Remarkable piezoelectric properties in thin films of cellulose nanofibers after electrochemical poling

Abstract

Internet-of-everything (IoE) is defined as networked connections of things, people, data and processes. IoE nodes, preferably shaped as printed flexible systems, serves as the frontier outpost of the Internet and comprises devices to record and regulate states and functions. To power distributed IoE nodes in an ecofriendly manner, technology to scavenge energy from ambience and self-powered devices are developed. For this, piezoelectricity is regarded as a key-property, however current technology typically based on polyvinylidene difluoride (PVDF) co-polymers, are expensive and produced via toxic protocols. We report piezoelectric characteristics of electrochemically poled cellulose nanofiber (CNFs) thin films processed from water dispersions. Poling these films at humid conditions cause breaking and reorientation of CNF segments, which results in enhanced crystal alignment rendering the resulting material piezoelectric. Generators based on poled CNF show similar piezoelectric voltage and coefficient, here measured to d33 = 46 pm/V, as for devices including PVDF copolymer layers of similar thickness. Our findings promise for low cost and printable ecofriendly piezoelectric-powered IoE nodes.