Fabrication of superhydrophobic/superhydrophilic patterns on polyimide surface by ultraviolet laser direct texturing

This paper presented a single-step processing method to fabricate either superhydrophobic or superhydrophilic patterns on different regions of polyimide surface by ultraviolet laser direct texturing. The effects of laser power intensity and pulse overlap on surface wettability were studied. When the laser power intensities applied were low ( < 5.5 x 10(5) W/cm(2)), the wettability of polyimide surface would transform from pristine hydrophilicity to superhydrophobicity with an increase of the pulse overlap. However, when the laser power intensities applied were high ( > 5.5 x 10(5) W/cm(2)), superhydrophilic surfaces could be obtained with increasing the pulse overlap. Thus, either superhydrophobic or superhydrophilic patterns would be fabricated by adjusting the laser power intensity and pulse overlap. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, and water contact angle meter were employed to characterize the physical and chemical properties of the laser-textured surface, respectively. The results showed that surface roughness and chemical compositions were varied by changing these two laser parameters, and both the surface roughness and the surface chemistry contributed to the change of wetting behavior of polyimide patterns. The convenient and efficient method to create the patterns with superhydrophobicity and/or superhydrophilicity would have the potential applications in flexible electronics, microfluidics, bio-technical field, and so on.