A comprehensive review on development of thermal metamaterials

Effective heat management remains a pivotal challenge in contemporary engineering, with most existing approaches centered on passive regulation rather than active control. As technological systems become increasingly compact and powerful, the demand for precise thermal manipulation—particularly the directional guidance of heat flow—has intensified. This review focuses on the rapidly advancing field of thermal metamaterials (TMMs), an innovative class of engineered materials specifically designed for anisotropic and adaptive control of heat conduction. The paper begins by categorizing metamaterials and exploring the fundamental thermal behaviours that distinguish TMMs from conventional materials. It then delves into state-of-the-art design methodologies, including transformation thermotics, topology optimization, and the emerging role of machine learning in accelerating the design process. Various fabrication techniques—ranging from conventional machining to additive manufacturing—are critically assessed, with an emphasis on scalability, material compatibility, and precision. The review also discusses experimental validation and testing protocols that bridge the gap between theoretical models and real-world implementation. By integrating design, fabrication, and testing strategies into a cohesive framework, this work aims to provide a comprehensive foundation for the development of next-generation heat management technologies with improved performance, adaptability, and manufacturability.