Sticky Thermoelectric Materials with Ultra-thin High Performance Foam for Hierarchically Designed Flexible Peltier Sheets

To improve energy efficiency of temperature conditioning for human body and to also prepare for extreme heat with climate change, Peltier human coolers have been developed and commercialized [Ref. 1]. However, its usage has been limited, such as a neck cooler, because the commercial Peltier devices are heavy and solid, constraining the size of contacting area for heat transfer. To slim their thickness and weight and to also meet the multiple complex requirements for mass production of flexible Peltier sheets, we have designed and developed sticky thermoelectric (TE) materials with a strategy adopting from other organic devices like organic light-emitting diodes and dye-sensitized solar cells: hierarchically hybridizing the multiple components to meet each requirement [Ref. 2-4]. At the microscale hybridizing inorganic TE particles with low-thermal-conductive organic solvents, the sticky TE materials suppresses the thermal conduction, which enable to keep the temperature difference based on the Peltier effect even on the thin sheet structure for flexibility. At the nanoscale, the surface/interface modification reduces the electrical resistance between TE particles. At the atomic scale, the Seebeck coefficient of TE particles is optimized. Instead of the organic sheet sealant surrounding the sticky TE materials, in this study, we employ an ultra-thin foam sheet because of its high sealing ability, low thermal conductivity, and shock absorption capacity. We observed that the low thermal conductivity contributes to keeping larger temperature difference between the upper and lower sides, and also confirmed that the shock absorption capacity relaxes the tension on the upper and bottom electrode sheets during the bending. We discuss details in this presentation.<br/><br/><br/>Ref. 1: Itao et al. J Jpn Soc Precis Eng 2016;82:919-924 (in Japanese).<br/>Ref. 2: Satoh et al. Sci Technol Adv Mater 2018;19:517-25.<br/>Ref. 3: Satoh et al. MRS Advances 2020;5:481-7.<br/>Ref. 4: Satoh et al. Soft Sci 2022;2:15.