Here, we fabricated nanofiber (NF)-based triboelectric nanogenerators (TENGs) from natural biopolymers using the industrially scalable solution blowing. This technique eliminates severe restrictions on solutions to be used and allows one to achieve biocompatible devices. Here, solutions of soy protein and lignin were blown into continuous monolithic NFs of hundreds of nanometers in diameter. The technique we employed yields large-area NF mats within tens of minutes and has never been employed to form TENGs. Furthermore, in contrast to electrospun and meltblown fiber mats, solution-blown NF mats are much fluffier/porous, which is beneficial for achieving higher voltages by means of triboelectricity. In particular, triboelectricity generated by our biopolymer-based TENGs revealed that they hold great promise as sustainable and environmentally friendly self-powered devices for biomedical applications with the highest efficiency in their class. Moreover, these are the first nanotextured plant-derived biopolymer-made TENGs.

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Abstract

Any rational theory of electrostatic atomizers (EAs) would require a detailed understanding of the nature of the polarized layer near the electrode, since this is the source of the electric charge carried by the jets issued from the EAs. The polarized layer either is driven out as the electrically-driven Smoluchowski flow and/or entrained by the viscous shear imposed by the bulk flow. The standard Gouy-Chapman theory of polarized diffuse layers implies zero electric current passing across the layer, which is impossible to reconcile with the fact that there are leak currents in the EAs. Here, we show that the electric current through the EA is controlled by faradaic reactions at the electrodes. The experiments were conducted with stainless steel or brass pin-like cathodes and three different anode (the conical nozzle) materials, which were copper, stainless steel, and brass. The different electrode materials resulted in different spray, leakage, and total currents in all the cases. Accordingly, it is shown that the total electric current generated by EAs can be controlled by the cathode and anode materials, i.e., by faradaic reactions on them. This lays the foundation for a more detailed understanding and description of the operation of EAs.