Vacuum Formed Spherical Triboelectric Architecture Overcoming Direction Constraints for 3D-Omnidirectional Ultrasonic Energy Receiving

Ultrasound-driven triboelectric nanogenerators (UD-TENGs) have emerged as promising ultrasonic energy converters for underwater and biomedical applications. Nevertheless, prevailing planar UD-TENGs exhibit pronounced directivity, which necessitates a prescribed deployment direction or complex ultrasound alignment strategies, and thus restricts both the output performance and practicality of these devices. This work introduces an ultrasound-driven spherical triboelectric nanogenerator (UD-STENG) that, for the first time, achieves 3D-omnidirectional ultrasonic energy harvesting (UEH) via capacitive triboelectric technology. By conformally integrating triboelectric layers onto spherical surfaces through vacuum forming, the UD-STENG establishes a spatially symmetric ultrasonic-triboelectric interface and delivers near-isotropic outputs regardless of the ultrasound incidence directions, generating average output powers from 0.42 to 2.92 mW over ultrasound intensities ranging from 0.05 to 3.0 W cm⁻². As a new UEH mode, the UD-STENG maintains effective operation under dynamic harvesting conditions and can be simultaneously driven by ultrasound sources from multiple directions for enhanced output. In implantable demonstrations, the UD-STENG operates independently of implantation directions and further supports practical functions, including real-time wireless data transmission and on-demand modulated pulse delivery. These advances expand the spatial operating window of UD-TENGs and lay the foundation for next-generation 3D triboelectric ultrasonic energy converters.