Laser micro-structuring of polymer surfaces

Surface texturing is a widely used technique in improving the performance of materials for various applications by modifying surface properties. This research focuses on the effective use of laser texturing techniques to modify the surface chemistry, roughness, and mechanical properties of polyether ether ketone (PEEK), specifically those produced through injection molding and additive manufacturing. The aim is to overcome PEEK’s intrinsic bio-inertness, making it more suitable for biomedical applications such as orthopedic implants.

The research objectives include a comprehensive understanding of various aspects related to the influence of lasers on PEEK surfaces. Firstly, the study aims to comprehend the impact of different lasers and their parameters on the properties of PEEK surfaces. Notably, the fluence threshold of PEEK was found to be dependent on the scan speed when using a 1 μm pulsed Nd: YAG laser. Moreover, the research highlights that lower pitch levels lead to surface melting at a specific fluence, while higher pitch levels result in the formation of grooves with varying dimensions. Additionally, utilizing a 10.61 μm pulsed Nd: YAG laser at 50 W output power effectively modifies the roughness of PEEK surfaces. Secondly, the investigation focused on the influence of texture and roughness on surface wettability and free surface energy. In this regard, the CO2 continuous wave laser was employed, significantly enhancing the total surface free energy and contact angles at different roughness levels. This finding demonstrates the successful modification of PEEK surfaces, thereby enhancing their wettability. Another crucial objective of this research was centered around evaluating the surface integrity and mechanical properties of laser-treated PEEK. It was observed that the application of a 10.6 μm pulsed nanosecond laser at fluences greater than 3.34 J/cm² results in significant softening of PEEK. Additionally, the study reveals that laser surface texturing significantly increases the adhesive bond strength of PEEK, regardless of whether the technique used is DLW or DLIP. The bond strength was found to be influenced by groove dimensions, with adhesive failure being the primary mode of failure. Lastly, this research explored the effect of laser treatment on both 3D-printed and injection-molded PEEK. Through a comparative analysis, it was

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revealed that both types of PEEK surfaces can achieve comparable bond strengths using different textures. The manufacturing process, whether 3D printing or injection molding, does not have a significant impact on the treatment process or the resulting surface properties. Particularly, the study highlights that adhesive bond strength is primarily governed by surface roughness, with wider and deeper grooves leading to superior bond strength.

In conclusion, the research provides a comprehensive understanding of the role of lasers in modifying PEEK surfaces, focusing on surface chemistry, roughness, and mechanical properties. The findings contribute valuable insights into the effective use of laser texturing techniques for enhancing PEEK materials, with potential applications in various industries, including biomedicine and manufacturing.