Feasible pickup from intact ossicular chain with floating piezoelectric microphone

Abstract

ObjectivesMany microphones have been developed to meet with the implantable requirement of totally implantable cochlear implant (TICI). However, a biocompatible one without destroying the intactness of the ossicular chain still remains under investigation. Such an implantable floating piezoelectric microphone (FPM) has been manufactured and shows an efficient electroacoustic performance in vitro test at our lab. We examined whether it pick up sensitively from the intact ossicular chain and postulated whether it be an optimal implantable one.MethodsAnimal controlled experiment: five adult cats (eight ears) were sacrificed as the model to test the electroacoustic performance of the FPM. Three groups were studied: (1) the experiment group (on malleus): the FPM glued onto the handle of the malleus of the intact ossicular chains; (2) negative control group (in vivo): the FPM only hung into the tympanic cavity; (3) positive control group (Hy-M30): a HiFi commercial microphone placed close to the site of the experiment ear. The testing speaker played pure tones orderly ranged from 0.25 to 8.0 kHz. The FPM inside the ear and the HiFi microphone simultaneously picked up acoustic vibration which recorded as .wav files to analyze.ResultsThe FPM transformed acoustic vibration sensitively and flatly as did the in vitro test across the frequencies above 2.0 kHz, whereas inefficiently below 1.0 kHz for its overloading mass. Although the HiFi microphone presented more efficiently than the FPM did, there was no significant difference at 3.0 kHz and 8.0 kHz.ConclusionsIt is feasible to develop such an implantable FPM for future TICIs and TIHAs system on condition that the improvement of Micro Electromechanical System and piezoelectric ceramic material technology would be applied to reduce its weight and minimize its size.

A New Floating Piezoelectric Microphone for Fully Implantable Cochlear Implants in Middle Ear

“…The anesthesia method is briefly described below, and it has been described in a previous study. 6,11 A combination of 20 mg/kg ketamine and 1.0 mg/kg xylazine was used to anesthetize the animals. For reduction of respiratory fluid secretion, atropine (0.5 mg intramuscularly) was also administered.…”

“…10 Based on piezoelectric ceramic materials and MEMS technology, an implantable middle-ear microphone, which was integrated with a low-noise preamplifier and encapsulated with a piece of thin titanium crust to form a miniature unibody structure, has been in use since 2001. 11 A fully implantable middle-ear implant typically uses an implantable sensor to detect ossicle mechanical motions, using the ear as a natural microphone. 9 Our team has been working on developing an implantable middle-ear system with a miniature piezoelectric microphone.…”

Sensing Devices for Detecting and Processing Acoustic Signals in Healthcare

“…Kang et al designed a biocompatible piezoelectric accelerometer using a ceramic bimorph element and an electronic chip enclosed in a titanium case with a total volume of 4.5 × 1 × 0.3 mm 3 and a mass equal to 38.4 mg. Tests were performed by gluing the device on the incus of a cat and measuring the acoustic stimuli [ 60 ]. The same design was tested by Gao et al with a finite element model that included a human middle ear [ 61 ].…”

Implantable microphones as an alternative to external microphones for cochlear implants

“…The frequency response curve of the piezoelectric microphone mirrored the standard external microphones but sensitivities were different (-38.7 dB re 1 V/Pa at 1,000 Hz and -1.5dB re 1V/Pa at 1,000Hz respectively). The same group developed a piezoelectric microphone implanted in cats and tested its sensitivity when placed on the malleus, and in comparison to an external microphone but also when hung in the tympanic cavity (Kang et al, 2012). Despite efforts to reduce the weight of the sensor, when attached to the malleus, the authors noticed a dramatic decrease in microphone sensitivity in the low frequencies, which they postulated was due to a mass-loading effect.…”