A flexible spring-shaped architecture with optimized thermal design for wearable thermoelectric energy harvesting

Despite the rapid advancements made for thin-film thermoelectric materials , the rational design of corresponding thermoelectric devices (TEDs) raises the urgent need for thermal optimization to meet the requirement of efficient utilization of the temperature gradient vertical to the device plane . Herein, a three-dimensional spring-like thermoelectric device (S-TED) with fundamantal dual elastomer layers and air gaps is proposed. The novel device architecture not only inherits excellent flexibility and compressibility , but also enables the capability of harvesting waste heat under vertical temperature gradient. Detailed analysis of thermal modeling indicates that optimization is considered in three aspects compared to conventional TEDs, including the strengthened contact for more efficient interfacial heat transfer, the hindered heat transfer across the device body via the construction of thermally-insulating air gaps, and the effective heat sink that facilitates the rapid heat transfer from device to the ambient. The as-fabricated S-TED delivers a high output power of 749.19 nW under a vertical gradient of 30 K with only three pairs of p-n couple, corresponding to high output power of 416.22 nW cm -2 compared to other reported flexible TEDs. The design strategy conceived in this work will promote the development of high-performance TEDs for flexible and wearable applications.