A Study on Bio-Compatible Piezoelectric Materials by First Principles Calculation

Abstract

Bio-compatible piezoelectric materials are becoming increasingly important for actuators and sensors in medical devices, that is Bio-MEMS such as health monitoring systems and drag delivery systems. In this study, we challenged to search new piezoelectric materials with bio-compatibility by first principles calculation. Firstly, constituent atom of bio-compatible piezoelectric materials have been specified by HSAB method from the viewpoint of interaction energy with in vivo molecules. Secondly, in order to create a perovskite-type crystal structure with good piezoelectric response, the combination of bio-compatible atoms was selected to satisfy geometric stable condition defined by tolerance factor. As a result, we discovered 7 kinds of new piezoelectric materials. One of them, MgSiO₃ is known to be a mineral with perovskite-type crystal structure, but it has never been applied to piezoelectric materials. Therefore, we focused on MgSiO₃ as a candidate for biocompatible piezoelectric materials, and then the stable cubic and asymmetric tetragonal structures of MgSiO₃ were analyzed by first principles DFT. Finally, structural phase transition of MgSiO₃ has been investigated on the assumption of linear structural change from cubic structure to tetragonal one. DFT calculation indicated that MgSiO₃ can change spontaneously to tetragonal structure with electric polarization, and that MgSiO₃ can present a good piezoelectricity.