Exploring the impact of auxetic structures in a hybrid design approach to low-frequency vibration energy harvesting

Abstract This study introduces an auxetic structure designed as a folded beam to improve the energy conversion efficiency of a hybrid energy harvester that includes piezoelectric, electromagnetic, and triboelectric harvesting units. Three auxetic structures have been considered to replace conventional springs, serving as folded beams within a multi-stable nonlinear system. The unique properties of auxetic structures, including exceptional energy absorption capacity, bending performance, resistance to torsional deformation, significant expansion under tensile forces, and reduced weight, contribute to improved energy density. These characteristics also enhance the conversion efficiency of the hybrid harvester when stimulated by low-frequency vibrations. By utilizing the auxetic structure, the power output is significantly enhanced compared to conventional structures, with an increase of approximately 1.55 times. To evaluate the overall performance of the tri-hybrid device featuring an auxetic design, an experimental study is carried out using an external excitation of 1 g at 5 Hz, resulting in a normalized power density of 3.56 mW cm −3 g −2 . This research showcases a notable progress in low-frequency vibration energy harvesting through the use of auxetic structures, providing a versatile and effective solution for powering low-energy electronic devices and sensors.