Sensors and Microsystems

The following sections are included:

• FOREWORD

• CONTENTS

A tutorial description is made of the recently introduced computer screen photo assisted technique (CSPT). The technique is based on the use of a (computer) screen as a light source in physical experiments and for colorimetric assays. In the present contribution we concentrate on the colorimetric applications of CSPT. We describe how the so called rgb- colors produced by the screen can be used together with a web camera to obtain spectral information, both for transmitted and reflected light from a sample. Fingerprinting of colored samples is further enhanced by the use of the information in all three channels of the web camera, enabling as an example the separation of light emission (fluorescence) and absorption for a given dye. A short discussion of the physics behind CSPT is given. The evaluation of test strips used to determine a number of parameters in urine for medical diagnostic purposes is given as an example of one of the interesting application areas of CSPT. It is also pointed out that the CSPT platform is suitable for mobile applications (palmtops, mobile phones) and furthermore inherently compatible with internet based control and evaluation of diagnostic tests both for medical and environmental purposes.

The following sections are included:

• Introduction

• Materials and Methods
  • Materials and Reagents
  • DNA amplification by polymerase chain reaction (PCR)
  • Screen-printing of gold electrodes
  • Purification of thiol-derivatised oligonucleotides
  • Bio-modification of the sensor surface
  • Hybridisation with synthetic oligonucleotides and PCR-amplified samples
  • Hybrid labelling with alkaline phosphatase and electrochemical detection

• Results
  • Electrochemical characterisation of the screen-printed gold electrodes
  • Electrochemical investigation of the probe-modified surface
  • Labelling with alkaline phosphatase
  • Optimisation of hybridisation time
  • Calibration plot for synthetic oligonucleotides
  • Hybridisation with PCR amplified samples

• Discussion

• Conclusions

• References

Photosystem II providing direct electron transport with electrodeposited poly(mercapto-p-benzoquinone) was immobilised onto modified gold electrodes. The properties of the biosensor were characterized using linear sweep voltammetry, atomic force microscopy and photo-induced chronoamperometry. I₀=9nM and LOD=0.7nM for DCMU showed improved sensitivity compared to all previously studied PSII biosensors.

ITC-irst Microsystems Division is since many years active in the design and fabrication, at prototype level and small volume production, of silicon integrated microsystems. In this paper we present two examples of recently developed microsystems: a new type of RF MEMS switch and an ISFET based Bioelectronic Microsystem for monitoring cellular metabolic activity.

The RF MEMS switch, which has been named "Symmetric Toggle Switch", is a capacitive microswitch based on a push–pull mechanism and utilizes torsion springs and levers, placed symmetrically and transverse to CPW line. It presents low actuation voltage and high isolation, and has been designed for high RF power and reliability applications in telecommunication.

The Bioelectronic microsystem uses ISFET arrays for extracellular acidification monitoring with VLSI read out electronics. The system is also intended for electrophysiological measurements by monitoring, extracellularly, the electrical activity from a network of neurons coupled to the microtransducer array substrate. The proposed system should be able to measure the electrical activity, as well as the metabolic activity, of a neuronal cell population by means of ISFET devices.

The immobilization of GOD enzyme on a series of different substrates (Si wafers, nanostructured TiO₂ films and Au nanotubes) has been investigated by means of X-ray photoelectron spectroscopy and atomic force microscopy. The peak-fitting analysis of main XPS lines enabled us to identify the GOD signals and to compare the enzyme's entrapment on different substrates. The highest amount of entrapped enzyme was registered on the surface of nanostructured TiO₂ films prepared by using MOCVD technique. Preliminary electrochemical studies of glucose oxidase, immobilised on titanium oxide films, were carried out in order to investigate the direct electrochemistry and the possibility to employ GOD/TiO₂ structures in biosensing devices.

This paper describes the use of oligonucleotide-modified screen-printed gold electrodes for the enzyme-amplified sensing of DNA sequences that identify pathogenic bacteria. Particular attention was given to design of the capture probe sequence, in order to obtain the highest hybridisation yield at the sensor surface. Moreover, probe surface densities were observed to deeply determine the bio-recognition capabilities of the immobilised probes. The electrochemical genoassay allowed specific detection of the PCR-amplified targets (388 bp).

The idea at the base of this study was to test bio-mimicking receptors computationally designed for compounds of evident toxicity like pesticides. Three tetrapeptides, with different estimated binding energy versus pesticides, were used for the experimental approach. The affinity toward two different pesticides, one carbamate (CM) and one organophosphate (OP), was tested using an electrochemical bioassay for AChE inhibitors. Concentrations, incubation time, and ionic strength of the oligopeptide-pesticide solution were evaluated using the electrochemical screening method. This study showed a nicely dependence between the estimated binding energy calculated by computational modeling and the ability of the tetrapeptides to bind the pesticides in solution. Particularly one of them (the tetrapeptide His-Gly-Ser-Ala) appeared as good candidate for the development of affinity systems for OP pesticides.

The development of piezoelectric and optical DNA-based sensing for the detection of point mutations of the TP53 tumor suppressor gene is presented. The sensing is based on the hybridization reaction between the immobilized probe and the target in solution. The mutation is detected since differences in the hybridization signal can be detected when the probe hybridizes the fully complementary or the mutated sequence.

The immobilization chemistry is performed by thiol-dextran-streptavidin coupling and then the biotinylated probe is added.

On the gold surface of the quartz crystal used for piezoelectric sensing, the specific probe sequence is immobilized, while the sensor chip of the optical device BIACORE X was modified by immobilizing, on the two flow cells, two different probes, differing only in one base. One probe is the same as in the piezoelectric sensor and the second probe contains the sequence carrying the mutation of interest. The hybridization reaction with two different target sequences (fully complementary and mutated) was performed. The analytical parameters of the systems were studied.

Field effect transistors (FET) are candidates for a new generation of fully electrical DNA sensors [1,2,3]. However, experimental data and theoretical models are still missing concerning the interaction among sensor surfaces, promoting polymers, and DNA. In this work we have studied the self-assembled monolayer of polypeptide poly(L-lysine) (PLL), which is used to control the specific adsorption of DNA onto the gate surface of Ion Sensitive Field Effect Transistor (ISFET), with silicon nitride (Si₃N₄) as the gate sensitive area. We have analyzed the adsorption of PLL, which has a fixed positive charge per monomer, through electrical measurements.

Conjugated polymers (CP) are a class of organic substances of increasing interest for their electroluminescence photoluminescence and nonlinearity properties. Some other properties of these molecules can be exploited to fix enzymes for biosensors. In this work, we investigate the immobilization property of a new class of modified polyphenil-ethynilenes (pPE). In these polymers, a glycol thioester group has been added to favour both the immobilization of enzymes and their filmability by self-assembly (SA) method. As a first glance, we choose to study the immobilization of the enzyme glucose-oxidase (GOD), responsible of the catalytic reaction of glucose, that is a well-known process and successfully applied in a wide class of glucose sensors. First, the enzymatic activity and stability of SA layers on dielectric substrates was demonstrated. Then, the behaviour of immobilized enzyme was tested in a Surface Plasmon Resonance (SPR) detection scheme as a fast and highly sensitive tool to monitor the interface enzymatic reaction. To this goal, gold-pPE/GOD multilayers were made and put in contact with a solution of glucose in water. Then, they were coupled in a Kretschmann configuration to a propagating surface plasmon by using light at 850 and 633 nm wavelengths. A well resolved angle shift was detected with both wavelengths, putting in evidence the set-on of the catalytic reaction of glucose. These encouraging tests indicate that the new pPEs can be excellent and stable immobilizers of enzymes, and are able to preserve their activity. This can be combined with high resolution optical techniques as SPR to give attractive alternatives to the existing systems or for their implementation.

Molecular binding between the glutamine binding-protein (GlnBP) from Escherichia coli and L-glutamine (Gln) is detected by means of an optical biosensor based on porous silicon nano-technology. The binding event is revealed as a wavelength shift in the reflectivity spectrum of a porous silicon optical microcavity (PSMC). Exploiting the hydrophobic interaction between GlnBP and the porous silicon surface "as etched", we avoid any preliminary surface functionalization process. The unmodified porous silicon optical microcavity, infiltrated by the protein, results stable to oxidation for few cycles of wet measurements.

This work is aimed to study the feasibility of a low energy gamma-ray detector for nuclear medicine to be inserted into a body cavity, duct, or vessel. The small dimension detector concept is based on a CsI:Tl scintillation crystal coupled to a Si Avalanche Photodiode (APD) mounted in a catheter. Due to the availability of ^99mTc in nuclear medicine departments, 140 keV photons have been considered for detector design. At this energy the response concerns a more extended volume nearby the cathector than in the case of beta emitting radiotracers. Monte Carlo simulations have been performed and results have then been compared to experimental ones. The latter have been obtained using a ⁵⁷Co radioisotopic source and a laboratory setup including a detector having dimensions not optimized coupled to a low-noise conventional electronics. Count rates and sensitivities have been measured approaching a point source to the detector along some paths and considering different background irradiation levels.

Recent advances in mobile technologies have greatly extended traditional communication technologies to mobile devices. Besides, thanks to VLSI integration technologies, mobile devices with high power calculation are more and more frequent available on the consumer market. So, it is possible to fit these devices with healthcare environments, which are obviously "mobile" where doctors and nurses do not have fixed workspaces. The aim of this study is to design and implement a mobile system for patient heartbeat monitoring, and to up-to-date an electronic case sheet, consultable by every hospital PCs for remote control of patient heart frequency.

A system intended to bring about innovation in remote health monitoring in terms of simplicity, economy and effectiveness in both domestic and hospital applications has been designed and prototyped.

It allows real-time rescue in case of emergency without the necessity for data to be constantly monitored by a medical; the unit performing a real time diagnosing electronically. When an emergency sign is detected through the real-time diagnosing system, the system sends a warning message to persons able to arrange for his/her rescue. A GPS system also provides the patient's coordinates.

The system might be useful not only to GPs but also to sportsmen. Thanks to its characteristics it can help reduce hospitalization rates and length of stays thereby improving health costs and quality of life.

The main aim of this work was to conceive a more reliable dental implant system to improve the load mechanism transfer from tne implant to the surrounding bone media for better long term fixation. There are several design approaches to achieve this goal, such as coating the implant with bioactive materials, changing the implant's geometry or using different materials. In this work, optical Fibre Bragg Grating (FBG) sensors have been used to dynamically measure the bone response to mechanical impact in implants and evaluate load transfer.

The impedance spectroscopy is a very promising technique for monitoring the blood glucose, very useful when frequent measurements are required. Our approach for monitoring the glucose level changes makes use of an AC analysis of the skin impedance over a wide frequency range, which is scanned until the optimal frequency, corresponding to the best sensitivity, has been reached. Our sensor has been optimized to work in frequency range 1-200MHz, in which the best performances in terms of electrical changes in the blood can be provided.

Automatic breathing detection is an important medical issue in apnea syndrome in newborn and/or quite old people, or to detect the response of body to physical activity. We detect the breathing using a conductive rubber to sense chest displacement. At the best of our knowledge, this is the first sensor based on the conductive rubber specifically designed to measure the breathing frequency. The conductive rubbers offer quite cheap and sensitive devices for dilatation measurement.

Signal detection is easier than in piezo sensor, compared to inductive displacement it is more simple. We expect it could be more rugged than inductive sensors and then other kind of resistive sensors. We are also studying ageing of this device for electrical and mechanical stress, and we plan to test more kind of conductive rubber. The application of the belt is not so tight to be oppressive so that it could be worn for long time, allowing us to plan for continuous measurement and recording.

In this paper we present a non-contact pressure control system based on the well-known water-column principle. It is a part of a complete system for robot-assisted endoscopy of human sub-arachnoid spinal space. The sensing elements are represented by optical proximity sensors. Pressure maintaining is a fundamental task for spinal endoscopy because unacceptable pressure variations inside sub-arachnoid space may cause serious damages to the patient's vital activities. The system was tested during in-vitro experiments on an artificial mock-up of the spine and during in-vivo experiments on pigs, which proved the reliability of the system.

One of the objective of the four year European project CLINICIP - Closed Loop Insulin Infusion in Critically Ill Patients - is the study of the metabolism of the adipose tissue in intensive care patients, by means of continuous monitoring of pH, pO₂, pCO₂. Microdialysis is the approach followed for the extraction of the sample from the subcutancous adipose tissue; the drawn interstitial fluids flows through a microfluidic circuit formed by the CMA60 microdialysis catheter in series with a glass capillary on the internal wall of which the appropriate chemistry is immobilised. The modulation of the fluorescence lifetime is the optical working principle used for the detection of oxygen and carbon dioxide, whereas absorption modulation is the one utilised for the pH detection. On this basis, two different optoelectronic units were developed for the interrogation of the glass capillary, one for life-time measurements and the other for absorption measurements. Preliminary tests demonstrated a resolution of 0.03 pH units for pH; ≤ 0.55 mmHg for oxygen and ≤ 0.6 mmHg for carbon dioxide; and an accuracy of 0.07 pH units for pH; ≤ 1 mmHg for oxygen and ≤ 1.5 mmHg for carbon dioxide. In vitro tests with the catheter CMA60 were performed for the metabolities O₂ and pH and a recovery of about 100% and 70% respectively was measured.

The idea of the new electronic medical device we propose, named "Aglaia", arose in response to the growing need perceived by medicine for high-tech diagnostic aids combining such features as reliability and specifity with non-invasive techniques.

Aglaia allows the effective auscultation, the accurate processing and the detailed visualization (temporal and frequency graphs) of any lung sound. Then, it is suitable for the continuous real-time monitoring of breathing functions, resulting very useful to diagnose respiratory pathologies. It provides medical specialists with a totally non-invasive high-engineering device able to detect and analyse the widest number of data for the monitoring of the respiratory system by the simple recording and evaluation of lung sounds being a substantiated correlation between lung sounds and diseases.

We have designed a microcontroller-based medical device for long term recording electrocardiograph (Holter applications) allowing data from up to 12 channels to be stored, thus providing the diagnostic capabilities of the static electrocardiograph (ECG) together with the wearability and the long term registration of the cardiac activity. Thanks to its specific sensors, embedded in a kind elastic band, it is possible to place on the thorax many electrodes without reducing the movement potentials. Moreover, the elastic band is provided with a wireless module (Bluetooth) to send the data to the recorder unit. The storage support is a flash card. Therefore, the new system is miniaturised and results more comfortable than the commonly used taperecorder type portable electrocardiographs. The microcontroller permits to implement a diagnostics algorithm and/or to download real time the data by UDP channel.

We investigate on the light emission properties (photoluminescence) of tin oxide nanobelts systems, synthesized by thermal evaporation of oxide powders under controlled conditions. By pumping the nanobelts samples either by ultraviolet or blue light a strong light emission is obtained, whose spectrum is broad and peaked in the green region. It is observed that the photoluminescence spectrum of the samples is significantly quenched when the sample surface interacts with nitrogen dioxide, even at concentriation as low as few ppm. Therefore, we performed time-resolved photoluminescence measurements in order to determine the effect of gas interaction on the recombination time of the excited states. The results are discussed in terms of a very fast charge transfer across the nanostructure/molecule interface.

In this paper we report on WO₃ films deposited by thermal evaporation. Layers have been characterized by means of electron microscopy techniques, revealing a microstructure suitable for gas sensing applications. Functional characterization has been carried out towards NO₂, NH₃ and CO, revealing the capability of the material to detect NO₂ concentrations lower than 100 ppb, with low cross-sensitivity towards CO and NH₃.

Sensor and Semiconductor Laboratory of Department of Physics of Ferrara (SSL) has implemented a quality management system (IS0 9001:2000) about processes of planning, development and production of thick film gas sensors and photovoltaic cells. The management system, based on the scheme Plan, Do, Check-Act, allows the monitoring the laboratory activities to get "continual improvement". The eight principles of quality have been applied for the first time to the research activity in the University, and they turned out to be simple but powerful tools for the success of the system. Moreover, the above mentioned principles being directed toward the internal performance, not only will benefit the organization itself, but also customers and interested partners. The international standard applied to SSL is based on four major clause headings which are: manager responsibility, resource management, process management and measurement, analysis and improvement.

Nanostructured titanium oxide was synthesized through an innovative and low-cost process called gel combustion. The technique merges chemical gelation and combustion processes. As synthesized gel combustion TiO₂ nanopowders showed only formation of the anatase phase with a crystalline domain size of 6 nm. High temperature treatments affected largely domain size and phase composition. O₂ sensing properties at high temperature (400 – 500 °C) were evaluated on pure and Pt-doped TiO₂-based sensors.

An approach to the production of a new class of gas sensors consisting of nanostructured hybrid organic-inorganic thin films is proposed. It is based on the co-deposition from supersonic beams of π-conjugated organic materials and cluster-assembled metal oxides in a UHV apparatus including surface characterization methods. The unique control achievable by supersonic beams on the initial kinetic energy, momentum and state of aggregation enables the growth (SuMBE) of molecular materials with controlled properties at different length scales. On the other hand, by means of supersonic beams of clusters, nanocrystalline TiO₂ films can be grown without annealing, so that grain size and morphology can be better controlled. We show that by the co-deposition of organic molecules and titania clusters, gas sensors based on sensitized nanostructured titania can be prepared exhibiting improved and novel gas sensing properties.

Microstructural characterization of indium oxide and silicon nitride thin films has been performed in order to investigate their suitability for gas sensing applications in a layered structure employed as a Surface Acoustic Wave device. Thick silicon nitride (SiN_x) and thin InO_x films have been deposited on a lithium tantalate (LiTaO₃) piezoelectric substrate by using a planar RF magnetron sputtering. The deposited films were characterised by X-ray Photoelectron Spectroscopy and Atomic Force Microscopy in order to understand and to control the different parameters that affect the film gas sensing properties, such as the thickness, chemical composition and surface micromorphology.

Carbon black/polymer composite are very interesting materials already used to produce VOCs sensors. In this work we study the possibility to model the response of sensors quantitatively and to describe the difference between sensor obtained with same polymer matrix (poly(2-hydroxy-ethyl-methacrylate)) changing type of carbon black. We have used carbon blacks characterized by different superficial area, structure and chemical functionalization. In order to evaluate the influence of filler type on the sensitivity of the different devices prepared, we are setting up a quantitative model to obtain the responses of the sensing devices. The implemented model is a combination of a conductivity model based on the General Effective Media (GEM) and a swelling model giving information about how much the composite swells as function of vapor concentration and type.

Metal Reactive Insulator Silicon Carbide (MRISiC) Devices with different reactive insulator layers of Ga₂O₃, TiO₂, and WO₃ have been fabricated and their hydrogen gas sensing performance has been investigated. Responses of devices with different reactive insulator layers have been compared in terms of barrier height, operating temperature range, series resistance, time constants and turn on voltage, all of which are modified by changing the reactive insulator layer. It is shown that exposure to different gas concentrations results in changes in carrier concentration and in barrier height, which results in a change in the forward bias voltage. Voltage shifts as large as 1 V have been observed. In addition, parameters have been extracted from Current-Voltage (I-V) measurements, which have shown changes in barrier height as large as 50 meV for H₂ concentrations of 1%.

Gas-sensitive properties of γ-Fe₂O₃ thin film, deposited on Si-substrate of new design, have been studied in this work. The layers were formed by using sol-gel derived γ-Fe₂O₃xnH₂O colloidal solution. Structural features of the films and peculiarities of iron state were obtained by employing XRD, HR-TEM, IR and Mössbauer spectroscopy. High sensitivity of the mentioned sensor to CH₄ has been established.

Semiconductor sensors based on nanocrystalline SnO₂, In₂O₃ and In₂O₃-SnO₂ thin films have been investigated for detecting low concentration (2-20 ppm) of nitrogen dioxide in dry air. In this work the gas-sensitive layers were prepared by modified sol-gel methods making use of no-standard precursors and a suitable surfactant. The samples have been morphologically characterized by SEM. Good gas-sensing responses towards NO₂ have been found for all the prepared samples with improved performances for the In₂O₃-SnO₂ based sensor. The performances of the sensors have been discussed according to the surface chemical reactions between the gas phase and the semiconductor.

Optical fluorescence changes of 6FDA-DAD fluorinated polyimide thin films, pure and doped with nile-red, have been monitored in presence of water, ethanol and isopropanol. The optical response depends on the species and on the concentration of the vapour, due both to the different permeation into the polymer matrix and to the hydrogen bond strength developed between the analyte molecule and the fluorophores. A lower detection limit of 500 ppm has been reached.

In this work free (H₂TPP), cobalt (CoTPP) and iron chloride (FeTPPCl) 5,10,15,20 meso-tetraphenyl porphyrin thin films have been deposited by vacuum evaporation (VE) and by spin coating technique (SPIN). Chemical and morphological properties of the samples were investigated by means of FT-IR and AFM analysis. This work pointed out, through a comparison between the optical responses of VE and SPIN films exposed to acetone, ethyl alcohol and NO₂ atmospheres, a large response dependence on the deposition techniques.

Metal oxide gas sensors (MOXs) are widely used in olfactory electronic systems for their high sensitivity and low-cost. These sensors modify their conductivity in presence of oxidizing and reducing gases, and their performance is strictly dependent on the measurement technique adopted. In particular, it was already established by many works that a noticeable improvement in selectivity can be obtained by operating MOXs with a variable temperature. In this context, a strong interest in developing simplified models able to predict the sensor response is rising.

A new non-aqueous sol-gel process has been implemented for the preparation of SnO₂- and In₂O₃-nanostructured oxides. Thick films of these nanopowders were tested in the monitoring of trace level of both oxidizing and reducing gas. These devices have shown enhanced performances respect to conventional sensors with linearity in a wide range of concentration, lower operating temperature and fast dynamic.

Semiconductor gas sensors are widely used due to high sensitivity to many chemicals and low costs, that make them interesting for applications in many different fields. In this paper a system for a complete evaluation of gas sensor response is described. An array of mass flow controllers and a radially symmetric stainless steel measurement chamber allowed to expose the sensors to controlled gas mixtures. The measurement chamber was designed to obtain an homogeneous flow without significant recirculating zones or stagnant volumes and to guarantee all sensors to be exposed at any time in the same conditions. A dedicated sensor holder avoided the need of microbonding procedures and allowed an easy mounting and a stable electrical contact with the sensor tracks and the platinum resistor embedded into the sensor support. The temperature of each sensor was independently controlled in the range 30 - 700 °C thanks to a PID control loop. The determination of the resistance-temperature calibration curves allowed to use the platinum resistors also as temperature sensors. The experimental set-up was fully automated by a dedicated software developed in Labview 7 environment. The gas sensors performance have been evaluated by this integrated experimental set-up in a fast, easy and complete way.

The conductance in air of thick-film gas sensors operating via flow trough tecnique strongly depends on the flux. In this work we demonstrate that the major effect of the flow rate is a change in humidity, because the thermal effect on the sensor is negligible. A mathematical model based on heat exchange and direct measurements of the resistance of the heater confirms this hypothesis and humidity compensation gave very good results.

A novel co-precipitation route for preparing pure Tin-Titanium solid solutions has been developed. Special emphasis focused on Sn_1-xTi_xO₂ systems with x = 0.3, 0.5 and 0.7 for investigating the influence of composition, microstructure and morphology on gas sensitivity. Nano-grained powders have been obtained for each stoichiometry and have been characterized by DTA/TG, XRD, microanalysis and SEM techniques. We deposited the Sn_1-xTi_xO₂ powders as thick films, which were comparatively tested vs. reducing gases. Preliminary studies stated that each layer exhibits an higher response respect to SnO₂ and TiO₂ reference layers, when tested in the same working conditions (100 ppm of CO, 300-400 °C working temperature). In particular, for 7:3 Tin-Titanium ratio the magnitude of the response attained at 300 °C was S = 25.

In this work, the conductivity behaviour of a porphyrin was studied. The effect of electrode nature and film thickness was also considered together with the exposure to dry and wet air. Results shows that porphyrin is intrinsically insulator but the conductance of thin films deposited on metallic electrodes can largely increase when exposed to humid air.

The aim of this work is to carry out a performance comparison between a commercial Bosch Lambda probe and a sol-gel TiO₂ thin film deposited an alumina substrates. Actually, zirconia based lambda probes are a well-established technology in the field of combustion control in fuel injection engines. An experimental bench was realized in order to perform contemporary data acquisition of a Bosch lambda probe Mod. LSF 4.2 and a TiO₂ thin film sensors. The signals of both sensors is acquired with an electrometer with scanner card on real gasoline engine. Fast response time is observed from TiO₂ sol-gel sensor, while best results were obtained from first experimental data on Pt doped devices, that outline response time comparable with commercial probe.

By reflectance anisotropy spectroscopy we have measured significant changes in the optical spectrum of Langmuir-Blodgett (LB) and Langmuir-Schaeffer (LS) porphyrin films, induced by vapour organic compounds (ethanol and propanol). Variations of the optical signal have been mainly detected in the Soret band region of the molecule, namely at 2.84 and 2.88 eV, with an evident dependence upon the different cycles of exposure/purging.

This result has a twofold implication: on one side it helps to comprehend the origin of the thickness dependence of RAS spectra measured at LB and LS layers; on the other, it opens an intriguing possibility towards the development of a sensitive optical gas-sensor.

Carbon nanotubes are fascinating new functional nanomaterials with remarkable electrical, optical, structural and mechanical properties [1]. The sensing properties of Langmuir-Blodgett (LB) films consisting of tangled single-walled carbon nanotubes (SWCNTs) used as sensitive nanomaterials for volatile organic compounds detection have been investigated by using Quartz Crystal Microbalance (QCM) 10 MHz AT-cut quartz resonators and standard Silica Optical Fiber (SOF) based on light reflectometry at a wavelength of 1310 nm [2,3]. The proposed detection techniques are focused on two key parameters in the gas sensing applications as mass change and complex refractive index change induced by gas molecules adsorption. High sensitivity to ethanol and ethylacetate vapors with concentration in the range 10-500 ppm, very fast responses and sub-ppm limits of detection have been observed for both sensors.

In this work, a coated Long Period grating based novel fiber optic sensor able to measure the concentration of organic analytes, in aqueous environment is presented. Syndiotactic polystyrene was used as sensitive polymeric layer due to its high sorption properties towards chlorinated and aromatic compounds. In particular, a thin semi-crystalline syndiotactic polystyrene film with crystalline nanoporous δ form was deposited along the sensing element by using dip-coating technique. Chemical detection has been carried out by measuring the wavelength shift and the amplitude change in the attenuation bands of the long period grating due to analytes sorption. Experimental results demonstrate the capability of the proposed sensor to detect very low concentrations (sub ppm) of chloroform in water. Finally the reversibility of the chloroform absorption is successfully investigated.

This study identifies an n-type porous silicon material that responds in a rapid and reversible manner to sulphur dioxide at room temperature, by an high quenching of its photoluminescence (PL), even at concentrations in the range of hundreds of ppb. PL quenching behaviour of this material has been investigated in nitrogen and in air, operating mechanism discussed, at the purpose of utilizing it for the fabrication of a stable device, that could satisfy the severe environmental requirements imposed by current laws.

In this paper a study on In₂O₃-based oxygen sensors operating at low temperature is reported. The accurate control of the morphology and grain size, achieved by applying a new non aqueous sol-gel modified route, allowed us to obtain oxygen resistive sensors with enhanced sensitivity at low temperature. The effects of operating temperature and Pt doping on the sensor response and the sensing mechanism were evaluated.

RPC (Resistive Plate Chambers) are used as trigger detectors of the muon system in LHC experiments (ATLAS, CMS and ALICE). These detectors are made of phenolich melaminic laminate electrodes, coated with a polymerized linseed oil film delimiting the gaseous sensitive volume. Our purpose is to understand the relative humidity (r.h.) influence on the conduction mechanisms in these electrodes. We present here the results of amperometric measurements on sample kept at fixed temperature 22° C on r.h. ranging within 10 and 90 % in cyclic way.

Ca- and Pd-doped iron oxide thin films have been prepared by a liquid-phase deposition method (LPD) starting from aqueous solutions of the precursors. Aim of this work is to investigate the role of Ca and Pd in modifying the sensing properties of Fe₂O₃ thin films for ethanol vapor sensing. Thin films sensing properties were investigated at constant relative humidity (50%) varying the sensor working temperature in the range 200-400°C. The response to some interferent gases like NO₂, CO, NH₃ was also studied. Ca doping was found an effective way to enhance the sensor response and also to increase the selectivity to ethanol. Pd doping improves the recovery times but decreases the selectivity to ethanol enhancing the CO response.

The operation of sensors in environments characterized by high temperature, high pressure, chemical activity or nuclear radiation is increasing their relevance in several engineering applications. Thus, the development of sensors based on materials suitable for operation in harsh environment is desirable. The outstanding physical and chemical properties of Chemical Vapor Deposition diamond could then be profitably exploited in the realization of electronic devices that could work when commercial sensor fail. To this purpose, a thermochemical sensor was designed using p-type CVD-diamond films and Palladium. The sensor was tested for different temperature drops, showing values of the thermoelectric power as high as 350 µV/°C with good stability. The catalytic properties of thin palladium films allow the thermocouple to be used for gas detection. As an example the hydrogen content, within a hydrogen-nitrogen gas mixture, was measured by means of the change occurred in the Seebeck output voltage, showed by the thermocouple, at constant values of the temperature drop. The sensor response was measured for hydrogen contents varying between 0.5 % and 2 %.

The aim of this research is to study and fabricate a high sensitive [1] sensor for hydrogen detection, based on palladium. For this purpose, the thermoelectric power of some metals was used, for the fabbrication of varieties of thin film thermopiles with a number of junctions from 20 to 140. Each device was constructed by usign Pd and another suitable metal, such as Cu and Al. We have used the two most rilevant features of Palladium: its capability to adsorbe hydrogen and the consequential change of its thermoelectric power. We have caracterized the response of these devices in function of the temperature difference ΔT present between the hot and cold junction. Afterwards we have studied the translation of the response curve when the device under test was exposed to a specific hydrogen concentration.

A novel electro-acoustic chemical sensor based on thin film bulk acoustic resonators (TFBAR) is presented. The use of TFBAR resonators, in the GHz range of frequencies, can widely improve the sensitivity of the well known quartz crystal micro-balance (QCM), whose operation frequencies (a few tens of MHz), limits their use to those applications where the detection of pollutants in concentrations of a few or less ppm is not essential. The TFBAR structure is implemented on (001) silicon substrates, an anisotropic chemical etching from the back side of the Si wafer is used to obtain the Si₃N₄ or SiO₂ - AIN resonating membrane. The devices result robust in construction and miniaturized in size; the technologies involved in their fabrication are fully compatible with those of the Si integrated circuits. The performances of the sensors have been tested using thermal evaporated thin layer of Co-tetra-phenyl-porphyrin, deposited on the etched side of the membrane. Time response upon different cycles of CO and Ethanol adsorption and de-sorption are reported together with the sensors calibration curves. Time stability, repeatability and sensitivity have been tested and reported.

We have developed highly sensitive microacoustic vapor sensors based on surface acoustic waves (SAWS) ST-,X quartz 433 MHz two-port resonator oscillators. A nanocomposite film of single-walled carbon nanotubes (SWCNTs) embedded in a cadmium arachidate (CdA) amphiphilic organic matrix was prepared by Langmuir-Blodgett technique with a different SWCNTs weight filler-content onto SAW transducers as sensing interface for vapor detection, at room temperature. The structural properties and surface morphology of the nanocomposite have been examined by X-ray diffraction and scanning electron microscopy, respectively. The sensing properties of SWCNTs nanocomposite LB films have been also investigated by using Quartz Crystal Microbalance (QCM) 10 MHz AT-cut quartz resonators. The measured acoustic sensing characteristics indicate that the sensitivity to polar and non-polar tested organic molecules (ethanol, ethylacetate, toluene) of the SWCNTs/CdA nanocomposite increases with the content of SWCNTs embedded in the nanocomposite with a linearity in the frequency change response and a very low sub-ppm limit of detection. Pattern recognition based on ANNs has been successfully applied for VOCs recognition using SAW and QCM sensors coated with 27.5 and 75.0 wt.% SWCNTs nanocomposite.

Experimental results on the capability of a Metal Oxides (MOXs) based optical sensor to perform ammonia detection in water, at room temperature, are presented. Electro-spray pyrolisis technique has been used to deposit the SnO₂ films on the distal end of standard Silica Optical Fibers (SOFs). Single wavelength reflectance measurements have been carried out to test the sensing performances for ammonia detection in water. High sensitivity to the target analyte with fast time response and good desorption properties in the minutes range has been demonstrated.

A measurement system conjugating the flow-injection technique in an automatic system and a low cost spectrometer as the photo-detecting device has been set in order to evaluate the concentration of Chromium (VI) in water. Light absorption spectra of the complex Chromium (VI) – Diphenylcarbazide, carried into the measuring cell, were analysed to detect the effect of interfering quantities and substances by also operating with suitable data processing techniques, like neural network. The aim of this work is to check the feasibility of this approach, for on-line and distributed measurements. Aspects concerning instrumentation system and operating steps are analysed in order to evaluate uncertainty causes and their effects on the whole uncertainty of the methodology, taking into account requirements of method reproducibility and standardization.

Some of the vegetal matrixes that are more common and more frequently described in the literature for their high antioxidant activity, such as green tea, black tea, rosemary and coffee, were selected. Methanol, acetone and aqueous dry extracts were prepared from each of these vegetal matrixes, using for extraction solvents considered to be complementary in processes for the extraction of antioxidant substances present in the vegetal matrixes. For the three extracts obtained from each matrix the antioxidant capacity was determined using a new electrochemical method based on the measurement of the anodic area of a cyclic voltammogram.

Platinum electrodes modified with electropolymerised film were assembled for rapid amperometric detection of nitrites. Parameters such as the permeability of the fims to nitrites, interference effects and film morphology were studied. The new nitrite sensor was fully characterized by Flow injection Analysis (FIA).

Screen-printed sensors are interesting devices for disposable, cheap and reliable analysis of heavy metals in connection with stripping analysis.

In this paper, we describe a novel gold-based screen-printed sensor which avoids the toxicity and the environmental contamination associated with mercury based sensor. The sensor consist of a screen-printed three electrode cell: a gold working electrode, a silver pseudo-reference electrode and a graphite counter electrode. It is used in combination with Square Wave Anodic Stripping Voltammetry (SWASV), using a portable electrochemical instrument.

The developed sensor was applied to arsenic detection. The optimised analytical parameters allows the convenient monitoring of micromolar and sub-micromolar concentrations of As(III) following short deposition time. Preliminary results on environmental samples analysis are illustrated.

A polymeric membrane ion-selective electrode (ISE) has been constructed to be used to determine quaternary ammonium salts contained in detergents for industrial use. The sensor we developed is based on PVC, as base polymer, and dibutylphthalate as plasticizer. The polymeric membrane thus obtained also contains a dodecyltrimethylammonium reineckate (DDTMAR) as cationic exchanger, which gives the membrane its characteristics of selectivity. For the electrochemical characterization of the ISE a standard dodecyltrimethylammonium bromide (DDTMABr) solution was used.

In this work, we describe the design implementation, validated by experimental results, of an innovative gas sensor array for wine quality monitoring. The main innovation of this integrated array deals with the simultaneous outputs of 8 different signals coming from a WO₃ thin film structure heated in a linear temperature gradient mode, allowing an overall evaluation of gas sensing properties of the material in a 100°C-wide window. Preliminary tests of gas sensing showed good responses to the target analytes for the specific application (1-heptanol, 3-methyl butanol, benzaldehyde and ethyl-hexanoate).

Sensor Fusion by means of different architectural approaches has shown to be a powerful tool for the analysis of data produced by arrays of chemical sensors. In this work, we focus our attention on two sensor fusion architectures based on Multilayer perceptrons, applied to a small matrix (4–elements) of chemiresistors based on thin film polymer composites, in order to obtain significative enhancement in both gas estimation precision and sensor dynamic behavior (speed).

Fungal growth on cereal grains is one of the main concerns in the storage of raw materials for food industry: because it reduces their nutritional value and due to he risk associted with the probable production of toxic metabolites (mycotoxins). Therefore, attempts are coming out for early detection and quantification of the fungal contamination degree. The aim of this work was to study the possibility of the application of electronic nose for detecting the volatile compounds, produced by the fungi metabolism, in the samples headspace.

The LibraNose showed promising performances in the discrimination between non infected samples and samples infected with two different species of fungi (P. chrysogenum and F. verticillioides).

Odorous contaminant in wheat have been detected using a conducting metal oxide semiconductor gas sensor array. Cereal grains contaminated by toxigenic fungi and relative mycotoxins can be detected and quantified using complex extraction procedures and analytical techniques. We studied the wheat odour, the presence of non-grain volatile metabolites due to Fusarium poae contamination for the determination of wheat quality classification by SPME-GC/MS and by electronic nose in order to compare analytical tecnique and sensor array tecnique.

Novels series of nano-gravimetric sensors are obtain from the deposition of new polypyrrole-derivates compound, on the oscillating quartz surface. In fact these polymers are used to modify the surface of the transductor with some functional chemical groups with affinity for a great class of volatile organic and inorganic compounds. In this article, a test that proves the chemical affinity of polypyrrole derivates sensors to a series of essential oils is reported.

A novel artificial olfactory system has been tested in order to investigate its capability of certifying extra-virgin olive oils in terms of flavour characteristics, with the eventual goal of determining their geographic origin. The results, obtained for many tens of samples coming from Tuscany, are encouraging: the system is able to detect the main defects, and its output can be correlated satisfactorily with the assessments of a panel about the organoleptic features, with the province origin and with the majority cultivar. Such results allow establishing a road map toward a protocol for the application of the system as complementary o alternative to panel tests.

The monitoring of gases and vapors of industrial and environmental interest was addressed using guided wave technologies. Hybrid optical devices making use of fiber optics and microoptics were used as an optical platform, on which to deposit gas or vapor-sensitive innovative materials. These materials, based on metal-coordinated porphyrins, phthalocyanines and their blends, were functionalized so as to offer their dielectric constants reversibly modulated by the interaction with analytes. The optical platform fitted to an electro-optical scanner, allowed the sensitive materials to be spectrally interrogated in the whole or in selected bands of the visible spectral range, so as to achieve a gas- or vapor-modulated absorption spectroscopy signal.

The optical sensors were exposed to CO, SO₂, NO₂ and NH₃ in the 25-100 ppm range. The overall sensor response was processed by means of chemometric methodologies. The experiments aimed to emulate an artificial olfactory perception as far as these toxic gases/vapors were concerned. The sensor-array demonstrated an excellent capability of discriminating the gases/vapors types and their concentrations.

Tasting systems based on array of cross-sensitive sensors are one of the most promising ways of performing rapid and low-cost analysis for foodstuff quality control. In literature many applications of Electronic tongue devices can be found for the characterization of different kinds of red wines, while the number of similar experiments concerning white wines is smaller. In the present study the electro-chemical properties of PVC-based solid contact sensors doped with different metallo-porphyrins have been evaluated, and their application in Electronic tongue system for the classification of Italian "Verdicchio" white wines is reported.

The influence of axial stress (typically originated by temperature difference) on the resonance frequency of three different types of flexural MEMS resonators, fabricated in a thick polysilicon technology, is investigated. Both clamped-clamped and a free-free resonators are considered, with a higher quality factor expected in the latter because of reduced mechanical losses in the anchors. Nominal resonance frequencies of the devices are between 10 MHz and 50 MHz. FEM simulations are performed and discussed, and their results compared, where possible, with theoretical models.

A silicon MEMS based component is projected and fabricated, that allows for minimum heat conductivity. while providing electrical connection on many channels by adopting an array of suspended superconducting metal lines, for ultra low temperature applications in the order of hundreds of microkelvin. The device is designed with L-Edit™ software and is fabricated at ITC-IRST microelectronics facility. The process has three mask levels and is divided into two splittings: one splitting is based on SU8 as polymer underlayer, the other uses polyimide. Bulk micromachining by anisotropic wet etching is used to create a cavity underneath the metal lines, and the dielectric layers underneath the lines are then dry etched leaving them suspended. The components are fabricated and technology issues related to the processing are investigated: self aligning of the polymer to the metal layer is examined to evaluate the undercut during plasma etching, and final release of the structure by silicon oxide removal is studied.

Microcantilevers are MEMS-structures suitable for chemical sensing. Sensitivity to specific analytes can be achieved by coating the beam surface with proper chemically sensitive films. This work presents the development of a microcantilever-based sensor array for agro-food applications. Modelling, design and fabrication process are presented.

We have fabricated the first example of flexible field effect device for chemical detection based on an organic field effect transistor (OFET) made by pentacene films grown on flexible plastic structures. The ion sensitivity is achieved by employing a thin Mylar™ foil as gate dielectric. The active layer is vacuum-sublimed on one side of the foil, pre-patterned with bottom-contact Au source and drain electrodes. The opposite side of the insulating film is in contact with an electrolytic solution that together with a reference electrode forms an ionic gate. A sensitivity of the device to the pH of the electrolyte solution has been observed. Thanks to the flexibility of the substrate and the low cost of the employed technology, this device opens the way for the production of flexible chemical sensors that can be employed in a variety of innovative applications.

This paper reports the development of a new MEMS device based on an innovative principle of measurement of the alcoholic strength. The new procedure takes advantage of many properties of the hydro-alcoholic solutions. The working principle of this new Silicon micromachined alcoholometer is the measurement of the evaporation energy of a droplet of solution dispensed by a tiny capillary. A microhotplate based on dielectric thin membrane has been designed in order to heat and measure the temperature of the droplets of hydro-alcoholic solution. The major advantages expected from microalcoholometer device are: small dimensions, low cost, low power of consumption, on-line measurement, small quantities of solution needed (< 10 mg), good accuracy and resolution, and wide range of measurement. Future work will develop a dedicated read-out electronic and the design of the acquisition system set up in order to manage automatically the experimental measurements. The results of this work brought to the application for a European patent.

In this communication, the compatibility of porous silicon and anodic bonding (AB) technologies for the realization of sensing micro components in lab-on-chip applications has been demonstrated. The two techniques have been combined for the fabrication of a chemical sensor, in view of its miniaturization and integration with a smart micro-dosage system. For this application a very quick and low temperature AB process is essential in order to prevent pores filling with thermal oxides.

In order to include in a silicon Lab On Chip the functional block for sample preparation, it has been developed a device based on dielectrophoresis (DEP) able to sort, isolate and burst target cells from clinically relevant samples. Although the physics may appear complex, the technology needed to accomplish DEP is straightforward and relatively inexpensive.

Because the DEP force is proportional to two independent terms, it is possible to exploit this versatility applying appropriate electrical signals to the electrodes and so optimize each application in accordance to the dielectric characteristic of the particles. The developed device has been designed for the separation of white blood cells in a diluted row blood sample and then lead these cells in an electroporation section to perfom lysis for the genetic information extraction.

A two-mask low cost technology for the fabrication of arrays of hollow, high aspect ratio silicon dioxide microneedles is presented. The process is based on the following technological steps: photo-electrochemical etching of silicon to etch a deep regular macropore array; wet thermal oxidation of macropores to produce silicon dioxide microchannels; silicon wet etching to release the microchannels and obtain the microneedles. Advantages and drawbacks of this approach are discussed on the basis of obtained experimental results.

In this work we present the microfabrication process for micro-electrode arrays (MEAs) designed for monitoring the electrophysiological behavior of neuron networks.

The developed devices mainly consist of planar multi-electrodes and three-dimensional structures for cell guided growth and networking.

Starting from a quartz wafer (double polished optical prime grade material, flame fused quartz, thickness 0.5 mm) the proposed fabrication process implements a Ti/TiN/Al/TiN low resistance multilayer for all the wires and electrical connections. All the exposed surfaces of the microelectrodes are realized in an Au/Cr (150nm/5nm) double layer: the thin Chromium layer is used in order to promote gold adhesion. The three-dimensional structures have been realized by means of a SU-8 negative resist. From a technological point of view, this research focused on obtaining i.) metal wires and electrodes with low resistivity and ii.) very thick SU-8 structures with improved performance in terms of adhesion. In order to implement well defined areas, connected by means of micro-channels, the development of reproducible procedure for SU-8 thick films deposition has been considered a central issue of this fabrication process.

In this paper the transient behaviour of ohmic RF-MEMS switches will be investigated by both experimental and simulation means. The devices are based on a suspended gold membrane and vertical electrostatic transduction, with gold ohmic contacts along the RF signal path. Dynamic RF measurements are performed by using a power detector to monitor opening and closing transitions of both series and shunt switches. Compact models of the fabricated devices are also implemented in Cadence^® through a developed MEMS model library based on modified nodal analysis. Pull-in voltage, actuation and release transition time have been observed and compared, achieving a better understanding of squeeze-film damping effect.

The design and fabrication process of a micromachined piezoresistive accelerometer based on an inertial proofmass is proposed. The sensor is addressed to aeronautical applications, that require a resonant frequency higher than 100 Hz and high damping. FEM simulations are carried out to verify the compliance of this structure with the given specifications, and an analysis of the fabrication process is presented. The readout circuit is based on Wheatstone bridge, and is designed to minimize the off axis acceleration signal [1,2]. The structure consists of a silicon made rectangular proof mass that is supported by four arms at the four edges, with piezoresistors located at both ends of each support. The fabrication of the structure is based on bulk micromechanics, by wet anisotropic etching of both sides of the silicon wafer in TMAH solution. The proof mass has convex corners that require corner compensation structures. Gold electroplating is used to deposit an additional thick layer on top of the mass.

In this paper a double axis micro-integrated Fluxgate magnetic sensor is presented. The device was designed using a PCB dual axis sensor previously realized as a starting point. In the PCB version the experimental results exhibit excellent agreement with the simulations performed using a tool based on the finite element method. Using the same design approach a version of the double axis Fluxgate structure to be realized in IC technology is here proposed. The accurate study of the magnetic field distribution allows a 75% area saving for the IC version with respect to a direct scaling of the PCB version. Imposing an external magnetic field of about 60 μT, the simulated differential output voltage of the micro-integrated Fluxgate sensor achieves a peak value of 1 mV with 5 mA sinusoidal excitation current peak at 100 kHz.

In this work a Si-based liquid separation microsystem for phenolic compounds detection in wine is presented. The main modules of the chip are i.) a Si-micromachined separation column with inlet and outlet for fluidic connections, ii.) a three-electrode amperometric sensor and iii.) a Pt microheater. Analytical calculations and finite element analysis have been performed to optimize microcolumn design. Preliminary test structures have been developed by implementing a microfabrication technological process. A system approach has been followed in the chip design in order to optimize the final packaging.

This paper describes an electro-optical sensor system used for the detection of methane with a low limit resolution of about 500 ppm. An integrated micro-heater has been used as infrared source, a commercial thermopile as infrared sensor and a 12 bit acquisition board to process data.

Optimization of planar waveguides for fluorescence biosensing is presented in this work. In particular, we show that optical (refractive index) and geometrical parameters have a strong influence on the efficiency of excitation and collection of fluorescent signals. Numerical analyses showed that a single-mode slab waveguide, operating at its fundamental TM mode and near its cut-off point, results in an efficient fluorescence excitation when employed as evanescent wave biosensor. A high refractive index contrast is demonstrated to be the key parameter for an efficient fluorescence collection. Other geometries, alternative to the classical slab waveguide, may result in an improvement of the fluorescence excitation and collection efficiencies.

Silicon optical receivers, operating at the optical communication wavelengths in the 1.3-1.55 μm range, have attracted much research effort. Unfortunately, the performance of the devices proposed in literature are poor because this wavelength range is beyond the absorption edge of silicon. In order to extend the maximum detectable wavelength, the most common approach, in the realization of Si-based detectors, is the use of silicon-germanium layers on silicon, anyway, requiring processes non compatible with standard CMOS technology. In this paper, with the aim to extend the operation of silicon-based photo-detectors up to the 1.3-1.55 μm range, an alternative approach is investigated: we propose the design of a resonant cavity enhanced Schottky photodetector based on the internal photoemission effect. The device fabrication is completely compatible with standard silicon technology.

In this paper, we present experimental results concerning sensing of vapours and liquids in porous silicon by spontaneous Raman scattering. Raman spectra are measured in backscattering configuration using a diode laser at 404 nm. The adsorption of chemical species induces a compressive strain in the porous silicon due to the action of the molecular forces, as a consequences a reversible blue-shift of the Raman spectra of the cavity has been observed.

A novel method based on micro-structured fiber Bragg gratings, for high-resolution refractive index measurement, is presented. The in-fiber structure relies on a partial and localized etching of the cladding layer along a standard grating. The main spectral changes of the structured grating are the increasing of the stop-band and the formation of a defect state inside the stop-band. The etching induces strong sensitivity of the reflected spectrum to the surrounding refractive index. Experimental results reveal the possibility to carry out low cost refractive index measurements by monitoring the reflected power using a narrow bandwidth interrogation. Resolution of 4.10^-5 for refractive index around 1.41 is obtained.

We report on a novel CMOS photon mixing sensor aimed at distance measurements, which can be fabricated in a standard CMOS technology. This device can be organized in array structures to realize range-finding integrated imagers. The measurement exploits the time of flight technique: the modulated light travels to a target and is back-scattered onto the detector. The distance is proportional to the phase shift between incident and reflected light. The photon mixing sensor, based on two interdigitated n-well diffusions on a p substrate, has been integrated together with dedicated read-out electronics, in a 500 μm × 25 μm pixel. The operation principle is based on the modulation of the space-charge region width by the applied voltage. A 128-pixel linear array has been designed in 0.35-μm 3.3-V CMOS technology (4 metal, 2 poly). An electro-optical characterization of dedicated test structures has been carried out.

A reconstruction algorithm employing an accurate modelling of the stimulated Brillouin scattering (SBS) interaction in a single-mode optical fibre is experimentally demonstrated. Distributed strain/temperature measurements are performed by using a Brillouin optical frequency-domain analysis configuration. Reconstructions are carried out by fully taking into account the influence of the modulation of the acoustic wave involved in the SBS interaction.

An aluminum prototype of the AMICA (Astro Mapper for Instrument Check of Attitude) Star Tracker Support (ASTS) of the AMS_02 (Alpha Magnetic Spectrometer) space experiment has been instrumented with Fiber Bragg Gratings (FBGs). In this work the use of FBGs in the acquisition of strains during a dynamic test on the ASTS prototype is reported. The excitation has been provided by an instrumented impact hammer, the response has been given by bonded FBGs and accelerometers nominally in the same location. All time histories have been recorded, transformed in the frequency domain to determine resonant frequencies and displacements (strain) shapes of the ASTS. Numerical simulations of this structure have been performed to predict the aforementioned dynamic features.

We propose an innovative PSP formulation in which pressure sensitive element is nanostructured silicon obtained in two different approaches and the binder is a polysilsesquioxane. The first approach is named top-down and consists in the dimension reduction of porous silicon powders assisted by a stain etching step. The other is a bottom-up one and consists in synthesizing nanometric silicon by metatheses reaction between silicon dioxide and carbon black, conducted in a ball milling reactor. We describe powders fabrication methods, formulation of our PSP and characterize paints performance.

In this work, a new device based on non-uniform thinned Fiber Bragg Gratings (ThFBGs) for the simultaneous measurements of temperature and refractive index is presented. The proposed structure relies on the use of a single and partially thinned FBG. The perturbation leads to a wavelength-splitting of the unperturbed grating spectral response in two separate peaks dependent on the surrounding refractive index and the local temperature. The simultaneous measurements of the Bragg wavelengths of the two peaks allow the accurate measurements of the refractive index and the temperature by using a single sensing element, simultaneously. Here, wet chemical etching in a buffered hydrofluoric acid (HF) solution was used for sensor fabrication. Experimental characterization for a 7.6μm etched cladding sensor is presented.

An organic, completely flexible strain gauge sensor based on a field effect devise has been fabricated. The proposed device consists in a "bottom contact" structure assembled on a flexible free standing insulating layer, without any substrate, with source, drain contacts and the active semiconductor layer on one side and the gate on the opposite side. The main advantage consists in avoiding the presence of a substrate thus allowing to apply a mechanical stimulus directly on the channel area. Thanks to the flexibility of the substrate and the low cost of the employed technology, this device opens up a new perspective for producing strain gauge devices from organic field effect transistors.

The feasibility of radioisotopic planar sources made by absorption of an active solution in Porous Silicon (PS) matrices has been studied. To this aim two PS samples, characterized by different pore dimension and shape, have been made and tested. The ^99mTc radiotracer, commonly used in nuclear medicine departments, has been loaded into the pores by immersion, and the radioactivity distribution over the porous areas has been measured by an Imaging Probe (IP). Using a solution with the low specific activity of 5.8 MBq/cc, counting rates of 96 ± 3 and 36 ± 2 counts/s per pixel (area 3.5 × 3.5 mm²) have been measured, showing good emission homogeneity for both PS samples. A mean activity ratio of 2.6 ± 0.4 has been found between the two samples. Further studies are in progress to optimize matrices treatment and loading techniques and to design porous phantoms having appropriate surface areas, shapes and absorbance.

Tabletop pulsed laser systems have been demonstrated to be of great relevance in many applications and studies. They have been widely used in several fields. Among them one can mention: generation of plasma on solid, liquid or gaseous targets; spectroscopic X rays analyses; imaging; microlithography; microscopy; radiographies (in particular of biological samples); conversion efficiency studies (laser to X or UV radiation); radiation matter interaction studies; plasma parameter determination; astrophysical studies, and so on. In this article it is reported a description, characterization and performance study of our Nd:YAG/Glass ultraintense tabletop pulsed laser system. It is located at University of Rome "Tor Vergata" and it used to produce X and UV rays by means of laser induced plasma.

In this work a temperature-compensated configuration for extending the working range of fiber Bragg grating (FBG) strain sensors has been proposed. This technique consists of the application of two FBGs to the opposite surfaces of a straight elastic beam which was bent in a horizontal direction. Pushing nearer of beam ends produced the beam curvature variation measured by means of the two FBG wavelength difference The difference of the two FBG wavelengths depends on the beam curvature, while the mean value is taken in order to compensate for the temperature effects.

The sensitivity of the system was obtained for different beam lengths. Decreasing the beam length increases the sensitivity, but decreases the working range.

The sensor proposed is less fragile than the bare fiber and constitutes a displacement sensor particularly suited for applications to breaks or separate elements of structures where it is impossible to affix the bare fiber.

Thermoelectric transducers fabricated with both p and n-type heavily doped polysilicon thermoelements are presented. The devices are realized on front-side micromachined membranes obtained with typical CMOS passivation and intermetal dielectric layers, namely thermal silicon oxide, LPCVD silicon nitride and oxide. The polysilicon layers constituting the thermocouples are deposited on different interconnection levels and connected with Al/Si paths.

The possibility to perform wafer level probing measurement of thin films thermoelectric power is demonstrated by using test structures realized with dielectric cantilevers suspended over a silicon substrate and equipped with heavily n-doped polysilicon heaters and thermistors. The measurements presented are performed on p and n-doped polysilicon thin films without the need of any atmosphere conditioning, and, consequently, in a fully automatic fashion. An ad hoc extraction procedure is proposed in order to compensate for instrumental offsets and sensitivity limits typically existing in a standard wafer-level test instrumentation.

This article presents a deformable poroelastic bidimensional elastomeric architecture that responds to deformations along various directions thanks to an integrated sensorized fabric. The sensors exploit the piezoresistivity of the loaded rubbers as a principle of strain transduction. Using this architecture, sensors have been characterized in terms of their quasistatic and dynamic electromechanical transduction properties.

In this work, the analysis of the phase response of fiber Bragg gratings (FBGs) subjected to longitudinal ultrasonic (US) field has been carried out. Numerical results reveal high sensitivity of the FBG phase response to US waves. The potentialities of the proposed approach to extend the sensing capability of fiber Bragg grating sensors as high frequency ultrasonic detectors are discussed with regard to new interrogation strategies based on time delay measurements.

The calibration of contact surface temperature probes greatly depends on the interaction between the sensor and the reference measurement surface. A dedicated calibration system for such probes has been developed at IMGC. It enables the calibration on a temperature-controlled reference surface in the temperature range from ambient to 350°C. The paper describes the prototype, its main metrological features as well as the thermal-fluid-dynamic model of the system for simulating the impact of the various influence parameters on the measurement. The preliminary results of the comparison between the numerical predictions and the experimental values, as obtained from the metrological characterisation of the system, are also reported.

This paper presents the design and performance evaluation of a new sensor system for detecting the presence of water or ice films on its surface. The system is based on a multi-frequency capacitive measurement and the effect that water and ice have different dielectric constants. Accumulation of ice or water on the electrodes of the sensor leads to a change of the effective capacitance value of the sensor. This change is measured using a sophisticated, high-sensitive, differential capacitance measurement circuit.

This paper concerns the application of electric transducers for studying the instability of peri-urban slopes in Caramanico Terme, a hilltop town located in the Apennine Mountains of the Abruzzi region (Central Italy). We describe the functioning of three types of piezometers located within different geologic materials and their response to the variations of the slope boundary conditions in terms of time lag and data reliability. The Caramanico area is characterised by a long record of historical landsliding activity typical of a high mountainous setting subjected to a relatively high average rainfall and seismic activity. Following previous landslide surveys and a careful evaluation of slope movements case records, we argue that a systematic and periodic monitoring of both ground deformation and causal factors of instability using integrated ground-based techniques, including subsurface monitoring, is necessary to advance the understanding of recurrent landslide hazards. In particular, electric transducers installed within both an oper-pipe piezometer and a Casagrande cell, together with electric piezometers, have been recognised as useful to gain a deeper insight on local groundwater variations. A very small acquisition timestep (6 hours) of the data-logging is aimed at obtaining nearly continuos pore water pressure measurements during intense rainfall and future earthquake events.

In this paper a comparison between performances of optic sensors based on fiber Bragg gratings and electric strain-gauges has been carried out. Both sensing systems are used to measure strains on strengthening reinforced concrete beams with fiber reinforced plastic laminates, an innovative and effective technique to increase loading capacity of already existing structural elements. Fiber Bragg gratings represent an alternative solution for strain measurements in the field of civil engineering to strain gauges, widely exploited and well assessed for these applications. Advantages of optic sensors in multi-point sensing systems for great numbers of sensors will be evidenced in terms of costs and performances.

The paper reviews the techniques employed for non destructive testing (NDT) on Carbon Fiber Reinforced Plastic (CFRP) materials from the perspective of the sensors characteristics and compares the different methods, even the most recently developed by the authors, based on guided acoustic waves generated/detected with piezopolymer intergitated transducers (piezo-IDT). These devices transmit and receive ultrasonic guided waves traveling inside the material and are able to detect any accidental defect or damage occurred to the material itself. New application of piezopolymer IDT for NDT on different types of composites will be presented and the very good defect detection capability will be demonstrated by exciting a symmetric mode S₀ at 350 kHz.

The PAIS system, based on IR technology, was developed by SMA (Sistemi per la Meteorologia el' Ambiente) for forest fire detection.

The application of a new adaptive filter is here presented, in order to allow an optimal recognition of emergency situations, avoiding not really dangerous alarms due to sudden disturbances of the environment.

A variable threshold is computed, based on the Hyperbolic filter algorithm, which is inversely proportional to the mean value obtained by moving a selected window through the matrix derived as two contiguous acquisitions difference.

The main advantages of this filter are a reduction of the response time and the threshold independence on the variability of meteorological conditions.

The results show that this filter is able to significantly reduce the number of false fire alarms inside the investigated area.

The PAIS system, developed by SMA (Sistemi per la Meteorologia e l'Ambiente) for forest fire detection, mainly uses Digital Terrain Model in trying to determine the exact position of the fire site. A theoretic study is here proposed, based on a new technique for determining the distance between the IR sensor and the target. The distance is computed by using both the hypothesis of black body with spherical emissivity in free space and the Bourget-Lambert-Beer law which takes the attenuation related to the atmospheric variability into consideration.

The computed distance is then used to determine UTM coordinates of the target. The real advantages of this technique are a reduction of the main memory and a more precise fire target localization.

In this paper we present an integrated wide-range resistance-to-time converter. The circuit in transistor level simulations achieves a precision of about 0.5% over a range of 5 decades (1kΩ-100MΩ) without requiring any calibration or autoranging. The presented technique exploits an integrator-based controlled oscillator, whose main time constant is function of the applied resistance value, named R_sens. The state of the art [1] of this measurement method has been improved by separating the oscillator circuit from the sensing device, leading to higher linearity performance. Indeed, the sensor response takes advantage of the fact that the device is biased between a fixed buffered reference voltage V_REF=1V and ground. A couple of high-linearity current mirrors replicate the current V_REF/R_sens and alternately push it into or pull it from the virtual ground of a resettable Miller integrator. The output of this block is connected to a couple of comparators which compare V_OUT with two fixed boundary voltages V_H and V_L(V_H-V_L=1V), producing the control signals for the switches that shunt the mirrored current. A small logic grants that the comparators switch alternately; furthermore it feeds an internal counter whose transition period is proportional to the value of R_sens. In the resistance range of interest the internal oscillator frequency will vary between f_min=50Hz and f_max=5MHz if the integrator feedback capacitance is set to 10pF and the mirrored current is scaled by a factor of 1:10 in order to reduce the operational amplifier output current, leading also to a lower total power consumption. The ratio between a reference counter, whose clock frequency is fixed at the midrange value f_mid=(f_min·f_max)^½=16kHz and the resistance dependent one represents the digitized value of R_sens. The measurement ends when the slower of the two counters reaches a fixed value N* which is enough to achieve the desired accuracy, i.e. 8 equivalent bits (N*=256). The maximum conversion time is 5 seconds, when sensing the highest resistance values, i.e. R_sens=100MΩ, while for the lower half-range values conversion (R_sens<320kΩ) requires only 16ms.

Quartz crystals are used for a variety of applications; in particular, if the quartz is coated by a chemically interactive material, it behaves as a microbalance and may be used as a chemical sensor. Since the properties of quartz crystals and of chemically interactive materials strongly depend on temperature, it is often necessary to control the temperature of quartz microbalances. Furthermore, during the measurement, it may be important to measure the speed of the flow to which the microbalance is exposed. Here we present a new ∑Δ interface for controlling the temperature of the microbalance and measuring the flow speed when an auxiliary terminal is properly added to one electrode of the quartz.

In this paper we present a CMOS integrated system for the temperature control of resistive gas sensor array. The circuit has been designed in AMS 0.35μm CMOS integrated technology. The general solution proposed performs the heating control exploiting a signal provided from a resistance-to-frequency converter. The sensor interface signal, by a digital conditioning sub-system, manages the heater circuit. The structure allows high sensibility and precision and performs good stability in temperature, power supply drift and low power characteristics so it can be used also in portable applications.

Resonators are proven to be interesting transducers for sensing applications especially in the chemical sensor domain. The sensors have been represented by capacitors/inductors in a ladder network formed from a cascade of n identical elementary cells in a mono dimensional arrangement or in a N × N array, once the type of cell impedances and the number of cells are known. This work considers these two kinds of networks and for each of them calculates the resonant frequencies generated in each node. This study demonstrates the existence of interesting frequency distributions which have remarkable characteristics.

In physical activity monitoring often only one parameter at a time is detected, since otherwise patient movement capabilities would be compromised. This is unsatisfactory since correlation among parameters is necessary to reject parameters alteration due to everyday life, but also it is necessary to detect correlated parameter alteration due to medical causes. Let's think about how everyday activities could modify heart rhythm and body temperature. We stress the importance of multi-sensor continuous data acquisition in biomedical studies also for the importance of correlated parameter changes coming from medical causes.

Our group has developed a new system for acquiring simultaneously a group of parameters which are strongly correlated: breathing rate, heart electrical activity, kinetic activity. Preliminary results on the prototypes are encouraging.

We should avoid to transform this measurement in a torture for the patient, so we need to pay attention to the non-invasivity and comfortable wearability of the sensors. To reduce device's weight we are developing a remote logger that gets signal from smaller on-body board.

In this paper we describe the structure of a multiprocessor control system for a gas sensing array. After a brief illustration of the sensor structure, a system overview will be given. Then, preliminary experimental results will be described.