Local dynamics during spontaneous thinning of thin films on a substrate*

Applications in bio-sensing, energy-efficient materials and photonics have led to an ever-increasing demand for functional patterns on surfaces at micro and nano scales. A promising method for pattern generation is through the spontaneous rupture and dewetting of thin liquid films on a substrate due to intermolecular forces. The liquid film is known to exhibit power-law (deformation-rate-thinning) rheology in many cases, where 0 < n ≤1 is the power-law exponent (n = 1 for a Newtonian fluid). Here, we study the spontaneous thinning and rupture of a thin film of a power-law fluid on a substrate under the influence of van der Waals forces of attraction. We demonstrate that in contrast to thinning of Newtonian films, fluid inertia can become significant during thinning of films of power-law fluids which leads to a breakdown of lubrication theory. The resulting flow transitions are investigated by employing a first of its kind two-dimensional model for film thinning that is able to accurately resolve the highly disparate length scales that are typical in thin film problems.