Droplet Movement on a Composite Wedge-Shaped Surface with Multi- Gradients and Different Gravitational Field by Molecular Dynamics

B Xu and ZQ Chen, MICROGRAVITY SCIENCE AND TECHNOLOGY, 30, 571-579 (2018).

DOI: 10.1007/s12217-018-9641-6

To find out the mechanism of droplet movement on the composite wedge- shaped surface with multi wettability gradients and simulated gravitational field in a micro view, the model of droplet movement was built and studied by molecular dynamics. It was found that the droplet would move faster and farther with greater vertex angle on hydrophobic surface than on hydrophilic surface until the whole droplet reached the strong wettability surface. Applied force was used to simulate gravitational field. An inflection point was appeared in the average velocity curve. The average velocity increased first and then decreased with greater applied force. The simulation results of relationship between average velocity and applied force corresponded well with nonlinear fitting curve, indicating the reasonable and reliable of simulation results. With the increase of applied force, the droplet became more flat. However, the effect of wettability gradient to shrink the spread area played a major role in the early to make the droplet narrower and then the combined effect of wettability gradient to enlarge the spread area and applied force had a major impact in the later to make the droplet spread more.

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