To validate an intracochlear piezoelectric sensor for its ability to detect intracochlear pressure and function as a microphone for a fully implantable cochlear implant.
A polyvinylidene fluoride (PVDF) piezoelectric pressure sensor was inserted into a human fresh cadaveric round window at varying depths. An external sound pressure stimulus was applied to the external auditory canal (EAC). EAC pressure, stapes velocity, and piezoelectric sensor voltage output were recorded.
The PVDF sensor was able to detect the intracochlear sound pressure response to an acoustic input to the EAC. The frequency response of the pressure measured with the intracochlear sensor was similar to that of the pressure at the EAC, with the expected phase delay of the middle ear transmission. The magnitude of the response increased and smoothened with respect to frequency as the sensor was inserted more deeply into the scala tympani. Artifact measurements, made with the sensor in air near the round window, showed flat frequency response in both magnitude and phase, which were distinct from those measured when the sensor was inserted in the round window.
This study describes a novel method of measuring intracochlear pressure for an otologic microphone composed of a piezoelectric polymer, and demonstrates feasibility. Our next goal is to improve device sensitivity and bandwidth. Our long-term objective is to imbed the piezoelectric sensor within a conventional cochlear implant electrode, to enable a device to both measure intracochlear sound pressure and deliver electrical stimulus to the cochlea, for a fully implantable cochlear implant.
*Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston
†Harvard Program in Speech and Hearing Bioscience and Technology, Cambridge, Massachusetts
‡Department of Electrical Engineering
§Department of Otolaryngology Head and Neck Surgery, Columbia University Medical Center
¶Department of Biomedical Engineering, Columbia University, New York City, New York
||Korea Advanced Institute of Science and Technology, Daejon, South Korea
Address correspondence and reprint requests to Francis (Pete) X. Creighton, M.D., Department of Otolaryngology, Harvard Medical School, Massachusetts Eye and Ear, ENT Education Office, 243 Charles St, Boston, MA 02114; E-mail: firstname.lastname@example.org
This article is associated with a poster presentation, “Investigation of Piezoelectric Sensors for a Middle Ear Microphone,” to be presented at the American Neurotological Society Meeting as The Combined Otolaryngology Sections Meeting in Chicago May of 2016.
Dr. Nakajima has a gift from Advanced Bionics to support parts of this research.
The other authors report no conflicts of interest.