A plucking rotational energy harvester with tapered thickness and auxetic structures for increasing power output

The rotational energy harvester (REH) has been widely investigated as a potential method to power electronic devices in the Internet of Things. Despite the advances in the REH, there remains a challenge to sufficiently harvest energy from low frequency rotations. To address this issue, a plucking REH with tapered thickness and auxetic structures (TAPREH) is proposed in this paper. By incorporating a tapered thickness beam, auxetic structures, and frequency up-conversion method, the proposed design can improve the generated energy under low frequency excitations. The performance of the proposed design is analyzed using finite element simulation, which shows a good agreement with the corresponding experimental results. Experimental validation of the proposed design revealed a peak power output of 0.489 mW at 1.5 Hz, representing an increase of 898% compared to the conventional plucking REH without auxetic structures (PREH). Moreover, the proposed design exhibits a more uniform stress distribution compared with the existing plucking REH with uniform thickness and auxetic structures (UAPREH). Consequently, the peak power output of the proposed design is increased by 186% compared with that of UAPREH while having lower maximum stress.