Complex fluids behavior at the interface:Beyond the trivialities

Talk by Dr. Udita Uday Ghosh (IIT-BHU, Varanasi) on the topic 'Complex fluids behavior at the interface:Beyond the trivialities' during the 36th mid-year meeting of the IASc, 04 July 2025.

Published abstract of the talk given below.

Complex fluids ranging from polymeric solutions, colloidal suspensions
to bacterial suspensions are ubiquitous but their behavior at the solid-fluid
interface are often distinctive. These distinctions will be highlighted in this
talk through multiple interfacial phenomena. The journey will start with the
dramatic climbing of certain viscoelastic fluids like polymeric solutions onto
an immersed rotating rod. This classical effect, called the Weissenberg effect
has been actively utilized in electrospinning, transporting of high viscosity
solution at picolitre level and in fabrication of micro/nano structures. This
phenomena will be revisited with a simple question‒does replacing the
immersed rod with an oil-dipped rod alter the features of the rod-climbing
effect? While the effect of shear on complex fluids is explored in the first
part of this talk, the second part focuses on flow dynamics of polymeric
fluid through cellulosic media in capillary rise experiments. Thereafter, we
proceed to probe the response of another class of complex fluids, colloidal
suspensions in discrete form, i.e., as droplets subjected to evaporation. In
particular, we attempt to characterise the evaporation via liquid cap evolution
dynamics instead of the classical approach of evaporation modes.