(539c) The Spreading and Shape Evolution of Ultra-low Surface Tension Droplets

The spreading and shape evolution of droplets, both sessile and pendant, is a classic problem in interfacial fluid mechanics and capillarity. The majority of work has concerned droplets residing within immiscible environments where surface tension normally plays an important role. This paper presents data on two systems where surface tension is largely absent: droplets immersed within a miscible liquid surrounding and water-water, phase separated systems. Not surprisingly, gravitational forces now dominate spreading and shape evolution. It is demonstrated that a number of surprising and unanticipated processes ensue that produce distinctly different drop dynamics.