Sensors and Microsystems

The following sections are included:

• FOREWORD

• CONTENTS

Sensors play a key-role in a number of present and perspected space activities. The paper highlights some of those activities, particularly in the area of Earth observation. Furthermore, the key-elements for building effective sensor-based space networks are pointed out and framed in the future plans of the Italian Space Agency.

A 50%30-pixel CMOS sensor aimed at real time three-dimensional vision applications is presented along with characterization results. The sensor is realized on a single mixed-signal chip fabricated in a 0.35-um, 3.3-V, 4-metal/Z-poly CMOS technology. The distance measurement relies on the pulsed indirect time of flight (TTOF) technique, and a precision of 4% is obtained in the 2-8 m range. The real time mode of operation is proved at 20 frames per second with non-cooperative targets.

Analytical methods used for mycotoxin determination are based on TLC, HPLC or ELISA. In the paste decade microarray and microsystem technologies were used for different applications including studies of human and veterinary diseases, drug discovery, genetic screening, clinical and food diagnostics. According to these approaches the aim of our work is to transfer the methods of the immunological assay from microtiter plates into a microarray format in order to develop a multiparametric, rapid, sensitive and inexpensive method for the the detection of mycotoxins for food safety application.

A microbial receptor protein with carboxypeptidase activity and a D-Alanine sensor were used to design an inhibition assay with electrochemical detectiton. This assay has been developed for the quantitative determination of β-lactam. Optimisation of the inhibition assay conditions allowed us to realise an assay with comparable analytical behaviour than the classical microbiological and other assays. The assay give a detection limit of 1 ng.mL^-1.

In this work a rapid competitive assay for rIgG detection as a fast means for use in routine analysis is presented.

This was achieved by using a micro-analytical flow system (ImmuSPEED™) for rapid and quantitative immunochemical analysis. This is an innovative system which combine a special cartridge (ImmuCHIP™), containing eight polymer microchannels, with a computer-controlled instrument for the control of fluidics. The higher surface-to-volume ratio in the channels and the shorter diffusion distances lead to very low detection limits and short reaction times, whereas the presence of micro-electrodes in each channel allows the direct quantification of the affinity reaction by electrochemical measurement within the microchannel.

In our approach an indirect competitive assay format was performed, by immobilising rIgG onto the surface of microchannels. Then, a sample solution containing an unknown amount of rIgG and a fixed concentration of anti-rIgG labelled with alkaline phosphatase was introduced in the modified channel in order to have the competition. Finally, the channel is filled with the substrate solution (containing p-aminophenyl phosphate 10 mM), and a real time amperometric evaluation of the enzyme kinetic was performed.

All the steps of the immunoassay occurred through hydrodynamic loading of the different solutions through the channels; the speed (µl/min) and duration of the flow, the number of loading step and incubation parameters were optimised, The effectiveness of the system was demonstrated by analysing rIgG concentrations in sample solutions within 5 min. obtaining the same sensitivities as well as in the ELISA tests.

In this work an electrochemical immunomagnetic sensor, based on a direct competitive assay, was developed using magnetic beads as solid phase and carbon screen-printed electrodes as transducers for the detection of sulfonamides. Magnetic beads coated with protein A were modified by immobilization of specific antibodies, then the competition between the target analyte and the corresponding analyte labeled with the enzyme was performed; after the immunosensing step, beads were captured by a magnet onto the working surface of a screen-printed electrode for the electrochemical detection. Screen-printed electrodes (SPEs) were chosen as transducers because they can be easily used in field and their technology allows mass-production at low cost, whereas the use of magnetic beads modified with antibody allowed the simultaneous concentration of the analytes and its separation from other matrix components. Alkaline Phosphatase (AP) was used as enzyme label and Differential Pulse Voltammetry (DPV) as fast electrochemical technique.

Calibration curves demonstrate that the developed immunomagnetic sensor was able to detect sulfonamide compounds in standard solutions at low concentrations (sub-ppb level). The fast incubation time (20 min) and electrochemical measurement (10 sec) make of this system a possible alternative to classic ELISA tests.

Evaluation of the performances of four DNA types was conducted in order to obtain a DNA biosensor for PAHs detection. The variation of the guanine oxidation peak was the analytical signal used to assess the interaction between the analyte and the immobilised DNA. Salmon testis single stranded DNA based biosensor was the chosen device. It was used to evaluated PAHs contamination both in standard solution than in real samples. Using this device an increase of the guanine oxidation peak is observed. Further experimentation on PAHs phototoxicity were also conducted, using BaP as target compound. Results demonstrated the possibility to employ DNA biosenrors as rapid and useful toxicity bioassay.

The aim of the present research was to develop highly selective and sensitive amperometric immunosensors for Atrazine based on a "competitive" assay procedure. To this end three immunosensor devices for the determination of triazinic pesticides based on competitive procedures are therefore described. All the immunosensors developed used an amperometric electrode for hydrogen peroxide as transducer and the peroxidase enzyme as marker. The results show the full validity of these immunosensor methods, which were optimized by comparing three different "competitive" operating procedures. Lastly we compared the results obtained using the new immunosensors with those found using an inhibition OPEE (Organic Phase Enzyme Electrodes) for triazinic pesticides detection, which showed no selectivity toward different classes of triazinic, carbamate and organophosphate pesticides. However the immunosensor developed demonstrated a noticeable selectivity for both different kinds of pesticides and triazinic or benzotriazinic products.

The increasing commercial interest in exploiting the therapeutic value of Lactoferrin as well as HIgG has stimulated the need for reliable assays for their determination. In this study we developed and characterized two screen-printed immunosensors for the determination of antibacterial proteins (Lactoferrin and HIgG), with the aim of suggesting this procedure for routine control. To this end we employed an amperometric screen printed transducer made of platinum electrodes, while the measurement method was based on the formation of a labelled immunocomplex on a suitable membrane overlapping the screen printed electrode, after competitive procedure between antigen and antibody; horseradish peroxidase being the enzymatic marker. Results of this research are continuously compared with those achieved using corresponding more classical custom built amperometric immunosensors.

The sport and anti-doping authorities fear that the newer form of doping, so-called gene doping, based on a misuse of gene therapy, will be undetectable and thus much less preventable. In 2003, the World Anti-Doping Agency (WADA) included for the first time gene doping in their "Prohibited List of Substances and Methods" as prohibited method, defining it as "the non-therapeutic use of cells, genes, genetic elements, or of the modulation of gene expression, having the capacity to enhance athletic performance". DNA-based biosensor approach based on piezoelectric sensing has been applied for the detection of Enhanced Green Fluorescent Protein (EGFP) and Cytomegalovirus (CMV) promoter sequences, used as model systems. Sensor optimization was carried out using synthetic oligonucleotides and application to human DNA was performed.

In this work a label-free genomagnetic electrochemical sensor was developed. It uses as bio-recognition element an oligonucletide sequence which is complementary to a specific DNA sequence. Moreover, the probe have the 5'-extremity modified with biotin, and contain the inosine base instead of guanine. Superparamagnetic microparticles modified with streptavidin were used as solid phase to carry out the analysis with the genomagnetic sensor. Actually, the probe is immobilised on the surface of microparticles by using the streptavidin-biotin interaction, and the affinity reaction with the DNA target occurs by incubating an optimised amount of derivatised microparticles with a fixed volume of sample. After magnetic separation, microparticles are concentrated and treated to release the target, which is finally adsorbed onto the surface of a screen-printed carbon-based sensor and electrochemically detected by the oxidation of guanine and adenine bases.

Experiments were then carried out on synthetic oligonucleotide sequences and afterwards on a PCR amplicon.

Recent advances in nanotechnology have attracted immense attention due to the possibility of creating functional materials, devices and systems by controlling matter at atomic and molecular scales. In this context, nanostructured electrode surfaces show an interesting and technologically important combination of properties such as high surface area, good electrical properties, chemical stability and easiness of miniaturization. In the present work, carbon nanotubes (CNT) and tin oxide nanostructured thin films were designed and tested as candidate electrical genosensors. Self-assembled CNT films were prepared by Chemical Vapor Deposition (CVD). Electrodes based on SnO₂ thin films and nanowires were prepared by RF magnetron sputtering on Al₂O₃ substrates.

Sensors were functionalized using oligonucleotides related to the most common inserts in the GMOs: the Promoter 35S. In particular, this paper describes the development of an enzyme-labelled genosensor using CNT thin films.

This work describes a biosensor for direct measurements of carbon dioxide (CO₂), The functionality of this device was tested by a QMB transducer coated by a liposome containing carbonic anhydrase (AC). During the CO₂ adsorption process a change in the QMB frequency was observed. Another transducer was used in this context. By a high resolution temperature variation transducer, such as the LiTaO₃. It has been possible to detect the heat generated during the reaction CO₂ + H₂O →HCO₃^- + H⁺ occurring inside the liposomes. In this work, the response curves of QMB and LiTaO3 are shown and commented.

The need to support food-labeling legislation has provided a driving force for development of analytical techniques for the analysis of food ingredients. The present work was carried out in view of a possible application in this field: the adulteration of milk and dairy products with milk from cheaper sources. The aim of this study was the development of a rapid and simple optical immunosensor, based on surface plasmon resonance (SPR) technology, for the detection of bovine IgG in adulterated milk samples and the detection and quantification of defined amounts of cow's milk that have been used to adulterate sheep and goat milk.

Gold nanoparticles have been covered with modified amphiphilic cyclodextrins, that are suitable for various applications in biosensing, diagnostics and targeted drug delivery (photothermal and photodynamic therapy). Surface characterization of two kinds of cyclodextrins has been carried out by X-ray Photoelectron Spectroscopy with the aim to investigate the bond between Au nanoparticles and cyclodextrins. Detailed analysis of obtained results revealed that the cyclodextrins are linked to the nanoparticles forming Au - N bond.

A multichannel array for chemical and biochemical parameters has been developed. It consists of a plastic chip formed by two pieces of poly(methyl methacrylate) (PMMA) opportunely shaped in order to obtain several flow channels. The first prototype of the flow cell consists of four channels obtained by combining two PMMA pieces: a lower piece which includes the four micro-channels and the inlet and outlet for the fluidic, and a cover, where the sensing layer is immobilized. The dimensions of a single flow-channel are: 0.5 mm in width, 0.4 mm in height and 18 mm in length. The total volume to fill a single channel is 3.6 µl. Light from a laser is used to excite the fluorescent sensing layer immobilized on the internal wall of the channel. A cylindrical lens is used to optimise the excitation of the immobilised fluorophore. Thanks to the anisotropy of the fluorescence at the interface between the channel and the plastic material, the emitted light travels along the thickness of the plastic cover. The fluorescence coming out from the plastic chip is collected by means of 200 micron optical fibre coupled with a GRIN lens and then is detected with an optical fibre spectrophotometer. The characterisation of the multichannel chip was carried out with the immunoreaction between IgG, covalently immobilised on the PMMA, and the Cy5-labelled anti-IgG which flows in the micro-channel.

Surface Plasmon Resonance (SPR) imaging is a label free method that can be used for the monitoring of the hybridization kinetics between oligonucleotides probes immobilized onto the Au surface and unlabelled complementary targets. In this work an automated SPR imaging-based framework on a PC architecture has been used as an optical biosensor, allowing high reliability real-time analysis of DNA-DNA interactions occurring at the biochip surface.

A portable multifunction amperometric transducer for monitoring bioactive material has been designed, manufactured and tested. It has been specifically designed to operate with a wide range of photoactive biosamples. Each of the two sensing cells in the instrument features two different LED optical sources to detect the photosynthetical activity of plants (i.e. spinacia oleracea) and microrganisms (i.e. algae and cyanobacteria). Target applications belong to the agro-food, pharmaceutical and biomedical fields. In this work experimental determination of common water pollutants is reported by testing water samples of the river Tevere.

In this work, we investigate the responses of an array of carbon black composite polymers to terpenoid vapours. In particular, the devices have shown current intensity changes upon exposure to specific concentrations of terpenoid vapours such as limonene, linalool and geraniol. The hypothesis used in order to qualitatively describe the sensors working mechanism assumes that the polymer swells when exposed to organic vapour and the swelling decreases the connectivity between the conductive filler particles. The filler dispersion, the morphology and the electrical stability of devices have been also evaluated.

This work reports the characterization of a monolayer of four different aminoacids (Tyrosine, Phenylalanine, Lysine and Histidine) chemisorbed onto gold quartz surface piezoelectric electrodes using well-ordered self-assembled monolayers (SAMs) technique.

The contribution of individual aminoacid to binding was investigated using five volatile compounds in the ppm concentration range (vapor (H2O), ethanol, dimethyl benzene (DMB), dimethyl methylphosphonate (DMMP) and Toluene). Piezoelectric quartz crystals covalently modified with aminoacids, were very stable with respect to shelf-life, reproducibility and memory effects allowing to the same electrodes to be used for all experimental analyses. Cross section data approach was applied recording, simultaneously, the signals of 5 quartz microbalance (4 aminoacids and the reference). The synergic action of each aminoacid selectivity was highlighted processing data with Principal Component Analysis (PCA). The PCA scores plot showed a clear quantitative discrimination of gases as well as the contribution of single aminoacid to the detection. The experimental data obtained were correlated to the chemical properties of the aminoacids and the computationally predicted binding scores of aminoacid-gas interaction in order to understand how molecular modelling approach can assist in rationalising the receptors choice.

This work reports results obtained with QCM (Quartz Crystal Microbalance) humidity sensors based on PEDOT-PSS [poly(3,4-ethylendioxythiophene)-poly(styrenesulfonate)] polymer films. The developed QCM sensors have shown high sensitivity, wide dynamic range, good stability and quick response.

A chemical sensor based on Surface Acoustic Wave (SAW) electro-acoustic structure is designed, fabricated and functionally characterized for gas sensing, at room temperature. A SAW two-port resonator integrated on ST-quartz substrate has been used in dual differential mode at resonant frequency of 433 and 915 MHz. Nanocomposite films based on filler of Carbon Nanotubes (CNTs) with nanostructured properties have been prepared by Langmuir-Blodgett (LB) material processing technique to functionalize the surface of SAW devices for vapor detection. The sensing characteristics towards vapors of ethanol, methanol, acetone, m-xylene, and toluene have been measured at room temperature with good performance of the SAW sensor.

Carbon nanotubes (CNTs) networked films have been fabricated by plasma-enhanced chemical vapor deposition system onto alumina substrates, provided with 6 nm thick Co growth-catalyst, for NO₂, H₂S and NH₃ gas sensing applications, at sensor temperature in the range of 100-250°C. Nanoclusters of noble metals surface-catalysts of Au, Pt and Pd have been sputtered on the surface of CNTs to enhance the gas sensitivity. It was demonstrated that the gas sensitivity of the metal-functionalized CNTs gas sensors significantly improved by a factor up to an order of magnitude through a spillover effect. The gas sensing properties of the CNTs-sensors, including the metal functionalized CNTs, are characterized by a change of the electrical conductivity in a model of the charge transfer with a semiconducting p-type character. The metal-functionalized CNTs sensors exhibit high gas sensitivity, fast response, reversibility, good repeatability, sub-ppm range detection limit with the gas sensing properties tuned by surface-catalyst used to functionalize the CNTs sidewalls.

Nanostructured molecular assembly may provide additional peculiar properties not found in other arrangements of the same basic constituents. Among the three-dimensional structures, nanotubes are particularly appealing for chemical sensor applications at least for the expected surface to volume ratio increase. In this paper, the sensing properties of self-assembled nanotubes of oppositely charged porphyrins are investigated for the first time.

The interaction with guest molecules gives rise to changes in the UV-Vis spectrum of nanotubes both in liquid and in solid-state. The optical properties were adequately measured by a simple set-up based on a computer screen as light source and a digital camera as detector.

Porphyrins nanotubular structures exhibited an enhanced sensitivity to various compounds with respect to those shown by the single porphyrins. The reason of the increased sensitivity may be found in an additional sensing mechanisms related to the modulation of the strenght of the forces that keep the nanotube together.

Sensing of light alkanes via chemoresistive gas sensors has been addressed. Screen-printed films of a solid solution of mixed Sn and Ti oxides have been selected for the purpose. We demonstrate that the films sensitively detect 100ppm of such gases and 500ppm of methane, two levels which are by far lower than the alarm limits for these gases. Information about the working mechanism of chemical reactions at surface has been discussed under either dry or wet condition.

The present work is a final dissemination of activities carried out and main results obtained in the national founded project Firb "Square". The project is leaded by Centro Ricerche Fiat and it involves the most qualified national public Research Institutes and Universities active in the fields of nanomaterials synthesis, nanotechnology and gas sensors development.

In this work a novel monocrystalline silicon nanowires array has been investigated and presented as hydrogen sensor, designed and fabricated by employing high resolution microfabrication techniques and featuring a high surface/volume ratio. The nanowires arrays makes up the channel of a MOS system, palladium-silicon dioxide-silicon.

Several devices have been fabricated by using a SOI (Silicon On Insulator) substrate. Source and Drain have been geometrically patterned by optical lithography and Boron p-doped. Electron Beam Litography (EBL) defined the MOS channel made up of a nanowires array of different length and width in different transistors. The pads of Source and Drain have been manufactured with an aluminium film deposition. The Gate has been fabricated with a grown silicon oxide layer (17.4 nm) and Palladium has been used as gate contact. Polarizing and exposing the device to H₂/N₂ cycles at different concentrations some preliminary measurements have been successfully conducted.

Sensing devices based on ZnO films deposited by RF sputtering have been investigated. Their sensing properties have been found dependent on film deposition parameters and post-deposition treatments such as thermal annealing and sensor working temperature. The fabricated sensors were found suitable for automotive applications in the control and prevention of CO contamination into the vehicle cabin and detection of hydrogen combustible gas leaks in fuel cell cars.

In this work, we report on the electrical response of hydrogen sensor based on palladium nanowires array. Stability and selectivity are investigated at room temperature, in presence of 4% hydrogen concentration in nitrogen. Measurements show a clear stability of the devices in a few months and no interference by a variety of gases as well as relative humidity.

Nanostructured semiconductor gas sensors are notoriously very sensitive to a huge number of environmental parameters, such as humidity and ambient temperature. It can be noticed that even if we keep the film temperature constant through an electronic feedback, variations of the ambient temperature lead to conductance variations. In this work we try to understand the nature of this dependence. In order to study the correlation between the response and the temperature of the film, of the air near the film and of the ambient temperature a thermal exchange mathematical model has been developed. A simple experimental configuration has been taken into account, with the heated film placed inside the protection cap, the whole sensor inside the test box and the test box subjected to environmental temperature, and the model was solved numerically and compared with the experimental data.

This paper introduces some preliminary consideration on non uniform resistance changes in silicon square photoconductors resulting when the surface exploration is made by small spot laser light. These results seem to be similar to those obtained from a chemically sensitive material such as, for instance SnO₂ left in air at a suitable temperature, for which the resistance decrease in presence of CO. A simple theory is considered for the determination of the approximated overall resistance value of a thermistor (or chemically sensitive thermistor) on the basis of sensitive sites localization.

We show that the efficiency of the red photoluminescence band of tin dioxide (SnO₂) nanobelts is quenched upon controlled adsorption of nitrogen dioxide (NO₂) molecules at sub-ppm concentration level, while it remains stable upon exposure to other polluting inflammable gases. In order to clarify the origin of this phenomenon, which may be of great interest in order to improve the selectivity of solid-state gas sensing devices, analyses are performed in controlled adsorption conditions by means of continuous wave and time-resolved photoluminescence. Adsorption of NO₂ molecules obeys to a Langmuir kinetic and leads to a decrease of the photoluminescence yield without affecting the lifetimes of radiative states. These findings support a picture in which photoluminescence quenching results from suppression of radiative states through interaction with NO₂ molecules acting as "static" quenchers. A simple model based on the above mechanism and allowing good fitting of the data is described and discussed. As the state of art on red luminescence in SnO₂ underlines the role of oxygen vacancy states, these results thus encourage investigation on oxygen-deficient SnO₂ nanobelts as selective optical gas sensors. Understanding the basic mechanisms governing the photoluminescence (PL) activity of SnO₂ NBs may represent the key to tailor their possible applications as optical nanosensors. It is commonly accepted that oxygen vacancies (OVs) play a key role and govern the optical activity of SnO₂ NBs. However, theoretical studies confirming such finding are lacking. We present a density-functional calculation of the electronic properties of SnO₂.

It is well known by far that biological organisms could arrange themselves in sophisticated and complex structures, which compete or overcome the top technology products available and which exhibit peculiar optical behavior. In recent years, the porous silica structures (frustules) created by living diatoms are under study for several nano-engineering applications based on bio-mimetic approaches. The diatoms are microscopic algae enclosed between two valves of hydrated amorphous silica. They spontaneously arise in every aquatic environment. More of 104 types of diatoms have been discovered and classified by different shapes of their cell walls. These intricate structures, called frustules, show symmetric patterns of micrometric and nanometric pores. Due their peculiar structures and large variety of morphologies, a widespread interest about diatoms and their possible use in nanosciences and nanotechnology has growth. They strongly emit in the visible range when pumped up by UV radiation and their photoluminescence, in virtue of their high surface-to-volume ratio, is strongly affected by changes of the surrounding atmosphere. Frustules belonging to different families were exposed to various chemical species in order to test their reactivity to different polluting gases. Different species of diatoms were found to exhibit different relative responses and different gas concentration ranges of sensitivity, depending on the morphology and porosity of their frustules. Due to the large variety of dimensions, porosities and surface morphologies available in nature, these materials appear to be promising to improve the selectivity of gas sensing based on photoluminescence optochemical transduction.

Innovative hydrogen sensors based on Kelvin Probe operation principle and on MEMS technology have been designed and fabricated, on the basis of a previous study and process dedicated to the manufacture of electro-statically actuated RF MEMS capacitive switches. Many factors can influence the work function difference, including adsorption or desorption of volatile compound molecules depending on the sample material. The innovation proposed consists in the use of an integrated Kelvin capacitor, featuring a fixed Palladium plate and a mobile Au plate, as a gas chemical sensor to monitor the concentration of hydrogen over time with a very high accuracy by detecting changes in the work function difference balance condition.

One of the main research topics at the Olfactometric Laboratory of the Politecnico di Milano is the study and the development of a system for the continuous monitoring of environmental odours at specific receptors. The first part of this work resumes a set of laboratory tests conducted with the aim of selecting an array of chemical sensors and their optimal operating conditions, whereas the second part of the work describes the experimental approach adopted for a field test, which consisted in the application of an electronic nose for the continuous monitoring of odours from a MSW landfill. The results of the laboratory tests enabled to evaluate the detection limits of a set of MOS sensors towards some environmentally important gases, and therefore to identify an optimal combination of sensors and operational conditions. Finally, the results of the field test show how an opportunely trained electronic nose can successfully be applied for the determination of the odour impact of a MSW landfill.

In many countries, fuel adulteration poses a serious problem in terms of environmental damage, fiscal frauds, and engines lifetime reduction. A practical example is Brazil where the major fraud is the addition of alcohol at a percentage higher than that established in accordance with the law. In this work, a methodology for fuel quality control based on mass and capacitance transduction of organic sensing layers is illustrated and commented. Preliminary results indicate the possibility to detect the presence of different contaminants and, in particular, to estimate the ethanol content in gasoline with an accuracy enough identify adulterated fuel in the Brazilian context.

This work points out the ability of the electronic nose to detect the presence of unburned diesel in engine oil, in comparison with standard methods based on distillation or gas chromatography. The system is based on an array of different gas micro-sensors whose sensitive layers are metal oxide thin films deposited by sol-gel technique on Si substrates. The sensor array, exposed to the volatile chemical species of different engine oil samples contaminated by diesel fuel, resulted to be appreciable sensitive to detect the fuel contamination. The results of Principal Component Analysis, used as exploratory data analysis technique, and the success rate of the classification, based on Gaussian mixture model, prove the good performance of the system in discriminating different diesel fuel diluted lubricating oil samples.

Interdigitate capacitive sensors are promising devices for gas sensing in terms of fabrication costs and ease of integration. The aim of this study was to investigate a novel arrangement of interdigitate capacitorsfor air quality monitoring with high sensitivity and resolution, using low cost devices at room temperature.

The system is fully controlled (through audio device board) by a personal computer which feature represent a great advantage in terms of cost, versatility and ease of use. The paper will describe the characteristics of the interdigitate capacitors, the electronic system and experimental results.

Impedance cell-based biosensors are playing a key role in today's miniaturized cell cultivation systems thanks to their sensitivity, efficiency and high level of automation. In this work, a micro sensor with an interdigitated electrode structure is used to monitor impedance changes associated with wine yeast growth. The goal is to monitor cell proliferation in presence of alcohol more quickly and objectively with respect to the traditional ethanol resistance assay. In spite of the existing techniques in the field of electrical biosensors, a new approach with solid agar medium is performed. The device shows an increment in impedance magnitude in concomitance with yeast cell growth. This impedance-based biosensor could follow cell growth at different ethanol concentrations, providing a reliable contribution to the common experimental practises.

We present a microfabricated device for the selective manipulation and separation of cancer cells from normal cells using dielectrophoresis technique (DEP). The device was designed to perform both vertical (positive/negative DEP, p- and n-DEP) and lateral (travelling wave DEP, Tw-DEP) cell motion and cell detection by means of electric impedance measurements. A technological fabrication process was defined. The device consists on a pair of interdigitated gold electrode arrays on a quartz substrate and a microfabricated three-dimensional structure for cell confinement. To improve the device biocompatibility a nanostructured TiO₂ film was deposited on it by supersonic cluster beam deposition (SCBD) technology. The dielectrophoretic effects of the chip were initially tested using polystyrene beads. We obtained the separation of different sized beads. The biocompatibility and cell movement capability of the device were performed using NIH/3T3 fibroblasts. Vertical and lateral motions of these cells were observed.

Breath analysis is a non-invasive procedure for the potential diagnostics of a broad range of medical pathologies which could be easily performed at clinics and doctor rooms. The development of a breath analyzer based on MOS sensors and designed for this scope is here described. The developed analyzer should replace and improve the analytical procedures so far performed with conventional techniques (e.g. GC-MS) which are generally expensive and time consuming and therefore not suitable for routine analysis in clinical environment.

In this work we investigate the physical behaviour of various form of carbon nanoparticles in aqueous environment. The role of dissolution and the evolution of the aggregation state of MWCNTs, SWCNTs functionalized with water soluble polymer and carbon black nanoparticles in a PBS solution (Phosphate Buffered Saline) has been investigated. Nanoparticles solution were periodically checked for dissolution, with absorbance measurements, and DLS analysis. The different aggregation kinetics have been observed and discussed in terms of their possible toxicological role. Results showed that carbon based nanoparticles have a strong tendency to aggregate in aqueous environment. Even the water soluble SWCNTs aggregate in aqueous solution. In fact, within 24 hours small and/or solubilized particles disappear from solution and around 700 nm average particles are formed.

Miniaturized integrated antennas are essential to the implementation of novel intelligent systems for wireless communication, RFID, biosensors and other related applications. The on-chip antenna concept is the actual trend in integrated wireless sensor systems because it is a practical solution to compact, small size and low cost devices for short range applications, like RFID tags and biomedical sensor data transmitters. Rapid scaling of low cost CMOS technology has enabled circuits and systems to operate into the micro/millimeter wave frequency band, where the required antenna size shrinks and makes the implementation of an on-chip antenna feasible. An on-chip antenna (OCA) represents a possible solution for a fully integrated wireless system with no off-chip components, paving the way to new unexplored applications, such as miniaturized sensors for biomedical applications. This paper explores some different geometries of integrated antennas in a 0.35 µm CMOS technology for devices operating in the internationally available unlicensed 2.4 GHz band (Industrial, Scientific, Medical band).

We here present a very low voltage (±1V) current mode integrated circuit for the read out of heart rate operating frequency with the purpose of performing heart tests on the human person. The whole circuit has been designed in a standard AMS 0.35µm technology.

Waiting for the complete integration, a prototype board has been implemented using commercial components. Test results are in agreement with those obtained from other classical commercial instruments.

Working on the single cells represents an important step for the study of living organisms, so that several new technologies and methodologies have been developed in these years with this aim. In this work we show an accurate equivalent electrical model of the interface between a living cultured cell and a biochip consisting in an array of microelectrodes. By coupling it with electrochemical impedance spectroscopy (EIS) measurements, it is possible to quantitatively correlate cell health and membrane morphology by using.

There is today a growing up interest in proton therapy for tumors treatment, because these particles permit to tightly shape the dose to the target. Anyway, the spatial accuracy of proton therapy is limited by the uncertainty in stopping power distribution, which is calculated from the photon attenuation coefficients measured by X-ray tomography. A proton computed tomography apparatus (pCT) could be used to directly measure stopping power and reduce this uncertainty. Single proton tracking is a promising way to face difficulties due to multiple Coulomb scattering. The design of a proton radiography (pCR) prototype and its practical realization are described in this paper. The prototype is based on a silicon microstrip tracker to characterize particle trajectory and on a segmented YAG:Ce calorimeter to measure their residual energy. The aim is to detect protons with initial kinetic energy K = 250-270 MeV and with a particle rate of ~1MHz. This prototype is the first step toward the design of a complete pCT system to measure tissue electron density with an accuracy better than 1% and with a spatial resolution better than 1 mm.

In this paper, we present an innovative physical sensor interface based on neural network that allows an electronic music composer to plan and conduct the musical expressivity of a performer. For musical expressivity we mean all those execution techniques and modalities that a performer has to follow in order to satisfy common musical aesthetics. The proposed sensor interface is composed by a gestural transducer, that measure motion acceleration and angular velocity, and a mapping module, that transform few physical measured parameters into a lot of specific sound synthesis parameters. It is able to transform six physical input parameters in seventeen sound synthesis parameters. In this work, we focus our attention on mapping strategies based on Neural Network to solve the problem of electronic music expressivity.

In this paper, a new kinematic sensor is presented, which performs the detection of incipient pathologies in human beings by means of the analysis of the sit-to-stand locomotion task. The sensor is based on the frequency analysis of acceleration measurements supplied by a homemade transducer and on the exploitation of some of the most effective classification strategies at this time. Results show the capability of distinguishing between pathological and non pathological subjects.

Mechanical resonance was contactless excited and detected in conductive nonmagnetic structures to be used as sensors without the need for external magnets, or electrical connections to the structure to supply current lines. An external coil generates a magnetic field at frequency f that induces eddy currents in the structure. The interaction between the eddy currents and the magnetic field itself causes Lorentz forces at frequency 2f that can set the structure into resonance. An additional dual-coil arrangement applies and senses a probing magnetic field at higher frequency and exploits it to measure the resonator vibrations. The principle was tested on millimeter-size metallic beams, obtaining operation distances in the order of 1 cm and values of the resonant frequencies in agreement with measurements taken by an optical system. The resulting resonators can be used as passive sensing elements for a variety of quantities, being especially attractive for harsh and inaccessible environments.

This work presents a novel approach for developing high density tactile sensing arrays for the fingertips of humanoid robot. Each touch sensing element or 'taxel' comprises of piezoelectric polymer film acting as transducer and directly deposited on the FET devices in the array. The tactile sensing arrays have been designed to have 25 touch sensing elements placed 1mm (center to center) away from each other thereby achieving the spatial resolution close to human fingertips. The size of each touch element is 0.5mm × 0.5 mm. The feasibility of the approach was studied by developing piezoelectric polymer-MEA (microelectrode array) based test chips - each comprising of 32 'taxels' (tactile elements) epoxy-adhered with a piezoelectric polymer (PVDF-TrFE) film. The experimental results from these tactile sensing arrays have also been presented.

Polycrystalline thick diamond samples were selected for this work. Silver deposits were made on both faces of the sample to perform measurements in sandwich configuration. Studies in pulsed mode were performed by using a commercial Amptek Cool-X source, constituted by a LiTaO₃ pyrolectric crystal and a copper target window. Pulse height distributions were carried out with a charge-sensitive preamplifier Ortec 142IH and a digital pulse processor multi-channel analyzer PX4 by Amptek. The detector is able to resolve two characteristic lines (Cu K_α and Ta L_α) only 90 eV apart: this feature suggests very good energy-resolving capabilities for X-ray spectroscopy.

In this work, we present a pressure sensor based on surface acoustic wave (SAW) resonators operating in the pressure range from 0 to 3 bar. The sensing mechanism is related to changes in the elastic constants of the substrate and, hence, in SAW phase velocity, induced by the applied pressure. In order to determine the radius of the membrane, we used a finite element method (FEM) program, using the elastic constants of the anisotropic ST-x quartz. A differential configuration has been designed to reduce parasitic phenomena due to temperature variations. The SAW elements are two 2-ports resonators operating at approximately 393 MHz and opportunely positioned on the designed circular diaphragm. SAW resonators are used as frequency-control element in the feedback branch of a Pierce oscillator circuit. The frequency shifts of the oscillators, as consequence of pressure variations, are easily measured and reported. A resolution better than 4 Pa and a linear response curve are obtained.

Moving object detection starting from a video sequence is a fundamental task in many computer vision applications, such as autonomous robotics, traffic control, driver assistance and surveillance systems. In this paper we propose a method, based on stereo vision, that improves separation ability. Two image sequences of the same scene are taken using two cameras with slight horizontal displacement. Stereo processing of these sequences gives both detection of movement and depth information, which can be used to distinguish moving objects with different distance from the observer. Information on the distance of a given point of the image can be useful in presence of moving objects appearing close in a 2D image but with different distances from the observer.

A very compact integrated flow meter for liquids is presented. An original and low cost package method, compatible with standard electronic chip packages, is proposed. The experimental characterization demonstrates that the sensor is suitable for detecting liquid flow rates of the order of a few ml/h, with dynamic range of 1:100, making it a good candidate for biomedical application such as maximal dose controllers in drug delivery systems.

The frequency response of thermal gas flowmeters fabricated by means of two different commercial CMOS processes has been investigated. The device are based on a standard differential temperature configuration with a heater placed between two temperature probes. Thermal insulation from the silicon substrate has been obtained by applying a simple postprocessing technique. A dependence of the frequency response on dielectric thickness has been found in the investigated frequency range.

A new multisensor for three of the four ambient variables of thermo hygrometric comfort has been realized, based upon the thermal and fluid dynamic behaviour of a flat heated surface, in transient state. The sensor is made up of a glass substrate with a gold layer deposited on it, used both as heater for current flow though it and as temperature sensor. Air temperature is measured while current is so low to don't produce self heating, while during the first seconds of heating convection heat transfer coefficient is evaluated, and from it air velocity is measured. Finally, mean radiant temperature is measured from the difference between the heat transfer coefficient results of the two part of the sensor: one blackened and another bright as after gold deposition. Test showed good accuracy in determination of the temperature and the other quantities.

We present the first results of long-term monitoring of temperature profiles at the Campi Flegrei caldera (Italy). The measurements were carried out along a 76 meters-deep borehole already equipped with a borehole strain-meter. We installed a cable containing a loop of optical fiber in order to use a fiber-optics distributed sensor based on stimulated Brillouin scattering. The obtained data are consistent with results of both deep and surface geothermal explorations and indicate that geothermal gradient can be efficiently measured and monitored by the proposed technique.

We propose and experimentally validate the use of a distributed optical fiber sensor for monitoring pipeline dislocation. The proposed technique is based on the measurement of the normal strain, by use of stimulated Brillouin scattering, along three longitudinal directions running along the pipeline. We demonstrate that, by choosing the three lines being reciprocally displaced of 120 degrees around the circumference of the pipeline, it is possible to measure the amount and direction of pipeline dislocation. The longitudinal position at which the deformation occurs is also evaluated. Numerical simulations carried out by finite-elements method have been employed to evaluate the accuracy of the measurements.

The growing need to control ultrafine particulate emission from combustion sources is driving the efforts in developing new methods for probing nanoparticles in the exhausts as well as within the flame environment. Optical methods are the most desirable to this aim being the less intrusive, furthermore the development of user friendly ultra-fast laser sources and detectors is forcing the application of new methods for combustion diagnostics. In this paper, the first application of Time Resolved Fluorescence Anisotropy for in situ measurements of fluorescent nanoparticles produced in flame is presented. Visible fluorescing particles with mean size of 8-9 nm have been detected and the capability to follow their growth with the height above the burner has been demonstrated.

A collection of lubricant oils from different types of turbines, which were characterized by different degrees of degradation, were analyzed by means of UV-VIS-NIR absorption spectroscopy, fluorescence spectroscopy, and scattering measurements. All these measurements were performed by means of optical fiber-based instrumentation that made use of LEDs or compact lamps for illumination and miniaturized spectrometers for detection. Multivariate data analysis was used to successfully correlate the wide optical spectral signature of oils to some of the most important parameters indicating the oil's degree of degradation, such as TAN, JOAP-index, water content, and phosphorus.

Fluorescence spectroscopy carried out by means of optical fibers was used for the rapid screening of M1 aflatoxin in milk, enabling the detection of concentrations up to the legal limit, which is 50 ppt. A compact fluorometric device equipped with an LED source, a miniaturized spectrometer, and optical fibers for illumination/detection of the measuring micro-cell was tested for measuring threshold values of AFM1 in pre-treated milk samples. Multivariate processing of the spectral data made it possible to obtain a preliminary screening at the earlier stages of the industrial process, as well as to discard contaminated milk stocks before their inclusion in the production chain.

Compact spectrometers are useful in most applications where measurements are performed out of the laboratory. A typical example is the spectrometry for planetary missions in which small and low-weight instruments are required.

The optical sensor described here allows building up a miniaturized multispectral spectrometer, with no moving parts. This sensor is obtained by combining a two-dimensional array detector (CCD) with a dedicated optical filter which transmittance changes along the surface of the filter itself. The range of operation, from ultraviolet to infrared, depends on both filter and detector characteristics. Classical optical elements such as prisms and gratings are avoided and overall dimensions strongly reduced.

In this work we present the development and the characterization of a liquid sensor based on peak-type operation for Metal-Cladding Leaky Waveguide (MCLW). The device is fabricated using polymeric materials (PMMA) and it is suitable for measuring small changes in refractive index of a solution covering its surface. The sensor exhibits a good sensitivity and offers the advantage that the sensing mechanism is based on changes of the angular position of a narrow peak, rather than changes of a broad dip as in Surface Plasmon Resonance based sensors.

Electro optical absorption in hydrogenated amorphous silicon (α-Si:H) – amorphous silicon carbonitride (α-SiC_xN_y) multilayers have been studied in two different planar multistack waveguides. The waveguides were realized by plasma enhanced chemical vapour deposition (PECVD), a technology compatible with the standard microelectronic processes. Light absorption is induced at λ = 1.55 µm through the application of an electric field which induces free carrier accumulation across the multiple insulator/semiconductor device structure.

Hydrogenated diamond surface is characterized by a negative electron affinity which induces an upward band bending and the formation of a hole accumulation layer. Hole density and mobility values are largely affected by the surface morphology, as well as by the amount of surface adsorbates. Such a film surface is used for the realization of large area field effect transistor (FET) structures for chemical sensing applications. In this context, we report on the realization of FET structures based on layered grown polycrystalline diamond, using different metals as gate electrodes. Our results clearly show that such films, when hydrogenated, can be suitably employed for the realization of interface controlled field effect sensors, where channel conductivity can be modulated by the surface potential established either by a metal or electrochemical gate electrode.

In this work, chemical sensors and biosensors, assembled with nanomaterials, are presented. In particular, the chemical sensor prototype, based on carbon nanotubes, selectively detects epinephrine in presence of ascorbic acid. The second analytical approach is a glucose amperometric biosensor based on nanocomposite materials. This method gives the possibility to synthesise nanostructured polymeric films acting as diffusion barrier toward the glucose oxidation, resulting in an extended linearity useful in diabetes field. Nanomaterials could be also applied in the Cultural Heritage for cleaning of stone surfaces. Recently, considering the mass production and the environmental diffusion of nanomaterials, a new trend related to the nanotoxicology has been considered. In this work, preliminary results suggesting a response of autonomic cardiac regulation after instillation of SWCNTs might be useful for identifying the pathophysiologic link between exposure to nanoparticles and acute adverse cardiac events.

In this work, we present experimental and numerical results relative to polarization-resolved reflectivity spectra of micromachined one-dimensional photonic crystals (1D-PCs), evaluated in the near-infrared region at both normal and non-normal incidence. The microstructures, fabricated by electrochemical deep etching of silicon, are hybrid quarter-wavelength PCs consisting of arrays of silicon walls, separated by air gaps, with thickness of 1.22 µm, period of 4 µm and aspect ratio up to 100. The spectral distribution of the photonic band gaps, measured in the wavelength range 1.1–1.7 µm, is in agreement with the theoretical calculations, obtained by using the characteristic matrix method. Furthermore, a theoretical Montecarlo analysis, carried out to take into account technology-induced errors on the fabricated 1D-PCs, allows to obtain a better matching between experimental and calculated reflectivity spectra.

Herein Ink Jet printing technique is described for functional materials deposition. As a concrete application we report on the production and characterization of an all printed device for sensing applications, where piezoelectric printheads have been used to deposit, in opportune drop sequences, conductive Ag ink for the interdigitated electrodes and polystyrene/carbon black based ink for the sensing layer.

Powered exclusively by an on-board antenna, a 13.56-MHz smart RFID tag with a temperature sensor is presented, based on a SMD ultra low power microcontroller. The PCB integrates an on-chip coil connected to a power reception system and an emitter/receiver RFID module made with a general purpose 8-bit microcontroller. In this work a perfectly repeatable technique to build wireless sensor devices that operate with RFID standards at 13.56 MHz has been achieved, tested with a 10 kΩ Negative Temperature Coefficient (NTC) sensor. This is a practical solution to obtain compact, small size and low cost devices for short range applications, like RFID tags with biomedical sensor data transmitters. The microcontroller ensures a low-cost alternative for achieving high-end features such as bi-directional communication, anti-collision and on-board computational power especially for acquisition systems.

A wide range of Wireless Sensor Network (WSN) applications are event-driven, therefore event detectors are a crucial component that ought to furnish opportune and reliable event estimations. Particularly, event detection computing demands from sensor nodes intensive signal processing tasks. Rather, the wireless sensor platform resources are limited and can not execute efficiently complex signal processing algorithms. Moreover, available radio chips can not transmit into the communication channel large amounts of raw sensor data.

In this paper the development of a lightweight event detector for acoustic events is presented. Threshold-based event detection methods require, on one hand off-line time consuming parameter tuning processes, and on the other hand the detector execution should perform continuously energy expensive point-to-point comparisons. As an alternative, we compute events occurrences, on the change of rate of the sum of the signal energy average plus the energy standard deviation at two separated time instants. Our approach works, under the assumption that for long time periods of unknown signal energy noise background levels, the rate slope will present flat or stable behavior, and it will experiment noticeable changes under sudden signal energy level changes for brief time instants. The detector reactivity is presented as function of two parameters: a) the change of rate slope tolerance and b) the time distance length among consecutive slope rate computations.

A very efficient localization system, capable to localize multiple identical sensor nodes (SNs), based on mixed acoustic and radio frequency communication is proposed. The remote devices are identical in the sense that each remote device emits signals that are indistinguishable from each other, i.e. there is not any identification code. A set of beacons emits a sequence of acoustic pulses in the space region containing the sensor nodes. When impinged by the acoustic wave front, each sensor node, independently from each other, sends back a radio frequency (RF) acknowledge signal to a central information processor (CIP) or radio base. The radio base, knowing the positions of the acoustic beacons and the time of arrival of the acknowledge signals, computes the positions of the sensor nodes with a suitable algorithm, identifying and discarding possible false signals due to echoes and environmental noise.

The on-chip antenna concept is the actual trend in integrated wireless sensor systems because it is a practical solution to compact, small size and low cost devices for short range wireless applications, like RFID tags and biomedical sensor data transmitters and other related applications. Rapid scaling of low cost CMOS technology has enabled circuits and systems to operate into the micro/millimeter wave frequency band, where the required antenna size shrinks and makes the implementation of an on-chip antenna feasible. An on-chip antenna (OCA) represents a possible solution for a fully integrated wireless system with no off-chip components, paving the way to new unexplored applications, such as miniaturized sensors for biomedical applications. In this paper an improvement of a wireless temperature sensor with on-chip antenna is proposed. This new solution uses the same principle, based however on a double ring oscillator structure, transforming the silicon substrate temperature variation into a frequency modulation. The design is realized by means of 0.35 µm CMOS technology. This new chip works at about 2.4 GHz frequency (instead of 750 MHz of the oldest), improving the antenna efficiency. The signal is transmitted by a small loop antenna structure which is realized by aluminium deposition on the top surface of the chip.

It is well known that many people need to ask for medical assistance because of infections contracted through foods and for other health disorders got from improper storage methods or packaging. To reduce the occurrences of this kind of diseases, it is under design a miniaturized system capable of monitoring some of the physical parameters useful to track the environment conditions where packaged food is stored before reaching the point of sale.

Energy harvesting or energy scavenging systems (e.g. piezoelectric, electrostatic, electromagnetic, solar cells, etc.) have raised in the last years an increasing interest to their use as power supply sources for electronic systems, particularly for wireless devices. The use of such systems, furthermore, is the key in environments where batteries cannot be used, e.g. tire of an automobile. The goal of our work is to design and implement an integrated power management system to optimize the power/energy transfer from the energy scavenging device to the power supply of an embedded smart wireless sensor. We focus our research activity on vibration-based energy harvesting generators, in particular on thin film piezoelectric cantilevers. In this work, we present the results of the on the road experimental tests, made with a Piezoelectric Bender Generator (PBG), mounted on a board, in turn, mounted onto the wheel of a car. With our work we assess the feasibility of using PBGs as power supply source of Wireless Tire Pressure Measurement Systems (TPMS).

Nowadays there is a renewed interest towards the development of innovative energy production devices for small consumption, to be used in harsh environments whose added value could be a very long operative lifetime (i.e. aerospace, medical, portable electronics). The exploitation of energy contained in long half-lives radioactive sources using a stable, resistant solid-state converter material like diamond could be an appealing solution. Diamond is a wide band-gap semiconductor characterized by exceptional physical properties and represents the appropriate material for applications involving the use of intense beams of high-energy (hv) radiation and electrons. At present we are designing devices for the conversion of high-energy radiation into electrical power. Specifically, the efforts are focused on the interaction between diamond and beta particles, which can be accurately simulated by an electron beam produced by a SEM system. The research activity is centred on designing and optimizing vacuum secondary-electron-emission (SEE) converters and probing the maximum obtainable energy conversion efficiency. The experimental results indicate values close to 1% for electron beams of 1 keV and about 0.4% at 1.5 keV.

Wireless Sensor Networks (WSN) are composed of battery supplied nodes. Since the battery depletion is a process that can not be stopped, WSN designers need to know in advance when batteries would be exhausted in order to make the estimation of application lifetime. To this aim, in this work we present an electronic system based on a dedicated PCB that allows users to visualize node current consumption usage and charge extracted from the battery during wireless sensor node operating modes.

In order to perform experimental evaluations we selected benchmarks that represent usual tasks in WSN applications and results are presented and discussed.

Recently many events occurred in the energy scenario: the most noteworthy among them are that EU confirmed its policy against climate change and the fully completion of the liberalization of the EU power market. Both these events lead to a change not only for industries but also for end-users, demanding for a different role: from passive consumer to active customer. Energy efficiency is considered as one of more proficient way to reach Kyoto Protocol targets, but efficient devices on their own are not sufficient to gain significant energy conservation. Several efforts toward development of cheap, affordable and easy-to-use sensors for energy management purposes are taking place, some driven by the European Commission. This paper will provide a description of the state-of-the-art and potential exploitation of sensors, and their future improvements, in energy management systems.

This paper describes an innovative pre-discharges detection system, developed to improve distribution network reliability. The assembled system includes optical sensors, based on different detection principle able to measure with high sensitivity the induced effects of pre-discharge phenomena, such as ignition of light, production of acoustic noise. Preliminary tests performed in a laboratory mock-up simulating pre-discharge phenomena arising during real operating condition confirmed the feasibility of the proposed approach. The obtained results are discussed in comparison with data simultaneously acquired with the standard partial discharge method.

When a thin layer of salt (NaCl) covers the surface of an high voltage insulator, the insulators flashover resistance capability can strongly be reduced by the presence of moisture in the air. To prevent possible electric power outages caused by particular weather conditions, remote inspection techniques capable of detecting small amounts of salt on the insulators have to be developed. We describe some preliminary results relevant to the utilization of a LIBS system for the analysis of salt contaminated samples.

We describe an innovative laser based scanning system properly conceived for monitoring both the ice accretion rate and the conductors sag in high voltage aerial electric lines. Preliminary results relevant to laboratory tests will be presented.

An oscillator circuit is proposed that simultaneously excites and tracks two harmonic resonances in a quartz crystal resonator (QCR) sensor. By probing the resonator at two harmonic modes at the same time, enhanced sensing capabilities can be conveniently achieved because a larger set of parameters can be measured with a single sensor. The circuit also provides compensation of the sensor parallel capacitance for increased accuracy. The oscillator was tested with 5-MHz AT-cut crystals simultaneously operated at the fundamental and third harmonic in contact with solutions of different density-viscosity products. The results show an excellent agreement between the oscillator readings and reference measurements taken with an impedance analyzer.

This paper presents a complete gas-sensing system which consists of a wide-dynamic-range interface circuit able to operate without calibration and of a high-efficiency temperature control loop with a switching heater based on a custom digital control logic. The gas-sensing interface circuit is based on resistance–to-frequency conversion and achieves, without calibration, a precision in resistance measurements of 0.5% over a range of 4.6 decades (dynamic range, DR=138 dB). The temperature control loop is driven by a digital set-point and the simulations results show that it controls the temperature of the sensor over a range of 250 °C with an accuracy better than 0.3 °C. The temperature control logic is reconfigurable and can be used to control the temperature of sensors with different baseline resistance value and different sensitivity. All voltage references are reconfigurable and on-chip buffered.

An integrated readout circuit for Lab-on-a-Chip applications is presented. The overall system consist of a 640 × 480 array of capacitor sensors and actuators. Usually for this kind of applications an off-chip analog-to-digital converter is used. As a consequence, the noise floor increases and high signal-to-noise ratios are difficulty achieved. On the other hand, these applications requires a stringent noise floor specification (>10b) and a relaxed linearity (≈8b). The complete sensor readout channel is composed by two main blocks: a pre-amplifier with programmable gain and an algorithmic analog-to-digital converter with a 1.5-bit/stage architecture. In order to save chip area and power consumption a time sharing technique has been taken into account using a single operational amplifier for the pre-amplification stage and the conversion stage. The proposed A/D converter has 11b resolution, a sampling rate of about 100ksample/s and an input full-scale range of 1.2Vp-p differential. Simulation results show a SNR = 65.7 dB and an ENOB value of 10.6b. Its power consumption is about 150µW. Readout chain is implemented in 0.35µm CMOS technology with a 3.3V supply voltage.

In this paper we propose a novel front-end, based on low voltage (LV) low power (LP) Second Generation Current Conveyors (CCIIs), for wide range resistive sensors, able to evaluate the resistive behaviour of the sensing element without any preliminary calibration. This interface operates a resistance-to-period (R-T) conversion exciting the sensor with a DC voltage and is able to reveal, for more than four decades of variation, both high and low resistive values. Post-layout simulations, conducted on the designed integrated solution, and preliminary experimental results, obtained using a commercial sensor (FIGARO TGS 2600) and AD844 as CCII, have shown high linearity and good agreement with theoretical expectations.

In this paper we present a new low voltage (1.5V supply) low power (750µW) capacitive sensor interface, based on a square wave oscillator implemented with a single second generation current conveyor (CCII). Complete theory calculations are addressed. Simulation results, obtained by means of Cadence simulator, are in a good agreement with theoretical expectations. Since the CCII has been implemented at transistor level, in a standard CMOS technology, the proposed sensor interface circuit can be completely integrated. The sensitivity of the conversion capacitance-oscillation period obtained from simulations is about 3ns/pF.

In this paper we propose a novel high precision current-mode instrumentation amplifier (CMIA), employing two second-generation current conveyors (CCIIs), which shows many advantages when compared to conventional differential architectures, for smart sensor system applications. In particular, in the proposed CMIA, the dynamic element matching (DEM) approach has been applied to a suitable CCII. This technique has allowed to decrease circuit offset due to mismatch of few components by dynamically interchanging them and averaging with a low pass filter, so avoiding any kind of CCII pre-calibration for offset compensation. Simulation results have demonstrated the validity of the present approach, in particular in sensor interface to increase system sensitivity.

In this paper we propose a novel fully-integrable oscillating circuit for the interfacing of high-valued Metal Oxide (MOX) resistive gas sensors, using a reduced number of active blocks. The proposed front-end employs only three Operational Amplifiers implementing a square wave oscillator whose output period is proportional to sensor resistance value. Through the use of an AC sensor excitation voltage, the circuit is able both to reveal typical resistive values of MOX gas sensors, which can vary from 100kΩ up to tens of GΩ, and to estimate also the parasitic capacitance in parallel to the resistive sensor (in the order of few pF). Preliminary experimental results, performed through a discrete component prototype and sample resistors, have shown high linearity and reduced percentage error (lower than 10%), compared with theoretical expectations.

We present a novel integrable Op Amp-based resistive sensor interface, performing a Resistance to Period (R-T) conversion and using a DC sensor excitation. The proposed circuit, based on an oscillator topology, is able to reveal more than four decades of high resistance variations (from about 1MΩ to more than 10GΩ), typical of some resistive gas sensors (e.g., metal oxide, MOX, sensors), avoiding the estimation of the sensor parallel capacitive component (in the order of few pF), since a DC excitation voltage for the resistive sensor has been utilized. The proposed front-end has been designed, as integrated circuit, in a standard CMOS technology (AMS 0.35µm), with a dual-supply voltage (±1.65V), so to be suitable in low-cost portable applications. Post-schematic simulations, on the designed integrated solution, and experimental results, obtained from a preliminary discrete-component prototype, have both shown high linearity and reduced percentage error (in the order of few %), with respect to the calculated theoretical values.