Design and Scalable Fabrication of Bioactive Ti/Polymer/Ti Sandwich Composites with Controlled Mechanics for Cranioplasty

The study presents the design and development of bioactive hybrid sandwich materials (SMs) for cranioplasty based on a Ti/polymer/Ti architecture engineered to optimize mechanical compatibility, formability, and biointegration. In this second-generation design, we replace the previously used PMMA core with a tunable P(MMA- ran -BMA) copolymer, enabling improved formability at near-room temperature and better matching of cranial bone mechanics. The polymer exhibits a tunable glass transition temperature, allowing for shaping at near-room temperature and enhancing delamination resistance. The Ti-polymer interfaces show strong adhesion (>10 MPa), achieved through surface-initiated polymerization. The sandwich structure provides lower thermal diffusivity and enhanced damping properties compared to monolithic Ti. Furthermore, the external Ti skins were postfunctionalized with poly sodium 4-styrenesulfonate (PNaSS) to introduce bioactivity, addressing the biological inertness of both Ti and methacrylate polymers. This functionalization improves cytocompatibility and promotes biomineralization. In a rat cranioplasty model, follow-up showed less early weight loss and a greater peak weight increase (35% compared to 24% for Ti), supporting improved early postoperative tolerance, although additional in vivo validation remains necessary.