3D transient modeling of thin-film coated surfaces to predict the temperature and ablated areas during laser processing

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University of New Brunswick
Increasing the biocompatibility of biomaterials is a hot topic in biomedical engineering. Introducing new surface modification methods, that can just slightly enhance the biocompatibility can directly improve the quality of lives of thousands or millions of people all around the globe. The main goal of this thesis is to study laser processed thin film multilayer structures which can be potentially used for biomedical applications. In this thesis, the laser treatment process is numerically modeled to predict the temperature field and surface profile for each set of laser parameters including the average power, repetition rate and scanning speed. The model is successfully verified with experimental measurements. The same model was modified for laser processing of thin film coated metals. The results show that applying a thin film on the surface can completely change the temperature field and make the heat affected zone smaller or larger. A new surface modification method is introduced by combining laser processing and electrospinning technique. In this method, the surface is processed by laser beam and then it is coated with an electrospun thin layer. This method has potential applications in bone implant fabrication. The implant can benefit from excellent biocompatibility of the electrospun layer in short-term, before the fibers are degraded, as well as long-term biocompatibility of the laser treated surface. In vitro tests showed that, this method can improve the biocompatibility, especially when the laser processed surface is coated with nanoscale fibers. Furthermore, it is shown that, by applying the electrospun layer on the surface, the thermal conductivity of the surface is closer to human body’s conductivity. It makes it an attractive method for modification of dental implants, where the cells can be damaged while drinking a hot beverage. Additionally, antibacterial agents (e.g. silver and ampicillin) were added to the fibers as an antibacterial agent, to prevent implant infection.