Mult Stimuli Responsive Smart PEEK Shape Memory Composites for Biomedical Applications: Current Advances, Challenges, and Future Perspectives

Shape-memory polymers (SMPs) have emerged as an important class of smart materials capable of undergoing programmable shape recovery in response to external stimuli, offering significant opportunities for next-generation biomedical devices. Among these materials, poly(ether ether ketone) (PEEK) has attracted considerable attention because of its excellent mechanical strength, chemical stability, thermal resistance, and biocompatibility, making it particularly suitable for load-bearing orthopedic and implantable applications. Recent advances in material engineering have enabled the development of smart PEEK composites with multi-stimuli responsiveness, including thermal, photonic, magnetic, mechanical, and solvent-induced activation. More importantly, the incorporation of chromogenic functionalities including thermochromic pigments, photochromic molecules, mechanochromic systems, and colorimetric sensors has transformed conventional shape-memory materials into intelligent, self-reporting biomaterials capable of providing real-time visual feedback during implant deployment, functional recovery, and postoperative monitoring. This review provides a comprehensive overview of recent advances in smart PEEK-based shape-memory composites, with particular emphasis on the integration of color-responsive materials for biomedical applications. Material modification strategies, fabrication technologies, and mechanisms governing multi-stimuli responsiveness are critically discussed together with the incorporation of chromogenic additives that enable visual sensing of temperature, mechanical stress, pH changes, and implant-associated pathological conditions. Recent developments in additive manufacturing, 3D and 4D printing, nanotechnology, and multifunctional composite design are also highlighted as enabling technologies for next-generation intelligent implants. Finally, the review discusses current limitations, including challenges related to long-term stability, color durability, biocompatibility, manufacturing scalability, and clinical translation. Future perspectives focusing on self-reporting orthopedic implants, colorimetric infection monitoring, personalized medical devices, and intelligent biomaterial platforms are presented to provide a roadmap for the continued development of multifunctional color-responsive PEEK systems.