Bio-Inspired Inner-Ear Microphones via a Piezoelectric Substrate and Nanorods

本项目的研究目标是通过模拟耳蜗中的毛细胞来开发一种特别敏感的麦克风。人类的听觉是一种极其敏感的生物感知机制，已经进化了数百万年。人的耳朵由三部分组成：外耳、中耳和耳蜗。外耳收集传入的声波以震动鼓膜。中耳将振动转换为耳蜗内的压力波。在耳蜗内，有数千个毛细胞被液体包围。毛细胞有纳米结构和图案的立体纤毛，在微小的压力波动下摆动和变形，以感知传入的声音。压力可低至20微帕，在耳蜗亚纳米范围内运动。随着人类年龄的增长，毛细胞逐渐丧失，听力恶化。暴露在噪音中会导致立体纤毛的进一步丧失或损害。对于几近失聪的患者(尤其是儿童)，外科医生将人工耳蜗(CI)以电极的形式插入耳蜗内，以直接刺激听神经元。CI研究中的最新努力是将麦克风与电极一起集成到耳蜗内。这种设计的优点是没有笨重的外部部件，通过听觉通路更自然地听力，更通用的语音处理算法，以及减少手术时间和复杂性。一个主要的瓶颈是无法获得一个灵敏度足够高的微型麦克风来安装到耳蜗中。在CI研究中对耳壳内麦克风的需求的推动下，PI计划通过模仿耳蜗毛细胞来开发一种特别灵敏的麦克风。该装置由带有电极的压电衬底和图案化纳米棒阵列组成。当周围流体的压力波动时，每个纳米棒都会受到阻力，使压电基板变形，从而产生电荷。大量的纳米棒显着放大了产生的电荷，增强了对压力波动的敏感性。设定了三个具体目标来实现。首先，使用硅/PZT和塑料/PZT纳米棒基板制造仿生麦克风(BIM)，其次，进行校准实验来研究BIM的可行性，第三，进行分析研究，以了解纳米棒的图案和尺寸如何影响BIM的灵敏度。预计在2.78亿听力障碍者中，很大一部分人可以从这项研究中受益于听力传感。听力康复研究将变得越来越重要，因为美国人口正在老龄化，预期寿命正在增加。这项研究还将通过精心设计的国际合作、招募代表性不足的学生和本科生、修订课程、外联和出版研究成果来扩大其影响。

The research objective of this project is to develop an extra-sensitive microphone by mimicking hair cells in the cochlea. Human hearing is an extremely sensitive bio-sensing mechanism that has evolved for millions of years. The human ear consists of three parts: the outer ear, middle ear, and cochlea. The outer ear collects incoming sound waves to vibrate the eardrum. The middle ear transduces the vibration to pressure waves in the cochlea. Inside the cochlea, there are thousands of hair cells surrounded by fluid. Hair cells have nano-structured and patterned stereocilia swinging and deforming under tiny pressure fluctuations to sense the incoming sound. The pressure can be as low as 20 micro-Pa with a motion in the sub nm range in cochlea. As humans age, hair cells are gradually lost and hearing deteriorates. Exposure to noise can lead to further loss or damage of stereocilia. For nearly deaf patients (especially children), surgeons insert cochlear implants (CI) in the form of an electrode into cochlea to directly stimulate auditory neurons. The newest endeavor in CI research is to incorporate a microphone inside the cochlea along with the electrode. Such design has the advantage of no bulky external components, more natural hearing via auditory pathways, more versatile speech processing algorithms, and reduced surgical time and complexity. A major bottleneck is the unavailability of a tiny microphone with high enough sensitivity to fit into cochlea. Motivated by the needs for an intracochlear microphone in CI research, the PI plans to develop an extra-sensitive microphone by mimicking hair cells in the cochlea. The device consists of a piezoelectric substrate with electrodes and an array of patterned nanorods. When the pressure of the surrounding fluid fluctuates, each nanorod receives a drag force deforming the piezoelectric substrate to generate electric charge. The large number of nanorods significantly amplifies the generated charge enhancing the sensitivity to the pressure fluctuation. Three specific goals are set to achieve. First, to fabricate the bio-inspired microphone (BIM) using a silicon/PZT and a plastics/PZT substrate with nanorods, second, to conduct calibrated experiments to study the feasibility of the BIM, and third, to conduct an analytical study to understand how the pattern and dimensions of the nanorods affect the sensitivity of the BIM.It is anticipated that a good portion of the estimated 278 million people who have hearing disability could benefit from this research in hearing sensing. Hearing rehabilitation research will become progressively important, because US population is aging and life expectancy is increasing. The research will also broaden its impact via a well-designed international collaboration, recruitment of underrepresented and undergraduate students, curriculum revision, outreach, and publication of research results.