This research concentrates on the sensitivity of a tin dioxide-based gas sensor semiconductor with respect to hydrogen fluoride in the atmosphere. This paper is focused on the development of a separation micro-system, which will be positioned in front of the gas sensor, for the potential use in a complex atmosphere. This study deals with the use of traditional techniques of micro-machining on silicon substrates to manufacture chromatographic micro-columns. The manufacture of the micro-channels and formulation of the stationary phase are discussed. Infrared spectroscopy allows following the evolution of the stationary phase with respect to time. We evaluate the thickness of the stationary phase deposited on the GC micro-channel's internal walls close to the micrometer. A solvent extraction test was performed in order to illustrate the use of the device considered.

Micro-machined Ultrasonic Transducer (MUT) structures are periodic, associating numerous elementary actuators. These transducers can be accurately analysed or even designed using mixed finite element analysis/boundary element methods (FEA/MEM). In this work, we report on the design and test of a cMUT structure based on a thin silicon membrane shaped in order to comply our modelling assumptions.

This work demonstrates the relevance of a Love-wave device dedicated to the detection of low concentrations of anhydride hexafluorhydric (HF) (CHF<3ppm). Improvements are demonstrated compared to previous versions of the detection system for which surface transverse wave (STW) devices were used. We also have tested a coating, specifically sensitive to HF, deposited atop a STW resonator, operating along the same Love-wave principle and exhibiting improved sensitivity compared to STW sensors. Time-life and sensitivity of each device are reported and discussed. Finally, a surface analysis has been performed to try and explain the actual effect of HF on the sensor surface.

Introduction. - The effects of a passive warm-up, by exposure to a hot thermal environment, on standing rifle-shooting performance were analysed.Subjects and method. - The cutaneous mean temperature and shooting performance of 6 high level shooters was measured under 3 different thermal exposure conditions.Results. - We find that a passive exposure to a 37 degreesC temperature enhances cutaneous body temperature. Only the condition where subjects were exposed to a 37 degreesC temperature during the passive warm-up enhances the following rifle performance during the shooting set at 20 degreesC, compared to control conditions, where passive warm-up and shooting set were conducted either at 20 or 37 degreesC (605.5 +/- 6.7 points vs respectively 600.8 +/- 6.5 and 596.6 +/- 7.3).Discussion and conclusion. - Our results provide evidences of the benefits of a passive warm-up in rifle shooting, a sport where the consequences of a physiological activation seem to be deleterious for performance. Coaches should make shooters aware of the benefits provided by such method of warm-up. (C) 2003 Elsevier SAS. Tous droits reserves.

This paper describes an interferometric pressure sensor designed to work as a remote sensor in a coherence modulation scheme, allowing a linear phase read-out of the signal. The sensor is realized from a silicon nitride waveguide Mach-Zehnder integrated on a (100) silicon substrate, and includes a micromachined membrane below a branch of the Mach-Zehnder. The characterization is achieved by a spectral analysis and shows a nonlinear relationship between the static pressure applied to the membrane and the phase variation thus obtained, The analytical description takes into account the induced deflection of the membrane and the resulting mechanical elongation of the waveguide.

We present a simple two-step etching process based on anisotropic wet etching of (100) silicon. As one example a system of three seismic masses on one chip has been fabricated. All three masses are symmetrically suspended by four high aspect ratio beams. The highly symmetrical design minimizes mechanical cross-sensitivities. Moreover, the three devices exhibit almost perfect rectangular alignment due to the orientation along the directions of the silicon crystal. Besides experimental results, design rules for the photolithography-masks are presented.

A study devoted to the design and fabrication of microgrippers using the LIGA technique is described in this paper. The design method is presented and validated by the use of finite-element analysis. Technological topics are detailed to illustrate the fabrication process. Also, experimental data concerning the mechanical behaviour of one of the microgrippers are reported. These data are used to improve the previous finite-element analysis. Finally, a comparison between experiments and theoretical predictions is discussed.

In this paper, we present a silicon bulk-microfabrication method which helps to overcome simultaneously several limitations of multi-axis micro-accelerometers. The method demonstrates an orginal solution to the building of a symmetrical structure by using double-side wet etching. This is a low-cost alternative to existing techniques for the fabrication of highly-symmetrical, single crystal silicon structures. The proposed approach provides low mechanical cross-sensitivities as well as the possibility of a batch fabrication process of the whole three-dimensional device without loss of accuracy due to assembly operation.For the fabrication of thin suspended beams with vertical sidewalls, a non-conventional alignment of +/-45 degrees from the [110] wafer flat was used. This alignment allows one to fabricate two perpendicular devices on one wafer in the same etching step. The etching was performed with a simple standard wet etching process in a KOH solution.A number of structures were fabricated to demonstrate the feasibility of this method. Aspect ratios (beam height over beam thickness) of over 35 were easily achieved. Undercut directions were determined and design rules for the mask layout were established. To describe the mechanical behaviour of the fabricated structure, an analytical model was implemented and a finite-element simulation was performed. First measurements of the seismic mass displacement were performed with an optical comparator, and they agree with theoretically obtained results. The new design offers the possibility of a two-axis accelerometer system on one wafer, consisting of two sensor elements rotated by 90 degrees. A three-axis monolithic accelerometer system with intrinsic perpendicular alignment due to the rectangular symmetry of the (100) planes can be realized, by including a third sensor element sensitive to vertical accelerations.

We have studied a pressure and a gravimetric sensor using an AlN film over a silicon membrane. The membrane is micromachine using both anisotropic and isotropic chemical etching. The AlN thin film is deposited by the sputtering method. Elastic waves are generated and detected through interdigital transducers (IDTs) calculated at the frequency of 90 MHz for the S0 Lamb-wave mode. The behaviour of such a sensor is presented. We have analysed and experimentally tested the pressure and have calculated the gravimetric sensitivity. By using the opposite temperature behaviours of silicon and AlN, a satisfactory temperature compensation is achieved. Results obtained from such experiments show sensitivities that agree with theoretical sensitivities provided by a theoretical model which includes the effect of the mass loading of the deposited thin-layer material.

This paper is devoted to the description of a low cost microfabrication process for the realization of deep etch X-ray lithography (DEXRL) masks. These masks are composed of a 15 mu m thick silicon membrane supporting gold absorbers which are typically 12 to 16 mu m thick. The resolution of such masks is limited to 2-4 mu m, but they allow irradiation up to 2 mm of polymethylmethacrylate (PMMA) by using hard X-ray synchrotron radiation. Theoretical results about dosimetric parameters for the PMMA irradiation are presented. Results obtained with these masks are also given. The purpose of this study is the realization of low cost micromechanical components using the LIGA technique.

In this paper, the fabrication of a three-dimensional (3D) silicon linear microactuator is described. This actuator is realized by anisotropic chemical etching of a (110)-oriented silicon wafer. The silicon monolithic structure of the microactuator comprises a fixed part bonded onto a glass substrate and a movable part suspended from two elastic beams. The displacement of the movable part is consequently frictionless, driven by electrostatic forces. We present the steps of the etching process and initial results concerning mechanical and electrostatic tests. Finally, some projected applications are discussed.

The fabrication of a 3D silicon linear microactuator is presented. This actuator is realized by anisotropic chemical etching of a (110) oriented silicon wafer. The silicon monolithic structure of the microactuator is constituted by a fixed part bonded on a glass substrate and a movable part suspended by two elastic beams. The displacement of the movable part is consequently frictionless and is obtained by electrostatic forces. Some mechanical and electrostatic tests are presented. Moreover, with the aim of using this device for microscopy applications, some results have been achieved concerning the isotropic etching of tips on a (110) oriented silicon wafer. It would therefore be possible to integrate a tip onto a movable part for effective application in atomic force or scanning tunneling microscopy.

LIGA technique has proved to be a powerful tool for micro-fabrication mass production. French laboratories (LURE, L2M, LPMO) gathered to introduce this new technology at LURE facilities. In this paper are described the different steps of the deep etch lithography process including mask realization and first pseudo-tridimensional resist structures are shown.

Among sensors using a thin membrane covered with a piezoelectric layer, we focused on the study of a pressure sensor using an AlN film over a silicon membrane. The membrane was micromachined using both anisotropic and isotropic chemical etchings. The AlN thin film was deposited by a sputtering method with very good stochiometric results. Elastic waves were generated and detected through IDT transducers calculated at a frequency of 88 MHz for the SO Lamb wave mode. We studied the velocity and the electromechanical coupling factor of the first symmetric and antisymmetric Lamb modes according to the thickness of the piezoelectric layer. The pressure and the temperature behavior of such a sensor using the SO Lamb mode are presented. We have analysed the pressure sensitivity and we propose some solutions to obtain a well temperature compensated structure. Especially, we were thinking to achieve a self-compensated structure by using the opposite temperature behavior of silicon and AlN