Self-assembly of unidirectionally polarized piezoelectric peptide nanotubes using environmentally friendly solvents

[Display omitted] •Large-scale piezoelectric FF nanotubes are synthesized using an environment-friendly method with a biocompatible solvent system.•FF nanotubes were unidirectionally polarized and exhibit strong piezoelectricity.•High performance and stable piezoelectric nanogenerator with FF nanotubes was introduced. Diphenylalanine (FF) peptide nanotubes are considered to be particularly promising biomaterials for bio-implantable devices due to their unique characteristics, such as strong piezoelectricity, remarkable physical properties, and chemical stability. However, the 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP)-water co-solvent system, which is often used for FF nanotube synthesis, is toxic and expensive. These are limitations for the development of eco-friendly and practical biocompatible piezoelectric devices. In this study, we developed an eco-friend and cost-effective approach for aligning piezoelectric FF nanotubes using an ethanol–water solvent system. First, we fabricated horizontally aligned FF nanotubes via a meniscus-driven self-assembly process. The fabricated FF nanotubes using ethanol exhibited unidirectional polarization and strong piezoelectric properties comparable to HFIP solvent based FF nanotubes. In addition, the FF-based piezoelectric nanogenerator generates voltage, current, and power of up to 1.66 V, 19.4 nA, and 19.2 nW, respectively, with a force of 40 N. These FF-based piezoelectric nanogenerators will be applicable as a compatible energy source for future biomedical applications.