Dynamic Response of Constrained Bubbles to Acoustic Excitation

University Of Rochester, Rochester NY

Investigators

Abstract

Abstract Numerous systems, from biomedical ultrasound to microfluidics, depend on the dynamic response of bubbles whose expansion is constrained by a surrounding tube or channel. For example, potential therapeutic uses of biomedical ultrasound, including localized drug delivery and clot dissolution, may be enhanced by the acoustic excitation of targeted bubbles within the blood stream. The goal of this project is to develop an understanding of the complex dynamic interactions between a gas cavity in a liquid and a surrounding compliant solid tube or channel. The physical system is quite complex because 1) it is a three-phase system, 2) the deformations of the bubble and tube can be large, and 3) the behavior of the system can be highly nonlinear. A major objective is to identify the important physical parameters and response characteristics of a constrained acoustically excited bubble. In particular, the effect of tube/channel parameters on both the resonance frequencies and nonlinear dynamic responses of bubbles (excited by a range of acoustic sources) will be characterized. To model the highly nonlinear interaction of this three-phase system with large deformations and rapidly changing time scales, simulation techniques will be developed using coupled boundary element and finite element methods. The simulation models will be updated based on the additional insight obtained from ultrasonic displacement measurements and high-speed photography observations of the responses of bubbles subject to a range of acoustic sources. A fundamental understanding of the dynamic response of bubbles to ultrasonic waves confined by vessels or channels will aid the development of a wide variety of systems including a) novel microfluidic devices, b) more effective drug delivery and activation techniques, c) new ultrasonic clot dissolution techniques, and d) guidelines for the safe use of echo contrast agents for improved diagnostic ultrasonic imaging. In addition, a Dynamic Measurements Laboratory will be developed to train undergraduate and graduate students in dynamic system response using experimental techniques such as ultrasonic displacement measurements and high-speed photography. These dynamic measurement techniques will be integrated into undergraduate and graduate laboratories and vibration classes to provide hands-on training tools. Instructional demonstrations to introduce girls in middle and high school to science and engineering will be developed using the high-speed camera.