Integrated Power Harvesting System Including a MEMS Generator and a Power Management Circuit

Abstract

This paper presents a novel ambient energy scavenging system for powering wireless sensor nodes. It uses a MEMS generator and an ASIC power management circuit. The system is realised as a System On a Package (SoP) with all components fabricated entirely using the microfabrication techniques. The electromechanical transduction is performed using the piezoelectric effect of Aluminium Nitride thin films. The reported experimental results prove the possibility of exploiting very low amplitude signals delivered by the generator for charging a storage capacitor. It is also shown that the proposed system of 5mm 3 can endlessly power a simple wireless sensor node; while a Lithium-Polymer thin film battery of the same volume can do so only for less than two months.

Piezoelectric MEMS for energy harvesting

“…Two piezoelectric modes, d 31 or d 33 , are commonly used in piezoelectric microdevices ( Figure 4 ). The relative directions of the electric fi eld and the strain distinguish them: d 31 when the electric fi eld is perpendicular to the input strain, and d 33 when they are parallel.…”

“…The relative directions of the electric fi eld and the strain distinguish them: d 31 when the electric fi eld is perpendicular to the input strain, and d 33 when they are parallel. 51 Conventional MEMS piezoelectric devices/ actuators have a d 31 confi guration in which a piezoelectric layer is sandwiched between top and bottom electrodes. For a d 31 mode energy harvester, the generated voltage is proportional to the thickness of the piezoelectric layer ( t xx ), the effective piezoelectric constant, g 31,f (Vm/N), and the applied stress, σ xx .…”

Piezoelectric MEMS Power Generators for Vibration Energy Harvesting

“…The power output obtained was of 2.16μW. Some Other MEMS cantilever piezoelectric power generators examples of different materials and structures can be found in [33] and [34]. Other than single beam structures, Figure 7 [35]shows a MEMS power generator array based on thick-film piezoelectric cantilevers.…”

A 2-DOF MEMS Ultrasonic Energy Harvester

“…However, the efficiency of vibration-to-electricity conversion is quite low in existing microgenerators, since: 1) most of the reported kinetic generator techniques suffer from scavenging in a narrow bandwidth from ambient sources due to their single resonance frequency and 2) most devices are designed to harvest energy in a single direction, which wastes the vibration energy existing in other directions [8]. An exception is the multifrequency piezoelectric harvester reported in [9] that was shown to broaden the bandwidth by using three piezoelectric bimorph cantilevers with identical dimensions but different masses.…”