Bulletin of the American Physical Society
67th Annual Meeting of the APS Division of Fluid Dynamics
Volume 59, Number 20
Sunday–Tuesday, November 23–25, 2014; San Francisco, California
Session E10: Microscale Flows: Formation and Dynamics of Drops |
Hide Abstracts |
Chair: Sindy Tang, Stanford University Room: 3005 |
Sunday, November 23, 2014 4:45PM - 4:58PM |
E10.00001: Confined microbubbles at high capillary numbers Martin Sauzade, Thomas Cubaud We experimentally investigate the flow behavior of bubbles in highly viscous silicone oils within various microgeometries. A square focusing section is used to examine the bubble generation process at large capillary numbers. We notably vary the continuous phase viscosity from 1 to 10,000 cS and study the dynamics of interfacial cusps during bubble pinch-off. The resulting segmented flows are then scrutinized in straight microchannels for both dissolving and non-dissolving bubbles. Finally, we examine the motion of bubbles in periodically constricted microchannels over a wide range of flow conditions. Our findings highlight the possibility to control and exploit the interplay between capillary and mass transfer phenomena with highly viscous fluids in microsystems. [Preview Abstract] |
Sunday, November 23, 2014 4:58PM - 5:11PM |
E10.00002: Flow regime and dynamic critical pressure of droplet entering confined microchannel Zhifeng Zhang, Jie Xu, Xiaolin Chen Droplet entering a microchannel contraction is a phenomenon widely seen in many applications, such as two phase separation, droplet microfluidics, size-based cancer cell detection, and micro combustors. Better understanding of the droplet flow regime as well as the droplet deformation pattern is crucial to device design in aforementioned applications. In present numerical study, we explore the transient behavior of droplet being squeezed into a micro-contraction and we report different flow regimes observed according to the blockage status of the droplet in the entrance of the contraction. We then quantify the relation between droplet deformation, back pressure and the flow velocity in the channel. In the end, we explore the effects of channel geometry by comparing the results in three different shapes of channels (circular square and rectangular). [Preview Abstract] |
Sunday, November 23, 2014 5:11PM - 5:24PM |
E10.00003: Picoliter Droplets of Controlled Composition for SERS Studies Chrysafis Andreou, Martin Moskovits, Carl Meinhart Generation of picoliter scale droplets of specified composition is a valuable tool for chemical analysis and synthesis, with many bioanalytical lab-on-chip applications. Here we present a microfluidic droplet generator that creates water-in-oil droplets of picoliter volume, by merging two laminar aqueous streams immediately before the droplet-generating junction. We use this device to investigate the dependence of surface enhanced Raman spectroscopic signal on the availability of silver nanoparticles, and analyte. By controlling the composition of the generated droplets, we can limit the availability of plasmonic nanoparticles and analyte molecules with unprecedented accuracy. Experiments, as well as numerical simulations, are used to investigate the plasmonic enhancement stemming from small numbers of silver nanoparticles confined within the droplets. [Preview Abstract] |
Sunday, November 23, 2014 5:24PM - 5:37PM |
E10.00004: Exploiting droplet formation in microfluidic devices to create functional particles Emilia Nowak, Mark Simmons Microfluidic devices offer excellent capabilities for the formation of microstructured particles which have functional attributes e.g. in controlled delivery of pharmaceuticals, enhanced nutrition and flavours in food. In this work, a microfluidic device is employed to form microstructured particles in two steps: (i) by formation of single/double emulsions and (ii) solidification of the droplet by either gelation or solvent evaporation. Both may impart non-Newtonian properties to the component phases. The influence of phase flow rates (capillary number), surfactant type/concentration and the rheology of the component phases upon the particle formation and hydrodynamic behaviour are described. [Preview Abstract] |
Sunday, November 23, 2014 5:37PM - 5:50PM |
E10.00005: Dynamics of jet breakup induced by perturbation Ho Cheung Shum, Jingmei Li, Sze Yi Mak We study the breakup of jet to form droplets, as induced by controlled perturbation, in a microchannel. Controlled mechanical perturbation is introduced to the tubing through which the jet phase is injected into the device, which is monitored under high-speed optical imaging. We measure the frequency of droplet formation and the sizes of the droplets as the frequency and amplitude of the perturbation is varied. Droplets can be induced to form at the perturbation frequency only above a critical frequency and amplitude. In this manner, the droplet size can be precisely controlled. The amplitude needed to induce breakup decreases as the interfacial tension of the system is lowered. Moreover, by selectively varying the wettability of the inner wall of the channel, double emulsion droplets can be generated in one step by applying large-amplitude perturbation of the jet phase. Our work demonstrates the potential of using controlled perturbation to generate droplets with tunable size and shapes, with implications on new designs of liquid dispensing nozzles. [Preview Abstract] |
Sunday, November 23, 2014 5:50PM - 6:03PM |
E10.00006: Dynamics of soft interfaces in droplet-based microfluidics Quentin Brosseau, Ingmar Polenz, Jean-Christophe Baret The numerous applications of microfluidic emulsions (i.e compartmentalisation) rely on both the short and long term stabilization of droplet interfaces. This is achieved mainly via the addition of surfactant or the formation of a rigid capsule. Therefore in order to predict and control the stability of the emulsions, a precise control of the interfaces modified in this way is required. In this talk, I present a microfluidic method for the characterisation of the dynamic properties of complex soft interfaces. Monodisperse droplets with controlled interfaces are produced at a flow focusing junction and deformed in sudden planar expansions. The deformation of the droplets is then analysed at different interface ages, allowing us to follow the dynamics of two processes occurring at the interface. First, the evolution of the interfacial tension, from which we extract the surfactant adsorption kinetics for small time and length scales. Secondly, the in-situ kinetics of a interfacial polymerization reaction permitting us to determine the mechanical properties of the resulting polymer shell and encapsulated droplet. [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