Measuring Thermophysical Properties of Glassy Materials via Focused Laser Spike Dewetting

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. Through micron-scale dot exposures on a universal heating substrate designed in our lab, coupled with optical microscopy, we have studied the characteristic radii of the dewetted ridge 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. Not only were we able to identify features of the dewetting that revealed differences between the polymer system, but the FLaSk process could give independent information on surface and bulk behavior. In this way, it has been shown that FLaSk dewetting as a metrology method can be employed for high-throughput analysis of thin film materials in high shear, high temperature testing regimes that would otherwise be difficult to reach.