Laser-assisted additive manufacturing for metallic biomedical scaffolds

Tissue engineering scaffolds serve as the defining structure for regenerating human tissues as well as the providers of temporary functionality during tissue regeneration. Scaffolds can be used as long-duration residing implants in applications such as dental, craniofacial, knee, and hip defects. When used as implants, the complex shape of scaffolds requires appropriate matching with the shape of the defect at the location of the implant, as well as biological compatibility with the surrounding tissue. In addition, the mechanical properties of scaffolds, which mainly include Young’s modulus, fatigue strength, and wear characteristics, need to be properly balanced with the properties of surrounding hard tissues for trouble-free and long-term functioning of the implant. The metallic structures produced by computer-aided design (CAD) controlled additive manufacturing (AM) technologies provide immense potential for developing such scaffolds and implants with very short lead times and at affordable costs using a variety of available metal powders. Out of many AM technologies, laser-assisted metal powder fusion and deposition systems have been gaining consistent popularity and enjoying sustained development for the past two decades. This chapter investigates the potential, progress, and the remaining research gaps and challenges for laser-based AM systems employed in developing metallic scaffolds and implants. The chapter also contains a discussion on the nature, scope, and desirable characteristics of scaffolds and implants so that the viability of metallic scaffolds can be elucidated. A thorough description of the achievements and limitations of four mainstream laser-based additive manufacturing (LBAM) systems, namely selective laser sintering (SLS), selective laser melting (SLM), laser engineered net shaping (LENS), and direct metal deposition (DMD), is presented, with particular focus on developing biomedical scaffolds and implants from biocompatible metals. The discussion on SLS may be an exception because most of the scaffolds made by this process are nonmetallic, but we cannot eliminate SLS from our discourse because it is the very foundation upon which SLM has been developed. Finally, the chapter discusses certain observations noted by the authors during their own research on the laserassisted development of scaffolds and implants, including remaining research gaps and potential areas for further research