Recent progress in the fabrication strategies and toughening mechanism of flexible ceramics and their applications

Ceramic materials are ubiquitous in the overall development of humankind and have been investigated for various applications due to their superior strength and stiffness among other known material classes. However, utilizing traditional ceramics in hostile loading environments remains challenging due to their intrinsic brittleness and limited ductile behavior, significantly preventing their range of applications. The move from conventional to advanced flexible ceramics is accelerating, characterized by enhanced mechanical toughness, which is actively studied to overcome their natural brittleness. Thus, developing flexible ceramic materials with damage-resistant characteristics that are simultaneously tough and strong is crucial for applications in frontier domains. In recent decades, numerous studies have reported that ceramic composites containing toughening materials and architectured ceramics constructed using bioinspired microstructures represent intuitive and logical approaches to strengthen and toughen ceramics. In this work, we systematically review the newly emerged toughening approaches for flexible ceramic materials, beginning with a detailed introduction to composite formulation, emphasizing the interfacial effects of ceramic composite toughening. Subsequently, we illustrate the toughening mechanisms of flexible ceramics, focusing on representative bioinspired microstructural imitationsand the relationship between ceramic microstructures and their mechanical performance. Moreover, we present several flexible ceramic fabrication strategies, such as sintering, freezing-casting, 3D printing, and conformal coating, while discussing in detail the influence of fabrication conditions on ceramic toughness. Finally, we demonstrate the potential applications and future opportunities for flexible ceramics. This review aims to provide readers with a better understanding of the toughening mechanisms for flexible ceramic materials and meaningful guidance for further studies toward broader application prospects.