NEHSTECH

Nonlinear Energy Harvesting Solutions for Micro- and Nano-Technologies

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 Obiettivo del progetto (Objective)

'Vibration energy harvesting at micro-scale is considered essential to enable low-power, maintenance free and long-lasting wireless sensor networks (WSNs). However, many problems still limit the efficiency of current vibration-driven generators: narrow bandwidth, low power density, MEMS scaling, inconsistent vibrating sources. The scientific objective of this research project is to overcome the present limitations by proposing an innovative dynamical concept. This is based on the exploitation of multiple-mass velocity amplification and nonlinear dynamical features. An high-efficient micro vibration energy harvester will be implemented by using electrostatic (and/or electromagentic) conversion method. The prototype will be realized by using silicon-base MEMS fabrication facilities at disposal of the hosting institute. In terms of power density and frequency bandwidth performances, this technology is expected to demonstrate an improvement by more than a factor four compared to traditional harvesting generators. Intellectual property is also highly anticipated. The training objective of the Fellow Researcher will be to complement and improve his skills in MEMS manufacturing and characterization by attending at formal and informal technical courses and practicing with the resources provided by the hosting institute. The results will be communicated by the Fellow Researcher in conferences and journal papers. A patent application is also envisaged.'

Introduzione (Teaser)

EU-funded scientists developed a micro energy harvesting device operating at very low frequencies and with power densities matching those of lithium batteries operating for one year.

Descrizione progetto (Article)

Vibrational energy harvesting (VEH) with micro-electromechanical systems (MEMS) are helping power maintenance-free and long-lasting wireless electronics such as autonomous sensors. However, vibrations may occur within a narrow frequency range, and energy harvesters may not get enough power out of those frequencies for long enough.

The EU-funded project 'Nonlinear energy harvesting solutions for micro- and nano-technologies' (http://www.esiee.fr/~bassetp/nehstech.html (NEHSTECH)) sought to overcome such limitations with an innovative approach. To widen bandwidth of micro energy harvesters, scientists used elastic stoppers, non-linear springs and bi-stable mechanical oscillators. As piezoelectric and electromagnetic converters are still quite bulky, the project focused on electrostatic vibration harvesters that are more suitable for implementation at MEMS scales.

Scientific work resulted in a silicon MEMS VEH prototype with electrostatic gap-closing combs. Silicon mass bi-stability was controlled by a bias voltage that exerted a softening effect to the effective stiffness of mechanical suspensions. Elastic stoppers served to maintain kinetic energy and increase proof mass and micro-ball velocity during collisions.

Scientists measured mechanical and electrical power spectral densities (PSDs) for different resistive loads and under a variety of realistic vibration inputs (random noise, sinusoidal, impulsive etc.). At very low frequencies, t he MEMS harvester demonstrated a power gain factor of 5 when compared with existing linear MEMS generators with single mass.

The capability of MEMS harvesters to operate at very low frequencies makes them suitable for important applications. These include pacemaker powering from human movements or bridge monitoring from self-sustainable wireless sensor nodes. The project's first prototype was not fully optimised, and further work needs to be done to improve its power performance.