The Experts below are selected from a list of 15333 Experts worldwide ranked by ideXlab platform
Joonkyung Jang - One of the best experts on this subject based on the ideXlab platform.
-
monte carlo study on the water meniscus condensation and Capillary Force in atomic Force microscopy
Journal of Physical Chemistry C, 2012Co-Authors: Hyojeong Kim, Berend Smit, Joonkyung JangAbstract:The water meniscus condensed between a nanoscale tip and an atomically flat gold surface was examined under humid conditions using grand canonical Monte Carlo simulations. The molecular structure of the meniscus was investigated with particular focus on its width and stability. The Capillary Force due to the meniscus showed a dampened oscillation with increasing separation between the tip and surface because of the formation and destruction of water layers. The layering of water between the tip and the surface was different from that of the water confined between two plates. The humidity dependence of the Capillary Force exhibited a crossover behavior with increasing humidity, which is in agreement with the typical atomic Force microscopy experiment on a hydrophilic surface.
-
lattice gas monte carlo simulation of Capillary Forces in atomic Force microscopy
Journal of Adhesion Science and Technology, 2010Co-Authors: Joonkyung Jang, George C SchatzAbstract:We review recent work concerned with lattice gas (LG) Monte Carlo (MC) simulations of the water meniscus formed between an atomic Force microscope (AFM) tip and the surface in contact with the tip. Grand canonical MC simulations were performed to study the meniscus structure and Capillary Force, and this work allowed us to examine the mechanism of meniscus formation as a function of the tip–surface distance and humidity. It is found that the meniscus becomes unstable when it is narrower than the diameter of the tip–surface contact area. The calculations suggest that the ultimate size limit for a stable meniscus is five molecular diameters. We developed thermodynamic integration and perturbation methods to calculate the Capillary Force. The magnitude and humidity dependence of Capillary Force are significantly affected by the hydrophilicity of both the tip and surface. A mean field density functional theory (DFT) closely approximates the Capillary Forces calculated from the MC simulation. Changing the atom...
-
atomic scale roughness effect on Capillary Force in atomic Force microscopy
Journal of Physical Chemistry B, 2006Co-Authors: Joonkyung Jang, Mark A Ratner, George C SchatzAbstract:We study the Capillary Force in atomic Force microscopy by using Monte Carlo simulations. Adopting a lattice gas model for water, we simulated water menisci that form between a rough silicon-nitride tip and a mica surface. Unlike its macroscopic counterpart, the water meniscus at the nanoscale gives rise to a Capillary Force that responds sensitively to the tip roughness. With only a slight change in tip shape, the pull-off Force significantly changes its qualitative variation with humidity.
-
Capillary Force in atomic Force microscopy
Journal of Chemical Physics, 2004Co-Authors: Joonkyung Jang, George C Schatz, Mark A RatnerAbstract:Under ambient conditions, a water meniscus generally forms between a nanoscale atomic Force microscope tip and a hydrophilic surface. Using a lattice gas model for water and thermodynamic integration methods, we calculate the Capillary Force due to the water meniscus for both hydrophobic and hydrophilic tips at various humidities. As humidity rises, the pull-off Force rapidly reaches a plateau value for a hydrophobic tip but monotonically increases for a weakly hydrophilic tip. For a strongly hydrophilic tip, the Force increases at low humidities (<30%) and then decreases. We show that mean-field density functional theory reproduces the simulated pull-off Force very well.
-
Capillary Force on a nanoscale tip in dip pen nanolithography
Physical Review Letters, 2003Co-Authors: Joonkyung Jang, George C Schatz, Mark A RatneAbstract:: Monte Carlo simulation has been used to characterize the Capillary Force due to the condensation of a liquid meniscus between a tip with a nanoscale asperity and a flat surface. To consider both hydrophobic and hydrophilic molecules coating the tip as a model of dip-pen nanolithography, tips with various wettabilities are studied. The Capillary Force due to the meniscus is calculated for various saturations (humidities). We have implemented a thermodynamic integration technique that can project the Force into energetic and entropic contributions. In most cases, the Force is mainly energetic in origin. At the snap-off separation where the meniscus disappears, the tip feels a significant entropic Force at high saturation. Our calculation shows nonmonotonic behavior of the pull-off Force as a function of saturation, which is in qualitative accord with experiments.
George C Schatz - One of the best experts on this subject based on the ideXlab platform.
-
lattice gas monte carlo simulation of Capillary Forces in atomic Force microscopy
Journal of Adhesion Science and Technology, 2010Co-Authors: Joonkyung Jang, George C SchatzAbstract:We review recent work concerned with lattice gas (LG) Monte Carlo (MC) simulations of the water meniscus formed between an atomic Force microscope (AFM) tip and the surface in contact with the tip. Grand canonical MC simulations were performed to study the meniscus structure and Capillary Force, and this work allowed us to examine the mechanism of meniscus formation as a function of the tip–surface distance and humidity. It is found that the meniscus becomes unstable when it is narrower than the diameter of the tip–surface contact area. The calculations suggest that the ultimate size limit for a stable meniscus is five molecular diameters. We developed thermodynamic integration and perturbation methods to calculate the Capillary Force. The magnitude and humidity dependence of Capillary Force are significantly affected by the hydrophilicity of both the tip and surface. A mean field density functional theory (DFT) closely approximates the Capillary Forces calculated from the MC simulation. Changing the atom...
-
atomic scale roughness effect on Capillary Force in atomic Force microscopy
Journal of Physical Chemistry B, 2006Co-Authors: Joonkyung Jang, Mark A Ratner, George C SchatzAbstract:We study the Capillary Force in atomic Force microscopy by using Monte Carlo simulations. Adopting a lattice gas model for water, we simulated water menisci that form between a rough silicon-nitride tip and a mica surface. Unlike its macroscopic counterpart, the water meniscus at the nanoscale gives rise to a Capillary Force that responds sensitively to the tip roughness. With only a slight change in tip shape, the pull-off Force significantly changes its qualitative variation with humidity.
-
Capillary Force in atomic Force microscopy
Journal of Chemical Physics, 2004Co-Authors: Joonkyung Jang, George C Schatz, Mark A RatnerAbstract:Under ambient conditions, a water meniscus generally forms between a nanoscale atomic Force microscope tip and a hydrophilic surface. Using a lattice gas model for water and thermodynamic integration methods, we calculate the Capillary Force due to the water meniscus for both hydrophobic and hydrophilic tips at various humidities. As humidity rises, the pull-off Force rapidly reaches a plateau value for a hydrophobic tip but monotonically increases for a weakly hydrophilic tip. For a strongly hydrophilic tip, the Force increases at low humidities (<30%) and then decreases. We show that mean-field density functional theory reproduces the simulated pull-off Force very well.
-
Capillary Force on a nanoscale tip in dip pen nanolithography
Physical Review Letters, 2003Co-Authors: Joonkyung Jang, George C Schatz, Mark A RatneAbstract:: Monte Carlo simulation has been used to characterize the Capillary Force due to the condensation of a liquid meniscus between a tip with a nanoscale asperity and a flat surface. To consider both hydrophobic and hydrophilic molecules coating the tip as a model of dip-pen nanolithography, tips with various wettabilities are studied. The Capillary Force due to the meniscus is calculated for various saturations (humidities). We have implemented a thermodynamic integration technique that can project the Force into energetic and entropic contributions. In most cases, the Force is mainly energetic in origin. At the snap-off separation where the meniscus disappears, the tip feels a significant entropic Force at high saturation. Our calculation shows nonmonotonic behavior of the pull-off Force as a function of saturation, which is in qualitative accord with experiments.
Anh V Nguyen - One of the best experts on this subject based on the ideXlab platform.
-
the contact angle variation of floating particles makes it difficult to use the neumann condition to quantify the air water interface deformation in three dimensional space
Langmuir, 2019Co-Authors: Anh V NguyenAbstract:Capillary Force is critical to the floatability of particles at the air–water interface. Quantification of the Capillary Force requires solving the Young–Laplace equation using suitable boundary conditions (BCs) at the triple contact line. For axisymmetric (two-dimensional, 2D) systems, such as single spheres floating at an initially flat air–water surface, both the Dirichlet (constant contact depth) and Neumann (constant contact angle) BCs can be applied. For three-dimensional (3D) systems, Neumann BCs (NBCs) have been successfully used. In this paper, we have challenged the use of NBCs for the 3D deformation of the air–water surface induced by floating particles, which always exhibit intrinsic contact angle (CA) hysteresis that is significantly amplified in 3D systems. Specifically, we designed and conducted the experiments using single prismatic particles, which allowed for the determination of two characteristic CAs at the two diagonal axes with a high degree of certainty. We calibrated the numerical ...
-
systematically altering the hydrophobic nanobubble bridging Capillary Force from attractive to repulsive
Journal of Colloid and Interface Science, 2009Co-Authors: Marc A Hampton, Anh V NguyenAbstract:Atomic Force microscopy (AFM) was used to examine how ethanol/water concentration affects the nanobubble bridging Capillary Force between a hydrophobic silica colloidal probe and a hydrophobic silica wafer. Nanobubbles were produced on the solid surfaces by a previously utilised method which uses solvent-exchange and surface scanning. In pure water a strong, long range attractive Force (≈230 nm) with a single jump in step was measured, typical of an interaction between two nanobubbles attached to the hydrophobic surfaces. An increase in the ethanol concentration had little effect on the range of the Force but dramatically reduced its magnitude. At an ethanol concentration of 40% by mass, the Force became repulsive after the initial attractive jump in. Above an ethanol concentration of 40% by mass, the Capillary Force disappeared. The change in the Force with ethanol concentration was explained using a Capillary Force model with constant volume and contact angle. The bridge geometry, contact angle, volume and rupture distance were determined for different ethanol concentrations.
Fengchao Wang - One of the best experts on this subject based on the ideXlab platform.
-
a generalized examination of Capillary Force balance at contact line on rough surfaces or in two liquid systems
Journal of Colloid and Interface Science, 2021Co-Authors: Jingcun Fan, Joel De Coninck, Fengchao WangAbstract:Abstract We investigate the Capillary Force balance at the contact line on rough solid surfaces and in two-liquid systems. Our results confirm that solid-liquid interactions perpendicular to the interface have a significant influence on the lateral component of the Capillary Force exerted on the contact line. Surface roughness of the solid substrate reduces the mobility of liquid and alters how the perpendicular solid-liquid interactions transfer into a Force acting parallel to the interface. A quantitative relation between surface roughness and the transfer strategy is proposed. Moreover, when a liquid is in coexistence with another immiscible liquid on a solid, the Capillary Forces exerted on liquids of both sides are involved in our theoretical model. The contact angle can be predicted by calculating three interfacial tensions. These arguments are then verified by molecular dynamics simulations. Our findings set up the generalized theoretical framework for the Capillary Force balance at the contact line and broaden its application in more realistic scenarios.
-
microscopic origin of Capillary Force balance at contact line
Physical Review Letters, 2020Co-Authors: Jingcun Fan, Joel De Coninck, Fengchao WangAbstract:We investigate the underlying mechanism of Capillary Force balance at the contact line. In particular, we offer a novel approach to describe and quantify the Capillary Force on the liquid in coexistence with its vapor phase, which is crucial in wetting and spreading dynamics. Its relation with the interface tension is elucidated. The proposed model is verified by our molecular dynamics simulations over a wide contact angle range. Differences in Capillary Forces are observed in evaporating droplets on homogeneous and decorated surfaces. Our findings not only provide a theoretical insight into Capillary Forces at the contact line, but also validate Young's equation based on a mechanical interpretation.
Michael Kappl - One of the best experts on this subject based on the ideXlab platform.
-
normal Capillary Forces
Advances in Colloid and Interface Science, 2009Co-Authors: Hansjurgen Butt, Michael KapplAbstract:A liquid meniscus between two lyophilic solid surfaces causes an attractive Force, the Capillary Force. The meniscus can form by Capillary condensation or by accumulation of adsorbed liquid. Under ambient conditions and between hydrophilic surfaces, Capillary Forces usually dominate over other surface Forces. They are relevant in many processes occurring in nature and technical applications, for example the flow of granular materials and friction between surfaces. Here we review normal Capillary Forces, focusing on a quantitative description with continuum theory. After introducing the Capillary Force between spherical surfaces, we extend the discussion to other regular and irregular surfaces. The influence of surface roughness is considered. In addition to Capillary Forces at equilibrium, we also describe the process of meniscus formation. Assumptions, limits, and perspectives for future work are discussed.
-
using Capillary Forces to determine the geometry of nanocontacts
Journal of Applied Physics, 2006Co-Authors: Hansjurgen Butt, Mahdi Farshchitabrizi, Michael KapplAbstract:The Capillary Force between two fine particles or between the tip of an atomic Force microscope (AFM) and a surface depends on the precise geometry of the contact region. In this paper we demonstrate that vice versa from a measurement of the adhesion Force versus humidity one can calculate the shape of the AFM tip (or the geometry of the contact between particles). This is verified by adhesion experiments with an AFM.
