This paper presents an ultralow power interface circuit for a fully implantable cochlear implant (FICI) system that stimulates the auditory nerves inside cochlea. The input sound is detected with a multifrequency piezoelectric (PZT) sensor array, is signal-processed through a front-end circuit module, and is delivered to the nerves through current stimulation in proportion to the sound level. The front-end unit reduces the power dissipation by combining amplification and compression of the sensor output through an ultralow power logarithmic amplifier. The amplified signal is envelope detected, and fed to a voltage-controlled current source as a reference for stimulation current generation. The single channel performance has been tested with a thin film pulsed-laser deposition (PLD) PZT sensor for sound levels between 60-and 100-dB sound pressure level (SPL). The proposed front-end signal conditioning unit, which can support different back-end stimulators, dissipates only 25.4 and 51.2 µW based on measurement, for 1-and 8-channel operation, respectively. This represents the lowest in the literature. The interface generates linear stimulation current of 110-430 µA for the given sound range. The single-channel and eight-channel stimulator consume 105 and 691 µW, respectively, for 110-µA biphasic stimulation current.Index Terms-Fully implantable cochlear implant (FICI), hearing loss, logarithmic amplifier (LA), neural stimulation, piezoelectric (PZT) sensor, ultralow power.
I. INTRODUCTIONA CCORDING to the World Health Organization (WHO), 360 million people have disabling hearing loss greater than 40-dB sound pressure level (SPL) as of 2017. The hearing loss can be mild, moderate, severe, or profound and leads to difficulty in hearing sounds that range from daily conversations to loud noises [1]. Conventional hearing aids can be used for
This paper presents the first acoustic experimental results of a MEMS based bulk piezoelectric transducer for use in fully implantable cochlear implants (FICI). For this purpose, the transducer was attached onto an acoustically vibrating membrane. Sensing and energy harvesting performances were measured using neural stimulation and rectifier circuits, respectively. The chip has a 150 Hz bandwidth around 1800 Hz resonance frequency that is suitable for mechanical filtering as a sensor. As an energy harvester, bulk piezoelectric transducer generated a rectified power of 16.25 μW with 2.47 VDC with 120 dB-A sound input at 1780 Hz. Among other MEMS acoustic energy harvesters in the literature, reported transducer has the highest power density (1.5 × 10 −3 W/cm 3 ) to our knowledge.
This paper presents design and fabrication of a MEMS-based thin film piezoelectric transducer to be placed on an eardrum for fully-implantable cochlear implant (FICI) applications. Resonating at a specific frequency within the hearing band, the transducer senses eardrum vibration and generates the required voltage output for the stimulating circuitry. Moreover, high sensitivity of the sensor, 391.9 mV/Pa @900 Hz, decreases the required power for neural stimulation. The transducer provides highest voltage output in the literature (200 mVpp @100 dB SPL) to our knowledge. A multi-frequency piezoelectric sensor, covering the daily acoustic band, is designed based on the test results and validated through FEA. The implemented system provides mechanical filtering, and mimics the natural operation of the cochlea. Herewith, the proposed sensor overcomes the challenges in FICI operations and demonstrates proof-of-concept for next generation FICIs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.