Bacterial cellulose hydrogel-based wearable thermo-electrochemical cells for continuous body heat harvest

Wearable thermo-electrochemical cells (TECs) provide a low-cost, high-efficiency and scalable approach to immediately convert body heat energy to electrical energy, which exhibit application possibilities as power sources in wearable devices . However, the current research status is that few reported TECs with high Seebeck coefficient ( Se ) have consistently comparable ionic conductivity ( σ ). In order to achieve high σ and Se simultaneously, here we prepared a bacterial cellulose (BC) hydrogel-based TEC with excellent power factor ( PF , 60.37 mW m -1 K -2 ). BC hydrogel not only exhibits good mechanical properties , but also is the key factor to improve σ (26.1 S m -1 ), this is mainly because its large number of surface hydroxyl groups are more conducive to the transport of cations. Benefiting from the synergy of thermodiffusion and thermogalvanic effect, Se is efficiently increased from 1.27 to 1.52 mV K -1 . TEC array based on 5 BC hydrogel can light a red light-emitting diode (LED) via a voltage amplifier. Meanwhile, we designed a proof-of-concept watch strap to harvest body heat, which demonstrated its promise in wearable applications. Graphical abstract. • BC hydrogel-based electrolytes have good mechanical properties. • BC hydrogel-based TEC achieves excellent PF of 60.37 mW m -1 K -2 due to high Se and σ of the system. • Wearable watch-strap sharped TECs are designed to harvest body heat.