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Bamboo-based devices! A new method to fabricate silver conductive coatings into the inner walls of bamboo vascular bundles is disclosed. The hollow conductive microchannels enabled the development of new electrical and electrochemical devices.

Annealing of sugarcane bagasse cellulose or lignin biocarbons under isopropanol vapor has induced an improvement in electrical conductivity of these materials. Remarkably, the sheet resistance dropped nearly three times for lignin biocarbon treated with isopropanol vapors. The use of isopropanol vapor annealing has increased sp2 carbon and decreased oxygenated functionality contents of these biocarbons. These chemical changes were confirmed by X-ray photoelectron and Raman spectroscopy analyses. Transmission electron microscopy images revealed the formation of graphitic domains on samples pyrolyzed in the presence of isopropanol, while electron energy loss spectroscopy mapping at a nanoscale showed an increase in graphitic characteristics of the particles. These chemical and structural changes of biocarbons have improved their electrical conductivity and decreased sheet resistance values of conductive tracks prepared with such materials. As a proof of concept, we fabricated flexible electronic circuits and paper-based electrochemical devices using conductive lignin-based inks prepared with our method.

Nanocellulose is a promising material for fabricating green, biocompatible, flexible, and foldable devices. One of the main issues of using nanocellulose as a fundamental component for wearable electronics is the influence of environmental conditions on it. The water adsorption promotes the swelling of nanopaper substrates, which directly affects the devices’ electrical properties prepared on/with it. Here, plant-based nanocellulose substrates, and ink composites deposited on them, are chemically modified using hexamethyldisilazane to enhance the system’s hydrophobicity. After the treatment, the electrical properties of the devices exhibit stable operation under humidity levels around 95%. Such stability demonstrates that the hexamethyldisilazane modification substantially suppresses the water adsorption on fundamental device structures, namely, substrate plus conducting ink. These results attest to the robustness necessary to use nanocellulose as a key material in wearable devices such as electronic skins and tattoos and contribute to the worldwide efforts to create biodegradable devices engineered in a more deterministic fashion.