From Nature to Electronic Devices: edible molecules fine-tuning for the obtainment of benign organic semiconductors

During the past decades, ingestible electronics1 paved the way for more sustainable and safer alternatives to standard electronic devices, so that they could work within the human body, allowing health monitoring and modern medical treatments. However, until now a scarce attention to material selection has required device recollection and supervised administration. The pioneering goal of the newly-born edible electronics field 2is the development of a safe and cost-effective technology which can expand its potential application to various areas. Its strength relies in an accurate choice of device component materials. Food, food-derived or edible synthetic molecules are chosen as raw materials to build disposable and harmless electronic devices whose constituents are safe for ingestion and degradable within the body after fulfilling their tasks. The exploitation of the inherent electronic properties of biocompatible materials allows the creation of life quality improvement tools for biomedical, pharmaceutical and food monitoring purpose. Although they play a key role in electronic devices, semiconductors are the least studied materials in terms of edibility. They must balance high electronic performances, safety for ingestion and electronic stability. Nature provides π-conjugated scaffolds as many food owes its colour to the molecular structures of chromophores. However, electronic properties are also linked to solid state molecular packing,3 a not-so-easy-to-find feature in materials of natural origin. In order to expand the knowledge on benign semiconductors, we are currently studying the properties of different π-conjugated natural pigments and their derivatives as well as safe strategies to isolate them starting from dietary supplements. Phycocyanin (blue spirulina) and chlorella pyrenoidosa have been taken into consideration as they provide access respectively to phycocyanobilin and chlorophylls. The latter are under investigation to be used as semiconductors in organic thin film transistors both for their easily tailorable molecular structure and HOMO level (HOMOChl-a 5.1 eV).4 The encouraging preliminary results obtained whit astaxanthin and β-carotene when used as semiconductive layer in organic field effect transistors (OFETs) has prompted us to synthetize and study different astaxanthin derivatives and polymers as well. Astaxanthin functionalization could actually influence the packing in solid state, thus modify the transport properties of the material. (1) Steiger, C.; Abramson, A.; Nadeau, P.; Chandrakasan, A. P.; Langer, R.; Traverso, G. Ingestible Electronics for Diagnostics and Therapy. Nat Rev Mater 2019, 4 (2), 83–98. https://doi.org/10.1038/s41578-018-0070-3. (2) Wu, Y.; Ye, D.; Shan, Y.; He, S.; Su, Z.; Liang, J.; Zheng, J.; Yang, Z.; Yang, H.; Xu, W.; Jiang, H. Edible and Nutritive Electronics: Materials, Fabrications, Components, and Applications. Adv Mater Technol 2020, 5 (10). https://doi.org/10.1002/admt.202000100. (3) Sharova, A. S.; Melloni, F.; Lanzani, G.; Bettinger, C. J.; Caironi, M. Edible Electronics: The Vision and the Challenge. Adv Mater Technol 2021, 6 (2). https://doi.org/10.1002/admt.202000757. (4) Buscemi, G.; Vona, D.; Trotta, M.; Milano, F.; Farinola, G. M. Chlorophylls as Molecular Semiconductors: Introduction and State of Art. Adv Mater Technol 2022, 7 (2). https://doi.org/10.1002/admt.202100245.