Piezoelectric energy harvesting from ambient vibrations offers an environmentally friendly approach to powering distributed sensors for the Internet of Things. This paper gives a direct comparison of Pb(Zr,Ti)O 3 (PZT)-and (K,Na)NbO 3 (KNN)-based harvesters using a compliant mechanism harvester design for resonant frequencies of 20, 40, and 70 Hz. At 70 Hz, the measured power densities for PZT-and KNNbased devices are 1139 and 31 μW/mm 3 , respectively, for unimorph structures on nickel foils of 25 and 50 μm in thickness. The power density ratios scale proportionally to the material energy harvesting figures of merit. Energy harvesting with the compliant mechanism design is twice as efficient when compared to harvesting with a simple cantilever beam.
Fluidlastic dampers, isolators and absorbers are stand alone components used to reduce vibrations in many civil, mechanical and aerospace structures. This research demonstrates how additive manufacturing can integrate fluidlastic circuits inside a metal part. An example device with relatively simple monolithic construction consists of two chambers separated by a thin membrane that is connected to the upper chamber by a bridge compliant mechanism. The chambers are filled with fluid and are connected by a long thin channel inertia track that coils around their periphery. Elastic strain deflects the bridge causing the membrane to bulge into the upper chamber. This causes a pressure gradient that drives the fluid flow from the upper chamber to the lower chamber through the inertia track. Enabled by additive manufacturing, design parameters such as chamber dimensions, constitutive material, fluid viscosity, etc. can be easily tailored to provide targeted resonance over a desired frequency range. Experimental results provide evidence of fluid pumping at the membrane’s first resonant frequency.
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