Generating and Focusing the Ultrasound Waves Using Elastomer-based Capacitive Micro-Speakers

Document Type : Original Article


1 Mechanical Engineering Department, Urmia University, Urmia, Iran

2 Institute of Engineering and Technology, South Ural State University, Chelyabinsk, Russian Federation


Ultrasound wave is a kind of waves with the frequency higher than the human audible frequency. Although ultrasound was first used for military identification purposes, it has been used for decades for various other applications, especially medical applications. Medical applications of ultrasound include diagnostic and therapeutic applications, such as for the treatment of cancer. In this paper, for the first time, electrostatically-actuated micro-speakers made of a dielectric elastomer (DE) have been used to generate and focus the ultrasonic waves using Micro-Electro-Mechanical Systems (MEMS) technology. The results have shown that a single micro-speaker could not generate an efficient focused wave, so an array of the micro-speakers has been considered. The layout of the micro-speakers is a square array of Bessel Panel. It has been shown that by adopting a suitable excitation frequency as well as number of the elements in the Bessel’s panel, the DE-based capacitive micro-structures can focus the generated sound wave in a pre-determined area.


1. Harvey, E.N., Loomis A.L., “High frequency sound waves of
small intensity and their biological effects”. Nature Publishing
Group. Vol. 121, (1928), 622-624.  
2. Murad, H.Y., “High intensity focused ultrasound (HIFU) in
conjunction with thermally triggered chemotherapy as a
synergistic treatment of cancer”. Tulane University School of
Science and Engineering, (2016). 
3. Fry, W., Fry, F., “Fundamental neurological research and human
neurosurgery using intense ultrasound”. IRE Transactions on
Medical Electronics, Vol. 7, (1960), 166-181.  
4. Jang, H.J., Lee, JY., Lee, DH., Kim, WH. and Hwanget, JH.,
“Current and future clinical applications of high-intensity focused
ultrasound (HIFU) for pancreatic cancer”. Gut and Liver, Vol. 4,
(2010), S57-S61. 
5. Minin, O., Minin. I, “Ultrasound Imaging: Medical
Applications”. BoD–Books on Demand. (2011).  
6. Opieliński, K., “Application of transmission of ultrasonic waves
for characterization and imaging of biological media structures”.
Printing House of Wroclaw University of Science and
Technology, Wroclaw, (2011). 
7. Azhari, H., “Basics of biomedical ultrasound for engineers”. John
Wiley & Sons (2010). 
8. Escoffre, J.M., Bouakaz, A., “Therapeutic ultrasound”. Springer
Vol. 880, (2015). 
9. Allan, P.L., Baxter, G.M. and Weston, M.J. “Clinical
Ultrasound”. E-Book: Expert Consult: Online and Print. Elsevier
Health Sciences Vol 2, (2011). 

10. Staszewski, W., Gudra, T., and Opieliński, K., “The Acoustic
Field Distribution Inside the Ultrasonic Ring Array”. Archives of
Acoustics, Vol. 43, No. 3, (2018). 455–463. 
11. Opieliński, K.J., Pruchnicki and P., Szymanowski P.,
“Multimodal ultrasound computer-assisted tomography: An
approach to the recognition of breast lesions”. Computerized
Medical Imaging and Graphics, Vol. 65, (2018), 102-114. 
12. De Pasquale, G., Rufer, L., Basrour, S., and Somà, A., “Modeling
and validation of acoustic performances of micro-acoustic
sources for hearing applications”. Sensors and Actuators A:
Physical, Vol. 247, (2016), 614-628. 
13. Varadan, V.K., Vinoy, KJ., Jose, KA., “Their Applications”.
Pennsylvania State University, USA, Wiley Online Library,
14. Heydt, R., Kornbluh, R., Eckerle, J., “Sound radiation properties
of dielectric elastomer electroactive polymer loudspeakers”.
Smart Structures and Materials. Electroactive Polymer
Actuators and Devices (EAPAD). Vol. 6168, (2006), 1-8. 
15. Bar-Cohen, Y., “Electroactive polymer (EAP) actuators as
artificial muscles: reality, potential, and challenges”. SPIE press
Bellingham, WA., Vol. 136., (2004).  
16. Feng, C., Jiang, L. and Lau, W.M., “Dynamic characteristics of a
dielectric elastomer-based microbeam resonator with small
vibration amplitude”. Journal of Micromechanics and Micro
engineering, Vol. 21, (2011), 095002. 
17. Sarban, R., Jones, RW.,  Mace, BR. and E Rustighi, E., “A tubular
dielectric elastomer actuator: Fabrication, characterization and
active vibration isolation”. Mechanical Systems and Signal
Processing, Vol. 25, (2011), 2879-2891. 
18. Carpi, F.,  Rossi, D .De, Kornbluh, R. and Pelrine, RE.,
“Dielectric elastomers as electromechanical transducers”.
Fundamentals, materials, devices, models and applications of an
emerging electroactive polymer technology, Elsevier. (2011).  
19. Keele Jr, D., “Effective performance of Bessel arrays”. Journal
of the Audio Engineering Society, Vol. 38, (1990), 723-748. 
20. Reddy, J.N., “Energy and variational methods in applied
mechanics: with an introduction to the finite element method”.
Wiley New York, (1984). 
21. Varadan, V.K.,  Vinoy, KJ. and Jose, KA., “RF MEMS and their
Applications”. Pennsylvania State University, USA, (2003). 
22. Mostafaei, B., Fathalilou, M., and Rezazadeh, G.,“A comparative
analysis of efficiency and reliability of capacitive micro-switches
with initially curved electrodes”. Microsystem Technologies,
(2019), online available. 
23. Rezazadeh, G., Fathalilou, M., and Shabani, R., “Static and
dynamic stabilities of a microbeam actuated by a piezoelectric
voltage”. Microsystem Technologies, Vol. 15, (2009), 17851791.
24. Kinsler, L.E., Frey A.R., Coppens, A.B., Sanders, J.V.,
“Fundamentals of acoustics. Fundamentals of Acoustics”. 4th
Edition, Wiley-VCH, pp. 560. ISBN 0-471-84789-5. (December
1999), 560. 
25. Kuttruff, H., “Acoustics: an introduction”. CRC Press. (2006).