Piezoelectric strain sensors with auxetic microstructure

Over the past few years the use of wireless sensors and wearable electronics has dramatically grown. These devices are spreading not only to different engineering fields, but also to objects in everyday use. Electro-chemical batteries, that need to be periodically replaced, are making way for alterna- tive solutions as piezoelectric actuators adopted to supply power to devices of smaller and smaller dimensions, from the micro- (MEMS) to the nano-scale (NEMS). In this framework, it is noteworthy the use of multifunctional composite materials adopting piezo- electric periodic cellular lattice structures with auxetic elastic behavior. In the present work, peri- odic anti-tetrachiral auxetic lattice structures, characterized by different geometries, are taken into account and the mechanical and piezoelectrical response are investigated. The equivalent piezoelec- tric properties are obtained adopting a first order computational homogenization approach, gener- alized to the case of electro-mechanical coupling, and various polarization directions are adopted. Moreover, a piezo-elasto-dynamic dispersion analysis adopting the Floquet-Bloch decomposition is performed. We extend to piezoelectric materials the analysis of auxetic beam lattices to evaluate the properties of the dispersion functions of waves propagating in different directions and to describe the acoustic behavior of the periodic material and to detect possible band gaps.