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We report a hierarchical hexahedral geometry of interdigited-comb MEMS capacitor for electrostatic vibration energy harvesters (e-VEHs), where the air damping effect is greatly reduced while the capacitance variation remains important. Based on the same frequency up-conversion structure as in our previous design, the device with the new electrode geometry reaches a larger bandwidth (10∼180 Hz) in...
We report a 1-cm2 ultra-wideband MEMS electrostatic vibration energy harvester (e-VEH) that combines a frequency-up conversion system with a vertical electret layer obtained by corona discharge. At 2.0 grms, the device can harvest more than 1 μW from 59 to 148 Hz, and more than 0.5 μW from 14 to 152 Hz. Thanks to this new device, we demonstrate the self-starting power supply of an energy autonomous...
This paper presents an explanation of the dynamic formation of black silicon (BSi) during deep reactive ion etching (DRIE) processes which has been confirmed by both experimental data with cryogenic DRIE and computational modeling. The model described the strong dependence of the substrate topography on the etching parameters and its evolution with process time. It shows the importance of the self-shadowing...
This paper reports on the drastic impact of the electromechanical coupling on the operating mode of a MEMS electrostatic Vibration Energy Harvester (e-VEH). A similar behavioral pattern was observed for two different conditioning circuits, which biased the e-VEH: one based on a classical charge pump circuit and one based on the Bennet doubler. The result of this study mitigates the commonplace opinion...
We present an accurate 3D reconstruction method for silicon micro/nanostructures with high aspect ratio, that was developed and implemented using a dual beam (Focused ion beam and scanning electron microscopy (FIB-SEM)) tomography. Black Silicon (BSi) samples were processed by alternating steps of FIB etching and SEM imaging, that allow obtaining sequential cross section images of the sample, including...
In the present paper, the reduced spectral reflectance properties of silicon micro/nanostructures are studied. In the aim of implementing a predictive reflectance simulation model based on surface topography, an alternative design method of an equivalent unit cell is proposed, where the dimensions and shape are determined based on statistical parameters of the sample topography. A good concordance...
We present a new MEMS electrostatic vibration harvester that exploits mechanical frequency amplification by multiple-mass impacts in combination with elastic stoppers. When the system is shaken at low frequency (10–60 Hz) a tungsten micro-ball impacts within the oscillating proof mass of the harvester transferring kinetic energy to the gap-closing comb transducer which in turns resonates at its natural...
We report on the first electrostatic Vibration Energy Harvester (e-VEH) using a voltage-controlled multi-stable energy potential in order to harvest energy from stochastic vibration noise. We show that an optimized pre-charge voltage on the electromechanical transducer associated with a displacement constraint of the movable mass leads to a triple-well potential. This condition enhances the energy...
This paper deals with a fully batch-processed MEMS electrostatic Vibration Energy Harvster (e-VEH) having a half-power frequency bandwidth of more than 30 % thanks to the combination of electrostatic and mechanical non-linearities. The electromechanical transducer is made of bulk-silicon gap-closing interdigited combs with a trapezoidal cross section. Up to 2.2 μW have been harvested at atmospheric...
This paper reports a novel vibration energy harvester (VEH) design consisting of a double-mass contactless frequency-up converter with buckled clamped-clamped beams. The vibration to electricity conversion is performed through a MEMS silicon micro electrostatic vibration energy harvester (e-VEH) based on in-plane gap-closing interdigitated combs. Despite the fact that the converter itself is designed...
In this work, a nonlinear vibration energy harvester consisting of a buckled beam and an electromagnetic transducer is proposed. An advantage of this device is that there is no need of permanent magnets to create the bistable potential. Theoretical modeling and experimental investigations on a prototype are presented. The prototype demonstrates a peak power of 2.96 mW at resonance of 52 Hz under 0...
In this paper we study the impact of the three-dimensional geometry of a micro/nanostructured silicon surface on its reflectivity under incident electromagnetic (EM) illumination. We simulate the optical reflectance of 3D micro/nano silicon cones of different dimensions. Based on the favorable simulation results, maskless textured silicon, called “black silicon” is processed by deep reactive ion etching...
This paper reports on an investigation of dynamic behavior of an electrostatic Vibration Energy Harvester (e-VEH) which uses gap-closing capacitive transducers and operates in a constant-charge mode. This work provides a deep insight into stability issues of a e-VEH investigating four dynamic modes, among which only one corresponds to a regular, stable and desirable operation mode needed for the energy...
This paper reports on a new approach for the analysis and design of vibration-to-electricity converters [vibration energy harvesters (VEHs)] operating in the mode of strong electromechanical coupling. The underlying concept is that the mechanical impedance is defined for a nonlinear electromechanical transducer on the basis of an equivalence between electrical and mechanical systems. This paper demonstrates...
In this paper we study the enhanced absorption properties of micro/nano structured silicon surface under incident electromagnetic (EM) illumination and then its capacity to convert light to heat. We then simulate the optical reflectance of the 3D micro/nano silicon cones of different dimensions. Equipped with the favorable simulation results we fabricate black silicon with excellent anti-reflectivity...
In this paper, we study the enhancement of silicon absorbing properties while microstructuring its surface with cones of variable size and spacing. We simulate the optical reflectance of the structures with spikes of different dimensions. Then random maskless textured silicon, called “black silicon” is processed by reactive ion etching (RIE) under cryogenic temperatures. Using this process, three...
In this paper, we propose a novel approach to on-chip cooling by thermionic emission by using vertical superlattices fabricated directly into the silicon wafer as opposed to conventional planar additive deposition methods used by most other groups. The advantages of this method are (i) significantly lower fabrication costs and (ii) adequate number of superlattice layers translating to higher efficiency...
In this paper, we propose a novel approach to on-chip cooling by thermionic emission by using vertical superlattices fabricated directly into the silicon wafer as opposed to conventional planar additive deposition methods used by most other groups. The advantages of this method are (i) significantly lower fabrication costs and (ii) adequate number of superlattice layers translating to higher efficiency...
This paper studies the vibration energy harvesting (VEH) capabilities for one electrostatic mechanism: the out-of-plane gap-closing (OPGC) converter. The goal is to maximize the output energy harvested from a MEMS device while preventing the integrity of the conditioning circuit. The originality of this work lies in the optimization taking into account both electrical and mechanical aspects and studying...
This paper presents a functional design and modeling of smart conditioning circuit of a vibrational energy harvester based on electrostatic transducer. Two original features are added to the basic configuration previously published (whose model we presented on BMAS2007 conference). Firstly, we developed an auto-calibration block which allows the new harvester to adapt dynamically to the varying environment...
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