Session: Basic Research in Colloids, Surfactants and Interfaces:

Lubricating fluid coated slippery surfaces are inspired by Nepenthes pitcher plants and show rich fundamental aspects with promising potential applications. The thin lubricating film of a slippery surface, which is sandwiched between an aqueous drop and the solid surface, is found stable or unstable depending on the surface energy of the solid surface. In this study, our research is focussed on the stability of lubricating films of slippery surfaces, which depends on the interfacial energy and the intermolecular interaction between the interacting media. Various interfacial energies control the stability (spreading) of micrometer thick films whereas the intermolecular interaction governs the stability of nanometer-thick films. For an unstable lubricating film underneath an aqueous drop, the instability pattern and its dynamics depend on the thickness of the film. A fluorescence microscopy-based technique is used in this study to investigate the final dewetting morphologies of thin lubricating films underneath aqueous drops for different thicknesses. Subsequently, optical contact angle measurements are also used to demonstrate the sink dynamics of the aqueous drop due to the dewetting of the lubricating films underneath the drops. The sink dynamics can be divided into different regimes such as initial thinning of a lubricating film due to the Laplace pressure of the drop, dewetting of the film, and finally the spreading of the drop. In equilibrium, the aqueous drop sits on a dewetted lubricant film on the solid surface. It is also observed from the dewetting dynamics that the system shows different slip behaviour (from no slip to full slip) depending on the thickness of the dewetting lubricating film.

Mr. Shivam Gupta

Appearances