Multichannel multimodal piezoelectric middle ear implant concept based on MEMS technology for next-generation fully implantable cochlear implant applications

This paper introduces a unique multimode, multichannel piezoelectric vibration sensor for the next-generation fully implantable cochlear implant (FICI) systems. The sensor, which can be implanted on the middle ear chain to collect and filter the ambient sound in eight frequency bands, comprises an array of 4 M-shape multimode and 11 single cantilevers. Finite element (FE) analysis indicates a 2.05-fold improvement in capturing frequency information for the multimodal sensor compared to its single-mode counterpart. Under an acoustic excitation at 100 dB SPL, the sensor, mounted on an artificial tympanic membrane, yielded a peak output voltage of 546.16 mVpp and a peak sensitivity of 285.28 mVpp/Pa at 1613 Hz. The extrapolated acoustic results indicated a dynamic frequency range between 300 Hz and 6 kHz, even at 30 dB SPL. Furthermore, a lightweight titanium coupler, employing a two-sided clipping structure with a maximum wall thickness of 70 μm, is micromachined for surgical attachment of the transducer to the middle ear chain. A commercial accelerometer, implanted on the incus short process (SP) of a cadaver using the titanium coupler, successfully recorded 0.1 g for 100 dB SPL at 500 Hz, revealing the potential feasibility of the coupler for vibration sensor implantation. Moreover, the presented anatomically accurate FE model of the middle ear, exhibiting a high correlation coefficient (R²) of 0.97 with the cadaveric experiment, suggests an efficient numerical approach for evaluating the implantation of middle ear prostheses. In this regard, the study holds great promise for clinical application in the field of implantable hearing aids.