Experimental investigation on dynamic characteristics of hexagonal CMUT
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In the present work, nonlinear dynamic characteristics of hexagonal capacitive micromachined ultrasonic transducer (CMUT) devices are reported for the first time. The 10 × 10 arrays showed a central frequency of 1.713 MHz with a bandwidth of 65 kHz, indicating synchronous vibration of the cells. Single cells and array are analyzed for their resonant frequency, quality factor, pull-in and mode of operation. The experimental analysis shows the resonance frequency shifts in the nonlinear regime. Spring hardening and then transition to spring softening of the structure with DC bias is observed on membranes with varying thicknesses. The paper demonstrates experimentally the traits of a single hexagonal cell with frequency shift under squeeze film damping phenomenon. The resonance frequency of these devices was found to vary from 1.58 to 1.83 MHz and this is attributed to the variation in thickness of the membrane across the wafer which is validated by FEM simulation results.
Financial support from DAE-IGCAR, Kalpakkam under grant-in-aid project is gratefully acknowledged. The authors express their sincere thanks to Director, CSIR-CEERI and Director, IGCAR for their support and guidance. They wish to thank all members of Smart Sensors Area at CSIR-CEERI; VKK is thankful to CSIR for grant under emeritus scientist scheme.
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