The effect of surface structure and arrangement on wettability of substrate surface
Graphical abstract
Introduction
Wetting is a common phenomenon in nature, and it has extensive applications, such as self-cleaning [1], anti-icing [2], anti-fogging [3], and lab-on-a-chip [4]. The contact angle is an important criterion to measure the wettability of the surface, when the contact angle of the droplet on the surface is greater than 90°, it is hydrophobic, otherwise, it is hydrophilic, and it is superhydrophobic when the contact angle is greater than 150° and with small hysteresis [5,6]. Moreover, many studies have demonstrated that the wettability of the surface is not only affected by the surface energy but also depended on the surface roughness of the substrate [7,8]. Therefore, the main methods of manufacturing hydrophobic surfaces are adjusting the surface energy and the surface roughness of the substrate.
At present, a lot of researches on the influence of surface structure on superhydrophobic have been done by many researchers. In terms of experimental studies, Bhushan et al. [5] discussed the influence of patterned silicon surfaces with cylindrical bodies of different diameters, heights and pitch distance on wettability, they believed that the hydrophobicity depends on the ratio of column diameter to spacing; Xia et al. [9] studied the wettability of honeycomb structure with different wall thickness and center distance. In terms of theoretical models, Li et al. [10] and He et al. [[11], [12], [13]] used two-dimensional and three-dimensional models of free energy thermal dynamics to analyze the contact angle hysteresis of different structural surfaces respectively, which was in good agreement with the experiment. The results show that the surface structure has a great correlation with wettability.
With the development of computer technology, molecular dynamics simulation is more widely used in the study of surface wetting because of its convenience and accuracy [14,15]. Hung et al. [16] studied the effect of graphene-coated surface on the wettability by molecular dynamics simulation, and realized the manipulation of droplet diffusion by modifying the different structures on graphene-coated surface. Chai et al. [17] found that the silicon dioxide surface which has been modified can be converted from hydrophilicity to hydrophobicity by molecular dynamics simulation. Theodorakis et al. [18] have done a lot of researches in the field of superspreading by molecular dynamics simulation, and the adsorption of surfactant on the surface was found to be the key feature of superspreading mechanism. And many researches mentioned above have studied the influence of surface structure on wettability from atomic defects to microstructure, from surface molecular particle modification to surface coating, the effect of surface structure on wetting was investigated at multiple levels [[19], [20], [21]]. The universality and reliability of molecular dynamics simulation are proved by these researches, and some important references for our study are provided at the same time.
However, the atomic mechanism of the influence of surface structure on the wettability and the structure of water molecular layer above surface are still unclear. In addition, the shapes and arrangements of surface micro structure units in nature are not regular. In the present study, the influences of different surface structures on the wettability were investigated by molecular dynamics simulation. To this end, the honeycomb arrangement structures with different basic units on the surface were established, then, the wetting behavior of these rough substrates compared with each other. The investigations were performed by the calculation and the follow-up analysis of contact states, static contact angles, radial distribution functions and hydrogen bonds of the droplets. And this research is conducive to discuss the influence of surface structure on wetting commonly existing in nature.
Section snippets
Methods
Molecular dynamics simulation is used to study the wetting behavior of droplets on the surface with different pores structure. All simulations are performed using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) software package [22]. Post-processing and visualization of the simulation results are carried out in the Open Visualization Tool (OVITO) [23] and Visual Molecular Dynamics (VMD) [24].
Contact states
The contact state is also an important index to measure the wettability of the substrate surface. Fig. 4(a) is the sectional view of the plane wetting system, and Fig. 4(b–d) are the sectional views of the rough wetting systems. It can be seen that the droplets of the rough wetting systems are in the Cassie state, and the contact angles are larger than that on the plane, indicating that the solid area fraction can change the hydrophobicity of the surface. And it is evident from Fig. 4(a–d) that
Conclusions
In this paper, the influence of honeycomb arrangement with different basic units on the surface wettability is simulated by molecular dynamics. It is found that the increase of solid area fraction can effectively increase the hydrophobicity. And contact states, static contact angles, RDF and hydrogen bonds of the droplets were calculated in this research, the analysis is carried out on the basis of these data.
First of all, in the numerical examples used in this paper, the droplets are all in
CRediT authorship contribution statement
Pengyu Wang: Conceptualization, Data curation, Formal analysis, Methodology, Software, Visualization, Writing - original draft, Writing - review & editing. Liang He: Conceptualization, Methodology, Writing - review & editing. Zhenqing Wang: Writing - review & editing, Supervision, Project administration, Funding acquisition.
Declaration of Competing Interest
The authors report no declarations of interest.
Acknowledgement
This project is support by National Natural Science Foundation of China with Grant NO. 11532013 and 11872157.
References (37)
- et al.
Fabrication of a superhydrophobic polypropylene membrane by deposition of a porous crystalline polypropylene coating
J. Membrane Sci.
(2008) - et al.
3-D thermodynamic analysis on wetting behavior of superhydrophobic surfaces
Colloids Surf. A
(2016) - et al.
A 3-D model for thermodynamic analysis of hierarchical structured superhydrophobic surfaces
Colloids Surf. A
(2017) - et al.
Thermodynamic analysis on wetting properties of a droplet on a solid surface with engineered trapezoidal microarchitecture
Int. J. Heat Mass Transf. - Theory Appl.
(2018) - et al.
Molecular dynamics simulation of wetting on modified amorphous silica surface
Appl. Surf. Sci.
(2009) - et al.
Spreading of aqueous droplets with common and superspreading surfactants. A molecular dynamics study
Colloids Surf. A
(2019) - et al.
Molecular dynamics study on the hydrophobicity of a surface patterned with hierarchical nanotextures
Colloids Surf. A
(2018) Fast parallel algorithms for short-range molecular dynamics
J. Comput. Phys.
(1995)- et al.
VMD - visual molecular dynamics
J. Mol. Graph. Model.
(1996) - et al.
Bioinspired interfacial materials with enhanced drop mobility: from fundamentals to multifunctional applications
Small
(2016)
Low ice adhesion on nano-textured superhydrophobic surfaces under supersaturated conditions
ACS Appl. Mater. Interfaces
Dynamic defrosting on scalable superhydrophobic surfaces
ACS Appl. Mater. Interfaces
Producing a superhydrophobic paper and altering its repellency through ink-jet printing
Lab Chip
Towards optimization of patterned superhydrophobic surfaces
J. R. Soc. Interface
Binary cooperative complementary nanoscale interfacial materials
Pure Appl. Chem.
Hydrophobic and self-cleaning coatings
Polym. Advan. Technol.
Patterned superhydrophobic surface based on Pd-based metallic glass
Appl. Phys. Lett.
Optimal geometrical design for superhydrophobic surfaces: effects of a trapezoid microtexture
Langmuir
Cited by (13)
Molecular dynamics study on wetting behavior of aluminum plates with different surface energies by microstructure difference
2024, Computational Materials ScienceWetting behavior of nanodroplets with low surface tension on pillar-type nanostructured substrates: Molecular dynamics simulations
2024, Journal of Molecular LiquidsEffect of non-standard SnAg surface finishes on properties of solder joints
2023, Applied Surface Science AdvancesNanostructure-dependent nanobubble drag reduction on NiTi self-adaption surface
2023, Journal of Molecular LiquidsDevelopment of an innovative grinding process for producing functional surfaces
2022, Tribology InternationalCitation Excerpt :Fig. 9 The contact condition is the main criterion to estimate the wettability of a surface which can be measured based on the cross-sectional perspective of the gas-liquid-solid equilibrium system [40]. Fig. 10 presents the image of the structured surface with droplets and 2D cross-section view images for measuring static contact angle on the copper surface with different groove area fractions.
Investigation of surface wettability and their influencing mechanisms under vibration field: A molecular dynamics simulation study
2021, Computational Materials ScienceCitation Excerpt :With advances in computer technology, molecular dynamics has been applied to study the effect of external field on surface wettability. Of note, the effectiveness of molecular dynamics has been demonstrated in a number of researches [20–28]. For instance, Li et al. [24] studied the wetting behavior of droplets on a vibrating smooth surface by using molecular dynamics, they established a model to predict the wetting state of droplets, and discussed the coalescence process of two droplets on a vibrating surface.