Ultrathin BiFeO₃ breaks the 30 nm limit, delivering fourfold stronger piezoelectricity

Piezoelectric materials, which convert mechanical stress into electricity and vice versa, are essential components in sensors, actuators, and energy-harvesting devices. However, the best piezoelectric materials, such as lead zirconate titanate (PZT), are toxic because they contain lead—prompting a search for lead-free alternatives.