Magnetic field and ultrasound induced simultaneous wireless energy harvesting

Energy harvesting can provide continuous power required for operating biomedical, physical, and chemical devices. However, providing sufficient power for many devices utilizing only a single modality through energy harvesting is still challenging due to its restricted power density considering the source energy that is below human body safety limits. Here, for the first time a high-power density energy harvester using piezoelectric and magnetoelectric conversion is demonstrated operating within the human body safety limit. This dual harvester can harvest energy from different directions, which makes it insensitive to the source orientation. Prototype design is demonstrated to harvest magnetic and ultrasound energies simultaneously from a single device traveling through liquid/tissue media generating an ultra-high power of ∼52.1 mW (a power density of ∼597 mW cm⁻³) across input of ∼500 μT rms magnetic field and ∼675 mW cm⁻² ultrasound intensity, which are below the safety limits prescribed by the IEEE and FDA. This represents an ∼225% improvement compared to individual magnetoelectric systems utilizing a single source under safety limits. The device can recharge a 3 V lithium-ion battery with 1 mA-h capacity at a rate of ∼1.67 mC s⁻¹ in porcine tissue. These findings suggest that the dual energy harvester based on magnetic field and ultrasound intensity has the potential to power various electronic devices, such as implantable devices and embedded components.