Tuning Drop Motion by Chemical Chessboard-Patterned Surfaces: A Many- Body Dissipative Particle Dynamics Study

CS Lin and S Chen and LL Xiao and Y Liu, LANGMUIR, 34, 2708-2715 (2018).

DOI: 10.1021/acs.langmuir.7b04162

Controlling the motion of liquid drops on the solid surface has broad technological implications. In this study, the many-body dissipative particle dynamics (MDPD) was employed to study the drop behaviors on chemical chessboard-patterned surfaces formed by square or triangular tiles. The scaling relationship of the model was established based on the surface tension, viscosity, and density of a real fluid, and an improved contact angle measurement technique was introduced to the MDPD system. For drops on a horizontal plane with different tile sizes, the equilibrium morphology was examined. The critical Bond number, that is, the critical dimensionless force which is required to unpin the drop, was found strongly affected by the size and the shape of the tiles. Once the droplet begins to move, the tile pattern and the size strongly affect the velocity fluctuation while weakly affect the average velocity. Interestingly, besides the common straight forward path, two more route patterns (zigzag and oblique) were observed by only tuning the tile angle, indicating that the advancing routes of the drop may vary according to the tile angle. To the author's knowledge, this phenomenon has not been reported in the literature. This study provides a valuable tool to explore the possibility of passive control of the drop's motion by energy-free chemical heterogeneous surfaces and thus is helpful for engineers to design a surface that could manipulate the drop motion without external energy.

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