Un capteur électrochimique pour la mesure locale d'un champ de vitesse tridimensionnel. Réalisation par des techniques microélectroniques et application à l'étude de l'écoulement dans une cellule à jet immergé

In this work, we show that the electrochemical method makes it possible to obtain the three velocity components of a fluid in the vicinity of the wall. This requires the use of a trisegmente sensor. This sensor is made up of a monodisk divided into three circular sectors at 120. This sensor is realized by the techniques of microelectronics. The different stages of the process for realising the sensor on a flexible support, and which involve many techniques such as photolithography, chemical or electrochemical deposits, chemical treatments or plasmas, are detailed. In order to study the behaviour of this sensor, we developed the theory on three-dimensional probes in a three-dimensional flow at stagnation point from the calculations for a flow with stagnation at symmetry plane. The last part of this work contains an experimental study where the possibilities of the trisegmente sensor are exploited to analyse the characteristics of flow within a jet cell which has a zone of stagnation and which allows to determine the responses of the sensor depending on changes in speed and direction of flow.Dans ce travail, on montre que la méthode électrochimique permet d'obtenir les trois composantes de vitesse d'un fluide au voisinage de la paroi. Cela nécessite l'utilisation d'un capteur trisegmenté. Ce capteur est constitué d'un monodisque divisé en trois secteurs circulaires à 120. Ce capteur est réalisé par les techniques de la microélectronique. Les différentes étapes du procédé pour réaliser le capteur sur support souple, et qui font appel à de nombreuses techniques comme la photolithographie, les dépôts chimiques ou électrochimiques, les traitements chimiques ou les plasmas, sont détaillées. Pour pouvoir étudier le comportement de ce capteur, nous avons développé la théorie sur les sondes trisegmentées dans un écoulement tridimensionnel à point de stagnation à partir des calculs pour un écoulement avec stagnation à plan de symétrie. La dernière partie de ce travail contient une étude expérimentale où les possibilités du capteur trisegmenté sont exploitées pour analyser les caractéristiques de l’écoulement au sein d'une cellule à jet qui possède une zone de stagnation et qui permet de déterminer les réponses du capteur en fonction des variations de la vitesse et de la direction de l’écoulement

Integrated Millimeter-Wave Silicon Micromachined Filters

This paper describes the design and the fabrication of a new type of millimeter-wave micromachined band pass filters, using silicon waveguides. The main interest of these components is their ability to be integrated along with other MMICs using flip chip bonding techniques. The micromachining fabrication technique allows to maintain very good fabrication tolerances, while the resulting filters are very compact. The design methodology is presented along with two examples of two and four pole filters at 42 GHz. applied to these filters and at last simulation results on 2 and 4 pole bandpass filters

Frequency filters for hyperfrequency applications in high speed and inter-satellite communications, anti-collision radars and radiometry

Egalement publié comme: Frequency filter and its manufacturing process US2006125579 (A1) 15/06/2006 Egalement publié comme: Frequency filter and its method of réalization EP1617503 (A1) 18/01/200

MEMS with an embedded fluidic microchannel for sensitive weighing of liquid samples

International audienceThis paper reports hollow MEMS plate oscillators for the characterization of liquid samples, with a one-fold improvement in both Q-factor and Allan deviation compared to previous alike structures, and fluidic constriction larger than 1μm. These new characteristics make the devices amenable for the first time to liquid weighing with a 100 Hz.(g.L-1)-1 sensitivity and a few g.L-1 detection floor

A robust ALD-protected silicon-based hybrid photoelectrode for hydrogen evolution under aqueous conditions

International audienceHydrogen production through direct sunlight-driven water splitting in photo-electrochemical cells (PECs) is a promising solution for energy sourcing. PECs need to fulfill three criteria: sustainability, cost-effectiveness and stability. Here we report an efficient and stable photocathode platform for H2 evolution based on Earth-abundant elements. A p-type silicon surface was protected by atomic layer deposition (ALD) with a 15 nm TiO2 layer, on top of which a 300 nm mesoporous TiO2 layer was spin-coated. The cobalt diimine-dioxime molecular catalyst was covalently grafted onto TiO2 through phosphonate anchors and an additional 0.2 nm ALD-TiO2 layer was applied for stabilization. This assembly catalyzes water reduction into H2 in phosphate buffer (pH 7) with an onset potential of +0.47 V vs. RHE. The resulting current density is -1.3 ± 0.1 mA cm-2 at 0 V vs. RHE under AM 1.5 solar irradiation, corresponding to a turnover number of 260 per hour of operation and a turnover frequency of 0.071 s-1

New sectorized implantable microelectrode fabrication, packaging and ageing for neural sensing and stimulation

International audienceThis paper describes the fabrication and the packaging of a flexible parylene-based multi-contact electrode embedded in a silicone-based cuff. This type of electrode is well suited for peripheral nerve recording and offers improved spatial selectivity. We conducted mechanical and electrical tests for assessing the reliability by using an accelerated lifetime protocol. Test structures made with platinum sandwiched with parylene C were designed. The accelerated lifetime soaking tests in phosphate buffered saline (PBS) solution at 67 degrees C showed a longer life time (approximatively 4.5 years) with a dehydration bake introduction in the process flow and a parylene thickness increase. A specific test bench was developed for the mechanical cycling and for evaluating the mechanical robustness of the thin film devices

New sectorized implantable microelectrode fabrication, packaging and ageing for neural sensing and stimulation

International audienceThis paper describes the fabrication and the packaging of a flexible parylene-based multi-contact electrode embedded in a silicone-based cuff. This type of electrode is well suited for peripheral nerve recording and offers improved spatial selectivity. We conducted mechanical and electrical tests for assessing the reliability by using an accelerated lifetime protocol. Test structures made with platinum sandwiched with parylene C were designed. The accelerated lifetime soaking tests in phosphate buffered saline (PBS) solution at 67 degrees C showed a longer life time (approximatively 4.5 years) with a dehydration bake introduction in the process flow and a parylene thickness increase. A specific test bench was developed for the mechanical cycling and for evaluating the mechanical robustness of the thin film devices