Développement d'un pré-concentrateur miniaturisé en technologie silicium pour la détection de substances chimiques à l'état de traces

International audienceL'objectif principal de cette étude est le développement d'un dispositif de pré-concentration basé sur une technologie de microréacteur en silicium. Les applications visées concernent les systèmes miniaturisés de détection de traces gazeuses, soit en pollution atmosphérique, soit pour la détection d'explosifs. Pour cela, une poudre de carbone est utilisée comme matériau adsorbent, et les dispositifs ont été testés sous benzène. Les composants sont constitués de micro-canaux en silicium obtenus par gravures DRIE. Ils sont équipés de capillaires métalliques et d'un micro-chauffage. Une partie de l'étude porte sur le dépôt par méthode fluidique de la poudre de carbone dans les micro-canaux. Un intérêt particulier de l'étude concerne l'utilisation de silicium poreux pour augmenter la quantité de carbone déposé. Les tests de faisabilité sous benzène permettent de vérifier l'effet de pré-concentration recherché

Effect of agricultural fiber reinforcement on the mechanical properties of a recycled polyethylene plastic composite material

This study determined the effect of certain agricultural fiber reinforcements on the tensile and impact mechanical properties of a recycled polyethylene plastic composite material. The purpose of the study was to provide information on certain mechanical properties of a recycled polyethylene plastic material as part of a coordinated materials application process. A prototype product run of the plastic composite material was done and test specimens were selected from this material. Notch impact, tensile, and flexure tests were conducted on test specimens. Test procedures complied with accepted standards from The American Society For Testing and Materials (ASTM). Tests were conducted on 193 notch impact specimens, 106 tensile test samples, and 13 flexure test specimens. Data collected during these tests were statistically analyzed by standard Analysis of Variance (ANOVA) tests at the 0.05 level of significance. Standard statistical procedures were applied to the data to ascertain if unexpected manufacturing or process variables were encountered. The effects of individual and combined treatments effects were analyzed for significance in regard to the influence these factors had on notch impact, tensile, and flexural strength. A statistically significant (p = 0.05) mean value difference was determined to exist between the effect of different lengths of reinforcement fiber, different volume fraction percentages of fiber reinforcement material, different test temperatures, and different types of fiber reinforcement material. Mean experimental values for each treatment effect were generated. Data were organized in appropriate data tables and graphical presentations

Does Technology Reform Education?

School reform initiatives have been part of public school change for some time. In the past two decades, this author has participated in implementing several educational changes within a public school classroom. Some of these changes have involved learning new teaching strategies, integrating technology into the curriculum, implementing new concepts such as whole language, and participating in workshops to learn about new educational topics. Often these change efforts were embraced by educators as new and innovative ways to help students learn. However, many of these changes were tried and discarded because no ongoing effort was made to incorporate them systematically into the school organization, ongoing support for further training was often absent, and resources to implement changes were not adequate. Within many educational environments these changes were referred to as fads because of their short term effects on the educational system and teaching behaviors

Visual Information Management: A New Skill for Online Course Development

Visual information management refers to the total package of effort that results in successful online delivery of education. It includes the delivery system, student preferences and perceptions, learning and teaching styles, and design factors (Bromham & Oprandi, 2006). Because online courses continue to be an increasingly larger and more influential factor in education, it is important to focus attention on strategies that optimize the outcomes of online education. This article describes some issues for consideration, as well as providing some suggestions for instituting policies and strategies to maximize benefits to students

Gas Sensors on Plastic Foil with Reduced Power Consumption for Wireless Applications

Recently, there is a growing interest in developing so-called "smart" RFID tags for logistic applications. These smart tags incorporate sensing devices to monitor environmental parameters such as humidity and temperature throughout the supply chain. To fulfill these requirements cost-effectively, RFID tags were produced on plastic foil through large scale manufacturing techniques. To benefit from sensing capabilities on these systems, the integration of gas sensors directly produced on plastic foil was explored. Their gas sensing performances were investigated when fabricated on same polymeric substrates than the labels. To be compatible with wireless applications, all sensors were designed to operate in the sub-milliwatt power range. The integration of three different transducers on plastic foil for the detection of different gaseous species was investigated. First, the direct use of the PET or PEN foil as an optical waveguide for the fabrication of a selective colorimetric ammonia gas sensor was carried out. It led to a simplified processing based on additive fabrication techniques compatible with large scale manufacturing. Second, the impact of miniaturization on drop-coated metal-oxide gas sensors when fabricated on polyimide foil on their sensing performances was investigated. They took advantage from the low thermal conductivity of the substrate to reduce the power consumption with a simplified processing. The detection of oxidizing and reducing gases was achieved at low power consumption when pulsing the sensors. Lastly, the benefits brought by the gas absorption in a polyimide foil were exploited with the design of a simple capacitive structure. By operating it in a differential mode with a second functionalized capacitor, the discrimination between low-concentrations of volatile organic compounds and humidity was achieved. The design and fabrication of these sensors were developed with a vision of their future production performed by large scale manufacturing techniques. The gas sensing performances of all three transducers were assessed and revealed sensitivities comparable to standard devices made on silicon. Each sensor was associated with low-power electronics targeting an integration on wireless systems. The concept of a smart gas sensing system was demonstrated with the interfacing of a capacitive humidity sensor on a passive RFID label

Hand-drawn resistors, capacitors, diodes, and circuits for a pressure sensor system on paper

Hand-written fabrication techniques offer new ways of developing customizable, biodegradable and low-cost electronic systems. In this work, a new level of complexity is demonstrated for hand-written electronics by fabricating passive components, circuits and a sensorsystem on paper. The system comprises a pencil-written graphite force-sensitive-resistor, a pencil-drawn RC-filter, a pen-written half-wave rectifier, and a commercial front-end voltage amplifier. The sensor system exhibits a linear response for pressures up to 1.2 kPa, and a sensitivity of 51 mV kPa-1 . Furthermore, the electrical and mechanical performance of the single components and circuits is studied. Diodes fabricated through pen-written deposition of silver and nickel contacts on amorphous Indium-Gallium-Zinc-Oxide coated paper show rectification ratios up to 1:8. Tensile and compressive bending measurements applied to all pencil-written components for radii down to 0.1 mm indicate minor influence of strain. Similar results are obtained for circuits created from these individual components. Diodes and half-wave rectifiers show a stable behavior when bent to a radius of 5 mm. The presented techniques can enable the development of flexible and eco-friendly wearables and sensors for consumer and healthcare applications, and are an effective way for school-pupils to explore the world of electronics

Inkjet Printed Conductive Polymer Electrodes for AC Electroosmosis

Standalone integrated microfuidic systems require pumping elements. Electro-osmosis (EO) is an e"ective method of actuating liquids [1,2]. ACEO exploits much lower potentials and, by using alternating fields, overcomes the issues of electrolysis and gas generatio

ULTRA-LOW POWER METAL-OXIDE GAS SENSOR ON PLASTIC FOIL

ABSTRACT We report on the design and fabrication of ultra-low power metal-oxide (MOX) gas sensors on plastic foils envisioning their fabrication at large scale and low cost. A complete sensor solution is presented including its packaging at the foil level and the driving/readout circuitry. The latter allowed the sensor to operate in pulsed temperature mode to reduce the power consumption in the sub-mW range. Gas measurements under CO, CH 4 and NO 2 have proven the proper operation of the sensor. These devices are being developed targeting wireless applications