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Sensors 2016, 16(8), 1248; doi:10.3390/s16081248

Design and Fabrication of Double-Focused Ultrasound Transducers to Achieve Tight Focusing

1
and
1,2,3,*
1
Department of Electronic Engineering, Sogang University, Seoul 04107, Korea
2
Department of Biomedical Engineering, Sogang University, Seoul 04107, Korea
3
Sogang Institutes of Advanced Technology, Sogang University, Seoul 04107, Korea
*
Author to whom correspondence should be addressed.
Academic Editors: Dipen N. Sinha and Cristian Pantea
Received: 4 June 2016 / Revised: 26 July 2016 / Accepted: 3 August 2016 / Published: 6 August 2016
(This article belongs to the Special Issue Ultrasonic Sensors)
View Full-Text   |   Download PDF [3797 KB, uploaded 6 August 2016]   |  

Abstract

Beauty treatment for skin requires a high-intensity focused ultrasound (HIFU) transducer to generate coagulative necrosis in a small focal volume (e.g., 1 mm3) placed at a shallow depth (3–4.5 mm from the skin surface). For this, it is desirable to make the F-number as small as possible under the largest possible aperture in order to generate ultrasound energy high enough to induce tissue coagulation in such a small focal volume. However, satisfying both conditions at the same time is demanding. To meet the requirements, this paper, therefore, proposes a double-focusing technique, in which the aperture of an ultrasound transducer is spherically shaped for initial focusing and an acoustic lens is used to finally focus ultrasound on a target depth of treatment; it is possible to achieve the F-number of unity or less while keeping the aperture of a transducer as large as possible. In accordance with the proposed method, we designed and fabricated a 7-MHz double-focused ultrasound transducer. The experimental results demonstrated that the fabricated double-focused transducer had a focal length of 10.2 mm reduced from an initial focal length of 15.2 mm and, thus, the F-number changed from 1.52 to 1.02. Based on the results, we concluded that the proposed double-focusing method is suitable to decrease F-number while maintaining a large aperture size. View Full-Text
Keywords: therapeutic ultrasound transducer; skin disease treatment; acoustic lens; press-focusing; double-focusing; 1-3 piezo-composite therapeutic ultrasound transducer; skin disease treatment; acoustic lens; press-focusing; double-focusing; 1-3 piezo-composite
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Jang, J.; Chang, J.H. Design and Fabrication of Double-Focused Ultrasound Transducers to Achieve Tight Focusing. Sensors 2016, 16, 1248.

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