Optimization, Design and Analysis of a MEMS Microphone with PVDF as a Structural Layer for Cochlear Implant Applications

Abstract

The cochlear implants are the most advanced technology for hearing aid impairments. It consists of a microphone or sensor, speech processor, stimulator, and the electrodes. The speech processor in the implant uses the MEMS microphones to pick the signals and process. Here we have proposed a model of MEMS microphone with PVDF as a structural layer and aids in converting the received sound signal into electrical impulses. The proposed device modeling overcomes the main bottlenecks of CIs in terms of footprint, volume, mass, and stimulation signal. A simplified analytical model of PVDF membrane for a microphone application is optimized and developed. The PVDF membrane with its piezoelectric phenomenon acts as a frequency separator for a given acoustic pressure, and it undergoes vibration and accumulation of static charges on the surface of the material that is captured using appropriate signal conditioning circuits with charge amplifiers and filters. First, the geometry with optimized parameters using mathematical modeling was built using COMSOL Multiphysics. The optimization was carried out using predetermined values of thickness and width as the design parameters to form a structure for the dominant resonant frequency. The optimized model built-in geometry of COMSOL is analyzed to the next process that included meshing, setting the environment for the membrane to act as an acoustic model using appropriate multiphysics and perform the study using time-dependent variables and frequency domain. The membrane is analyzed for stress distribution along the walls and the center. Similar studies are carried out for PVDF membrane with a patch of PZT with optimized dimensions. A comparative analysis of the membrane for its acoustic property is to serve as a membrane in a MEMS microphone. A detailed analysis for a PVDF membrane is in terms of resonant frequency, stress, maximum displacement for the input acoustic pressure. This approach of simulating the optimized design for a structure to be a membrane in a MEMS acoustic sensor is validated, and thus, demonstrating it can be reliably used as a piezoelectric membrane in a MEMS process of a product.