Bulletin of the American Physical Society
65th Annual Meeting of the APS Division of Fluid Dynamics
Volume 57, Number 17
Sunday–Tuesday, November 18–20, 2012; San Diego, California
Session L11: Bubbles IV and Drug Delivery |
Hide Abstracts |
Chair: Kausik Sarkar, George Washington University Room: 26A |
Monday, November 19, 2012 3:35PM - 3:48PM |
L11.00001: Simulation of Magnetic Particles in the Bloodstream for Magnetic Drug Targeting Applications Erica Cherry, John Eaton Magnetic Drug Targeting (MDT) is a promising new idea for treatment of cancer and other well-localized diseases. An ideal MDT treatment would involve chemically binding the drug particles to magnetic particles, injecting them into the body, and using external magnetic fields to steer the particles towards or hold them near areas of diseased tissue not accessible via injection. However, it would be difficult to implement efficient MDT treatments because we know little about how magnetic particles interact with blood flow. With the goal of understanding these dynamics, a simulation of blood flow containing magnetic particles was performed. The particles were subject to a variety of forces such as gravity, externally-applied magnetic force, and inter-particle magnetic force. A separate simulation was performed to determine how the magnetic particle dispersion coefficient varied with flow properties such as shear and erythrocyte content, and the results of the dispersion simulation were used in the main simulation. Results from these simulations will be presented and used to draw conclusions about the technology required for a successful MDT treatment. [Preview Abstract] |
Monday, November 19, 2012 3:48PM - 4:01PM |
L11.00002: Highly-focused high-speed impact on soft material: Application for needle-free injection device Yoshiyuki Tagawa, Nikolai Oudalov, Claas Willem Visser, Chao Sun, Detlef Lohse The development of needle-free drug injection systems is of great importance to global healthcare. Existing methods use diffusive jets, which suffer from insufficient penetration into the skin. We established a novel method of creating microjets with a very sharp geometry and controlled velocities even for supersonic speeds up to 850 m/s. In this presentation we demonstrate that it is possible to penetrate human skin using these jets and in this way deliver liquid substances to the human body. The penetration depth is much deeper than those of conventional methods. Further penetration dynamics is studied through experiments performed on gelatin mixtures. A model based on Stokes-like drag is proposed to predict the depth of the penetration. [Preview Abstract] |
Monday, November 19, 2012 4:01PM - 4:14PM |
L11.00003: Mapping the acoustic scattering behavior of spherical microbubble clouds Miguel A. Parrales, Juan M. Fernandez, Miguel Perez-Saborid Sound scattering and acoustic propagation through bubbly liquids have been studied deeply in the last decades. The main reason for these studies was to explain and analyze the high impact of gas bubbles on sound propagation: the compressibility missmatch and the resonant behavior make the bubble a very efficient sound scatterer, changing appreciably the acoustic properties of the biphasic medium. Here we propose a numerical analysis, based on the self-consistant multiple scattering approach, to compute the linear acoustic response of spherical microbubble clouds while excited by an external ultrasonic wave. The calculations have been done for a wide range of the cloud void fraction $\beta$. By varying the excitation frequency $\omega_o$, we are able to map the total scattering intensity from the cloud in a $(\beta-\omega_o)$ phase space. The localization of the collective resonant modes on this map finally reveals the different scattering regimes. Furthermore, the total pressure field is obtained both inside and outside the cloud, being possible to visualize the acoustic wave propagation in each scattering regime. [Preview Abstract] |
Monday, November 19, 2012 4:14PM - 4:27PM |
L11.00004: Acoustic Excitation of a Micro-bubble Inside a Rigid Tube Adnan Qamar, Ravi Samtaney A theoretical model for acoustic excitation of a single micro-bubble inside a rigid tube is proposed in the present work. The model is derived from the reduced Navier-Stokes equations and by utilizing Poiseuille pipe flow theory. Wall Frictional losses induced due to fluid motion by the bubble oscillation in response to the acoustic perturbation are taken into account. The proposed model is not a variant of conventional Rayleigh-Plesset (RP) equation and is principally a super-set of all the conventional RP models. The model is first of its kind, which relates the bubble dynamics with the tube geometric and acoustic parameters in a consistent manner. Model predicts bubble oscillation dynamics as well as bubble fragmentation quite well when compared to the available experimental data. Results are computed for three tube diameters of 200, 100 and 12 microns with two initial bubble radiuses of 1.5 and 2 microns. The response of micro-bubble is highly non-linear with the driving acoustic frequency. Bubble response for low acoustic peak negative pressure (PNP) is linear, whereas as the PNP is increase nonlinearity are manifested and eventually bubble fragmentation takes place. For fixed acoustic parameters, an exponential decay in bubble response is observed as the tube length is increased. For very small tube diameters, the predictions are damped, suggesting the breakdown of the inherent model assumptions for these cases. [Preview Abstract] |
Monday, November 19, 2012 4:27PM - 4:40PM |
L11.00005: Stably Levitated Large Bubbles in Vertically Vibrating Liquids Timothy O'Hern, Bion Shelden, Louis Romero, John Torczynski Vertical vibration of a liquid can cause small gas bubbles to move downward against the buoyancy force. Downward bubble motion is caused by the oscillating bubble volume (induced by the oscillating pressure field) interacting with the bubble drag force. The volume-drag asymmetry and the oscillating pressure gradient produce net downward bubble motion analogous to that caused by the Bjerknes force in high-frequency vibrations. Low-frequency (below 300 Hz) experiments demonstrate downward bubble motion over a range of vibration conditions, liquid properties, and pressure in the air above the free surface. Small bubbles deep in a quasi-two-dimensional test cell usually coalesce to form a much larger bubble that is stably levitated well below the free surface. The size and position of this levitated bubble can be controlled by varying the vibration conditions. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
Monday, November 19, 2012 4:40PM - 4:53PM |
L11.00006: Nonlinear dynamics of PLA (poly-lactic acid) encapsulated ultrasound contrast microbubbles Shirshendu Paul, Kausik Sarkar, Margaret Wheatley The presence of the stabilizing encapsulation in microbubble based ultrasound contrast agents (UCAs) has critical effects on their acoustic properties. Biodegradable polymers like poly-lactic acid (PLA) hold promises to provide better stability and control over properties. Here, we report determination of interfacial rheological properties of PLA microbubbles using\textit{ in vitro }experiments and investigation of their non-linear scattering response. The average bubble size measured using DLS is 1.8 $\mu $m. However, the attenuation measured through a suspension of PLA bubbles shows a peak between 2.5-3.2 MHz, much smaller than the resonance frequency of a free bubble of similar size. This observation is explained by an extremely low surface elasticity (0.02-0.06 N/m) and the polydispersity of the bubble population. The estimated properties lead to an excellent agreement between model prediction and the experimentally measured response (up to 30 dB enhancement of fundamental response). Subharmonic threshold prediction is shown to be critically dependent on the bubble size distribution. [Preview Abstract] |
Monday, November 19, 2012 4:53PM - 5:06PM |
L11.00007: Microbubbles as drug-delivery vectors: steering ultrasound contrast agents in arterial flow using the Bjerknes force Alberto Aliseda, Alicia Clark Micron-sized coated microbubbles, commonly referred to as ultrasound contrast agents (UCAs), have been identified as potential targeted drug delivery vectors with applications in cancer chemotherapy and thrombolysis. The Bjerknes force, produced by the fluctuating pressure field created by the ultrasound waves acting on the oscillating bubble with a phase lag induced by the liquid's inertia and viscosity, can be used to direct the microbubbles to specific targeted areas in the circulatory system. While this phenomenon is well understood in a quiescent fluid, we need a better understanding of the dynamics of microbubbles in the complex pulsatile flow found in the human circulatory system. The non-linear interactions of ultrasound volume oscillations and flow-induced stresses are explored via high speed imaging of UCAs under in vitro flow that reproduces conditions in large arteries (relatively high Reynolds and Womersley numbers). This improved understanding will be used to manipulate and steer UCAs with ultrasound, in conjunction with hydrodynamic forces. [Preview Abstract] |
Monday, November 19, 2012 5:06PM - 5:19PM |
L11.00008: The Short Time Scale Events of Acoustic Droplet Vaporization David S. Li, Oliver D. Kripfgans, J. Brian Fowlkes, Joseph L. Bull The conversion of a liquid microdroplets to gas bubbles initiated by an acoustic pulse, known as acoustic droplet vaporization (ADV), has been proposed as a method to selectively generate gas emboli for therapeutic purposes (gas embolotherapy), specifically for vascularized tumors. In this study we focused on the first 10 microseconds of the ADV process, namely the gas nucleation site formation and bubble evolution. BSA encapsulated dodecafluoropentane (CAS: 678--26--2) microdroplets were isolated at the bottom of a degassed water bath held at 37\r{ }C. Microdroplets, diameters ranging from 5-65 microns, were vaporized using a single pulse (4-16 cycles) from a 7.5 MHz focused single element transducer ranging from 2-5 MPa peak negative pressure and images of the vaporization process were recorded using an ultra-high speed camera (SIM802, Specialised Imaging Ltd). It was observed that typically two gas nuclei were formed in series with one another on axis with ultrasound pulse. However, relative positioning of the nucleation sites within the droplet depended on droplet diameter. Additionally, depending on acoustic parameters the bubble could deform into a toroidal shape. Such dynamics could suggest acoustic parameters that may result in tissue damage. [Preview Abstract] |
Monday, November 19, 2012 5:19PM - 5:32PM |
L11.00009: An Experimental Review on Microbubble Generation to Be Used in Echo-PIV Method to Determine the Pipe Flow Velocity Alinaghi Salari, Mohammad Behshad Shafii, Shapoor Shirani Today microbubbles are broadly used as ultrasound contrast agents. Flow Focusing (FF) in microchannels can pave the way for the generation of same size bubbles. Microbubbles can be used as tracers in the Echo Particle Image Velocimetry (Echo-PIV) method to determine the velocity profile in main body vessels such as carotid. In this paper we use a low-cost microchannel fabrication method for preparing microbubble contrast agents by using some surface active agents and a viscosity enhancing material to obtain appropriate microbubbles with desired lifetime and stability for any \textit{in vitro }infusion for velocity measurement. All the five parameters that govern the bubble size extract and some efforts are done to achieve the smallest bubbles by adding suitable surfactant concentrations. By using these microbubbles for the Echo-PIV method, we experimentally determine the velocity field of two flow types, namely steady state and pulsatile pipe flows. [Preview Abstract] |
Monday, November 19, 2012 5:32PM - 5:45PM |
L11.00010: Development of microbubbles generator using microchannel toward biomedical applications Hironobu Kaji, Rei Masuda, Kazuhito Inoue, Mitsuhisa Ichiyanagi, Ikuya Kinefuchi, Shu Takagi, Yoichiro Matumoto Microbubbles have been already used as ultrasound contrast agents to visualize microcirculation system. They are also expected to be used for the drag delivery agent. For these bubbles, important requirements are their size and functionality such as carrying drugs and staying stability in vivo. Aiming at the development of microbubbles with the well-controlled size and functions, we have been developing a microbubble generation system using microchannels. Advantages of the method using microchannels are to generate small- and monodisperse-size microbubbles with the wide variety of choice in both liquid phase and gas phase and the capability of surface coating. In the present study, microbubbles are generated using T-junction type microchannel. We have designed the channel shape to reduce the bubble size. The improvement of the shape has enabled us to generate the smaller microbubble whose diameter is 6.1$\mu $m. Moreover, the effect of the viscosity in the liquid phase are investigated and it is confirmed that smaller bubbles are generated with the increase of viscosity. In addition, we have developed a new type microchannel for the surface coating of a microbubble. The results will be discussed in the presentation. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700