A handy motion driven, frequency up-converting piezoelectric energy harvester using flexible base for wearable sensors applications

This paper presents a piezoelectric energy harvester driven by human handy motion vibration to be used in wearable sensors applications. It employs a metal ball to impact (mechanical) consecutively on two flexible sidewalls (while shaken) that act as the bases for two mass-loaded piezoelectric unimorph generating beams. Each impact allows the sidewall to transfer impulsive force to the loaded-mass and causes voltage generation by virtue of piezoelectric effect. It offers mechanical frequency up-conversion strategy (frequency of generated voltage waveform is 60Hz). Besides, instead of direct mechanical impact on piezo-beam, impact on the flexible base meets the reliability challenge from its quick damage. Moreover, use of flexible base for piezo-beam minimizes the power loss by minimizing the quick decay of the generated voltage or power. Our fabricated macroscale prototype harvester is capable of generating maximum 175μW average power while it is manually shaken at 4.96Hz.