High Performance Bacterial Cellulose Organogel‐Based Thermoelectrochemical Cells by Organic Solvent‐Driven Crystallization for Body Heat Harvest and Self‐Powered Wearable Strain Sensors

As a low‐grade sustainable heat source, the human body provides a great driving force for converting heat into electric energy using thermoelectric materials, which can effectively power wearable electronics. However, the low thermoelectric conversion efficiency is not sufficient to achieve energy autonomy in the operation of wearable devices. Herein, wearable bacterial cellulose (BC) organogel‐based thermoelectrochemical cells (TECs) are designed and prepared with K 4 Fe(CN) 6 /K 3 Fe(CN) 6 as a redox couple. The addition of propylene glycol significantly improves the mechanical properties of the TECs and drives K 4 Fe(CN) 6 to gradually crystallize, resulting in the concentration gradient of redox ions, which significantly enhanced the heat‐to‐electricity conversion efficiency (from 1.27 to 2.30 mV K −1 ), proving that they are promising candidates for powering flexible and wearable devices in various application scenarios. The TECs are further assembled into self‐powered strain sensors, which can detect the movement of the human body under various tensions and pressures in real time with high sensitivity. This indicates that the BC organogel‐based TECs for self‐powered strain sensors have great application potential in the wearable field.