Irradiation of poly(tetrafluoroethylene) surfaces by CF4 plasma to achieve robust superhydrophobic and enhanced oleophilic properties for biological applications

Poly(tetrafluoroethylene) (PTFE) was irradiated by CF4 plasma produced in the gas discharge ion source facility to produce stable and robust superhydrophobic surfaces and to enhance the materials' oleophilic property for biological applications. The characterizations employed on the samples are contact angle measurements, analysis of the surface morphology (scanning electron microscopy), surface roughness measurements (atomic force microscopy) and analysis of the surface chemistry (Fourier transform infrared spectroscopy). Superhydrophobic behavior with water contact angles as high as 156° was observed. The wettability of all the treated samples was found to be stable in time as evidenced by the statistically insignificant differences in the hysteresis contact angles. The level of enhanced hydrophobicity depended on the plasma energies (i.e. irradiation times, discharge current, and discharge voltage); higher plasma energies produced surfaces with high hydrophobicity. The plasma treatment also enhanced the oleophilic property of the materials' surface as evidenced by the decrease in the PDMS-oil contact angle from 33° to as low as 10°. The superhydrophobicity of the modified PTFE and the enhancement of its oleophilic property were due to (1) the changes in the roughness of the surface, (2) the formation of nanoparticles or nanostructures on the surface, and (3) the changes in the surface chemistry.