Squeeze Film Effect in Surface Micromachined Nano Ultrasonic Sensor for Different Diaphragm Displacement Profiles

In the present paper, we have analytically explored the small variations of the local pressure in the trapped air film of both sides of the clamped circular capacitive micromachined ultrasonic transducer (CMUT), which consists of a thin movable membrane of silicon nitride (Si N ). This time-independ...

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Bibliographic Details
Published in:Sensors (Basel, Switzerland) Switzerland), 2023-05, Vol.23 (10), p.4665
Main Authors: Dastidar, Avik Ghosh, Maity, Reshmi, Tiwari, Ramesh Chandra, Vidojevic, Dejan, Kevkic, Tijana S, Nikolic, Vojkan, Das, Subhajit, Maity, Niladri Pratap
Format: Article
Language:English
Subjects:
Analysis
CMUT
displacement profile
Edge effect
Electrodes
Engraving
FEM
Measuring instruments
Membranes
Micromachining
modified Bessel’s equation
pressure profile
Reynold’s equation
Sensors
Silicon nitride
Squeeze films
Statistical methods
Viscous damping
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Summary:In the present paper, we have analytically explored the small variations of the local pressure in the trapped air film of both sides of the clamped circular capacitive micromachined ultrasonic transducer (CMUT), which consists of a thin movable membrane of silicon nitride (Si N ). This time-independent pressure profile has been investigated thoroughly by solving the associated linear Reynold's equation in the framework of three analytical models, viz. membrane model, plate model, and non-local plate model. The solution involves Bessel functions of the first kind. The Landau-Lifschitz fringing technique has been assimilated to engrave the edge effects in estimation of the capacitance of CMUT, which should be considered in the micrometer or lesser dimension. To divulge the dimension-based efficacy of the considered analytical models, various statistical methods have been employed. Our use of contour plots of absolute quadratic deviation revealed a very satisfactory solution in this direction. Though the analytical expression of the pressure profile is very cumbersome in various models, the analysis of these outputs exhibits that the pressure profile follows the displacement profile in all the cases indicating no viscous damping. A finite element model (FEM) has been used to validate the systematic analyses of displacement profiles for several radii and thicknesses of the CMUT's diaphragm. The FEM result is further corroborated by published experimental results bearing excellent outcome.
ISSN:1424-8220
1424-8220
DOI:10.3390/s23104665