Size Effect on Nano-Droplet Spreading on Solid Surface

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In this paper MD simulation has been performed to study the behavior of nano-sized non-polar argon droplets spreading on a solid surface. Three different sizes of the nano-droplet have been examined with the diameters of 6, 9 and 12 . The dynamic contact angle and maximum spreading diameter rate of the droplets were analyzed according to the size of the droplets and also the nature of the substrates. The properties of surface were changed from wettable to partially wet, and non-wettable surfaces. We have examined the different aspects of droplet spreading to investigate the mechanism of spreading in nano-scale. It is found that the dynamic contact angle has changed significantly by changing the droplet size. While the equilibrium contact angle was less affected by change in the drop size. The maximum spreading diameter rate is increased by increasing the drop diameter for all surfaces. For wettable surface we have observed the spreading rate diameter vary with drop diameter according to a power law, with the power of nearly 1.4. The dynamic contact angle has shown no effect by size in this case. For partially wettable and non-wettable surfaces, the maximum spreading rate scales up with the same power, however the curves have shown a time difference with a delay in the wetting process. The wetting time and the delay in dynamic contact angle in non-wet and partially wettable surfaces have shown a correlation of power 0.67 with the drop size, i.e. the time difference increases by increasing the droplet size. It was observed the non-wettable surfaces bounce back the droplet in a different critical surface property, according to the size of droplet, i.e. the larger drop bounces back on a surface with higher interaction energy.

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Journal: TechConnect Briefs
Volume: 3, Nanotechnology 2008: Microsystems, Photonics, Sensors, Fluidics, Modeling, and Simulation – Technical Proceedings of the 2008 NSTI Nanotechnology Conference and Trade Show, Volume 3
Published: June 1, 2008
Pages: 374 - 377
Industry sectors: Medical & Biotech | Sensors, MEMS, Electronics
Topic: Micro & Bio Fluidics, Lab-on-Chip
ISBN: 978-1-4200-8505-1