Bulletin of the American Physical Society
68th Annual Meeting of the APS Division of Fluid Dynamics
Volume 60, Number 21
Sunday–Tuesday, November 22–24, 2015; Boston, Massachusetts
Session E11: Nanoscale Flows: General |
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Chair: Anoop Kanjirakat, Texas A&M University at Qatar Room: 111 |
Sunday, November 22, 2015 4:50PM - 5:03PM |
E11.00001: Measurement of the near-wall velocity profile for a nanofluid flow inside a microchannel Anoop Kanjirakat, Reza Sadr Hydrodynamics and anomalous heat transfer enhancements have been reported in the past for colloidal suspensions of nano-sized particles dispersed in a fluid (nanofluids). However, such augmentations may manifest itself by study of fluid flow characteristics near in the wall region. Present experimental study reports near-wall velocity profile for nanofluids (silicon dioxide nanoparticles in water) measured inside a microchannel. An objective-based nano-Particle Image Velocimetry (nPIV) technique is used to measure fluid velocity within three visible depths, O(100nm), from the wall. The near-wall fluid velocity profile is estimated after implementing the required corrections for optical properties and effects caused by hindered Brownian motion, wall-particle interactions, and non-uniform exponential illumination on the measurement technique. The fluid velocities of nanofluids at each of the three visible depths are observed to be higher than that of the base fluid resulting in a higher shear rate in this region. The relative increase in shear rates for nanofluids is believed to be the result of the near-wall shear-induced particle migration along with the Brownian motion of the nanoparticles. [Preview Abstract] |
Sunday, November 22, 2015 5:03PM - 5:16PM |
E11.00002: The deposition of gold nanoparticles in MWCNT forests Franciscus de Jong, Adeline Buffet, Michael Schlueter The deposition, i.e. transport and attachment, of small-sized particles is a basic process, on which many applications are based. The innumerable applications range from biology and medicine to engineering. Due to their promising mechanical properties multi-walled carbon nanotubes (MWCNTs) have gained increasing popularity in the past decade. A large number of dense packed vertically aligned MWCNTs form a so-called MWCNT forest. In our study we functionalized the MWCNT forest to filter gold nanoparticles from a colloidal suspension. An experimental investigation was carried out in which the particle deposition kinetics was locally determined with small-angle X-ray scattering (SAXS). Furthermore, inductively coupled plasma atomic emission spectroscopy (ICP-AES) was used to verify the local observations. It was concluded that both, SAXS and ICP-AES investigations shows very good agreement. Furthermore, an analytical deposition model was developed based on the DLVO-theory. The experimental and theoretical investigation presented here give insight in the deposition kinetics within a MWCNT forest. The results open up pathways to optimize MWCNT forests for filtering purposes. [Preview Abstract] |
Sunday, November 22, 2015 5:16PM - 5:29PM |
E11.00003: Experimental demonstration of scaling behavior for ionic transport and its fluctuations in individual carbon nanotube Lyderic Bocquet, Eleonora Secchi, Antoine Nigues, Alessandro Siria We perform an experimental study of ionic transport and current fluctuations inside individual Carbon Nanotubes (CNT) with a size ranging from 40 down to 7 nanometers in radius. The conductance exhibits a power law behavior dependence on the salinity, with an exponent close to 1/3. This is in contrast to Boron-Nitride nanotubes which exhibits a constant surface conductance. This scaling behavior is rationalized in terms of a model accounting for hydroxide adsorption at the (hydrophobic) carbon surface. This predicts a density dependent surface charge with a exponent 1/3 in full agreement with the experimental observations. Then we measure the low frequency noise of the ionic current in single CNTs. The noise exhibits a robust 1/f characteristic, with an amplitude which scales proportionaly to the surface charge measured independently. Data for the various CNT at a given pH do collapse on a master curve. This behavior is rationalized in terms of the fluctuations of the surface charge based on the adsorption behavior. This suggests that the low frequency noise takes its origin in the process occuring at the surface of the carbon nanotube. [Preview Abstract] |
Sunday, November 22, 2015 5:29PM - 5:42PM |
E11.00004: The near wall TIRFM measurement of nano-tracer's statistical intensity distribution (SID) and determining the base intensity I$_{0}$ Xu Zheng The total internal reflection fluorescence microscopy (TIRFM) is an evanescent-wave-based technique for measuring nanoparticle dynamics very close to wall. The intensity of the evanescent wave decays exponentially (i.e. I(z)$=$I$_{0}$exp(z/z$_{\mathrm{p}}))$, which can provide information of the tracer particle position not just parallel but also normal to wall. However, considering the z information is encoded in tracer intensity, it is critical to determine the base intensity I$_{0}$. In this study, we will first establish a model to describe the statistical intensity distribution (SID) of the nano-tracers observed in the evanescent field inspired by the works of Huang et al.. A different function of particle-wall interaction and a term of the influence of the objective focal plane thickness are introduced in the present SID method. Then, TIRFM experiments are performed to measure the histogram of SID. The experimental histogram of SID is then fitted by the theoretical curve to determine I$_{0}$ which is the only one fit parameter. By near wall velocity measurement, we will show that the SID method has a very high precision in determining I$_{0}$ and the vertical z position of every nanotracer. Further tests show that the PDF of nano-tracers can reveal more information about how nanoparticles interact with the charged solid wall. This provides a promising method to detect the physical properties near interface. [Preview Abstract] |
Sunday, November 22, 2015 5:42PM - 5:55PM |
E11.00005: Nanodroplet Depinning Dynamics of from Nanoparticles Fong Yew Leong, Liu Qi, Zainul Aabdin, Utkarsh Anand, Tran Si Bui Quang, Utkur Mirsaidov Nanoscale defects on substrate affect the sliding motion of water nanodroplets. Using in situ TEM imaging, we visualized the depinning dynamics of water nanodroplets from gold nanoparticles on a flat SiNx surfaces. Our observations showed that nanoscale pinning effects of the gold nanoparticle opposes the lateral forces, resulting in stretching, even breakup, of the water nanodroplet. Using continuum long wave theory, we modelled the dynamics of a nanodroplet depinning from a nanoparticle of comparable length scales, and the model results are consistent with experimental findings. In particular, the critical depinning force for a ten-nanometer particle is found to be on the order of a nano-Newton, and the apparent viscosity of interfacial water is inferred to be several orders of magnitude greater than bulk values. Our findings have important implications on surface cleaning at the nanoscale. [Preview Abstract] |
Sunday, November 22, 2015 5:55PM - 6:08PM |
E11.00006: Formation of parallel two-phase flow in nanochannel and application to solvent extraction Yutaka Kazoe, Takuya Ugajin, Ryoichi Ohta, Kazuma Mawatari, Takehiko Kitamori Micro chemical systems have realized high-throughput analysis in ultra small volumes. Our group has established unit operations such as extraction, separation and reaction, and a concept of integration of chemical processes using parallel multi-phase flows in microchannels. Recently, the research field has been extended to 10-1000 nm space (extended-nanospace). Exploiting extended-nanospace, we developed ultra high performance chemical operations such as aL-chromatography and single molecule immunoassay. However, formation of parallel multi-phase flow in nanochannels has been difficult. The challenge is to control liquid-liquid/gas-liquid interfaces in 100 nm-scale. For this purpose, this study developed a partial surface modification method of nanochannel and verified formation of parallel two-phase flow. We achieved partial hydrophobic modification using focused ion beam (FIB). Using this method, formation of parallel water/dodecane two-phase flow in a nanochannel of 1500 nm width and 890 nm depth was succeeded. Solvent extraction of lipid, which is a basic separation in bioanalysis, was achieved in 25 fL volume much smaller than single cell. This study will greatly contribute to develop novel nanofluidic devices for chemical analysis and chemical synthesis. [Preview Abstract] |
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