Introduction Additive manufacturing has already transformed the way mechanical components are designed and produced. 4D printing takes this concept a step further by creating components that can change their shape, properties, or function over time when exposed to an external stimulus. The fourth dimension in 4D printing is time. Unlike conventional 3D-printed parts, 4D-printed components are designed to respond intelligently to changes in their environment. This emerging technology has significant potential in Mechanical Engineering, robotics, aerospace, automobiles, biomedical devices, and smart manufacturing. What is 4D Printing? 4D printing is an advanced additive manufacturing technique in which smart materials are printed into structures capable of transforming after fabrication. These materials respond to stimuli such as: • Temperature • Moisture • Light • Electricity • Magnetic fields • pH changes • Mechanical force The component is programmed during the design and manufacturin...