Magnetoelectric Composite Material Technologies for Autonomous Smart Systems: From Rigid to Flexible Structures

Abstract Magnetoelectric composites are multifunctional materials capable of sensing magnetic and mechanical signals, actuation under magnetic and electric fields, and dual energy harvesting from stray magnetic fields and mechanical vibrations. They are thus reckoned as an enabling material technology for autonomous smart systems to be at the core of a range of applications, from nodes in wireless sensor networks to be massively deployed in the information society, to bioimplanted devices for medical diagnosis and therapeutics, wearable electronics and electronic skin in robotics. Large progress has been made during the last decades, and composite bulk laminate structures with outstanding response, in principle ready for the applications, have been demonstrated. Efforts now concentrate on ensuring reliability, mostly associated with preserving elastic coupling between components under operation, and on fabrication up-scaling and miniaturization, composite integration into microelectromechanical systems, and the fabrication of flexible structures. The spotlight summarizes and updates the authors' contributions to solve these challenges. On one hand, a number of advanced low-temperature processing techniques, either for bulk or thin-film configuration, have been demonstrated for the preparation of rigid and flexible layered structures with high-quality interfaces and sizeable magnetoelectric coefficients. Several high Curie-temperature, high-sensitivity piezoelectric perovskite BiMeO3-PbTiO3 systems (Me: Sc3+ or Fe3+) with very good down-scaling behavior of properties have been considered, combined with either magnetic spinel oxides or metals. On the other hand, insights into the causes that determine and limit response beyond component fraction and interface quality have been gained. Besides, preliminary results on the fabrication of flexible structures based on the piezoelectric biopolymer PLLA by 3D printing are presented. Responsible (green) electronics need to be developed within the framework of the circular economy.