Hydrophilic patterning of superhydrophobic surfaces by atmospheric-pressure plasma jet

An atmospheric-pressure plasma jet (APPJ) has been developed to fabricate hydrophilic patterns on superhydrophobic surfaces. The surface morphologies, chemical compositions and wettability were investigated using scanning electron microscopy, Fourier-transform infrared spectrophotometry, X-ray photoelectron spectroscopy and water contact angle measurement. The results show that the superhydrophobic areas exposed to the APPJ could be completely converted to superhydrophilic without changing the macro and microsurface morphologies. The transition from superhydrophobicity to superhydrophilicity is because of the decrease of hydrophobic fluorine-containing functional groups and the increase of the hydrophilic oxygen-containing functional groups. Combined with scanning and mask technology, complex and large-area wettability contrast patterns can be easily fabricated on various superhydrophobic substrates by the APPJ treatment. Additionally, the retention of intrinsic microstructures enables the surface to recover superhydrophobicity only by using surface fluorination. This results in a rapid reversible transition between superhydrophilicity and superhydrophobicity.