Research Papers

Effects of Added Mass on Lead-Zirconate-Titanate Thin-Film Microactuators in Aqueous Environments

[+] Author and Article Information
Chuan Luo

Assistant Professor
Department of Precision Instruments,
Tsinghua University,
Beijing 100084, China

W. C. Tai

Department of Mechanical Engineering,
University of Washington,
Seattle, WA 98195-2600

Cheng-Wei Yang

Department of Mechanical and
Aerospace Engineering,
University of California, Los Angeles,
Los Angeles, CA 90095-1597

G. Z. Cao

Department of Material
Science and Engineering,
University of Washington,
Seattle, WA 98195-2120

I. Y. Shen

Department of Mechanical Engineering,
University of Washington,
Box 352600,
Seattle, WA 98195-2600
e-mail: ishen@u.washington.edu

1Corresponding author.

Contributed by the Design Engineering Division of ASME for publication in the JOURNAL OF VIBRATION AND ACOUSTICS. Manuscript received May 3, 2015; final manuscript received July 1, 2016; published online September 30, 2016. Assoc. Editor: Nader Jalili.

J. Vib. Acoust 138(6), 061015 (Sep 30, 2016) (10 pages) Paper No: VIB-15-1150; doi: 10.1115/1.4034613 History: Received May 03, 2015; Revised July 01, 2016

In this paper, we conduct experimental, theoretical, and numerical studies of a lead-zirconate-titanate (PZT) thin-film microactuator probe submerged in water. The major component of the actuator is a PZT diaphragm anchored on four silicon sidewalls. There is also silicon residue at the juncture of the diaphragm and the sidewalls due to imperfect etching processes. In the experimental study, frequency response functions of actuator displacement are measured via a laser Doppler vibrometer and a spectrum analyzer. The measurements show that the first natural frequency of the microactuator reduces from 80 kHz in air to 20 kHz when the microactuator is submerged in water. A viable explanation is that the surrounding water induces significant added mass to the microactuator. Estimation of the added mass based on theories in fluid mechanics successfully reconciles the predicted frequency to the vicinity of 20 kHz confirming the effects of added mass. Finite element models are also created to study how the silicon sidewalls and residue affect the added mass. Simulations show that presence of the sidewalls or residue would modify the fluid flow thus altering the added mass and natural frequency. In general, the finite element predictions agree well with the experimental measurements within 10% difference.

Copyright © 2016 by ASME
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Fig. 1

Schematic drawing of PZT thin-film membrane actuator placed in cochlea (not to scale)

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Fig. 2

Schematic drawing of the PZT microactuator probe

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Fig. 3

Photo and schematic drawing of experimental setup

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Fig. 4

Measured FRF of the PZT probe in air and in water

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Fig. 5

Assumed shaped for the calculation of added mass; the square domain has a simply supported boundary condition

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Fig. 6

Cross-sectional view of the probe

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Fig. 7

Deflection profile and equivalent length

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Fig. 8

A quarter finite element model: (a) structural domain and (b) fluid domain

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Fig. 9

Ratio of natural frequencies in water and in air as a function of water level

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Fig. 10

Fluid–structure finite element models: (a) the reference model, (b) diaphragm with sidewalls, (c) diaphragm with silicon residue, and (d) diaphragm with sidewalls and silicon residue

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Fig. 11

Simulated pressure field of four models: (a) reference model, (b) diaphragm with sidewalls, (c) diaphragm with silicon residue, and (d) diaphragm with both sidewalls and residue




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