Bulletin of the American Physical Society
77th Annual Meeting of the Southeastern Section of the APS
Volume 55, Number 10
Wednesday–Saturday, October 20–23, 2010; Baton Rouge, Louisiana
Session HD: Liquids and Nanostructures |
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Chair: Saiful Khondaker, University of Central Florida Room: Nicholson Hall 108 |
Friday, October 22, 2010 1:30PM - 1:42PM |
HD.00001: ABSTRACT WITHDRAWN |
Friday, October 22, 2010 1:42PM - 1:54PM |
HD.00002: Breakup of Liquid Nano-threads Simulated by Molecular Dynamics Harris Wong, Ping Du A circular liquid thread of radius R will break up into drops if the axial wavelength of surface perturbation L $>$ 2$\pi $R. If L $<$ 2$\pi $R, the thread is stable and will remain intact. This is Rayleigh's stability criterion based on a continuum model. We use molecular dynamics to simulate the evolution of Lennard-Jones liquid threads with equilibrium radius R = 2.25-6.59, where R has been non-dimensionalized by the distance at which the Lennard-Jones potential equals zero. Periodic conditions are imposed at the boundaries of the simulation box so that the thread length is the wavelength L. We find that if R is fixed, there exists a range of L bounded by L$_{min}$ and L$_{max}$ such that for L $\ge $ L$_{max}$ the thread always breaks up into drops and stays as drops, and for L $\le $ L$_{min}$, the thread remains connected but the shape varies continuously among a series of shapes including a cylinder, unduloids, and sinusoids. For L$_{min} <$ L $<$ L$_{max}$, the thread can break up temporarily into drops and then resume connected. As R increases, L$_{min} \to $ L$_{max}$, and L$_{max}$ is slightly smaller than 2$\pi $R. The appearance of various shapes can be explained by the energy fluctuation of the system. [Preview Abstract] |
Friday, October 22, 2010 1:54PM - 2:06PM |
HD.00003: Temperature and viscosity effects on the velocity profile of a nanochannel electro-osmotic flow Bohumir Jelinek, Sergio D. Felicelli, Paul F. Mlakar, John F. Peters Significant temperature and viscosity effects on the electrokinetic transport in a nanochannel with a slab geometry are demonstrated using a molecular dynamics (MD) model. A previously studied system consisting of Na$^+$ and Cl$^-$ ions dissolved in water and confined between fixed crystalline silicon walls with negatively charged inner surfaces in an external electric field was investigated. Lennard-Jones (LJ) force fields and Coulomb electrostatic interactions with Simple Point Charge Extended (SPC/E) model were used to represent the interactions between ions, water molecules, and channel wall atoms. Dependence of the flow of water and ions on the temperature was examined. The magnitude of the water flux and even its direction are shown to be significantly affected by temperature. Temperature dependence of the flux was attributed to the charge redistribution and to the changes in viscosity of water. Using a simple inverse power approximation for water viscosity profile across the channel instead of constant viscosity, an improved prediction of MD electro-osmotic velocity profile from charge density by Stokes equation is demonstrated. [Preview Abstract] |
Friday, October 22, 2010 2:06PM - 2:18PM |
HD.00004: Modeling of Fluid Flow and Heat Transfer in Nanotube and Nanowire Forests Michael Martin Bundles of nanotubes, also known as nanotube forests, are under consideration for applications such as chip cooling and pre-concentrators for biodetection. Scaling law analysis shows that the air flow through these forests at atmospheric pressure is in the free-molecular flow regime. Based on the linearized free-molecular flow equations, a model is presented for the pressure drop and heat transfer in these systems. The momentum and energy equations are coupled, requiring that they be solved simultaneously. Results show large pressure drops, and a non-linear pressure distribution, similar to that seen in rarefied micro-channel flows. [Preview Abstract] |
Friday, October 22, 2010 2:18PM - 2:30PM |
HD.00005: Fluid Flow and Heat Transfer in Polygonal Micro Heat Pipes Sai Sashankh Rao, Harris Wong Micro heat pipes have been used to cool micro electronic devices, but their heat transfer coefficients are low compared with those of conventional heat pipes. A typical micro heat pipe has a long and narrow cavity of polygonal cross section. A long vapor bubble occupies the center of the cavity, while the liquid fills the rest. As one end of the pipe is heated, the liquid evaporates and increases the vapor pressure. The higher pressure drives the vapor to the cold end where the vapor condenses and releases the latent heat. The condensate moves along the liquid-filled corners of the pipe back to the hot end to complete the cycle. We solve the steady-flow problem assuming a small imposed temperature difference between the two ends of the pipe. This leads to skew-symmetric fluid flow and temperature distribution along the pipe so that we only need to focus on the evaporative half of the pipe. Since the pipe is slender, the axial flow gradients are much smaller than the cross-stream gradients. Thus, we can treat the evaporative flow in a cross-sectional plane as two-dimensional. Analytic solutions are derived for the temperature distribution and fluid flow along the pipe. Our model provides an explanation for the comparatively low effective thermal conductivity in micro heat pipes, and points to ways to improve their heat transfer capabilities. [Preview Abstract] |
Friday, October 22, 2010 2:30PM - 2:42PM |
HD.00006: Simulation of Heating in Nano-Electro Mechanical (NEMS) Bridges Elham Maghsoudi, Michael Martin Heat transfer in a thermally actuated doubly clamped bridge is simulated using a Finite Difference Method. These results are used to investigate the effect of convective cooling on the mechanical response of the system, defined as the displacement. The system is a doubly clamped beam with a length of 10 microns, a width of 1 micron, and a thickness of 300 nanometers, in air with a pressure from 0.01 Pa to 2 MPa. Conduction along the beam as well as convection between the beam and the gas are considered. A constant heat load is applied to the top of the beam. Both free molecular and continuum approaches are considered to define the convective coefficient. Simulations are performed for three different materials: silicon, silicon carbide, and diamond. The numerical results show that the displacement and the response of thermally actuated nano-scale devices are strongly influenced by ambient cooling. These results are scaled using the Biot number. The mechanical response of the system depends on the material properties and the Biot number. [Preview Abstract] |
Friday, October 22, 2010 2:42PM - 2:54PM |
HD.00007: Structural and magnetic stabilization of edges of layered zigzag graphene nanoribbons Jun-Qiang Lu, Yanna Zhang, Xiao-Li Lu, Yongjin Jiang, Botao Teng We report first-principle study on structural and magnetic stabilization of bilayer and trilayer zigzag graphene nanoribbons with two different edge alignments. Our results showed that (I) structural deformation only happens in layered ZGNRs with a- alignment edges; the ground state of the bi-layered ZGNR with a- alignment edges is nonmagnetic; while that of the tri-layered ZGNR with a-alignment edges is magnetic even with structural deformation; (II) layered ZGNRs with $\beta$-alignment edges are always flat and have magnetic ground states; (III) the intra-layer magnetic order in a layered ZGNR is always antiferromagnetic near each edge regardless of edge alignment and number of layers, as long as its ground state is magnetic; (IV) with the increasing of the number of layers, the magnetic order of the ground states can be complex and non-collinear. [Preview Abstract] |
Friday, October 22, 2010 2:54PM - 3:06PM |
HD.00008: Two-dimensional phase of gases physisorbed on a graphene Hye-Young Kim, Louis Bruch, Milton Cole The phases of gases physically adsorbed on a suspended, free-standing graphene are explored. In particular, three kinds of phase transitions are examined: (1) The quasi-two-dimensional condensation of a van der Waals fluid, (2) Contribution of the substrate-mediated interaction energy to the ground state energy of monolayer solid and liquid phases of He on graphene, and (3) Wetting transition of water and other fluids on graphene. In each case, the difference from those for adsorption on graphite will be presented. [Preview Abstract] |
Friday, October 22, 2010 3:06PM - 3:18PM |
HD.00009: High Density Bio-Nano Device Fabrication with Supramolecular NanoStamping Maitri Desai, Robyn Cross, Keith Carroll, Jennifer Curtis DNA microarrays are miniature complex devices that organize a high density of genetic information for biomedical applications such as genetic screening. Fabrication of DNA microarrays can be realized with different micropatterning methods such as microcontact printing and Thermochemical Nanolithography (TCNL). Recently, a low cost, high-throughput technique called supramolecular nanostamping (SuNS) has been developed to allow replication of DNA arrays by means of hybridization, contact to secondary surface, followed by dehybridization. However, the initial microarrays used for SuNS suffer from poor DNA density and the ability to make nanoscale resolution arrays practically. Our work focuses on combining the advantages of TCNL, which overcome these limitations, with SuNS. This will provide an ideal microarray fabrication process. To expedite the development stage, we have established a working SuNS protocol for our TCNL surfaces using microcontact printing rather than the more difficult, expensive TCNL. Once the SuNS is performed successfully and repeatedly using microcontact printing, ultimately, we will apply this method to nano resolution TCNL patterns and consequently combine TCNL and SuNS. [Preview Abstract] |
Friday, October 22, 2010 3:18PM - 3:30PM |
HD.00010: Integrated surface plasmon resonance spectral sensing using super-periodic nanohole array Haisheng Leong, Junpeng Guo, Yongbin Lin, Robert Lindquist, David Brady We will report the demonstration of an integrated surface plasmon resonance spectroscopic chemical sensors using patterned nanohole arrays. [Preview Abstract] |
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