Thin liquid films are used in many potential applications such as coating, printing, painting, and heat protaction. The stability of the films depends on various interfacial and intermolecular forces. In this work, our research is focused on studying the stability of the thin lubricating films under aqueous drops. This system is inspired by <i>Nepenthe’s</i> pitcher plants and is used as self-cleaning, anti-icing, anti-biofouling, and self-healing surfaces. In this system thin lubricating film is sandwiched between a drop and a solid surface. The lubricating film between drop and substrate is stable on hydrophobic surfaces, while for hydrophilic surfaces, the lubricating film ruptures and dewet into small dewetted droplets. The dewetting dynamics depend on the lubricating film's thickness, and the final morphology depends on the boundary conditions. However, hydrophobic surfaces are stable due to interfacial and intermolecular forces, but lubricating films on these surfaces can be destabilized using external perturbations like an electric field. Due to the electric field, the surface capillary waves start growing with exponential growth and follow the linear stability analysis. After removing the electric field, the dewetted pattern rewets and forms a uniform film. This dewetting and rewetting process is completely reversible. Electric field induced instability is reversible without removing the aqueous drop have an advantage over hydrophilic surfaces. Fluorescence microscopy was used to observe the dewetting dynamics on hydrophilic and hydrophobic surfaces.

Instability on thin lubricating films under aqueous drops: on hydrophilic and hydrophobic surfaces

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