Effect of roughness as determined by atomic force microscopy on the wetting properties of PTFE thin films

TLDR

The study investigates how the roughness of vacuum‑deposited PTFE thin films affects their wetting behavior using AFM and contact angle measurements. Surface roughness was quantified by AFM through RMS roughness (Rq) values and fractal dimension analysis. Results show a clear correlation between roughness and contact angle, with nanometer‑scale asperities producing extremely high water contact angles up to 150°, confirming that roughness drives the hydrophobicity of the PTFE coating.

Abstract

Abstract The influence of film roughness on the wetting properties of vacuum‐deposited polytetrafluorethylene (PTFE) thin films has been investigated using atomic force microscopy (AFM) and contact angle goniometry. Surface roughness has been characterized by atomic force microscopy in terms of RMS roughness ( R q ) and fractal dimensions. A contact angle correlation with surface roughness, as determined by AFM, is evident from these results, which are discussed on the basis of wetting theory. The results also confirm that the high water contact angles (as high as 150°) recently observed at the surface of a new water repulsive coating material (mixture of PTFE and binder) are because of surface roughness. Such measurements clarify the effect of nanometer‐size surface asperities on the wetting properties of hydrophobic coating.