Development of Superhydrophobic PTFE Surface Using Oxygen Plasma Processing

The effect of oxygen plasma processing on the wettability of the polytetrafluorethylene (PTFE) surfaces has been studied. In this study, the radio frequency (RF) power (50–300 W), exposing time (5–30 min), and working pressure of
$5\times 10^{-\textrm {2}}$
mbar were used to create nanostructures on PTFE surfaces. To prevent contaminants and the impact of substrate temperature, a single electrode-based setup was employed for plasma discharge with a sacrifice PTFE disk behind the specimen. The transformation of the hydrophobic to the superhydrophobic surface was achieved by etching with oxygen plasma at different RF power and treatment times. After treatment of 5 min at 200 W, measured water contact angle (WCA) was about 135° which became superhydrophobic (152°) when the treatment time was increased to 30 min. The surface topography and morphology of the surface were studied by using atomic force microscopy (AFM). The surface roughness is responsible for changes in the wettability of the PTFE surfaces. An increase in RF power and processing time increased the surface roughness through nanopillar formation which in turn increased the WCA of the surface. X-ray photoelectron spectroscopy (XPS), Fourier transformation infrared spectroscopy (FTIR), and attenuated total reflectance were used to examine the chemical alteration of the PTFE surface following oxygen plasma treatment. The group frequencies observed in the FTIR and XPS spectra of the treated samples did not show any notable alterations compared to the untreated samples. However, slight variations were noticed in the intensity values of the absorbance peaks across all the samples. Results are associated with the oxygen plasma-modified PTFE samples’ wettability properties, which are investigated using contact angle, hysteresis, and surface energy measurements.