Laser surface texturing of biomaterials: from conceptualization to implementation

Laser surface modification and more specifically laser surface functionalization is widely being considered as a way to efficiently give the surfaces of innovative high value products added or enhanced surface properties. The technology offers a number of desired advantages over competing technologies, of which: selectivity, relatively high processing speeds and the absence of waste or harmful by-products. Nevertheless, the full range of potential applications and suitable target materials is not yet explored, and some feasibility and implementation challenges remain open-ended concerns. With the limited literature available on laser surface texturing of cobalt chrome alloys, a prevalent implant material, the research presented in this thesis aims to address the suitability of this technology in that context and compare it with the current state-of-the-art in the orthopaedics industry. Furthermore, the transferability of the laser surface texturing process from 2D planar test samples to actual 3D parts will be assessed and the effects of 3D laser processing disturbances on the surface functionality evaluated. Finally, a method for laser processing complex surfaces productively is presented and validated on additively manufactured spherical parts

Functionalization of plastic parts by replication of variable pitch laser-induced periodic surface structures

Surface functionalization of plastic parts has been studied and developed for several applications. However, demand for the development of reliable and profitable manufacturing strategies is still high. Here we develop and characterize a new process chain for the versatile and cost-effective production of sub-micron textured plastic parts using laser ablation. The study includes the generation of different sub-micron structures on the surface of a mold using femtosecond laser ablation and vario-thermal micro-injection molding. The manufactured parts and their surfaces are characterized in consideration of polymer replication and wetting behavior. The results of the static contact angle measurements show that replicated Laser-Induced Periodic Surface Structures (LIPSSs) always increase the hydrophobicity of plastic parts. A maximum contact angle increase of 20% was found by optimizing the manufacturing thermal boundary conditions. The wetting behavior is linked to the transition from a Wenzel to Cassie-Baxter state, and is crucial in optimizing the injection molding cycle time

Light scattering and optical diffusion from willemite spherulites

This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.optmat.2015.12.025Willemite is a zinc silicate mineral used in modern day pottery as a decorative feature within glazes. It is produced by controlled heat treatment of zinc oxide-containing ceramic glazes. The heat-treated glazes devitrify, producing thin nanoscale needle-like willemite crystals growing in spherulitic morphologies through branching of the needles. We show here that this resulting morphology of willemite crystals in an inorganic glass matrix has a previously unreported strong interaction with light, displaying remarkable optical diffraction patterns. Thin sections of such spherulites act as optical diffusers, enabling light beams to be spread up to 160? in width. Analysis of the interaction between the willemite spherulites and light suggests that the high density of willemite crystals in the spherulites and the length scales associated with both the thickness of the needles and the spacings between branches are together responsible for this optical diffusion behaviour