Perspectives of Flexible Thermoelectric Fibers by Thermal Drawing Techniques

Abstract

Wearable devices are increasingly being used to prevent diseases and to enhance physical health. However, this advancement comes with the challenge of high power consumption. Existing portable power storage or generation solutions often fail to meet the requirements for uninterrupted power supply, compact size, light weight, and low noise. Thermoelectric materials have emerged as a promising solution for portable energy supplies due to their ability to directly convert body heat into electricity. These materials not only provide clean energy for wearable devices but also support solid-state refrigeration, temperature sensing, and monitoring functions. Nevertheless, conventional inorganic materials with high thermoelectric properties face several challenges, such as brittleness, poor postprocessing capabilities, large size, complex preparation procedures, and high cost, limiting their suitability for heat sources with irregular surfaces. Conversely, while organic thermoelectric materials are more flexible, they exhibit weak thermoelectric performance and cannot meet the growing power demands of modern wearable devices. Recently, through thermal drawing technology, high-performance inorganic materials can be fabricated into flexible thermoelectric fibers, combining excellent thermoelectric properties with flexibility. These fibers are capable of harvesting waste heat to generate electricity, assisting in body temperature regulation, and measuring the temperature of irregular heat sources, thereby meeting the requirements of wearable devices. Wearable fabric devices woven from inorganic thermoelectric fibers retain the thermoelectric efficiency of bulk inorganic materials while offering additional benefits such as washability, fatigue resistance, portability, and the potential for large-scale and low-cost production. These advantages enable wearable thermoelectric devices to operate effectively in diverse and challenging environments. However, current commercial equipment is difficult to accurately measure micrometer/nanometer-scale fiber thermoelectric fibers. Herein, we have developed an in situ measurement system for the thermoelectric properties of micro/nanoscale materials, which can perform integrated in situ testing of the electrical conductivity, Seebeck coefficient, and thermal conductivity of thermoelectric fibers, reducing the measurement uncertainty compared to measuring multiple parameters for multiple samples separately.

This Account primarily summarizes our efforts to enhance the performance of flexible thermoelectric fibers produced by the thermal drawing technique and demonstrates the practical applications of these materials. By preparing fibrous inorganic materials with varying elemental compositions and microstructures and developing an in situ measurement system for characterizing thermoelectric properties of micro/nanoscale fiber materials, we have investigated and analyzed fibers with diverse thermoelectric properties and mechanical flexibility. Additionally, we have explored the application of flexible thermoelectric fibers, particularly their integration into wearable fabrics, and demonstrated their utility in thermoelectric power generation, refrigeration, and temperature sensing.