Infrared-Laser-Induced Thermocapillary Deformation and Destabilization of Thin Liquid Films on Moving Substrates

We study the thermocapillary deformation, induced by infrared laser irradiation, of thin liquid films on moving substrates. We develop numerical models for the temperature distribution and film thickness evolution. Steady-state film thickness profiles are measured for different values of substrate speed and laser power. The experimental results compare well with the simulations. In the case of partially wettable substrates, the thin liquid films tend to become unstable. We find that, for certain ranges of the laser power and substrate speed, the film ruptures in a single location and subsequently dewets without the occurrence of residual droplets. Such clean dewetting is highly desirable in the context of immersion lithography or solution processing of organic electronic devices.