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Identifier 000425478
Title Femtosecond laser induced biomimetic surfaces with unique wetting and optical properties
Alternative Title Δημιουργία βιομημιτικών επιφανειών με ξεχωριστές διαβροχικές και οπτικές ιδιότητες μέσω λέιζερ υπέρ-στενών παλμών
Author Λαναρά, Χριστίνα
Thesis advisor Ρεμεδιάκης, Ιωάννης
Reviewer Παπάζογλου, Δημήτριος
Στρατάκης, Εμμανουήλ
Abstract Biomimetics offer the possibility of biological systems simulation on artificial surfaces, with desired properties. There are many attempts to fabricate artificially these surfaces. The present thesis comprises three parts. The first one is the fabrication of micropatterned silicon substrates via ultra-short pulsed laser irradiation under different experimental parameters, including laser fluence. The second part is the fabrication of hierarchical micro-nano-patterned substrates. These comprise micropatterned silicon substrates which have been thermally oxidized and nano-decorated with spherical and rod shaped gold nanoparticles of various functionalities and sizes. Gold nanoparticles have been attached via silane chemistry. Both types of substrates have been characterized with respect to their morphological, wetting and optical properties. The third part is the fabrication of micropatterned steel substrates via ultrashort pulsed laser irradiation under different experimental parameters, including irradiation medium. Steel samples fabricated, for constant laser fluence, in air and ammonia gaseous environments. Regarding the micropatterned substrates, the morphological characterization showed that as the laser fluence increased, the roughness of the surface increased as well. Micropatterned substrates comprised microcones of varying height and density. Specifically, the density and the height of the micro-features (i.e. microcones) decreased and increased respectively, with increasing laser fluence. Optical characterization showed that as the surface roughness appears, the absorbance increased, across the range of wavelength (250-2000nm). The layer of silicon oxide on flat silicon substrates lead to reduction of the reflectance, in contrast with the case of micro-structured substrates, where silicon oxide layer increased the reflectivity, in near infrared spectrum. This leads to absorbance reduction in near IR range but very high absorbance efficiency in UV/Vis range (~97%). Regarding the hierarchical micro-nano substrates, SEM analysis confirmed the successful deposition of the gold nanoparticles on the micropattenred silicon substrates. Deposition gave a homogenous distribution of single nanoparticles and some regions of small clusters. All types of the gold nanoparticles (NPs) being tested, which carried diverse functionalities (e.g. oligopeptides, including the CALNN-RGD and organic moieties, including the DMAP) have been successfully attached on the surfaces of the micropatterned silicon substrates. Rod shaped AuNPs do not carry any ligands. Remarkably, the NPs covered the whole 3D surface of the micropatterned substrates giving a distribution that was comparable to that on the flat silicon substrates. Optical characterization showed that gold nanoparticles caused increment of absorbance of the oxidized micro-patterned silicon substrates in near IR range. Finally, steel micro-patterned substrates have been characterized for their morphological and wetting properties. Morphological characterization showed that in presence of reactive gas (ammonia), during the irradiation procedure, steel microcones were smaller and shorter than the air-structured ones. As for the wetting characterization, in the case of air-structured surfaces there was non stable wetting behavior, in contrast with the ammonia-structured steel surfaces which remained hydrophilic for over 100 contact angle measurement days. Also, the ammoniastructured surfaces appeared anti-corrosive behavior.
Language English
Subject Laser
Issue date 2019-11-29
Collection   Faculty/Department--Faculty of Sciences and Engineering--Department of Materials Science and Technology--Post-graduate theses
  Type of Work--Post-graduate theses
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