Advances in 4D printing technology in medicine

4D printing technology represents a revolutionary breakthrough in the field of additive manufacturing. It not only inherits the spatial construction capabilities of 3D printing but also introduces the dimension of time, endowing printed objects with dynamic "life". This technology uses smart responsive materials that allow printed objects to change their shape, properties, or functions in response to specific environmental stimuli, such as temperature, magnetic fields, or light changes, as programmed in advance. This has shown great potential and application prospects in the fields of medical research and clinical applications. In this article, we first explore the smart responsive materials that enable 4D printing and introduce their unique physical and chemical properties and functions. Secondly, we review the innovative applications of these smart materials in the medical fields of tissue engineering, regenerative medicine, and drug delivery. Finally, we discuss the challenges faced by 4D printing technology in practical applications and look forward to the future development direction of the technology and its broader application potential in various fields.