Leaf-Inspired Flexible Thermoelectric Generators with High Temperature Difference Utilization Ratio and Output Power in Ambient Air

The inherently small temperature difference in air environment restricts the applications of thermoelectric generation in the field of Internet of Things and wearable electronics. Here, a leaf-inspired flexible thermoelectric generator (leaf-TEG) that makes maximum use of temperature difference by vertically aligning poly(3,4-ethylenedioxythiophene) polystyrene sulfonate and constantan thin films is demonstrated. Analytical formulae of the performance scales, i.e., temperature difference utilization ratio (phi(th)) and maximum output power (P-max), are derived to optimize the leaf-TEG dimensions. In an air duct (substrate: 36 degrees C, air: 6 degrees C, air flowing: 1 m s(-1)), the 10-leaf-TEG shows a phi(th) of 73% and P-max of 0.38 mu W per leaf. A proof-of-concept wearable 100-leaf-TEG (60 cm(2)) generates 11 mu W on an arm at room temperature. Furthermore, the leaf-TEG is flexible and durable that is confirmed by bending and brushing over 1000 times. The proposed leaf-TEG is very appropriate for air convection scenarios with limited temperature differences.