Federal University of Santa Catarina, Mechanical Engineering, Florianopolis, 88040-900, Brazil.
Naval Postgraduate School, Monterey, CA, 93943, USA.
Sci Rep. 2018 Mar 2;8(1):3920. doi: 10.1038/s41598-018-22219-7.
The presence of external elements is a major limitation of current hearing aids and cochlear implants, as they lead to discomfort and inconvenience. Totally implantable hearing devices have been proposed as a solution to mitigate these constraints, which has led to challenges in designing implantable sensors. This work presents a feasibility analysis of a MEMS piezoelectric accelerometer coupled to the ossicular chain as an alternative sensor. The main requirements of the sensor include small size, low internal noise, low power consumption, and large bandwidth. Different designs of MEMS piezoelectric accelerometers were modeled using Finite Element (FE) method, as well as optimized for high net charge sensitivity. The best design, a 2 × 2 mm annular configuration with a 500 nm thick Aluminum Nitride (AlN) layer was selected for fabrication. The prototype was characterized, and its charge sensitivity and spectral acceleration noise were found to be with good agreement to the FE model predictions. Weak coupling between a middle ear FE model and the prototype was considered, resulting in equivalent input noise (EIN) lower than 60 dB sound pressure level between 600 Hz and 10 kHz. These results are an encouraging proof of concept for the development of MEMS piezoelectric accelerometers as implantable sensors for hearing devices.
外部元件的存在是当前助听器和人工耳蜗的主要限制因素，因为它们会导致不适和不便。完全可植入的听力设备已被提议作为减轻这些限制的一种解决方案，这导致了在设计可植入传感器方面的挑战。本工作对作为替代传感器的与听骨链相连的 MEMS 压电加速度计进行了可行性分析。传感器的主要要求包括尺寸小、内部噪声低、功耗低和带宽大。使用有限元（FE）方法对不同设计的 MEMS 压电加速度计进行了建模，并针对高净电荷灵敏度进行了优化。选择了最佳设计，即具有 500nm 厚氮化铝（AlN）层的 2×2mm 环形配置进行制造。对原型进行了表征，其电荷灵敏度和频谱加速度噪声与 FE 模型预测非常吻合。考虑到中耳 FE 模型与原型之间的弱耦合，等效输入噪声（EIN）在 600Hz 至 10kHz 之间低于 60dB 声压级。这些结果为开发作为听力设备可植入传感器的 MEMS 压电加速度计提供了令人鼓舞的概念验证。
