Molecular Dynamics Simulation of Microdroplet Impingement on Solid Surface

Abstract

Impingement process of a nanoscale liquid droplet on solid wall was studied with a molecular dynamics simulation technique in order to investigate one of the elementary processes in inkjet printing technology. We proposed a new wall model consisting of Lennard-Jones (LJ) particles with fixed position, which shows a virtual friction between the wall and the droplet. A droplet consisting of about 14,000 LJ particles was projected with a given speed onto the model wall, and change of the droplet shape was analyzed. After the collision, the droplet spreads on a “hydrophilic” or strongly interacting wall, but bounces on a “hydrophobic” wall. Next we investigated the impinging dynamics on “pre-patterned” walls, which is a promising technique for electronic circuit fabrication with inkjet printing. When the wall is patterned with hydrophilic and hydrophobic regions, the droplet tends to spread only on the hydrophilic area. The droplet is able to trace much complicated patterns when the impinging speed is sufficiently large. In the case that the speed exceeds a certain threshold, however, the droplet breaks up.