AMSV Newsletter 2016

Design of a Collapse-Mode CMUT With an Embossed Membrane for
Improving Output Pressure
Yuanyu Yu, Sio Hang Pun, Peng Un Mak, Ching-Hsiang Cheng, Jiujiang Wang, Pui-In Mak, and
Mang I Vai
From Biomedical research line
In IEEE Transactions on Ultrasonics, Ferroelectrics,
and Frequency Control - TUFFC 2016
Motivation
Architecture
Capacitive micromachined ultrasonic transducers
(CMUTs) have emerged as a competitive
alternative to piezoelectric ultrasonic transducers,
especially in medical ultrasound imaging
and therapeutic ultrasound applications, which
require high output pressure. However, when
compared with piezoelectric ultrasonic transducers,
the output pressure capability of CMUTs
needs still to be improved.
In this work, a novel structure is proposed by
forming an embossed vibrating membrane on a
CMUT cell operating in the collapse mode to
increase the maximum output pressure. By using
a beam model in undamped conditions and
finite-element analysis simulations, the proposed
embossed structure showed improvement
on the maximum output pressure of the
CMUT cell when the embossed pattern was
placed on the estimated location of the peak deflection.
(a)
(b)
(a) 3-D outlook view and (b) 2-D axisymmetric cross-sectional view of
the proposed collapse-mode CMUT with an embossed membrane.
2-D axisymmetric view of the dual embossed patterns located
symmetrically in the vibrating center.
Principle
Result
Based on the analysis of the simply supported beam model,
X = 0.481L is the optimal position for the embossed pattern.
For a collapse-mode CMUT, the output pressure is improved
and the center frequency is reduced with this embossed pattern.
(a)
(b)
(a) Output pressure comparison between the uniform membrane and
the embossed membrane CMUT in the collapse mode. (b) Thinning
embossed membrane to tune center frequency.
Relationship between pressure improvement and center frequency
shift for various embossed positions.