Dual-responsive wettability nanofiber coating

Poly o-toluidine nanofiber coatings present an intelligent surface that can switch between hydrophilic and superhydrophobic states using UV light or electric stimuli.

Smart surfaces with adjustable wettability are gaining significant interest in both foundational research and industrial applications, where control over surface interactions with liquids is essential. The wettability of solid surfaces depends mainly on their chemical composition and surface topography. By applying external stimuli, it is possible to alter these surface characteristics, enabling dynamic transitions between hydrophilic (water-attracting) and hydrophobic (water-repellent) states.

In this study, researchers synthesized poly o-toluidine nanofibers through a straightforward interfacial polymerization process in an aqueous/organic system. These nanofibers were then used to create superhydrophobic coatings, which were applied via a room-temperature spraying technique. The resulting coatings demonstrated dual-responsive wettability, enabling a reversible switch between superhydrophobic and hydrophilic states. This behavior was driven by ultraviolet (UV) light and electric stimulation.

Through X-ray photoelectron spectroscopy (XPS) analysis, it was found that UV light exposure altered the surface chemical composition, which in turn influenced the wettability. Meanwhile, applying an electric stimulus caused a shift in surface wettability through the redistribution of charges and the alignment of electric dipoles along the liquid–solid interface. These findings indicate that poly o-toluidine coatings can act as “smart” surfaces, responding flexibly to environmental cues, with potential applications in fields requiring adaptive wettability, such as microfluidics, anti-fouling coatings, and sensor technology.

Source: Journal of Coatings Technology and Research, Vol. 21, pp. 1255–1262 (2024).