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 KB: Minisymposium: Fluid Transport in Nanotubes and Nanochannels |
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Chair: Sandra Troian, Princeton University Room: Hilton Chicago Waldorf |
Monday, November 21, 2005 4:10PM - 4:36PM |
KB.00001: Carbon Nanotube-Based Devices and the Study of Fluid Transport through Them Haim Bau Experimental data pertaining to liquid transport through carbon nanotubes with diameters ranging from a few to hundreds of nanometers is briefly reviewed. A hybrid fabrication technique of carbon nanotube-based devices is described. The fabrication technique combines dielectrophoretic positioning of nanotubes and photolithography. The devices facilitate the introduction and control of fluid flow through the carbon nanotubes. Preliminary experimental results pertaining to capillary filling of, condensation in, evaporation from, particle flow into, and ionic current transmission through the nanotubes are discussed and compared with theoretical predictions. Although many of the observations indicate that the liquids behave classically, a few observations are still puzzling and await explanation. Finally, electron microscopy of controlled liquid flow is proposed as a new paradigm in fluid physics. [Preview Abstract] |
Monday, November 21, 2005 4:36PM - 5:02PM |
KB.00002: Nanohydrodynamics within the electrical double layer Lyderic Bocquet Charge transport in nanochanels is investigated using molecular dynamics. We focus in particular on the microscopic origin of the widely used ``Zeta potential.'' We show that the definition of this quantity not only involves the electrostatic nature of the interface, but is also intrinsincaly related to the dynamics of the solvent at the solid surface, providing new perspectives to control this quantity. We show in particular that the dynamics of the electric double layer (EDL) is very much dependent on the wettability of the charged surface on which the EDL develops. For a wetting surface, the dynamics, characterized by the so-called Zeta potential, is mainly controlled by the electric properties of the surface, and our work provides a clear interpretation for the traditionally introduced immobile Stern layer. In contrast, for non-wetting surfaces the immobile layer disappears and the Zeta potential deduced from electrokinetic effects is considerably amplified by the existence of a slippage at the solid substrate. The existence of strongly amplified electro-osmotic effects is accordingly demonstrated. Simulation results are shown to be in excellent agreement with predictions taking into account the slippage of the fluid the solid surface. The amplification effect is accordingly controlled by the ratio between the slip length (of the fluid at the solid surface), and the debye length. Such effects open the possibility of strongly enhanced electro-osmotic and electrophoretic effects in microchanels. [Preview Abstract] |
Monday, November 21, 2005 5:02PM - 5:28PM |
KB.00003: Carbon nanotubes as molecular conduits: flow of water, protons, ions, and nucleic acids Gehard Hummer The transport of water, protons, ions, and nucleic acids through carbon nanotubes was studied with all-atom molecular dynamics simulations. Water is found to fill even narrow pores of sub-nanometer diameter, but the filling is sensitive to the strength of attractive pore-water interactions and local electric fields. Motions of water through nanotubes is fast on a molecular scale. Protons were also found to move rapidly along one-dimensionally ordered water chains inside nanotubes. The transport of nucleic acids through nanotube membranes is dominated by polymer conformational dynamics during entry, and hydrophobic attachment to the pore walls during exit. [Preview Abstract] |
Monday, November 21, 2005 5:28PM - 5:54PM |
KB.00004: Multiscale Simulations of Carbon Nanotubes and Liquids Petros Koumoutsakos We present molecular dynamics and hybrid continuum/atomistic simulations of carbon nanotubes in liquid environments with an emphasis on aqueous solutions. We emphasize computational issues such as interaction potentials and coupling techniques and their influence on the simulated physics. We present results from simulations of water flows inside and outside doped and pure carbon nanotubes and discuss their implications for experimental studies. [Preview Abstract] |
Monday, November 21, 2005 5:54PM - 6:20PM |
KB.00005: Molecular Dynamics Study of Phase Change of Water inside a Single-Walled Carbon Nanotube Shigeo Maruyama The phase change of liquid water to ice crystal inside a single-walled carbon nanotube (SWNT) was studied with molecular dynamics simulations. Water molecules were modeled with SPC/E potential and carbon-carbon interaction was expressed by Brenner potential. The carbon-water interaction was expressed with the Lennard-Jones function with the quadrupole interaction term. An SWNT with liquid water inside was initially kept in equilibrium at 300 K. Then, the carbon atoms were cooled at the constant cooling rate. The liquid to solid phase change for various cooling rates in a SWNT with various chiralities were examined. With certain cooling rate for a fixed chirality SWNT of (10, 10), the phase change was observed in the temperature range of 200K-220K. For sufficient slow cooling rate, the structure of ice crystal was a hollow octagonal tube. Similar simulations for several host SWNTs with different chiralities such as (8, 8), (9, 9), (11, 11) and (14, 3) were examined. It turned out that for thinner SWNTs the ice crystal favored the hollow tube structure such as pentagonal and hexagonal tubes depending on the diameter. On the other hand, for thicker nanotube the ice tube larger than octagonal structure was not obtained. Depending on the diameter of SWNT, the chiral water tube structure was also observed. [Preview Abstract] |
Monday, November 21, 2005 6:20PM - 6:46PM |
KB.00006: Multiphase fluids confined in carbon nanotubes Constantine Megaridis, Yury Gogotsi, Alexander Yarin The dynamics of liquid attoliter volumes contained in carbon nanotubes is investigated theoretically and experimentally. The experiments employ electron microscopy to visualize multiphase fluids in real time with spatial resolution approaching 1nm. The hydrophilic nanochannels studied include hydrothermally synthesized, CVD and commercially produced carbon nanotubes with inner diameters in the range 5-300 nm and wall thickness ranging from 1 nm to 40 nm. Dynamic phenomena are presented for aqueous fluids contained in closed-end nanotubes, and pure water condensing inside open-end carbon nanotubes. Some examples are given on filling nanotube channels with fluids impregnated with solid particles. A theoretical model formulated using a continuum approach, combines temperature-dependent mass diffusion with intermolecular (Lennard-Jones) interactions in the fluid bulk, as well as in the vicinity of the carbon walls. Several axisymmetric cases are considered, and comparisons between theoretical predictions and experimental data are performed. The current study shows the potential of using nanotube channels for understanding fluid behavior at the nanoscale. [Preview Abstract] |
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