Rational understanding of viscoelastic drop impact dynamics on porous surfaces considering rheological properties

Abstract

Understanding of viscoelastic drop impact on porous solid surfaces emerges as the essential physics for broad industrial and biological systems. However, there have been few studies concerning the post-drop impact transition considering rheological properties and dynamics. Here, we report the post-impact dynamics of viscoelastic drops on porous mesh surfaces using experimental and theoretical analyses. Five concentrations of highly viscous polymer solutions with shear-thinning and viscoelastic characteristics exhibit different rheological properties (viscosity, storage, loss moduli, etc.). These changes in the rheological features result in four distinguishable impact dynamics on two-dimensional mesh surfaces. Viscoelastic drops that exhibit viscoelastic solid properties (storage modulus > loss modulus) resulted in combined elastic solid-like motions and viscous fluid-like motions depending on the impact velocity and anti-penetration effects (such as capillary pressure and yield stress). Meanwhile, decreases in the viscoelastic fluid properties resulted in monotonous viscosity-dominant behaviors. A pressure-balance equation was proposed to theoretically predict the filament column penetration length of viscoelastic solid drops. The theoretical results correlated with the experimentally measured values until necking occurred in the filament column. We believe that this study on viscoelastic drop impact dynamics can shed light on future applications that involve various mechanical behaviors of non-Newtonian fluid drops, such as 3D printing, coating, bio-fluid treatments, and polymeric solutions.