Journal Article memristors piezoelectric Membranes, Artificial Metglas PZT Research Support, Non-U.S. Gov't Review artificial neurons artificial olfactory systems composites energy harvesting epitaxial oxide thin films ferroelectric figure-of-merit gas sensors graphene heterostructures hybrid hysteresis magnetoelectricity multifunctional oxide nanogenerator nanorods neuromorphic computing olfactory synapses probabilistic neural networks pyroelectric self-resonance tuning silicon oxide