CAREER: Investigation of bubble dynamics in microscale geometries, with applications in bioengineering and microfluidics

涉及微气泡的动力学现象是美学的、复杂的，并且在气泡喷射打印等工业应用中具有重要意义。如果能很好地理解无界液体中气泡的动力学，那么还需要做大量的基础科学工作来理解有界微观几何中与固体表面接触的气泡的动力学。这个具有根本意义和实际意义的问题将通过两个研究项目来解决。第一个倡议涉及微通道中气泡的动态运动。通道的几何形状和气液壁界面的动态润湿控制了通道中气泡移动所需的压力。这个问题在微流体装置中是至关重要的，其中气泡可以阻塞具有狭窄限制的微通道。该问题将通过基于mems的装置和高速可视化进行理论和实验研究。第二个项目是研究附着在固体表面的微泡对超声波的反应。最近的研究表明，超声波驱动气泡振荡，从而在气泡附近产生一个微小的甜甜圈形状的漩涡，这种现象被称为微流。我们的理论和实验研究将涉及固体边界下的微流模拟和粒子图像测速（PIV）。这种微流场和相关的剪切应力将被用于使生物细胞变形，并使药物通过它们的膜，以及构建一个微引擎。一个通用的微型PIV系统将为这项研究获得，与一个相机，也允许高速成像。智力上的优点是为微气泡与固体几何接触的动力学行为提供了科学基础。这个关于微通道中气泡运动的第一个研究将在理论方面得到与Henrik Bruus合作的支持。并与布鲁克海文国家实验室功能纳米材料中心的奥列格·冈（Oleg Gang）在实验方面（纳米涂层）合作。对润湿角运动、滞后和松弛时间尺度的认识有望取得重大进展。我们的第二个研究将探讨微流如何依赖于气泡润湿角度和附近的固体表面。将进行理论和实验研究，包括（理论方面）耦合固流相互作用声学计算，存在固体边界的声学微流模拟，以及（实验方面）高速可视化以及微粒子图像测速。第二项研究涉及与Citovski博士的合作。以及伦斯勒理工学院多相研究中心的莫拉加博士。更广泛的影响将是与seonic SA和Micronics公司合作开发更可靠的微流体设备，通过自清洁通道几何形状或气泡陷阱解决不希望出现的气泡问题。此外，将研究通过微流与生物细胞相互作用的新方法，并开发一种新的超声装置来控制药物通过细胞膜的转染并操纵它们。微流场还将用于驱动一种适合人类头发的新型微引擎，该引擎将与布鲁克海文国家实验室功能纳米材料中心的奥列格·冈合作开发。最后，我们相信气泡相关现象的可视化提供了一条从日常经验到当前涉及微纳米级现象的科学挑战的有吸引力的途径。这将用于引起布朗克斯当地高中和小学学生对工程的兴趣，并对石溪学生社区的研究产生兴趣。

ABSTRACT 0449269Investigation of bubble dynamics in microscale geometries, with applications in bioengineering and microfluidics Dynamics phenomena involving microbubbles are aesthetic, complex, and important in industrial applications such as bubble-jet printing. If the dynamics of a bubble in an unbounded liquid is well understood, a lot a basic scientific work needs to be done to understand the dynamics of a bubble in contact with a solid surface, in a bounded microscale geometry. This problem of fundamental and practical interest will be addressed through two research initiatives. The first initiative concerns the dynamic motion of a bubble in a microchannel. The channel geometry, and the dynamic wetting at the gas-liquid-wall interface, control the pressure needed to move the bubble in the channel. This issue is critical in microfluidics devices, where bubbles can clog microchannels with narrow restrictions. This problem will be studied theoretically and experimentally with a MEMS-based setup and high-speed visualization. The second initiative studies how a microbubble attached to a solid surface reacts to ultrasound. Recent investigations have shown that ultrasound drives bubbles oscillations, which produce a tiny, donut-shape vortex in the vicinity of the bubble, a phenomenon called microstreaming. Our theoretical and experimental research will involve simulations of microstreaming in the presence of solid boundaries and Particle-Image-Velocimetry (PIV). This microstreaming field and the associated shear stress will be used to deform biological cells and bring drugs through their membranes, as well as to build a microengine. A general-purpose micro- PIV system will be acquired for this research, with a camera that also allows high-speed imaging. The intellectual merit is the development of a science base for the dynamic behavior of microbubbles in contact with a solid geometry. This first study on the motion of a bubble in a microchannel will be supported on the theoretical side by a collaboration with Henrik Bruus.s research group in Denmark, and on the experimental side (nanocoatings) with Oleg Gang, from the Center for Functional Nanomaterials at Brookhaven National Laboratory. Significant advances are expected on the understanding of the motion of the wetting angle, its hysteresis and relaxation time scale. Our second study will investigate how microstreaming depends on the bubble wetting angle and the nearby solid surfaces. Theoretical and experimental investigations will be performed, involving (for the theoretical side) coupled solid-fluid interactions acoustic calculations, simulations of acoustic microstreaming in the presence of solid boundaries, and (for the experimental side) high-speed visualization together with micro Particle Image Velocimetry. This second study involve collaboration with Dr. Citovski.s biology group at Stony Brook, as well as Dr. Moraga from the Center for Multiphase Research at Rensselaer Polytechnic Institute. The broader impact will be the development in collaborations with Seyonic SA and Micronics Inc- of more reliable microfluidic devices, solving the issue of undesired bubbles through self-cleaning channel geometries or bubble traps. Also, novel ways to interact with biological cells through microstreaming will be investigated, with the development of a novel sonoporation device to control drug transfection through cell membranes and manipulate them. The microstreaming flow field will also be used to power a novel type of microengine that fits in a human hair, to be developed in collaboration with Oleg Gang, from the Center for Functional Nanomaterials at Brookhaven National Laboratory. Finally, we are convinced that visualization of bubble-related phenomena provide an attractive path from everyday experience to current scientific challenges involving micro- and nanoscale phenomena. This will be used to interest local high school and elementary school students from the Bronx to engineering, and to generate interest for research in the Stony Brook student community.