耳蜗腔与压电薄膜助听器件的流-固耦合特征与模型

Combined electric and acoustic stimulation (EAS) of the inner ear and totally implantable cochlear prostheses have recently received wide attention for their potential benefits in hearing rehabilitation, MEMS devices based on piezoelectric thin film are paramount candidates for these two applications for their capability of either generating or picking up acoustic waves in inner ear. But the effects of narrow cochlear duct and perilymph in it on the performance of the thin-film devices have not been investigated, which slow down the research and optimal design of these MEMS devices. We will investigate this effect through both experiments and finite element modeling in this project. Specifically it includes the following parts: first, measuring the added mass and damping effects from perilymph in both free boundary conditions or constrained boundary conditions in a self-developed experimental environment; second, extracting the basic assumptions and boundary conditions from the realistic solid-fluid coupled situation to simplify the basic partial differential equations; third, solving the partial differential equations by finite element method; finally, verifying and modifying the basic assumptions and boundary conditions by comparing the experimental and simulated results to optimize the solid-fluid coupled finite element model. This solid-fluid coupled finite element model will provide important platform and reference for the following research and optimization design of the intra-cochlear MEMS devices based on piezoelectric thin film.

混合植入式助听器和全植入人工耳蜗是当前听力康复领域的热点方向，基于压电薄膜的微机电系统（MEMS）是它们在内耳产生音波或拾取音波的重要器件。而狭小的耳蜗腔与其中的淋巴液对薄膜型器件的影响至今没有系统的研究与结论，本项目计划通过实验测量与建模结合的方式针对产生影响的关键因素及作用机理进行研究。具体内容包括：第一、搭建压电薄膜器件的液体测试环境，并对液体中的频率响应曲线进行测量。第二、由基本的流体动力学方程组出发，综合考虑器件的工作原理、结构参数、材料性能等因素，提出符实际情况的基本假设和边界条件，对方程组进行简化。第三、用有限元方法对模型进行数值求解。最后，通过实验结果对模型的基本假设和边界条件进行验证和完善，建立能对耳蜗环境产生的影响做出准确预测的模型。本项目的成果将为后续面向真实耳蜗腔淋巴液环境的微型可植入压电薄膜助听器件的研究和优化设计建立基础平台和参考依据，具有重要的科学和实际意义。

混合植入式助听器和全植入人工耳蜗是当前听力康复领域的热点方向，基于压电薄膜的微机电系统（MEMS）是它们在内耳产生音波或拾取音波的重要器件，而狭小的耳蜗腔与其中的淋巴液对薄膜型器件性能具有重要的影响。本项目通过数值仿真与实验相结合的方法研究发现，这种耦合效应可以被分为附加质量和附加阻尼两种类型。其中附加质量将使薄膜的谐振频率的下降至空气中的25%；产生附加质量的液体范围在薄膜法向方向约为薄膜厚度的300倍，不同液体环境的边界条件将改变附加质量与液面高度的关系，而附加质量与薄膜的振动频率和振幅均没有关系。附加阻尼的效果与压电薄膜的振动频率相关而与振动幅度无关。附加质量与附加阻尼均随着压电薄膜与固体边界之间间距的减小而显著增加，本项目研究得到的数值模型对于压电薄膜品质因数的预测误差在间距大于30微米的情况下小于15%。此外本项目还对压电薄膜以及耳蜗内的微电极阵列的加工工艺进行了研究，并对微电极阵列的刺激分辨率进行了优化设计。本项目所取得的成果为微型可植入声电混合助听器件的研究和优化设计建立了基础平台和参考依据，具有重要的科学和实际意义。