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A Method to Minimize Resonant Frequency Drift of CMUTs Due to Fluid Loading

Authors:
Thasnim Mohammed
Sazzadur Chowdhury

Keywords: CMUT; electrostatic spring softening; fluid loading effect; resonant frequency drift; 3D FEA

Abstract:
This paper presents a method to minimize the resonant frequency drift of Capacitive Micromachined Ultrasonic Transducers (CMUTs) due to fluid loading. A unified mathematical model for the resonant frequency of a CMUT that includes the electrostatic spring softening effect and the fluid loading effect due to the coupled fluidic layer has been developed that provides the basis of the proposed approach. The minimization method involves dynamic adjustment of the DC bias voltage to modify the electrostatic spring softening parameter to offset the effects of fluid loading. Analytical and COMSOL based 3D Finite Element Analysis (FEA) results show that the drift in the resonant frequency of a 6 MHz CMUT operated in water can be compensated by adjusting the bias voltage by 2% from its 75% pull-in voltage value to render an improvement of 4% in lateral and axial resolutions in imaging applications. A bias voltage adjustment of 9% of the 75% pull-in voltage value is necessary to achieve an improvement of 20.74% when the CMUT is operated in glycerol.

Pages: 86 to 91

Copyright: Copyright (c) IARIA, 2021

Publication date: November 14, 2021

Published in: conference

ISSN: 2308-3514

ISBN: 978-1-61208-918-8

Location: Athens, Greece

Dates: from November 14, 2021 to November 18, 2021