Rotary disk multi-phase freestanding-electret generator with enhanced power and low ripple output

Highlights: • Rotary disk multi-phase freestanding-electret generator (FEG) is demonstrated with enhanced power and low ripple output. • Output power enhancement is benefited by generator capacitance reducing and positively utilizing the edge effect. • Two-phase FEG has the highest maximum average power, 78.4% higher than the conventional single-phase FEG. • Each phase of MFEG is independent, which can be used separately, one as sensing signal and the other as energy output. Energy harvesters with higher power and direct-current (DC) output are of great significance for the energy supply of electronic devices. Here, we demonstrate rotary disk multi-phase freestanding-electret generators (MFEGs) with enhanced output power and low ripple output via a novel design. This novel design can enhance the output power by the reduction of generator capacitance and the improvement of the transferable charge density through positively utilizing the edge effect. The factors which both theoretical and experimental results show that the two- and three-phase FEGs have higher maximum output power than that of the conventional single-phase FEG (SFEG) and the two-phase FEG (TFEG) has the highest one. To further improve the output power, we optimize the structural parameters of TFEG and obtain 78.4% higher maximum output power than that of the optimal SFEG in experiment. Moreover, MFEGs connected to rectifier bridges obtain almost DC outputs. And since each phase of MFEGs is independent, the output of each phase can be utilized separately, for example, one as sensing signal and the other as energy output, providing a broad prospect for self-powered sensing.