Development of Active Artificial Hair Cell Sensors

The cochlea is known to exhibit a nonlinear, mechanical amplification which allows the ear to detect faint sounds, improves frequency discrimination, and broadens the range of sound pressure levels that can be detected. In this work, active artificial hair cells (AHC) are proposed and developed which mimic the nonlinear cochlear amplifier. Active AHCs can be used to transduce sound pressures, fluid flow, accelerations, or another form of dynamic input. These nonlinear sensors consist of piezoelectric cantilever beams which utilize various feedback control laws inspired by the living cochlea. A phenomenological control law is first examined which exhibits similar behavior as the living cochlea. Two sets of physiological models are also examined: one set based on outer hair cell somatic motility and the other set inspired by active hair bundle motility. Compared to passive AHCs, simulation and experimental results for active AHCs show an amplified response due to small stimuli, a sharpened resonance peak, and a compressive nonlinearity between response amplitude and input level. These bio-inspired devices could lead to new sensors with lower thresholds of sound or vibration detection, improved frequency sensitivities, and the ability to detect a wider range of input levels. These bio-inspired, active sensors lay the foundation for a new generation of sensors for acoustic, fluid flow, or vibration sensing.