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Acoustic reflectivity minimization in Capacitive Micromachined Ultrasonic Transducers (CMUTs)
Monica La Mura1, Nicola A Lamberti1, Barbara L Mauti2
1Dipartimento di Ingegneria Industriale, Università degli Studi di Salerno, Italy.
Ultrasonics
|September 20, 2016
Summary
This study introduces a method to reduce unwanted echoes in Capacitive Micromachined Ultrasonic Transducers (CMUTs) when used with water. The technique significantly lowers signal reverberation, improving ultrasound imaging quality.
Area of Science:
- Acoustics and Ultrasonics
- Materials Science
- Biomedical Engineering
Background:
- Capacitive Micromachined Ultrasonic Transducers (CMUTs) exhibit high front-face acoustic reflectivity when coupled with water due to impedance mismatch.
- This reflectivity causes signal reverberation in pulse-echo operation, leading to artifacts and reduced contrast in ultrasound imaging.
Purpose of the Study:
- To propose and validate a method for reducing front-face reflectivity and signal reverberation in CMUTs.
- To introduce a Reverberation Level (RL) index for quantifying unwanted signal reverberation.
Main Methods:
- The proposed method involves increasing bias voltage, applying an optimized resistive load, and adding a low-impedance acoustic backing to Reverse Fabrication Process (RFP)-CMUTs.
- Finite Element simulations were used for analysis, and experimental characterization of single-element RFP-CMUTs with varying backing materials and electrical loads was performed.
Main Results:
- The combined method improved mechanical energy conversion, transmission to the backing, and electrical energy dissipation.
- A Reverberation Level (RL) reduction of 8.6dB was achieved in the analyzed prototypes.
Conclusions:
- The developed method effectively reduces front-face reflectivity and signal reverberation in CMUTs.
- This approach enhances ultrasound imaging quality by mitigating artifacts caused by signal reverberation.
