(139d) Design and Fabrication of Flexible Thermoelectric Cooling Devices with Enhanced Cooling Performance

In the past decade, wearable and flexible thermoelectric (TE) coolers have emerged as promising solutions for active cooling, particularly in military contexts to mitigate heat stress for diverse military and civilian applications. However, the widespread adoption of commercially available ceramic-packaged TE devices has been hindered by their rigidity and limited cooling efficiency. To address these issues, we have recently developed a highly flexible thermoelectric device (TED) utilizing bismuth telluride-based TE pillars, thin copper electrodes, and insulating Ecoflex rubber. Multiple TED prototypes were fabricated with Ecoflex films of varying thicknesses. Different arrangements of copper electrodes were implemented to optimize their performance and stability. Experimental results demonstrated that these TEDs maintained good stability even after 1000 bending cycles.

These TEDs, when coupled with efficient and flexible heatsinks made from Ecoflex silicone rubber, flexible Cu foam, and a phase-change material (PCM), demonstrated remarkable performance. For the flexible heatsink, aluminum nitride (AlN) was incorporated into Ecoflex silicone rubber to achieve high flexibility and excellent thermal conductivity, resulting in a soft rubber mixture. The PCM used in the heatsink was dodecyl myristate with a 37 °C melting temperature, which offered efficient and sustainable solutions for temperature regulation in TEDs, maintaining a relatively constant temperature within a defined range. It absorbed excess heat when the heatsink temperature rose above the phase change temperature. The TED with the PCM-based heatsink effectively lowered skin temperature from 36 °C to a comfortable 32 °C for a duration of at least 23 minutes, even in ambient temperatures set at 37 °C. The fabricated TEDs underwent thorough characterization and evaluation for their active cooling capabilities, in addition to assessment alongside various heatsinks. Their flexibility and durability were also examined. Detailed discussion on the fabrication process and analysis of these devices will be provided.