Philippe Basset

A batch-fabricated and electret-free silicon electrostatic vibration energy harvester

This paper presents a novel silicon-based and batch-processed MEMS electrostatic transducer for harvesting and converting the energy of vibrations into electrical energy without using an electret layer. Effective conversion from the mechanical-to-electric domains of 61 nW on a 60 MΩ resistive load, under a vibration level of 0.25 g at 250 Hz, has been demonstrated. Rigorous analysis of the efficiency of the harvester is presented, covering issues related with mechanical and electrical operation. Various schemes for the conditioning electronics are discussed and the harvested power measurements using a dc/dc converter are explained in detail. The paper concludes with a comparison with previous electrostatic transducers based on a new simple factor of merit.

Electrostatic vibration energy harvester with combined effect of electrical nonlinearities and mechanical impact

This paper presents an advanced study including the design, characterization and theoretical analysis of a capacitive vibration energy harvester. Although based on a resonant electromechanical device, it is intended for operation in a wide frequency band due to the combination of stop-end effects and a strong biasing electrical field. The electrostatic transducer has an interdigited comb geometry with in-plane motion, and is obtained through a simple batch process using two masks. A continuous conditioning circuit is used for the characterization of the transducer. A nonlinear model of the coupled system ‘transduce-conditioning circuit’ is presented and analyzed employing two different semi-analytical techniques together with precise numerical modelling. Experimental results are in good agreement with results obtained from numerical modelling. With the 1 g amplitude of harmonic external acceleration at atmospheric pressure, the system transducer-conditioning circuit has a half-power bandwidth of more than 30% and converts more than 2 μ Wo f the power of input mechanical vibrations over the range of 140 and 160 Hz. The harvester has also been characterized under stochastic noise-like input vibrations.

A Silicon MEMS DC/DC Converter for Autonomous Vibration-to-Electrical-Energy Scavenger

This letter deals with an innovative design for a silicon MEMS DC/DC converter, to be used in autonomous mechanical-energy scavengers, based on electrostatic transduction. The device is made of bulk silicon and is fabricated using a batch process. It is 27 mm3 in volume and resonates at 250 Hz. We demonstrate a net vibration-to-electricity power conversion of between 60 and 100 nW in autonomous mode, i.e., without injecting and introducing new charges from an external power supply. We have compared the measurements with the results of a mixed VHDL-AMS/ELDO modeling experiment, and the agreement between these two experiments is better than 3%.

A large stepwise motion electrostatic actuator for a wireless microrobot

An original large stepwise motion electrostatic microactuator for a wireless microrobot using a distributed Ciliary Motion System (CMS) [1] is presented. Coventorware/sup TM/ cosolver simulations have shown x-displacement of 240 nm for one actuation step. Design of the antennas for inductive powering has been optimized in order to maximize the energy transfer. 24 /spl mu/m gold electroplated hollow micro-coils have been fabricated on an epoxy substrate as receiver antennas. Q-factor of 29 at 13.56 MHz and induced voltage up to 100 V on a 1 k/spl Omega/ load has been obtained. Remote actuation of an array of actuators supporting a 0.25 mm/sup 2//380 /spl mu/m-thick piece of silicon has been successfully demonstrated with a pull-in voltage of 80 V.

On the optical and morphological properties of microstructured Black Silicon obtained by cryogenic-enhanced plasma reactive ion etching

Motivated by the need for obtaining low reflectivity silicon surfaces, we report on (sub-) micro-texturing of silicon using a high throughput fabrication process involving SF6/O2 reactive ion etching at cryogenic temperatures, leading to Black Silicon (BS). The corresponding high aspect ratio conical spikes of the microstructured surface give rise to multiple reflections and hence, enhanced absorption under electromagnetic radiation. Aiming a better understanding of this mechanism, we performed a systematic study by varying several plasma process parameters: O2/SF6 gas flow rate ratio, silicon temperature, bias voltage, and etching time. We determined the process window which leads to BS formation and we studied the influence of the process parameters on the surface morphology of the obtained BS samples, through analysis of scanning electron microscopy images. The measured optical reflectance of BS is in the order of 1% in the visible and near infrared ranges (400–950 nm). We noticed that the lowest refle...

Electret-Free Micromachined Silicon Electrostatic Vibration Energy Harvester With the Bennet’s Doubler as Conditioning Circuit

This letter presents for the first time experiments combining a previously reported microelectromechanical system electrostatic vibration energy harvester (e-VEH) and the Bennets doubler circuit. A self-limiting effect on the harvested power, which was not reported before on macroscopic e-VEHs, has been observed. This effect is due to the nonlinear dynamics of the system and to the self-increase of the electromechanical damping that is typical for e-VEHs. With a few volts of initial precharge, the Bennets doubler progressively increases the voltage across the transducers terminals up to 23 V, where saturation occurs. A power of 2.3 μW is available for a load, when the harvester is excited by 1.5 g at 150 Hz of external acceleration.

A General Analytical Tool for the Design of Vibration Energy Harvesters (VEHs) Based on the Mechanical Impedance Concept

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 how the mechanical impedance of the transducer depends not only on the geometry and the nature of the electromechanical transducer itself but also on the topology and on the operation mode of the conditioning circuit. The analysis is developed for resonant harvesters and is based on the first-harmonic method. It is applied to three electrostatic harvesters using an identical conditioning circuit but employing transducers with different geometries. For each of the three configurations, the mechanical impedance of the transducer is calculated and then used to determine the optimal electrical operation mode of the conditioning circuit, allowing a desired amplitude of the mobile-mass vibration to be obtained. This paper highlights how the parameters of the conditioning circuit and of the transducer impact the transducers mechanical impedance, directly affecting the impedance matching between the energy source (resonator) and the transducer. This technique permits the design of highly efficient VEHs whatever the means of transduction.

Complete System for Wireless Powering and Remote Control of Electrostatic Actuators by Inductive Coupling

This paper proposes a successful asynchronous remote powering and control of electrostatic microactuators, organized in two distributed micro motion systems (DMMS) with the aim of realizing a wireless microrobot. Remote powering of the integrated circuit (IC) and the microelectromechanical systems (MEMS) components is obtained by inductive coupling at 13.56 MHz, and the digital transmission is created by modulating the carrier amplitude by 25%. The system includes a high-voltage controller IC. It provides a link between the power and data on the receiver antenna on one side, and the actuators of the microrobot on the other. The micromachined antenna is designed to optimize the inductive coupling. The main IC building blocks, such as the received signal rectifier/amplifier, the integrated digital processing and the DMMS actuation voltage generation are given in detail. The demonstrator has successfully achieved the remote control and asynchronous operation under 100 V of two arrays of 1700 electrostatic actuators, having a capacity of 2 nF each

Thermal conductivity and thermal boundary resistance of nanostructures

AbstractWe present a fabrication process of low-cost superlattices and simulations related with the heat dissipation on them. The influence of the interfacial roughness on the thermal conductivity of semiconductor/semiconductor superlattices was studied by equilibrium and non-equilibrium molecular dynamics and on the Kapitza resistance of superlattices interfaces by equilibrium molecular dynamics. The non-equilibrium method was the tool used for the prediction of the Kapitza resistance for a binary semiconductor/metal system. Physical explanations are provided for rationalizing the simulation results.PACS68.65.Cd, 66.70.Df, 81.16.-c, 65.80.-g, 31.12.xv

A nonlinear MEMS electrostatic kinetic energy harvester for human-powered biomedical devices

This article proposes a silicon-based electrostatic kinetic energy harvester with an ultra-wide operating frequency bandwidth from 1 Hz to 160 Hz. This large bandwidth is obtained, thanks to a miniature tungsten ball impacting with a movable proof mass of silicon. The motion of the silicon proof mass is confined by nonlinear elastic stoppers on the fixed part standing against two protrusions of the proof mass. The electrostatic transducer is made of interdigited-combs with a gap-closing variable capacitance that includes vertical electrets obtained by corona discharge. Below 10 Hz, the e-KEH offers 30.6 nJ per mechanical oscillation at 2 grms, which makes it suitable for powering biomedical devices from human motion. Above 10 Hz and up to 162 Hz, the harvested power is more than 0.5 μW with a maximum of 4.5 μW at 160 Hz. The highest power of 6.6 μW is obtained without the ball at 432 Hz, in accordance with a power density of 142 μW/cm3. We also demonstrate the charging of a 47-μF capacitor to 3.5 V used to power a battery-less wireless temperature sensor node.