Browsing by Subject "Biomembranes"

Now showing 1 - 2 of 2

Open Access
Microfabricated ultrasonic transducers: towards robust models and immersion devices
(IEEE, 1996-11) Ladabaum, I.; Jin, X.; Soh, H. T.; Pierre, F.; Atalar, Abdullah; Khuri-Yakub, B. T.
The successful fabrication of ultrasonic immersion transducers is reported. Transducers are observed to operate from 1 MHz to 20 MHz in water, with the frequency range limited by electronics, not the transducers. Transmission results are included which show that a single pair of transducers is able to operate in water at 4, 6, and 8 MHz with a signal to noise ratio of at least 48 dB. The same transducer pair is shown to operate in air at 6 MHz. A model is introduced which highlights the significant parameters of transducer design. The model enables the design of optimized transducers.
Open Access
Micromachinable leaky wave air transducers
(IEEE, 1997-11) Değertekin, F. L.; Atalar, Abdullah; Khuri-Yakub, B. T.
In this paper, ultrasonic air transducers which use the lowest order antisymmetric (A/sub 0/) mode Lamb waves in a thin plate as a means of efficient coupling of ultrasonic energy to air are discussed. For a silicon plate of 1 /spl mu/m thickness, the energy leak rates can go up to 0.6 dB per wavelength. At MHz frequencies the plate thickness should be in the range of 1-10 /spl mu/m, which requires micromachined structures to be used. The radiation pattern of the transducers can be controlled by the geometry of the transducer, which can also be used for focusing. A theoretical model to calculate the efficiency and optimized transducer dimensions is presented. This model is applied to common micromachining materials such as silicon, silicon nitride and silicon dioxide. The analysis show that, with these transducers it is possible to achieve a conversion loss with a minimum of 8.7 dB and 78% fractional bandwidth. Experimental results on transmission imaging are also presented using an implementation of the transducer operating around 580 kHz.