MEMS scale artificial hair cell sensors inspired by the cochlear amplifier effect

Abstract

Research over the past few decades has shown that the ear exhibits an important, nonlinear amplification called the “cochlear amplification.” It is responsible for boosting faint sounds and improving frequency sensitivity, which allows the ear to process a larger range of sound intensities (from about 20 micro-Pa to 20 Pa). In contrast, typical microphones, accelerometers, and other dynamic sensors are designed to operate linearly in the sensor’s quasi-static response region. Instead, the cochlea operates in the resonance region, where weak inputs are significantly amplified. The goal of our research is to develop unique, piezoelectric-based MEMS sensors that mimic the function of hair cells in the mammalian cochlea. Inspired by the geometry of the hair cells, a set of artificial hair cells (AHCs) are designed based on piezoelectric cantilever beams. Developing piezoelectric, MEMS AHC arrays capable of mimicking the cochlea’s behavior is the main scope of this work. The design consists of a substrate material and two layers of Lead Zirconate Titanate (PZT) deposition that represents artificial hair cells. Abaqus finite element software is used to model the AHC arrays. Fundamental frequencies of the AHCs and also frequency response function due to a base excitation of the array are obtained by linear perturbation frequency analysis and steady-state linear dynamic analysis, respectively. As a proof of concept, a series of dynamic tests are conducted on larger scale single AHCs and an array of four AHCs to measure the response of the sensors to an external stimulus.