Utilizing star-shaped auxetic metabeams for piezoelectric vibration energy harvesting

This study introduces a star-shaped auxetic cantilever beam for vibration energy harvesting applications. Auxetic materials, characterized by a negative Poisson’s ratio, produce uniform stresses under mechanical loading, making them ideal for enhancing power generation in energy harvesters. The proposed design consists of two piezoelectric layers and a star-shaped auxetic structure that converts mechanical input into electrical energy. The piezoelectric layers are assumed to be wired in parallel configurations. The beam is excited by base motion, with its response analyzed through translational and rotational dynamics and a tip mass attached at its free end. A Timoshenko beam model is developed to derive the coupled electromechanical equations of the auxetic harvester, and an exact solution is employed to evaluate its electrical performance. A 3D finite element model is also constructed to validate the analytical model, with convergence and comparison studies confirming its stability and accuracy. A parametric study investigates the influence of design parameters on the harvested power, revealing that larger auxetic core inclination angles and greater cell rib thickness maximize the power output. The star-shaped auxetic energy harvester achieves a 43% higher output voltage compared to a conventional aluminum harvester under equivalent operating conditions while also reducing weight by 20% without compromising power output. These findings highlight the potential of auxetic structures and multipurpose composites in advancing vibration-based energy harvesting technologies and broader engineering applications.