WO2025099520A1

WO2025099520A1 - Power transmitter with safety system

Info

Publication number: WO2025099520A1
Application number: PCT/IB2024/060289
Authority: WO
Inventors: Werner Meskens; Koen Erik VAN DEN HEUVEL; Samuelle BOECKX
Original assignee: Cochlear Ltd
Current assignee: Cochlear Ltd
Priority date: 2023-11-09
Filing date: 2024-10-18
Publication date: 2025-05-15
Anticipated expiration: 2026-05-09

Abstract

An apparatus includes a first magnetic induction (MI) antenna configured to wirelessly transmit power to a second MI antenna of a device within or on a recipient's body portion. The apparatus further includes a sensor configured to generate a sensor signal. The apparatus further includes control circuitry in electrical communication with the first MI antenna and the sensor. The control circuitry is configured to, in response to the sensor signal, determine at least one of: a presence, location, and/or an attribute of a cushion between the body portion and the first MI antenna, a clearance between the first MI antenna and the body portion, and an extent of tissue of the recipient within a power transmission range of the first MI antenna. The control circuitry is further configured to adjust, in response to the sensor signal, a power level transmitted by the first MI antenna.

Description

POWER TRANSMITTER WITH SAFETY SYSTEM

BACKGROUND

Field

[0001] The present application relates generally to systems and methods for wirelessly transmitting power to a device on or implanted within a recipient’s body from an external device outside the recipient’s body.

Description of the Related Art

[0002] Medical devices have provided a wide range of therapeutic benefits to recipients over recent decades. Medical devices can include internal or implantable components/de vices, external or wearable components/devices, or combinations thereof (e.g., a device having an external component communicating with an implantable component). Medical devices, such as traditional hearing aids, partially or fully-implantable hearing prostheses (e.g., bone conduction devices, mechanical stimulators, cochlear implants, etc.), pacemakers, defibrillators, functional electrical stimulation devices, and other medical devices, have been successful in performing lifesaving and/or lifestyle enhancement functions and/or recipient monitoring for a number of years.

[0003] The types of medical devices and the ranges of functions performed thereby have increased over the years. For example, many medical devices, sometimes referred to as “implantable medical devices,” now often include one or more instruments, apparatus, sensors, processors, controllers or other functional mechanical or electrical components that are permanently or temporarily implanted in a recipient. These functional devices are typically used to diagnose, prevent, monitor, treat, or manage a disease/injury or symptom thereof, or to investigate, replace or modify the anatomy or a physiological process. Many of these functional devices utilize power and/or data received from external devices that are part of, or operate in conjunction with, implantable components.

SUMMARY

[0004] In one aspect disclosed herein, an apparatus comprises at least one first magnetic induction (MI) antenna configured to wirelessly transmit power to at least one second MI antenna of a device within or on a body portion of a recipient. The apparatus further comprises at least one sensor configured to generate at least one sensor signal. The apparatus further comprises control circuitry in electrical communication with the at least one first MI antenna and the at least one sensor. The control circuitry is configured to, in response to the at least one sensor signal, determine at least one of: a presence, location, and/or at least one attribute of a cushion between the body portion and the at least one first MI antenna, a clearance between the at least one first MI antenna and the body portion, and an extent of tissue of the recipient within a power transmission range of the at least one first MI antenna. The control circuitry is further configured to adjust, in response to the at least one sensor signal, a power level transmitted by the at least one first MI antenna.

[0005] In another aspect disclosed herein, a method comprises wirelessly transmitting power from a power source to a device on or implanted within a recipient’s body. The device is inductively coupled to the power source. The method further comprises, while wirelessly transmitting the power from the power source to the device, generating information relevant to exposure of the recipient’s body to electric, magnetic, and/or electromagnetic fields generated by the power source. The method further comprises, in response to the information, adjusting the power transmitted from the power source to the device such that the electric, magnetic, and/or electromagnetic fields comply with a predetermined medical safety regulatory standard for exposure of the recipient’s body.

[0006] In another aspect disclosed herein, an apparatus comprises at least one first antenna coil configured to receive at least one electrical current. The at least one electrical current is configured to flow through the at least one first antenna coil to transcutaneously transmit power to at least one second antenna coil of a device within or on a tissue portion of a recipient’s body. The apparatus further comprises at least one sensor configured to generate at least one first signal indicative of a presence, type, and/or thickness of a cushion between the tissue portion of the recipient’s body and the at least one first antenna coil. The apparatus further comprises circuitry configured to adjust, in response to the at least one first signal, the at least one electrical current.

[0007] In another aspect disclosed herein, an apparatus comprises a housing having a first surface and a second surface opposite to the first surface. The housing is configured to be placed in either a first orientation or a second orientation. In the first orientation, the first surface is on an underlying support surface and the second surface is in contact with a recipient or with a cushion beneath the recipient. In the second orientation, the second surface is on the underlying support surface and the first surface is in contact with the recipient or with the cushion beneath the recipient. The apparatus further comprises at least one power transmission coil within the housing. The at least one power transmission coil is positioned closer to the second surface than to the first surface and is configured to transmit power to a device on or within the recipient. The apparatus further comprises a sensor on or within the housing. The sensor is configured to generate a sensor signal indicative of whether the housing is in the first orientation or the second orientation. The apparatus further comprises circuitry within the housing and in electrical communication with the at least one power transmission coil. The circuitry is configured to adjust, in response to the sensor signal, at least one electrical current flowing through the at least one power transmission coil.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Implementations are described herein in conjunction with the accompanying drawings, in which:

[0009] FIG. 1A is a perspective view of an example cochlear implant auditory prosthesis implanted in a recipient in accordance with certain implementations described herein;

[0010] FIG. IB is a perspective view of an example fully implantable middle ear implant auditory prosthesis implanted in a recipient in accordance with certain implementations described herein;

[0011] FIG. 2 schematically illustrates an example apparatus in accordance with certain implementations described herein;

[0012] FIGs. 3A-3G schematically illustrate various views and configurations of an example apparatus, an example device within or on a portion of a recipient’s body, and an example cushion between the apparatus and the portion of the recipient’s body in accordance with certain implementations described herein;

[0013] FIGs. 4A-4F schematically illustrate various example first MI antennas in accordance with certain implementations described herein; and

[0014] FIG. 5 is a flow diagram of an example method 500 for operating an apparatus in accordance with certain implementations described herein. DETAILED DESCRIPTION

[0015] Certain implementations described herein provide a wireless power transmitter for charging a device implanted or worn on a recipient’s body. The transmitter includes a sensor system configured to detect one or more environmental aspects of the transmitter and the device to be charged which can vary unpredictably during a charging session or among different charging sessions. Example aspects include: a presence, location, and/or at least one attribute of a cushion (e.g., cushion material type; cushion material) between the device and the transmitter; a clearance between a magnetic induction (MI) antenna of the device and the body portion; an extent of the recipient’s body tissue within a power transmission range of the transmitter. The power transfer rate between the device and the transmitter and/or the exposure of the recipient’s tissue to electric, magnetic, and/or electromagnetic fields can depend on the detected aspects, and the transmitter can use the detected aspects to adjust a transmission power level (e.g., by adjusting the current flowing through the MI antenna) to optimize the charging current while complying with regulatory exposure safety limits.

[0016] The teachings detailed herein are applicable, in at least some implementations, to any type of implantable or non-implantable stimulation or measurement system (e.g., implantable or non-implantable auditory prosthesis device or system). 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 auditory prosthesis devices, certain other implementations are compatible in the context of other types of devices or systems.

[0017] Merely for ease of description, apparatus and methods disclosed herein are primarily described with reference to an illustrative medical device, namely an implantable transducer assembly 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.

[0018] While certain implementations are described herein in the context of auditory prosthesis devices, certain other implementations are compatible in the context of other types of sensory prosthesis systems that are configured to evoke 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), tinnitus treatment devices, visual devices (e.g., bionic eyes), visual prostheses (e.g., retinal implants), somatosensory implants, and chemosensory implants. 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 monitoring systems; pain control systems; bladder control systems; 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.

[0019] FIG. 1A is a perspective view of an example cochlear implant auditory prosthesis 100 implanted in a recipient in accordance with certain implementations described herein. The example auditory prosthesis 100 is shown in FIG. 1A as comprising an implanted stimulator unit 120 and a microphone assembly 124 that is external to the recipient (e.g., a partially implantable cochlear implant). An example auditory prosthesis 100 (e.g., a totally implantable cochlear implant; a mostly implantable cochlear implant) in accordance with certain implementations described herein can replace the external microphone assembly 124 shown in FIG. 1 A with a subcutaneously implantable microphone assembly, as described more fully herein. In certain implementations, the example cochlear implant auditory prosthesis 100 of FIG. 1 A can be in conjunction with a reservoir of liquid medicament as described herein. [0020] As shown in FIG. 1A, the recipient has an outer ear 101, a middle ear 105, and an inner ear 107. In a fully functional ear, the outer ear 101 comprises an auricle 110 and an ear canal 102. An acoustic pressure or sound wave 103 is collected by the auricle 110 and is channeled into and through the ear canal 102. Disposed across the distal end of the ear canal 102 is a tympanic membrane 104 which vibrates in response to the sound wave 103. This vibration is coupled to oval window or fenestra ovalis 112 through three bones of middle ear 105, collectively referred to as the ossicles 106 and comprising the malleus 108, the incus 109, and the stapes 111. The bones 108, 109, and 111 of the middle ear 105 serve to filter and amplify the sound wave 103, causing the oval window 112 to articulate, or vibrate in response to vibration of the tympanic membrane 104. This vibration sets up waves of fluid motion of the perilymph within cochlea 140. Such fluid motion, in turn, activates tiny hair cells (not shown) inside the cochlea 140. Activation of the hair cells causes appropriate nerve impulses to be generated and transferred through the spiral ganglion cells (not shown) and auditory nerve 114 to the brain (also not shown) where they are perceived as sound.

[0021] As shown in FIG. 1A, the example auditory prosthesis 100 comprises one or more components which are temporarily or permanently implanted in the recipient. The example auditory prosthesis 100 is shown in FIG. 1A with an external component 142 which is directly or indirectly attached to the recipient’s body, and an internal component 144 which is temporarily or permanently implanted in the recipient (e.g., positioned in a recess of the temporal bone adjacent auricle 110 of the recipient). The external component 142 typically comprises one or more sound input elements (e.g., an external microphone 124) for detecting sound, a sound processing unit 126 (e.g., disposed in a Behind-The-Ear unit), a power source (not shown), and an external transmitter unit 128. In the illustrative implementations of FIG. 1A, the external transmitter unit 128 comprises an external coil 130 (e.g., a wire antenna coil comprising multiple turns of electrically insulated single-strand or multi-strand platinum or gold wire) and, preferably, a magnet (not shown) secured directly or indirectly to the external coil 130. The external coil 130 of the external transmitter unit 128 is part of an inductive radio frequency (RF) communication link with the internal component 144. The sound processing unit 126 processes the output of the microphone 124 that is positioned externally to the recipient’s body, in the depicted implementation, by the recipient’s auricle 110. The sound processing unit 126 processes the output of the microphone 124 and generates encoded signals, sometimes referred to herein as encoded data signals, which are provided to the external transmitter unit 128 (e.g., via a cable). As will be appreciated, the sound processing unit 126 can utilize digital processing techniques to provide frequency shaping, amplification, compression, and other signal conditioning, including conditioning based on recipient-specific fitting parameters.

[0022] The power source of the external component 142 is configured to provide power to the auditory prosthesis 100, where the auditory prosthesis 100 includes a battery (e.g., located in the internal component 144, or disposed in a separate implanted location) that is recharged by the power provided from the external component 142 (e.g., via a transcutaneous energy transfer link). The transcutaneous energy transfer link is used to transfer power and/or data to the internal component 144 of the auditory prosthesis 100. Various types of energy transfer, such as infrared (IR), electromagnetic, capacitive, and inductive transfer, may be used to transfer the power and/or data from the external component 142 to the internal component 144. During operation of the auditory prosthesis 100, the power stored by the rechargeable battery is distributed to the various other implanted components as needed.

[0023] The internal component 144 comprises an internal receiver unit 132, a stimulator unit 120, and an elongate electrode assembly 118. In some implementations, the internal receiver unit 132 and the stimulator unit 120 are hermetically sealed within a biocompatible housing. The internal receiver unit 132 comprises an internal coil 136 (e.g., a wire antenna coil comprising multiple turns of electrically insulated single-strand or multistrand platinum or gold wire), and preferably, a magnet (also not shown) fixed relative to the internal coil 136. The internal receiver unit 132 and the stimulator unit 120 are hermetically sealed within a biocompatible housing, sometimes collectively referred to as a stimulator/receiver unit. The internal coil 136 receives power and/or data signals from the external coil 130 via a transcutaneous energy transfer link (e.g., an inductive RF link). The stimulator unit 120 generates electrical stimulation signals based on the data signals, and the stimulation signals are delivered to the recipient via the elongate electrode assembly 118.

[0024] The elongate electrode assembly 118 has a proximal end connected to the stimulator unit 120, and a distal end implanted in the cochlea 140. The electrode assembly 118 extends from the stimulator unit 120 to the cochlea 140 through the mastoid bone 119. In some implementations, the electrode assembly 118 may be implanted at least in the basal region 116, and sometimes further. For example, the electrode assembly 118 may extend towards apical end of cochlea 140, referred to as cochlea apex 134. In certain circumstances, the electrode assembly 118 may be inserted into the cochlea 140 via a cochleostomy 122. In other circumstances, a cochleostomy may be formed through the round window 121, the oval window 112, the promontory 123, or through an apical turn 147 of the cochlea 140.

[0025] The elongate electrode assembly 118 comprises a longitudinally aligned and distally extending array 146 of electrodes or contacts 148, sometimes referred to as electrode or contact array 146 herein, disposed along a length thereof. Although the electrode array 146 can be disposed on the electrode assembly 118, in most practical applications, the electrode array 146 is integrated into the electrode assembly 118 (e.g., the electrode array 146 is disposed in the electrode assembly 118). As noted, the stimulator unit 120 generates stimulation signals which are applied by the electrodes 148 to the cochlea 140, thereby stimulating the auditory nerve 114.

[0026] While FIG. 1 A schematically illustrates an auditory prosthesis 100 utilizing an external component 142 comprising an external microphone 124, an external sound processing unit 126, and an external power source, in certain other implementations, one or more of the microphone 124, sound processing unit 126, and power source are implantable on or within the recipient (e.g., within the internal component 144). For example, the auditory prosthesis 100 can have each of the microphone 124, sound processing unit 126, and power source implantable on or within the recipient (e.g., encapsulated within a biocompatible assembly located subcutaneously), and can be referred to as a totally implantable cochlear implant (“TICI”). For another example, the auditory prosthesis 100 can have most components of the cochlear implant (e.g., excluding the microphone, which can be an in-the-ear-canal microphone) implantable on or within the recipient, and can be referred to as a mostly implantable cochlear implant (“MICI”).

[0027] FIG. IB schematically illustrates a perspective view of an example fully implantable auditory prosthesis 200 (e.g., fully implantable middle ear implant or totally implantable acoustic system), implanted in a recipient, utilizing an acoustic actuator in accordance with certain implementations described herein. The example auditory prosthesis 200 of FIG. IB comprises a biocompatible implantable assembly 202 (e.g., comprising an implantable capsule) located subcutaneously (e.g., beneath the recipient’s skin and on a recipient's skull). While FIG. IB schematically illustrates an example implantable assembly 202 comprising a microphone, in other example auditory prostheses 200, a pendant microphone can be used (e.g., connected to the implantable assembly 202 by a cable). The implantable assembly 202 includes a signal receiver 204 (e.g., comprising a coil element) and an acoustic transducer (e.g., a microphone assembly 206 comprising a diaphragm and an electret or piezoelectric transducer) that is positioned to receive acoustic signals through the recipient’s overlying tissue. The implantable assembly 202 may further be utilized to house a number of components of the fully implantable auditory prosthesis 200. For example, the implantable assembly 202 can include an energy storage device and a signal processor (e.g., a sound processing unit). Various additional processing logic and/or circuitry components can also be included in the implantable assembly 202 as a matter of design choice.

[0028] For the example auditory prosthesis 200 shown in FIG. IB, the signal processor of the implantable assembly 202 is in operative communication (e.g., electrically interconnected via a wire 208) with an actuator 210 (e.g., comprising a transducer configured to generate mechanical vibrations in response to electrical signals from the signal processor). In certain implementations, the example auditory prosthesis 100, 200 shown in FIGs. 1A and IB can comprise an implantable microphone assembly, such as the microphone assembly 206 shown in FIG. IB. For such an example auditory prosthesis 100, the signal processor of the implantable assembly 202 can be in operative communication (e.g., electrically interconnected via a wire) with the microphone assembly 206 and the stimulator unit of the main implantable component 120. In certain implementations, at least one of the microphone assembly 206 and the signal processor (e.g., a sound processing unit) is implanted on or within the recipient.

[0029] The actuator 210 of the example auditory prosthesis 200 shown in FIG. IB is supportably connected to a positioning system 212, which in turn, is connected to a bone anchor 214 mounted within the recipient's mastoid process (e.g., via a hole drilled through the skull). The actuator 210 includes a connection apparatus 216 for connecting the actuator 210 to the ossicles 106 of the recipient. In a connected state, the connection apparatus 216 provides a communication path for acoustic stimulation of the ossicles 106 (e.g., through transmission of vibrations from the actuator 210 to the incus 109).

[0030] During normal operation, ambient acoustic signals (e.g., ambient sound) impinge on the recipient’ s tissue and are received transcutaneously at the microphone assembly 206. Upon receipt of the transcutaneous signals, a signal processor within the implantable assembly 202 processes the signals to provide a processed audio drive signal via wire 208 to the actuator 210. As will be appreciated, the signal processor may utilize digital processing techniques to provide frequency shaping, amplification, compression, and other signal conditioning, including conditioning based on recipient-specific fitting parameters. The audio drive signal causes the actuator 210 to transmit vibrations at acoustic frequencies to the connection apparatus 216 to affect the desired sound sensation via mechanical stimulation of the incus 109 of the recipient.

[0031] The subcutaneously implantable microphone assembly 202 is configured to respond to auditory signals (e.g., sound; pressure variations in an audible frequency range) by generating output signals (e.g., electrical signals; optical signals; electromagnetic signals) indicative of the auditory signals received by the microphone assembly 202, and these output signals are used by the auditory prosthesis 100, 200 to generate stimulation signals which are provided to the recipient’s auditory system. To compensate for the decreased acoustic signal strength reaching the microphone assembly 202 by virtue of being implanted, the diaphragm of an implantable microphone assembly 202 can be configured to provide higher sensitivity than are external non-implantable microphone assemblies. For example, the diaphragm of an implantable microphone assembly 202 can be configured to be more robust and/or larger than diaphragms for external non-implantable microphone assemblies.

[0032] The example auditory prostheses 100 shown in FIG. 1 A utilizes an external microphone 124 and the auditory prosthesis 200 shown in FIG. IB utilizes an implantable microphone assembly 206 comprising a subcutaneously implantable acoustic transducer. In certain implementations described herein, the auditory prosthesis 100 utilizes one or more implanted microphone assemblies on or within the recipient. In certain implementations described herein, the auditory prosthesis 200 utilizes one or more microphone assemblies that are positioned external to the recipient and/or that are implanted on or within the recipient, and utilizes one or more acoustic transducers (e.g., actuator 210) that are implanted on or within the recipient. In certain implementations, an external microphone assembly can be used to supplement an implantable microphone assembly of the auditory prosthesis 100, 200. Thus, the teachings detailed herein and/or variations thereof can be utilized with any type of external or implantable microphone arrangement, and the acoustic transducers shown in FIGs. 1A and IB are merely illustrative.

[0033] FIG. 2 schematically illustrates an example apparatus 300 in accordance with certain implementations described herein. FIGs. 3A-3G schematically illustrate various views and configurations of the example apparatus 300, an example device 400 within or on a portion 405 of a recipient’s body, and an example cushion 307 between the apparatus 300 and the portion 405 of the recipient’s body in accordance with certain implementations described herein. In certain implementations, as shown in FIGs. 3A-3G, the apparatus 300 (e.g., pillow charger; mattress charger) is positioned on an underlying support surface (e.g., mattress surface; bedframe surface), while in certain other implementations, the apparatus 300 is embedded within a padded component in contact with the recipient’s body (e.g., headrest charger; chair charger) or is worn and/or held by the recipient.

[0034] In certain implementations, the apparatus 300 comprises at least one first magnetic induction (MI) antenna 310 configured to wirelessly transmit power to at least one second MI antenna 410 of the device 400 within or on the body portion 405 of the recipient. The apparatus 300 further comprises at least one sensor 320 configured to generate at least one sensor signal 322. The apparatus 300 further comprises control circuitry 330 in electrical communication with the at least one first MI antenna 310 and the at least one sensor 320. The control circuitry 330 is configured to determine, in response to the at least one sensor signal 322, at least one of: a presence, location, and/or at least one attribute of the cushion 307 between the body portion 405 and the at least one first MI antenna 310, a clearance between the at least one first MI antenna 310 and the body portion 405, and an extent of tissue of the recipient within a power transmission range of the at least one first MI antenna 310. The control circuitry 330 is further configured to, in response to the at least one sensor signal 322, adjust, in response to the at least one sensor signal 322, a power level transmitted by the at least one first MI antenna 310 (e.g., by adjusting the current flowing through the at least one first MI antenna 310).

[0035] In certain implementations, the device 400 receiving power from the apparatus 300 is an implanted portion of a transcutaneous system (e.g., a “partially implantable,” “semi-implantable,” “mostly implantable,” “fully implantable,” or “totally implantable” transcutaneous system) configured to operate using power currently being received by the device 400 and/or previously received and stored by the device 400. For example, the transcutaneous system can be a sensory prosthesis system (e.g., auditory prosthesis system; visual prosthesis system; vestibular prosthesis system), a muscle (e.g., heart) stimulation or monitoring system, a nerve stimulation or monitoring system, or a brain stimulation or monitoring system.

[0036] The device 400 can comprise at least one second MI antenna 410 (e.g., at least one substantially planar antenna coil) and can be configured to operate with a corresponding external portion (not shown) of the transcutaneous system. The external portion can comprise at least one external MI antenna configured to be in wireless communication with the at least one second MI antenna 410 while the external portion is worn on the recipient’s body. For an auditory prosthesis system, the device 400 can be implanted on and substantially parallel to a bone surface within the recipient (e.g., a surface of a portion of the skull behind an auricle 110 or pinna; a surface of the mastoid bone 119) and the external portion can be configured to be worn on the head with the at least one external MI antenna (e.g., on and/or behind the auricle 110) in wireless communication with the at least one second MI antenna 410. The external portion of the transcutaneous system can be configured to be worn on the body portion 405 (e.g., head) during a normal operation mode of the device 400 and configured to be removed from the recipient’s body during a power transfer mode of the device 400 (e.g., during a sleep session of the recipient), during which the apparatus 300 provides power to the device 400.

[0037] During the normal operation mode of the device 400, the at least one second MI antenna 410 (e.g., second communication coil) can be in wireless communication with at least one external MI antenna of the external portion and, during the power transfer mode, the at least one second MI antenna 410 can be in wireless communication with the at least one first MI antenna 310. The device 400 can further comprise circuitry 420 configured to receive data and/or control signals from the external portion of the transcutaneous system during the normal operation mode and configured to receive power signals from the apparatus 300 during the power transfer mode. The circuitry 420 can also be configured to receive/transmit data and/or control signals from/to the apparatus 300 during the power transfer mode. In certain implementations, the device 400 is configured to operate without an external portion during the normal operation mode of the device 400 (e.g., a wholly subcutaneous or fully implantable system) and is configured to be in wireless communication with the at least one first MI antenna 310 during the power transfer mode.

[0038] In certain implementations, the device 400 is an implanted portion of a sleep-disordered breathing (SDB) (e.g., sleep apnea) treatment system for which the normal operation mode is also the power transfer mode. For example, the device 400 can be implanted on or within the recipient’s jaw, neck, or shoulder region (e.g., with stimulation electrodes on, within, or in proximity to the recipient’s tongue or hypoglossal nerve) and the apparatus 300 can be configured to provide data and/or control signals, in addition to the power signals, to the device 400 during a sleep session of the recipient.

[0039] The circuitry 420 of the device 400 can comprise stimulation and/or measurement circuitry comprising one or more active elements (e.g., stimulator unit 120; assembly 202; vibrating actuator) configured to deliver stimuli (e.g., stimulation signals) to a portion of the recipient’s body and/or to detect an attribute or condition of the recipient’s body and can be in electrical communication with the portion of the recipient’s body via electrical conduits (e.g., electrode assembly 118; return electrode) extending from the device 400 to a region of the recipient’s body. In certain implementations, the circuitry 420 is configured to directly use power received by the at least one second MI antenna 410. In certain other implementations, the circuitry 420 comprises power storage circuitry 422 (e.g., battery; capacitor) configured to receive and store power from the at least one second MI antenna 410 during a first time period (e.g., while the device 400 is in proximity to and/or in wireless communication range with the apparatus 300) and to provide stored power to other portions of the circuitry 420 during a second time period (e.g., while the device 400 is spaced and/or out of wireless communication range from the apparatus 300) subsequent to the first time period.

[0040] In certain implementations, the apparatus 300 comprises a housing 305 and the at least one first MI antenna 310, the at least one sensor 320, and the control circuitry 330 are contained (e.g., hermetically sealed) within the housing 305. The housing 305 can comprise an electrically insulative material (e.g., silicone rubber; polymer; polyetheretherketone (PEEK); ceramic; titanium oxide; fiberglass; parylene) that is substantially transparent to the electromagnetic or magnetic fields generated by the at least one first MI antenna 310 (e.g., such that the housing 305 does not substantially interfere with power, data, and/or control signal transmission between the apparatus 300 and the device 400). [0041] As schematically illustrated by FIGs. 3A-3G, the housing 305 can comprise a substantially planar portion configured to be positioned beneath a cushion 307 (e.g., pillow; mattress), the cushion 307 configured to receive the body portion 405 with at least a portion of the cushion 307 between the body portion 405 and the at least one first MI antenna 310. For example, the cushion 307 can be a compressible pillow upon which the recipient can rest their head (e.g., during a sleep session) with the substantially planar portion of the housing 305 on the mattress and beneath the cushion 307. In certain implementations, the apparatus 300 comprises the cushion 307, while in certain other implementations, the apparatus 300 does not comprise a cushion 307 (e.g., but can be configured to be used in conjunction with a cushion 307).

[0042] In certain implementations, the at least one first MI antenna 310 comprises a single substantially planar first MI antenna 310 (e.g., first communication coil), while in certain other implementations, the at least one first MI antenna 310 comprises a plurality of substantially planar first MI antennas 310 (see, e.g., FIG. 2). The first MI antennas 310 can be positioned to overlap one another (see, e.g., two first MI antennas 310a,b of FIG. 2) or to not overlap one another. At least some of the first MI antennas 310 can be substantially parallel or coplanar with one another, and at least some of the first MI antennas 310 can be substantially perpendicular to one or more other first MI antennas 310 (e.g., in two or three orthogonal orientations). For example, the housing 305 can comprise other portions that are at non-zero angles relative to the substantially planar portion beneath the cushion 307, the other portions containing other first MI antennas 310 at non-zero angles (e.g., orthogonal) relative to the at least one first MI antenna 310 within the substantially planar portion of the housing 305. The first MI antennas 310 can be positioned around a region (e.g., along two or more sides of the region) in which the body portion 405 and the device 400 are to be placed.

[0043] FIGs. 4A-4F schematically illustrate various example first MI antennas 310 in accordance with certain implementations described herein. FIGs. 4A and 4B schematically illustrate a perspective view and a top view, respectfully, of an example substantially circular first MI antenna 310 in accordance with certain implementations described herein. FIG. 4C schematically illustrates a perspective view of another example substantially circular first MI antenna 310 in accordance with certain implementations described herein. FIGs. 4D and 4E schematically illustrate a perspective view and a top view, respectfully, of an example substantially rectangular first MI antenna 310 in accordance with certain implementations described herein. FIG. 4F schematically illustrates a perspective view of another example substantially rectangular first MI antenna 310 in accordance with certain implementations described herein.

[0044] In certain implementations, the at least one first MI antenna 310 comprises at least one electrically conductive and substantially planar first coil 312 configured to be in magnetically inductive communication with the at least one second MI antenna 410 (e.g., second communication coil) of the device 400. For example, the at least one first coil 312 can comprise an electrically conductive wire (e.g., platinum, gold, copper, or other metal; electrically insulated single-strand or multi-strand) with one or more loops wound around and substantially orthogonal to an antenna axis 314. For another example, the first coil 312 can comprise a metal trace (e.g., copper) with one or more loops on a flexible substrate (e.g., printed circuit board) and that run (e.g., wind) around the antenna axis 314.

[0045] As shown in FIGs. 4A-4B and 4D-4E, the first coil 312 of a first MI antenna 310 can have coil loops that are substantially co-planar with one another (e.g., planar spiral), and as shown in FIGs. 4C and 4F, the coil loops can be substantially parallel to one another (e.g., spring-shaped). While FIGs. 4A-4F show the first coil 312 having three coil loops, other numbers of coil loops (e.g., 2, 4, 5, 6, or more) and other shapes (e.g., oval, obround, fabiform, reniform, or others) are also compatible with certain implementations described herein. In certain implementations in which the apparatus 300 comprises multiple first MI antennas 310 with multiple first coils 312, the first coils 312 can comprise the same number of coil loops as one another and the coil loops can have substantially equal widths and/or shapes as one another, while in certain other implementations, two or more of the first MI antennas 310 can have first coils 312 with numbers of coil loops, widths, and/or shapes of the coil loops that differ from one another.

[0046] The first coil 312 can have a lateral dimension (e.g., diameter, length, and/or width, along a direction substantially perpendicular to the antenna axis 314) less than or equal to 500 millimeters (e.g., in a range of less than 100 millimeters; in a range of 15 millimeters to 60 millimeters; in a range of 50 millimeters to 200 millimeters; in a range of 100 millimeters to 300 millimeters; in a range greater than 100 millimeters; in a range of 125 millimeters to 250 millimeters; in a range greater than 300 millimeters). In certain implementations, the first coil 312 has at least one lateral dimension that is substantially equal to or greater than (e.g., by a factor of 1.2, 2, 3, 4, 5, or more) at least one lateral dimension of the at least one second MI antenna 410 of the device 400.

[0047] In certain implementations, the at least one sensor 320 is configured to detect at least one aspect of an environment of the apparatus 300 and the device 400. As described herein, the at least one aspect of the environment has an effect on an efficiency of power transfer from the apparatus 300 to the device and/or on an amount of energy emanating from the at least one first MI antenna 310 that is absorbed by the recipient’s body. The absorbed energy can be electromagnetic radiated energy, or energy generated by the electric or magnetic fields. For example, the at least one aspect that is detected can include a presence, location, and/or at least one attribute (e.g., thickness; compressibility; dielectric constant) of a cushion 307 between the body portion 405 and the at least one first MI antenna 310. For another example, the at least one aspect can include a clearance (e.g., distance) between the at least one first MI antenna 310 and the body portion 405. For another example, the at least one aspect can include an extent (e.g., position and dimensions, such as height, width, thickness, or volume) of tissue of the recipient’s body (e.g., tissue of another body portion 406 in which the device 400 is not implanted) within a power transmission range of the at least one first MI antenna 310. For another example in which the apparatus 300 is configured to be operated while between the body portion 405 and a surface (e.g., the apparatus 300 on a top surface of a mattress and the body portion 405 above the apparatus 300), the at least one aspect can include an orientation of the apparatus 300 relative to the surface.

[0048] In certain implementations, the at least one sensor 320 is configured to generate at least one sensor signal 322 indicative of the detected at least one aspect of the environment (e.g., multiple sensors 320 that are configured to generate sensor signals 322 indicative of multiple aspects of the environment). The at least one sensor 320 can comprise one or more: accelerometers, gyroscopes, tilt sensors, inclinometers, pressure sensors, capacitive sensors, impedance sensors, radio-frequency (RF) reflectometry sensors, ultra- wide-band (UWB) radar sensors, millimeter-wave radar sensors, heat sensors, infrared, ultraviolet, or visible light sensors, ultrasonic sensors, biometric sensors, radio-frequency identification (RFID) sensors, near-field-communication (NFC) sensors. In certain implementations, the at least one sensor 320 comprises a plurality of sensors 320 distributed across the apparatus 300 (e.g., over a surface of the housing 305), while in certain other implementations, the at least one sensor 320 comprises a single sensor 320 (e.g., located in proximity to a region in which multiple first coils 312 of the at least one first MI antenna 310 overlap one another).

[0049] In certain implementations, the at least one sensor 320 is configured to generate at least one sensor signal 322 indicative of a presence, location, and or at least one attribute of the cushion 307 between the body portion 405 and the at least one first MI antenna 310. For example, the at least one sensor 320 can comprise at least one ultrasonic sensor configured to detect the cushion 307 and/or an attribute of the cushion 307 (e.g., the thickness of the cushion 307 between the body portion 405 and the at least one first MI antenna 310). For another example, the at least one sensor 320 can comprise at least one radio-frequency identification (RFID) sensor (e.g., reader) or at least one near-field communication (NFC) sensor (e.g., reader) configured to receive information from at least one RFID or NFC tag on or within the cushion 307. The at least one RFID or NFC tag can include information regarding at least one attribute of the cushion 307 (e.g., material; compressibility; stiffness; rigidity; softness; hardness; dielectric constant; minimum thickness; maximum thickness).

[0050] In certain implementations, the at least one sensor 320 is configured to generate at least one sensor signal 322 indicative of a clearance between the at least one first MI antenna 310 and the body portion 405 and/or an extent of the recipient’s tissue within a power transmission range of the at least one MI antenna 310. The extent of the recipient’s tissue can include the location (e.g., distance), dimensional size (e.g., height, width, thickness, volume) and/or orientation (e.g., relative to the at least one first MI antenna 310) of the body portion 405 in which the device 400 is implanted (e.g., head) and/or of another body portion 406 in which the device 400 is not implanted (e.g., arm; hand). For example, the at least one sensor 320 can comprise at least one UWB radar sensor (e.g., X4 UWB short-range impulse radar transceiver system-on-chip sensor available from Novelda Oslo of Oslo Norway) and/or at least one mm-wave radar sensor (e.g., 24 GHz human presence sensing module). For another example, the at least one sensor 320 can comprise at least one capacitive sensor (e.g., MS889X-series capacitive sensor available from Microdul AG of Zurich Switzerland). A capacitive sensor can provide sufficient accuracy, operating based on the detection of the higher dielectric constant of tissue (e.g., s > 20) compared to the dielectric constant of air (e.g., s = 1) and cushion materials (e.g., s < 4). Other example sensors 320 compatible with certain implementations described herein include but are not limited to: human body detection sensors; acoustic sensors; pressure sensors; ultrasonic sensors; impedance sensors; radio-frequency (RF) reflectometry sensors, biometric sensors; heat sensors; infrared sensors (e.g., Grid-EYE infrared array sensor) and/or ultraviolet or visible light sensors (e.g., sensors configured to recognize shapes of human body portions). In certain implementations, the at least one sensor signal 322 generated by at least one sensor 320 is indicative of the presence, location, and/or orientation of the tissue relative to the at least one first MI antenna 310 while the tissue is substantially not moving (e.g., the tissue does not have to move to be detected by the at least one sensor 320).

[0051] In certain implementations, the apparatus 300 is configured to be operated while positioned between the body portion 405 and a surface (e.g., the apparatus 300 on a top surface of a mattress and the body portion 405 on or above the apparatus 300) and the at least one sensor 320 is configured to generate at least one sensor signal 322 indicative of an orientation of the apparatus 300 relative to the surface. For example, the at least one first MI antenna 310 can be asymmetrically positioned within a substantially planar portion of the housing 305 having a first side and a second side opposite to the first side, with the at least one first MI antenna 310 closer to the first side than to the second side (e.g., to provide a minimum clearance distance between the at least one first MI antenna 310 and the recipient’s tissue). A distance between the at least one first MI antenna 310 and the device 400 can be dependent on the orientation of the housing 305 relative to an underlying surface (e.g., mattress). The at least one sensor 320 can be configured to detect the orientation of the housing 305 and can be selected from the group consisting of: at least one accelerometer; at least one gyroscope; at least one tilt sensor; at least one inclinometer. The at least one sensor signal 322 can be indicative of whether the first side or the second side of the portion of the housing 305 is closer to the body portion 405 (e.g., whether the first side or the second side of the portion of the housing 305 is on the mattress underlying the housing 305).

[0052] In certain implementations, the control circuitry 330 comprises one or more microprocessors (e.g., application-specific integrated circuits; generalized integrated circuits programmed by software with computer executable instructions; microelectronic circuitry; microcontrollers) and at least one storage device (e.g., at least one tangible or non-transitory computer readable storage medium; read only memory; random access memory; flash memory) configured to store information (e.g., data; commands) accessed by the one or more microprocessors during operation. The at least one storage device can be encoded with software (e.g., a computer program downloaded as an application) comprising computer executable instructions for instructing the one or more microprocessors (e.g., executable data access logic, evaluation logic, and/or information outputting logic). In certain implementations, the one or more microprocessors execute the instructions of the software to provide functionality as described herein. In certain implementations, the control circuitry 330 comprises communication circuitry (e.g., RF antenna; Bluetooth antenna) configured to receive data and/or control signals from an external device (e.g., smart phone; smart tablet; smart watch; other remote device operated by the recipient) and/or to transmit data signals to the external device.

[0053] In certain implementations, the control circuitry 330 comprises at least one coil driver 332 configured to provide at least one electrical current 316 to the at least one first MI antenna 310. In certain other implementations, the at least one coil driver 332 is separate from the control circuitry 330 but is responsive to control signals from the control circuitry 330. The control circuitry 330 (e.g., via the at least one coil driver 332 responding to control signals from the control circuitry 330) can be configured to adjust, in response to the at least one sensor signal 322, the at least one electrical current 316 flowing through the at least one first coil 312 of the at least one first MI antenna 310. For example, in response to the at least one sensor signal 322 received from the at least one sensor 320, the control circuitry 330 can adjust the at least one electrical current 316 flowing through the at least one first coil 312 (e.g., at least one magnitude, at least one phase, and/or at least one frequency of the at least one electrical current 316) By adjusting the at least one electrical current 316, the control circuitry 330 can adjust a power level transmitted by the at least one first coil 312 (e.g., adjusting the at least one electrical current 316 flowing through the at least one first MI antenna 310 to be less than a predetermined threshold level).

[0054] In certain implementations, the apparatus 300 is configured, upon activation of the apparatus 300 and/or upon initiation of a power transfer mode, to transfer power, data, and/or control signals (e.g., transcutaneously) to the device 400 and/or to receive data and/or control signals from the device 400 (e.g., transcutaneously) while the body portion 405 is in a plurality of positions and/or orientations relative to the apparatus 300. During the power transfer mode, the transfer rate of power from the apparatus 300 to the device 400 and the field exposure of the recipient’s body to electric, magnetic, and/or electromagnetic fields from the apparatus 300 both depend on various aspects of the environment of the apparatus 300 and the device 400. For example, the power transfer rate and/or the amount of field exposure can depend on the relative distance and/or orientation of the at least one first MI antenna 310 of the apparatus 300 to the at least one second MI antenna 410 of the device 400, the existence of intervening material (e.g., tissue material; cushion material) between the at least one first MI antenna 310 and the at least one second MI antenna 410, and the electrical and magnetic properties of any such intervening material.

[0055] At least some aspects of the environment of the apparatus 300 and the device 400 can be static (e.g., not varying appreciably during the power transfer mode/sleep session and/or between different iterations of the power transfer mode/sleep session). Examples of static environmental aspects include but are not limited to: physical dimensions of the recipient and/or the body portion 405; the location of the at least one second MI antenna 410 on or within the body portion 405; the physical dimensions and properties of the at least one first MI antenna 310 and/or the at least one second MI antenna 410; the physical dimensions of the apparatus 300 (e.g., the location of the at least one first MI antenna 310 relative to the housing 305).

[0056] In addition, at least some aspects of the environment of the apparatus 300 and the device 400 can be variable (e.g., varying appreciably during the power transfer mode/sleep session and/or between different iterations of the power transfer mode/sleep session). The variations of these aspects can be due to motion of the recipient and/or the apparatus 300 or use of different cushions 307. Examples of variable environmental aspects include but are not limited to: distance and/or orientation of the body portion 405 relative to the apparatus 300; distance and/or orientation of the at least one second MI antenna 410 relative to the at least one first MI antenna 310; existence and/or amount of intervening material (e.g., tissue material; cushion material) between the at least one second MI antenna 410 and the at least one first MI antenna 310 (e.g., the thickness of the cushion 307 between the body portion 405 and the apparatus 300; an arm and/or hand of the recipient moved to be in proximity to the apparatus 300). [0057] In certain implementations, the at least one sensor 320 is configured to detect one or more of these aspects of the environment (e.g., at least one varying aspect; at least one non-varying aspect) and to provide sensor signals 322 indicative of these environmental aspects to the control circuitry 330. To compensate for any variations of aspects of the environment that affect the power transfer rate from the apparatus 300 to the device 400 (e.g., by attenuating or absorbing a larger fraction of the power emanating from the apparatus 300, thereby lessening the amount of power received by the at least one second MI antenna 410), the control circuitry 330 can adjust (e.g., vary the magnitude, phase, and/or frequency) the at least one electrical current 316 flowing through the at least one first MI antenna 310 such that an optimal power transfer rate is achieved.

[0058] However, such adjustments can also increase the field exposure of various tissue portions of the recipient in proximity to the apparatus 300 to the electric, magnetic, and/or electromagnetic fields emanating from the apparatus 300. This field exposure can have physical effects (e.g., stimulation; heating) on the tissue, and for sufficiently high field magnitudes, these physical effects can be deleterious (e.g., causing damage and/or discomfort to the recipient). In certain implementations, the control circuitry 330 is further configured to adjust the at least one electrical current 316 flowing through the at least one first MI antenna 310 such that the transmitted power level reduces (e.g., avoids) such deleterious physical effects.

[0059] These deleterious physical effects can be characterized by one or more medical safety regulatory standards for exposure of a recipient’s body to electric, magnetic, and/or electromagnetic fields. Examples of medical safety regulatory standards compatible with certain implementations described herein include but are not limited to: specific absorption rate (SAR) standard; nerve stimulation (NS) standard; tissue heating (TH) standard. A SAR value can be defined as an average rate of energy deposition (e.g., absorption) per unit mass of body tissue (e.g., units of W/kg) when exposed to a radio frequency (RF) electromagnetic, magnetic, or electric field. A NS value can be defined as a level of electric fields (e.g., voltage gradients) induced within a body portion by exposure to electric and/or magnetic fields (e.g., with frequencies of 3 kHz to 10 MHz). For sufficiently intense induced electric fields, the resting membrane potential of the tissue can result in spontaneous depolarization of the membrane and the generation of spurious action potentials. A TH value can be defined as a level of thermal heating induced within a body portion by exposure to electromagnetic, electric, and/or magnetic fields (e.g., with frequencies of 100 kHz to 300 GHz), where a sufficient temperature increase can result in a physiologically significant effect. The TH value can be determined using a thermal dose parameter that quantifies effects from heating using a tissue model (e.g., CEM43).

[0060] In certain implementations, to inhibit (e.g., avoid) deleterious physical effects potentially resulting from operation of the apparatus 300 during the power transfer mode (e.g., during a sleep session of the recipient), the control circuitry 330 is configured to access a predetermined threshold level (e.g., corresponding to a maximum level in compliance with a predetermined medical safety regulatory standard for field exposure of the recipient’s body) to set an upper bound on the power emanating from the apparatus 300 (e.g., an upper bound on the at least one electrical current 316 flowing through the at least one first MI antenna 310). In certain implementations, the at least one sensor 320 is configured to detect at least one aspect of the environment (e.g., at least one varying aspect; at least one non-varying aspect) and to generate the at least one sensor signal 322 indicative of at least one detected aspect of the environment, and the control circuitry 330 is configured to maintain the at least one electrical current 316 flowing through the at least one first MI antenna 310 to be less than the predetermined threshold level in response to at least one detected aspect of the environment of the apparatus 300 and the device 400 (e.g., in response to the at least one sensor signal 322).

[0061] In certain implementations, the at least one sensor 320 can detect at least one environmental aspect and can generate at least one sensor signal 322 that is indicative of the at least one detected environmental aspect. The control circuitry 330 can utilize information from the at least one sensor signal 322 and other previously stored information (e.g., stored in a data storage device of the control circuitry 330 or in an external device in communication with the control circuitry 330) to calculate a transmitted power level for transmitting power to the device 400 at an optimal (e.g., maximized) power transfer rate while maintaining the field exposure to be in compliance with a predetermined medical safety regulatory standard.

[0062] As shown in FIGs. 3A-3E, during a sleep session or between different sleep sessions, different surfaces of the body portion 405 can rest on a cushion 307 between the body portion 405 (e.g., head) and the apparatus 300, with the body portion 405 in different positions and/or orientations and with the cushion 307 having different thicknesses during the sleep session. While FIGs. 3A-3E schematically show the at least one first MI antenna 310 as comprising at least one substantially planar antenna coil 312 and the at least one second MI antenna 410 as comprising at least one substantially planar antenna coil 412, other shapes and sizes of the first and second antenna coils 312, 412 are also compatible with certain implementations described herein. While FIGs. 3A-3E show some specific example configurations of the body portion 405 relative to the apparatus 300, other configurations (e.g., intermediate configurations in which the body portion 405 is at other positions and/or orientations relative to the apparatus 300) are also possible.

[0063] In these various configurations, the distance and/or orientation of the at least one second MI antenna 410 relative to the at least one first MI antenna 310 can vary (e.g., can depend on which surface of the body portion 405 is resting on the cushion 307) as can the amounts of tissue material and cushion material between the at least one second MI antenna 410 and the at least one first MI antenna 310. The coupling coefficient between the at least one second MI antenna 410 and the at least one first MI antenna 310 also varies depending on these environmental aspects. The control circuitry 330 can receive, in real-time, the sensor signals 322 indicative of the detected aspects, and can use information regarding the detected aspects and other aspects to calculate, in real-time (e.g., dynamically), an optimal power level to be transmitted by the at least one first MI antenna 310. The control circuitry 330 can also adjust the at least one electrical current 316 to provide an optimal power transfer rate to the device 400 while keeping the field exposure of the recipient’s tissue below a maximum level in compliance with a predetermined medical safety regulatory standard.

[0064] FIGs. 3A-3C schematically illustrate an example configuration of the body portion 405 (e.g., head) relative to the apparatus 300 in accordance with certain implementations described herein. In this example configuration, a first surface (e.g., back side of the head) of the body portion 405 rests on the cushion 307. The at least one second MI antenna 410 can be substantially perpendicular to the first surface and substantially parallel to a second surface (e.g., the left side of the head) and can be substantially perpendicular to the at least one first MI antenna 310.

[0065] In this configuration, the body portion 405 can be at a variety of positions and orientations relative to the apparatus 300, such that the at least one second MI antenna 410 can be at a variety of positions and orientations relative to the at least one first MI antenna 310. As shown in FIG. 3 A, the at least one second MI antenna 410 can have a first position coordinate 430a along a first direction 432a substantially parallel to the at least one first MI antenna 310 and a second position coordinate 430b along a second direction 432b substantially parallel to the at least one first MI antenna 310 and substantially perpendicular to the first direction 432a. The first and second position coordinates 430a, b can vary due to movement of the body portion 405 across the apparatus 300. As shown in FIG. 3B, the at least one second MI antenna 410 can also have a third position coordinate 430c along a third direction 432c substantially perpendicular to the first and second directions 432a, b. The third position coordinate 430c can vary due to different thicknesses of the cushion 307 between the body portion 405 and the apparatus 300. As shown in FIG. 3C, the at least one second MI antenna 410 can have a variety of orientations relative to the at least one first MI antenna 310 due to the orientation of the body portion 405 relative to the apparatus 300 (e.g., while remaining substantially perpendicular to the at least one first MI antenna 310).

[0066] In FIGs. 3A-3C, the first and second position coordinates 430a, b have ranges of possible values at which the first surface of the body portion 405 is resting either on the cushion 307 or on the housing 305 (e.g., without a cushion 307 present). The third position coordinate 430c has a range of possible values that has a lower bound (e.g., corresponding to a minimum cushion thickness of zero for the absence of a cushion 307) substantially equal to a first fixed distance (e.g., in a range of 60 mm to 90 mm) between the at least one second MI antenna 410 and the first surface and can have an upper bound substantially equal to a sum of the fixed first distance and a maximum cushion thickness (e.g., in a range of 25 mm to 100 mm).

[0067] FIGs. 3D and 3E schematically illustrate two other example configurations of the body portion 405 in accordance with certain implementations described herein. As with the configuration of FIGs. 3A-3C, the at least one second MI antenna 410 in the configurations of FIGs. 3D and 3E can be at a variety of positions having first, second, and third position coordinates 430a, b,c in the first, second, and third directions 432a, b,c, respectively, and the body portion 405 can have different orientations relative to the apparatus 300. In the configurations of FIGs. 3D and 3E, the at least one second MI antenna 410 is substantially parallel to the second surface and to a third surface (e.g., right side of the head) and is substantially parallel to at least one first MI antenna 310.

[0068] In FIG. 3D, a second surface of the body portion 405 (e.g., left side of the head) rests on the cushion 307. The ranges of the possible first and second position coordinates 430a, b in the configuration of FIG. 3D can be substantially the same as the ranges of the first and second position coordinates 430a, b in the configuration of FIGs. 3A-3C. However, the range of possible third position coordinates 430c in the configuration of FIG. 3D can be substantially different from the corresponding range in the configuration of FIGs. 3 A-3C. The range of the third position coordinate 430c of the configuration of FIG. 3D can have a lower bound (e.g., corresponding to the minimum cushion thickness of zero for the absence of a cushion 307) substantially equal to a second fixed distance (e.g., in a range of 4 mm to 10 mm; smaller than the first fixed distance) between the at least one second MI antenna 410 and the second surface and can have an upper bound substantially equal to a sum of the fixed second distance and the maximum cushion thickness. Thus, the at least one second MI antenna 410 is generally farther from the at least one first MI antenna 310 in the configuration of FIG. 3B than in the configuration of FIG. 3D.

[0069] In FIG. 3E, a third surface of the body portion 405 (e.g., right side of the head) rests on the cushion 307. The ranges of the possible first and second position coordinates 430a, b in the configuration of FIG. 3E can be substantially the same as the ranges of the first and second position coordinates 430a, b in the configuration of FIGs. 3A-3C. However, the range of possible third position coordinates 430c in the configuration of FIG. 3E can be substantially different from the corresponding range in the configuration of FIGs. 3A-3C and the configuration of FIG. 3D. The range of the third position coordinate 430c of the configuration of FIG. 3E can have a lower bound (e.g., corresponding to the minimum cushion thickness of zero for the absence of a cushion 307) substantially equal to a third fixed distance (e.g., in a range of 120 mm to 180 mm; larger than the first and second fixed distances) between the at least one second MI antenna 410 and the third surface and can have an upper bound substantially equal to a sum of the fixed third distance and the maximum cushion thickness. Thus, the at least one second MI antenna 410 is generally farther from the at least one first MI antenna 310 in the configuration of FIG. 3E than in the configuration of FIG. 3B. [0070] Also, as shown in FIGs. 3B, 3D, and 3E, the orientation between the at least one second MI antenna 410 and the at least one first MI antenna 310 about the second direction 432b can differ depending on the surface of the body portion 405 that is resting on the cushion 307. The coupling coefficient between the at least one second MI antenna 410 and the at least one first MI antenna 310 is generally larger when the at least one second MI antenna 410 and the at least one first MI antenna 310 are substantially parallel to one another and is generally smaller when the at least one second MI antenna 410 and the at least one first MI antenna 310 are substantially perpendicular to one another. Furthermore, as shown in FIG. 3C, the relative orientation about the third direction 432c between at least one second MI antenna 410 and the at least one first MI antenna 310 can depend on the orientation of the body portion 405 relative to the apparatus 300. The coupling coefficient can also depend on the relative orientation about the third direction 432c.

[0071] In addition, as shown in FIGs. 3B, 3D, and 3E, the space between the at least one second MI antenna 410 and the top surface of the housing 305 can comprise different fractions of different materials. For example, the distance between the at least one second MI antenna 410 and the at least one first MI antenna 310 can comprise a tissue length extending through the recipient’s tissue and a cushion length extending through the cushion 307. As shown in FIG. 3B, the tissue length and cushion length can be approximately equal to one another, while as shown in FIG. 3D, the tissue length can be substantially less than the cushion length, and as shown in FIG. 3E, the tissue length can be substantially greater than the cushion length. The recipient’s tissue can generally be more absorptive to electromagnetic radiated energy or energy generated by the electric or magnetic fields than is the cushion material, so the different fractions of tissue material and cushion material between the at least one second MI antenna 410 and the at least one first MI antenna 310 can not only affect the power transfer rate but also the field exposure of the recipient’s body.

[0072] In certain implementations, the relative distance between the at least one second MI antenna 410 and the at least one first MI antenna 310 also depends on the position and/or orientation of other body portions of the recipient. For example, as shown in FIG. 3F, a recipient can move another body portion 406 (e.g., arm; hand) to be positioned between the body portion 405 (e.g., head) and the cushion 307. Besides affecting the distance and/or orientation of the at least one second MI antenna 410 relative to the at least one first MI antenna 310, the body portion 406 at this position can absorb at least some of the power emanating from the apparatus 300, so the body portion 406 can contribute to the field exposure to be accounted for in the determination of the transmitted power level (e.g., the at least one electrical current 316).

[0073] In certain implementations, the apparatus 300 is operable in a plurality of orientations relative to the environment. For example, the apparatus 300 can comprise a first surface and second surface substantially opposite to the first surface and the at least one first MI antenna 310 can be positioned within the apparatus 300 closer to the second surface than to the first surface. In a first orientation (see., e.g., FIGs. 3B and 3D-3F), the apparatus 300 can be operated with the first surface serving as a bottom surface resting on an underlying element (e.g., mattress), and the second surface serving as a top surface upon which the cushion 307 and/or body portion 405 rests. In a second orientation (see, e.g., FIG. 3G), the apparatus 300 can be flipped relative to the first orientation such that the second surface serves as the bottom surface and the first surface serves as the top surface, and the at least one first MI antenna 310 is farther from the body portion 405 (e.g., and the at least one second MI antenna 410). As a result, the relative distance of the at least one first MI antenna 310 and the at least one second MI antenna 410 can depend on the orientation of the apparatus 300 relative to the environment.

[0074] In certain implementations, the information contained in the at least one sensor signal 322 is usable by the control circuitry 330 to determine the expected coupling coefficient between the at least one second MI antenna 410 and the at least one first MI antenna 310 and/or the expected field exposure of the recipient’s tissue as a function of the at least one electrical current 316 flowing through the at least one first MI antenna 310. Examples of such information include but are not limited to: configuration of the body portion 405 (e.g., side of the head resting on the cushion 307); position of the body portion 405 along the first, second, and/or third directions 432a, b,c; orientation of the body portion 405 about the second and/or third directions 432b, c; thickness (e.g., minimum thickness; maximum thickness) of the cushion 307 in the third direction 432c; fractions of tissue material and cushion material between the body portion 405 and the apparatus 300; at least one attribute (e.g., identity, type, compressibility, stiffness; softness, hardness, and/or dielectric constant) of the material of the cushion 307 (e.g., when the cushion 307 is not a component of the apparatus 300); orientation of the housing 305 relative to an underlying surface (e.g., mattress).

[0075] In certain implementations, the control circuitry 330 is configured to access stored information that is usable by the control circuitry 330 to determine the expected coupling coefficient between the at least one second MI antenna 410 and the at least one first MI antenna 310 and/or the expected field exposure of the recipient’s tissue as a function of the at least one electrical current 316. Examples of such stored information include but are not limited to: dimensions and/or other parameters of the at least one first MI antenna 310, the at least one second MI antenna 410, and/or the body portion 405 (e.g., dimensions of the head); location of the at least one second MI antenna 410 relative to the body portion 405 and location of the at least one sensor 320 relative to the at least one first MI antenna 310 (e.g., to be used in conjunction with the detected position of the body portion 405 relative to the at least one sensor 320 to determine the position of the at least one second MI antenna 410 relative to the at least one first MI antenna 310); at least one attribute (e.g., identity, type, compressibility, softness, hardness, and/or dielectric constant) of the material of the cushion 307 (e.g., when the cushion 307 is a component of the apparatus 300).

[0076] In certain implementations, the control circuitry 330 is configured to utilize the information received from the at least one sensor signal 322 and the accessed stored information to determine the magnitude, phase, and/or frequency of the at least one electrical current 316 to be used to achieve an optimal power transfer rate from the apparatus 300 to the device 400. The control circuitry 330 can take into account the different coupling coefficients between the at least one second MI antenna 410 and the at least one first MI antenna 310 and the different absorptive properties of any intervening material between the at least one second MI antenna 410 and the at least one first MI antenna 310 in the different configurations. In certain implementations in which the at least one first MI antenna 310 comprises multiple first coils 312, the control circuitry 330 is configured to use beamforming techniques (e.g., adjusting the magnitude, phase, and/or frequency of the electrical currents 316 flowing through the multiple first coils 312 to direct the electrical, magnetic, and/or electromagnetic fields in a direction towards the at least one second MI antenna 410) while maintaining the field exposure to be in compliance with the predetermined medical safety regulatory standard. [0077] FIG. 5 is a flow diagram of an example method 500 for operating an apparatus 300 in accordance with certain implementations described herein. While the method 500 is described by referring to some of the structures of the example apparatus 300 of FIGs. 2, 3A-3G, and 4A-4F, other apparatus and systems with other configurations of components can also be used to perform the method 500 in accordance with certain implementations described herein.

[0078] In an operational block 510, the method 500 comprises wirelessly transmitting power from a power source (e.g., apparatus 300) to a device (e.g., device 400) on or implanted within a portion of a recipient’s body (e.g., body portion 405), the device inductively coupled to the power source. For example, as shown in FIGs. 3A-3G, the device can comprise an implanted portion of an acoustic prosthesis system positioned on a head of the recipient and the pad can comprise a cushion 307 (e.g., pillow) upon which the head rests during said wirelessly transmitting the power (e.g., during a sleep session of the recipient).

[0079] In an operational block 520, the method 500 further comprises, while wirelessly transmitting the power from the power source to the device, generating information relevant to exposure of the recipient’s body to electric, magnetic, and/or electromagnetic fields generated by the power source. For example, the information can comprise at least one of: a presence and/or location of a pad (e.g., cushion 307) between the power source and the recipient’s body, at least one attribute of the pad between the power source and the recipient’s body, a clearance between the power source (e.g., the at least one first MI antenna 310) and the body portion 405, and an extent of the recipient’s body within a power transmission range of the power source. Generating the information can comprise receiving at least one signal (e.g., sensor signal 322) from at least one sensor (e.g., sensor 320) of the power source. In certain implementations, wirelessly transmitting the power and gathering sensor information are performed using different timeslots. For example, the at least one sensor 320 can be activated in a time division multiple access (TDMA) scheme with the at least one MI antenna 310 to reduce (e.g., avoid) potential reduction of sensor sensitivity and/or accuracy caused by concurrent sensing and power transfer.

[0080] For example, referring to FIGs. 3A-3B, at one moment during a power transfer mode/sleep session, the recipient’s head can have an orientation relative to the apparatus 300 such that the back surface of the recipient’s head rests on the cushion 307. The control circuitry 330 can receive detected information regarding one or more detected environmental aspects in real-time (e.g., via the sensor signals 322 from the at least one sensor 320) and can access stored information (e.g., from data storage) regarding other environmental aspects. For example, the at least one sensor 320 can dynamically detect the orientation of the head relative to the apparatus 300 as well as the distance between the at least one sensor 320 and the back surface of the recipient’s head and/or the thickness of the cushion 307 and can provide sensor signals 322 indicative of these detected environmental aspects in real-time to the control circuitry 330. The control circuitry 330 can access stored information regarding the position of the at least one first MI antenna 310 relative to the at least one sensor 320 and the distance between the back surface of the recipient’s head and the at least one second MI antenna 410, and can use the detected information and the accessed information to calculate, in real-time, the distance and orientation between the at least one first MI antenna 310 and the at least one second MIM antenna 410. In addition, the control circuitry 330 can access stored information regarding the spatial distribution of fields and/or power transmitted from the at least one first MI antenna 310 (e.g., the power transmission range of the at least one first MI antenna 310) to calculate, in real-time, the power transfer rate of power from the at least one first MI antenna 310 to the at least one second MI antenna 410 and the field exposure of the recipient’s tissue as functions of the electrical current 316 flowing through the at least one first MI antenna 310. The control circuitry 330 can access stored information regarding the predetermined medical safety regulatory standard for field exposure of the recipient’s tissue and can dynamically determine an optimal power level to be transmitted by the at least one first MI antenna 310 to the at least one second MI antenna 410 (e.g., the maximum power level or current flowing through the at least one first MI antenna 310 for which the field exposure complies with the predetermined medical safety regulatory standard) at the moment during the power transfer mode/sleep session.

[0081] In an operational block 530, the method 500 further comprises, in response to the information, adjusting the power transmitted from the power source to the device such that the electric, magnetic, and/or electromagnetic fields comply with the predetermined medical safety regulatory standard for exposure of the recipient’s body. For example, the control circuitry 330 can adjust the transmitted power level to be the determined optimal power level. [0082] In certain implementations, generating the information can be performed periodically (e.g., at regular intervals) to detect changes that have occurred during the power transmission mode (e.g., sleep session) and adjusting the power transmitted can be performed periodically in response to the periodically generated information. For example, at other moments during the power transmission mode/sleep session, the recipient can move to different positions and/or orientations while the back surface of the head continues to rest on the cushion 307 (see, e.g., FIG. 3C) or with other surfaces resting on the cushion 307 (see, e.g., FIGs. 3D and 3E), the thickness of the cushion 307 can change as a result of the recipient’s movement, the recipient can move other tissue portions into the power transmission range of the at least one first MI antenna 310 (see, e.g., FIG 3G), etc. By periodically detecting environmental aspects during the power transmission mode/sleep session and accessing corresponding stored information as appropriate, the control circuitry 330 can determine and maintain an optimal transmitted power level throughout the power transmission mode/sleep session despite the recipient’s movements.

[0083] 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 be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. [0084] 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 various devices, various implementations described herein can be incorporated in a variety of other suitable devices, methods, and contexts. More generally, as can be appreciated, certain implementations described herein can be used in a variety of implantable medical device contexts that can benefit from certain attributes described herein.

[0085] 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.

[0086] 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.

[0087] The invention described and claimed herein is not to be limited in scope by the specific example implementations herein disclosed, since these implementations are intended 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: at least one first magnetic induction (MI) antenna configured to wirelessly transmit power to at least one second MI antenna of a device within or on a body portion of a recipient; at least one sensor configured to generate at least one sensor signal; and control circuitry in electrical communication with the at least one first MI antenna and the at least one sensor, the control circuitry configured to, in response to the at least one sensor signal, determine at least one of: a presence, location, and/or at least one attribute of a cushion between the body portion and the at least one first MI antenna, a clearance between the at least one first MI antenna and the body portion, and an extent of tissue of the recipient within a power transmission range of the at least one first MI antenna, the control circuitry further configured to adjust, in response to the at least one sensor signal, a power level transmitted by the at least one first MI antenna.

2. The apparatus of claim 1, wherein the control circuitry comprises at least one coil driver configured to provide at least one electrical current to the at least one first MI antenna.

3. The apparatus of claim 2, wherein the control circuitry is configured to, in response to the at least one sensor signal, adjust the at least one electrical current flowing through the at least one first MI antenna to be less than a predetermined threshold level.

4. The apparatus of claim 3, wherein the predetermined threshold level corresponds to a maximum level in compliance with a predetermined medical safety regulatory standard for exposure of the recipient.

5. The apparatus of claim 4, wherein the predetermined medical safety regulatory standard comprises at least one of: a specific absorption rate (SAR) standard, a nerve stimulation (NS) standard, and a tissue heating standard.

6. The apparatus of any of claims 2 to 5, wherein the control circuitry is further configured to, in response to the at least one sensor signal, adjust at least one magnitude, at least one phase, and/or at least one frequency of the at least one electrical current.

7. The apparatus of any preceding claim, wherein the at least one sensor is selected from the group consisting of: accelerometers, gyroscopes, tilt sensors, inclinometers, pressure sensors, capacitive sensors, impedance sensors, radio-frequency (RF) reflectometry sensors, ultra-wide-band (UWB) radar sensors, millimeter-wave radar sensors, heat sensors, infrared, ultraviolet, or visible light sensors, ultrasonic sensors, biometric sensors, radio-frequency identification (RFID) sensors, near-field-communication (NFC) sensors.

8. The apparatus of any preceding claim, wherein the at least one sensor signal is generated while the body portion and/or the tissue is substantially not moving.

9. The apparatus of any preceding claim, further comprising a substantially planar housing portion containing the at least one first MI antenna, the housing portion having a first side and a second side, the at least one first MI antenna closer to the first side than to the second side, wherein the at least one sensor signal is indicative of whether the first side or the second side of the housing portion is closer to the body portion.

10. The apparatus of any preceding claim, wherein the at least one sensor signal is indicative of the presence and/or location of the cushion or is indicative of the at least one attribute of the cushion, the at least one sensor comprising at least one RFID sensor or at least one NFC sensor.

11. The apparatus of claim 10, wherein the at least one attribute comprises at least one of: a thickness, a compressibility, a dielectric constant.

12. A method comprising: wirelessly transmitting power from a power source to a device on or implanted within a recipient’s body, the device inductively coupled to the power source; while wirelessly transmitting the power from the power source to the device, generating information relevant to exposure of the recipient’s body to electric, magnetic, and/or electromagnetic fields generated by the power source; and in response to the information, adjusting the power transmitted from the power source to the device such that the electric, magnetic, and/or electromagnetic fields comply with a predetermined medical safety regulatory standard for exposure of the recipient’s body.

13. The method of claim 12, wherein the information comprises at least one of: a presence and/or location of a pad between the power source and the recipient’s body, at least one attribute of the pad between the power source and the recipient’s body, a clearance between a power-emitting antenna of the power source and the device, and an extent of the recipient’s body within a power transmission range of the power source.

14. The method of claim 13, wherein the device comprises an implanted portion of an acoustic prosthesis system positioned on a head of the recipient and the pad comprises a cushion upon which the head rests during said wirelessly transmitting the power

15. The method of any of claims 12 to 14, wherein said generating the information comprises receiving at least one sensor signal from at least one sensor of the power source.

16. The method of any of claims 12 to 15, wherein said wirelessly transmitting the power and said generating the information are performed using different timeslots.

17. The method of claim 16, wherein said wirelessly transmitting the power and said generating the information are performed using time division multiple access (TDMA).

18. A non-transitory computer readable storage medium having stored thereon a computer program that instructs a computer system to perform the method of any of claims 12 to 17.

19. An apparatus comprising: at least one first antenna coil configured to receive at least one electrical current, the at least one electrical current configured to flow through the at least one first antenna coil to transcutaneously transmit power to at least one second antenna coil of a device within or on a tissue portion of a recipient’s body; at least one sensor configured to generate at least one first signal indicative of a presence, type, and/or thickness of a cushion between the tissue portion of the recipient’s body and the at least one first antenna coil; and circuitry configured to adjust, in response to the at least one first signal, the at least one electrical current.

20. The apparatus of claim 19, wherein the circuitry is configured to adjust the at least one electrical current to maintain a transmitted power level transmitted by the at least one first antenna coil to be below a threshold level in compliance with a medical safety regulatory standard for electromagnetic exposure of the recipient’s body.

21. The apparatus of claim 19 or claim 20, wherein the at least one sensor is further configured to generate at least one second signal indicative of a presence, location, and/or orientation of the tissue portion of the recipient’s body and/or of another tissue portion of the recipient’s body, and the circuitry is configured to adjust the at least one electrical current in response to the at least one first signal and the at least one second signal.

22. The apparatus of any of claims 19 to 21, wherein the circuitry is configured to adjust the at least one electrical current in real-time in response to the at least one first signal.

23. The apparatus of any of claims 19 to 22, wherein the device is an implanted portion of an acoustic prosthesis system positioned on a skull surface of the recipient.

24. An apparatus comprising: a housing having a first surface and a second surface opposite to the first surface, the housing configured to be placed in either a first orientation with the first surface on an underlying support surface and the second surface in contact with a recipient or with a cushion beneath the recipient or a second orientation with the second surface on the underlying support surface and the first surface in contact with the recipient or with the cushion beneath the recipient; at least one power transmission coil within the housing, the at least one power transmission coil positioned closer to the second surface than to the first surface and configured to transmit power to a device on or within the recipient; a sensor on or within the housing, the sensor configured to generate a sensor signal indicative of whether the housing is in the first orientation or the second orientation; and circuitry within the housing and in electrical communication with the at least one power transmission coil, the circuitry configured to adjust, in response to the sensor signal, at least one electrical current flowing through the at least one power transmission coil.

25. The apparatus of claim 24, further comprising the cushion, the cushion in contact with the housing, wherein the device is implanted within a head of the recipient and the cushion is configured to be between the head and the housing in both the first orientation and the second orientation.

26. The apparatus of claim 24 or claim 25, wherein at least one power transmission coil comprises a plurality of substantially planar power transmission coils that are substantially parallel to one another and at least partially overlap one another.

27. The apparatus of any of claims 24 to 26, wherein the sensor is selected from the group consisting of: accelerometer; gyroscope; tilt sensor; inclinometer.

28. The apparatus of any of claims 24 to 27, further comprising at least one second sensor on or within the housing, the at least one second sensor configured to generate at least one second sensor signal indicative of a position and/or orientation of the recipient relative to the at least one power transmission coil.

29. The apparatus of claim 28, wherein the at least one second sensor signal is indicative of at least one of: a presence, location, minimum thickness, maximum thickness, compressibility, rigidity, and/or dielectric constant of the cushion, a clearance between the at least one power transmission coil and the recipient, and an extent of tissue of the recipient within a power transmission range of the at least one power transmission coil.

30. The apparatus of any of claims 24 to 29, wherein the circuitry is configured to adjust the at least one electrical current to be less than a predetermined threshold level corresponding to a maximum level in compliance with a predetermined medical safety regulatory standard for exposure of the recipient.