Bulletin of the American Physical Society
75th Annual Meeting of the Division of Fluid Dynamics
Volume 67, Number 19
Sunday–Tuesday, November 20–22, 2022; Indiana Convention Center, Indianapolis, Indiana.
Session U09: Bubbles: Biomedical, Cavitation and Acoustics |
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Chair: Outi Supponen, ETH Zurich Room: 136 |
Tuesday, November 22, 2022 8:00AM - 8:13AM |
U09.00001: Cavitation nucleation in acoustic vaporization of superheated droplets Samuele Fiorini, Anunay Prasanna, Gazendra Shakya, Outi Supponen Acoustic Droplet Vaporization (ADV) is the phase-change process of superheated droplets into bubbles induced by ultrasound waves. The increase in liquid/vapor system volume together with the strong pressure and flow fields created by the rapid vaporization can be exploited in biomedical applications such as embolotherapy and targeted drug delivery. In the effort to elucidate the underlying physics and to improve the precision and safety of ADV, we conduct experiments to characterize micron-sized perfluorocarbon droplet/bubble system dynamics by means of ultra-high-speed videomicroscopy and ultrasound imaging. We also aim at reducing the negative pressure amplitude needed to induce the phase-change by engineering the droplet composition and by tuning the acoustic driving. Experimental observations of cavitation nucleation spots are compared with theoretical models combining nucleation theory and acoustic propagation inside the droplet core in a probabilistic framework, and the influence of their number and positions on the subsequent dynamics of the interface is examined. |
Tuesday, November 22, 2022 8:13AM - 8:26AM |
U09.00002: acoustic bubbles driven actuator for remote energy scavenging in a liquid medium Lin Chai, Deasung Jang, Jinpyo Jeon, Sang kug Chung this paper presents a new type of an acoustic energy scavenging system utilizing a miniature rotor actuated by acoustically oscillating bubbles periodically vibrates piezocantilevers to generate electric power. the behavior of an oscillating bubble under acoustic excitation and the oscillating bubble-induced microstreaming are experimentally investigated to prove the working principle of the proposed acoustically driven actuator. the motion of the acoustically driven actuator and the electric voltage generated from the vibrating piezocantilever are investigated. the rotating speed of the actuator is highly dependent on the applied acoustic frequency and inversely proportional to the distance between acoustic transmitters. the output voltages and power generated from the vibrating piezocantilever are measured using the custom-made electrical circuit with different electric loads. furthermore, the effect of multiple piezocantilevers on the electric energy density is investigated to demonstrate the possibility of improving the electric energy density. this actuation technique is a simple but useful tool for energy scavenging and for potential acoustic wave sensors and actuators. |
Tuesday, November 22, 2022 8:26AM - 8:39AM |
U09.00003: Coalescence of drug-carrier microbubbles Berenice Pérez Cacho, Gabriel A Caballero Robledo Microbubbles can be used for targeted therapy. This novel application requires enhancing their response to ultrasound waves. Bubbles with the same composition will have the same response to the ultrasound if they have monodisperse size distribution. The fabrication of monodisperse microbubbles is achieved using microfluidic devices. However, these bubbles can be difficult to collect and usually have short lifespans. Segers et al. [Lab chip 19, 158-167 (2019)] recently constructed a model describing the coalescence probability of bubbles with only-lipid membranes produced in flow-focusing devices. They proved that temperature, lipid concentration, and the amount of pegylated lipids alter the coalescence probability. In this work, we study the coalescence of bubbles when drug molecules are added to their membrane. |
Tuesday, November 22, 2022 8:39AM - 8:52AM |
U09.00004: Acoustic vaporization of droplet aggregations Anunay Prasanna, Samuele Fiorini, Gazendra Shakya, Outi Supponen Acoustic Droplet Vaporization (ADV) is a phenomenon wherein micron- and sub-micron-sized droplets are vaporized into microbubbles upon exposure to high-frequency ultrasound. This process can be used to improve the contrast in medical ultrasound imaging and for targeted drug delivery in the human body. Here, we investigate droplet aggregations as a way to reduce the acoustic pressure required to achieve ADV compared to single droplets. We perform experiments on different droplet aggregations using ultra-high-speed video-microscopy to temporally resolve their vaporization dynamics upon acoustic excitation. The phenomenon discloses rich dynamics – from the nucleation of micro-cavitation in a specific droplet within the aggregation to the full vaporization of the droplets. We compare the dynamics of aggregations to those of individual droplets and discuss their implications in reducing the vaporization threshold of ADV. |
Tuesday, November 22, 2022 8:52AM - 9:05AM |
U09.00005: Numerical Simulations of Ablation Mechanisms during Focused Ultrasound Therapies Jean-Sebastien A Spratt, Mauro Rodriguez, Spencer H Bryngelson, Tim Colonius Focused ultrasound therapies such as histrotripsy or burst-wave lithotrispy are promising techniques for non-invasive stone comminution and tissue erosion. Such treatments effectively deliver acoustic energy to a target (such as renal calculi) inside the body with limited impact on surrounding tissue. They involve two important ablation mechanisms. First, the focused ultrasound itself can cause high stresses in the target, particularly as it resonates across a stone. Second, the acoustic energy can cause cavitation bubbles to form near the target, the violent collapse of which induces stone or tissue ablation. Our implementation of a hypoelastic material model in the open-source Multi-component Flow Code (MFC) enables the simulation of each mechanism by modeling the elastic response of stones along with the background fluid dynamics. Simulations of the stresses generated in stones due to focused ultrasound waves and the collapse of bubbles that form near the surface help elucidate the relative impact of each mechanism. To understand this relative impact, we present high resolution simulations of acoustic wave-bubble-elastic solid interactions, enabled by the GPU implementation of the code. |
Tuesday, November 22, 2022 9:05AM - 9:18AM |
U09.00006: HIFU-induced cavitation bubble cloud dynamics and its role in model kidney stone erosion Luc Biasiori-Poulanges, Claire Bourquard, Bratislav Lukic, Ludovic Broche, Outi Supponen Cavitation bubble clouds generated by high-intensity focused ultrasound (HIFU) contribute to non-invasive clinical procedures to erode bodily tissues up to ablation. Independently of the ultrasound energy, the role of the bubble clouds themselves in the erosion process is not clear, and the physics governing the cloud dynamics remains elusive. We herein present experiments of the bubble cloud dynamics under HIFU in (i) a boundary-free environment, and (ii) with a stone in the focal region of the ultrasonic transducer. In both cases, intricate time-dependent cloud morphologies are reported. This partially results from the convergence and merging of sub-clouds under the acoustic forces. In the absence of a stone, the monotonic trajectories of the clouds are enveloped within the ultrasound beam. The presence of a stone in the focal region however generates a standing wave which modifies the canonical cloud trajectories observed. When cavitating close enough to the focal region, clouds violently hit the stone and hammer the surface. This results in a suspended layer of fragments that experiences a gravity-driven instability once the ultrasound is turned off. These results are supported with high-speed conventional and X-ray imaging, as well as microscopy of the damaged stones. |
Tuesday, November 22, 2022 9:18AM - 9:31AM |
U09.00007: Prediction for the bubble dissolution rate in a protein solution Xiaoxu Zhong, Arezoo M Ardekani We have developed a model for the bubble dynamics in a protein solution. We model the protein-coated bubble surface as a linear viscoelastic interface, and we use the case of bubble dissolution due to gas diffusion to highlight the importance of the surface excess stress. |
Tuesday, November 22, 2022 9:31AM - 9:44AM |
U09.00008: Maximum Radius of an Explosively Growing Bubble in a Viscoelastic Medium Subjected to an Ultrasound Wave Baudouin Fonkwa Kamga, Minki Kim, Eric Johnsen The potential of cavitation damage can be harnessed to create local and precise destruction of biological tissues. Applications of this principle include histotripsy, in which cavitation bubbles are created thanks to focused megahertz and megapascal pressure pulses. Once created, these bubbles collapse inertially and induce stresses that mechanically homogenize tissue. When designing a histotripsy device, one important parameter to control is the size of the region targeted, which may be related to the maximum radius of a growing cavitation bubble in the specified medium. In this study, we wish to obtain a scaling law between the maximum radius of the bubble and other parameters of the problem. Previous studies have undertaken this task, but for a Newtonian liquid and with limited results. The novelty of our approach is the inclusion of an elastic term, representative of the medium viscoelastic behavior. To derive our scaling law, we rely on the Keller-Miksis equation, coupled with thermal equations inside and outside the bubble, and on energy budget analysis. We simplify our analysis by considering an idealized waveform for the pressure where the bell curve is replaced by a negative rectangular function. This is referred to as a negative-top hat pulse. Our results show that the elasticity of the medium reduces the maximum radius, as we could expect. Our scaling law agrees well with simulations. However, we observe some discrepancies as the elasticity increases, when considering realistic pressure pulses. |
Tuesday, November 22, 2022 9:44AM - 9:57AM |
U09.00009: Investigation of Microbubble Dynamics under Acoustic Field Ilke Kaykanat, Kerem Uguz Ultrasound has been used for various applications, including the ultrasound-focused break up of urinary stones, diagnostic imaging, Ménière’s disease, and Parkinson’s disease. Recent advancement in ultrasound is in using microbubble oscillation to enhance the effect of the drug in chemotherapy. Since compressibility of a bubble is large, the bubble oscillates in accordance with ultrasound. The oscillation of the intravascular microbubbles increases the permeability of endothelium, thus increasing the drug uptake to the target site. In this study, the dynamic of a bubble in a non-Newtonian power-law fluid confined within an elastic solid is investigated to understand the microbubble behavior in a blood vessel. An external acoustic field is applied to the elastic confinement to obtain volume oscillations. The effects of the frequency and the peak negative pressure of the acoustic field, the power-law index, the confinement size, and the bulk modulus are studied. |
Tuesday, November 22, 2022 9:57AM - 10:10AM |
U09.00010: Cavitation inception on biological cells Anna Borich, Claus-Dieter Ohl Cavitation is well established in medical therapy, e.g. for renal stones lithotripsy, removal of blood clots, HIFU, histotripsy, embolotherapy, and more recently even for targeted cell drug delivery. The interaction of cavitation with cells, the extra-cellular matrix, and tissue is well understood and mostly caused by mechanical forces. Yet, the origin of cavitation in medical therapy is an open problem, which is addressed in this presentation. |
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