| Abstract [eng] |
In this Master thesis, the wetting properties of simple (single layer) and hierarchical (double layer) periodic microstructures were investigated. The simplest and most direct measure of surface wettability is the contact angle of a hemispherical liquid droplet (often a water droplet) on the surface of interest, which was measured using a drop shape analyzer and special software. Bigger contact angle of a drop on a surface means that that surface is more hydrophobic. It was established that the polymer SZ2080 used in the experiments has chemical hydrophobic properties. Single layer periodic polymeric microstructures with various periods (8 µm, 6 µm, 4 µm and 2 µm) and one hierarchical (2 µm on 8 µm) microstructure were fabricated using four-beam interference lithography. It was established that when fabricating periodic microstructures using laser interference lithography there is an optimal irradiation dose (~0,004 Js/cm^2), which when used produces microstructures with strongest hydrophobic properties (i. e. achieves maximum wetting angle). It was also established that, in the case of single layer periodic microstructures, increasing the ratio of structure height and period h/Λ (from ~0,41 to ~0,54) increases the water droplet wetting angle (i. e. strengthens the surface hydrophobic properties). Also, the fabricated hierarchical structure significantly increased the hydrophobic properties of the surface: ~90˚ degree wetting angle on 8 µm periodic structure increased up to ~112˚on hierarchical 2 µm on 8 µm structure. Finally, very large wetting angles (i. e. superhydrophobicity) were not achieved, because this requires extremely rough surfaces and for the water droplet to be in the composite (Cassie-Baxter) wetting regime. |
