The invention relates to MEMS-Based Cochlear Implant which is on a fully implantable device for mimicking the natural hearing mechanism of the ear and producing auditory signals to stimulate the auditory nerves.
Human peripheral auditory system (
Sensorineural hearing impairment is caused from irreversible damage to cochlear hair cells rendering them non-functional/missing. Cochlear implants (CIs) are used to bypass the damaged hair cells and directly stimulate the auditory nerve by means of a cochlear electrode, thus opening a way for the treatment of sensorineural hearing loss. In a typical cochlear implant system, external and internal components form a complete working system/device. External components comprise a microphone, a sound processor, a battery and a wireless emitter.
Internal components comprise a receiver and the cochlear electrode. The microphone collects the acoustic information in the environment and the captured acoustic waves are processed and transmitted to the cochlear electrode via a receiver implanted at the rear head behind the ear.
These devices suffer from daily/frequent battery recharge/replacement requirement, damage risk of external components, and aesthetic concerns combined with psychological effects on the patients. The exposure of the external components to the outer world can lead to a damage easily due to impact and water. On the other hand, hearing impairment is a disease affecting the patient's quality of life by limiting the social interaction of him/her with the environment. For young patients this situation may also have adverse effects on the psychological health.
The major drawback of conventional CIs is that, they replace the entire natural hearing mechanism with electronic hearing, even though most parts of the middle ear are operational. Besides, the power-hungry units such as RF transceiver and processors cause limitations in continuous operation due to battery capacity.
Up to now, various devices have been recorded to substitute the microphone component of cochlear implants to reduce the battery need of them.
US 2003/0012390 A1 describes a resonator bars as a vibration detector with distinct resonance frequency resonator corresponding to their thickness with piezoelectric. This device used in conventional cochlear implants, however it doesn't provide a solution for energy consumption concerns.
An implantable piezoelectric hearing aid was reported in U.S. Pat. No. 3,712,962 A, where a single piezoelectric transducer is placed on middle ear between bones to sense incoming sound and generate signals to stimulate the auditory system. The generated signal is not large enough for direct stimulation of electrodes without electronics. On the other hand, the electronics and powering of such electronics was not specified.
The same concern applies to US. Pub. No. 20050113633 using single elliptic thin piezoelectric element to convert ossicles vibration to electrical signal. Previous argument: single elliptic thin element produces low signal voltage that is not enough to stimulate the auditory nerve without electronics.
U.S. Ser. No. 10/022,541 B2 disclosed a low power electronic device for cochlear implant. The system including sensing, processing, and stimulation circuits is utilized to interface single piezoelectric transducer and stimulate electrodes in cochlea. The need of a battery is inevitable and providing different power supplies is problematic, while powering up the system is matter of serious concern.
Micro-fabricated piezoelectric transducers are widely used to convert mechanical vibrations to electrical domain and they offer solutions for cochlear implants (CIs) as a sound sensor and also power source due to its small size and relatively high energy density. Utilizing this capability, micro piezoelectric transducers can be used for (i) exploiting the functional parts of the middle ear and mimicking the hair cells in the cochlea (4) via electrodes and (ii) harvesting energy from vibrations in the hearing system. An example of micro-fabricated piezoelectric transducers being used to conert mechanical vibrations to electrical domain is given in L. Beker, Ö. Zorlu, N. Göksu, and H. Külah, “Stimulating auditory nerve with MEMS harvesters for fully implantable and self-powered cochlear implants,” in 2013 Transducers Eurosensors XXVII: The 17th International Conference on Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS EUROSENSORS XXVII), 2013, pp. 1663-1666.
If MEMS-based multi-frequency transducers are used for sensing and mechanical filtering of the acoustic signals, (U.S. Pat. No. 9,630,007 (as in point 1 above)), external microphone, transceiver and electronic filtering circuitry—all of which necessitate external components and result in a power-hungry operation—can be eliminated. Therefore, this can lead to elimination of bulky external components and significant reduction of power demand which can be supplied via MEMS based energy harvesting transducer.
This invention is an improvement over the patent of H. Külah, et al., “Energy harvesting cochlear implant” U.S. patent application Ser. No. 14/355,213, filed Dec. 2, 2011, now U.S. Pat. No. 9,630,007. In that patent, the fundamental of the fully implantable cochlear implant is introduced.
The present invention is related to a MEMS-Based Cochlear Implant system that meets the requirements mentioned above, eliminates all of the disadvantages and brings about some new advantages.
Research studies conducted over those Fundamentals (mentioned in Prior Art About The Invention) since then, advanced to a significantly improved concept for the FICI. These improvements necessitates filing of a new patent for this significantly improved concept, which are briefly; (i) separate transducers for energy harvesting and sound sensing, (ii) sound processing and stimulation by ultra-low power interface circuit instead of direct stimulation by transducer, (iii) wireless recharging, (iv) vacuum packaging of transducers, (v) recharging through a standard earplug via a simple tone generator application running on a smart phone.
This invention introduces a fully implantable cochlear implant system (FICI) composed of the multi-frequency acoustic transducer and an energy harvesting system using piezoelectric effect. All components of the FICI system are implemented in middle and inner ear. The stack of acoustic transducer and energy harvester are mounted on one of the ossicles on the ossicular chain (2) or the tympanic membrane (1) to sense incoming sound and extract acoustic energy, respectively. Electronics are necessary to interface acoustic sensor and energy harvester in order to generate the required impulse for the stimulation of the relevant auditory nerves via implanted electrode in cochlea (4) and recharge the battery. Transducers are fabricated and packaged using Micro-Electro-Mechanical Systems (MEMS) fabrication techniques and implanted into middle ear, all coated with a biocompatible material. A wireless data transfer unit is also included for patient fitting and system diagnosis. The invention promises high quality electronic hearing aid by help of mimicking the natural hearing mechanism and eventually eliminates components of a conventional cochlear implant outside the body and batteries to be frequently replaced.
The system includes transducer and energy harvester making use of piezoelectricity to generate signal of acoustic waves and extract incoming energy which is to be implanted to middle ear on tympanic membrane or ossicles. The device utilizes interface electronic to sense and process signals for electrically stimulating the relevant auditory nerves corresponding to selected frequency of sound. Implanted rechargeable battery provides required power where energy harvesting system including piezoelectric harvester and interface circuit recharge the battery and provide regulated supply voltage. The device further compromises RF coils and related electronics for patient fitting and diagnosis as well as power transfer to the battery as a support for energy harvesting system. The RF coil and an interface circuit are implanted under the skin beside the rechargeable battery. The invention in complete mimics the natural operation of an auditory system, therefore eliminates the use of microphone, sound processor, and transmitter that are currently used externally in conventional cochlear implants.
The figures used to better explain a MEMS-Based Cochlear Implant developed with this invention and their descriptions are as follows:
The parts in the FIGS. have each been numbered and the references of each number has been listed below.
To better explain MEMS-Based Cochlear Implant developed with this invention, the details are as presented below.
With reference to
Information about Major Components:
Energy Harvesting:
One of the most important features of the FICI is its novel battery charging methodology by which the device harvests energy through the vibration generated as a result of sound waves fed by a simple earplug connected to a tone generator. This can be a simple application running on a smartphone or a similar mobile device, or through ambient sound. Battery recharging is realized through a harvesting transducer based on MEMS piezoelectric cantilever
A piezoelectric energy harvester is to be placed to a location that the vibrations due to sound waves can be detected; either in the middle ear cavity connected to one or more hearing elements such as umbo, ossicles or ear drum; or under the skin tissue of ear canal. The goal is to have high acoustic energy (40-90 dB SPL) and utilize ear canal amplification effect. The eardrum (Tympanic membrane (1)) vibrates with the sound waves coming through the ear channel (auditory canal). Pinna and auditory canal amplifies the incoming sound waves according to the incoming wave frequency. The piezoelectric harvester design and mounting point have minimum damping effect of on hearing elements and percieve maximum incoming energy by designing at ear canal amplification frequency.
Power conditioning IC is an autonomous self-adaptive system to extract acoustic energy via piezoelectric energy harvester for supplying power to neural stimulation electronics. Integrated circuit provides practical MEMS piezoelectric harvesting system and is compact enough to be implantable in the limited area within middle ear or its close periphery. The IC boosts and manages extracted power and provides regulated power supply to sub-units of the system. An example of a power conditioning IC is given in S. Chamanian, H. Ulu{tilde under (s)}an, A. Koyuncuoğlu, A. Muhtaroğlu and H. Külah, “An Adaptable Interface Circuit With Multistage Energy Extraction for Low-Power Piezoelectric Energy Harvesting MEMS,” IEEE Transactions on Power Electronics, vol. 34, no. 3, pp. 2739-2747, March 2019. doi: 10.1109/TPEL.2018.2841510.
Energy harvesting unit is for fulfilling the power demand of this ultra-low power cochlear implant. However, as an implanted device cannot be replaced frequently, a back-up solution is integrated to the FICI device for power supply. In addition to energy harvester, a wireless power transfer unit is included in the package for recharging the battery, whenever the performance of energy harvester cannot cover the consumption of FICI package. Refer to “Wireless power and data transmission” section for this back-up recharging unit.
Sound Sensing and Stimulation:
The FICI uses frequency selective piezoelectric cantilevers, in a similar way to the cochlear hair cells, to generate the signals for neural stimulation. This eliminates most of the power-hungry electronics, such as microphones, RF transceiver, and active band pass filters, while utilizing the healthy portions of the middle ear. By this way, the FICI operates at low power, as it does not require continuous RF transmission and microphone. Also, the piezoelectric cantilevers with band-pass characteristics simplify the electronics.
Acoustic Sensor:
FICI's sound detection unit: acoustic sensor/transducer is an array of piezoelectric cantilevers (
This invention proposes a feasible solution to the challenges such as volume and mass limitations, frequency range, and power requirements. The transducer based on mechanical sensors is compacted since all sensing devices (multi-frequency piezoelectric transducers) can be gathered either on a single layer (
Sound Processing and Stimulation Interface Circuit:
Low-powered signal conditioning interface circuit is required to accomplish the FICI system. In this invention, fully integrated interface circuit, with substantially reduced power dissipation (<500 μW) compared to conventional CIs (10 mW-40 mW), processes signals from the piezoelectric cantilevers with different frequencies and stimulates the auditory neurons inside cochlea (4) consistently according to the power level and frequency of the acoustic input signal.
The sensor outputs are amplified, range-compressed into AC current waveforms and rectified. The envelopes of the rectified signals are extracted and are selectively sampled as a reference for the stimulation current generator equipped with patient fitting function. Adjusted biphasic stimulation current is delivered to the auditory neurons while protecting them from excess charge damage.
Wireless Power and Data Transmission:
The battery implanted under the skin is recharged by an acoustic energy harvesting system. In order to have a back-up and a supporting source to the energy harvester, wireless power transmission interface circuit is included. An RF coil placed next to the battery under the skin (
The charging operation is done with inductively coupled RF coils. The efficiency of the transmission, and effect of misalignment between transmitter and receiver units during charging is minimized with specific measures without using any magnets. These coils facilitate high power transfer in range of 1 mW up to 50 mW and high-speed data transmission 4 Mb/s as well as low area occupation.
Data Transmission:
Any implanted device is required to be calibrated initially, and in the long term; monitored and recalibrated. For this purpose, a reliable data transmission unit is vital. Then, FICI includes a data transceiver unit with the following functions:
Integration:
For the effective implantation and long operation time of FICI units with minimum space requirement, effective integration and connection of the parts is crucial. For this purpose, energy harvesting and sound detector chips will be 3D integrated to form compact transducer stack (
As a summary: a harvesting and fully implantable cochlear implant system for providing electrical stimulation signals is proposed; where the system comprising:
Other Aspects of the Invention:
This application is the national phase entry of International Application No. PCT/TR2020/051317, filed on Dec. 17, 2020, the entire contents of which are incorporated herein by reference.
Filing Document | Filing Date | Country | Kind |
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PCT/TR2020/051317 | 12/17/2020 | WO |