Laser-Induced Melting and Phase Explosion in Liquid Metal Films

We develop a mathematical model of liquid flow and phase change phenomena during fabrication of micro- and nanochannels by laser-induced melting and evaporation of thin metal films deposited on glass substrates. Channels of cross-sectional sizes between several hundred nanometers and a few micrometers can be manufactured by wet etching or contact photolithography after the desired pattern is created by the laser in the metal film. Interaction of the laser beam with the metal film is a complicated process, characterized by high temperature gradients. In this work we investigate the regime where phase explosion takes place in a small region of the metal film surrounded by a pool of molten metal. In the melt region, both evaporation from the surface and viscous flow induced by thermocapillary stresses take place; all these processes are incorporated into the model. Evolution of the surface of the molten film is investigated, and the impact of phase explosion on the flow is discussed.