Electrically Heated Flexible Heaters in Wearable Technology: A Review of Research Progress and Challenges

The growing need for thermal regulation in extreme environments and personalized heat management underscores the limitations of conventional rigid heaters, whose bulky structure, limited flexibility, and sluggish thermal response impede their integration into wearable electronics, biomedical devices, and smart textiles. In contrast, electrically heated flexible heaters─lightweight, mechanically compliant, and capable of rapid, precise heating─offer a compelling solution, enhancing both device performance and user comfort. This review summarizes the recent progress and existing challenges of electrically heated flexible heaters in wearable applications with a focus on their heating mechanisms, materials, fabrication techniques, and practical implementations in wearable systems. First, it briefly introduces the heating mechanism. Second, it highlights and evaluates different conductive heating materials, including metal-based materials, carbon-based materials, conductive polymers, MXene, and composite materials. At the same time, a comparison is made of the various preparation processes for electrically heated flexible heaters. Subsequently, the applications of flexible electrothermal heaters are systematically reviewed in areas such as personal thermal management, healthcare, visual indicators, thermal camouflage, information encryption, and electromagnetic shielding. Finally, the challenges and issues faced by electrically heated flexible heaters in the wearable field are explored, and potential solutions are proposed.