Bulletin of the American Physical Society
69th Annual Meeting of the APS Division of Fluid Dynamics
Volume 61, Number 20
Sunday–Tuesday, November 20–22, 2016; Portland, Oregon
Session L22: Microscale Flows: Microfluidic Devices |
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Chair: Ivan C. Christov, Purdue University Room: E141/142 |
Monday, November 21, 2016 4:30PM - 4:43PM |
L22.00001: Modeling fluid--structure interactions in shallow microchannels Tanmay C. Shidhore, Ivan C. Christov Rectangular microfluidic conduits with deformable walls are some of the simplest and most extensively studied microfluidic devices, primarily due to their practical design applications in a variety of fields like biology, medical diagnostics (e.g., lab-on-a-chip), nanotechnology, etc. Experimentally, these devices are found to deform into a non-rectangular cross-section due to fluid--structure interactions occurring at the channel walls. These deformations significantly affect the flow profile, which results in a non-linear relationship between the flow rate and the pressure drop, which cannot be explained by a `generalised Poiseuille flow solution'. To this end, we perform a numerical study of these fluid--structure interactions and their effect on the flow rate and the pressure drop occurring in microfluidic conduits with a single deformable wall. The behavior of several shallow conduit systems ($\ell\gg w\gg h$) with rigid base and side walls and a soft top wall (e.g., PDMS) is simulated under laminar flow conditions using the commercial software suite ANSYS. Simulation results are compared against experimental pressure drop--flow rate data from the literature and also newly developed analytical expressions for the wall deformation, the pressure and the normalized flow rate. [Preview Abstract] |
Monday, November 21, 2016 4:43PM - 4:56PM |
L22.00002: Evaluation of strategies for size based separation of polydisperse vesicle suspensions Kari J. Storslett, Susan J. Muller Microfluidic devices can be used to separate suspensions of deformable particles with different intrinsic characteristics (e.g. size) with reasonable throughputs and without external labeling. Using vesicle suspensions to test microfluidic separation schemes provides insight into cell separation. Two schemes for separating vesicle suspensions by size are discussed: filtration and inertial focusing. The filter physically prevents most large vesicles from passing through. The filtrate is collected at one outlet and the larger vesicles are collected at another. This device showed good size separation between the two collected suspensions and was able to reduce the polydispersity of the collected suspensions relative to the original suspension. The inertial separation device was based on a design studied by Di Carlo et al$^{\mathrm{1}}$. This design was modified for our suspension and showed an ability to separate the suspension by size; however, the separated suspension's polydispersity was only slightly reduced. The advantage of the inertial separation device was its greatly increased throughput. A separation strategy may be selected based on the relative importance of high throughput vs. reduced polydispersity. (1) Di Carlo, D. et al. \textit{Anal. Chem.} \textbf{2008}, \textit{80}, 2204-2211. [Preview Abstract] |
Monday, November 21, 2016 4:56PM - 5:09PM |
L22.00003: Continuous high throughput molecular adhesion based cell sorting using ridged microchannels. Bushra Tasadduq, Gonghao Wang, Alexander Alexeev, Ali Fatih Sarioglu, Todd Sulchek Cell molecular interactions govern important physiological processes such as stem cell homing, inflammation and cancer metastasis. But due to a lack of effective separation technologies selective to these interactions it is challenging to specifically sort cells. Other label free separation techniques based on size ,stiffness and shape do not provide enough specificity to cell type, and correlation to clinical condition .We propose a novel microfluidic device capable of high throughput molecule dependent separation of cells by flowing them through a microchannel decorated with molecule specific coated ridges. The unique aspect of this sorting design is the use of optimized gap size which is small enough to lightly squeeze the cells while flowing under the ridged part of the channel to increase the surface area for interaction between the ligand on cell surface and coated receptor molecule but large enough so that biomechanical markers, stiffness and viscoelasticity, do not dominate the cell separation mechanism. We are able to separate Jurkat cells based on its expression of PSGL-1ligand using ridged channel coated with P selectin at a flow rate of 0.045ml/min and achieve 2-fold and 5-fold enrichment of PSGL-1 positive and negative Jurkat cells respectively. [Preview Abstract] |
Monday, November 21, 2016 5:09PM - 5:22PM |
L22.00004: Programmed assembly of colloidal arrays using shaped microvortices Avanish Mishra, Aloke Kumar, Steven Wereley Ability to program colloidal assemblies in desired spatial patterns and orientation remains a significant roadblock to the development of micro- and nanoparticle-based devices. In this work, by shaping electrothermal microvortices, we demonstrate a high-throughput assembly of particles in complex shapes. The microscale electrothermal vortices are generated by optical heating of an electrode layer in the presence of an AC electric field. Entrained in the electrothermal flow particles rapidly and reversibly assemble into the shapes of projected optical patterns. These microvortices can be dynamically reconfigured by changing the optical patterns, thus allowing us to alter the topology of particle clusters. Additionally, driven by an interplay of Stokes drag and dipole-dipole repulsion, the number of particles and inter-particle spacing in an array can also be dynamically tuned by changing the flow velocity. Using a net electrophoretic force in an asymmetrical AC electric field, we demonstrate permanent deposition of patterned particles. In this presentation, we plan to discuss the mathematical background on shaping the electrothermal flow, its implementations in forming colloidal arrays, and their applications. [Preview Abstract] |
Monday, November 21, 2016 5:22PM - 5:35PM |
L22.00005: Using machine vision and data mining techniques to identify cell properties via microfluidic flow analysis Geoffrey Horowitz, Samuel Bowie, Anna Liu, Nicholas Stone, Todd Sulchek, Alexander Alexeev In order to quickly identify the wide range of mechanistic properties that are seen in cell populations, a coupled machine vision and data mining analysis is developed to examine high speed videos of cells flowing through a microfluidic device. The microfluidic device contains a microchannel decorated with a periodical array of diagonal ridges. The ridges compress flowing cells that results in complex cell trajectory and induces cell cross-channel drift, both depend on the cell intrinsic mechanical properties that can be used to characterize specific cell lines. Thus, the cell trajectory analysis can yield a parameter set that can serve as a unique identifier of a cell's membership to a specific cell population. By using the correlations between the cell populations and measured cell trajectories in the ridged microchannel, mechanical properties of individual cells and their specific populations can be identified via only information captured using video analysis. [Preview Abstract] |
Monday, November 21, 2016 5:35PM - 5:48PM |
L22.00006: A Multi-Gradient Generator in a Single Microfluidic Device for Optical Microscopy and Interferometry Manuel Bedrossian, Jay Nadeau, Chris Lindensmith The goal of this work was to create a single microfluidic device capable of establishing multiple types of gradients in a quantifiable manner. Many microbial species are known to exhibit directed motility in the presence of stimuli. This phenomenon, known as taxis, can be used as a bio-signature and a means of identifying microorganisms. Directed microbial motility has been seen as a response to the presence of certain chemicals, light, heat, magnetic fields, and other stimuli. Microbial movement along the gradient vector, that cannot be explained by passive hydrodynamics or Brownian motion, can shed light on whether the sample contains living microbes or not. The ability to create multiple types of gradients in a single microfluidic device allows for high throughput testing of heterogeneous samples to detect taxis. There has been increased interest in the search for life within our solar system where liquid water is known to exist. Induced directional motility can serve as a viable method for detecting \textit{living} organisms that actively respond to their environment. The device developed here includes a chemical, photonic, thermal, and magnetic gradient generator, while maintaining high optical quality in order to be used for microscopy as well as quantitative phase imaging [Preview Abstract] |
Monday, November 21, 2016 5:48PM - 6:01PM |
L22.00007: Heat transfer enhancement in a cross-slot micro-geometry Allysson Domingues, Waleed Abed, Robert Poole, David Dennis The cross-slot geometry is a common geometric shape in microfluidic applications. In this work we investigate, numerically and experimentally, the influence of a purely-inertial flow instability on the enhancement of heat transfer in a cross-slot micro-geometry where symmetry is broken but the flow remains steady. The cross-slot comprises two crossed square channels with opposed inlets and outlets, which generate a stagnation point at the geometric centre. The flow of a Newtonian fluid is steady, two-dimensional and produces a sharp symmetric boundary between fluid streams entering the cross-slot from opposite directions at low Reynolds numbers ($Re$). Therefore, only conduction heat transfer occurs between the fluid streams as there is virtually no mixing between them. Beyond a certain critical value of $Re$, approximately 40, a steady symmetry-breaking bifurcation occurs and convective heat transfer arises because an axially oriented spiral vortex is created in the outlet arms. The effects of this purely-inertial instability suggest it is an effective method of enhancing mixing and heat transfer in microfluidic devices that can be exploited in applications such as lab-on-chip and micro chemical-reaction devices at relatively low Reynolds numbers (i.e. $Re<100$). [Preview Abstract] |
Monday, November 21, 2016 6:01PM - 6:14PM |
L22.00008: A scalable micro-mixer for biomedical applications Luca Cortelezzi, Simone Ferrari, Angelo Dubini Our study presents a geometrically scalable active micro-mixer suitable for biomedical/bioengineering applications and potentially assimilable in a Lab-on-Chip. We designed our micro-mixer with the goal of satisfying the following constraints: small dimensions, because the device must be able to process volumes of fluid in the range of $10^{-6} \div 10^{-9}$ liters; high mixing speed, because mixing should be obtained in the shortest possible time; constructive simplicity, to facilitate realizability, assimilability and reusability of the micro-mixer; and geometrical scalability, because the micro-mixer should be assimilable to microfluidic systems of different dimensions. We studied numerically the mixing performance of our micro-mixer both in two- and three-dimensions. We characterize the mixing performance in terms of Reynolds, Strouhal and P\'{e}clet numbers in order to establish a practical range of operating conditions for our micro-mixer. Finally, we show that our micro-mixer is geometrically scalable, ie., micro-mixers of different geometrical dimensions having the same nondimensional specifications produce nearly the same mixing performance. [Preview Abstract] |
Monday, November 21, 2016 6:14PM - 6:27PM |
L22.00009: Electromagnetically driven liquid iris. Deasung Jang, Jin Won Jeong, Dae Young Lee, Dae Geun Kim, Sang Kug Chung This paper describes a tunable liquid iris driven by electromagnetic actuation for miniature cameras. To examine the magnetic effect on a ferrofluid, the contact angle modification of a sessile ferrofluid droplet is tested using a neodymium magnet and an electric coil which 2.5 A current is applied to. The contact angle variations of the ferrofluid droplet for each test are 21.3 and 18.1 degrees, respectively. As a proof of concept, a pretest of a tunable iris actuated by electromagnetic effect is performed by using a hollow cylinder cell. As applying the current, the aperture diameter is adjusted from 4.06 mm at 0A to 3.21 mm at 2.0A. Finally, a tunable liquid iris (9 x 9 x 2 mm$^{\mathrm{3}})$, consisting of two connected circular microchannels, is realized using MEMS technology. the aperture diameter of the tunable liquid iris is able to be modified from 1.72 mm at 0 A to 1.15 mm at 2.6 A. This tunable optical iris has potential applications not only for portable electronic devices but also in biomedical fields such as optical coherence tomography and microsurgery. [Preview Abstract] |
Monday, November 21, 2016 6:27PM - 6:40PM |
L22.00010: Microfluidic particle manipulation using high frequency surface acoustic waves Ye Ai, David J. Collins Precise manipulation of particles and biological cells remains a very active research area in microfluidics. Among various force fields applied for microfluidic manipulations, acoustic waves have superior propagating properties in solids and fluids, which can readily enable non-contact cell manipulation in long operating distances. Exploiting acoustic waves for fluid and cell manipulation in microfluidics has led to a newly emerging research area, acoustofluidics. In this work, I will present particle and cell manipulation in microfluidics using high frequency surface acoustic waves (SAW). In particular, I will discuss a unique design of a focused IDT (FIDT) structure, which is able to generate a highly localized SAW field on the order of 20 \textmu m wide. This highly focused acoustic beam has an effective manipulation area size that is comparable to individual micron-sized particles. Here, I demonstrate the use of this highly localized SAW field for single particle level sorting with sub-millisecond pulses and selective capture of particles. Based on the presented studies on acoustic particle manipulation, I envision that the merging of acoustics and microfluidics could enable various particle and cell manipulations needed in microfluidic applications. [Preview Abstract] |
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