From 3D to 6D bioprinting: emerging additive manufacturing technologies for biomedical applications

Additive manufacturing (AM) has rapidly evolved over recent years, offering a multitude of possibilities for the development of highly realistic medical equipment and devices. Each generation of AM technology introduces new features, enhancing its application in the medical field. Three-dimensional (3D) printing, the foundational technology, offers a cost-effective, rapid, and personalized approach for fabricating medical devices. However, its limited ability to produce highly complex geometries restricts its use in certain advanced applications. To overcome these limitations, 4D printing technology has emerged, enabling the production of dynamic structures that can respond to environmental stimuli. This makes it ideal for fabricating scaffolds and implants that closely mimic the behavior of natural tissues, offering significant potential in regenerative medicine. Additionally, 5D printing surpasses traditional 3D printing by employing five axes in the manufacturing process, enabling the production of complex, robust structures with enhanced mechanical strength. The latest innovation, 6D printing, integrates the dynamic capabilities of 4D printing with the multi-axis precision of 5D printing, further enhancing the complexity and functionality of fabricated medical devices. This review explores recent advancements in AM technologies, including 3D, 4D, 5D, and 6D printing. It discusses their transformative potential in medical applications, from tissue engineering to the production of customized implants and prosthetics.