Bulletin of the American Physical Society
64th Annual Meeting of the APS Division of Fluid Dynamics
Volume 56, Number 18
Sunday–Tuesday, November 20–22, 2011; Baltimore, Maryland
Session L18: Microfluids: Fluidic Devices I |
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Chair: Xiangchun Xuan, Clemson University Room: 321 |
Monday, November 21, 2011 3:35PM - 3:48PM |
L18.00001: Levitation, aggregation and separation of micro-sized particles in a Hydrodynamic Acoustic Sorter, HAS Mauricio Hoyos, Angelica Castro, Despina Bazou Levitation, aggregation and separation of micron-sized particulate materials can be generated in a fluidic resonator by an ultrasonic standing wave field force. A piezoelectric transducer generates standing waves between the two walls of a parallel plate channel composing the resonator. The number of pressure nodes $n$ is given by the relationship: $w=n\lambda /2$ with $\lambda$ the wavelength. The primary radiation force generated by the standing wave generates levitation of micron-sized particles driving them toward the nodal planes. An equilibrium position is reached in the channel thickness where the acoustic force balances the gravity force. The equilibrium position is independent on particle size but it depends on the acoustic properties. Once particles reach the equilibrium position, transversal secondary forces generate aggregation. We shall present the levitation and aggregation process of latex particles and cancer cells in a 2MHz resonator. We demonstrate the possibility of separating particles under flow in a Hydrodynamic Acoustic Sorter HAS, in function of their acoustic impedance and in function of their size using a programming field force. [Preview Abstract] |
Monday, November 21, 2011 3:48PM - 4:01PM |
L18.00002: Continuous Separation of Microparticles in a Microfluidic Channel via the Elasto-inertial Effect of Non-Newtonian Fluid Sehyun Shin, Jeonghun Nam, Hyunjung Lim Pure separation and sorting of microparticles from complex fluids are essential for biochemical analyses and clinical diagnostics. In this study, we present a simple and label-free method to separate microparticles with high purity using the elasto-inertial characteristic of non-Newtonian fluid in microchannel flow. At the inlet, particle-containing sample flow was pushed toward the side walls by introducing sheath fluid from the center inlet. Particles of 1 $\mu $m and 5 $\mu $m diameter that were suspended in viscoelastic fluid were successfully separated in the outlet channels: larger particles were notably focused on the centerline of the channel at the outlet, while smaller particles kept flowing along the sidewalls with minimal lateral migration to centerline. The same technique was further applied to separate platelets from diluted whole blood. Through cytometric analysis, we found that the purity of collected platelets was close to 99.9{\%}. Conclusively, the technique of microparticle separation using elasto-inertial forces in non-Newtonian fluid is proven to be an effective method for separating and collecting microparticles based on size differences with high purity. [Preview Abstract] |
Monday, November 21, 2011 4:01PM - 4:14PM |
L18.00003: Interactive tuning of flow geometry for size-sensitive sorting of microparticles Sascha Hilgenfeldt, Cheng Wang, Shreyas Jalikop We show that sensitive selection, focusing, and sorting of microparticles by size is possible in microfluidic setups without the need for moving boundaries or external forces on the particles. The flow domain is flexibly and interactively shaped by the superposition of a transport flow and a microbubble-induced streaming flow. This method separates particles for which both the absolute size and the size differential are only a few micrometers, in a setup whose smallest geometric scale is about 100 microns. Size-dependent trapping, release, and focusing can be effected and used for switching and sorting [1]. Devices based on this novel concept are easy to fabricate and can be directly tailored to a variety of transported objects, including cells and vesicles. \\[4pt] [1] C. Wang, S. V. Jalikop and S. Hilgenfeldt, Applied Physics Letters {\bf 99}, 034101 (2011). [Preview Abstract] |
Monday, November 21, 2011 4:14PM - 4:27PM |
L18.00004: Continuous size-based dielectrophoretic particle sorting in a microfluidic device Barukyah Shaparenko, Han-Sheng Chuang, Howard Hu, Haim Bau The dielectrophoresis~(DEP) force acting on a particle passing through a nonuniform electric field is proportional to its volume, making DEP well-suited for size-based particle sorting. Pinched flow fractionation uses the geometry constraints of a narrow segment of microchannel to effect size-based separation. We combine these two techniques in series to create a size-based microfluidic sorting device, using negative DEP to allow for continuous particle sorting. An interdigitated array of five L-shaped electrodes permits the sorting of up to five different particle sizes. For a given set of particle sizes ($\sim \!1$--$10 \textrm{ }\mu$m), this sorting process can be optimized by using the applied potentials on the electrodes as our optimization parameters. Through on-chip voltage control of the electrodes, we can achieve sorting for various sets of particle sizes with the same microfluidic device geometry. We compare the computational optimization solution to an analytical solution and with experimental results. [Preview Abstract] |
Monday, November 21, 2011 4:27PM - 4:40PM |
L18.00005: Gravity driven separation based on lateral displacement in anisotropic microfluidic media Raghavendra Devendra, German Drazer We designed an anisotropic periodic array of rectangular obstacles and directly measured the Brownian motion of particles in the absence of an external field. Earlier, we established that in the limit of small driving forces, particle-wall hydrodynamic interactions, coupled with geometric confinement, lead to non- linear effects in the mobility of rigid spherical particles in the periodic array. We further proposed that such anisotropic media could be used for continuous size-based separation of particles in microfluidic devices. Here, we show that such anisotropic systems could also lead to separation in the deterministic limit of high Peclet numbers. We use gravity as the driving force and investigate the effect of the orientation of the force with respect to the media. We observe directional locking in the motion of the particles, analogous to that observed in macroscopic systems and discuss the role of irreversible particle-obstacle interactions in the observed behavior. We report the average migration angles for different sizes of particles and confirm the utility of these anisotropic arrays to create microdevices for continuous particle sorting. [Preview Abstract] |
Monday, November 21, 2011 4:40PM - 4:53PM |
L18.00006: Diamagnetic Particle Separation in Ferrofluid Microflows Xiangchun Xuan, Litao Liang Particle separation is important for a wide range of applications. A variety of force fields have been demonstrated to separate particles in microfluidic devices. Magnetic field-induced separation is simple, cheap, and free of fluid heating issues that accompany electric, acoustic, and optical methods. We develop a novel magnetic particle separation method in a curved microchannel with a nearby permanent magnet. This method is capable of separating both magnetic and nonmagnetic particles by size. It is based on the dependence of particle magnetophoresis on the particle size and the particle's distance from the magnet. We present in this talk a continuous separation of 3 $\mu $m- and 5 $\mu $m-diameter polystyrene particles in a ferrofluid flow without magnetic and fluorescent labeling. We also develop a numerical model to simulate the particle separation process. [Preview Abstract] |
Monday, November 21, 2011 4:53PM - 5:06PM |
L18.00007: Continuous blood fractionation using an array of slanted grooves Jorge A. Bernate, Liu Chengxun, Liesbet Lagae, German Drazer Blood is a complex fluid having different specialized biological functions and containing a plethora of clinical information. The separation of different blood components is a crucial step in many research and clinical applications. In this work we take advantage of the flow characteristics in microfluidic devices in which the bottom surface is patterned with slanted rectangular grooves to continuously fractionate blood. We exploit the flow in the vicinity of the patterned surface when the dimensions of the grooves are much smaller than the dimensions of the main channel. In these devices, we observed that the grooves act as open channels guiding flow along them with the flow over them being in the direction of the main channel. We present experiments in which the different blood components are deflected laterally to a different extent by the flow along the grooves depending on their sedimentation velocity, which allows their continuous fractionation. In particular, the heavier red blood cells experience the largest deflection while the lighter white blood cells deflect the least, allowing their passive and minimally invasive isolation. In addition, this fluidic platform can also be used to separate magnetically labeled circulating cancer cells which can be retained in the flow along the grooves using a sufficiently strong magnetic force. [Preview Abstract] |
Monday, November 21, 2011 5:06PM - 5:19PM |
L18.00008: Dielectrophoretic Separation of Live and Dead Yeast Cells in Microfluidic Reservoirs Daniel Showers, Vincent Brown, Litao Liang, Tzuen-Rong J. Tzeng, Xiangchun Xuan Insulator-based dielectrophoresis (iDEP) is an emerging technology that has been widely used to manipulate particles and cells in microfluidic devices. Current iDEP devices use in-channel micro-obstacles such as hurdles, posts and ridges to create electric field fields, which may cause potential Joule heating problem due to the locally amplified electric field. In this talk we present a dielectrophoretic separation method in microfluidic reservoirs. Due to the significant size mismatch between a microchannel and its end-channel reservoirs, electric fields gradients are inherently produced at the microchannel-reservoir junction. The induced dielectrophoresis can be utilized to focus and trap cells and particles. We demonstrate a continuous concentration and a selective isolation of live yeast cells from dead yeast cells in a reservoir under DC-offset AC electric fields. The effects of AC to DC field ratio and AC field frequency on the separation performance are both examined. We also develop a numerical model to understand and predict the observed cell motions in microfluidic reservoirs. [Preview Abstract] |
Monday, November 21, 2011 5:19PM - 5:32PM |
L18.00009: Surface Design for Efficient Capturing of Rare Cells in Microfluidic Device Yaling Liu, Dan DePietro, Antony Thomas, Chi-mon Chen, Shu Yang This work aims to design, fabricate, and characterize a micro-patterned surface that will be integrated into microfluidic devices to enhance particle and rare cell capture efficiency. Capture of ultralow concentration of circulating tumor cells in a blood sample is of vital importance for early diagnostics of cancer diseases. Despite the significant progress achieved in development of cell capture techniques, the enhancement in capture efficiency is still limited and often accompanied with drawbacks such as low throughput, low selectivity, pre-diluting requirement, and cell viability issues. The goal of this work is to design a biomimetic surface that could significantly enhance particle/cell capture efficacy through computational modeling, surface patterning, and microfluidic integration and testing. A PDMS surface with microscale ripples is functionalized with epithelial cell adhesion molecule (EpCAM) to capture prostate cancer PC3 cells. Our microfluid chip with micropatterns has shown significantly higher cell capture efficiency and selectivity compared to the chips with plane surface or classical herringbone-grooves. [Preview Abstract] |
Monday, November 21, 2011 5:32PM - 5:45PM |
L18.00010: Cascade and staggered dielectrophoretic cell sorters Fang Yang, Xiaoming Yang, Hong Jiang, Guiren Wang We report experimental results of successful separation of different cancer cells (breast and prostate) from colorectal cancer cells in Dielectrophoresis (DEP) in continuous operation. Conductivity influence on DEP spectrum for each cell type has been investigated. Under optimized condition, different cell type can be separated from each other. Enrichment factor and cell purity are measured to characterize the performance of the DEP chip. AC voltage and frequency effect on the separation is measured. In practical lab-on-a-chip application highly purified cell and high flow rate are required. In order to increase the purity of the isolated cells, cascade DEP sorter is developed. To increase flow rate, staggered DEP sorter is developed. It is found that compared with single DEP sorter, adding cascade DEP sorter can significantly increase r the purity of the target cell. With the staggered chip, the flow rate can be increased without compromising enrichment factor. [Preview Abstract] |
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