4D printing: A detailed review of materials, techniques, and applications

Four-dimensional (4D) printing has gained considerable attention since its conception in 2013. It was made possible by interdisciplinary studies and the rapid expansion of smart materials, three-dimensional (3D) printers, and designs. Unlike static objects produced by 3D printing, the 4D effect enables a 3D-printed structure to change its design or functionality over a period of time in reaction to environmental factors such as temperature, light, or water, rendering 3D printing “alive.” This study reviews the latest significant basics and technological developments in 4D printing, as well as their features. The factors affecting 4D printing are also explored. Moreover, the employed materials are studied with a focus on their properties, mechanisms, and possible implications or uses. In addition, the various 4D printing techniques and their applications are presented. Finally, the challenges and limitations of the 4D printing domain are discussed.