TR2023007135T2 - MEMS BASED COCHLEAR IMPLANT - Google Patents

Abstract

The present invention relates to a fully implantable device that mimics the natural hearing mechanism of the ear and produces auditory signals to stimulate the auditory nerves.

Description

DESCRIPTION MEMS-BASED COCHLEAR IMPLANT Technical Field of the Invention The invention is based on a fully implantable device that mimics the natural hearing mechanism of the ear and produces auditory signals to stimulate the auditory nerves. Prior Art About the MEMS-Based Invention (Prior Art) Human peripheral hearing system (FIG. 1) It consists of the outer ear (auricle), middle ear (ear canal, eardrum (l), ossicles) and inner ear (cochlea). The human hearing range varies between acoustic waves from 20 Hz to 20 kHz. The pinna and ear canal (FIGURE 1) amplify incoming sound waves according to the incoming acoustic wave frequency. The eardrum (1) is connected to the ossicles (hammer, incus and stirrup) in the middle ear, which further strengthen the sound vibration and transfer these vibrations to the oval window (3) of the cochlea (4). The movement of the stirrup stimulates the inner ear, leading to an electrochemical activity associated with the cochlear hair cells that stimulate the auditory nerves [l] located on the basilar membrane. Sensorineural hearing impairment results from irreversible damage to cochlear hair cells, which become dysfunctional/deficient. Cochlear implants (CIs) are used to bypass damaged hair cells and directly stimulate the auditory nerve via a cochlear electrode, opening a pathway for treating sensorineural hearing loss. In a typical cochlear implant system, external and internal components form a complete operating system/device. External components include a microphone, an audio processor, a battery, and a wireless transmitter. Internal components include a receiver and cochlear electrode. The microphone collects acoustic information from the environment and the captured acoustic waves are processed and transmitted to the cochlear electrode through a receiver placed on the back of the head, behind the ear. These devices suffer from the need for daily/frequent battery charging/replacement, risk of damage to external components, and aesthetic concerns, as well as psychological effects on patients. Exposing external components to the outside world can easily cause damage from impact and water. On the other hand, hearing impairment is a disease that affects the quality of life by limiting the patient's social interaction with the environment. This situation may also negatively affect psychological health in young patients. The biggest disadvantage of traditional CIs [2] is that they replace the entire natural hearing mechanism with electronic hearing, although most parts of the middle ear are functional. Additionally, power-hungry units such as RF transceivers and processors cause limitations in uninterrupted operation due to battery capacity. To date, several devices have been noted to replace the microphone component of cochlear implants to reduce the need for batteries. It describes resonator bars as a vibration detector with a resonant frequency resonator. This device, which is used in traditional cochlear implants, does not solve the energy consumption concern. In the document numbered US 3712962 A, an implantable piezoelectric hearing device is reported, in which a single piezoelectric transducer is placed between the bones in the middle ear to detect incoming sound and generate signals to stimulate the auditory system. The signal produced is not large enough for direct stimulation of the electrodes without electronics. On the other hand, electronics and the operation of such electronics are not specified. The same concern is the single elliptical thin contact to convert the ossicle vibration into electrical signal: the single elliptical thin element produces low signal voltage, which is not enough to stimulate the auditory nerve without electronics. Document US 10022541 B2 discloses a low power electronic device for cochlear implant. The system, which includes sensing, processing, and stimulation circuits, is used to interface the single piezoelectric transducer in the cochlea and stimulate the electrodes. The need for batteries is inevitable and providing different power sources is problematic, while system operation is a matter of serious concern. Microfabricated piezoelectric transducers are widely used to convert mechanical vibrations into electrical field [3] and offer solutions for cochlear implants (CIs) as a sound sensor and also as a power source due to their small size and relatively high energy density. By taking advantage of this ability, micro piezoelectric transducers can be used to (i) exploit the functional parts of the middle ear and mimic hair cells in the cochlea (4) via electrodes and (ii) harvest energy from vibrations in the auditory system. If MEMS-based multi-frequency transducers are used to detect and mechanically filter acoustic signals (U.S. Pat. No. 9,630,007 (as in point 1 above)) external microphone, transceiver, and electronic filtering circuits—all of which require external components and require a power supply to operate. The cause can be eliminated. Therefore, this can lead to the elimination of bulky external components and a significant reduction in power demand, which can be achieved through the MEMS-based energy harvesting converter. Now it is a development of the US patent application number 9,630,007, titled "Energy harvesting cochlear implant" by H. Külah et al. In this patent, the basis of a fully implantable cochlear implant is given. Purposes of the Invention and Brief Description The present invention relates to the MEMS Based Cochlear Implant system that meets the above-mentioned requirements, eliminates all disadvantages and provides some new advantages. Since then, research work on these Principles (mentioned in the Prior Art) has progressed towards a significantly improved concept for FICI. These improvements necessitate a new patent application for this significantly improved concept; (i) separate transducers for energy harvesting and sound detection, (ii) sound processing and excitation via ultra-low power interface circuitry rather than direct excitation by the transducer, (iii) wireless charging, (iv) vacuum packaging of transducers, (v) a smart charging via a standard earplug via a simple tone generator app running on the phone. The present invention provides a fully implantable cochlear implant system (FICI) consisting of a multi-frequency acoustic transducer and an energy harvesting system using the piezoelectric effect. All components of the FICI system are applied to the middle and inner ear. The acoustic transducer and energy harvester stack are respectively mounted on one of the ossicles on the ossicular chain (2) or the eardrum (l) to detect incoming sound and extract acoustic energy. The electronic components that form the interface between the acoustic sensor and the energy harvester are required to create the impulse necessary to stimulate the relevant auditory nerves through the electrode implanted in the cochlea (4) and to charge the battery. The transducers are manufactured and packaged using Micro-Electro-Mechanical Systems (MEMS) manufacturing techniques and implanted into the middle ear, all coated with a biocompatible material. A wireless data transfer unit for patient mounting and system diagnostics is also included. The invention guarantees a high-quality electronic hearing aid by mimicking the natural hearing mechanism and, as a result, eliminates the extracorporeal components of a conventional cochlear implant and the batteries that need to be changed frequently. The system includes a transducer and an energy harvester that utilize piezoelectricity to generate the signal of acoustic waves and extract the incoming energy to be implanted in the middle ear on the eardrum or ossicles. The device uses electronic interface to detect and process signals to electrically stimulate the relevant auditory nerves corresponding to the selected sound frequency. The implanted rechargeable battery provides the required power where the energy harvesting system, which includes a piezoelectric collector and interface circuit, charges the battery and provides a regulated supply voltage. The device also numbs the RF coils and associated electronics for insertion and insertion into the patient as well as transferring power to the battery as a backup for the energy harvesting system. The RF coil and an interface circuit are implanted under the skin alongside the rechargeable battery. The invention completely mimics the natural functioning of an auditory system, thus eliminating the use of external microphones, sound processors and transmitters currently used in traditional cochlear implants. Explanations of Figures Explaining the Invention The figures and their explanations used to better explain the MEMS Based Cochlear Implant developed with this invention are as follows: FIGURE 1 is a schematic view of the human ear; FIG. 2 shows in detail a beam of the converter or energy harvester according to the invention. Figure 3 is a partial view of a converter according to the invention and shows exemplary beams in detail. FIG. 4 shows another possible transducer according to the invention. FIG. 5 shows a 3D view of the stacked transducer according to the invention and the substrate to be mounted. FIG. 6 shows a schematic of the sandblasted RF coil and battery associated with interface circuits according to the invention. FIG. 7A is a schematic view of the stacked converter and collector built on the stirrup and ossicle leg, and FIG. 7b is the view built on the anvil. Reference Numbers Each of the parts in the figures is numbered and the references for each number are listed below. l Eardrum 2 Ossicular Chain 3 Oval Window 4 Cochlea Round Window Piezoelectric part 21 Cantilever Beam 22 Tip Mass 33 Base Detailed Description of the Invention To better explain the MEMS Based Cochlear Implant developed with this invention, its details are given below. The present invention discloses a fully self-powered implantable device to electrically stimulate auditory nerves located in the cochlea (4) using a cochlear electrode to correct impaired hearing. The piezoelectric effect is used to convert mechanical vibrations into electrical fields for both sound detection and energy harvesting purposes. The sound transducer of the invention is implanted in the middle ear on the eardrum or ossicular chain (2) to detect the frequency of vibrations of incoming sound pressure waves according to its mechanical frequency selective structure. This invention uses ultra-low power interface electronics to amplify and process the signals generated through the converter. The amplitude of the calibrated signals is transferred to the electrodes according to the cochlear frequency map to stimulate the auditory nerves. The MEMS fabricated piezoelectric collector is stacked with the sound transducer to generate the required power from the vibrations of the middle ear organelles (2). In the present invention, an autonomous interface electronics manages the extracted energy and provides regulated sources for the stimulation electronics. The interface electronics architecture includes passive and active circuits with two storage elements containing a capacitor and a rechargeable battery. The passive energy extraction circuit can charge the storage element without initial energy in either reservoir. The circuit manages the charging flow to the storage elements to ensure autonomous operation and controls the activation of other electronic devices through start-up circuits. A rechargeable battery and interface electronics associated with a coil are implanted under the skin. This coil is attached to the patient via the wearable external coil as a backup/support for the energy harvesting system and is used as a wireless transfer to recharge the battery. Energy Harvesting: One of the key features of FICI is its new battery charging methodology, where the device harvests energy through vibration produced as a result of sound waves fed by a simple earplug connected to a tone generator. This could be a simple app running on a smartphone or similar mobile device, or via ambient sound. Battery recharging is accomplished through a summing transducer based on the MEMS piezoelectric cantilever in FIG. 2 and a power conditioning interface circuit that extracts energy from the transducer and directs the extracted energy to charge the storage element to power the audio processing and exciter IC. The autonomous power unit offers a significant improvement in the long-term use of implants with ultra-low power and efficient electronics. The summation transducer is optionally vacuum packaged and is a high quality factor cantilever die that does not interfere with the frequency bands of the acoustic sensor, preferably operating in acoustic bands with specific resonance frequencies. The piezoelectric energy collector will be placed in a position where vibrations resulting from sound waves can be detected; in the middle ear cavity connected to one or more hearing elements, such as the umbilicus, ossicles, or eardrum; or under the skin tissue of the ear canal, and the ear canal is amplified. The tympanic membrane (ear drum (1)) vibrates with the sound waves coming from the ear canal (hearing canal). The ear canal and the ear canal amplify the incoming sound waves according to the incoming wave frequency. The piezoelectric collector design and mounting point are minimum on the hearing elements. It has a damping effect and is designed at the ear canal amplification frequency to detect the incoming energy at the maximum level. The power conditioning IC [4] is an autonomous, self-adaptive system for extracting acoustic energy via a piezoelectric energy harvester to power neural stimulation electronics. The integrated circuit provides a practical MEMS piezoelectric collection system and is compact enough to be implanted in limited space within the middle ear or its immediate surroundings. The IC amplifies and manages the output power and provides regulated power supply to the subunits of the system. The energy harvesting unit is to meet the power demand of this ultra-low power cochlear implant. However, since an implanted device cannot be replaced frequently, a backup solution for the power supply is integrated into the FICI device. In addition to the energy harvester, a wireless power transfer unit is included in the package to charge the battery in cases where the performance of the energy harvester cannot meet the consumption of the FICI package. For this replacement charger, refer to the "Wireless power and data transmission" section. Sound Detection and Stimulation: FICI uses frequency-selective piezoelectric cantilevers, similar to cochlear hair cells, to generate signals for neural stimulation. This eliminates most power-hungry electronics, such as microphones, RF transceiver, and active bandpass filters, while using healthy parts of the middle ear. In this way, FICI operates at low power because it does not require uninterrupted RF transmission and a microphone. Additionally, piezoelectric cantilevers with bandpass properties simplify electronics. Acoustic Sensor: FICI's sound detection unit; The acoustic sensor/transducer is a series of piezoelectric cantilevers placed on the eardrum or ossicles (FIG. 3). Piezoelectric consoles convert acoustic vibration into the electrical signal required for neural stimulation in specific frequency channels. The present invention proposes a feasible solution to challenges such as volume and mass limitations, frequency range and power requirements. The transducer based on mechanical sensors has been compressed to cover the specific frequency range of the human hearing band, as all the sensing devices (multi-frequency piezoelectric transducers) can be assembled on a single layer (FIG. 4) or stacked layers (FIG. 5). Micro consoles are placed at linear and logarithmic intervals according to the distribution of daily sound waves in the hearing band. They provide mechanical filtering and mimic the natural functioning of the cochlea, which is an important innovation of this invention. Sound Processing and stimulation interface circuit: Low-power signal conditioning interface circuit is required to realize the FICI system. In this invention, the fully integrated interface circuit with significantly reduced power dissipation (<500uW) compared to traditional CIs (10mW-40mW) processes signals from piezoelectric consoles at different frequencies and continuously transmits signals to the cochlea (4) according to the power level and frequency of the acoustic input signal. It stimulates the auditory neurons inside. Sensor outputs are amplified, intermittently compressed and rectified into AC current waveforms. The rectified signals are de-enveloped and selectively sampled as a reference for the stimulation current generator equipped with patient attachment functionality. The adjusted biphasic stimulation current is delivered to auditory neurons while protecting them from overload damage. Wireless power and data transmission: The battery implanted under the skin is recharged by an acoustic energy harvesting system. Wireless power transfer interface circuitry is included to provide a backup and supplementary source to the energy harvester. An RF coil placed subcutaneously next to the battery (FIG. 6) and an external RF coil aligned to the implanted one are used not only to charge the battery in cases where the collected energy is not sufficient, but also to transfer data for insertion into the patient and diagnosis. It should be clearly noted that this charging system differs from the traditional cochlear implant power delivery unit, which requires continuous RF power transmission to operate, whereas in this charging unit introduced for FICI, RF wireless transmission will be activated only for a short period of time as a complementary source to charge the battery. Charging is done with inductively combined RF coils. With special precautions without the use of magnets, transmission efficiency and the effect of misalignment between the transmitter and receiver units during charging are minimized. These chokes facilitate high power transfer from lmW to 50mW and 4Mb/s high-speed data transmission as well as low space occupation. Data transmission: initial and long-term calibration of any implanted device; needs to be monitored and recalibrated. For this purpose, a reliable data transmission unit is vital. The FICI then includes a data transceiver unit with the following functions; I. Importing data from outside for insertion into the patient, ii. Back telemetry to verify received data by transferring data from inside to outside. This is achieved by the same inductively coupled RF coils or other data transfer channels. Integration: For effective implantation and long operating time of FICI units with minimum space requirement, effective integration and connection of parts is very important. To this end, the energy harvesting and noise detector chips will be 3D integrated to form the compact transducer stack (FIG. 5). This stack is hermetically packaged (can also be vacuum packaged) and interconnected with power and signal conditioning CMOS interface circuits via a flexible substrate. By the nature of the invention, all packaging of FICI units is biocompatible to ensure implantation. In summary; A collection and fully implantable cochlear implant system is proposed to provide electrical stimulation signals; where the system includes the following; 0 Frequency selective piezoelectric cantilevers for generating signals for neural stimulation, o An acoustic transducer comprising a plurality of cantilever beams (21) and a piezoelectric part (20) connected to each of the cantilever beams (21); where each of the plurality of cantilever beams (21) has a different predetermined natural frequency from each other, corresponding to the 200Hz-10Khz frequency band of the incoming acoustic waves, 0 Autonomous circuit with passive and active circuits containing two storage elements containing a capacitor and a rechargeable battery. an interface electronics manages the energy extracted therein and provides regulated sources for the stimulation electronics and is configured to couple to the acoustic transducer and receive and amplify the signals of the plurality of cantilever beams 21; and processing circuits for stimulating the relevant auditory nerves via cochlear electrodes, o Power conditioning IC (interface circuit) [4], which is an autonomous, self-adaptive system for extracting acoustic energy through the piezoelectric energy harvester to power the neural stimulation electronics, o Present in the hearing system an energy harvesting system that includes a piezoelectric console to extract incoming acoustic energy, 0 Wireless power transfer interface circuit used to have a backup and supporting source to the energy harvester, 0 Here the rechargeable battery placed under the skin is recharged by the acoustic energy harvesting system. 0 At least one RF coil used as a wireless transfer for attachment to the patient via a wearable external coil as a backup/support for the energy harvesting system and for recharging the battery. Other aspects of the invention; It is a system in which each of the console beams (21) contains a free end and a fixed end; The piezoelectric part (20) is placed at the fixed end; Each of the plurality of cantilever beams (21) can convert incoming acoustic waves into voltage outputs via the piezoelectric element (20). System wherein the energy harvesting system is configured to charge the rechargeable battery, wherein the energy harvesting system includes an interface circuit configured to couple the energy extracted from said piezoelectric to the MEMS fabricated piezoelectric harvester and manage the energy to provide regulated power supply, the energy harvesting system, the middle ear Cochlear implant, which further comprises: at least one flexible biocompatible base on which said transducer, interface electronics and cochlear electrode are built. Said transducer, mounted on said flexible biocompatible base, is placed on a vibrating element of an auditory system that vibrates under the influence of incident acoustic waves. The flexible biocompatible base is shaped with a suitable serpentine electrode using a conductive metal for signal transfer between the transducers, interface electronics, and the cochlear electrode. A cochlear implant wherein each of a plurality of cantilever beams 21 is designed to predetermine the natural frequency; where the low frequency cantilever beam (21) includes a tip mass (22) at the free end and the high frequency cantilever beams (21) are independent of the tip mass (22). Here, each end mass may contain a rectangular structure of different lengths. It is a cochlear implant, where the number of cantilever beams (21) can vary between 1 and 30 or as much as is within the volume and mass limitation of the transducer. It is a cochlear implant, where the transducer and energy harvester also include the biocompatible, hermetic coating and biocompatible coating of the entire system. Cochlear implant, referring to FIG. 7a and FIG. 7b, wherein transducers are implanted into the middle ear; It is preferably docked between one of the ossicular legs and the umbo or one of the ossicular legs and the stapes and any that transmit vibration. It is a cochlear implant, where it also includes wireless data transfer, including the implanted RF coil and connected electronics for wearing the system and even transferring power to the battery. Transducers are clamped between the umbo and ossicular chain (4) to detect the frequency of vibrations of incoming sound pressure waves. It contains an implanted RF coil and associated electronics for wireless data transfer, system docking, and even power transfer to the battery. The piezoelectric part (20) is placed on the fixed end. Each end mass may include a rectangular structure of different lengths. The energy harvesting system uses the vibration energy present in the middle ear hearing system. The system is applied to the middle and inner ear. Interface electronics associated with a rechargeable battery and a coil are implanted subcutaneously. The acoustic transducer and energy harvester stack is mounted on one of the ossicles on the ossicular chain (2) or the eardrum (l) to detect incoming sound and extract acoustic energy. All transducers are coated with a biocompatible material. It is an energy harvesting system and includes a wireless power transfer unit included in the package to recharge the battery in cases where the performance of the energy harvester cannot meet the consumption of the FICI package. An RF coil placed subcutaneously next to the battery and the external RF coil aligned to the implanted one are used not only to charge the battery in cases where the collected energy is not sufficient, but also to transfer data for patient placement and diagnosis.