Biodegradable CuI/BCNF composite thermoelectric film for wearable energy harvesting

Cellulose is the most widely distributed polymer material in nature and is considered a low-cost, green and recyclable material. Because of its excellent mechanical, optical and thermal properties, people are interested in the research of cellulose-based flexible electronic devices. Among them, bacterial cellulose has a low fiber bundle size during the production process and is easier to process to obtain nanofibers. Hereby, in this study the composite thermoelectric film was prepared from bacterial cellulose nanofibers (BCNFs) and copper iodide (CuI), a low-toxicity thermoelectric material. Hydrophobic properties of the composite thermoelectric film were obtained by immersing in AKD emulsion. It showed good mechanical flexibility and high biocompatibility. CuI particles can be recovered successfully through cellulase simulating the degradation process, and the closed-loop of preparation-recycling can be completed. In addition, it achieves an open circuit voltage of 11.3 mV and output power of 2.76 nW at a temperature difference of 70 K. This work not only confirms the environmental protection of CuI/BCNF thermoelectric film, but also provides a strategy for the recycling of thermoelectric equipment.