Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session E17: Solid-Liquid Interfaces |
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Sponsoring Units: DCMP Chair: Steven Cronin, University of Southern California Room: LACC 306A |
Tuesday, March 6, 2018 8:00AM - 8:12AM |
E17.00001: Molecular Dynamic Thin Film Evaporation and Condensation in Nano gap Elnaz Norouzi .Due to the vast advancement in modern technology, the computers and electronic devices are getting more and more miniaturized. Therefore, the importance of efficient heat transfer becomes crucial. Nowadays, Implementing phase change heat transfer in flat heat pipes with thickness less than millimeter has been one of the most efficient approaches for cooling process. Thus, more profound study on phase change heat transfer from microscopic scale and nanoscale could help to improve cooling procedure. In this study, the domain is a nano gap, with two platinum walls at top and bottom and Argon fluid in between. In non-equilibrium molecular dynamic simulation, when a temperature gradient is applied through the nano gap, there exists a non-evaporating layer on the hot wall which becomes thinner as temperature gradient is increased. The higher temperature gradient indicates a higher heat transfer coefficient. Accommodation coefficient, as the ratio of the number of the atoms cross the two phase interface to those atoms reach at the interface, is investigated in different temperatures. The combination of accommodation coefficients from molecular dynamic simulation and Schrage equation provides insight to the details of intermolecular interaction when phase change occurs in nanoscale. |
Tuesday, March 6, 2018 8:12AM - 8:24AM |
E17.00002: Molecular Dynamics of the Water-gold Interface including Metal Polarizability Effects in the Classical Force Field Victor Ruiz, Matej Kanduč, Won Kyu Kim, Rafael Roa, Joachim Dzubiella Solid-liquid interfaces are of growing interest to basic science and technology. The water-gold interface has received much attention due to its applications in catalysis and biotechnology. The need of including biomolecular and ionic species in the aqueous environment within atomistic simulations necessitates the accurate inclusion of charge and fluctuations effects of the liquids [Small 12, 2395 (2016)]. The formed interfaces are complex due to the interplay of van der Waals (vdW) interactions, covalent bonds, and image-charge effects due to the highly polarizable surface. Using a classical Drude-oscillator model [JCP 119, 3025 (2003)], we present a force field for the gold-water interface which includes image-charge effects induced in the metal surface. Our parametrization is based on calculations of a single molecule/monolayer of water using vdW-corrected density-functional theory [PRL 108, 146103 (2012)] that includes the many-body collective response of the substrate electrons in the vdW interaction coefficients. We show that this methodology yields a consistent connection between the induced polarizability effects in the surface and the vdW interaction between water molecules and the surface when compared to available literature. |
Tuesday, March 6, 2018 8:24AM - 8:36AM |
E17.00003: Understanding the Role of DOPA in Underwater Adhesion Sukhmanjot Kaur, Amal Narayanan, Abraham Joy, Ali Dhinojwala Removal of interfacial water is a major challenge in making adhesives that can stick underwater. However, there are many examples of biological adhesives that work in wet environments such as mussels, caddisfly and sandcastle worm. It is found that mussels stick to rocks underwater using byssal threads and the proteins that binds these threads to surfaces contain 20 % 3,4-dihydroxyphenylalanine (DOPA), indicating the importance of this molecule in mussel adhesion. Many new polymers have been synthesized that incorporates the DOPA unit to improve adhesion underwater. Although these materials show promising results, the role of catechol in interfacial adhesion is still under debate. In my research, we have focused on the role of hydrophobic groups along with DOPA in underwater adhesion. We have designed polymers that contain DOPA mimetic groups along with a significant fraction of hydrophobic side chains, and a UV cross-linkable molecule. We have used surface sensitive sum-frequency generation spectroscopy to probe the contact interface of this polymer with a solid substrate underwater to understand the role of DOPA. Also we related the spectroscopic observations with adhesion measured using JKR geometry. |
Tuesday, March 6, 2018 8:36AM - 8:48AM |
E17.00004: Graphene-integrated Microfluidic Platforms for Electrical Probing in Retina Yuchen Zhang, Kirsten Dodson, Rachel Fisher, Rui Wang, Deyu Li, Rebecca Sappington, Yaqiong Xu Graphene is of growing interest in biological and biomedical fields due to its extraordinary physical properties and excellent biocompatibility. Combining graphene field-effect transistors and scanning photocurrent microscopy with microfluidic platforms, we designed a new approach to investigate electrical signals in the mouse retina. At the optic nerve head (ONH) of the retina, significant photocurrent signals were detected, indicating the electrical activity from this region can modulate the carrier concentration of the graphene and induce local potential gradients. The built-in electrical field can efficiently separate photo-excited electron-hole pairs, leading to intense photocurrent responses in the graphene underneath the ONH. We also show that no apparent photocurrent signal was observed in the graphene underneath either dehydrated or fixed retinal tissues, verifying that the photocurrent responses generated in the graphene underneath the ONH were indeed induced by the electrical activity in living retina. |
Tuesday, March 6, 2018 8:48AM - 9:00AM |
E17.00005: Enhancing Interface Sensitivity of Energy Materials by Resonant X-Ray Scattering Isvar Cordova, Guillaume Freychet, Gregory Su, Cheng Wang The advent of novel mesoscale materials requires the constant concomitant progress in the characterization techniques used to address the new challenges and questions inherent to these materials. In this presentation, we reveal a powerful, yet simple, patterning approach for interface characterization that takes advantage of the physical processes intrinsic to resonant X-ray scattering and dramatically enhances the interface signal in order to enable data collection on millisecond timescales. Unlike standard microscopic techniques, this highly sensitive spatio-chemical information can be obtained over a statistically-significant area and doesn't require a highly focused beam whose flux can often be deleterious to the sample. We demonstrate its ability to selectively probe the interfacial regions of inorganic materials used throughout the fields of energy conversion and storage with sub-nm 3D precision. In addition, we leverage newly-developed in-situ/operando capabilities for gas/liquid flow and electrical biasing compatible with most "soft" and "tender" X-ray beamlines to show how this approach can be a powerful interrogation tool to monitor reactions near interfaces. |
Tuesday, March 6, 2018 9:00AM - 9:12AM |
E17.00006: Effect of Thermocapillary stress on the Stability of a Non-isothermal Thin Liquid Film Flowing Inside a Heated Rotating Horizontal Cylinder Tara chand Kumawat, Naveen Tiwari The stability analysis has been carried out for a thin film flowing inside a uniformly heated rotating horizontal cylinder. Mass, momentum, and energy equations are simplified under lubrication approximation to obtain film thickness evolution equation. The mathematical model includes effects of gravity, viscous drag, inertia, surface tension and thermocapillary force. The film thickness evolution equation is solved numerically to obtain two-dimensional solutions neglecting |
Tuesday, March 6, 2018 9:12AM - 9:24AM |
E17.00007: Calcium-Induced Molecular Rearrangement of Peptide Folds Enables Biomineralization of Vaterite Calcium Carbonate Hao Lu, Helmut Lutz, Steven Roeters, Matthew A. Hood, Arne Schäfer, Rafael Muñoz-Espí, Rüdiger Berger, Mischa Bonn, Tobias Weidner Proteins can control mineralization of CaCO3 by selectively triggering the growth of calcite, aragonite or vaterite phases. The templating of CaCO3 by proteins must occur predominantly at the protein/CaCO3 interface, however molecular-level insights into the interface during active mineralization have been lacking. Here, we investigate the role of peptide folding and structural flexibility on the mineralization of CaCO3. We study amphiphilic peptides based on glutamic acid and leucine with beta sheet and alpha helical secondary structures. While both sequences lead to vaterite structures, the beta sheets yield free-standing vaterite nanosheet with superior stability and purity. Surface-specific spectroscopy studies and molecular dynamics simulations of these 10’s of microns large peptide-vaterite sheets reveal that the interaction of calcium ions with the peptide monolayer restructures both the peptide backbone and side chains. This restructuring enables effective templating of vaterite by mimicry of the vaterite (001) crystal plane. The results demonstrate the importance of interfacial processes for biomineralization and biomimetic peptide design. |
Tuesday, March 6, 2018 9:24AM - 9:36AM |
E17.00008: Evaporative pattern formation by Aqueous Sodium Chloride solution at ambient and elevated temperature conditions Nandita Basu, Rabibrata Mukherjee Droplet evaporation on solid substrate is of interest since last few decades due to its growing importance in several applicative fields. Presence of crystalline materials within a liquid drop makes the evaporation process critical as along with complex flow patterns inside an evaporative droplet an additional phenomena of crystallization takes place. By employing simple drop-deposition technique on solid substrate at ambient conditions conversion from ring-like to uniform deposit was observed with increasing NaCl salt concentration. NaCl-rings were obtained at higher salt concentration instead of a single deposit on addition of surfactant in the salt solution i.e., the deposition patterns were altered in presence of surfactant. At elevated temperatures, double ring to single ring conversion was noticed with stepwise increase in salt concentration. At higher salt concentration the inner ring disappeared and merged with the outer one to form a single thicker ring with the evolution of a no-deposition zone at the center of the droplet. The flow dynamics within the droplets and the mechanism of the drying pattern formation are qualitatively discussed. |
Tuesday, March 6, 2018 9:36AM - 9:48AM |
E17.00009: Abstract Withdrawn
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Tuesday, March 6, 2018 9:48AM - 10:00AM |
E17.00010: Dynamics of fluid films flowing down a fibre influenced by nozzle geometry Hangjie Ji, Claudia Falcon, Abolfazl Sadeghpour, Zezhi Zeng, Sungtaek Ju, Andrea Bertozzi Viscous thin liquid films flowing down vertical strings can exhibit interesting dynamics via the formation of droplets driven by a Rayleigh mechanism with the presence of gravity. Motivated by experimental results on the effects of nozzle geometry on the dynamics of these viscous droplets by Sadeghpour et al. (2017), we further study a thin film model for the gravity-driven flow in the Rayleigh-Plateau Regime. The governing equation is a fourth-order nonlinear parabolic PDE for the film thickness. Time-dependent computations of the spatial evolution of the film reveal a strong influence of inlet boundary conditions that characterize different nozzle geometry. Numerical solutions of traveling wave solutions also yield information on the profile and propagation velocity of fluid beads, which agrees with available experimental data. |
Tuesday, March 6, 2018 10:00AM - 10:12AM |
E17.00011: In situ investigation of the solid/electrolyte interface in photo-electrochemical conditions using surface X-ray diffraction Axel Wilson, Immad Nadeem, Hadeel Hussain, Xavier Torrelles, Geoffrey Thornton, Chris Nicklin, Jorg Zegenhagen A custom setup was developed at Diamond Light Source for photo-electrochemical experiments probing the structure of solid/liquid interfaces in situ using surface X-ray diffraction (SXRD). Clean surfaces are prepared in ultra-high vacuum (UHV) by standard methods and pre-characterised using e.g. X-ray photoelectron spectroscopy and scanning tunnelling microscopy. Samples can be transferred under UHV into the chamber and mounted on a diffractometer for SXRD structure determination under UHV. The pristine surface is then contacted with a drop of electrolyte to study the solid/liquid interface with SXRD also under influence of an external potential and UV/visible light exposure. |
Tuesday, March 6, 2018 10:12AM - 10:24AM |
E17.00012: Electrochemical Tuning of Graphene Enhanced Raman Spectroscopy Haotian Shi, Lang Shen, Bingya Hou, Jihan Chen, Steve Cronin In this talk I will review our recent progress in electrochemical tuning of graphene enhanced Raman spectroscopy (GERS). We developed a novel approach to probe the local ion concentration at graphene/water interfaces using in situ Raman spectroscopy. Monolayer graphene grown by chemical vapor deposition (CVD is used as the working electrode in a three-terminal potentiostat while Raman spectra are measured in situ under applied electrochemical potentials using a water immersion lens.The charge density in the graphene electrode is also measured independently using the capacitance-voltage characteristics and is found to be consistent with those measured by Raman spectroscopy. Then, CuPc molecules are deposited on the graphene. GERS spectra are then taken in an aqueous solution as a function of the applied electrochemical potential. A 50% modulation in the Raman intensity as a function of the applied potential. |
Tuesday, March 6, 2018 10:24AM - 10:36AM |
E17.00013: Suppression of Instability in Polymeric Films Under A Liquid Water-Organic Mixture by Altering the Substrate Wettability Sumita Sahoo, Anuja Das, Rabibrata Mukherjee A thin polymer film exposed to a poor solvent can be an effective means of destabilizing an otherwise stable film (in air) by destabilizing polar interactions. Here we investigated instability mediated rupture of stable polystyrene film in a water-organic solution at room temperature. We showed that this instability depends mainly on the Diffusion Length (L) and Spreading Coefficient (S) of the liquid. We observed that for a film of thickness hE < L, dewetting occurs due to rapid diffusion and spreading of solvent at the substrate-polymer interface whereas for thicker films (hE > L) wrinkles were observed. Dewetting under such a liquid mix allows penetration of different solvents, based on their respective Permeability (PS), towards the substrate which causes the adhered polymer chains to loosen up decreasing the viscous friction at polymer-substrate interface leading to a faster dewetting dynamics. We observed that on a solvo-phobic substrate the polymer chains remain adhered to substrate while exposed to the solvent mixture, due to which the film was partially stabilized. Generally, on a phobic substrate a film is unstable in air but while exposed to an effectively poor solvent it is more stable compared to a film on a phillic substrate. |
Tuesday, March 6, 2018 10:36AM - 10:48AM |
E17.00014: Effect of Structure and Functional on the SFG Spectrum at the Alumina-Water Interface Mark DelloStritto, Stefan Piontek, Eric Borguet, Michael Klein
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