Flexible thermoelectric materials and devices for sensing applications

Given the explosive advancements in artificial intelligence and the Internet of Things, flexible, portable, sustainable and maintenance-free sensors are increasingly demanded. Aligning with that, the development of efficient energy harvesting devices to power these sensors is crucial and has aroused extensive attention recently. Flexible thermoelectric devices have emerged as promising candidates because they are capable of directly converting temperature differentials into voltage while offering the advantages of flexibility, absence of vibration, long service lives, and seamless integration with various multi-functional miniaturized electronics. Additionally, flexible thermoelectric (FTE) devices can perform as self-powered sensors, displaying great application prospects. In this review, the fundamental knowledge on FTE materials and devices is summarized, highlighting recent progresses in the state-of-the-art FTE materials and devices. The representative sensing application scenarios, including temperature sensors, pressure sensors, strain sensors, airflow sensors, respiration sensors, dual-modal sensors, multi-modal sensors, and electronic skin, are systematically outlined. Finally, the current development bottlenecks, challenges and prospects towards the future development of FTE materials and devices for sensing applications are discussed with a view to drive further advances in the field of self-powered and flexible sensors.