Unlocking toughness in 3D-printed cement through bio-inspired designs: current status and future perspectives

To address the intrinsic brittleness of conventional cementitious materials, researchers have drawn inspiration from natural biological structures to develop advanced bio-inspired cementitious composites through three-dimensional (3D) printing. This approach exploits additive manufacturing to replicate natural architectures-such as the "brick-and-mortar" structure of nacre-by precisely organizing hard cementitious and soft polymeric phases across multiple scales. As a result, novel composites exhibiting a synergistic combination of high strength and toughness have been achieved. This review systematically summarizes recent progress in this interdisciplinary field, emphasizing four key aspects: the composition and structure of bio-inspired materials; the design principles and fabrication methods for bio-inspired cementitious materials; bio-inspired toughening strategies and their associated mechanical models; and the integration of bio-inspired concepts with 3D printing technology. The interrelationships among these topics, key scientific challenges, and state-of-the-art developments are discussed in depth. Finally, this work highlights the remaining obstacles for engineering applications and provides a forward-looking perspective on future research directions.