Sensors and Microsystems

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FOREWORD.

CONTENTS.

The eukaryotic cell is a unique system in which an extremely high number of complex biomolecules and ions are so well organized that they are efficiently utilized in different pathways without interfering between each other, because of separate internal compartments that define different spaces. Nevertheless, these compartments exchange material and information so that the cell's life is a fine-tuned integration of a large numbers of events that have to take into account the outside environment as well. Then, a cell must be able to check and monitor the inside and outside space in order to make the right decision each time it has to. Some of the strategies set up by the cell to solve its problems will be briefly addressed in this paper: high accuracy of fundamental processes, internal organization, specific checkpoints, connections with the outside environment and sensory organelles able to monitor it. By integrating all the cues, the cell will normally end up with the right decision, depending on the situation: to wait and rest or to move, to proliferate and/or differentiate and, in the worse case, to programme its own death.

The concept of the European Research Area - ERA, the RTD within the 6^th FW performed alongside major focused initiatives with a structuring context, the notion of Ambient Intelligence, the micro and nanotechnologies passed and present strategy are synergic aspects of a complex strategic program aiming to achieve a new vision for the research at the European level. This new vision has been considered very important and necessary to improve the European industry competitiveness in old and in emerging new sectors, while improving its effectiveness in using all the available economic resources and its capacity to transform, more quickly and efficiently, the RTD results into innovation.

The need of process and quality control in many industrial fields is requiring the development of optical sensors taylored for specific applications. These sensors must be potentially low cost and possibly should integrate on the same die signal processing capabilities. Standard CMOS technology is therefore the technology to choose for satisfying these requirements. Two examples of application specific vision sensor are presented in this paper. The first is a focal plane array with very high dynamic range for the automotive industry, and the latter is a linear array with on board processing for a triangulation based 3D laser scanner.

Silicon radiation detectors represent one of the main research lines of the ITC-irst Microsystem Division. Specially tailored fabrication technologies for particle detectors have been developed in the past few years, and production and R&D activities are now carried out in parallel. We report on the most relevant achievements, focussing the attention on double-sided microstrip detectors for the AMS and the ALICE experiments, and on new detector developments for X-ray medical imaging and future collider applications.

In this paper we report of the development of a DNA biosensor based on optical detection (surface plasmon resonance). The sensor chip of the optical device Biacore X™ was modified with a new immobilization procedure based on the interaction between the gold surface of the chip and a thiolated oligonucleotidic probe. The hybridisation reaction between the immobilized probe and the complementary target in solution was detected in real time.

Surface Plasmon Resonance (SPR) is one of the most sensitive detection methods for changes of thickness and refractive index in ultra-thin films. In this paper we developed a SPR imaging system in order to characterize organic monolayers, a basic commodity to develop biochemical sensors arrays. SPR image contrast could be enhanced by chemical modifications of the patterned monolayers. The lateral resolution achieved by our SPR imaging device with HeNe laser source and in Kretschmann configuration is about 4 µm.

A biosensor has been developed, based on immobilised Pseudomonas putida cells, operating in n-hexane suitable for determining benzene in hydrophobic matrices in which benzene was contained. The biosensor may be also used in the initial screening, of the pool of aromatic hydrocarbons contained in unleaded fuel, operating directly in n-hexane and using a relatively cheap and simple instrumental set-up.

In this paper graphite or gold working electrodes obtained by several deposition techniques were used as substrates for electrochemical synthesis of Ni-NTA chelators. obtaining higher immobilization yields (increased 50 fold), lower treatment time (5 min) with respect to the chemical treatment (12h), and ability to address the synthesis on only one electrode in a sensor µ-array.

Different membranes were tested on screen printed electrodes to improve signal quality when sensing oxygen at a −700 mV potential (vs Ag/AgCl). The use of a cellulose acetate membrane, drugged with quaternary ammonium salts to provide the necessary electrolyte, allows for a sensible reduction of noise for measurements at negative potentials.

Evolution of a previously reported bienzymatic biosensor for the determination of organo-phosphorous pesticides are reported. This class of pesticides are detected thanks to their high reversible inhibition power towards acid phosphatase (AcP). The catalytic activity of AcP was detected by means of a screen-printed electrode, in presence of the substrate ascorbic acid 2-phosphate (A2P). The current change due to the electrochemical oxidation of the ascorbic acid as reaction product was monitored. Particularly we focused our attention to the determination of the widely diffused pesticides, i.e. Malathion. Results obtained show a high sensitivity, with a lower detection limit of about 5 ppb.

A new disposable electrochemical genosensor for the detection of characteristic sequences related to genetically modified organisms (GMOs) was developed. Thiol modified oligonucleotides were immobilised onto gold screen-printed electrodes by self-assembled monolayer technique. The genosensors were hybridised with biotinylated complementary sequences. Streptavidin-alkaline phosphatase was coupled to the hybrid through streptavidin-biotin bond and the electroactive product of enzymatic hydrolysis, α-naphthol, could be detected by differential pulse voltammetry (DPV). The detection limit was 1 µg/L.

Dioxins are highly toxic substances, and well known environmental pollutants and carcinogens. It is of fundamental importance to build a selective sensor for this class of compounds. Our approach relies on the design and development of artificial peptides as a mimic of the Aryl Hydrocarbon receptor binding site (Ah; dioxin receptor) in the living cells. A series of pentapeptides have been designed and their affinity toward dioxin was tested by a computational approach (LEAPFROG™ algorithm). Two peptides A and B (A: [N]Asn-Phe-Gln-Gly-Ile[C]; B: [N]Asn-Phe-Gln-Gly-Phe[C]), have been chosen in order to evaluate their potential applicability in solid-gas analysis by using a QCM (Quartz Crystal Microbalance) sensor arrays. The peptide sequences were functionalised by two terminal cysteine residues in order to achieve a covalent interaction with the QCM gold surface. The peptide immobilisation was accomplished by dipping of the quartz surfaces in mM solution of A and B in i) water and ii) EtOH/water (1:1 v/v). A quantitative evaluation of mass deposition can be obtained from the differences on the quartz frequency resonance. A strong influence of the solvent of the dioxin stock solution (e.g. hexane, toluene) was tested. Both of the QCM sensors (A and B) gave a good linearity against different sample concentrations. In particular, their desorption coefficients (at 20 ppb concentration) were nicely dependent on the free energy of interaction calculated by computational modelling.

This work illustrates comparative experiments on 10-MHz AT-cut thickness-shear mode quartz crystal microbalance (QCM) sensors and 7-MHz resonant piezo-layer (RPL) sensors made by lead zirconate titanate (PZT) thick films screen-printed on alumina substrate. The sensors were sensitized with cavitand coatings (Qx-Cav and Me-Cav) and exposed to different organic vapors to evaluate their different performances.

A new calyx[4]pyrrole-based macrocycle, meso-(tetramethyl-tetraoctyl)calix[4]pyrrole (MTP), has been synthesized and transferred onto solid surface by using Langmuir-Schäfer (LS) method. Scanning Force Microscopy (SFM) investigation showed that the LS films are almost homogeneous and are consistent with the X-type configuration with the hydrophobic tails of MTP disposed almost perpendicularly with respect to the substrate. Induced Circular Dichroism (ICD) experiments in presence of chiral alcohol vapours, such as R(-) 2-butanol, R(-) 2-pentanol and R(-) 2-hexanol highlighted that although not chiral by themselves the MTP molecules within the film exhibit chirality induced by the binding with the chiral guests. These findings make these films promising active layers for the chemical recognition of short-chain alcohol molecules.

Three differently metallated phthalocyanines bearing the same peripheral substituents have been deposited by the Langmuir-Blodgett technique directly onto the quartz crystals of a piezoelectric apparatus and used as the active layers for the detection of different alcohols. The subsequent statistical analysis reveals that in the sensing performances the thickness of the multilayer is a more important parameter than the nature of the central metal atoms in the macrocycles.

Spin coated layers of some metallo-phthalocyanines have been used as optochemically interactive materials in volatile organic compounds detection in the UV-VIS spectral range. Principal component analyses show a good selectivity depending on both the metal and the peripheral substituents. Optical sensitivity towards tert-butylamine, diethylamine, dibutylamine, 2-butanone and acetic acid has been monitored.

Hybrid CoTPP-SnO₂ thin films have been obtained by the sol-gel approach coupled with spin coating technique. These films have been deposited onto interdigital electrodes and their performances as chemical sensors have been measured towards the detection of methanol vapors. These CoTPP-SnO₂ sensors showed fast and reversible responses towards different concentrations of methanol and best results were obtained at 250 °C working temperature, while a sharp decrease was observed at higher temperatures. These results are attributed to the well known catalytic activity of metalloporphyrins, which is not thermally decomposed at 250 °C, as confirmed by optical measurements.

We have designed and developed surface acoustic waves (SAWs) sensors coated by either single-wall carbon nanotubes (SWCNTs) or multi-wall carbon nanotubes (MWCNTs) for chemical detection of volatile organic compounds (VOCs), at room temperature. Upon individual exposure to ethanol, ethylacetate and toluene in nitrogen, the resonance frequency of the SAW 433.92 MHz oscillating sensor exhibits high downshift of 720 (150), 670 (160), 450 (110) kHz, respectively, for SWCNTs (MWCNTs) films dispersed into solvent of ethanol, at room temperature. Higher sensitivity than that of organic layer-coated SAW sensors can be achieved, at room temperature. The selectivity to VOCs under test can be controlled by the type of organic solvent used to disperse the carbon nanotubes as sensing materials onto SAW sensors.

In the present work the interaction of Zn-Tetraphenylporphyrins with chemically different volatile compounds are reported, in order to create Thickness-Share-Mode-Resonators (TSMRs) with optimal thickness for sensing response. Previous results showed isotherm curves typical for each chemical compound, thus demonstrating the selectivity of the used Zn-Porphyrins. However, other parameters are expected to contribute to the isotherm shape, such as the coating porosity, roughness and thickness. In this paper, the behaviour of TSMR sensors prepared with different amounts of the same coating has been investigated. Results indicate a strong correlation between sensor properties and deposition parameters opening the way to optimised sensor fabrication.

The behaviour of an alternating co-polymer, poly(2,5-dioctyloxy-1,4-phenylene-alt-2,5-thienylene), has been first investigated at the air-water interface. The floating has been analysed by monitoring Langmuir curves and Brewster angle microscopy. The floating films were deposited by the Langmuir- Schäfer (horizontal lifting) technique onto various substrates. It is evident from experimental data that a strong co-planarity and interchain association originates above all in the floating film on the water surface and in the transferred multilayers. Such films were used as the active layers in resistive chemical gas sensor device, thus revealing excellent sensitivity towards NO₂, reversibility and time stability of the response.

The morphology and the gas sensitive properties of composite thin films have been studied in this work realizing and characterizing resistive sensing devices working at room temperature. Poly(methyl-methacrylate), atactic poly(styrene), poly-(2-hydroxy ethyl methacrylate) have been used as polymeric insulating matrix. Graphite, commercial carbon blacks and home made carbon nanoparticles have been dispersed in the polymers modulating their conductibility to show the influence of the filler structure, concentration and type. The influence of the polymeric matrix, the filler type, concentration and dispersion, the thin film morphology, all together strongly determine the sensor device response to volatile organic compounds (VOC). The characteristics of the sensors responses to different VOCs (sensitivity, selectivity, response and recovery time) are related to these parameters in order to optimize the sensing device.

In this work we investigate a poly(aniline) gas sensor device characterized by good responses to few ppm of ammonia in air at different humidity levels. Properly doped emeraldine films also exhibit strong photoluminescence when exposed to ammonia vapors. The physical mechanism at the base of poly(aniline) sensitivity, optical and electrical, is investigated in order to evaluate the feasibility of a multi-parametric NH₃ sensor.

Although Polydimethylsiloxane (PDMS) is one of the most widely used polymers, up to now there are few evidences of its application as gas sensor. In this work, we investigate the effects of volatile organic compounds (VOC) on optical and electrical PDMS physical properties. In the former case, cross-linked PDMS samples, exhibit a strong photoluminescence even when simply excited by a blue LED. The emission is stable in controlled air for several days and it quenches when exposed to several VOCs. As far as resistive sensors are concerned, the PDMS strong insulating properties have been modulated using commercial carbon blacks as conductive phase. Measurements of the electrical conductance variation vs. vapors concentration show a strong and fast response, even for concentrations in the order of hundreds of ppm. In this case, recovery seems to be the major problem.

The aim of our recent research is the synthesis of new molecules suitable for applications in gas sensors. In this work we extended our studies on the sensitive behaviour of a polymeric material (Pt-TRI) prepared from a square planar Pt(II) complex and the organic spacer [2-ethynylthiophene]2,5 bis-ethynylthiophene. The responses to relative humidity and alcohol vapours variations of sensors based on these organometallic polymeric membrane were investigated. A interesting response towards methanol and ethanol was found. Moreover current vs temperature measurements were performed in the range from 20 °C to 75 °C with different applied voltage in order to evaluate the activation energy of the polymeric membrane.

A polymer-coated surface transverse acoustic wave (STW) resonator for applications in high resolution humidity sensors was developed. The acoustic device was designed to resonate at 316 MHz and realized on AT-cut quartz substrate to minimize thermal dependencies. Different kinds of polymeric films (HMDSO and a-C:H) deposited via PECVD method, were tested. The device resonant frequency shift versus the sorbed water vapor mass, was measured at controlled relative humidity and temperature. An average sensitivity of 15 ppm/% change in RH was obtained which was found to be about one order of magnitude higher compared to the best result reported in the literature. The response time to a step of 90% RH was found to be less than 30s, showing a fast performance.

Different methods for obtaining WO₃ powders suitable for gas sensing have been developed. Aqueous and alcoholic solvents proved to be the most promising media to grow nanometric particles. Morphological characterization highlighted that ethanol and a di-chetone led to a finer grain with a more homogeneous size distribution. Thick films of WO₃ responded to NO₂ with high sensitivity. In particular the samples arising from ethanolic solution proved to be the most performing layers.

We present the results concerning the characterisation of nickel oxide thin films deposited by dc reactive magnetron sputtering. Different NiO thin films have been prepared by changing some deposition parameters, as the oxygen content in the reactive plasma and the sputtering mode (metal- or oxide-sputtering mode). The structure and surface morphology of the samples have been analysed by XRD and AFM respectively. Gas sensing tests to NO₂ in the range 1÷10 ppm and to CO in the range of 50÷200 ppm at different temperatures (250÷420°C) have been carried out. A set of NiO films have been also surface modified by Pt and good response to H₂ have been obtained.

Sol-gel derived In₂O₃ thin and thick films were investigated as gas sensors for the detection of very low concentration of CO and NO₂. A marked selectivity towards oxidizing and reducing gases was achieved by properly selecting the active materials from the same starting solution. A morphological and structural characterization of the films allowed to understand their different electrical behavior.

Pt and Au-doped zinc oxide thin films have been prepared by a liquid phase method (LPD) and tested as oxygen sensors in the temperature range between 250 and 600°C. Au-doped films show better sensing characteristics than Pt-doped films, allowing operation at temperatures as low as 300 °C. Au-doped ZnO sensors are most promising in terms of response, response time and stability and show a low temperature coefficient in the temperature range between 300 and 400°C. On the basis of the results reported, a discussion on the effects of metallic dopants on the oxygen gas sensing mechanism of ZnO-based thin films will be presented.

Currently, production automobiles utilize an exhaust gas sensor, lambda sensor, located in the main exhaust stream in order to regulate air/fuel mixtures. The control of engine exhaust is also important activity for environmental protection. The EFI (Electronic Fuel Injection) system was introduced to precisely control the air – fuel ratio, and it has been contribuiting in decreasing toxic exhaust and improving fuel efficiency. Commercial lambda sensors are characterized by electrochemical cells based on oxygen - ion conductor ZrO₂ and a heater element made of highly insulative alumina or silicon nitride. Here we evaluate the gas sensing properties of sol – gel TiO₂ thin film based sensors for future automotive application as lambda sensors.

The hydrogen gas sensing performance of Pt/ZnO/SiC solid-state structures has been investigated. The ZnO thin films were deposited by a planar r.f. magnetron sputterer onto n-type 6H silicon carbide wafers. These devices were employed as Schottky diodes and operated in constant current mode. Exposure to different concentrations of hydrogen gas results in changes in the device's carrier concentration and hence in the Schottky barrier height. This results in a change in the forward bias voltage. The ZnO thin films, after annealing in static air at 300, 500, 700 and 900°C, have been characterized by X-ray Photoelectron Spectroscopy (XPS) and X-Ray Diffraction (XRD). The formation of hexagonal ZnO ICSD card. N° 29272 was observed when the films were annealed at temperatures greater than 500°C. The sensors responses to hydrogen were analyzed when the ambient gas was 5% oxygen balanced in nitrogen. These responses were stable and repeatable in the investigated temperature range of 300 and 500°C.

Ce-doped iron oxide thin films have been prepared by a liquid phase method (LPD) and tested as alcohol sensors. Sensing tests carried out at 300 °C have shown that the addition of Ce to Fe₂O₃ increases the sensitivity to methanol. The optimum loading of Ce was around 50 % in moles.

A microstructural and electrical characterization was carried out in order to investigate the effect of Ce on the methanol sensitivity of Fe₂O₃ films. The reactivity of the mixed oxides towards methanol oxidation has been also investigated. According to the obtained results, a discussion on the role played by Ce on the methanol sensing properties of iron oxide thin films is presented.

CTO powders and thin films have been prepared by a sol-gel route and subsequent thermal treatment at low temperature (≤ 400 °C). The humidity characteristics of CTO thin films have been investigated. Results reported have shown that the humidity behaviour is related to the intergranulary porosity of the films. The Cr/Ti ratio and the role of alkaline impurities (Li⁺) was also studied with aim to clarify the mechanism of the surface conduction of CTO films in the presence of water vapor.

We investigated the effect of humidity on a set of SnO₂ gas sensors. As one might expect, absolute humidity is the only meaningful physical quantity because chemical equilibrium is established by the concentrations of reagents. When absolute humidity is properly compensated for, the gas response follows this dependence because all other parameters keep unchanged.

Li-, Zn- and Au-doped Fe₂O₃ thin films have been investigated as humidity sensing materials. Depending on the nature and loading of the dopant, microstructural modifications on the host metal oxide have been observed. The humidity sensing properties of these films were studied by means of Electrochemical Impedance Spectroscopy (EIS). Humidity sensing data have been then analysed by an electrical modeling and correlated to the microstructural characteristics.

Undoped and doped tin oxide-based microsensors have been prepared by the sol-gel deposition technique. The influence of the ageing of the Ti/Au interdigitated electrical contacts on the responses of the samples has been investigated. In particular, in this paper, we report the responses of different sensors towards some gases as hexanal, acetone and pentanal discussing the reproducibility and repeatability and the baseline drift during the measurements. The sensors showed a little drift probably due to the ageing of the electrical contacts that we observe by SEM images. SEM results were also correlated with XPS analysis.

A theoretical model has been developed to interpret the different behavior of SnO₂ and TiO₂ sensors. It is based on the determination of the surface-state density, which pins the Fermi level of the semiconductor, thus removing the linear relationship between the work function and the grain-to-grain energy barrier. To interpret these differences, measurements of the built-in potential, V_bi, related to the Schottky barrier, were pursued at different temperatures in thick-films of SnO₂ and TiO₂, obtained via sol-gel. The model predicts a decrease in the density of surface states with the grain radius only in TiO₂, which seems to be confirmed by the experiment.

The chemical composition of the thin films of mixed metal oxides (Sn-W, Mo-Sn and Mo-Ti), prepared by magnetron sputtering and by sol-gel, were investigated by standard and angle-resolved XPS depth profiling techniques. Starting from the stoichiometric compounds on the surface and going deeper into the volume of the films, the depth profiles revealed there the presence of reduced metal ions. The possible contribution of sputtering-induced reduction of the oxides, interchange redox reactions between two metal ions in these compounds, influence of sputtering ion energy and photoelectron collection angle are discussed on the basis of obtained experimental results.

The high interest around titanium dioxide is linked to its photocatalytic and photoelectrochemical properties. Photogenerated charge carriers under UV irradiation can migrate to the surface and drive several redox processes, from water splitting in hydrogen and oxygen to the photocatalytic degradation of organic pollutants. Potential applications of TiO₂ thin films range from self cleaning and superhydrophilic surfaces to photocatalytic air and water detoxification. However, it is generally recognized that the photonic efficiency of present materials is not satisfactory. One of the approaches to improve material performance involves transition metal doping of anatase thin films and colloids. The doping could affect not only the optical band gap, but also surface and morphology of nanocristalline thin films. In this work was explored the effect of Sn doping on anatase polycrystalline TiO₂ films. Scanning Tunneling Microscopy (STM) was used to image the sample surfaces. Good STM images were obtained by TiO₂ film deposition on conductive substrates (SnO₂ coated glass). By a statistical analysis of the roughness parameters from the images, a correlation between photocatalytic activity and exposed surface area of the samples has been observed.

Good quality TiC-based thin-films were obtained and used to assemble new electrochemical probes. These films were first characterized using scan electron microscopy (SEM), Reflection High Energy Electron Diffraction (RHEED) and Raman Spectroscopy, which revealed the cubic lattice of TiC. The electrochemical evaluation of these probes has been performed by cyclic voltammetry of classic redox systems, both inorganic ([(Fe(CN)₆]³⁻; [Ru(NH₃)₆]³⁻) and organic (hydroquinone). A near Nernstian behavior has been confirmed for all the studied couples.

The influence of some experimental conditions on the kinetics of electropolymerization of several monomers and the resulting morphology of the nanomaterials has been studied. The investigated monomers were: 1.2-, 1.3- and 1.4-phenylenediamine, 2.3-, 1.5- and 1.8-diaminonaphthalene, o- and p-anisidine, 5-amino-1-naphthol and o-, m- and p-aminophenol, and 3.3'-diaminobenzidine. In particular, the resulting polymers showed that an increase of the ionic strength values increases the polymerization rate at a constant potential, both in buffered solutions and also in acidic medium. Finally the morphology of the different template-synthesized nanostructured materials has been carefully analyzed by scanning electron microscopy (SEM). In addition, emission and Raman spectroscopy showed that the relative conjugation length increases with decreasing pore size.

A disposable modified electrochemical sensor for the detection of heavy metals is described. Coupling this sensor with square wave stripping analysis, detection limit of 0.3ppb, 1ppb, 0.5ppb were found for lead(II), cadmium(II) and copper(II) respectively. The main advantage of this device is the avoidance of mercury solution to perform stripping analysis.

Two phthalocyanines and a porphyrin with different central metal atoms (Cu, Ni and Co, respectively) were deposited by the Langmuir-Blodgett technique directly onto the quartz crystals of a piezoelectric apparatus and used as the active layer for the detection of phenols in liquid phase. Reproducibility, reversibility and time stability are the main characteristics of the sensors. For the investigated active layers, the subsequent statistical analysis revealed that in the sensing performances the responses of the two different phthalocyanines were redundant.

A description is given of a preliminary approach to the use of a new generation solid state sensor based on the capacity of the sensor element to catalyze the photodegradation of various kinds of organic compounds and to recognize their structure on the basis of the type of process catalyzed. The electron holes present in the TiO2 structure are able to trigger an oxidative process involving substances present in the environment, in particular those ones that can be adsorbed on it. These characteristics make titanium dioxide a suitable material to be used as a sensor for antioxidant, i.e. reducing, substances. By reacting with it these substances produce potential variations corresponding to values specific to the above mentioned photo-oxidative processes.

A fiber optic multimeter is presented, consisting of a platform for interrogating an array of absorption-based chemical sensors. It has been validated on a set of porphyrin-based materials having gas-sensor potential. Discrimination between different kinds of gases has been demonstrated.

A first prototype of an electro-optical nose has been designed, assembled and tested. This new system is made up of a matrix of silicon integrated photodiodes (the electro-optical transducers), coated by different thin films of metalloporphyrins (used as chemically interactive material -CIM- with a function of incident light filter), and of a blue LED source with an emission peak centred in the main absorption band of the CIM (the Soret Band, around 430 nm).

The occurrence of the Sick Building Syndrome (SBS) inside buildings equipped with Heating Ventilation Air Conditioning (HVAC) Systems can be reduced by controlling the concentration of pollutants in the indoor air. This can be achieved by smart intervening procedures implemented in the HVAC control system, which will be operated on the basis of reliable information about both the indoor and outdoor air quality, aiming to ensure the most appropriate amount of ventilation. Within CLEAN-AIR, we are developing a dedicated, miniaturized, low-cost electronic nose realized using state-of-the-art microsystems/sensors fabrication technologies. This e-nose provides data as input to the specifically implemented smart intervening procedures, which will allow the HVAC system to be operated under demand, rather than by a fixed duty cycle.

At current there is a great interest in developing new techniques for the food quality assessment. Electronic nose is considered an attractive technique for evaluating food aroma. In this work we present an overview of application examples of an electronic nose based on sol-gel metal oxide gas sensor array to the evaluation of some foodstuffs (milk, dry salami, olive oil and peach fruit). The responses of the sensor array to the flavours of these foodstuffs have been correlated with the results obtained by other standard techniques.

Pharmaceutical products are eligible for electronic nose characterisation. In particular, being the composition reported in the accompanying documentations and having a large availability of products differing one each other only for few components.

In this paper, preliminary tests performed with the ENQBE electronic nose and aimed at distinguishing between different classes of medicines are discussed. The possibility to distinguish between specific commercial and generic pharmaceutical products is also illustrated and commented.

The development of chemical sensors operating in the liquid phase has been performed by deposition of thin film of metalloporphyrins onto glassy carbon electrodes by electropolymerization technique. An array of the developed Potentiometric sensors has been exploited for the analysis of real matrices. This array was able to discriminate among different brand of commercial mineral waters and among model sample contaminated by heavy metal salts. The developed electronic tongue was also successfully exploited for the discrimination among pharmaceutical drugs belonging to the same active principle but differing for excipients.

A study aiming at the discrimination of basic tastes by measuring the variations of the electrical impedance of a sensor array is presented.

In the last decade many kinds of partially selective sensors have been developed, both for gaseous and liquid compounds, to be used into arrays capable of generating characteristic fingerprints of complex samples. Relevant data are analysed by pattern recognition techniques, mimicking the functionality of the human sense of smell and taste.

In the case of electronic tongues, three measurement techniques are mainly used for sample analysis, i.e. potentiometry, voltammetry and conductimetry.

In this work, the electrical impedance of a sensor array was measured at a frequency of 150 Hz by means of an impedance meter. The measurement process was automated; a mechanical arm and a rotating platform controlled by a data acquisition card and a dedicated software allowed the sequential dipping of sensors in the test solutions. The array was composed of five sensors of three different types based on carbon nanotubes or carbon black dispersed in polymeric matrices and doped polythiophenes.

Measurements were carried out on 15 different solutions representing the five basic tastes (sodium chloride, citric acid, glucose, glutamic acid and sodium dehydrocholate for salty, sour, sweet, umami and bitter respectively) at three concentration levels comprising the human perceptive range. More than one hundred measurements were carried out for each sample in a six month period to evaluate the system repeatability and robustness. A fairly good degree of discrimination was obtained analysing the data by linear and non linear pattern recognition techniques.

The feature extraction is the operation aimed at extracting from the temporal evolution of the sensor signal a number of synthetic descriptors to be used in the input of pattern recognition model. A comparison of two alternative approaches is investigated. These novel methods are based on an array driven feature extraction, and a specifically defined phase-space where sensor signals are represented. In this paper, these methods are described and illustrated through two typical electronic nose applications.

The paper describes the design and development of an apparatus for DNA analysis based on chip electrophoresis [1] and laser induced fluorescence (LIF) techniques. The system employs a solid-state sensor called SPAD, for the detection of extremely low fluorescence intensities. The system is highly automatized and user-friendly. The sensitivity limit of the apparatus reaches the picoMolar range. Thanks to an automatic search and positioning system, it is very easy to arrange different chip types and configurations.

Functional integration, flexibility and massive parallelism are the main features required for the next lab-on-a-chip (LOAC) generation. Embedded complex circuits of the size of a cell are required for single cell manipulation, while massive parallelism is feasible if individual cell manipulation and detection capabilities are integrated in a flexible and programmable hardware platform. An example of lab-on-a-chip for individual cell manipulation and detection is presented. The device is equipped with a bidimensional array of 320×320 individually addressable and programmable micro-sites; each site embeds both a sensor and an electrode. By individually programming the voltages applied to the electrodes a dielectrophoretic closed cage can be realized in correspondence of each micro-site¹. More than 10,000 cells can be trapped in stable levitation, each in a different cage and individually moved from one site to the next along the whole micro-chamber; a deterministic control on each cell location is assured by the "moving-cage" principle² combined with optical sensors³.

In this paper we present a novel drug delivery device that: 1. is able to release drug in a controllable way (one shot, multiple shots, continuous release); 2. has power requirements compatible with those of standard integrated circuits; 3. can be easily miniaturized. The actuation principle relies on the electrolysis of a water-based solution that is kept separated from the drug by an elastic membrane. The pressure generated inside the chamber containing the electrolytic solution causes an outward deflection of the membrane that forces the drug to exit its storing chamber through an outlet orifice. The drug out-flow can be electronically controlled and different releasing modes can be achieved (one shot, multiple shots, continuous delivery). Voltages as low as 2V are able to activate the device, with extremely small currents (≪1mA). A first prototype has been fabricated and tested. Flow-rate and pressure vs. time measurements have been performed, which confirm the suitability of the device for in-body applications.

DEParray™ is a biosensors/actuator implementing Silicon Biosystems' patented technology for individual cell manipulation^1,2 and detection³. The base of DEParray™ is a microelectronic active silicon substrate embedding control circuitry for addressing each individual dielectrophoretic (DEP) cage and integrated optical/capacitive sensors to detect the particles inside each cage. The unprecedented flexibility and selectivity afforded by this device represent a breakthrough for biological research and analysis.

This work presents the development of a fabrication technology for a silicon-based microcolumn for gas chromatographic measurements. The system consists of two main components: i.) the silicon wafer micromachined separation capillary column and ii.) the metal oxide semiconductor detector made on silicon membrane. The final goal will be to realize low cost and portable miniaturized system expressly designed for the detection of infant neuroblastoma tumor. In this preliminary work both simulation and technological aspects have been considered for the fabrication. The microcolumn design has been performed in order to optimise the separation factor. Silicon micromachining techniques have been applied to the fabrication of the device.

The design and development of a microfabricated sensor for atmospheric mercury determinations is described. The sensor is based on the technique of resistivity variation of thin gold film. Properties, advantages and drawback of two different substrates (glass and PCB) have been presented. Experiments have been carried out to test the linearity of the sensors in function of mercury adsorption. The sensors work in a large range of linearity and need a low power during the regeneration process. Other tests were carried out in order to evaluate the 'sensor endurance' to regeneration; unused sensors on glass and PCB substrates underwent numerous regeneration cycles without inflicting any mechanical or electrical damage to the resistors.

This paper reports the design, realisation and preliminary testing results of an integrated air flow sensor based on micromachined technology.

The mass airflow sensor architecture consists of microelectronic thermal (hot-wire) anemometer design: two separate photomask sets were developed using L-Edit™ software (by Tanner Research), with different layout for the two different splittings projected, one for the polysilicon resistor process and the other one for the gold resistor process. The working mode of the system is very simple: when there is no flow, the temperature profile around the hot resistor on the membrane is symmetrical. When gas flows, the symmetry is perturbed and we can measure this by controlling the difference in the resistance of the heaters. A flow rate can then be correlated to this differential change in temperature. The advantages are: the very small sensor size, the low power consumption, the velocity measurement range, the simultaneous fluid temperature measurement, the good accuracy, the very low signal to-noise ratios, the excellent frequency response, the operational simplicity, a continuous analog output signal and the low cost of the sensor device.

We realised a micro air flow sensors prototype, fabricated with MEMS technologies. Preliminary electro-mechanical tests were carried on demonstrating the high performances of this device.

This work focuses on the fabrication of a piston-type silicon condenser microphone. The proposed device is basically composed of a movable polysilicon diaphragm and a fixed gold backplate, making up the condenser electrodes. The movable electrode is realized by a rigid plate supported by small flexible springs. In order to manufacture plates which are rigid and light at the same time, polysilicon membranes stiffened by vertical ribs are investigated. The fabrication technology developed for this purpose is a variation of the HEXSIL process [1]. Both the piston and the springs are manufactured through the same polysilicon deposition, thus providing a simple process for the fabrication of the structured diaphragm. The fixed electrode is fabricated on the same chip by electroplating a thick layer of gold. The resulting process employs a combination of bulk and surface micromachining techniques. In this paper the process architecture used in the fabrication of the first prototypes is presented and some related technological problems are discussed as well. Preliminary results on the functional characterization of the microphones are finally reported.

This article deals with basic investigations of the development and manufacturing process of a piezoelectric driven microactuator for nebulization of fluids. The concept of the fabrication of the micronebulizer will be introduced. First fundamental investigations on materials characterization and process technology for the electrodes and piezoelectric AlN layers will be presented. AlN thin films have been depositetd by reactive sputtering technique and have been characterized with dielectric and ferroelectric measurements.

In the last years there was an increasing interest in micromachined RF switches, mainly in the communication and space industries. This article describes a fabrication process used for the development of electrostatically actuated MEMS RF switches operating in the 2 - 40 GHz range. Results of the RF characteristic measurements of single switches are presented and possible improvements are discussed.

In this paper two sensing applications of Antiresonant Reflecting Optical Waveguide (ARROW) structures are proposed. In the first, we show that, by a suitable design, a conventional ARROW waveguide can be turned in an integrated optical refractometer useful in chemical and biochemical sensing. In the second application, using some peculiar properties of ARROW structures, we have designed and realized an integrated flow cell by an hollow core ARROW waveguide.

Previously obtained results of low temperature bonding of borosilicate glass using potassium or sodium silicate as adhesives have been investigated. The main problem was that voids and clusters appeared in the silicates layers and drastically diminished the bonding strength and uniformity. In order to overcome this problem a glass-to-glass silicate assisted bonding has been experimentally analyzed and accordingly the technological conditions of deposition and annealing process have been modified.

The surface wet ability prior to bonding has been increased by immersing the glass plates in HF 5%vol solution and by exposing them to O₂-plasma. A better uniformity and thickness control of the silicate layer have been reached by introducing a delay step in the spin-on deposition process. An appropriate viscosity of the silicate layer at the solid-air interface has been obtained using a stepwise speed-time characteristic and a second spin step. The adhesion has been significantly improved when increasing the force applied on the glass surfaces in contact.

Polycrystalline silicon films have been grown from Si₂H₆ by Low-Pressure Chemical Vapour Deposition (LPCVD) at 800K and in-situ laser annealing on amorphous silicon seed layers deposited on a metallic Ti/Pd/Ag multilayer. The crystalline volume fraction in the seed layer was controlled by thermal annealing. According to the Metal Induced Crystallization (MIC) effect, the presence of the metal induces a lower-temperature crystallizzation of silicon in the seed layers. XRD and SEM data show that the formation of palladium silicides in the seed layer drives the growth of wire-like columns which are found to change morphology depending on the seed layer microstructure and laser annealing parameters. Superficial palladium was found to affect also the growth rate by enhancing the Si₂H₆ dissociation.

In this paper the electrochemical silicon etching in HF-based solution is demonstrated as a new technique for silicon micromachining, alternative to commonly used methods. Electrochemical etching of silicon in HF-based electrolyte, a well known technique for regular macropore formation, is here exploited to produce a multitude of different regular silicon microstructures (microtubes, microtips, microchannels, microspirals, micropillars, microwalls, etc.). The electrochemical micromachining technique is here detailed and discussed.

The concept of temperature coefficient of resistance (TCR) entail a device with uniform temperature. However, Joule heated integrated metal resistors usually feature a non-constant temperature profile. After defining an effective TCR, this paper describes simple analytical relationships able to justify its constancy in the case of the heating element of a micromachined gas sensor.

A fundamental loss mechanism in microresonators at low vacuum levels is the energy transfer from the resonating mass to the surrounding gas. Both continuum models (based on Navier-Stokes equations) and molecular models (based on the microscopic motion of the gas molecules) have been proposed to explain experimental damping data. In this work, we present measurements of quality factor and damping factor, extracted with a novel measurement method, for several micro-machined resonators, and we compare them with theoretical predictions both for continuum and molecular models. The second approach, which does not require ad-hoc hypoheses and has a stronger theoretical basis, is shown to fit experimental data more accurately as well.

The diffusion of thermal gas flow sensors in the field of microfluidic, biomedic and aerospace applications has led to a growing request for more and more accurate devices suitable for very low flow rate. In this work, a theoretical and experimental investigations of the response of a micromachined silicon anemometer in very low gas flow rate is reported. In particular, the dynamical range and sensitivity limits of the presented thermal sensor have been investigated. Possible solutions aimed to increase the sensor performances have been also proposed and discussed.

This work analyzes the main aspects related to long term electro-mechanical measurements on RF MEMS switches fabricated for DC to 30GHz; the fabrication process, design, and adopted experimental procedures have been also described in details.

Particular attention as been dedicated to the stress effect for studies to different behavior due to applied electric field.

In this work, the internal stress of grown silicon oxide, CVD silicon nitride, evaporated chromium and gold, conventionally used in micromechanics were investigated. Gold films were deposited both by PVD and electroplating, the latter using two different bath solutions (sulfite and cyanide). Stress measurements were carried out by wafer curvature comparison, before and after deposition, using Stoney's formula for thin films ^1,2: wafer curvature was measured by profilometer. The possibility to tailor the internal stress of electroplated gold was investigated, obtaining a stress range from tensile to compressive: cyanide bath yielded stress from −30 MPa to about 0 MPa, and sulfite bath showed stress between −90 MPa and 110 MPa. The obtained stress values can provide fundamental information for the design of micromechanic devices: particularly interesting is the stress of electroplated gold since this layer, combined with photoresist as a spacer, provides an excellent surface micromachining structural material for low temperature processing, with the possibility to set the internal stress of the micro structures by changing the plating parameters.

The main object of the paper is the implementation of two different approaches for the estimation of the modulus of elasticity and of the failure strain and stress in micro machined structures manufactured of epitaxial polycrystalline silicon. The micro test structures are produced using a standard THELMA process becoming an integral part of a MEMS actuator of comb-finger type.

A MEMS components model library is implemented within the Cadence^® simulation framework, yielding to a hierarchical, fully mixed-domain design environment based on an IC-design framework. The modelling tools are matrix based structural analysis and analogue hardware description language SpectreHDL^®, while finite element method simulations are used as a validation tool. The benefits of the obtained top-down multi-domain design apprach are demonstrated through the design of a MEMS varactor, to be inserted within a CMOS radio frequency voltage controlled oscillator. Gained access to both electrical and mechanical parameters and quantities during static and dynamic simulations proves to be the key tool for aiming at overall optimum design.

This work describes the simulation of a MEMS-based oscillator, composed by a MEMS resonator and a transresistance amplifier. The presented implementation uses standard Vhdl-Ams language, a suitable behavioral language for describing mixed-domain systems, and was simulated by using the developed Vhdl-Ams compiler and simulation framework SAMSA, which allows for complete DC, AC and transient analyses. By using this tool, modeling and simulation of several MEMS devices is possible, and complex analog/digital systems can be designed and simulated together with different simulation techniques, exploiting Matlab™ functions and Toolboxes.

The understanding of how brain works is strongly connected to the capability of managing and understanding the spontaneous communication, realized by electrical activity, among its units.

Recent developments in neuroengineering led the possibility to build new electrophysiological systems for the stimulation and recording of simultaneous activity of large populations of cells. Using Microtrasducer Arrays (MTAs), on which cells culture can be grown and kept alive for long time (from weeks, up to several months), it is possible to define distinct collective functional states of the network and to study the dynamic behavior of the neuronal population.

Despite the widespread use of such electrophysiological experimental systems, there is a lack of commercially available tools for data analysis and visualization and those existing could not easily used within these emerging recording techniques and their compatibility is usually limited.

Commercial systems are usually sold with their recording software, but several problems occur trying to customize such systems in order to realize particular experimental procedures.

Multi-sites analog to digital conversion and storage cause several problems such as the large amount of incoming data stream (depending by the number of source channels, the sampling frequency and the resolution bits of each sample), the overlapping between signal sources, the needing of automating, the space-temporal patterns of the recorded activity have to be related to the topological structure of the substrate, etc.

The purpose of this paper is to introduce a developed software package that could be easily adapted to different experimental recording systems. It integrates features that permits easy customizations for different type of microtrasducer arrays (i.e. ISFET, planar TiN / SiN electrodes, etc.), and different AD boards (i.e. NI 16-F AT MIO, NI PCI 6071E, etc.), including data transmission trough several protocols and devices (i.e. RS232, NI PCI DIO 32HS, etc.).

The software was developed with the aim to realize a central core which allows to integrate different system solutions by adding further different modular libraries.

Data managing functions are controlled via a Graphical User Interfaces (GUIs) and data format are compatible with most used applications for data displaying and analysis such as Microsoft® Excel and Microcal^(™) Origin®.

In this paper, we discuss the potential implementation of silicon carbide radiation detectors: by means of simulation studies we carry out a comparison between a typical silicon detector and a silicon carbide radiation sensor in terms of charge collection efficiency related to the crossing of a Minimum Ionizing Particle (MIP). We also compare different technological options for the SiC detectors, looking for optimal overall performance of the sensing system.

Microelectromechanical (MEM) switches have been recently considered as alternative key elements with respect to PIN diode switches for high frequency applications. In spite of many configurations proposed in literature, a full theoretical modeling of the MEM switches is still in progress by using numerical and analytical approaches. In this paper, a phenomenological modeling of a classical MEM switch configuration is presented, to describe the microwave performances resulting from this mechanical device.

In the last decade, fundamental advances in the fabrication technology of cell-based microsystems have demonstrated the feasibility to utilize living cell as primary transducer to detect biologically active agents [1]-[2]. This screening-based methodology represents an emerging technique and benefits a large area of biomedical applications, ranging from basic research to various fields of pharmacological analyses. In this paper we describe the design implementation, validated by experimental results, of an integrated read-out circuit for field-portable silicon based microsystem designed for multisite monitoring of the physiological state of a cell population.

The studies on VOC's sensors have received a great deal of attention worldwide. Bubblers can be used in experimental set-up in order to produce vapours of different liquid substances. Experimental method has been elaborated, which allows to determine the evaporation rate of alcohols forced to bubbling with a nitrogen flux. Temperature dependant measurements where performed to evaluate the liquids mass loss for different environmental situations. We have found a good approximation between our experimental data and the theoretical expression for water evaporation rate. Our final goal was to find a relationship between alcohol concentration in the test chamber and the carrier gas flux.

Miniature detector modules including Single-Photon Avalanche Diodes (SPADs) and the associated electronic circuitry (an integrated Active-Quenching Circuit - iAQC), are here presented. These modules are able to detect single photons, and can be used in any application where very faint and/or fast optical signals must be measured. Thanks to the small size and the limited power consumption of the CMOS design of the iAQC, these modules can be housed in standard packages (e.g. TO-8) and can be fitted also in restricted spaces within instrumentation systems, such as microscopes or cryostats. The employed quenching circuit is the first fully monolithic iAQC reported in literature; US patent and European patents have been applied for its design. It can swiftly quench and reset the SPAD biased up to 40V above breakdown. The total counting deadtime is less than 50ns, corresponding to a maximum saturated counting rate of 20Mcounts/s. The circuit provides also a gated-sensor operation mode, with minimum gate-on time interval of about 50ns. The compactness, low-power design and high reliability of the iAQC make it suitable also for multi-sensor systems, such as linear and square arrays of SPAD detectors.

Image sensors for Web, PDA and Cellular Phones miniaturized video cameras are strongly affected by low yield during the assembly process.

Using silicon through vias for electrical interconnections: a quite new technological platform at wafer level developed at ST (Cornaredo R&D site), it is possible to simplify the assembly process of several sensor devices.

The proposed architecture allows the wafer protection during wafer dicing for singulation and then the possibility to have dangerous particles on the active surface is reduced. Moreover, this approach eliminates the active manual tuning of the optics currently performed during the final assembly process.

We discuss the realisation and characterisation of simple diamond-based optical Position Sensitive Detectors in which the contact geometry is studied for efficiently monitor one- and two-dimensional light beam displacements. Diamond PSDs show an intrinsic solar blindness, a linearity around 0.99 and a very good response speed under the 193 nm, 3 ns pulsed excimer laser irradiation used for the characterisation.

Hot-carriers in MOSFETs are responsible for time-dependent near-infrared emission, synchronous with the switching transitions of CMOS circuits. Fast electrical waveforms propagating through integrated circuits can be effectively measured by means of high sensitivity solid-state photodetectors with sharp time-resolution. In our setup we combined two photodetectors: a CCD camera, with high quantum efficiency and imaging capability, and a Single-Photon Avalanche Diode (SPAD), with ultra-fast time response (less than 30ps of time jitter). We developed a photoemission model and we introduced it into a SPICE simulator in order to foresee the luminescence waveforms in the actual working conditions. In this paper we discuss the joint use of luminescence measurements and circuit simulations in order to analyze the signals propagating through a mixed analog/digital CMOS circuit.

The glass transition zone of thin polymer films on silica substrates has been investigated by using a novel optoelectronic integrated sensor involving refractive index and temperature simultaneous measurements. The sensor design is based on the deposition of a thin polymer film on the distal end of a standard optical fiber. Direct reflectometric interrogation and fiber Bragg grating operations have been used to simultaneously retrieve information about the refractive index variation over the glass transition region revealed by a temperature ramping. The glass transition has been identified by measuring the change of thermo-optic coefficient in cooling down experiments. The comparison between refractive index and standard calorimetric analysis has been carried out to test the optoelectronic integrated sensor reliability. The proposed sensing system has been demonstrated able to measure the glass transition temperature of thin polymer films. Moreover systems and procedures can be readily implemented to investigate the effect of polymeric sample finite size and specific energetic interactions on the glass transition zone.

The development of a multifunction automotive sensor with the integration on a single CMOS array of several sensing functions is the main goal of SIRPA project. This paper refers to some results of the project. First of all a new automotive function has been designed: the visibility detection. Then three sensor prototypes have been developed: a fog sensor with PIN receiver, a multifunction sensor with standard CMOS array, a chip in 0.35µm CMOS technology for rain detection.

Color and turbidity measurements performed in the visible spectral range and at many angles are presented to evaluate the content of A and B chlorophylls and pheophytins, as an alternative for HPLC technique.

The applicability of fiber optic sensors to the automotive field was evaluated within a national project, in which the Fiat Research Centre, RTM and CNR-IROE are involved. The measurement of the mechanical distortions on a vehicle windshield was considered as a case study. This paper refers mainly to the validation phase of the project and in particular to the distortion measurements on a windshield of a FIAT "Brava" using fiber Bragg gratings. The results were compared with data collected by using strain gauges and thermocouples.

The developed instrument for CO₂ power laser beam diagnostic was implemented with a new module for beam position monitoring. The sensor module consists of a four quadrants full size 25×25 m² PVDF pyroelectric array. The beam centroid position is visualized in real time on a color LCD. This display is provided of a touch screen for a friendly use interface command. The instrument is interfaced with other measuring modules with pyroelectric matrix arrays.

The possibility of generating sub-harmonic components, via a non-linear interaction between the contrast agent and ultrasonic waves is investigated. Evaluations are also given for the pressure thresholds relative to the sub-harmonic activation and the bubble destruction.

Innovative in situ measurement of internal stress of wood during the drying process is presented. In order to quantify the internal stress and subsequent strain generated in wood during the process^1,2, different indirect and semi-direct techniques can be adopted such as the asymmetrical drying test³, and other standard destructive tests: these semi-direct techniques provide measurement of the overall effects of stress as the combination of internal gradients. In order to specifically measure the internal stress at a given depth in the material, an in-situ measurement is required, by inserting a probe which can measure the local pressure of the wood along a specific axis.

This system needs to be non destructive and minimize the interference of the measurement specimen with the material. Moreover, it has to be chemically inert towards the environment of the drying oven.

A custom sensor was designed based on a silicon micromachined pressure gauge inserted in a Teflon nail: Teflon provides protection, it works as a medium between the gage and wood, and it makes it possible to handle the sensor. In this configuration the pressure gauge has directional sensitivity, and therefore axis-selective measurement is possible.

An easy to use sensing device was realized, reducing the package dimension to the minimum (6mm diameter). A silicon pressure gauge by Entran™ was used. The influence of the Teflon package on the gauge sensitivity was studied by finite element simulation using ANSYS™ software.

Measurements of internal stress during drying process were carried out and compared with results obtained by different measurement techniques. A first empirical confirmation of the theoretical models for wood stress was obtained. The research have been carried out in the framework of "SILE 2" project, with the financial support of the Autonomous Province of Trento.

The contactless heart beat detector could be used in medical, civil and safety fields. Our experiment has concerned with the detection of the heart beat rate without electrodes attached to the body.

We have studied different capacitive sensors, different relative positions between the body and the sensors and a variety of algorithms in order to obtain the best signal to noise ratio.

In this paper we describe the design and development of a thermometer sensor integrated with a Bluetooth modem device which is used to send measured termal data to a remote PC. System implementation details and demonstration results are provided. The integrated Bluetooth platform can be easily re-adapted to be interfaced with many other sensors other than the thermometer.

This paper treats of the design efforts in creating an effective and robust distributed measurement and control architecture for multisensor systems, founded on the recent and topical IEEE 1451 Smart Transducer Interface family of standards [1] and [2], that provides the common interface and enabling technology for the connectivity of transducers to microprocessors, control and field networks, data acquisition and instrumentation systems.

To illustrate these points and to demonstrate the impact of this family of standards, a reference implementation of a simple distributed system for environmental monitoring has been developed and will be here described.