Liquid- to Solid-Like Failure Mechanism of Thin Polymer Films at Micro- and Nanoscales

A surface forces apparatus and various optical visualization techniques were used to study the transition mechanisms between liquid-like snapping and solid-like failure at nano- and microscales. Transient deformations and flows of polymer necks were studied over a large range of pulling forces, pulling rates, temperatures, and viscosities. A continuous transition is suggested—from simple neck-thinning and snapping, through viscous fingering, to sharp solid-like cracking— between these two limiting modes of failure if one chooses to vary the system properties and experimental conditions in a systematic way. The Saffman−Taylor fingering equation was found to remain valid down to nanoscopic dimensions, and a modified version of it is suggested to be suitable to elastic, solid-like materials.