Giant thermopower of ionic gelatin near room temperature

Abstract

Harvesting heat from the environment into electricity has the potential to power Internet-of-Things (IoT) sensors, freeing them from cables or batteries especially for use as wearable devices. We demonstrate a giant positive thermopower of 17.0 mV K⁻¹ in a flexible, quasi-solid state, ionic thermoelectric material using synergistic thermodiffusion and thermogalvanic effects. The ionic thermoelectric material is a gelatin matrix modulated with ions providers (KCl, NaCl, and KNO₃) for thermodiffusion effect and redox couple (Fe(CN)₆⁴⁻/Fe(CN)₆³⁻ for thermogalvanic effect. A proof-of-concept wearable device consisting of 25 unipolar elements generated over 2 V and a peak power of 5 μW using body heat. This ionic gelatin shows promises for environmental heat-to-electric energy conversion utilizing ions as energy carriers.