Bulletin of the American Physical Society
2007 APS March Meeting
Volume 52, Number 1
Monday–Friday, March 5–9, 2007; Denver, Colorado
Session W42: Liquids and Tribology |
Hide Abstracts |
Sponsoring Units: DCMP Chair: Mu Wang, Nanjing University Room: Colorado Convention Center 505 |
Thursday, March 8, 2007 2:30PM - 2:42PM |
W42.00001: Monolayer Degradation and Sidewall Tribometer Studies of Vapor Phase Lubricants for MEMS D. Adam Hook, Brendan Miller, Shannon J. Timpe, Michael T. Dugger, Jacqueline Krim Monolayers have been widely used for MEMS to prevent release related stiction as well as adhesion as the devices are stored for long periods of time. Degradation of these monolayers in mechanical contact and at elevated temperatures however render the devices useless after a short period of time. While vapor-phase lubricants have primarily been studied within the context of macroscopic system performance, they may ultimately prove to be the most effective, if not the only, means to deliver and/or replenish a lubricant that can withstand a variety of extreme environmental conditions that a MEMS device is likely to encounter. We have made direct measurements of the change in the coefficient of friction of a MEMS sidewall tribometer as the lubricant is added to a vacuum chamber. Monolayer degradation under normal contact, requirements to prevent device failure, and friction measurements of vapor phase lubricants will be presented. [Preview Abstract] |
Thursday, March 8, 2007 2:42PM - 2:54PM |
W42.00002: Tribological properties of bound plus mobile lubricants for MEMS application. Brendan Miller, D. Adam Hook, Jacqueline Krim Long chain alkylsilane monolayers are used to protect MEMS devices from adhesion due to contamination. One such monolayer, perfluorodecyltrichlorosilane (PFTS) has been shown to have very advantageous thermal properties but will wear under mechanical rubbing. The mobility of vapor phase lubricants (VPL) used in conjunction with these self-assembled monolayers (SAMS) [1] may be the key to extending the lifetime of rubbing contacts in MEMS by replenishing worn away parts of the SAM. We studied tricresyl phosphate, a known anti-oxidant, and Nye lubricant, used for aerospace applications. We measured friction and obtained wear characteristics with a quartz crystal microbalance (QCM), a sliding tribometer under cryogenic temperatures, and an AFM in order to understand the effect of mobility, temperature, and atomic-point contacts to help bridge the gap between fundamental friction and MEMS application. \newline [1] ``Dynamics of Vapor-Phase Organophosphates on Silicon and OTS W. Neeyakorn1, M. Varma1, C. Jaye1, J. E. Burnette, S.M. Lee, R. J. Nemanich, C. Grant2 and J. Krim'' Tribology Letters, in press. [Preview Abstract] |
Thursday, March 8, 2007 2:54PM - 3:06PM |
W42.00003: Self-organization of surfactant aggregates on rough and smooth surfaces Hannes C. Schniepp, Ho C. Shum, Dudley A. Saville, Ilhan A. Aksay Atomic force microscopy (AFM) investigations of surfactant aggregates at liquid-solid interfaces have traditionally been performed on atomically smooth mica, graphite or gold. In order to extend the utility of this technique to more practical applications where atomically smooth surfaces rarely exist, we present results on rough gold surfaces for the first time. We achieve high-quality images of micellar structures on rough surfaces by using sharp, soft AFM probes. Contrary to the orientational order observed on atomically smooth surfaces, micellar organization on rough surfaces is also affected by the grain boundaries and atomic ledges. Our approach opens up the possibility of investigating surfactant self-assembly on arbitrary materials. [Preview Abstract] |
Thursday, March 8, 2007 3:06PM - 3:18PM |
W42.00004: Real-time observation of self-assembling nanostructures of Langmuir-Blodgett films of vinylidene fluoride-trifluoroethylene copolymer by Atomic Force Microscopy. Jihee Kim, Stephen Ducharme, Brian Rodriguez, Sergei Kalinin Annealing studies have shown that ferroelectric polymer Langmuir-Blodgett (LB) films less than 10 nm thick undergo drastic morphology change after annealing in the crystalline ferroeletric phase [M. Bai \textit{et al.}, \textit{Appl. Phys. Lett. }\textbf{85}, 3528 (2004)] During annealing in the crystalline paraelectric phase, continuous films self-assemble into disk shape features, nanomesas, with approximately 9 nm thickness and 100 nm diameter. The nanomesa self-assembly was observed in real time with an Atomic Force Microscope, which was equipped with a heating stage. This results show that the nanomesas formed during annealing agree well with nanomesas observed in ferroelectric phase at room temperature after annealing in the paraelectric phase. [Preview Abstract] |
Thursday, March 8, 2007 3:18PM - 3:30PM |
W42.00005: Study of Low Temperature Fuel Cells Thin Films Morphology by GISAXS Tomomi Irita, Thomas Russell Grazing incidence small angle x-ray scattering experiments were performed on thin films of Nafion solutions as a function of time as the solvent, methanol/water, evaporated. The development and orientation of the structure and morphology in the thin films, at the free surface and in the bulk of the film, was characterized by the scattering below and above the critical angle. The scattering profiles indicated that Nafion thin morphology was strongly influenced by the conformations of Nafion molecules in the solutions. In addition, the morphology in thin films of sulfonated block copolymers of polystyrene-b-poly(ethylene-o-butylene)-b-polystyrene, an alternative material for fuel cell applications, was characterized by GISAXS and scanning force microscopy using different solvents and under an applied electric field. Both the solvents used and the applied field was found to markedly influence the orientation of the ion conducting domains in the films. [Preview Abstract] |
Thursday, March 8, 2007 3:30PM - 3:42PM |
W42.00006: Feasibility of Large Free-standing Liquid Films in Space Rui Zheng, Thomas Witten We consider the feasibility of large-scale free-standing thin liquid film experiment in the space environment as a new realization to study two-dimensional hydrodynamics. We identify material and environmental criteria necessary to avoid freezing, evaporation, chemical degradation, and spontaneous collapse of the film. These criteria pose no obstacles to achieving films of kilometer scale and lifetime of many months, with attainable Reynolds number up to $10^7$. However, impacts from meteoroids pose a serious threat to the film, and require substantial shielding or unproven self-healing properties in the film. Current theoretical and experimental studies of two-dimensional turbulence are briefly reviewed. We also describe a specific candidate liquid for the film. [Preview Abstract] |
Thursday, March 8, 2007 3:42PM - 3:54PM |
W42.00007: Characterization of Surface Nanobubbles Shangjiong Yang, Stephan Dammer, Harold Zandvliet, Stefan Kooij, Bene Poelsema, Detlef Lohse In this work we characterize surface nanobubbles on hydrophobic surface in water by Atomic Force Microscopy (AFM) operated in the tapping mode. A connection between the formation of nanobubbles and the surface topography is presented. Together with large contact angle of nanobubbles, which determines their shape, the surface topology may support the surprising stability of nanobubbles. It is shown that the properties of the nanobubbles and their density are sensitive to the gas concentration and type. We show that different surface treatments also influence nanobubbles in formation and shape. Next, adding surfactants (2-butanol) causes nanobubbles to shrink, as expected from the Laplace equation. Finally, we show that exchanging alcohols by water on the surface strongly encourages the formation of nanobubbles. [Preview Abstract] |
Thursday, March 8, 2007 3:54PM - 4:06PM |
W42.00008: High Density Monolayer Deposition of Fine Nanoparticles for Opto-Electronic Devices Xavier Bulliard, Wanki Bae, Kookheon Char, Seong Jae Choi, Jae Young Choi In this study, we present a unique approach to form uniform monolayers of nanoparticles (NPs) deposited on a substrate with high surface coverage density up to 2x10$^{12}$ NPs/cm$^{2}$. This was achieved through the wet coating of fine NPs with a diameter less than 10 nm. The mechanism of monolayer formation was decomposed into two stages: first the deposition driven by the electrostatic forces between a substrate and NPs and then the self-arrangement of NPs through the action of capillary forces. A physical description of the interaction forces involved in the process confirmed that for fine NPs the capillary forces are dominant over the electrostatic repulsion between adjacent NPs during drying. This enables the high compaction of a monolayer without altering its uniformity. Dip- and spin- coating techniques could as well be used for the deposition on various substrates (for example, hafnium and silicon oxides), which proves the versatility of this approach. The obtained architecture show promising properties and could be implemented for the production of the next generation of opto-electronic devices. [Preview Abstract] |
Thursday, March 8, 2007 4:06PM - 4:18PM |
W42.00009: Microcontact printing Using Metallic Salt Solution ``Ink'' Cary Allen, Josh Dorr, Ian Schick, Evan Schick, Reuben Collins, Anish Khandekar, Thomas Kuech Arrays of micron size metal dots were patterned onto Si substrates using microcontact printing. Poly(dimethlysiloxane) stamps were prepared from Si masters fabricated using photolithography and anisotropic etching. Aqueous GaCl$_{3}$ and In(NO$_{3})_{3}$ inks were microcontact printed onto Si substrates, creating arrays of micron size metal salt deposits. The In(NO$_{3})_{3}$ deposits were further processed by annealing in an N$_{2}$:H$_{2}$ (9:1) forming gas environment at 600 \r{ }C which converted the deposits into In metal. Details of the stamp preparation and printed patterns, along with, characterization using atomic force microscopy and X-ray diffraction will be presented. The ability to inexpensively pattern metal arrays on semiconductor surfaces has implications for ohmic contacts and, with additional processing, arrays of semiconductor crystallites for optoelectronic applications. [Preview Abstract] |
Thursday, March 8, 2007 4:18PM - 4:30PM |
W42.00010: X-ray diffuse scattering from thin polystyrene films Mrinmay K. Mukhopadhyay, Zhang Jiang, Sunil K. Sinha, Laurence B. Lurio, Jarett Stark, Xuesong Jiao, Suresh Narayanan, Alec Sandy Diffuse x-ray scattering from silicon supported polystyrene films has been measured as a function of thickness. An x-ray standing wave method was used to distinguish scattering from the surface and scattering from density fluctuations within the interior of the film. The former is a measure of surface roughness, while the latter yields the compressibility, $\kappa { }_T$. Films thicker than $h \quad \sim $100 nm had bulk values for $\kappa { }_T$, while thinner films showed the empirical relation $\kappa { }_T(h)=\kappa _T^{bulk} \left( {1+\alpha \mathord{\left/ {\vphantom {\alpha h}} \right. \kern-\nulldelimiterspace} h} \right)^\delta $ with \textit{$\alpha $} = 20 ($\pm $1) nm and \textit{$\delta $ }= 1.6 ($\pm $1). The surface component of the scattering agreed with capillary wave theory for small $q$, but excess scattering appeared at larger $q, $which followed a power law, $S^\ast \sim \,q^{1 \mathord{\left/ {\vphantom {1 \upsilon }} \right. \kern-\nulldelimiterspace} \upsilon }$. We attribute the excess scattering to static roughness from chain ends and loops near the surface. [Preview Abstract] |
Thursday, March 8, 2007 4:30PM - 4:42PM |
W42.00011: ABSTRACT WITHDRAWN |
Thursday, March 8, 2007 4:42PM - 4:54PM |
W42.00012: New Cyclic Voltammetry Method for Examining Phase Transitions on Electrodes: Simulated Results Ibrahim Abou Hamad, Daniel Robb, Per Arne Rikvold We propose a new experimental technique for cyclic voltammetry, based on the first-order reversal curve (FORC) method for analysis of systems undergoing hysteresis. The advantages of this technique are demonstrated by applying it to dynamical models of electrochemical adsorption. The method can not only differentiate between discontinuous and continuous phase transitions, but can also quite accurately recover equilibrium behavior from dynamic analysis of systems with a continuous phase transition. The FORC diagram for a discontinuous phase transition is characterized by a negative (unstable) region separating two positive (stable) regions, while such a negative region does not exist for continuous phase transitions. Experimental data for Electrochemical FORC (EC-FORC) analysis could easily be obtained by simple reprogramming of a potentiostat designed for conventional cyclic-voltammetry experiments.\\ \\ I. Abou Hamad, D.T. Robb, P.A. Rikvold, J. Electroanal. Chem., in press. [Preview Abstract] |
Thursday, March 8, 2007 4:54PM - 5:06PM |
W42.00013: Relating contact angles, drop size and Line Energy Preeti Yadav, Prashant Bahadur, Kumud Chaurasia, Rafael Tadmor The relation between drop radius, $r$, the force to slide it, and the advancing and receding contact angles, \textit{$\theta $}$_{A}$ and \textit{$\theta $}$_{R}$, has been studied. To keep the line energy (energy per 2$\pi r)$ independent of $r$, the modified Young equation predicts that \textit{$\theta $}$_{A}$ and \textit{$\theta $}$_{R}$ change considerably with $r$. As shown by many investigators, \textit{$\theta $}$_{A}$ and \textit{$\theta $}$_{R}$ change negligibly, if at all, with $r$. We show why the modified Young equation is correct and still \textit{$\theta $}$_{A}$ and \textit{$\theta $}$_{R}$ should hardly change with $r$. Our results suggest that the Laplace pressure is a significant parameter in inducing the line energy. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700