelectricelement 110 (e.g., the non-zero voltage difference A V). For example, the circuitry 120 can be in electrical communication with the plurality of electrodes 118 and can be configured to apply the non-zero voltage differences AV to induce time-varying changes 124 of the curvature of the piezoelectric element 110 (e.g., bending of the piezoelectric element 110). For example, different piezoelectric layers 112 can expand and contract by differing amounts relative to one another such that the piezoelectric element 110 bends in response to the nonzero voltage differences AV. The non-zero voltage differences AV can comprise a non-zero direct current (DC) voltage component VDC corresponding to a constant curvature and an alternating current (AC) voltage component VAC corresponding to time-varying curvatures (e.g., varying between more curvature than the constant curvature and less curvature than the constant curvature) that generate vibrational signals 160 that propagate through the at least one bone 50.

[0033] In certain implementations, the piezoelectric element 110 comprises a unitary (e.g., single; monolithic) component. For example, the piezoelectric layers 112 can comprise two or more sub-layers in mechanical communication with one another (e.g., bonded together) into a unitary component, at least one of the sub-layers comprising a piezoelectric material (e.g., unimorph having one piezoelectric sub-layer and a nonpiezoelectric sub-layer; bimorph having two or more piezoelectric sub-layers). The piezoelectric element 110 can comprise other non-piezoelectric materials, such as a bonding material (e.g., adhesive; epoxy; metal) between piezoelectric sub-layers, and the electrically conductive electrodes 118 (e.g., metal) that are configured to apply the non-zero voltage differences to the piezoelectric layers 112. In certain implementations, the number of piezoelectric layers 112 is selected to provide a predetermined power, size (e.g., area, thickness), stiffness, and / or resonance frequency. Examples of piezoelectric materials compatible with certain implementations described herein include but are not limited to: quartz; gallium orthophosphate; langasite; barium titanate; lead titanate; lead zirconate titanate (PZT); potassium niobate; lithium niobate; lithium tantalate; sodium tungstate; sodium potassium niobate; bismuth ferrite; sodium niobate; polyvinylidene fluoride; macro fiber composite (MFC); other piezoelectric crystals, ceramics, or polymers.

[0034] The piezoelectric element 110 can have a cross-sectional shape (e.g., circular; rectangular; square; oval; polygonal with 5, 6, 7, 8, or more sides; regular; irregular)in a plane substantially perpendicular to the longitudinal axis 111 and can be substantially symmetric about the longitudinal axis 111. The piezoelectric element 110 can have a length along the longitudinal axis 111 (e.g., in a range of 2 millimeters to 20 millimeters; in a range of 3 millimeters to 10 millimeters), a width substantially perpendicular to the length (e.g., in a range of 2 millimeters to 20 millimeters), and a thickness substantially perpendicular to the length and to the width (e.g., in a range of less than 2 millimeters; less than 1 millimeter; greater than 300 microns). Various configurations and geometries of the piezoelectric element 110 are compatible with certain implementations described herein (see, e.g., “Piezoelectric Ceramic Products: Fundamentals, Characteristics and Applications,” Physik Instruments (PI) GmbH & Co., Lederhose, Germany, www.piceramic.com, (2016)).

[0035] In certain implementations, the circuitry 120 comprises at least one microcontroller configured to receive data and / or control signals indicative of the non-zero voltage differences to be applied between the first and second portions 114,116 of the piezoelectric element 110 and to generate the non-zero voltage differences in response to the received data and / or control signals. The at least one microcontroller can comprise at least one application-specific integrated circuit (ASIC) microcontroller, digital signal processing (DSP) microcontroller, generalized integrated circuits programmed by software with computer executable instructions, and / or microcontroller core. In certain implementations, the circuitry 120 comprises and / or is in operative communication with storage circuitry configured to store information (e.g., data; commands) accessed by the circuitry 120 during operation (e.g., while providing the functionality of certain implementations described herein). The storage circuitry can comprise at least one tangible (e.g., non-transitory) computer readable storage medium, examples of which include but are not limited to: read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory. The storage circuitry can be encoded with software (e.g., a computer program downloaded as an application) comprising computer executable instructions for instructing the circuitry 120 (e.g., executable data access logic, evaluation logic, and / or information outputting logic). In certain implementations, the circuitry 120 executes the instructions of the software to provide functionality as described herein. The circuitry 120 of certain implementations further comprises other digital circuitry (e.g., registers; filters; output controllers; memory controllers).

[0036] In certain implementations, at least a portion of the circuitry 120 can be within the housing 150 and / or at least a portion of the circuitry 120 can be outside the housing 150. For example, the circuitry 120 can comprise first circuitry (e.g., a first microcontroller) within the housing 150 and electrically connected to the electrodes 118 and second circuitry (e.g., a second microcontroller) in a second housing (e.g., casing) in electrical communication with the first circuitry. The second circuitry can be configured to provide power, data, and / or control signals to the first circuitry within the housing 150. In certain implementations, the second housing is implanted within the recipient’s body separate from the housing 150 and the electrical communication between the first and second circuitry is through one or more electrical conduits (e.g., wires) extending between the housing 150 and the second housing. In certain other implementations, the second housing is part of a device external to the recipient’s body (e.g., worn on the recipient’s body) and the electrical communication between the first and second circuitry is via a wireless communication channel (e.g., a transcutaneous inductive radio frequency (RF) communication link between the apparatus 100 and the external device), across which the apparatus 100 receives power, data, and / or control signals from the device. The second circuitry of certain implementations can comprise a device separate from both an externally worn device and the implanted apparatus 100 (e.g., smartphone; smart tablet; smart watch; other remote device operated by the recipient and in communication with the externally worn device and / or the implanted apparatus 100).

[0037] In certain implementations, the circuitry 120 comprises a single amplifier configured to apply both the non-zero DC voltage component and the AC voltage component between the first and second portions 114,116. In certain other implementations, the circuitry 120 comprises a first amplifier configured to apply the non-zero DC voltage component between the first and second portions 114,116 and a second amplifier configured to apply the AC voltage component between the first and second portions 114,116. The first amplifier and the second amplifier can have substantially equal resolutions or the second amplifier can have a higher resolution than does the first amplifier. In certain implementations, the first and second amplifiers are in series electrical connection with one another, while in certain other implementations, the first and second amplifiers are in parallel electrical connection with one another. For example, the first amplifier can have asufficiently high electrical impedance such that the oscillating data signals (e.g., audio data signals) do not drive the first amplifier but do drive the second amplifier. The AC voltage component generated by the second amplifier can ride on the non-zero DC voltage component generated by the first amplifier.

[0038] In certain implementations, the first mount 130 and / or the second mount 140 comprises at least one biocompatible material (e.g., plastic; PEEK; silicone; titanium; titanium alloy; ceramic; zirconium oxide) and is sufficiently rigid to transmit the vibrational signals 160 from the piezoelectric element 110 and the housing 150 to the bone 50. In certain implementations, the first mount 130 and the second mount 140 comprise the same at least one biocompatible material, while in certain other implementations, the first mount 130 and the second mount 140 comprise different biocompatible materials. The at least one biocompatible material of the first and / or second mounts 130,140 can be the same as the at least one biocompatible material as the housing 150. At least one of the first mount 130 and the second mount 140 can be an integral portion of the housing 150.

[0039] In certain implementations, the first mount 130 and the second mount 140 are configured to be rigidly affixed to the first and second outer bone surface regions 52a, b, respectively, such that the vibrational signals 160 generated by the time-varying changes of the attribute of the piezoelectric element 110 are transmitted to the outer bone surface 52 and propagate through the at least one bone 50. For example, as shown in FIGs. 1A-1D, each of the first mount 130 and the second mount 140 can comprise at least one lamina (e.g., slab; sheet; plate) configured to extend across the first outer bone surface region 52a and the second outer bone surface region 52b, respectively. The at least one lamina of the first mount 130 and / or the second mount 140 can have a thickness T in a direction substantially perpendicular to the first outer bone surface region 52a and / or the second outer bone surface region 52b, respectively (e.g., in a range of 10 microns to 100 microns).

[0040] In certain implementations, the at least one lamina of the first mount 130 and / or the second mount 140 is configured to extend across the outer bone surface 52 in at least one direction having a component substantially parallel to the longitudinal axis 111. For example, the at least one lamina of the first mount 130 and / or the second mount 140 can have a length L substantially parallel to the longitudinal axis 111 in a range of 3 millimeters to 20 millimeters (e.g., in a range of 5 millimeters to 10 millimeters). The at least one laminaof the first mount 130 and / or the second mount 140 can have a width W substantially perpendicular to the length, the width W in a range of 2 millimeters to 20 millimeters; (e.g., in a range of 5 millimeters to 10 millimeters). In certain implementations, the width W is substantially equal to a width of the housing 150 (e.g., as shown in FIGs. 1A-1D), while in certain other implementations, the width W is less than the width of the housing 150 or greater than the width of the housing 150. In certain implementations, the at least one lamina of the first mount 130 has a first length, a first width, and a first thickness and the at least one lamina of the second mount has a second length, a second width, and a second thickness. For example, as shown in FIGs. 1A-1D, the second length can be substantially equal to the first length, the second width can be substantially equal to the first width, and the second thickness can be substantially equal to the first thickness. For another example, the second length can be different from the first length, the second width can be different from the first width, and / or the second thickness can be different from the first thickness.

[0041] FIGs. 2A-2D schematically illustrate various example first and second mounts 130,140 in accordance with certain implementations described herein. In certain implementations, as shown in FIG. 2A, the at least one lamina of the first mount 130 and / or the second mount 140 has a substantially rectilinear (e.g., rectangular; square) shape (see, also, FIGs. 1A-1D). In certain other implementations, the at least one lamina of the first mount 130 and / or the second mount 140 has a substantially curved (e.g., circular; oval) shape (e.g., FIG. 2B), a substantially trapezoidal shape (e.g., FIG. 2C), or other shapes (e.g., triangular; polygonal; irregular). In certain implementations, the first mount 130 and / or the second mount 140 is symmetric about the longitudinal axis 111 (see, e.g., FIGs. 2A-2D), while in certain other implementations, the first mount 130 and / or the second mount 140 is asymmetric relative to the longitudinal axis 111.

[0042] As shown in FIG. 2D, the first mount 130 and / or the second mount 140 comprises a plurality of portions (e.g., the first mount 130 comprising first portions 130a, b; the second mount 140 comprising second portions 140a, b). At least some of the first portions 130a, b and / or at least some of the second portions 140a, b can extend in both directions substantially parallel to the longitudinal axis 111 (e.g., one or more first portions 130a,b extending towards the second mount 140; one or more second portions 140a,b extending towards the first mount 130). The first portions 130a,b and the second portions140a, b are spaced from one another (e.g., are not coupled to one another). Certain such implementations can increase the extent of the first mount 130 and / or the second mount 140 along the longitudinal axis 111 (e.g., the direction of the time-varying changes 124 of the length of the piezoelectric element 110), as compared to certain implementations in which the first mount 130 and / or the second mount 140 only extend outwardly from respective ends of the housing 150. Other shapes and configurations of the first and second mounts 130,140 are also compatible with certain implementations described herein. In certain implementations, the first mount 130 and the second mount 140 have substantially the same shape, configuration, and / or dimensions as one another (see, e.g., FIGs. 2A-2D), while in certain other implementations, the first mount 130 and the second mount 140 have different shapes, configurations, and / or dimensions from one another.

[0043] In certain implementations in which the first and / or second outer bone surface regions 52a, b are not substantially flat (e.g., curved), the first mount 130 is configured to be curved (e.g., bent) to substantially follow a first contour of the first outer bone surface region 52a and / or the second mount 140 is configured to be curved (e.g., bent) to substantially follow a second contour of the second outer bone surface region 52b. For example, the at least one lamina of the first mount 130 and / or the second mount 140 is sufficiently malleable (e.g., compliant; flexible; bendable; twistable) to be shaped by the clinician (e.g., surgeon) during the implantation process to substantially conform to the contour of the underlaying portion of the outer bone surface 52. For example, at least a portion of the at least one lamina can be bent by the clinician in an upward or downward direction relative to the housing 150 (e.g., in a direction substantially perpendicular to the longitudinal axis 111) and / or twisted about a direction substantially parallel to the longitudinal axis 111 to conform to anatomical variations of the underlying bone while maintaining sufficient axial stiffness to facilitate transmission of the vibrational signals 160 from the piezoelectric element 110 to the at least one bone 50.

[0044] In certain implementations, the bone 50 upon which the apparatus 100 is to be implanted on or within comprises cortical bone material 51 (e.g., having a thickness in a range of 1 millimeter to 5 millimeters; in a range of 2 millimeters to 4 millimeters) and underlying diploe material 53, the cortical bone material 51 comprising the outer bone surface 52. The cortical bone material 51 is denser and harder than the diploe material 53,and cortical bone material 51 is more conducive to propagating the vibrational signals 160 emanating from the piezoelectric element 110 than is the diploe material 53. In certain implementations, the first and second mounts 130,140 are configured to be rigidly affixed to the first and second outer bone surface regions 52a, b, respectively, (which comprise the cortical bone material 51) across a surface area (e.g., fixation area) that is in the range of 6 mm2to 400 mm2(e.g., in a range of 25 mm2to 100 mm2).

[0045] FIGs. 3A-3D schematically illustrate cross-sectional side views of example apparatus 100 rigidly affixed to an outer bone surface 52 in accordance with certain implementations described herein. As shown in FIGs. 3A and 3B, the housing 150 is at least partially within a cavity 54 extending from the outer bone surface 52 into the underlying diploe material 53 and the first and second mounts 130,140 are rigidly affixed to the first and second outer bone surface regions 52a, b, respectively. In FIG. 3A, substantially the whole housing 150 is within the cavity 54, and in FIG. 3B, approximately one -half of the housing 150 is within the cavity 54 with the remaining portion of the housing 150 extending above the outer bone surface 52. For example, the cavity 54 can be machined (e.g., drilled; milled) into the bone 50 with a depth sufficient to allow the housing 150 to extend below the outer bone surface 52 by a predetermined amount (e.g., extending through the cortical bone material 51 into the diploe material 53.

[0046] As shown in FIG. 3C, the housing 150 is on or above the outer bone surface 52 and the first and second mounts 130,140 are rigidly affixed to the first and second outer bone surface regions 52a, b, respectively. As shown in FIG. 3D, the housing 150 is at least partially within the cavity 54 and the first and second mounts 130,140 are rigidly affixed to the first and second outer bone surface regions 52a,b, respectively. At least one of the first and second outer bone surface regions 52a, b can comprise a machined (e.g., milled) portion of the cortical bone material 51 (e.g., by a depth substantially equal to the thickness of the first and / or second mount 130,140; by a depth in a range of 0.5 millimeter to 1 millimeter). For example, a portion of the cortical bone material 51 can be machined to planarize the at least one of the first and second outer bone surface regions 52a, b prior to affixing the first and second mounts 130,140 to the bone 50 and / or to induce bone regrowth for osseointegration with the first and / or second mount 130,140. While FIG. 3D shows the machined portion of the cortical bone material 51 in conjunction with substantially the wholehousing 150 within the cavity 54 (see, e.g., FIG. 3A), the machined portion of the cortical bone material 51 can be used with other configurations of the housing 150, with or without a cavity 54 (see, e.g., FIGs. 3A-3C).

[0047] In certain implementations, the first mount 130 and / or the second mount 140 is further configured to be rigidly affixed to a machined bone surface 55 substantially perpendicular to the first outer bone surface 52a and / or the second outer bone surface 52b. For example, the machine bone surface 55 can be an inner surface of the cavity 54 and formed during the machining which forms the cavity 54. In this way, the first mount 130 and / or the second mount 140 can be rigidly affixed to both the cortical bone material 51 and the diploe material 53. While the diploe material 53 is softer and less dense than the cortical bone material 51, in certain implementations, affixing the first mount 130 and / or the second mount 140 to the diploe material 53 as well as to the cortical bone material 51 can further facilitate transmission of the vibrational signals 160 from the piezoelectric element 110 to the at least one bone 50.

[0048] FIGs. 4A-4D schematically illustrate cross-sectional side views of portions of example apparatus 100 rigidly affixed to the bone 50 in accordance with certain implementations described herein. In certain implementations, the first mount 130 and / or the second mount 140 is configured to be rigidly affixed to the outer bone surface 52 (e.g., and to the machined bone surface 55) by osseointegration. As shown in FIG. 4A, the first mount 130 and / or the second mount 140 can comprise a surface (e.g., coating) comprising an osseointegrating material 170 (e.g., titanium) configured to contact the bone 50 (e.g., the outer bone surface 52) and to be rigidly affixed to the bone 50 via osseointegration. As shown in FIG. 4B, the first mount 130 and / or the second mount 140 can be configured to be rigidly affixed to the outer bone surface 52 by cement 172 (e.g., epoxy; glue; adhesive), examples of which include but are not limited to: OtoMimix bone cement available from Olympus Corp, of Hachioji, Tokyo Japan. As shown in FIG. 4C, the first mount 130 and / or the second mount 140 can comprise a surface with one or more protrusions 174 (e.g., ridges; bumps; teeth) or recesses (e.g., grooves) configured to be rigidly affixed to the outer bone surface 52. As shown in FIG. 4D, the first mount 130 and / or the second mount 140 can comprise at least one fastener 176 (e.g., screw; rivet; nail; pin; bone fixture; clamp; coupler) configured to extend through a portion of the first and / or second mount 130,140 and to berigidly affixed to the underlying bone 50. In certain implementations, the first mount 130 and / or the second mount 140 comprises a combination of two or more of the osseointegrating material 170, cement 172, one or more protrusions 174, and at least one fastener 176. In certain implementations, the first mount 130 and the second mount 140 are configured to be rigidly affixed to the first and second outer bone surface regions 52a, b, respectively, by the same type of mechanism (e.g., osseointegrating material 170, cement 172, one or more protrusions 174, or at least one fastener 176) as one another, while in certain other implementations, the first and second mounts 130,140 are rigidly affixed to the first and second outer bone surface regions 52a, b by different types of mechanisms from one another.

[0049] FIGs. 5A-5C are flow diagrams of examples of a method 200 for implanting an apparatus 100 in accordance with certain implementations described herein. While the method 200 is described by referring to some of the structures of the example apparatus 100 of FIGs. 1A-1D, 2A-2D, 3A-3D, and 4A-4D, other apparatus and systems with other configurations of components can also be used to perform the method 200 in accordance with certain implementations described herein.

[0050] In an operational block 210, the method 200 comprises providing an actuator (e.g., apparatus 100) comprising a plurality of piezoelectric layers 112 and a plurality of electrodes 118 alternating with the piezoelectric layers 112. The actuator further comprises two end anchors (e.g., first and second mounts 130,140) spaced from one another along a direction substantially perpendicular to the piezoelectric layers 112 (e.g., longitudinal axis 111). For example, at least one of the two end anchors comprises at least one plate and said providing the actuator comprises manipulating the at least one plate to be substantially parallel to the corresponding portion of the outer bone surface. The actuator can be configured to undergo time-varying expansions and contractions between the two end anchors to generate vibrational signals that propagate through the bone.

[0051] In an operational block 220, the method 200 further comprises mounting the two end anchors to be in mechanical communication with corresponding portions of an outer bone surface 52 of a recipient’s body with the direction substantially parallel to the portions of the outer bone surface 52. For example, the two end anchors are configured to hold the actuator (e.g., mass free actuator) such that the longitudinal axis 111 is substantiallyparallel to the first outer bone surface region 52a (e.g., cortical bone surface region) and / or the second outer bone surface region 52b (e.g., cortical bone surface region).

[0052] In certain implementations (see, e.g., FIG. 5B and 5C), the method 200 further comprises, in an operational block 230, prior to said mounting in the operational block 220, machining the bone 50. For example, the bone 50 can be machined to substantially planarize the portions of the outer bone surface 52. For another example (see, e.g., FIG. 5C), the bone 50 can be machined to form a recess (e.g., cavity 54) into the bone 50. In certain such implementations, said mounting in the operational block 220 can comprise, in an operational block 222, positioning the actuator such that each of the two end anchors has a first portion extending over the outer bone surface 52 and a second portion extending into the recess below the outer bone surface 52 and, in an operational block 224, affixing the two end anchors to the corresponding portions of the outer bone surface 52. The corresponding portions of the outer bone surface 52 can be adjacent to the recess. For example, the second portions of the two end anchors can be in mechanical communication with corresponding side surfaces of the recess.

[0053] Although commonly used terms are used to describe the systems and methods of certain implementations for ease of understanding, these terms are used herein to have their broadest reasonable interpretations. Although various aspects of the disclosure are described with regard to illustrative examples and implementations, the disclosed examples and implementations should not be construed as limiting. Conditional language, such as, among others, "can," "could," "might," or "may," unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain implementations include, while other implementations do not include, certain features, elements and / or steps. Thus, such conditional language is not generally intended to imply that features, elements and / or steps are in any way required for one or more implementations or that one or more implementations necessarily include logic for deciding, with or without user input or prompting, whether these features, elements and / or steps are included or are to be performed in any particular implementation. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a nonexclusive manner, indicating that the referenced elements, components, or steps may bepresent, or utilized, or combined with other elements, components, or steps that are not expressly referenced.

[0054] It is to be appreciated that the implementations disclosed herein are not mutually exclusive and may be combined with one another in various arrangements. In addition, although the disclosed methods and apparatuses have largely been described in the context of medical devices, various implementations described herein can be incorporated in a variety of other suitable devices, methods, and contexts.

[0055] Language of degree, as used herein, such as the terms “approximately,” “about,” “generally,” and “substantially,” represent a value, amount, or characteristic close to the stated value, amount, or characteristic that still performs a desired function or achieves a desired result. For example, the terms “approximately,” “about,” “generally,” and “substantially” may refer to an amount that is within ± 10% of, within ± 5% of, within ± 2% of, within ± 1 % of, or within ± 0.1% of the stated amount. As another example, the terms “generally parallel” and “substantially parallel” refer to a value, amount, or characteristic that departs from exactly parallel by ± 10 degrees, by ± 5 degrees, by ± 2 degrees, by ± 1 degree, or by ± 0.1 degree, and the terms “generally perpendicular” and “substantially perpendicular” refer to a value, amount, or characteristic that departs from exactly perpendicular by ± 10 degrees, by ± 5 degrees, by ± 2 degrees, by ± 1 degree, or by ± 0.1 degree. The ranges disclosed herein also encompass any and all overlap, sub-ranges, and combinations thereof. Language such as “up to,” “at least,” “greater than,” less than,” “between,” and the like includes the number recited. As used herein, the meaning of “a,” “an,” and “said” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “into” and “on,” unless the context clearly dictates otherwise.

[0056] While the methods and systems are discussed herein in terms of elements labeled by ordinal adjectives (e.g., first, second, etc.), the ordinal adjective are used merely as labels to distinguish one element from another (e.g., one signal from another or one circuit from one another), and the ordinal adjective is not used to denote an order of these elements or of their use.

[0057] The invention described and claimed herein is not to be limited in scope by the specific example implementations herein disclosed, since these implementations areintended as illustrations, and not limitations, of several aspects of the invention. Any equivalent implementations are intended to be within the scope of this invention. Indeed, various modifications of the invention in form and detail, in addition to those shown and described herein, will become apparent to those skilled in the art from the foregoing description. Such modifications are also intended to fall within the scope of the claims. The breadth and scope of the invention should not be limited by any of the example implementations disclosed herein, but should be defined only in accordance with the claims and their equivalents.

Claims

WHAT IS CLAIMED IS:

1. An apparatus comprising:a piezoelectric element comprising a plurality of piezoelectric layers, the piezoelectric element having a first portion and a second portion spaced from the first portion along a longitudinal axis of the piezoelectric element that is substantially perpendicular to the piezoelectric layers;circuitry in electrical communication with the piezoelectric element, the circuitry configured to apply non-zero voltage differences between the first portion and the second portion, the non-zero voltage differences inducing time-varying changes of an attribute of the piezoelectric element; anda first mount in mechanical communication with the first portion and a second mount in mechanical communication with the second portion, the second mount spaced from the first mount, the first mount configured to be rigidly affixed to a first outer bone surface region and the second mount configured to be rigidly affixed to a second outer bone surface region.

2. The apparatus of claim 1, further comprising a housing containing the piezoelectric element and configured to be implanted on or within at least one bone of a recipient’s body with the first mount and the second mount rigidly affixed to the first and second outer bone surface regions, respectively, such that the time-varying changes of the attribute generate vibrational signals that propagate through the at least one bone.

3. The apparatus of claim 2, wherein the vibrational signals evoke a hearing percept by the recipient.

4. The apparatus of any of claims 1 to 3, wherein the first portion comprises a first end of the piezoelectric element, the second portion comprises a second end of the piezoelectric element spaced from the first end along a longitudinal axis of the piezoelectric element, and the attribute comprises a length of the piezoelectric element along the longitudinal axis.

5. The apparatus of claim 4, wherein the piezoelectric element is configured to be implanted such that the longitudinal axis of the piezoelectric element is substantially parallel to the first outer bone surface region and / or the second outer bone surface region.

6. The apparatus of claim 4 or claim 5, wherein each of first mount and the second mount comprises at least one lamina configured to extend across the first outer bone surface region and the second outer bone surface region, respectively.

7. The apparatus of claim 6, wherein the at least one lamina is configured to extend in at least one direction having a component substantially parallel to the longitudinal axis.

8. The apparatus of claim 6 or claim 7, wherein the at least one lamina has a substantially oval or rectilinear shape.

9. The apparatus of any preceding claim, wherein the first mount is configured to be curved to substantially follow a first contour of the first outer bone surface region and / or the second mount is configured to be curved to follow a second contour of the second outer bone surface region.

10. The apparatus of any preceding claim, wherein the first mount comprises a first surface with one or more first protrusions configured to be affixed to the first outer bone surface region and / or the second mount comprises a second surface with one or more second protrusions configured to be affixed to the second outer bone surface region.

11. The apparatus of any preceding claim, wherein the first mount and / or the second mount is configured to be rigidly affixed by osseointegration.

12. The apparatus of any preceding claim, wherein the first mount and / or the second mount is configured to be rigidly affixed to the outer bone surface by cement.

13. The apparatus of any preceding claim, wherein the first mount and / or the second mount is configured to be rigidly affixed by at least one fastener.

14. The apparatus of any preceding claim, wherein the first mount and / or the second mount is further configured to be rigidly affixed to a machined bone surface substantially perpendicular to the first outer bone surface region and / or the second outer bone surface region.

15. The apparatus of any preceding claim, wherein the piezoelectric element comprises a bone conduction mass free actuator.

16. The apparatus of claim 1, wherein the attribute comprises a curvature of the piezoelectric element.

17. A method comprising:providing an actuator comprising a plurality of piezoelectric layers and two end anchors spaced from one another along a direction substantially perpendicular to the piezoelectric layers; andmounting the two end anchors to be in mechanical communication with corresponding portions of an outer bone surface of a recipient’s body with the direction substantially parallel to the portions of the outer bone surface.

18. The method of claim 17, wherein at least one of the two end anchors comprises at least one plate and said providing the actuator comprises manipulating the at least one plate to be substantially parallel to the corresponding portion of the outer bone surface.

19. The method of claim 17 or claim 18, further comprising, prior to said mounting, machining the bone to substantially planarize the portions of the outer bone surface.

20. The method of any of claims 17 to 19, further comprising, prior to said mounting, machining the bone to form a recess into the bone, and said mounting comprises:positioning the actuator such that each of the two end anchors has a first portion extending over the outer bone surface and a second portion extending into the recess below the outer bone surface; andaffixing the two end anchors to the corresponding portions of the outer bone surface.

21. The method of claim 20, wherein the corresponding portions of the outer bone surface are adjacent to the recess.

22. The method of claim 20 or claim 21, wherein the second portions of the two end anchors are in mechanical communication with corresponding side surfaces of the recess.

23. The method of any of claims 17 to 22, wherein the actuator is configured to undergo time-varying expansions and contractions between the two end anchors to generate vibrational signals that propagate through the bone.

24. An apparatus comprising:a mass free actuator comprising a piezoelectric element configured to expand and contract along a longitudinal axis in response to applied voltages; anda first anchor in mechanical communication with a first end portion of the mass free actuator and a second anchor in mechanical communication with a second end portion of the mass free actuator opposite to the first end portion, the first anchor configured to be rigidly affixed to a first cortical bone surface region having a surface area in a range of 6 mm2to 400 mm2and the second anchor configured to be rigidly affixed to a second cortical bone surface region having a surface area in a range of 6 mm2to 400 mm2.

25. The apparatus of claim 24, wherein the surface area of the first cortical bone surface region and / or the second cortical bone surface region is in a range of 25 mm2to 100 mm2.

26. The apparatus of claim 24 or claim 25, wherein the first and second anchors are configured to hold the mass free actuator such that the longitudinal axis is substantially parallel to the first cortical bone surface region and / or the second cortical bone surface region.

27. An apparatus comprising:a piezoelectric actuator configured to vibrate along an axis in response to applied voltages; anda housing containing the piezoelectric actuator and configured to be implanted on or within at least one bone of a recipient’s body such that vibrational signals generated by the piezoelectric actuator propagate through the at least one bone, the housing comprising:a first end portion configured to be implanted to be in mechanical communication with a first cortical bone surface region of the at least one bone such that the axis is substantially parallel to the first cortical bone surface region; anda second end portion configured to be implanted to be in mechanical communication with a second cortical bone surface region such that the axis issubstantially parallel to the second cortical bone surface region, the second cortical bone surface region spaced from the first cortical bone surface region.

28. The apparatus of claim 27, wherein the first end portion comprises at least one malleable first plate configured to conform to a first contour of the first cortical bone surface region and the second end portion comprises at least one malleable second plate configured to conform to a second contour of the second cortical bone surface region.

29. The apparatus of any of claims 1 to 16 and claims 24 to 28, wherein the apparatus comprises a component of a sleep disorder device, a seizure device, a balance or movement disorder device, a tinnitus management device, or a sensory prosthesis device.

30. The method of any of claims 17 to 23, further comprising using the actuator as a component of a sleep disorder system, a seizure system, a balance or movement disorder system, a tinnitus management system, or sensory prosthesis system.

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