Bulletin of the American Physical Society
2005 58th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 20–22, 2005; Chicago, IL
Session BB: Microfluidics: Velocimetry |
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Chair: Kenny Breuer, Brown University Room: Hilton Chicago Waldorf |
Sunday, November 20, 2005 10:56AM - 11:09AM |
BB.00001: Quantum Nanospheres{\texttrademark} for sub-Micron Particle Image Velocimetry Carl Meinhart, Patrick Freudenthal Quantum Nanospheres (QNs) have been developed as a new type of flow-tracing particle for micron resolution Particle Image Velocimetry (micro-PIV). A 60 nm diameter QN is formed by conjugating approximately eighty 10 nm quantum dots (QDs) to an individual 43 nm polystyrene bead. Since QDs have relatively high quantum efficiency, the QNs are significantly brighter than commercially-available fluorescently-dyed particles of similar size. In addition, the 60 nm dia. QNs allow accurate velocity measurements close to microchannel walls and high spatial resolution for micro-PIV measurements. QNs maintain their fluorescent properties whether suspended in liquid or gas and may prove well-suited for gas-phase PIV. The use of QNs as flow-tracing particles for micro-PIV was demonstrated by measuring fluid motion in a 30 x 300 um channel. Using an interrogation region of 1 x 1024 pixels and ensemble averaging 1800 image pairs, we achieved a spatial resolution of 117 nm x 11.7 um x 2 um. Using 50{\%} overlap between interrogation regions, the velocity vector spacing is 58.6 nm. Since the QNs have a nominal diameter of 60 nm, the particle diameter is 50{\%} of the smallest dimension of the interrogation region. To the best of the authors' knowledge, these velocity measurements are the highest spatial resolution measurements (based on interrogation volume) reported to date. [Preview Abstract] |
Sunday, November 20, 2005 11:09AM - 11:22AM |
BB.00002: Statistical Particle Tracking Velocimetry using Single Molecule and Quantum Dot Tracers Jeff Guasto, Peter Huang, Kenneth Breuer Particle Tracking Velocimetry (PTV) with nanometer resolution is demonstrated using single molecules and quantum dots (QD) as tracer particles. Several problems are unique to this regime, including: shot noise from intensified cameras, large drop- in/drop-out (due to Brownian motion and QD blinking), sub-pixel tracer intensity profiles and lastly issues associated with tracking with high particle seeding densities. We have developed a statistical particle tracking method to successfully address these problems. The algorithm tracks all possible particles, removing non-physical matches using the global statistical properties of the system, leaving the true particle displacement distribution (and hence velocity). The algorithm is validated using FITC-Dextran molecules and QDs. Experiumental results concerning the velocity and diffusion characteristics of the nanoscale tracers are reported. [Preview Abstract] |
Sunday, November 20, 2005 11:22AM - 11:35AM |
BB.00003: Single Quantum Dot (QD) Velocimetry S. Pouya, M. Koochesfahani, P. Snee, M. Bawendi, D. Nocera We introduce the use of quantum dot (QD) nanoparticles for near-surface velocimetry and provide preliminary data to demonstrate its feasibility. Evanescent wave illumination is used to image the motion of water-soluble (CdSe)ZnS QDs with a core size of 6 nm within a region of order 100 nm of a surface. These particles are an order of magnitude smaller than those typically used to date in nano-PIV studies. Results will be presented for the two in-plane components of the velocity near the surface of a microchannel. This work was supported by the CRC Program of the National Science Foundation, Grant Number CHE-0209898. [Preview Abstract] |
Sunday, November 20, 2005 11:35AM - 11:48AM |
BB.00004: 3D scanning micro-PIV measurement of micro-round tube flow Kyosuke Shinohara, Yasuhiko Sugii, Jae Hong Jeong, Koji Okamoto Recently, a number of microfluidic researches were carried out for various fields such as biomedicine, analytical chemistry, chemical synthesis, drug delivery, and so on. In microscopic scale, the dominant factors of fluid dynamics are completely different from those in macro scale: Surface tension and electrical force are bigger than inertia forces. Thus, in order to design microfluidic devices, the understanding of specific physics in microflows is necessary. In this work, the authors suggest a strong measurement instrument for microfluid dynamics. The 3D scanning micro-PIV system was developed in order to measure three-dimensional velocity distributions at micrometer scale resolution. This system consisted of an epi-fluorescence microscope with objective lens, a high-speed CMOS camera with 6000 fps at 512 x 512 pixels, a piezo actuator, and Nd:YAG CW laser. To validate the measurement accuracy of the system, it was applied to 95 $\mu$m micro-round tube flow. 3D (three-dimensional: x,y,z) -3C (three-component: u,v,w) velocity distribution of the micro-round tube was obtained at the spatial resolution of 5.4 x 2.7 x 4.2 $\mu$m. [Preview Abstract] |
Sunday, November 20, 2005 11:48AM - 12:01PM |
BB.00005: 3-D micro-PIV measurement of microchannel flow using high-speed confocal scanning microscopy Haruyuki Kinoshita, Marie Oshima, Shohei Kaneda, Teruo Fujii Three-component velocity measurement has been performed for micro flow using a 3-D micro-PIV technique. Sequential volumetric particle images are obtained using a high-speed 3-D confocal scanning microscopy. The present 3-D confocal system consists of a microscope, a Nipkow disk-based multi-spot confocal scanner, a piezo-driven objective positioner, and a high-speed camera. This system can scan the cubic domain of 240 $\times$ 180 $\times$ 25 $\mu$m in less than 100 milliseconds as changing the position of the confocal plane quickly in the out-of-plane direction by the objective positioner. As the result, we can record time series of 3-D spatial distributions of tracer particles in slow micro flow. All three components of velocity are obtained applying a 3-D PIV algorithm based on the 3-D cross-correlation method to the sequential volumetric images. We have measured a 3-D flow in a microchannel with a step using the 3-D micro-PIV technique. The out-of-plane component of velocity has been measured successfully in addition to the in-plane velocity distribution. [Preview Abstract] |
Sunday, November 20, 2005 12:01PM - 12:14PM |
BB.00006: Examination of Large-Scale Structures in Turbulent Microchannel Flow Hao Li, Michael Olsen Microscopic particle image velocimetry was performed on turbulent flow in microchannels of various diameters and aspect ratios to evaluate the characteristics of large-scale turbulent structures. Spatial correlations of velocity fluctuations were measured along the channel centerlines and at four other locations, and characteristic turbulent length scales were defined. For square microchannels, excellent agreement was observed between the measured length scales and results for macroscale duct flow. Along the centerline of the square microchannels the normalized longitudinal length scale, $2Lx_ {uu}/W$, ranged from 0.30-0.37, the lateral length scale, $2Ly_ {uu}/W$, ranged from 0.16-0.18, and the ratio between the two length scales, $Lx_{uu}/Ly_{uu}$ ranged from 1.88-2.00, results which agree well with macroscale results. Results for non- square microchannels indicate that as aspect ratio increases, the ratio $Lx_{uu}/Ly_{uu}$ also increases, ranging from 2.29 for an aspect ratio of 2.09 up to 3.75 for an aspect ratio of 5.68. For the square microchannels the turbulent structures are smaller near the side walls than near the center of the microchannel with $2Lx_{uu}/W$ ranging from 0.30-0.38 along the centerline, but dropping to 0.04-0.06 at $y/(W/D) = 0.94$. Similar results were observed for the rectangular microchannels. For the rectangular microchannels $2Lx_{uu}/W$ ranged from 0.32 to 0.42, compared to 0.30-0.38 for the square microchannels. [Preview Abstract] |
Sunday, November 20, 2005 12:14PM - 12:27PM |
BB.00007: A maximum likelihood algorithm for the reconstruction of velocity profile with nano-PIV Christel Hohenegger, Peter Mucha At nano-scale, images of particle flows near a channel wall are obtained combining standard PIV techniques with evanescent wave illumination [R. Sadr et al., J. Fluid Mech. 506, 357-367 (2004)]. Assuming a Langevin description with experimentally known diffusion tensor and a fluid velocity profile directed in one-in-plane direction, we simulate linear, parabolic and electro-osmotic flow with a Milstein scheme of both strong- and weak- order 1. We develop a maximum likelihood algorithm to reconstruct the dependence of the in-plane velocity profile from the out-ot-plane direction. We use PIV simulated particle images and assume an uniform out-of-plane distribution. We further compare the results obtained with two different forms of the probability density function for the in-plane displacement. Next we discuss the validity of the model and of the reconstruction in light of the comparison with true experimental data, in particular the difficulties encountered when assuming a non-uniform out-of-plane distribution. Finally we identify the values of the physical parameters guarantying the validity of the reconstruction algorithm. [Preview Abstract] |
Sunday, November 20, 2005 12:27PM - 12:40PM |
BB.00008: Temperature Measurement using Brownian Motion in the Presence of a Velocity Gradient. Pramod Chamarthy, Steve Wereley, Suresh V. Garimella Brownian motion of sub-micron sized tracer particles is a common source of measurement uncertainty in micro fluidics experiments. This random movement of particles is known to broaden the cross correlation peak in Particle Image Velocimetry (PIV). If information on Brownian motion can be extracted from the increase in peak width, equations in the literature can be used to relate it to temperature. A PIV algorithm that detects both the location and broadening of the correlation peak can measure velocity as well as temperature simultaneously using the same set of images. The feasibility of this technique was demonstrated (Hohreiter et al. 2002) through experiments and simulations in a stationary fluid for the temperature range 20$^\circ$C - 50$^\circ$C. Preliminary experimental results will be presented in which temperatures ranging from 20$^\circ$C - 80$^\circ$C were measured in a quiescent pool of water using a standard epi-fluorescence $\mu$PIV system. Three different methods - standard PIV, Single Particle Tracking and Low Image Density PIV - were used to extract temperature from the same set of images and the results compared. The effects of velocity gradients on temperature measurement accuracy and temperature (and its gradients) on velocity measurement accuracy will be explored. [Preview Abstract] |
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