We report on a novel electromechanical energy scavenging and wireless interrogation scheme using low frequency components of musical vibrations. The device incorporates a piezoelectric cantilever beam that converts the acoustic vibrations into electric power; rectifying circuitry; a storage capacitor in parallel with a PDMS based inductive pressure sensor; and a ferrite core. Musical sound wave from a loudspeaker induces vibrations in the piezoelectric cantilever at harmonics, which match its resonant frequency. This, in turn generates a voltage that is rectified and stored in the capacitor. At non-resonant harmonics, the supply is interrupted, causing the stored charge to be dumped into the sensing LC tank inducing oscillations at its natural frequency, which is picked up externally with a receiver coil. Applying pressure reduces the distance between the ferrite core and the coil, changing the inductance and hence modulating the resonance frequency of the LC tank.Multimedia Publications
Our group has developed energy harvesting devices based on capacitive sensing arrays. The devices are powered by the insertion and removal of charge on diaphragms whose deflection changes with variations in applied pressure gradients. The employment of a low boiling point liquid in the MEMS device increases the harvesting performance, resulting in readily available power of 0.5 μW for pressure gradients as low as 90 mmHg.