Focused Laser Spike Dewetting as a Rheology Method for Soft Matter Thin Films

Abstract

<div>Focused laser spike (FLaSk) dewetting employs a localized heat source to create thermocapillary induced trench-ridge morphologies. By using a universal heating substrate to create a material independent thermal profile coupled with optical microscopy, we have studied the dewetted ridge feature for several distinct glassy thin films. The evolution of the ridge's radius over time can be modeled using stretched exponential functions to derive a maximum dewetted radius and a characteristic decay time. The characteristic decay time shows a super-Arrhenius behavior resembling viscosity change during the glass transition process. An effective viscosity is defined by balancing the thermocapillary Marangoni stress using the mean temperature in the melt pool, indicating clear signature of composition. In this way, we have demonstrated that FLaSk dewetting as a rheology</div><div>method can be employed for high-throughput analysis of glassy thin film materials at high temperature and shear.</div>