Nanoparticle‐Empowered 4D Printing: Materials, Stimuli, and Emerging Actuation Strategies

ABSTRACT 4D printing has emerged as a transformative advancement in additive manufacturing, enabling printed structures to undergo dynamic changes in shape or properties over time in response to external stimuli. Although early developments in 4D printing focused on stimuli‐responsive polymers and innovative mechanical designs, significant challenges remain, including slow response times, the necessity for bulk stimulus exposure, and limited spatial precision in actuation. Nanoparticle‐mediated 4D printing offers promising solutions to these limitations. By integrating functional nanoparticles into printable matrices, it becomes possible to achieve remote, localized, and highly programmable actuation with improved speed (ranging from 100% to up 500%) and spatial control (at distance of up to ∼ 1 m). This review summarizes recent progress in material systems for 4D printing and the diverse external stimuli that drive shape transformations. In particular, it focuses on nanoparticle‐mediated 4D printing, highlighting how nanotechnology is unlocking new levels of functionality and adaptability, and outlining future directions for this rapidly evolving field.