Showing papers by "Elie Lefeuvre published in 2012"

Energy harvester device for autonomous intracorporeal capsule

Abstract: An energy harvester device for an autonomous intracorporeal leadless capsule comprises a surface formed on the outside of the body of the capsule that is deformable under the effect of pressure variations in the environment surrounding the capsule A first capacitor electrode coupling to the deformable surface with the interposition of a damping element forming high-pass filter with respect to pressure variations in the surrounding medium, and a second capacitor electrode mounting on a support connected to the body The movement of the deformable surface produces a modification of surfaces in vis-a-vis of the two electrodes and/or of the dielectric gap which separates them, with a variation of the capacity of said capacitor The capacitor is preloaded when its capacity is maximum, and unloaded by transferring energy into storage circuit when this capacity decreases from a reduction in surfaces in vis-a-vis and/or of an increase of the dielectric gap

An active piezoelectric energy extraction method for pressure energy harvesting

Abstract: This paper presents an energy harvesting technique to power autonomous systems and more particularly active implantable medical devices. We employ a piezoelectric diaphragm placed in a fluidic environment such as blood subjected to very low frequency (2 Hz) pressure variations that is deflected in a quasi-static manner and transduces mechanical energy into electrical energy. In order to maximize energy generation and to get the most out of a given piezoelectric device, we propose to apply an optimized method to extract the piezoelectrically generated charge through the application of a controlled voltage. We believe that this method could be one of the improvement levers to achieve self-powered miniaturized implants. An analytical model is presented and shows that within its validity domain, the extracted energy is proportional to the desired applied voltage. Taking power electronics losses into account can yield a theoretical increase in the extracted energy of several thousand per cent. Experimental measurements in a pressure chamber have been carried out whose results corroborate the proposed model. For the tested setup, the application of a 10 V peak amplitude square-wave voltage increased the extracted energy by a factor of nine compared to a classical rectifier-based energy harvesting method.

Microstructured silicon membrane with soft suspension beams for a high performance MEMS microspeaker

Abstract: This study presents a novel approach to MEMS microspeakers design aiming to tackle two main drawbacks of conventional microspeakers: their poor sound quality and their weak efficiency. For this purpose, an acoustic emissive surface based on a very light but very stiff structured silicon membrane was designed and microfabricated. This architecture, for which the membrane undesirable vibration modes were reduced to only three within the microspeaker bandwidth, is promising to let the microspeaker produce high sound quality from 300 Hz to 20 kHz. This silicon membrane is suspended by a whole set of silicon springs designed to enable out-of-plane displacements as large as 300 μm. Different geometries of springs were considered and the material maximum stress was analyzed in each case by finite element modeling. The proposed structure promises an efficiency of 10−4, that is to say ten times higher than that of conventional microspeakers.

Energy recovery device for autonomous intracorporeal capsule

Abstract: The capsule has an energy recovery transducer comprising a capacitor electrode in form of comb coupled to a movable actuation member that has a deformable element (42) deformed in response to effect of pressure variations in a medium. The electrode and another capacitor electrode have surfaces separated by dielectric gap to define a capacitor. An energy storage and management module is powered by the transducer based on a reduction in the surfaces and/or an increase of the gap. The element is coupled to the comb by a mechanical high-pass filter (68) for pressure variations in the medium.

Electrodynamic MEMS: Application to Mobile Phone Loudspeakers

Abstract: This paper presents an electrodynamic MEMS for mobile phone loudspeaker applications. The whole structure of the loudspeaker is a new conception to reach higher performances than in existing devices: a linear behavior to ensure a high acoustic fidelity and a high efficiency to increase the power autonomy. So, the motor is ironless, constituted of permanent magnet only. Several electrodynamic structures are presented and studied with analytical formulations of the magnetic field. The emissive part is a plane silicon surface, very rigid and light, the suspension is achieved by silicon beams, which are not sensitive to mechanical fatigue, the electroplated copper coil is thick and requires a specialist technique to be deposited. The moving part displacements are in a range far larger than in existing MEMS (600 μ m). The trends for dimensioning the structure are investigated and prototypes realized and tested, with NdFeB ring magnets. As a result, the 70 dB SPL at 10 cm bandwidth reaches up to 100 kHz, and the behavior is particularly linear.

Silicon-based MEMS microspeaker with large stroke electromagnetic actuation

Abstract: This paper reports on the design, manufacturing process and characterization of a new silicon-based microspeaker. The objectives of this work were to get better sound quality, higher acoustic power and higher efficiency than that of conventional microspeakers. An optimized microstructure for the silicon mobile part enabled the sound radiator to be extremely light and rigid. The suspension was designed to enable large out-of-plane displacements of the radiator. The radiator was actuated by an electromagnetic motor composed of a fixed permanent magnet and a planar coil located on top of the silicon membrane. The electromagnetic structure was designed and optimized regarding efficiency and linearity. The obtained upward and downward motion, close to a perfect piston movement, was very beneficial for the sound quality. Electro-mechano-acoustic characterization showed that the suspension can stand out-of-plane displacement higher than 1200 µm. For an injected power of 0.5 W, the microspeaker was capable to generate a sound pressure level of 80 dB at 10 cm from 330 Hz up to 20 kHz frequency. The efficiency reached 3×10−5, that is to say three times higher than typical efficiency of conventional microspeakers. Moreover, very low intermodulation effect was detected. This contributed to the remarkable sound quality of this silicon-based microspeaker.

Potential of MEMS technologies for manufacturing of high-fidelity microspeakers

Abstract: The use of microspeakers has drastically grown over the past few years in reason of the important increase of mobile electronics devices having sound reproduction functions. Consumer electronics devices such as mobile phones, tablets or camcorders are the most representative exemples of everyday used devices with embedded microspeakers. Since 2009, this market exceeds one billion microspeakers per year. However, in parallel to the sales increase, the performances of these small-size transducers have been only very little improved in terms of sound quality, efficiency and power density over the last decade. Several reasons can explain such stagnation, such as the limits of conventional manufacturing techniques, or the focus put on selling points other than sound reproduction. The proposal made here is to take advantage of Microsystems technologies for improving microspeaker's performances. Indeed, such a technological leap appears as a very promising way to overcome the major shortcomings of micro speakers made using conventional technologies. This paper illustrates, in the case of a silicon microspeaker, the gains that can be expected from MEMS technologies. The design and the microfabrication process of the device will be fully detailed. Experimental acoustic chacacteristics will be compared to that of conventional microspeakers of same size and power range.

DC and Pulsed electrodeposition of SmCo thin films

Abstract: Thin films of SmCo have been produced by electrodeposition in a Hull cell from aqueous solution. The composition of the films is dependant on the supplying mode - continuous or pulsed current. The influence of the cobalt concentration in the electrolytic solution, as well as the presence of a supporting electrolyte has been also studied. A systematic study allowed determining several operating points leading to the functional compositions of 11% or 16% Sm/(Sm+Co) ratio.

Dispositif de récupération d'énergie pour capsule intracorporelle autonome

Abstract: Le dispositif recuperation d'energie comporte une surface deformable (42) formee sur l'exterieur du corps (40) de la capsule et apte a etre deformee alternativement dans un sens et dans l'autre sous l'effet des variations de pression dans le milieu environnant la capsule. Une premiere electrode de condensateur est couplee a la surface deformable avec interposition d'un element amortisseur mecanique (68) formant filtre passe-haut a l'egard des variations de pression dans le milieu environnant, et une seconde electrode de condensateur est montee sur un support (56) relie au corps. Le mouvement de la surface deformable produit une modification correlative des surfaces en vis-a-vis des deux electrodes et/ou de l'intervalle dielectrique qui les separe, avec variation correlative de la capacite dudit condensateur. Le condensateur est precharge lorsque sa capacite est maximale, il est decharge en transferant son energie vers des moyens de stockage lorsque diminue cette capacite sous l'effet d'une diminution des surfaces en vis-a-vis et/ou d'une augmentation de l'intervalle dielectrique.