Focused laser spike (FLaSk) dewetting has been used as a method for the patterning of soft matter thin films for several decades. Through the use of a focused laser beam, a localized heat source is provided along with an extreme thermal gradient. The material melted by the local heating is simultaneously moved down the thermal gradient and forms highly characteristic trench-ridge morphologies. A heating substrate that could prevent direct interaction between the laser beam and soft matter is designed to create a thermal field not influenced by the thin film. The focal point’s peak temperature at different laser power is analyzed by FEM simulation and calibrated by melting of crystalline materials. Through micron-scale dot exposures on this “universal heating substrate”, coupled with optical microscopy, we have studied the characteristic radii of the dewetted ring feature for various glassy thin films with different molecular weights and glass transition temperatures as a function of time. This was approached through a combination of experiments, simulations, and analytical models. Experimental results show that at early stages of the dewetting, the features evolve exponentially with time. However, in the later stage, the evolution is better described by a power law, which arises from the confinement of material far from the thermal spot. Moreover, the evolution rate of soft matters with different molecular weight display behaviors influenced by surface effects. In this way, it has been shown that FLaSk dewetting as a metrology method can be employed for high-throughput analysis of glassy thin film materials in high shear, high temperature testing regimes that would otherwise be difficult to reach.

Focused laser spike thermocapillary dewetting for metrology of glassy thin films

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.