Mat-like flexible thermoelectric system based on rigid inorganic bulk materials

This paper reports on a mat-like flexible thermoelectric system (FTES) based on rigid inorganic bulk materials, i.e. Bi–Te compounds. Inorganic bulk materials exhibit higher thermoelectric performance and can create a larger temperature drop due to their considerable height compared with organics and printable inorganics, meaning the FTES can produce an impressive power output. We show that the FTES, wherein both a thermoelectric module and a heat sink are integrated, is flexible enough to be adapted to any irregularly shaped surface. In the FTES, p- and n-type legs composed of a thermoelectric module are placed inside holders, which are connected to one another using flexible wires. Powered by a portable battery, the FTES was used to refrigerate human skin. As a result, a temperature drop of approximately 4 K was experimentally demonstrated, which humans felt as ‘cold’ or ‘very cold’, based on analysis. This indicates the feasibility of using the proposed FTES to control the temperature of the human body, even when using a portable battery. This was also applied to body heat harvesting. The FTES generated approximately 88 µW of power, which is sufficient to operate most wearable and/or implantable sensors. Our analysis based on human thermoregulatory modeling indicates that both refrigeration and power generation capacity can be further enhanced by improving the thermal contact between the FTES and human skin. The FTES shows potential for wearable refrigeration and body heat harvesting.