Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session W2b: Nanoscale Liquids |
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Sponsoring Units: DCMP Chair: Oleg Gang, Brookhaven National Laboratory Room: LACC 151 |
Thursday, March 24, 2005 4:18PM - 4:54PM |
W2b.00001: Singularities in Contact line Motion: From molecular simulations to continuum theories Invited Speaker: Colin Denniston When the contact line at the intersection between a fluid interface and a solid moves, traditional continuum calculations predict a diverging dissipation. Experiments and continuum theories cannot reveal how this singularity is removed, but proposals are based on very different mechanisms: Shear-induced slip or diffusive transport. We present detailed molecular simulations and atomistically-derived mesoscale models [1] of contact line motion in the conditions assumed for diffusive models [2]. The singularity is primarily eliminated by slip, but there is a Marangoni-like contribution to slip that has not been observed previously. Diffusion is present, but perpendicular to the expected direction. We also find an interesting dynamic dewetting transition at a finite dynamic contact angle. [1] C. Denniston and M.O. Robbins, PRL 87, 178302 (2001); ibid, PRE 69, 021505 (2004). [2] H.-Y. Chen, D. Jasnow, J. Vinals, PRL 85, 1686 (2000). [Preview Abstract] |
Thursday, March 24, 2005 4:54PM - 5:30PM |
W2b.00002: Structure and Dynamics of Thin Molten Polymer Films Invited Speaker: While capillary wave theory accurately describes the surface structure simple liquids, complications arise for molten polymer films. The polymer’s high viscosity freezes long wavelength modes, Van der Waals interactions with the substrate modify the energetics, and the large molecular size leads to the failure of continuum hydrodynamics at nanometer length scales. X-ray scattering provides valuable information needed to understand polymer films at scales where these effects become important. Specular and diffuses scattering from polymer surfaces show capillary waves dominate the surface structure at long length scales, but indicates deviations from capillary wave roughness at nanometer length scales. Coherent x-ray scattering measurements of the relaxation rate of capillary wave fluctuations show remarkably good agreement with continuum theory for thick films and long wavelength modes [1]. Wide- angle x-ray scattering excited by standing waves measures density fluctuations as a function of depth within a liquid film and indicates that the near surface region of a film has modified properties. This work was funded by NSF Grant DMR- 0209542. [1] Hyunjung Kim et. al., Phys. Rev. Lett. 90, 068302 (2002) [Preview Abstract] |
Thursday, March 24, 2005 5:30PM - 5:42PM |
W2b.00003: Wetting of topological nano-patterned surfaces O. Gang, B. Ocko, K. Alvine, M. Fukuto, P. Pershan, C.T. Black We have investigated the evolution of simple hydrocarbon and fluorocarbon liquid films on nano-patterned surfaces of near-hexagonally packed 20 nm wide nano-cavities [1]. Our x-ray measurements show that the behavior of wetting films on patterned surfaces differs from the expected $\Delta \mu ^{-1/3}$ dependence found for the van der Waals interacting flat films [2]. Two different regimes (filling and growing) for the wetting film evolution were observed as a function of the chemical potential offset $\Delta \mu $. The filling regime exhibits a $\Delta \mu ^{-3/4 }$dependence for the adsorption of the liquid film into nanocavity; a significant enhancement compared to the flat surface. These results qualitatively confirm the theoretically predicted increase of the wetting exponent for the curved surface. However, quantitatively, the measured exponent for the paraboloid-like cavity is considerably lower than the predicted value [3]. \begin{enumerate} \item C. T. Black et al, \textit{Appl. Phys. Lett}., 79, \textbf{409, }(2001). \item O. Gang et al, M. Fukuto, P.Huber, P.Pershan, \textit{Coll. and Surf. A} \textbf{206}, 293, 2002 \item Rascon, C. and A.O. Parry, \textit{Nature}, \textbf{407}: p. 986 (2000); Robbins, M.O et al\textit{ Phys. Rev. A}, 43(8), 4344 (1991). \end{enumerate} [Preview Abstract] |
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