Doped and Multilayer Variants of Diamond-Like Carbon Coatings for Biomedical Devices: A Review

Abstract

Diamond-like carbon (DLC) coatings are promising for biomedical applications due to excellent tribology, chemical inertness, and biocompatibility, but suffer from high residual stress and poor adhesion. This review focuses on two advanced strategies—elemental doping and multilayer architectures—to overcome these limitations. Metal doping (Ag, Cu) and nonmetal doping (Si, F) adjust the sp³/sp² ratio, reducing internal stress while improving toughness and adhesion. Silicon enhances hydrophilicity and tribochemical stability; fluorine increases hydrophobicity, reducing protein adsorption and platelet activation; silver or copper imparts antimicrobial properties. Multilayer designs like nanolaminates relieve interfacial stress and boost load-bearing capacity, significantly improving wear resistance and adhesion on polymers. Despite the remarkable progress, the path to clinical maturity requires overcoming persistent challenges. Achieving precise control over dopant distribution and release kinetics is paramount to ensuring long-term therapeutic efficacy without toxicity. Furthermore, ensuring robust interfacial adhesion in complex multilayer architectures under physiological duress remains a critical engineering challenge. A deeper biological understanding is also needed to decipher how coating microstructure and wear debris characteristics orchestrate the immune response and long-term tissue integration. Overall, doped and multilayer DLC coatings hold great potential to enhance the durability of next-generation biomedical devices.