Processing of Functional Texturing on Micro-fibers by Laser-induced Micro/Nanoscale Surface Topographies

The purpose of this study was to establish a method for fabricating a laser-induced micro/nanoscale surface topography (micro/nanotopography) on micro-fibers of glass (quartz) with a diameter of 125 m by using a femtosecond-pulsed laser to express the function of hydrophilicity. The micro/nanotopographies were produced through laser ablation by using a femtosecond-pulsed laser with a wavelength of 514 nm, a pulse width of 234 fs, a repetition rate of 60 kHz, and a spot diameter of 6.9 m. Structures of the irradiated surfaces were observed experimentally using a scanning electron microscope. A micro/nanotopography was observed on the surface of the micro-fiber when fluence and/or overlap ratio exceeded a given threshold. These experimental data showed evidence of a micro/nanotopography on laser-ablated micro-fibers. The apparent contact angles ranged from 106.4 to 88.7 without the micro/nanotopography, and decreased from 88.2 to 48.7 when a micro/nanotopography was presented. In particular, several cases of hydrophilicity under 51.1 were obtained, likely because of the non-continuous change in wettability from the Cassie state to the Wenzel state. Thus, optimum conditions for including both a micro/nanotopography and a hydrophilic surface on a micro-fiber were identified.