Bulletin of the American Physical Society
74th Annual Meeting of the APS Division of Fluid Dynamics
Volume 66, Number 17
Sunday–Tuesday, November 21–23, 2021; Phoenix Convention Center, Phoenix, Arizona
Session M11: Microscale Flows: General & Microscale Flows: Devices |
Hide Abstracts |
Chair: Burt Tilley, WPI Room: North 125 AB |
Monday, November 22, 2021 1:10PM - 1:23PM |
M11.00001: Buoyancy-driven co-flow of miscible solutions in a microchannel Niki Abbasi, Janine K. Nunes, Zehao Pan, Tejas Dethe, Andrej Kosmrlj, Howard A Stone Buoyancy-driven flows are ubiquitous and have been studied extensively in traditional lock-exchange configurations. Within the past decade, with the rise of lab-on-a-chip devices, buoyancy-driven co-flows of miscible solutions, with similar viscosities, have been studied. Here, we experimentally study the buoyancy-driven co-flow of two miscible liquids, with a viscosity contrast, in a flow-focusing microchannel. Poly(ethylene glycol) (PEG) solution is introduced as the inner stream, and water is flowed as the outer stream. By performing confocal microscopy at different positions in the microchannel, we observe the evolution of the moving fronts of the two fluids on the walls of the device. Water, the less dense fluid, spreads across the top wall of the channel as the fluid moves downstream in the channel, while the denser fluid, the PEG solution, spreads across the bottom wall of the device. We quantify the motion of the moving front of both fluids, by tuning the flowrate of each phase and the density difference between the two fluids (which results in changes in the viscosity ratio between the two fluids). We further quantify the normalized width of the moving fronts, using an appropriate two-phase flow description, based on the ratio of the convective to the buoyancy time scales within this system. We observe the raw data from the experiments collapse onto a line. We anticipate that buoyancy-driven co-flows within microchannels may have important implications for design and operation of lab-on-a-chip devices. |
Monday, November 22, 2021 1:23PM - 1:36PM |
M11.00002: Microextensional Rheology for Small Volume or Expensive Biological Sample Analysis John Hollister, Helia Hosseini, Mercedes Rodriguez, Jean-Pierre Hubschman, Pirouz Kavehpour One of the methods to study microstructure of complex fluids is rheology. In general, rheological analysis requires relatively large volume samples to analyze meaningful characteristics. Many biological materials, however, do not naturally occur or are prohibitively expensive to produce in these requisite large volumes. Vitreous humor samples are small volumes available per specimen, and certain protein solutions, such as Tau protein, are very expensive to purchase ($10,000 per ml). Therefore, a method to perform complex analysis on small-volume biological samples is crucial to the growing field of micro-extensional rheology. Using a commercial tensiometer to induce an extensional flow and a high speed camera to capture the evolution of the fluid structures, we developed a technique that is capable of measuring important characteristics of biological samples such as extensional relaxation time and extensional viscosity with volumes less than 100 microliters. To demonstrate the effectiveness of this technique, we analyzed the relaxation times and extensional viscosity of several biological samples and have shown promising results. In addition, we were able to capture rheological properties of dilute polymer solutions using this technique, while shear rheology tests did not yield such results. |
Monday, November 22, 2021 1:36PM - 1:49PM |
M11.00003: On gaseous coolants in porous ceramic electromagnetic absorbers: thermal runaway vs Joule-Thompson cooling at the microscale Ajit Mohekar, Burt S Tilley, Vadim V Yakovlev An electromagnetic (EM) heat exchanger (HX) absorbs EM waves in high-power beaming applications and converts the internal energy to mechanical work. One design of an EM HX consists of a porous ceramic which is heated by EM waves, and a gaseous coolant flowing through the pores transfers the dissipated thermal power to the outlet. A nonlinear phenomenon associated with EM heating of ceramics with a temperature-dependent loss factor is thermal runaway—slight increase in the applied power causes significant rise of temperature (up to 2000K). Designing such an EM HX requires understanding of the coupling between compressible gas dynamics and thermal runaway at the pore-scale. To study the microscale phenomena, we consider a 2D thin and long EM HX, consisting of a single channel with an ideal compressible gas coolant in perfect thermal contact with a thin solid ceramic layer. We apply lubrication theory to derive the averaged conservations laws and solve the system numerically in MATLAB. We find that Joule-Thompson cooling occurs locally when work of expansion done by the gas dominates over the net heat added to the system. Finally, parametric studies on Péclet and bearing numbers are carried out to determine critical conditions for the onset of Joule-Thompson cooling within the gas. |
Monday, November 22, 2021 1:49PM - 2:02PM |
M11.00004: Reduced models for analyzing flow instability in compliant rectangular microchannels Xiaojia Wang, Ivan C Christov Fluids conveyed in deformable conduits are often encountered in microfluidic applications, which makes fluid--structure interactions (FSIs) an inherent feature of these systems. Previous experiments reported the existence of FSI-induced instabilities in microchannel flows at low Reynolds number (Re). This observation suggests new strategies to enhance mixing at the microscale, where mixing is diffusion limited. To provide new understanding of these phenomena, we formulate an unsteady reduced model of flow in a long, shallow rectangular microchannel with a compliant top wall. Based on previous work, the slenderness of the compliant channel gives rise to a Winkler-foundation-like behavior of the fluid--solid interface; i.e., the interface deformation is fully determined by the local pressure. To apply this idea to flow stability, we first spanwise average the deformed channel. Second, to regularize the model, we introduce weak tension, which enables satisfaction of the displacement constraints along the edges of the channel. Third, the deformed channel height is introduced into a cross-sectionally averaged 1D flow model, which is obtained from the Navier--Stokes equations, keeping leading-order terms in Re ≠ 0. The steady response of the resulting reduced model is analyzed, and the global linear stability of the inflated base state is determined. It is shown that, for specific combination of the model's parameters, the base state is linearly unstable. Numerical simulations of the reduced model show that the unstable cases correspond to self-sustained oscillations of the channel wall. The proposed model can be useful for understanding flow instabilities observed in microchannels at Re as low as 200-300. |
Monday, November 22, 2021 2:02PM - 2:15PM |
M11.00005: The role of sharp turns in inertial particle focusing in the microfluidic labyrinth chip Anirudh Gangadhar, Siva A Vanapalli, Eric Lin, Sunitha Nagrath We investigated inertial, size-based focusing of particles in the microfluidic labyrinth device which consists of several sharp turns in addition to circular loops. Experiments were conducted over a range of fluid Reynolds number 125 ≤ Ref ≤ 417 and particle sizes and the results were compared to focusing in spiral channels. At a given particle size, we observe that focusing occurs at a higher critical Dean number De* in the labyrinth compared to spiral channels, except at Ref = 417. Moreover, focusing occurs at higher De* for larger particles in labyrinth, except at Ref = 417. CFD simulations showed a dominant corner vortex at Ref = 417 which could be the source of this deviation. In general, we find that the presence of a corner vortex increases the local radius of streamline curvature making particles to focus at a lower De*. Additionally, we measured the focusing length Lf to test the hypothesis that sharp turns help in focusing smaller particles. Across all Ref, Lf was found to vary inversely with particle size. At Ref = 125, only the smaller 7 and 12 µm particles focused at a significantly lower Lf as compared to the spiral. At all other Ref, we did not observe this reduction in Lf for any of the particle sizes tested. |
Monday, November 22, 2021 2:15PM - 2:28PM |
M11.00006: An in-vitro living system for flow rectification Mattia Gazzola, Fan Kiat Chan, Liu Hong, Zhengwei Li, Yashraj R Bhosale, Zhi Dou, Onur Aydin, Taher Saif, Leonardo P Chamorro Conventional applications using viscous streaming overwhelmingly utilize classically understood bodies that are rigid and of simple shape and topology, offering limited opportunities for flow manipulation. Taking advantage of recent computational insights into body-topology effects on streaming flows, and biofabrication advances, we present the first in-vitro realization of a living biological muscle ring able to elicit complex rectified flows. Using a synergistic experimental and numerical approach, we characterize this flow response to identify the distinct footprint of viscous streaming. This streaming system marks a significant milestone towards the design and fabrication of independent, self-sustained, active, and biocompatible entities capable of flow manipulation at the microscale, opening avenues for transport, mixing, and trapping across a spectrum of applications, from engineering to medicine. |
Monday, November 22, 2021 2:28PM - 2:41PM |
M11.00007: Rectified flow-mediated transport in bio-hybrid settings Fan Kiat Chan, Yashraj R Bhosale, Mattia Gazzola Motivated by drug-delivery applications and recent advances in bio-hybrid engineering, we present a torus-shaped, bio-compatible muscle ring operating in Stokes-like flows. Muscle ring contractions set up a rectified viscous streaming flow, which we confirm via direct numerical simulations. Leveraging this streaming response, we explore in-silico the capability of this system to perform contactless payload delivery and particle manipulations, demonstrating its robustness across a range of conditions. Comparison against results without muscle actuation further confirms that viscous streaming is indeed the dominant mechanism at play. |
Monday, November 22, 2021 2:41PM - 2:54PM |
M11.00008: Affordable portable manufacturing of microfluidic mixers and separators through tunable sacrificial layer morphologies Jack D Johnson, Huy Tran, Min Y Pack Microfluidic devices have the ability to let humans see and test a variety of chemicals and cells to mix and separate for medical and biological applications. These applications include drug administration, cell analysis on a micro scale, and can help diagnose or detect diseases. However, due to the massive costs and inefficiencies of such devices, microfluidic devices can be hard and costly to manufacture. This project aims to provide an alternative to manufacturing effective, efficient, and repeatable devices at a low expenditure. We use a sacrificial layer of gelatin dispensed from a custom made inkjet printer on a heated substrate. This process is designed to create reusable mixers and separators for these previously mentioned applications at an affordable price. By creating an affordable way to produce separators and mixers, we hope to provide the scientific community the means to expand their applicative research with the use of this process to create cheap and effective microfluidic devices. |
Monday, November 22, 2021 2:54PM - 3:07PM |
M11.00009: Optimizing the closing time of telescoping cardboard boxes Kaare Hartvig Jensen, Jolet De Ruiter, Sean Marker, Emil Østergaard The economics, environmental impact, and mechanical properties of paper-based storage containers have been widely studied. However, knowledge of the physical processes relevant to the end-user experience is unavailable. This presentation outlines the main effects associated with the closing and opening of telescoping boxes which are used, for instance, to store and transport board games, footwear, mobile phones, and tablet computers. The sliding motion of the lid is controlled by flow in a thin film of air in the gap separating the lid and the base of the box. Based on a broad comparison between theory and experiments on real and synthetic boxes, we find that the process is primarily controlled by the shape of the gap between the base and the lid. Three distinct experimental regimes are observed, and an optimal design for a rapidly closing box is identified. |
Monday, November 22, 2021 3:07PM - 3:20PM |
M11.00010: Looped DNA: supercoiling dependent shape and hydrodynamics Radost Waszkiewicz, Maciej Lisicki, Daniel J Catanese, Jonathan Fogg, Magdalena Gruziel-Słomka, Maria L Ekiel-Jezewska, Borries Demeler, Maduni Ranasinghe, E. Lynn Zechiedrich, Piotr Szymczak Circularized DNA molecules behave differently than short linear segments of DNA, as they are unable to relax the entire torsional stress. Such conditions are of biological interest, but they can be challenging, as DNA can buckle, if the stress is sufficiently high. |
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