Dynamic Response of Constrained Bubbles to Acoustic Excitation

摘要从生物医学超声到微流体，许多系统都依赖于气泡的动态响应，气泡的膨胀受到周围管子或通道的限制。例如，生物医学超声的潜在治疗用途，包括局部药物输送和血栓溶解，可以通过声学激发血流中的靶向气泡来增强。该项目的目标是了解液体中的气腔与周围顺应的固体管或通道之间的复杂动态相互作用。物理系统相当复杂，因为1)它是一个三相系统，2)气泡和管子的变形可能很大，3)系统的行为可能是高度非线性的。一个主要的目标是识别受约束声激励气泡的重要物理参数和响应特性。特别是，管/通道参数对气泡(由一系列声源激励)的共振频率和非线性动态响应的影响将被表征。为了模拟这一具有大变形和快速变化时间尺度的三相系统的高度非线性相互作用，将发展耦合边界元和有限元方法的模拟技术。模拟模型将根据超声位移测量和对气泡对各种声源的响应的高速摄影观察获得的额外洞察力进行更新。对气泡对受血管或通道限制的超声波的动态响应的基本了解将有助于开发各种系统，包括a)新型微流体设备，b)更有效的药物输送和激活技术，c)新的超声凝块溶解技术，以及d)用于改进诊断超声成像的回声造影剂的安全使用指南。此外，还将建立一个动态测量实验室，培训本科生和研究生使用超声波位移测量和高速摄影等实验技术进行动态系统响应方面的培训。这些动态测量技术将被整合到本科和研究生实验室以及振动课程中，以提供动手培训工具。将使用高速摄像机制作向初中和高中女生介绍科学和工程知识的教学演示。

AbstractNumerous 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.