Piezoelectric Rotational Energy Harvester for Body Sensors Using an Oscillating Mass

A rotational energy harvester for human body applications is presented in this paper. An oscillating mass, similar to those found in wristwatches is used as a proof mass to act on a piezoelectric impulse excited transduction mechanism that is particularly well suited for these low-frequency, non-harmonic vibrations. The electromechanical coupling is enhanced by letting a piezoelectric beam vibrate at its natural frequency after an initial excitation. The plucking of the beam is achieved by a completely contact less magnetic coupling, beneficial for the longevity of the device. The potential advantages of rotary harvesters are discussed and a first design is introduced. The measurement results demonstrate the successful implementation and make it possible to investigate the influence of different factors on the power output. At a frequency of 2 Hz a maximal power of 2.6 microwatt was achieved when tested on a rocking table.