Finally, the nanocomposite-based US-driven PENGs have a good biocompatibility, with no cytotoxicity or immune response in vivo, indicating their potential for developing wireless power generators and actuators for medical implant devices. Furthermore, the US-PENG actuator system, which is composed of an amplifier and a microcontroller, could efficiently convert ultrasonic energy into electricity or instructions to switch on/off small electronics in the tissues and organs of mice. Remarkably, piezoelectric nanogenerators could attain an extraordinary output power of 521 μW cm −2 under ultrasound stimulation, which is far greater than that of force-induced PVDF-based nanogenerators and other ultrasound-driven triboelectric generators. For US-driven PENGs, the electrons and holes are generated not only from the interfaces between the NPs and the matrix, but also from the dipoles vibrating in the smaller lamellae of ferroelectric β-phase crystals in poled nanocomposites. Herein, we successfully synthesized core-conductive shell-structured BaTiO nanoparticles as nanofillers to design implantable poly(vinylidenefluoride- piezoelectric nanogenerators (PENGs) and actuators for harvesting ultrasound (US) underneath the skin. Based on ultrasonic coupling effects at the interfaces, the interfacial architecture is a critical parameter to attain desirable electromechanical properties of nanocomposites. Transcutaneous energy-harvesting technology based on ultrasound-driven piezoelectric nanogenerators is the most promising technology in medical and industrial applications.

Piezo electric effect