Sensors and Microsystems

The olfactory system excels in both discrimination and detection of odorants. In mammals, it reliably discriminates more than 3000 structurally diverse odorant molecules and has an amazingly high sensitivity that allows the detection of very low amounts of specific odorant molecules. In addition, the olfactory system has the capability to adapt to ambient odorants, allowing the recognition of a broad range of stimuli. The discrimination among different odorants is achieved by using hundreds of receptors, activated with a combinatorial code. Olfactory transduction uses a canonical second messenger system providing two critical attributes: amplification and high signal-to-noise characteristics, giving the system its remarkable detector capabilities. In this review, we present an introduction to the basic molecular mechanisms of olfactory transduction in olfactory sensory neurons.

Chemistry play a key role in the design of active materials for sensing applications. Inorganic and polymer chemistry contributed in the past very well to the enhancements in the area of solid state gas sensors. Nowadays, chemistry has also opened a land of opportunities for the development of new sensing materials coming from the field of organic compounds, coordination complexes, hybrid composites, etc., and their synthesis on the nanoscale. In this regard, several examples from our laboratory illustrate how chemical process innovations can result in new materials developments, improving sensor performance. Advances in recent activities concerning novel sensing materials are here reported.

In this work, experimental results on the optical characterization of alcohol-infiltrated silicon/air one-dimensional photonic crystals (1D-PhCs), fabricated by electrochemical micromachining of silicon, are presented and compared with theoretical predictions. Infiltration of alcohols into 1D-PhCs produces reliable changes (redshift and increase of the bandgap order in the near-infrared region) in the reflectivity spectrum, with respect to air. Such changes, which can be attributed to an increase in the average refractive index of the structure, allow one to discriminate between different alcohols. Experimental data are in good agreement with numerical results calculated by using the characteristic matrix method, modified to take into account surface roughness of silicon walls.

We operated WO

3

gas sensor at room temperature under UV illumination. The observed increase in conductance is expected to depend on interband electronic transition, being the bandgap of the material smaller than the incident light. Strong evidence that the main phenomenon is instead surface barrier modulation is given in the present work.

Polythiophenes and, in particular, poly(3-alkylthiophenes) have attracted much interest as VOCs sensing materials due to their good environmental stability, easy processability and their particular sensing ability. In this work, the potentiality of a particular class of polythiophenes, the highly regioregular poly[3-(4-alkoxyphenyl)thiophenes], has been investigated as VOCs sensor. This class of polymers showed long term stability under room temperature operation, very high sensitivity towards hydrocarbons and low response time.

We report on electrical transport and noise processes of Epoxy/multi-wall carbon nanotube composites. The dc measurements suggest that the investigated system can be regarded as a random resistor network in which the resistors are located at the junctions between carbon nanotubes and the nodes are the conducting pathways connecting different junctions, namely the nanotubes themselves. The noise-spectral density measurements reveal the existence of a threshold voltage, above which a markedly nonlinear behavior is found and is tentatively related to the specific properties of the Epoxy-mediated contact barrier among the carbon nanotubes.

In this work, microwave-assisted technique was applied in the synthesis of different metal oxide nanostructures for gas sensing applications. Chemoresistive devices consisting of a thick layer of SnO

2

, ZnO, Cd(OH)

2

and CdO nanostructures on interdigitate alumina substrates were fabricated and their sensing characteristics investigated. Sensor devices based on these metal oxide nanostructures exhibited good performance in the monitoring of low concentrations of toxic gases.

The synthesis, electrical and sensing properties of 7,8-diazabenzo[

ghi

]perylene (DABP) mixed with multi-walled carbon nanotubes (MWCNTs) have been reported. DABP was synthesized through a photochemical reaction approach and resulted suitable for solution processing, allowing the easy deposition of films on the sensor substrate. Thin films of DABP/MWCNTs composites have shown an electrical behavior depending on the carbon nanotubes loading. Sensing properties of resistive devices fabricated using DABP/MWCNTs semiconducting composites have revealed a high and fast response to relative humidity and vapor of protonated organic solvents.

The synthesis, characterization and electrical properties of zeolite P-based material have been reported. It was verified that thick films can be deposited on ceramic substrates forming a homogeneous and porous structure, making easy the fabrication of thick film-based sensors. The structural properties of these materials revealed moreover an ideal environment for gas or vapor adsorption. Sensing properties of resistive devices fabricated using zeolite-P/MWCNTs composites have shown a rapid response and high sensitivity to relative humidity.

Thermoelectric power (TEP) of the carbon nanotubes (CNTs) films, grown by radiofrequency plasma-enhanced chemical vapor technology onto silicon substrates, has been measured. Two different metal contacts of Cr–Al and Cr–Au have been fabricated for the CNTs-based thermocouples and preliminarily investigated. The CNTs-based thermocouples exhibit large values of TEP due to the Schottky barriers at semiconducting CNTs-metal junctions. The highest TEP of 40.7 ?V/K has been achieved for the thermocouple CNTs/Cr–Al. This value is enhanced of about 2 times compared to single-walled CNTs bundles reported in literature (Collins et al. Science 287:1801–1804, 2000), and comparable to isolated suspended single-walled carbon nanotubes with Pt-electrodes reported in literature (Yu et al. Nano Lett 5(9):1842–1846, 2005) as well. The CNTs-thermocouples exhibit linear relationship for the output voltage versus temperature in the range from 20 to 70°C by providing an interesting nanomaterial for energy applications and temperature and/or radiation microsensors.

We propose a novel optical gas recognition thin film layer of 4-[

bis

[(3,5-dimethyl-1H-pyrazol-1-yl)methyl]-amino]phenol on quartz substrates. The gas optical response to the following analytes have been investigated as air pollutants (SO

2

, NO

2

, CO, CH

4

and NH

3

). The spin-coated pyrazole layer appears to have reversible sensitivity towards SO

2

and very low and irreversible sensitivity for NO

2

.

Pt-doped TiO

2

/MWCNT composites have been prepared by the sol–gel route and tested in resistive devices for the low temperature monitoring of hydrogen. A morphological and microstructural investigation by SEM, TEM, XRD and micro-Raman spectroscopy of the composites was carried out. Results indicated that, regardless the nominal C/Ti molar ratio, only the anatase phase of titania is formed. Thin films of the Pt-doped composites, deposited on interdigitated ceramic substrates, showed promising hydrogen sensing at low temperatures. On the basis of the results obtained, some hypotheses on the sensing mechanisms operating on these nanostructured hybrid materials have been formulated.

Quasi-1D nanostructures of metal-oxide semiconductors, in particular ZnO and SnO

2

nanowires, have been extensively investigated for their novel physical properties and are used in many applications such as gas sensors, transparent conducting electrodes, catalysts, solar cells and many other optoelectronic devices. They are

n

-type semiconductor with a wide band gap, showing a broad visible photoluminescence (PL) emission at room-temperature, depending on gas atmosphere. Moreover, when irradiated with UV-visible radiation (at energy higher than or equal to their band gap), metal oxide nanowires show a great increase of conductance and photocurrent (PC) is generated, if a constant potential is applied. PL emission and PC generation are strongly dependent on surface states and can thus be tuned depending on the surrounding atmosphere. In this work, we studied PC generation in SnO

2

nanowires synthesized via evaporation-condensation (EC) process and its dependence on surrounding gas atmosphere, targeting NO

2

sensing application.

In the present paper we describe the development of a surface acoustic wave (SAW) ammonia sensor which utilizes the Rh

2

(form)

4

complex as responding material. It has observed that the SAW resonance frequency shifted reversibly upwards upon NH

3

exposures at room temperature. Moreover, the greater affinity of the Rh

2

(form)

4

film coating for the N-Lewis bases guaranteed a selective binding capability towards NH

3

in the presence of water vapour, allowing to monitor the concentration of ammonia gas in the head-space of aqueous solutions.

Networked carbon nanotubes (CNTs) films have been grown by chemical vapor deposition (CVD) technology onto miniaturized Co-coated alumina substrates for NO

2

and NH

3

gas sensing applications, at a sensor temperature of 150°C. The sidewalls of the CNTs films have been modified by spray-coating with two different metalloporphyrins (MPPs) consisting of a TetraPhenylPorphyrin coordinated by a central metal of zinc (Zn-TPP) and manganese (Mn-TPP) for enhanced sensitivity and tailored specificity. It was demonstrated that the gas sensitivity of the MPPs-modified CNTs-sensors significantly improved by a factor up to four-times through a catalytic effect of the MPPs. The gas sensing properties of CNTs-sensors, including MPPs-modified CNTs, are characterized by a change of the electrical conductivity in a model of charge transfer with a semiconducting

p

-

type

character. A response of the CNTs-sensor functionalized with 2 spray-layers of Mn-TPP has been measured as 0.43% to 0.5 ppm NO

2

, and as 0.09% to 10 ppm NH

3

, at 150°C. The MPPs-functionalized CNTs-sensors exhibit high sensitivity, fast response, reversibility, good repeatability, sub-ppm range detection limit.

Water colloids of indium oxide were synthesized by laser ablation in liquids (LAL). TEM measurements have shown the formation of indium oxide nanoparticles with a bimodal distribution, consisting mainly of particles of small diameters (2–5 nm) accompanied by larger nanoparticles (about 10–20 nm in diameter).These colloidal solutions have been used to deposit films on interdigitated substrates in order to fabricate carbon monoxide resistive sensors. In

2

O

3

(LAL) films-based sensors have shown good performances, indicating that LAL is a very promising technique for the synthesis of metal oxide nanoparticles for gas sensing.

For an accurate indoor air composition analysis the most useful tool is represented by the combination of a manual SPME collection of samples and the subsequent gas chromatography/mass spectrometry characterization. This method is lengthy, expensive and moreover it cannot allow a prompt danger signal. In this paper, different classes of indoor air pollutants have been evaluated, focusing the attention on acid and basic compounds and comparing the efficiency of a commercial pH indicator to corrole response. The reactions induced by acids or bases onto the dye embedded membranes led to absorption spectra considerable changes. The computer screen photoassisted technique has been able to discriminate among the tested analytes, showing also low detection limits in the case of trimethylamine.

Gold nano-electrode ensembles were synthesized within nanoporous polycarbonate membranes and coupled with screen printed substrates. A disposable and versatile electrochemical system for biosensing and bio analytical applications has been obtained. Scanning Electron Microscopy and Scanning Probe Microscopy techniques were used to characterize the membrane surface, the nanostructured surfaces and the resulting biosensing devices. Efficiency and response of nano-probes were tested with several enzymatic immobilizations on the sensitive surface. Herein, the model case of a glucose oxidase biosensor based on nanoelectrodes is taken into account, for further evaluations on the accuracy of the biosensor system.

The optical and electrical properties of vanadium pentoxide films simply prepared by direct deposition from stable ethanol suspensions of V

2

O

5

nanoparticles, are found to change after exposure to ammonia. Aimed at developing solid state ammonia sensors able to work at room temperature, spectrophotometric investigations and electrical measurements are performed on vanadium pentoxide films deposited on glass, on V

2

O

5

films deposited on flexible substrates, having nanosilver electrodes applied on the top, and on

n

-Si/V

2

O

5

heterojunctions.

Recently, noble-metal nanoparticles (NMNPs) were introduced in the sensing discipline, and become one of the most efficient ways to enhance sensors sensitivity. It is known, in fact, that NMNPs possess peculiar optical properties. When NMNPs are illuminated by a laser beam with proper wavelength, the so-called localized surface plasmons, a collective oscillation of conduction electrons on NMNP surface, are excited. The effect is relevant, for example, in Surface Enhanced Raman Spectroscopy, where a significant enhancement of a localized electromagnetic field near NMNPs surface allows to detect species usually undetectable with normal Raman spectroscopy. Here we present a method for the growth of silver NP arrays with controlled morphology by means of the pulsed laser ablation technique performed in presence of a Ar atmosphere. The nanoparticles size and morphology can be tuned, respectively, by the Ar pressure and the laser pulse number. The SERS activity of nanoparticle arrays is investigated by Raman scattering of adsorbed rhodamine 6G (R6G) at different concentrations.

Polymer nanocomposites (PNCs) represent a new class of sensing materials for volatile organic compounds (VOCs) detection. These materials can be simply processed by inkjet printing (IJP) technique, an emerging technology that has assumed a key role in the field of electronics wherever replacing conventional rigid substrates with flexible ones is required. In the present work, we fabricated PNCs chemical sensors inkjet printing a polystyrene (PS)/carbon black (CB) composite based ink on different substrates, flexible and not, such as polyethylene terephthalate (PET), glass and alumina. The sensors responses have been analyzed upon exposure to acetone organic vapors and compared in terms of sensitivity, response time and limit of detection.

TiO

2

-based nanotubular materials have been synthesized by different methods, i.e. anodic oxidation of Ti foils, hydrothermal process and atomic layer deposition of titania on carbon nanotubes. The effect of the different synthesis methods on the final characteristics of the nanotubular materials obtained have been evaluated by a detailed morphological and microstructural investigation carried out by SEM, TEM and XRD. Films of the synthesized nanotubular TiO

2

, deposited on QCM substrates, have shown a promising potential for the monitoring of hydrogen at room temperature.

The goal of this work was to design a sandwich assay with electrochemical transduction for the detection of a tumor marker, human epidermal growth factor receptor 2 (HER2), using a simple target capturing step by antibody-functionalised magnetic beads. The HER2 proto-oncogene is amplified and/or overexpressed in approximately 20–25% of invasive breast cancers. The assay is based on a sandwich format in which a primary monoclonal antibody anti-HER2 is coupled to protein A modified magnetic beads. The modified beads are then used to capture the protein from the sample solution and the sandwich assay is performed by adding a secondary monoclonal antibody anti-HER2 labelled with biotin. The enzyme alkaline phosphatase (AP) conjugated with streptavidin and its substrate (?-naphthyl-phosphate) are then used for the electrochemical detection by differential pulse voltammetry (DPV). The conditions for the antibody immobilization and for the protein binding have been first optimised. The performance of the assay in terms of sensitivity, reproducibility and selectivity has been studied in buffer.

A compact sensor for measuring multiple gas flows has been designed and fabricated. The device consists in a single silicon chip where three independent flow sensing structures have been included. The sensing structures are differential micro-calorimeters, equipped with double heaters in order to perform drift-free offset compensation. The chip includes also a versatile electronic interface including a low noise chopper amplifier and an original closed loop heater driver capable of reducing the effects of pressure variations on the flow measurement. The chip has been designed using the BCD6s process of STMicroelectronics. A post-processing step, based on anisotropic etching, is required to complete the smart sensor fabrication.

Field-Effect Transistors comprising layers of lipids have been developed and characterized from the electrical point of view. Lipid layers-OTFT are proposed as novel devices for perspective application in the detection of analytes from aqueous samples.

We have developed a prototype of a sensor able to detect and measure electric fields in the atmosphere. The atmosphere is a gaseous envelope gravitationally bound to the Planet. Different atmospheres have very different properties. For instance, the atmosphere of Venus is very thick and cloudy, and is responsible for producing the very high surface temperatures on that planet by virtue of its greenhouse effect. On the other hand, the Martian atmosphere is very sparse. Earth’s atmosphere is intermediate between these two extremes. It is distinguished from all other known atmospheres by its very active hydrologic cycle. One need merely examine pictures of Earth from space to appreciate the intricate cloud structures. Water in Earth’s atmosphere plays a very important energetic role. Because of its chemical composition, most incoming sunlight passes through Earth’s atmosphere and is absorbed at the ground. This heat is transported to the atmosphere through sensible heat and moisture fluxes. Upon condensation, this heat is then released into the atmosphere. The atmosphere may be conceptually divided into several layers, according to its thermal and ionization structure. The region where the temperature decreases because of the upward heat flux is called the troposphere. Above it, there is a layer in which temperature increases upward because of ozone absorption of solar radiation, the stratosphere.

In this work devices based on single palladium nanowire are realized by combining dielectrophoresis and focused ion beam (FIB) and characterized as hydrogen sensor at room temperature. Fixing the geometry of the electrodes, patterned by FIB, several devices are fabricated by varying the frequency of the applied field (DEP), to assess the effect on the shape of nanowire. Different kind of nanowire structures are, then, observed by means of SEM and AFM. The sensing mechanisms in presence of hydrogen are investigated and compared for each, finding that electrical current decreases because of palladium hydride formation.

The fabrication and characterization of SiC Schottky diodes for the detection of alpha particles at room temperature are described. A 5 × 5 matrix of diodes has been fabricated in order to verify the dependence of the device response on randomly distributed wafer defects. A dedicated exposure apparatus has been fabricated to test the detectors. Some preliminary alpha energy spectra obtained with the lowest reverse current diodes are shown.

The discoveries of giant magneto-resistance and spin-transfer torque effects are milestones in the history of magnetism. During the last two decades, they have fueled a conspicuous research activity in the field of nanotechnology, giving rise even to a new scientific branch, the spintronics, a neologism for spin-based electronics. From the very beginning, in fact, experimental results pointed out several potential applications of spintronic devices, such as magnetic random-access-memories, sensors, nano-oscillators, modulators and receivers working at microwave frequency. An overview of these devices will be here provided, emphasizing their behavior and the applications.

Pulmonary ventilation is an important and indispensable method used in lung surgery. Generally, during the operation it is necessary to exclude one of the two lungs from ventilation. To this purpose the characteristics of the actual bronchial blockers don’t let to exclude easily the lung during the surgical maneuvers. The difficulties evidenced during the anesthesia procedures by using a common blocker, have highlighted the need to find a new solution with alternative characteristics, such as to create an exclusion of the lung and at the same time to optimize the position of the blocker throughout the surgical maneuver.

A new Magneto-Optic Surface Plasmon Resonance (MOSPR) gas sensor is presented. This sensor is based on the combination of the magneto-optic effects of magnetic materials and the Surface Plasmon Resonance in metallic layers. Preliminary results proofed the enhancement in sensitivity of the MOSPR sensor with respect to traditional SPR sensor.

The aim of this paper is the realization of a novel bistable U-shaped micro-electro-mechanical system to efficiently harvest energy from ambient vibrations. The classical approach is based on vibrating mechanical bodies (linear systems) that allow for collecting energy through the adoption of smart materials, magnetic or electrostatic solutions. The idea pursued in this work is to consider the device vibrations biased by external vibration sources and also a double well dynamic in order to increase the harvest performances. The switching mechanism is based on a U-shaped structure that oscillates around two stable states when the stimulus is large enough to exceed the potential barrier. The device has been designed and realized performing a custom technology (BESOI) based on 15 ?m c-Si wafer. Numerical simulations and preliminary measurement campaign validate the nonlinear mechanism showing that the nonlinear system exhibits a behaviour suitable to harvest energy from ambient vibrations.

Flow measurements on silicon dioxide microchannels featuring inner cross-section as low as 16 ?m

2

and aspect-ratio as high as 50 have been performed using liquids with different dynamic viscosities. The microchannels, arranged in a square array with density of 1 × 10

6

channel/cm

2

, are embedded into a silicon substrate and connected to a reservoir grooved on the backside of the substrate. Flow measurements were performed by using an original, purposely designed system. In this work, details on both the measurement systems and the flow properties of such a small channels are reported and discussed.

An ultrasonic probe was developed by using, in conjunction, opto-acoustic and acousto-optic devices based on fiber optic technology. A Micro-Opto-Mechanical-System (MOMS) approach is proposed to realize the broadband ultrasonic probe on micromachined silicon frames suited to be mounted on the tip of optical fibers.

A novel optical biosensor realized in SOI technology has been proposed. A preliminary study involving common configurations such as ring- and disk-resonator has been carried out in order to design and then to test the new resonator, which we call hybrid resonator because it shows ring resonator shape and an optical behavior (in terms of Q factor) similar to the one of a disk-resonator. A detection limit of 5 × 10

?3

RIU has been demonstrated for the detection of glucose inside an aqueous solution.

Two different integrated transmitter topologies, each exploiting an on-chip loop antenna and implementing an on–off key (OOK) modulation, have been implemented using a standard 0.35 ?m CMOS process. The implemented transmitters use two different directly modulated oscillator topologies, namely a 2.5 GHz complementary cross-coupled LC oscillator and a 1 GHz current-starved ring oscillator, whose outputs are employed respectively to feed their own loop antenna. The cross-coupled LC transmitter and the ring oscillator topology consume, respectively, 22 and 4.4 mW from 3.3 V supply voltage. The average power consumption can be decreased to few tens of microwatt by duty-cycling the transmitters and by increasing the data rate of the packet to be transmitted up to 2 Mbit/s for the cross-coupled LC typology and 1 Mbit/s for the ring oscillator transmitter. The employed integrated small loop antenna radiate sufficient power for few meters communication range.

The aim of this work is to exploit an automatic system to make it easier, more quickly and costless the evaluation of Intracranial pressure (ICP) signal in cerebral pathology affected patients. The authors have developed a tool able to filter, analyze and extract features from ICP signal or recording. For the conducted study we have used the ICP MicroSensor, a catheter with a micro miniature silicon strain gauge type sensor mounted at one end and an electrical connector at the other end. We studied 16 continuous pressure recordings of different patients who underwent an infusion test. The digital signal processing (DSP) performed consists in: signal filtering, peaks identification, location of single pressure waves and extraction of features from each single wave. The outflow of the elaboration is composed by the 14 parameters trends which allows an easy analysis of intracranial pressure. It can be intended as a valid, consistent, reliable and easy-computing tool that might be used by the medical team in all those cases that involve brain damages or diseases.

Imaging sensors employing sub-millimeter waves and terahertz radiation (frequencies from 100 to 3000 GHz) are needed for security applications requiring stand-off, non-destructive sensing, due to its much larger penetration depth into dielectric materials.

In this chapter we present two different solutions of integrated photovoltaic energy harvesting, realized for discrete and continuous time working systems. The first solution is realized in a standard 0.35 ?m CMOS technology: it collects light energy from the environment, by means of 2 mm

2

on-chip integrated micro-solar cells, and accumulates it in an external capacitor. While the capacitor is charging, the load is disconnected. When the energy in the external capacitor is enough to operate the load for a predefined time-slot, the load is connected to the capacitor by a power management circuit. The second solution is realized in 0.35 ?m SOI CMOS technology. The energy harvesting elements consist of 35 trench-insulated

p

–

n

junctions, while the sensing system consists of a bandgap reference circuit, including an integrated high precision temperature sensor, and a high voltage low drop-out voltage regulator.

In this paper we present a 32-channel integrated front-end circuit for low-energy (0.5–100 keV) X-ray detection with a multi-anode silicon drift detector. The front-end circuit includes 32 read-out pixel cells (RPC), each consisting of a low noise preamplifier, a second-order RC-CR pulse shaper, a peak stretcher, an amplitude and a peak discriminator, as well as a reset and pile-up rejection circuit. Most of the parameters of the front-end circuit are programmable through a digital configuration register, supporting daisy-chain connection. At room temperature the equivalent noise charge of the RPC is 18.3 e

?

and its linearity error is lower than 5% over the complete input range. The front-end circuit has been designed in a 0.35-?m CMOS technology with main 3.3-V power supply. A single RPC occupies an area of 200 × 380 ?m

2

and consumes 0.4 mW.

In order to improve the efficiency in manufacturing complex Microsystems, a comparison between artificial and natural systems “growing” mechanisms and architecture have been investigated. As an example we have compared the process to fabricate a microelectronic chip with a size of ¼ of square centimeter and the biological process needed to make a similar size biological cell: a wheat grain. Just estimating the energy needed to make the two systems, we see that the energy balance differs of about three orders of magnitude. In fact, to make the silicon microchip of that size with a medium complexity, the energy used is more than 1 kWh, while a wheat grain energy need is less than 1 Wh. If we consider, following a common thinking, that the artificial processes are conceived as an emulation of the natural processes, this strong difference in the energy balance appears a quite strange surprise. Moreover, it is worth taking into account that the complexity of a biological eukaryotic cell is much higher than the microchip one. The understanding of mechanisms the biologic world uses to achieve its extraordinary efficiency, is very important to design cheaper artificial manufacturing processes to make systems more and more complex when the minimum dimensions the process is able to control inside the system goes in the range of nanometers.

A Quartz Crystal Microbalance (QCM) gas sensor coated with carbon nanotubes (CNTs) layered films as chemically interactive nanomaterial is described. A QCM resonator integrated on AT-cut quartz substrate has been functionally characterized as oscillator at the resonant frequency of 10 MHz. The CNTs have been grown by chemical vapor deposition (CVD) system onto alumina substrates, coated with 2.5 nm thick Fe catalyst, at a temperature of 750°C in H

2

/C

2

H

2

gaseous ambient as active materials for gas sensors. CNTs multilayers, with and without buffer layer of cadmium arachidate (CdA), have been prepared by the Langmuir–Blodgett (LB) technique to coat at the double-side the QCM sensors for organic vapor detection, at room temperature. It was demonstrated that the highest mass sensitivity has been achieved for CNTs multilayer onto CdA buffer material due to the greatest gas adsorbed mass. The sensing properties of the CNTs-sensors at enhanced mass sensitivity have been investigated for three different vapors of ethylacetate, acetone and m-xylene in the range of gas concentration from 10 to 800 ppm. The CNTs-based QCM-sensors exhibit high sensitivity (e.g., 5.55 Hz/ppm to m-xylene of the CNTs-multilayer) at room temperature, fast response, linearity, reversibility, repeatability, low drift of the baseline frequency, potential sub-ppm range detection limit.

A compact 2D wind sensor made up of an integrated, single chip, double channel flow sensor and a PMMA cylinder is proposed. The flow sensor is a standard micro calorimeter designed with a commercial CMOS process and thermally insulated from the substrate by means of a post-processing technique. The cylinder has two orthogonal active sections with an original channel configuration that connects the outer surface of the cylinder surface to the flow sensor. The optimization of the channel configuration allows to obtain a cosine dependence of the measured flow on the wind direction.

We report results on a field-effect induced light modulation at

?

= 1.55 ?m in a high-index-contrast waveguide based on a multisilicon-on-insulator (MSOI) platform. The device is realized with the hydrogenated amorphous silicon (?-Si:H) technology and it is suitable for monolithic integration in a CMOS integrated circuit. The device exploits the free carrier optical absorption electrically induced in the multistack core waveguide.

Improved niobium-based SQUID sensors in a magnetometer and a gradiometer configuration are presented. The SQUID magnetometer has an integrated square superconducting sensing coil with an area of 9 mm

2

, much smaller than a typical SQUID magnetometers keeping a comparable magnetic field sensitivity but a higher spatial resolution. At

T

= 4.2 K, an intrinsic magnetic field noise spectral density of 5.8 fT/?Hz, has been measured in the flux locked loop configuration. The SQUID planar gradiometer with a long baseline (50 mm) has a pickup antenna consisting of a series of two integrated rectangular coils inductively coupled to the SQUID in a double washer configuration. At

T

= 4.2 K a magnetic flux noise spectral density of 3 ??

0

/?Hz has been measured. The spectral density of the magnetic field noise referred to one sensing coil, is 3.0 fT/?Hz resulting in a gradient spectral noise of 0.6 fT/cm · ?Hz.

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. Due to the typical small chip dimension, only high frequency bands can use these antennas in optimum, i.e., resonating, conditions. Although the chip dimension do not allow resonant radiating elements, nevertheless this does not seem to be a limit for the specific application in contactless sensing, where a short distance wireless link is sufficient. In this paper an improvement of a wireless temperature sensor with on-chip antenna is presented. This solution, realized in 0.35 ?m CMOS technology, exploits a proportional to absolute temperature (PTAT) voltage scheme, where the difference between two base-emitter voltages under different bias current densities is constantly measured. The availability of bipolar transistors in CMOS technology allows to exploit their properties in temperature sensor applications. The signal is transmitted by a small loop antenna structure which is realized by aluminium deposition on the top surface of the chip.

In this paper we present a new configuration of an integrated optofluidic Mach–Zehnder interferometer based on liquid core ARROW waveguide that permits to obtain high sensitivity for liquid sensing. The proposed devices have been realized and optically characterized. The experimental results are in good agreement with the theoretical ones.

In this work we explored a simple, cheap and fast route to grow polyaniline (PANI) nanotubes arranged in an ordered structure directly on an electrode surface by electrochemical polymerisation. The deposited nanostructures were electrochemically and morphologically characterised and then used as a functional substrate for biochemical sensing by combining the intrinsic advantages of nanostructures as optimal transducers and the well known benefits of molecularly imprinted polymers (MIPs) as receptors. The hybrid nanostructured-MIP sensor was applied to the molecular recognition of catechol. Moreover, a gas sensing application was also investigated by exploiting resistance variation of the polymer in presence of different gases (CO, NO

2

, NH

3

and ethanol).

In this work, an ab-initio study of the electrical response to odorants of a self-assembled monolayer of a pig OBP immobilized onto a miniaturized Si-substrate equipped with gold interdigitated electrodes (IDE), was started. Electrical Impedance Spectroscopy (EIS) was used as electrical characterization technique and a dedicated experimental set-up was arranged in order to carry out EIS measurements in controlled environment. The EIS data was fitted by using a fitting software based on Levenberg–Marquardt (LEVM) algorithm to determine the equivalent circuit of the system.

In harbor water, the hydrocarbons pollution identification represents an important issue. Hydrocarbon presence derives from oil spills, for instance in bilge water, or it may come from industrial discharge. A prompt identification of oil presence is crucial for living beings and for the maintenance of a healthy marine environment. Both crude oil and fuels contain different fluorophores that under ultraviolet radiation exhibit a strong fluorescence which varies in intensity and hue. Fluorescence results mainly from the emission of aromatic hydrocarbons. Indeed, fluorescence spectroscopy is a widely used technique for characterization of oil samples.

The design and development of a new sensor prototype for hydrogen concentration detection in the fuel cells stream is reported. The sensor’s operation principle is based on the effects induced to high thermal conductivity of hydrogen, monitored by means of a PID (proportional-integral-derivative) control. The sensor is also implemented with a semiconducting layer which provides an additional output response. The sensor shows good linearity in the 0–100% range and it is suited to detect hydrogen in the stream of fuel cells with fast response.

A potentiometric urea biosensor based on urease (Ur) electrochemical immobilisation by poly(

o

-phenylenediamine) (PPD) is proposed. Polymer films have been grown by cyclic voltammetry on a glassy carbon (GC) electrode, using an unconventional “upside-down” (UD) geometry. GC/Ur-PPD electrodes exhibit a rapid (5–10 s) and sensitive response to urea concentration and lifetime of at least 5 weeks. Work is in progress to optimise the sensor and study its behaviour in the presence of possible interferences.

A simple and novel amperometric biosensor for glucose detection is proposed. It is based on the immobilization of glucose oxidase in a poly(vinyl alcol) matrix drop casted on a platinum electrode surface (Pt/GOx-PVA). The composite material GOx-PVA has been characterized by UV-vis spectroscopy to verify the preservation of enzyme structural integrity and of the enzymatic activity in PVA membrane. X-ray Photoelectron Spectroscopy (XPS) characterization revealed a homogeneous film deposited on Pt whose structure is preserved under operative conditions. Glucose was determined in the absence of a mediator used to transfer electrons between the electrode and the enzyme. Amperometric characterization has been performed at ?400 mV by using pulsed amperometric detection (PAD). Under the selected optimal conditions, the biosensor showed wide dynamic range (0.1–37 mM) yielding a low limit of detection (10 ?M). Biosensor performance was satisfactory also in terms of repeatability, reproducibility and anti-interference ability.

In this paper we report on the design, fabrication and characterization of an integrated-optic spiral resonator for angular rate sensing applications. The spiral resonator design has been optimized through a parametric analysis and a minimum angular velocity of about 10°/h, suitable for aerospace applications, has been theoretically predicted. The resonator has been fabricated in silica-on-silicon technology and characterized. Experimental results are in good agreement with the theoretical predictions.

In the present study we report the use of gold screen printed electrodes for the detection of the oxidized form of Benzo[a]pyrene via DNA based sensing. Benzo[a]pyrene-r-7,t-8-dihydrodiol-t-9,10-epoxide (DE–BaP) was the target molecule. Our approach consisted in the design of an electrochemical biosensor able to generate a response upon the formation of a stable adduct between DNA and DE–BaP. Such a device should be, in principle, able to predict the formation of an adduct between an immobilized DNA strand and the toxic molecule.

In this work, a glassy carbon electrode was modified with a methionine functionalized conjugated molecule, realizing a novel Hg

2+

electrochemical sensor. The overall assay scheme included an accumulation step, the electrochemical measurement and a regeneration step. All these aspects have been optimized including accumulation time, cleaning procedure and stability of the sensing layer.

An electrochemical flow injection analysis method for the selective determination of ortho-diphenols have been developed and optimized. The method is based on the use of sodium molybdate as an electrochemical mediator. The selectivity of the measurement has been evaluated with respect to different ortho-diphenols and phenols that are usually found in extra-virgin olive oil. After FIA optimization the protocol has been applied to the detection of olive oil samples and results were compared with a reference method.

Using thick-film technology on a ceramic substrate, a new tilt senor based on the heat transfer principle has been developed. The sensor is fabricated from ceramic materials and thick-film technology that results in an accuracy of about 2% full scale output, repeatability of about 0.2°C and thermal stability <0.2%/°C over a ±50° range. The TFT tilt sensor is capable of resolving less 0.1°. Finally, the sensor is inexpensive enough to be, in the near future, competitive with other types of commercial tilt transducer.

This contribution focus on the selection of sensor array for the use in olfactive nuisance detection and analysis inlandfill and industrial area chemical emissions monitoring. Electrochemical and polymer based sensors are tested for the use in electronic nose instrumentation for the selected application. Two sites, a landfill and an industrial sites are used as testing locations. Results support the feasibility of usage of a subset of the investigated sensors in such scenarios.

This decade have seen the development of a novel pattern recognition paradigm, named Artificial Immune Systems, based on peculiar features expressed by mammalian immune systems. Apart from some controversy, typical of a newly developed paradigm, AISs semmes to express interesting features that could be exploited also in the field of artificial olfaction. In facts, AO practitioners have been exploring the neural metaphors since years now but have never explored the potentiality of the immune metaphor. In this paper, we experiment the use of AIRS, an AIS based classifier, comparing its performance with the well established FFNN classifier in a typical AO setting. Results are quite interesting highlighting the possibility to introduce AIS in artificial olfaction exploiting their novel features, particularly as regards as drift impact reduction and internal knowledge representation readability.

Aircraft Maintenance Organizations are facing the needs for a significant technology innovation phase due to emerging novel standards and security needs. These are fostered by political and environmental situation characterized by strong commitments for security and “green aircraft” operations. Novel sensing technologies are at the core of this revolution being primary player both in the novel aircraft concept development and for the development of the associated novel maintenance standards. Authors are involved in these efforts by teaming up for the proposition of research initiative that will lead to the development of innovative operative supports and knowledge in the field of aircraft maintenance. In this contribution, key technologies and their state of the art are briefly identified together with their possible application. The technology oriented initiatives proposed by the authors companies are also introduced.

In the present paper a novel optical system for the monitoring and measurement of different analytes in Point of Care Testing (POCT) is presented. It is based on an optical biochip constituted by a two-piece polymethylmetacrylate (PMMA) chip, with 13 microchannels through which the analysed sample flows. The sensing layer, where the immunochemical reaction takes place, is located on the bottom side of the upper piece of the PMMA chip. All the electronic, optoelectronic and fluidics component are embedded in a portable instrument that is totally controlled by software. Preliminary tests on C-reactive protein (CRP) and procalcitonin (PCT) immunoassay are reported.

In this work, the applicability of luminescent porous silicon (PS) nanoparticles as ascorbic acid (AA) carrier has been studied. PS nanoparticles have been realized reducing in multi-sized particles porous silicon free-standing film placed in deionized water by sonication and filtering through 0.45 ?m membrane. The PS nanoparticles are water-soluble and highly fluorescent. PS nanoparticles are loaded by AA, monitoring the fluorescence spectra by a spectrofluorimeter. Before assessing the loading of AA into PS nanoparticles dispersed in water, the emission stability of PS solution has been acquired. Once stabilized the signal and loaded the AA, the presence and the real absorption of AA onto PS nanoparticles has been evaluated from emission quenching of the silicon nanoparticles.

The chapter presents an automated monitoring system for the detection of dangerous events of elderly people (such as falls) in AAL applications. In order to provide a self-contained technology solution not requiring neither the environment rearrangement, nor the presence of specialized staff, nor a priori information about elderly characteristics/habitude, the focus is placed on the classification of human postures and the detection of related adverse events. The people is detected through a non-wearable device (a TOF camera), overcoming the limitations of the wearable approaches (accelerometers, gyroscopes, etc.) for human monitoring (the devices are prone to be incorrectly worn or forgotten). The system shows high performances in terms of efficiency and reliability on a large real dataset of falls acquired in different conditions. The posture recognition is carried out by using a topological approach on the 3D points cloud. Experimental results validate the soundness of the posture recognition scheme.

In this work the interaction of the pesticide carbaryl with two groups of biomimetic ligands, peptides and MIPs was screened by multiple minima hypersurfaces (MMH) procedures, through the AM1 semiempirical method. Data related to the properties of the molecular association of the complex biomimetic ligand-pesticide were obtained and compared with another molecular modeling algorithm named Leapfrog, as included in the Sybyl software package, and experimental results from the literature, remarking good correlation between them. All important MMH program parameters (cells number, box size, conformers) were studied and optimized with the aim of getting the minimum computation time without losing the correlation with experimental data. The data demonstrated that MMH approach can be used as a fast biomimetic ligand screening tool for MIPs. In the case of peptides the computation time was not comparable with the molecular dynamics methods conventionally used for this approach.

A novel imprinting scheme, combining for the first time electropolymerization with metal-ion coordination, has been proposed. A MIP for a pesticide (4-(2,4-dichlorophenoxy)butyric acid (2,4-DB)) has been prepared from a Co-porphyrin (Co(III)tetrakis(o-aminophenyl) porphyrin (CoTAPP)) as functional monomer. Such an approach aims to combine advantages of electropolymerization with ones related to the use of metal complexes in imprinting procedures. After verification of template entrapment and subsequent removal by XPS spectroscopy, the imprinting effect was verified by comparing electrochemical responses of MIP and not-imprinted polymer (NIP) tested by Cyclic Voltammetry (CV). MIP revealed an enhanced electrocatalytic activity towards 2,4-DB reduction as well as a good selectivity against both pesticides and structurally related compounds.

In this work, a wireless energy consumption monitor made up of a current transformer with its analog interface and an 8-bit microcontroller that acquire sensor’s data is presented. The whole system is wireless connected to a PC through a Bluetooth module for the sending of the data that are managed and collected by the host software developed in LabVIEW, a multiplatform graphical programming environment. A digital programmable potentiometer have been used to allow the system’s electronic to dynamically tune the sensitivity of the measurement by means of the firmware implemented in the ?C that let to obtain both result accuracy and a fast convergence of the algorithm. The entire design address the need of the reduction of the electronic system’s energy consumption with the utilization of advanced low power technique both hardware and software.

The pervasiveness of RFID technology in novel application fields, such as agriculture and food chain integrated management, is related to the addition of sensor and computational capabilities to the systems, and as a consequence, their powering become a challenge. Passively powered devices, such as inductively coupled passive HF RFID systems, utilize an external electromagnetic field to operate without an internal power source. This paper presents a battery-less RFID sensor useful to create a safer and more manageable food supply chain of perishable comestibles.

The fate and the behaviour of nanoparticles in seawater, which is the ultimate sink for any release of nanoparticles, is a very important issue for the assessment of their environmental impact. Despite this concern, only few studies regarding the ecotoxic effect of NPs upon marine organisms were conducted. In this work the dispersion behaviour of NPs in a seawater matrix has been investigated and their physicochemical properties characterized. The ecotoxicological impact towards marine organisms of several nanoparticles has been also examined.

A fiber optic setup for diffuse-light absorption spectroscopy in the wide 400–1700 nm spectral range is experimented for detecting and quantifying the adulteration of extra virgin olive oil caused by lower-grade olive oils. Absorption measurements provide spectral fingerprints of authentic and adulterated oils. A multivariate processing of spectroscopic data is applied for discriminating the type of adulterant and for predicting its fraction.

We report the results of a load test performed on a road-bridge. In particular, the tests were performed by a portable prototype based on stimulated Brillouin scattering (SBS) in optical fibers. The optical fiber sensor, previously attached along the steel beam, was able to provide the strain profile along the structure, with a spatial resolution of 3 m and a strain accuracy of ±20 ??. A comparison with finite-elements-method simulations, as well as with data collected by vibrating wire strain gauges, permitted to confirm the validity of the SBS-based approach in monitoring the deformation of large structures.

The achievement of proper electrochemical performance in proton exchange membrane fuel cells depends on a number of factors, among which the difficulty in obtaining a uniform pressure distribution over the whole fuel cell active area. For a given stacking design, contact pressure levels are usually controlled by selecting an appropriate external clamping pressure on the endplates. Hence, the actual out-of-plane deformation of the endplates is believed to play a critical role. The goal of this study is to investigate this aspect by using an optical full-field measurement technique based on stereoscopic digital images correlation. The preliminary results reported in this paper, obtained by testing a PEMFC with 13 mm thick Cu endplates, shows that the endplates bend noticeably under loading, leading to an uneven distribution of the out-of-plane deformation field.

The temperature-dependent UV spectroscopy and thickness shear mode acoustic method were applied to study of thermodynamics and binding properties of DNA aptamers sensitive to thrombin depending on the substitution of bases in G-quadruplex. The substitution of thymidines by adenines in TT and TGT loops of G-quadruplex resulted in destabilization of aptamers and in decrease of sensitivity to human thrombin.

A new type of Epoxy/CNT composite has been fabricated based on bisphenol A-epoxy resin, loaded with 0.5wt% of commercial multiwall carbon nanotubes. Exploiting the resulting high conductivity of this composite material, we tested the possibility to use it as absorber of electromagnetic waves at microwave frequencies up to 25 GHz. For this purpose the sample, to be tested, was placed as substrate of a microstrip transmission line. Measurements of the scattering parameters, done with a vectorial network analyzer, have been used in order to obtain the power absorption (PA) spectra. Special attention was paid to the optimization of the microstrip geometry. A comparison of the PA spectrum with the absorption spectra of commercial cavity absorbers showed encouraging results, regarding the microwave absorption capability of the new nanocomposite material.

In the last years the global energy economy hangs in the balance, pushing up the research interest in novel and renewable energy sources and in innovative engines able to improve performances saving the efficiency. This frame requires the development of power electronics subsystems and the continuous increase of working temperatures; hence reliability has become the most critical requirement for any new device design. The temporal evolution of temperature distribution on the surface of a power electronic device undergoing an exerted stress plays a fundamental role in studying and improving reliability. A suitable scanning measuring system has been realized in order to allow the analysis of fast transient states and the localization of “hot-spots” which could be a cause of a premature failure and unreliability of the devices.

The most popular micromirrors switches, work with a sinusoidal low-frequency carrier obtained by a simple generator with a rude shift-level circuitry. Aiming to the problem for the pulsed rectangulars carrier signals, more and more used in the digital and scanning bonded silicon mirrors, the analog amplifiers arranged to operate in a saturation region, decrease the sharpness of leading and trailing edges of a rectangular pulse envelope (i.e. audio amplifiers). This approach makes unusable a set of features of these actuators. The well-known systems, based on high-voltage logic ports, capable of resulting an output carrier that having the shape substantially a square waveform, require large current and are very expensive. In the proposed architecture, it is possible to reduce both the excessive and unnecessary spectral components resulting from the rapid rise and fall time of the rectangular envelope as also relax the current requirements with a dedicated circuitry arrangement that modifies the output source in a trapezoidal envelope. A new scheme for decreasing power requirements using a source degenerated logic port is introduced. This method, addresses these issues by tracking the output current with a very simple approach that doesn’t require an additional consumption as most solutions do.

After recent research carried out by our team aimed at developing new immunosensors for lactoferrin, in the present note are reported the results of research carried out to determine the constant of affinity between Lactoferrin and the corresponding antibody (human anti-lactoferrin). In addition, a detailed investigation was made of immunosensor selectivity and the cross selectivity of the immunosensor developed towards the principal proteins present in milk which are considered as possible interference in Lactoferrin determination in milk and its derivatives, or in saliva.

Continuation of our team’s study of olive oil rancidification carried out in recent years using ad hoc biosensors. While in the preceding research the thermo-oxidative decomposition of extra-virgin olive oil (EVOO) at high temperatures was investigated, in the present work the aim was instead to make a more in-depth study of the principal processes that occur when an oil sample is artificially rancidified isothermally at 98°C in a air stream, using the classical American oxygen method (AOM method, official method). The principal processes taking place were essentially monitored using three different organic phase enzyme electrodes (OPEEs) as well as by two other ancillary non biosensor methods. Furthermore, the present research was not limited to the study of EVOO. The kinetic investigation using biosensor methods was extended to include olive oil (OO) and olive oil residue (OOR).

The combined use of peptide nucleic acid probes and ultrasensitive nanoparticle-enhanced SPRI detection is shown to allow the ultra-sensitive detection of non-amplified genomic DNA.

An in vitro study to assess toxicological properties of buckypaper made from multiwalled carbon nanotubes is presented. Human peripheral blood lymphocytes have been chosen as cell model, and cytotoxicity has been investigated as it is a crucial factor in understanding the mechanisms of action of nanomaterials on cells and tissues. Buckypaper treatment has resulted in a reduction of cell growth of phytoemaglutinin stimulated human lymphocytes. In view of the potentially widespread use of this nanomaterial in pharmacological and biological applications, for which injection into human body is foreseen, we believe the results of the present study can contribute to the knowledge of the human health risk related to the use of buckypaper.