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

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.

Analytical Modeling and Validation of a Preloaded Piezoceramic Current Output

Energy harvesting using piezoceramic has drawn a lot of attention in recent years. Its potential usage in microelectromechanical systems is starting to become a reality thanks to the development of an integrated circuit. An accurate equivalent circuit of piezoceramic is important in energy harvesting and the sensing system. A piezoceramic is always considered to be a current source according to empirical testing, instead of the derivation from its piezoelectric characteristics, which lacks accuracy under complicated mechanical excitation situations. In this study, a new current output model is developed to accurately estimate its value under various kinds of stimulation. Considering the frequency, amplitude and preload variation imposed on a piezoceramic, the multivariate model parameters are obtained in relation to piezo coefficients. Using this model, the current output could be easily calculated without experimental testing in order to quickly estimate the output power in energy harvesting whatever its geometric shape and the various excitations.

Влияние освещения на пьезоэлектрические характеристики кварцевых резонаторов

The results of the effect of lighting on the piezoelectric characteristics of quartz resonators in the form of a tuning fork, which have been pre-trained by increased friction from the external environment, are presented. A significant change in the piezoelectric characteristics of such resonators was found depending on the intensity and spectrum of illumination. It is assumed that the detected change in the characteristics of the resonators is due to dislocations formed in the resonator during training with increased friction of the external environment, and is a manifestation of the well-known photoplastic effect and its quenching.