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.

Response of Saos-2 osteoblast-like cells to laser surface texturing, sandblasting and hydroxyapatite coating on CoCrMo alloy surfaces.

Cobalt chrome alloys are commonly used in orthopaedic implants where high stiffness and wear resistance are required. This study proposes Laser Surface Texturing (LST) as a cost-effective mean for producing bioinspired surface textures in order to improve the performance of CoCrMo orthopaedic implants. Cobalt-chrome alloy disks were modified using three different LST strategies: i) micro-scale texturing using a nanosecond laser source; (ii) micro-scale texturing with an ultrashort laser source and (iii) bioinspired sub-micron scale texturing with an ultrashort laser source. The modified disks were characterized and compared to blasted, hydroxyapatite coated and polished surface finishes. Saos-2 osteoblast-like cells were seeded on the different surfaces and their proliferation and morphology was assessed. The laser modification increases the surface energy of the CoCrMo alloy disks when compared to their untreated counterparts. The bioinspired sub-micron textured surfaces exhibited the highest cell metabolic activity on day 7 of the MTT assay.