A New Approach to Capacitive Sensing: Repulsive Sensors

提案标题：一种新的方法，电容传感：排斥sensorsBrief项目目标的描述：这项研究的目的是设计一种新的方法，电容传感，并证明其有效性的MEMS microphones.Abstract：非技术性助听器是有用的工具，老龄化人口可以使用，以提高他们的生活质量。微型麦克风是助听器的关键部件，其声学性能决定了助听器在帮助听力受损者在嘈杂环境中进行交流方面的有效性。微机电系统（MEMS）麦克风由于其小的形状因子以及其与大批量制造工艺的兼容性而已经发展为主导便携式电子设备（诸如蜂窝电话）中的微型麦克风的市场。虽然MEMS麦克风有潜力在助听器中提供显著的性能改进，但它们通常还没有表现出足够的性能来满足这种要求苛刻的应用。拟议研究的目标是更好地利用MEMS技术，使高性能MEMS麦克风的设计发生革命性变化。如果成功的话，这项研究将为助听器带来更灵敏的MEMS麦克风，并将对听力受损者的生活产生巨大的影响。MEMS麦克风的噪声性能将是主要的改进，可以帮助老年人听得更好。技术使用静电排斥指的电容式传感是一种新颖的概念，可以改变许多因传统平行板传感器的吸合不稳定性而受到功能限制的应用。自1916年电容式麦克风发明以来，吸合电压的限制显著降低了这些设备在噪声性能和灵敏度方面的功能。我们建议使用微机电系统（MEMS）电容式传感机制的基础上的排斥力，不像传统的电容式传感器，不遭受吸合电压。这种方法允许显著增加的偏置电压，这将大大改善麦克风的信噪比和电灵敏度。这里研究的MEMS麦克风由硅振膜组成，该硅振膜在暴露于声压时绕轴旋转。膜片包含多个电容传感器单元，并且它们的电容变化转换为电容器中的电压。一个单位传感器单元包括一个可移动的手指上面的垂直对齐的固定手指旁边的未对齐的固定手指。当在对准的和未对准的指状物中产生电势差时，在可移动指状物上产生不对称电场，从而产生将其推离衬底的排斥力。我们的初步研究表明，单位传感器单元的初始间隙可以被设计成使得可移动指状物上的力保持排斥，这防止了可移动指状物在基板上的塌陷（拉入）。由于可动手指上电场分布的不对称性，使得电容与机械位移之间存在复杂的耦合关系。因此，为了获得耦合系统行为的基本理解，我们将创建电容式MEMS传感器的分析和数值模型。使用模型模拟，我们将设计所需的灵敏度的传感器。使用微加工技术，我们将建立传感器和表征其行为使用激光多普勒振动计。在将传感器与麦克风电路集成后，我们将在消声室中测试系统，以验证传感器提高麦克风的性能和灵敏度。

Proposal Title: A New Approach to Capacitive Sensing: Repulsive SensorsBrief Description of Project Goals: This research aims to devise a new approach to capacitive sensing and to demonstrate its effectiveness in MEMS microphones.Abstract:Nontechnical Hearing aids are useful tools an aging population can use to improve their quality of life. Miniature microphones are a key component in hearing aids and their acoustic performance determines the effectiveness of hearing aids in helping the hearing impaired communicate in noisy environments. Micro-Electro-Mechanical Systems (MEMS) microphones have grown to dominate the market for miniature microphones in portable electronic devices such as cell phones due to their small form factor as well as their compatibility with high-volume manufacturing processes. While MEMS microphones have the potential of providing significant performance improvements in hearing aids, they have generally not yet demonstrated sufficient performance for this demanding application. A goal of the proposed research is to take better advantage of MEMS technology to enable a revolutionary change in the design of high-performance MEMS microphones. If successful, this research will lead to more sensitive MEMS microphones for hearing aids and will have a tremendous impact on the lives of hearing impaired. Noise performance of the MEMS microphone will be the major improvement that can help the aging population hear better.Technical Capacitive sensing using electrostatic repulsive fingers is a novel concept that can transform many applications suffering from limited functionality due to the pull-in instability of conventional parallel plate sensors. Since the invention of capacitive microphones in 1916, the limitation of pull-in voltage has significantly diminished the functionality of these devices in terms of noise performance and sensitivity. We propose using a Micro-Electro-Mechanical Systems (MEMS) capacitive sensing mechanism based on the repulsive force that, unlike conventional capacitive sensors, does not suffer from pull-in voltage. This approach allows significantly increased bias voltages that will substantially improve the signal-to-noise ratio and electrical sensitivity of microphones. The MEMS microphone examined here is composed of a silicon diaphragm that rotates about an axis upon exposure to sound pressure. The diaphragm incorporates a number of capacitive sensor unit cells, and their change in capacitance converts to a voltage in the preamplifier. A unit sensor cell consists of a movable finger above a vertically aligned fixed finger next to an unaligned fixed finger. When potential differences are made in the aligned and unaligned fingers, an asymmetric electric field is created on the movable finger, generating a repulsive force that pushes it away from the substrate. Our preliminary studies show that the initial gap of the unit sensor cell can be designed so the force on the movable finger remains repulsive, which prevents the collapse of the movable fingers on the substrate (pull-in). The asymmetric electric field distribution on the movable finger causes a complicated coupled relationship between the capacitance and mechanical displacement. Therefore, to gain a fundamental understanding of the coupled system behavior, we will create analytical and numerical models of the capacitive MEMS sensor. Using the model simulations, we will design the sensor for desired sensitivity. Using microfabrication techniques, we will build the sensor and characterize its behavior using a Laser Doppler Vibrometer. After integrating the sensor with preamplifier circuitry, we will test the system in an anechoic chamber to verify the sensor improves the performance and sensitivity of microphones.