4D printing: materials, technologies, and future applications in the biomedical field

4D printing can be defined as the fabrication of structures using smart materials that allow the final object to change its shape, properties, or function in response to an external stimulus such as light, heat, or moisture. The available technologies, materials, and applications have evolved significantly since their first development in 2013, with prospective applications within the aerospace, manufacturing, and soft robotic industries. This review focuses on the printing technologies and smart materials currently available for fabricating these structures. The applications of 4D printing within biomedicine are explored with a focus on tissue engineering, drug delivery, and artificial organs. Finally, some ideas for potential uses are proposed. 4D printing is making its mark with seemingly unlimited potential applications, however, its use in mainstream medical treatments relies on further developments and extensive research investments.