多孔微泡的动力学研究
Dynamics of entrapped microbubbles with multiple openings
摘要：
水中微气泡在声场的激励下产生振动，产生声辐射力和拖曳声流。这些力可以用于各种生物医学应用，如靶向药物输送和芯片上生物操纵。使用微泡作为致动器的传统方法是将它们捕获在微加工的腔体内。通过约束空气与水相互作用的界面来施加各向异性力。现有的球形气泡的分析模型是无法预测的气泡在这种配置的动态。在这里，一个新的模型内的任意形状的空腔多个圆形开口的气泡被困。半分析模型通过优化问题的解决方案捕获更真实的几何形状。我们挑战的假设，气泡应在其第一个共振频率激发，以优化其性能。计算固有频率和相关的正常振动模式，其随后用于通过有限元模拟来计算声流模式和相关联的推力。建立了一个实验平台来测量由微制造气泡致动器加载的梁的偏转，并可视化所产生的流模式。结果突出了计算模型作为工程应用的设计工具的贡献。
英文摘要：
Microbubbles excited by acoustic fields inside water oscillate, and generate acoustic radiation forces and drag-induced acoustic streaming. These forces can be harnessed in various biomedical applications such as targeted drug delivery and on-chip biomanipulation. The conventional approach for using microbubbles as actuators is to trap them inside microfabricated cavities. Anisotropic forces are applied by constraining the interfaces where the air interacts with water. The existing analytical models derived for spherical bubbles are incapable of predicting the dynamics of bubbles in such configurations. Here, a new model for bubbles entrapped inside arbitrarily shaped cavities with multiple circular openings is developed. The semi-analytical model captures a more realistic geometry through a solution to an optimization problem. We challenge the assumption that bubbles should be excited at their first resonance frequency to optimize their performance. The natural frequencies and the correlated normal vibration modes are calculated, which are subsequently used to compute the acoustic streaming patterns and the associated thrust by a finite element simulation. An experimental platform was built to measure the deflection of beams loaded by microfabricated bubble actuators, and visualize the generated streaming patterns. The results highlight the contribution of the computational model as a design tool for engineering applications.
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