Processing of Functional Texturing on Micro-fibers by Laser Induced Periodic Surface StructuresWednesday (24.06.2020) 11:20 - 11:23 Room 1
Objectives: Functional textures on fiber surfaces are useful in various textile applications, including wettability, moisture retention, breathability, dyeability, cushioning, and touch sensation. However, it is difficult to process micro- and nano-textures on fibers with micron-scale diameters because of the risk of rupture. The purpose of this study was to establish a method for fabricating a laser induced periodic surface structure (LIPSS) on micro-fibers induced by a femtosecond laser to express the function of wettability.
Methods: The micro- and nano-patterned surfaces were produced through laser ablation using a femtosecond laser (Carbide, Light Conversion UAB, Lithuania) with a wavelength of 1028 nm, a pulse length of 234 fs at a repetition rates of 60 kHz, and a spot diameter of 7 microns. Various geometries and structures of the irradiated surfaces were compared with experimental observations of glass fibers (quartz, 125 microns of cladding diameter, 20 degrees of equilibrium contact angle, Furukawa Electric Co., Ltd., Japan) using a scanning electron microscope. An overview is given of how the microscopic properties of the generated surfaces depend on the laser parameters of the fluence, F, ranging from 2.34 to 18.36 J/cm^2 and the overlap ratio of laser spots, OR. The apparent contact angles of the glass fibers were measured using a commercial contact angle analyzer (DM-701, Kyowa Interface Science Co. Ltd., Japan) by dropping a 1 micro-L of distilled water droplet from a microsyringe between two glass fibers.
Results and Discussion: A LIPSS was observed on the glass surface when F and/or OR exceeded a threshold level. The glass fiber ruptured for F > 18 J/cm^2. Before laser processing, the apparent contact angle of the glass fiber was 107.0 degrees, which agreed well with the calculation results of the Cassie–Baxter equation with a cylindrical model. After laser processing, the apparent contact angles ranged from 89.0 to 106.4 degrees, and they decreased from 80.7 to 48.7 degrees when a LIPSS was observed. In particular, hydrophilicity under 51.1 degrees was achieved, the considered reason being the non-continuous change in wettability from the Cassie state to the Wenzel state.
Conclusion: Regarding fiber hydrophilicity, the experimental data show evidence of a LIPSS on laser-ablated glass fibers. Thus, the optimum conditions for inducing a LIPSS and a hydrophilic surface on a glass fiber are identified.
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