Regensburg 2022 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 7: Wetting, Fluidics and Liquids at Interfaces and Surfaces

CPP 7.7: Vortrag

Montag, 5. September 2022, 12:30–12:45, H39

Dewetting of thin lubricating films under aqueous drops on high and low surface energy surfaces — •Bidisha Bhatt, Shivam Gupta, Vasudevan Sumathi, Sivasurender Chandran, and Krishnacharya Khare — Indian Institute of Technology Kanpur, Kanpur, India

Understanding the stability of thin liquid films under different environments is important due to their potential applications, such as coatings, paints, and printing, to name a few. In this work, we investigate the stability of thin liquid films of a lubricating fluid under aqueous drops on slippery surfaces. Lubricating films under aqueous drops are found stable when the total excess free energy of the system is positive, which otherwise would dewet into droplets on hydrophilic surfaces. The dewetting dynamics and the apparent contact angle of the aqueous drop depend on the thickness of the lubricating film and the final morphology depends on interfacial boundary conditions between film and the substrate. However, the lubricating films on hydrophobic surfaces are stable under the aqueous drops, yet they can be destabilized using external perturbations like an electric field. Due to the electric field, surface capillary waves are generated at the film-drop interface, and the amplitude of the waves grows exponentially with time, similar to spinodal dewetting. Experimentally observed wavelength and growth rate of the surface capillary waves show good agreement with the theoretically predicted value using linear stability analysis. The dewetted droplets coalesce and form a uniform film again upon removing the applied voltage, making the dewetting process fully reversible.