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Wetting on flexible hydrophilic pillar-arrays.

Yuan Q, Zhao YP - Sci Rep (2013)

Bottom Line: For the first time, the combined effect of the surface topology, the intrinsic wettability and the elasticity of a solid on the wetting process is taken into consideration.Scaling analysis is performed based on molecular kinetic theory and validated by our simulations.Our results may expand our knowledge of wetting on pillars and assisting the future design of active control of wetting in practical applications.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing, People's Republic of China.

ABSTRACT
Dynamic wetting on the flexible hydrophilic pillar-arrays is studied using large scale molecular dynamics simulations. For the first time, the combined effect of the surface topology, the intrinsic wettability and the elasticity of a solid on the wetting process is taken into consideration. The direction-dependent dynamics of both liquid and pillars, especially at the moving contact line (MCL), is revealed at atomic level. The flexible pillars accelerate the liquid when the liquid approaches, and pin the liquid when the liquid passes. The liquid deforms the pillars, resulting energy dissipation at the MCL. Scaling analysis is performed based on molecular kinetic theory and validated by our simulations. Our results may expand our knowledge of wetting on pillars and assisting the future design of active control of wetting in practical applications.

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(a) The relationship between the work of adhesion Wa and the Young's modulus Y in the ordinary range of FCC LJ solids.The red line is a linear fit of the MD results. (b) Evolution of Rf with respect to t for different Y.
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f4: (a) The relationship between the work of adhesion Wa and the Young's modulus Y in the ordinary range of FCC LJ solids.The red line is a linear fit of the MD results. (b) Evolution of Rf with respect to t for different Y.

Mentions: In the framework of MKT, the energy dissipation results from the friction at the MCL, measured by Wa, which has a link with the Young's modulus Y. A variety of solids can be modeled as LJ solid37, such as the face-centered-cubic (FCC) solid38 used in our simulations, in which only the nonbonding interactions are considered. From the atomic aspect of view39, Wa is expressed by , where AS−L is the Hamaker constant between solid and liquid, ρS and ρL are the number density of the solid and the liquid, dL is the size of the liquid molecule, is the depth of the LJ potential well, is the zero-crossing distance. Y of the LJ solid is 39, where ds is the lattice constant of the solid. Substituting parameters used in our simulations, we obtain Wa ~ 0.1 J/m2 and Y ~ 100 GPa. Comparing their expressions, Wa monotonically increases with the increase of Y. However, there is no analytical solution of the relation between Wa and Y. Hence, we used the MD simulations to obtain their relation by changing εS−S and found a roughly linear increase of Wa with respect to Y, i.e. Wa ~ λY, shown in Fig. 4(a).


Wetting on flexible hydrophilic pillar-arrays.

Yuan Q, Zhao YP - Sci Rep (2013)

(a) The relationship between the work of adhesion Wa and the Young's modulus Y in the ordinary range of FCC LJ solids.The red line is a linear fit of the MD results. (b) Evolution of Rf with respect to t for different Y.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3672886&req=5

f4: (a) The relationship between the work of adhesion Wa and the Young's modulus Y in the ordinary range of FCC LJ solids.The red line is a linear fit of the MD results. (b) Evolution of Rf with respect to t for different Y.
Mentions: In the framework of MKT, the energy dissipation results from the friction at the MCL, measured by Wa, which has a link with the Young's modulus Y. A variety of solids can be modeled as LJ solid37, such as the face-centered-cubic (FCC) solid38 used in our simulations, in which only the nonbonding interactions are considered. From the atomic aspect of view39, Wa is expressed by , where AS−L is the Hamaker constant between solid and liquid, ρS and ρL are the number density of the solid and the liquid, dL is the size of the liquid molecule, is the depth of the LJ potential well, is the zero-crossing distance. Y of the LJ solid is 39, where ds is the lattice constant of the solid. Substituting parameters used in our simulations, we obtain Wa ~ 0.1 J/m2 and Y ~ 100 GPa. Comparing their expressions, Wa monotonically increases with the increase of Y. However, there is no analytical solution of the relation between Wa and Y. Hence, we used the MD simulations to obtain their relation by changing εS−S and found a roughly linear increase of Wa with respect to Y, i.e. Wa ~ λY, shown in Fig. 4(a).

Bottom Line: For the first time, the combined effect of the surface topology, the intrinsic wettability and the elasticity of a solid on the wetting process is taken into consideration.Scaling analysis is performed based on molecular kinetic theory and validated by our simulations.Our results may expand our knowledge of wetting on pillars and assisting the future design of active control of wetting in practical applications.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing, People's Republic of China.

ABSTRACT
Dynamic wetting on the flexible hydrophilic pillar-arrays is studied using large scale molecular dynamics simulations. For the first time, the combined effect of the surface topology, the intrinsic wettability and the elasticity of a solid on the wetting process is taken into consideration. The direction-dependent dynamics of both liquid and pillars, especially at the moving contact line (MCL), is revealed at atomic level. The flexible pillars accelerate the liquid when the liquid approaches, and pin the liquid when the liquid passes. The liquid deforms the pillars, resulting energy dissipation at the MCL. Scaling analysis is performed based on molecular kinetic theory and validated by our simulations. Our results may expand our knowledge of wetting on pillars and assisting the future design of active control of wetting in practical applications.

Show MeSH
Related in: MedlinePlus