SENSORS, 2002 IEEE

A model of a miniaturised NDIR (Non Dispersive Infrared) gas analysis system, aiming to predict the final system specifications, is presented. It comprises the different elements of the NDIR detector, including a surface micromachined Fabry-Perot tuneable filter. These models have been used to estimate the response of the NDIR system to different gas mixtures. Multivariate regression methods like Partial Least Squares (PLS) allow the recovery of the true sample composition from the IR absorption spectra measured with the NDIR system, despite the limited selectivity of the filter. Combining model and data processing permits one to predict the effect on the final system specification of design parameters. Here we compare the effect of the technology used for the filter on the system errors.

In this paper, we present the first sensor ever built using films grown by supersonic beam of cluster oxides as sensing material. Supersonic cluster beams, produced by a pulsed micro-plasma cluster source have successfully used to prepare nanocrystalline thin films of TiO/sub 2/. The sensors, prepared by using different deposition parameters, were suitable for use in a gas sensor array for electronic nose. Sensors showed a quite good response to ethanol, methanol and propanol. Principal component analysis was used as method for testing the array capability in discrimination and recognition of the volatile compounds.

The recent state of the electromagnetic (EM) sensors for microsatellites development is reported. The set of EM sensors produced at Lviv Centre of Institute of Space Research (LCISR) includes the following devices: flux-gate magnetometers (FGM); search-coil magnetometers (SCM); electric probes (EP); and wave probe (WP). The WP is another kind of instrument which combines in one sensor three independent sensors: SCM, EP and split Langmuir probe. Such a combination allowed one to create a principally new instrument. The developed theory confirms that WP can directly measure wave vector components in space plasma. All these types of space sensors are described and their parameters are presented.

A fully integrated laser Doppler velocimeter sensor is presented in this paper. The size of the sensor head is 4 mm width by 2 cm long. The fabrication of the whole system is described and optical characterizations are thoroughly discussed Wall friction measurements are compared, with a good agreement to other measurement techniques. Finally, the possibility of measuring velocity from the light diffused by submicrometer particles is discussed.

A novel single crystal silicon MEMS fabrication process is proposed using proton-implantation smart-cut technique. Compared to conventional SOI wafer fabrication processes for MEMS applications, this technology can potentially result in a significant substrate and processing cost reduction. A single crystal silicon layer with 1.78 /spl mu/m thickness has been achieved using the proposed technique. Prototype structures such as cantilever beams and clamped-clamped micro-bridges have been successfully fabricated as demonstration vehicles for future micro-system implementations.

A method of using FEA software in direct calculation of the performance of MEMS pressure sensors is described. The pressure sensor is one of a family of MEMS pressure sensors, which use a piezo-resistor bridge on a silicon diaphragm as the transducer. The sensor model includes level-0 packaging and the geometry is parametric so that it can easily be applied to design variations. The method computes the resistance of the piezo-resistors by calculating the piezo-resistance in each finite element. Then an accurate total resistance is calculated as a function of pressure and temperature, from which the transducer signal is estimated. The transducer signal is described in terms of the sensitivity, linearity and offset. The sensitivity matches the measured data within the one standard deviation of the measured values. Deviation from linear is within 0.2% of the measured values. Not all of the significant factors that contribute to the offset have been included in this method.

A study was undertaken to fabricate flexible silicon substrates for high-density packaging. Two different fabrication methods were evaluated to obtain the best mechanical strength. To protect the structures from KOH etching an electroplated layer of nickel was used as protective layer. Structures are fabricated with electroplated gold leads to ensure low resistance.

A local sensor bus for transmitting data from several digital smart sensors to an Internet interface was tested. The master/slave type bus is based on the three-wire SPI (serial peripheral interface) bus, which is built into most microcontrollers. At the sensor end, after A/D conversion of the analog sensor signals and further processing of the digitized data, the data is formatted into standard 8-byte ASCII code, which can be read directly by any computer. A header indicates the type of sensor data, for example, TC123.45 for a temperature sensor reading 123.45/spl deg/C. The data is in the form of an email so the following Internet interface (TCP/IP) only retransmits the data to the requesting browser where it is displayed in the same format as any email The Esbus format consists of an 8-byte request from the master followed by 32-byte response from the selected slave. The response is subdivided into an 8-byte header, which identifies the sensor and channel number, and three sets of 8-byte sensor data, as described above. In order to adapt the SPI an addressable network, the data output driver is converted to open collector. The paper will describe the I/O circuits, waveform/timing, and data formats for a specific smart sensor (temperature, humidity, illumination).

In this paper, the fabrication, characterization and test of 2D-optical lenses using PDMS material are reported in order to perform on a portable chip a fluorescence spectroscopy using optical fibers. The technological steps to make the PDMS layer are first detailed, and the patterns then checked with a SEM. By comparing different interfacial structures, it is shown that the light beam characteristics can be modified and slightly focused on the micro-channels where fluorescent dye is flowing. For a constant dye concentration, the use of such lenses enables one to increase the intensity of fluorescent response compared to the same design with a flat interface, which corresponds to a better sensitivity of the detection method.

The next several years will witness the evolution of sensor networks from simple test-and-report wired systems to intricate wireless information fabrics that connect our surroundings to the information super highway and cyberspace. These systems will be applied to agricultural monitoring, medical monitoring, intelligent space realization, automotive safety, personal area networks, and even wartime intelligence. To enable these applications research efforts will be focused on developing low-power, low-cost sensor technology and creating networks that self-assemble, self-anneal and self-heal into an emergent life-like system. The human nervous system with its 7-8 billion neurons represents a compelling model for such systems. Each wireless sensor device can be interpreted as a neuron with radio frequency (RF) connectivity. These devices are referred to as neuRFon/spl trade/ devices and can sense the environment, process various stimulus, and transmit a request for action while consuming very little power and requiring minimal, if any, human intervention. This paper presents an overview of neuRFon/spl trade/ technology and some of the associated challenges in the design and implementation of wireless sensor networks.