# Anodic Oxidation of 3D Printed Ti6 Al4V Scaffold Surfaces: In Vitro Studies
## 1 Introduction  
Industry 4.0 refers to the onset of the \"fourth industrial revolution\", which started in Germany in the 2010s. It involves the systematic implementation of intelligent technologies to optimize production and management processes [1]. The movement had consequences in other fields, including the medical field, leading to a new revolution known as Medicine 4.0. This revolution aims to enhance patients' quality of life through the use of advanced technologies. These technologies are transforming the patient-doctor relationship and enabling more personalized treatments [2]. One of the standout technologies in the context of Industry 4.0 for medicine is additive manufacturing (AM). This technology allows for the production of customized implants with specific characteristics tailored to each individual's situation. The AM method represented a major advance in implants, allowing for custom fabrications with complex geometries, such as porous structures. This has the potential to enhance the osseointegration process [3]. In this context, the Powder-Bed Fusion Electron-Beam Melting (PBF-EB) technique has shown promise as an alternative for manufacturing scaffolds from metallic materials to correct bone defects. The process of Powder-Bed Fusion Electron-Beam (PBF-EB) takes place in a vacuum chamber, where metal powder is evenly distributed on a build platform. The powder is melted using an electron beam for each layer during the fabrication of the specimen. The bed platform moves vertically (in the z-direction) layer by layer, following the design specifications. This technique is highly precise and design oriented, and tailored to meet individual needs. It is capable of manufacturing highly complex structures in a shorter period of time compared to traditional manufacturing processes [4]. The materials used in this application are in the form of powders, with the Ti\({}_{6}\)Al\({}_{4}\)V alloy being commonly utilized. This choice is based on its favorable mechanical properties, such as high strength and a low Young's modulus [5]. After processing, not all particles are melted in the scaffolds, and chemical treatments have been successfully used to remove unmelted powder particles. However, the surfaces produced are bioinert, and surface treatment techniques can be employed to enhance the biological response. Numerous techniques have been proposed for modifying the surface of implantable devices. These techniques include physical methods such as thermal spraying [6; 7], plasma surface modification [6; 8], ion implantation [6; 9], and physical vapor deposition [6; 10], along with chemical methods such as sol-gel [6; 11] and chemical vapor deposition [6; 12]. Electrochemical methods have also been employed for this purpose, and they have become increasingly popular due to their relative simplicity and low cost compared to other techniques. Moreover, they facilitate the application of coatings onto implants through various methods, eliminating the need for expensive and specialized equipment [13]. According to [PERSON] et al. [14], the surface modification of 3D porous metals is more challenging than that of solid implants because widely used techniques, such as plasma spraying, are technically inapplicable or have limitations. From our perspective, a technique that has the potential to enhance implant osseointegration involves growing a layer of titanium dioxide nanotubes (TiO\({}_{2}\)) on the surface of the implant [13]. This technique can also promote better corrosion resistance. [PERSON] et al. [15] verified an improvement in the corrosion resistance of Ti-6 Al-4V extra-low interstitial (ELI) alloy scaffolds, built using the Direct Metal Laser Sintering (DMLS) additive manufacturing technique, after anodic oxidation. Another advantage of this technique is that by varying parameters such as the voltage and the electrolyte, different types of nanostructured morphologies can be obtained [16; 17].