Sensors and Microsystems

Lactate is used as a biomarker of the tissue oxygenation level for the evaluation of different pathologies or for the assessment of physical performances. The present work describes the application of a previously developed platform for the colorimetric enzymatic detection of l-lactate using a smartphone-based technology. The sensor is based on the lactate oxidase-horseradish peroxidase (LOx-HRP) enzymes immobilized by adsorption on a poly (aniline-co-anthranilic acid) (p(ANI-co-AA)) composite polymer. The unique colorimetric properties of this film were exploited for the detection of lactate using a reversible redox reaction catalyzed by the adsorbed enzymes, which generates a color change of the polymer from green to blue only when the substrate is present. The sensor response, consisting in changes of the polymer optical features, was easily evaluated using the free-of-charge Color Grab application for Android OS installed on a smartphone. The developed sensor was optimized in regard to several experimental parameters and the color variation of the polymer was also monitored by spectrophotometric measurements. Finally, the developed biosensor was employed for the detection and quantification of l-lactate in different media relevant for clinical practice.

This paper presents a study on a Lab-on-Chip system based on the optical interaction between biological material and optical devices for the detection of analyte’s properties inside a solution or mixture. The reported LoC performs both interaction and detection phase in the same chip, taking advantage of a polymer waveguiding structure optically coupled with a thin-film amorphous silicon photodiode fabricated on a single glass substrate. Before its actual implementation in biomolecular recognition applications, we report a feasibility study on the detection of fat content in milk, carried out by interpolating simulated data with the measured electro-optical response of the sensor. The sensing demonstration highlights a limit of detection of 106 ppm and a sensitivity of about 8.7 pA/(g/dL), encouraging further developments and an actual implementation in food quality control.

The AstroBio CubeSat (ABCS) project aims at the development of a Lab on Chip (LoC)-based payload engineered for astrobiological researches. ABCS 3U CubeSat will be launched in early 2022 and will operate within the internal Van Allen belt, at an altitude of about 6000 km. Given ABCS harsh space operational environment, payload assembly was designed to be as much dependable as possible. Analytical approach, design, assembly, integration and test were implemented, and on-ground validation confirmed payload data acquisition.

We present a feasibility study on biological tissue and cell manipulation by a novel, multi-hinge microgripper characterized by high dexterity and complex in-plane tips displacement, while being at the same time highly compact and easy to manufacture via MEMS technology. The device was obtained by combining selective flexibility with planar fabrication technology and has been developed to propose new solutions for miniaturized, inexpensive, energy-efficient, effective and accurate manipulation at the micro-scale. The presented study consists of a direct morphological comparison with real-life cardiac and lung tissue samples, and was accomplished via in-vitro microscope observation. The results highlight the function capability of manipulating, grasping and clamping objects having a size of 50 to 150 µm, including muscle fibers, blood vessels and cells, encouraging further developments toward an in-vivo scenario with actual biological material.

The presence of harmful chemicals and microorganisms in food is often addressed to food contamination, which can cause consumer illness at different levels of severity. Aptasensors can become a helpful tool in the detection of contaminants and allergens as a highly sensitive and easy-to-use analytical procedure. Moreover, the introduction of nanostructured systems allows the miniaturization and the portability of the devices, which make them suitable for on-field screening analysis. The aim of this manuscript is to give to readers an overview on the most recent important achievements of our research group in the realization of electrochemical aptasensors to be applied in food analysis.

The development of a system consisting of a device based on a fuel cell for ethanol, coupled to yeast cells (Saccaromyces Cerevisiae), has been completed. Through the use of a potentiostat, connected to a PC, the optimization of the system was then carried out by studying the type of yeast to be used and by monitoring the power curves obtained. The device was then used for the determination of glucose in test solutions and for the detection of the “pool” of carbohydrates in commercial soft drinks.

We present the development of a compact, easy-to-use device that implements a 3D microfluidic network with sensing sites, based on impedance spectroscopy techniques. The aim is to provide a Lab-on-Chip approach in applications where classification of microparticles is required, as well as morphological and volume studies. A complex colloidal mixture made of cell-resembling agarose microbeads suspended in aqueous medium was arranged to carry out microfluidic and impedance spectroscopy tests on the device. Preliminary impedance measurements show the effectiveness of the counting sub-system, displaying a good sensitivity in detecting the passing of a single bead over a sensing site. These results confirm the effectiveness of the system, and encourage further developments toward an implementation in actual biomedical scenarios. Possible applications can be found in 3D cell-cultures monitoring, blood analysis and diagnosis and blood-related diseases.

The development of microfluidics-based devices has opened the way to tremendous advances in many different biomedical contexts, as for example, organ-on-chip (OOC) experiments. However, to exploit the full potential of this technology, the integration with sensors and the analysis of experimental data are also necessary. In this paper, some examples of how we can improve the OOC performances through the development of ad-hoc sensors and the application of machine learning algorithms to process the huge amount of data collected in the OOC experiments are shown.

A long period fiber grating was fabricated, characterised by the maximum enhancement of the evanescent field by means of the exploitation the lowest order LP0,2 cladding mode (CM) near turn-around point (TAP) in water medium. A thermostated closed flow cell was designed for sensor characterization and immunoassay implementation. The sensor was characterized by surrounding refractive index (SRI) sensitivity within RI range from 1.333 to 1.3335 and the sensitivity was found to be 8751 nm/SRIU with a resolution of the order of 10–5. Immunoassay was performed by immunoglobulin G/anti immunoglobulin G (IgG/anti-IgG) interaction in human serum and a limit of detection (LOD) of 0.16 ng/ml (1.06 pM) was achieved.

Here we present an analysis on a class of metasurfaces based on Titanium nanocommas, that features a relevant circular dichroism, a highly sought-after characteristic in sensing applications. Our study includes extensive simulations and an evaluation of the challenges for the samples fabrication. Our numerical results reveal promising values of dichroism in ultraviolet and visible frequencies, which further validates the use of Titanium for this type of devices, in addition to its biocompatibility. We also show the variations of the behaviour related to the superficial oxidation of the metal. Details, results and guidelines from the fabrication processes are presented.

Carbon dots, thanks to their surface functional groups are able to coordinate Eu(III) ions sensitizing the luminescence coming from the lanthanide excited states. We prepared C-dots from solid olive waste, and assembled them in a new CDs-Eu(III) complex, in aqueous solution. The new species is able to transduce the presence of protons into a dual optical signal working as H+-sensor in the 6–2 pH range.

Not only air pollution can affect men’s health, but it can have a detrimental impact on solar irradiance reaching the earth, resulting, for instance, in a decrease of photovoltaic plants energy yield. In this paper a theoretical model is proposed to evaluate the effect of air pollutants on solar irradiance using data measured at ground level. The model has been applied to the case of NO2 pollution in Acerra, a small town near Naples (Italy) where data have been collected for two years. It is found that NO2 has a negligible effect on solar budget, at least with respect to other pollutants such as PM2.5.

A VOC 4-sensor array was applied to the analysis of blood samples collected from healthy young men living in two known Italian contaminated areas, i.e. Land of Fires (LF) and Valley of Sacco River (VSR). Data processed by Multivariate data analysis (PCA and Discriminant Analysis) showed a distinguishing between the two areas. The preliminary results stimulate the research towards new analyzes and more extensive biomonitoring campaigns in these areas of interest for health protection.

Even though several classes of materials have been investigated for chemical sensors applications, one-dimensional metal oxides (1D MOX) have considerable advantages. Especially, MOX nanowires (NWs) show physicochemical properties that allow them to overcome the drawbacks of traditional thick and thin film-based gas sensors such as low sensitivity and signal drifting due to the grain coalescence. As a result, nanosized 1D MOX are considered one of the best materials to fabricate new generation of chemical/gas sensors. This review attempts to collect the significant results achieved at SENSOR Lab, Brescia (Italy) on the synthesis of 1D MOX for chemical sensors applications. In particular, the bottom-up strategy to grow 1D MOXs (nanowires-like structures) mainly adopted by SENSOR Lab is the evaporation condensation technique. 1D MOX may be produced by using two different mechanisms, Vapor Liquid Solid (VLS) which employs a seed catalyst to assist the 1D growth and, Vapor Solid (VS). The synthesized nanowires are uniform, dense and have a high aspect ratio with diameters as low as few nanometers and length of tens of micrometers. Many gas sensors based on 1D MOX are produced including p-type semiconductors such as NiO and n-type such as ZnO, SnO2, WO3 and In2O3. They exhibit excellent sensitivity, high stability and fast response towards hazardous gases including toxic and flammable compounds such as NO2, NH3, acetone, ethanol and H2.

This review work reports the synthesis, the morphological, structural, spectroscopic, and electrical properties, the sensing performances of TixSn1-xO2 solid solutions, using pristine SnO2 and TiO2 as reference. Each characterization highlighted two behavioral classes for the solid solutions: SnO2-like and TiO2-like, being the oxide with x = 0.25 the borderline sample. Furthermore, two real applications of (Ti, Sn) solid solutions are described: i) in air quality monitoring to detect carbon monoxide (CO), ii) to detect the variation of analytes concentrations in samples of hydraulic fluid headspace collected during the system running.

Films of multiwalled carbon nanotubes (MWCNTs) are proposed as the sensing element of low-cost sensors for the detection of temperature, pressure and water droplets. Liquid solutions of functionalized MWCNTs are vacuum filtered to produce freestanding films of randomly oriented MWCNTs, known as buckypapers, which are patterned in strips of several mm size. The electrical conduction of the buckypaper is highly sensitive to the environmental conditions. It increases for rising temperature or when a pressure is applied; conversely, it is decreased under tensile strain or by exposure to water droplets. The experimental data presented in this work confirm the suitability of buckypapers for multipurpose sensors able to detect different physical quantities simultaneously.

An overview on metal ions detection in water exploiting polymer optical fiber (POF) sensors is presented. A simple and highly sensitive plasmonic sensor in POFs has been functionalized by different specific self-assembled monolayer (SAM) receptors to achieve the specific detection of several metal ions in water. In particular, the detection of uranyl, copper(II), and iron(III) ions is reported here. The developed optical fiber sensors have been demonstrated to be effective for determining these metal ions in water solutions in µM ranges, even lower in the case of uranyl ion (tens of nM).

Optical spectroscopy is a successful technique for assessing the quality and safety of intact food. It is a photonic tasting, as the food can be checked in real time by means of a light bean, without sampling and without the need for intermediate chemistry, thus providing a green analytical tool. The most effective instruments for spectroscopy available in our laboratory are presented, together with some successful applications to food analysis. They range from bulky instruments for Raman spectroscopy to custom and peculiar devices for turbidity-free absorption spectroscopy of liquids, to pocket colorimeters and fluorimeters, and to the most recent handheld smartphone-connected spectrometer for applications in low-resource settings.

Hybrid materials made of organic and inorganic elemengts are gaining interest in many technological fields from light conversion to sensors. In this paper, the case of porphyrnoids and ZnO nanoparticles is considered. These materials are suitable to be applied with transducers based on different principles and the resulting sensors show the interplay between light sensitivity and chemical sensitivity and selectivity. These properties result in sensors behaving rather differently respect to the individual constituents of the hybrid material. Among the routes to prepare hybrid materials we investigated two approaches: the first based on a one pot growth and the second, more conventional, where the organic layer is applied to the well-formed nanoparticles. Preparation protocols and porphyrinoids structure influence the overall sensing properties of materials, thus, these sensors show promise to be implemented as an electronic-nose that combines selectivity to strong electron donors and broad-selectivity towards the other classes of chemicals. Some study cases are reported where real context applications have been simulated to highlight the potentialities of these materials as alternative to porphyrin thin films.

Limit values for occupational exposure to chemical agents are based on the hazard classification of the substances, which does not necessarily coincide with the actual occurrence of a health damage. The very low incidence of occupational diseases related to exposure to volatile chemicals registered in Italy is probably the result of the combination between a poor exposure assessment and difficulties in diagnosis, classification and communication. The use of automated specific, robust and reliable real-time strategies would lead to a noticeable improvement in assessment and control of this health risk. Direct reading detectors with specificity and sensitivity compatible with the occupational exposure limit values could be a powerful tool for determining, in real time, the processes, the areas or the moments in which airborne concentrations of hazardous substances are produced and which workers are exposed to higher risk for their health.

Metal Oxide Semiconductor (MOS) gas sensors are suitable for many applications in different industries. They can be considered low-cost sensors in comparisons with devices based on different sensing technologies. In this paper we are exploring the potential of the integration of MOS sensor with other sensing capabilities like relative humidity and temperature in a unique combo device together with an application specific integrated circuit (ASIC). The incremental complexity of such device is paid back by the wide advantages and benefits. The potential of power reduction, low noise, the enhancement of selectivity by detecting the VOC fingerprints represents only a part of many advantages that this integration is offering. Moreover, this paper introduces an innovative dynamic view called R2C that exploits gas sensor hysteresis. It has the clue in the full programmability and control of STMicroelectronics MOS based VOC sensor. This innovative 3D data view opens the door to the exploitation of this combo device in many application fields and contexts, including the e-nose as well.

The interesting properties of gold nanoparticles (AuNPs) have stimulated their increasing applications in various research fields such as nanotechnology, materials science, and sensing. To this purpose the immobilization of gold nanoparticles on suitable transducers surfaces is still under study. Aim of this work was to optimize the adhesion and distribution of colloidal gold nanoparticles on glass substrates suitable to generate a nanostructured plasmonic transducer for sensing application.

A great challenge in the area of gas detection for new applications is the development of devices which are user-friendly, robust, with low detection limits and allow fast analyses. Conductometric gas sensors possess many of these requisites and have been used from more than half century in a variety of application fields. In this paper we highlights the potential of novel conductometric sensors under development in ongoing projects at the Sensor lab of the University of Messina. Through these examples, new domains in the applications of gas sensors are foreseen.

Based on the Project S.A.L.V.O. that aims to realize a new, smart technology, partly wearable, for the safety of workers and workplaces, bringing together wireless localization systems, low-energy artificial intelligence techniques and innovative sensors to detect harmful gases and fine dust. This work illustrates a first characterization campaign for the gas sensor candidate. Metal Oxide Gas Sensors (MOX) are the most suitable gas sensor typology thanks to their miniaturization and high sensitivity. ST microelectronics produced a miniaturized MOX prototype that can be evaluated and optimized for the Project. In the preliminary stage the gas sensor is classically conditioned and exposed to Methane and Carbon Monoxide. The output response is measured also under an environmental humidity change and response to humidity itself is also evaluated. Results illustrate the arising crucial-points for the optimization of the device.

This work presents the humidity sensing features of MoS2 prepared by a hydrothermal method. A peculiar pattern of the detection responses in the entire range of RH (from 0% RH up to saturated environment) and the inversion of the conductance variation between the conditions of low and high water concentration was observed, suggesting the presence of different detection mechanisms.

Biometric recognition systems based on 3D information of palmprint have been experimented with in the last years. Optical technology is the most widely used, but it provides information on the external surface only. Ultrasound, instead, allows obtaining information that accounts for principal lines depth. In this work, a 3D palmprint recognition system, based on images acquired through an Ultrasound system by using water or gel as a coupling medium between the probe and hand, is proposed and tested. In both cases, a 3D template that contains information on the depth of principal lines is generated by combining 2D templates obtained from images extracted at various under-skin depths. The performances of the system have been evaluated through verification and identification experiments on home-made databases of 633 water samples and 423 gel samples, respectively. For both cases, the 3D method reports better results than the 2D one. Furthermore, the recognition capability of the proposed system is comparable with that of the best optical system reported in the literature.

We designed, fabricated, and tested a UHF RFID-based wireless system for electromyographic sensing, differently from the usual RFID employment on TAGs. The design leads to a fully integrated system, not electromagnetically interfering with the analogic part of the board, thus preserving the very low signal coming from the electromyographic activity of the muscles. Whilst wireless transmission usually represents the greater power contribution, our solution has the advantage of a compact design to easily implement data transfer passive communication, without onboard energy consumption. We optimized the analog output of the EMG sensor to properly interface the input of the analog to digital converter that is embedded in the RFID chip. A test exploiting three hand gestures confirmed the expected results, and the collected and transmitted EMG signal is compliant with the same signal sampled with an oscilloscope, thus promoting further advancements to reduce the overall system dimensions and the analog power requirements.

Tactile sensing has become crucial in robotic applications such as teleoperation, as it gives information about the object properties that cannot be perceived by other senses. In fact, it is essential that robots are equipped with advanced touch sensing in order to be aware of their surroundings and give a feedback to an operator. Such sensing systems are made of sensors and an elaboration unit that acquires tactile signals and process the data, retrieving information such as texture, hardness, and shape. In this paper, we propose a novel tactile sensing system made of flexible, high sensitive and high spatial resolution piezoelectric polyvinylidene fluoride‐trifluoroethylene P(VDF-TrFE) sensors, and a low power and low cost Interface Electronics (IE) that can acquire data from 32 channels simultaneously with a sampling frequency of 2KSamples/s. We validate the system acquiring data from three different objects to classify their hardness using an artificial neural network of one hidden layer with approximately 89% accuracy. The signal processing and the classifier will be hosted by the IE in the next future.

In the field of MEMS and sensors, package has also to allow the ‘sensing’ of external ambient without influence the measurement of the target physical quantity. It follows that package plays a primary role since it may strongly affects the device behavior and performance. Depending on the application and mission profile, design and package technology need to be targeted in order to fit the best the given requirements.Ceramic cavity packages limit the stress transfer to the MEMS due to the high mechanical stiffness and to the coefficient of thermal expansion that can be considered matched versus that of silicon sensor ensuring high performance in terms of stability. On the opposite the thermomechanical parameter of ceramic are in discrepancy with the one of PCB and this lead to a higher stress on the solder joint between component and board.In this paper it is presented a package structure that has the target to achieve the best tradeoff between device stability and reliability requirements. The introduction of a Silicon Interposer add a degree of freedom to the structure allowing the possibility for an optimal material and design.Numerical analysis has been performed to properly design the package. Correlation with a study on full device with field displacement characterization technique based on digital image correlation (DIC) is demonstrated.

Poling procedure is mandatory for the mechanical, piezoelectric and ferroelectric stability of piezoelectric material including PZT, standard piezo layer for ST MEMS devices.Without poling step the devices will suffer instability and even large variation of ferroelectric and mechanical parameters. Of course, this implies a deep study for each specific application to prevent this variability. The paper here described illustrates a convergence method to find a minimum sensible parameter’s set allowing a fast discrimination between all possible poling tests. The aim is the convergence towards the best “poling routine”. Best in terms of minimum effort (time, T and bias) for stable and reliable poling treatments. Moreover, some of the changes induced by a “stable poling routine” have been demonstrated to improve the response of acoustic devices in terms of SPL and THD.

In this paper, we demonstrate the use of a graded-index perfluorinated optical fiber (GI-POF) for distributed static and dynamic strain measurements. The system is based on a Coherent Optical Time-Domain Reflectometry (C-OTDR) configuration operating at the wavelength of 850 nm. Static strain measurements are carried out by exploiting the increase of the backscatter Rayleigh coefficient consequent to the application of a tensile strain. Dynamic strain (vibration) measurements are also detected along the same fiber, exploiting the vibration-induced changes in the backscatter Rayleigh intensity time-domain trace.

We proposed and addressed methods for using multiple energy harvesting strategies to power a wearable sensory glove. The capabilities of piezoelectric and thermal energy harvesters were reported, with hand motions and body heat used to these goals. A potential multi-input single-output DC-DC architecture was proposed to harvest energy from the two sources, and power analysis results were used to assess the harvesting system viability in terms of the amount of gathered power required to power the target applications.

We report the field emission characterization of graphene flakes deposited on SiO2/Si substrates. Electrical measurements are performed inside a scanning electron microscope provided of nano-manipulated metallic probes exploited as electrodes either to contact the flakes or as anode to collect electrons in field emission configuration. We demonstrate that local electric field as high as few hundreds V/µm allows to extract a current from the top of the flake. We also demonstrate a horizontal field emission device in which the electrons are extracted from the edge of the flake.

Barium Zirconate Titanate-Barium Calcium Titanate (BZT-BCT) has been proposed as an alternative material to toxic lead zirconate titanate (commonly referred as PZT) for the production of micro-electro-mechanical devices based on piezoelectric thin films. Among the possible fabrication methods, sol-gel is the most adoptable and cost-effective technology. To produce good quality films, the homogeneity of the solution is a key factor. For this purpose, 2-methoxyethanol (a toxic, carcinogen solvent) is widely used, although such approach affects the environmental sustainability of the fabrication process. This work deals with the development of a “green” high stable precursor solution based on non-toxic and non-carcinogenic solvents. Results showed that a highly stable, homogeneous solution has been produced thanks to a thorough reagents dehydration. By depositing such solution on commercial platinum-coated wafers, thin layers with homogeneous morphology and improved electrical stability have been produced.

We implemented a Bluetooth Low Energy system concerning the acquisition, encryption, wireless transmission, and reconstruction of the electromyographic signal for prosthetic control. The system is expandable with other devices supporting Bluetooth and is a valuable alternative to the current proprietary implantable EMG systems, which use restricted protocols and ignore data security. The adopted system-in-package has ultra-small dimensions and encloses an integrated antenna, thus additional space in the implant or the prosthesis is not required. It includes peripherals embodying advanced solutions for buffering the signal and prosthetic control, including wired digital protocols, Bluetooth, and analog signal reconstruction features. All this embracing the development for the next generation of myoelectric prosthetic control.

We designed, fabricated, and validated a piezoresistive bending sensor, a fundamental component of wearable electronic devices for monitoring human motion. The most diffused opaque carbon-based resistance flex sensors suffer from low detection for small bending angles. The sensor we here present is based on a semi-transparent active material (fulleropyrrolidine bisadducts polymer) and has the remarkable advantage of good electrical properties for low bending angles. The fabrication steps are effective since a pre-patterned ITO/PET surface is functionalized by chronoamperometric deposition, and the silver electrical contacts are inkjet printed. We propose a fitting function of the measured thin film resistance curve vs. the bending angle, showing promising properties as a complimentary bending sensor to the most diffused flex sensors. The results pave the way to new applications and more performant wearables.

Thanks to the widespread availability of sensor data, it is today possible to accurately predict anomalies in machinery functioning, preventing so potential breakages, downtime, and poor quality of products. In the case of punching machine, it is important to monitor the surface of the punch tool in order to detect abnormal incipient deformations. This paper addresses the problem of model building when only few punch-tool samples are available for model training. To this end, sample data are augmented by generating synthetic deformations and then using, hybridlike, both synthetic and real data for model training. The feature extraction process relies on the new concept of Profile Integration Matrix, which accounts for punch-tool surface deformations. Using the Profile Integration features, the predictive model is based on the supervised classifier one-class Support Vector Machine. The achieved results are promising, showing accuracy rates of 97.4% with hybrid data and of 97.7% with synthetic data.

The paper investigates the temperature dependence of the electrical characteristics of an organic thin film transistor (OTFT), through the development of an analytical model based on the MTR (multiple trapping and release) mechanism, that is related to an exponential density of states in the organic semiconductor layer at the insulator interface. The aim is to realize a simple single-ended organic sensor, consisting of a diode-connected OTFT, with a high sensitivity and linearity in a wide temperature range (from 230 to 330 K). The fabricated sensor shows the maximum linearity of 99.95% at a bias current of 22 nA with a sensitivity of about 100 mV/K, exceeding that of silicon-based sensors, and a good stability with an error lower than 1%. The model used to describe the device behavior demonstrates that the linearity is given by the compensation of two non-linear functions of temperature.

Vibration data analysis is an effective method for assessing internal fault in transformers. Recently, neural network classifiers have been successfully proposed as a tool for the detection of loss of clamping pressure of the winding pack in transformers under load operating condition. In this paper, we extend this approach to the case of unloaded transformer, where, unlike load operating conditions, vibrations are mainly driven by the core. This investigation has been carried on with vibration data experimentally collected with a lab equipment constituted by an oil insulated transformer, either under no fault (tight winding pack) or fault (loose windings) conditions. The analysis proves that the fault can be still reliably detected with a high accuracy, robustly with respect to a possible misplacement in the positioning of the sensor.

Three different approaches for the analytical detection of fluids by means of rectangular glass micro-capillaries working in the near infrared wavelength region are presented. At first, a non-specific refractometric measurement for the detection of glucose concentration in solutions is reported, exploiting the micro-capillaries as optical resonators: by monitoring the spectral shift of the ratio between the transmitted and reflected optical spectra (T/R) from the capillary, it is possible to extract the wavelength positions of the cavity resonances (maxima of T/R) for fluids with different refractive index. When the refractive index of the sample fluid filling the channel increases, a shift towards longer wavelengths is observed. Then, a spectral phase shift interferometric technique for the detection of the wavelength position of the resonances is proposed. When the capillary is inserted in an interferometric setup, it is possible to distinguish fluids by knowing the dependence of the wavelength positions of the steep jumps in the cosine signal on the refractive index of the filling fluid. Finally, the potentiality of micro-capillaries is investigated for specific sensing, exploiting absorption spectroscopy. All the proposed optical readout approaches are remote, contactless and non-invasive. In addition, the glass-micro-capillaries are very suitable for analytical detection of fluids: they are low-cost devices, available in several formats. Thanks to their micrometric size, they can be incorporated in micro-fluidic circuits. Borosilicate glass is a bio-compatible material, allowing the use of the micro-fluidic platforms in a wide range of applications for label-free optical sensing.

Examples of piezoelectric MEMS (micro-electromechanical systems) developed to work as sensors, actuators and energy harvesting devices are presented. Specifically, a distance-independent contactlessly-interrogated piezoelectric microresonator has been developed to operate as a microbalance. Acoustic-wave piezoelectric microactuators have been investigated to centrifugate liquid drops in acoustofluidics applications and to operate as tunable sound transducers. A piezoelectric MEMS energy harvester which combines the multi-converter and nonlinear approaches has been proposed.

The present work is part of the research activity of the S.A.L.V.O. Project, which envisages the realisation of a portable multisensory node to monitor possible dangerous conditions for workers, by evaluating their exposure to various substances, including atmospheric particulate matter. Here we discuss the possibility of using piezoelectric membranes as self-cleaning atmospheric particulate sensors. PM10-like particulate matter is initially deposited on the membranes, and the frequency shift is evaluated by correlating it to the particulate-covered membrane surface. Finally, the membrane's self-cleaning ability was assessed by subjecting it to appropriate vibration cycles. The results are extremely encouraging and pave the way for the use of piezoelectric membranes as self-cleaning particulate sensors.

In this paper we present the scheme of an optical phase shifter based on a SU-8 slot waveguide with a liquid crystal upper cladding. It has been obtained after an evaluation of the fabrication process flow and the numerical optimization/modeling of waveguides. We studied numerically the achievable phase shift through a combination of 2D Finite Element Method and index ellipsoid diagram. We also show that a slot configuration of the waveguides allows to sustain both quasi-TE and quasi-TM modes, while ensuring more interaction between the guided signals and the cladding. The choice of the materials and fabrication processes was operated by selecting established methods and procedures, and gauging the compatibilities. Given the high phase shifting efficiency and the accessibility of the fabrication processes, this component can be a key element for the development of compact and inexpensive devices which are suitable for many applications in computation, communication and sensing.

The necessity to improve safety on work places, is an impressive driver for advances in the field of Personal Protective Equipment (PPE). Such devices are fundamental to avoid the worker getting hurt during hazardous operations in a work environment. This work presents a prototype of a wearable smart PPE (also called sensor node) equipped with chemical and physical sensors. In particular the sensor node includes particulate, VOC, O2, CO2, CO, sensors and offers the possibility to transmit over LORA network a report to enable an alarm protocol. With the aid of such a device the worker will result always connected to a sentinel network that will continuously monitor him/her in order to guarantee his/her safety. The node has enough computational power so as to implement a Real Time Locating System and Artificial Intelligence algorithms that can interpret some poses or gestures of the worker, correlate them with the location and, in case, recognize and classify them as dangerous. The whole architecture of the system will be presented together with some details on the hardware and software architecture.

We designed, developed and validated a bone conduction-based hand pose sensing wireless and wearable system, capable of distinguishing different hand gestures and enabling the evaluation of the pose angles of the fingers. The system can be used as a valuable alternative to sensory gloves, image processing or electromyographic signal analysis. BCHS has the advantage of significantly reducing the size of the recognition system, not requiring a confined environment as with camera systems, having no blind spots, and being minimally invasive to the user. The test results demonstrated the feasibility of the proposed measurement techniques and encourage further activities for the development of a complete system by embedding the post-processing tasks into the wearable device.

Structural Health Monitoring (SHM) is the technique that allows to understand the health state of a structure. Its application is more and more widespread in the last decades, especially thanks to introduction of the Structural Damage Indicator Evaluation. In case of critical event, or simply for the passage of time, this evaluation allows to understand if a structure has a complete loss of functionality, or, more probably, if it is simply no longer in optimal condition. In the latter case, it will be possible to calibrate the most adequate and targeted interventions. In this work an application that allows to observe the structure functionality over time and to find possible damages is presented. In this case, the reference structure is a steel bar. Its monitoring is made possible using a microcontroller and two digital triaxial accelerometers. The data returned are then suitably processed, so it is possible to determine the identification of the damage indicator in the event that the structure was perturbed.

In this paper we show the design capability of realizing a signal source with the SG13G2 technology process of IHP foundry. It is a 130 nm SiGe BICMOS process and the oscillators that have been designed and fabricated are devoted for THz applications, in particular for the realization of a THz Camera for imaging applications. Different circuitry solutions have been addressed and exhaustive EM analyses have been carried out for the achievement of the designs. Among the solution we have proposed it is worth noting a signal source at 186 GHz, a 370 GHz solution and one operating beyond of the maximum frequency of the transistors, at 580 GHz. Measurements realized as well as chips fabrication by IH Foundry have confirmed the reliability of the designs and the capability to be used in practical applications.

Mood detection and vital signs monitoring based on commonly used contact or contactless devices can play an important role in psychological health monitoring and human-computer interaction. Existing methods cannot rely on the common smart bracelets or watches to monitor emotions in daily life. Thus, in this paper a novel framework for mood detection that combines vital signs and facial expression recognition using contactless sensors is proposed. Specifically, a heart rate (HR) estimation algorithm and a facial expression recognition (FER) module using a low cost and commercial camera are combined to evaluate the end user's mood. The proposed system can detect faces “in the wild” independently from the selected vision sensor and from face orientation, consequently increasing its usability. We are currently testing the overall system first in a controlled environment and then in a real environment to achieve our final goal. The findings of the preliminary experiments show promising results for HR and facial expression monitoring with a low average error expressed in terms of Root Mean Square Error for HR estimation and high accuracy regarding facial expression recognition.

Smartwatches for fitness tracking are more and more popular, cheap and precise in Heart Rate measurement. In this device, the measure of the cardiac rhythm is based on the usage of such optical sensors sensitive to the capillary blood flow. About the heart rate assessment, the mentioned optical method is a robust replacement of the classic Electrocardiography sampled in wearable devices, as it is more immune to motion artifacts. We proposed an innovative Wearable Optical Silicon Sensor for making robust PPG Measurements. The experimental results showed in this contribution, confirmed the effectiveness of the proposed Wearable Optical devices.

In recent years, the interest of the scientific community towards new technologies for sensor fabrication has grown, in particular with regards to the possibility of creating flexible and low-cost sensors, devices and electronic circuits, motivated by the need to increasingly reduce development times and costs manufacturing of sensors and electronic devices.The ever-widening diffusion of applications that use wearable, disposable and low-cost devices has raised also the needing of producing sensors based on sustainable production technologies, possibly recyclable and, anyway, with a low environmental impact, after their useful life.The research team at the SensorLab@DIEEI of the University of Catania, Italy, has been involved, since decades, in research activities on new technologies, such as Inkjet printing and Micromilling for the rapid prototyping of sensors, silicon-based MEMS, flexible polymeric sensors and Biopolymer-based sensors.In this paper, the technologies are introduced and a set of meaningful examples are briefly described. In particular, for the sake of comparison, the selected examples are in all the cases accelerometers.

Ladder networks are typically used for passive filters, and they also represent a good equivalent model for mechanical, chemical and thermal system. These networks could be also used in the study of sensor networks, in order to control their parameters (and their static and dynamic behavior) by interrogating each point of the network; in particular, each node of the network brings the information of each cells of the network. The aim of this work is to provide an automatic model for the monitoring of a sensor network. For this purpose, a network of distributed sensors evaluating the characteristic of the network when the sensors change their features has been studied. This approach was achieved by using Quartz Micro Balances (QMB), a type of sensors generally applied in environmental and medical field.

Localization based services are in the process of being ubiquitous, it is then essential to find a low-cost and low-energy solution for localization of moving targets. Bluetooth-based solutions for indoor localization have become increasingly popular in recent years. In addition to its availability (e.g., BLE is available on most modern smart devices), Bluetooth Low Energy technology is an economical and simple solution to the industry. To the best of our knowledge, none of the existing indoor localization systems use both Angle of Arrival and Received Signal Strength Indication. This paper presents the experimental assessment of a single device localization system that uses Angle of Arrival and Received Signal Strength Indication for localization of moving targets using Bluetooth. The results demonstrate that the developed system is an important step towards a new generation of real-time indoor localization systems that can locate targets with high accuracy (e.g., AoA accuracy: 89.2%), and an improvement concerning the cost of the implementation.

This paper presents a novel approach for achieving a very simple, wideband ultrasonic signals reception stage. It relies on a piezopolymer broadband sensor and a second generation voltage conveyor (VCII) based electronic interface. The former manages to achieve a bandwidth larger than 60 kHz thanks to its novel shape, whereas the electronic interface takes advantage of the inherent capability of VCIIs of manipulating both voltage and current signals to achieve a large bandwidth while maintaining extremely high conversion gains. The proposed system, although very simple, shows a sensitivity level of −100 dB, which matches commercially available references. The presented results are obtained without any filtration stage. VCII has been implemented through a commercially available AD844, with a supply voltage of ±15 V.

A robust, self-consistent, event-triggered incremental 13-bit A/D converter for space spectroscopy (ORION ADC) has been developed and characterized. The main application of the proposed circuit is the detection of X and γ rays in space within the THESEUS exploration mission, whose aim is a deeper investigation in high-energy transient phenomena over the complete universe history. The first fabricated prototype, in CMOS 0.35 µm technology includes the full ADC mixed signal architecture plus all ancillary but fundamental blocks for its successful characterization, including voltage reference and input signal buffers. The circuit is based on a second order sigma-delta modulator architecture which can be reset before each conversion to avoid hysteretic behavior over different samples processing. This requirement is mandatory in spectroscopic applications. Since the converter will be employed in a dual-mode front-to-back-end circuit for X and γ ray detection, it must exhibit maximum flexibility and re-configurability. Several internal analog and digital test points can be interrogated by the characterization setup and a dedicated internal logic can carry out digital decimation and filtering operations, as well as control the ADC state machine and accuracy/conversion time trade-off mode preference. The ORION ADC is one of the key-modules of the core ASIC of the THESEUS mission spectroscopy ORION, thus particular focus has been given to reliability and robustness. Finally, event-based conversion leads to power consumption reduction, while guaranteeing very short latency in conversion time.

In this work a smart sensorial panel with innovative characteristics is presented. It is realized from waste, in particular from the industrial processing of paper and cardboard and embeds a series of wireless and battery-free sensors. The system is able to monitor the environmental conditions of the panel itself in terms of temperature and moisture. In addition, it shows localization capability for safety monitoring in the workspaces thanks to the embedded RFID tag. All communications as well as power supply are possible thanks to a dedicated reader. These characteristics make the panel very easy to be installed and of interest for industry 4.0.

In this paper the authors present a current mode approach for the readout of differential capacitive sensors. The main novelty lies in the use of the relatively new second generation voltage conveyor (VCII) active block to process signals in the current domain and then operate an inherent conversion to a voltage output, so to make the readout operation compatible with a voltage mode system. This approach allows to achieve a high and tunable sensitivity, even at low supply voltages and, thanks to a simple current feedback operation, the insensitiveness to stray capacitances is achieved as well. Waiting for IC fabrication, preliminary measurements have been conducted using commercial components (AD844) to implement the VCII, showing a constant interface sensitivity up to 412 mV/pF and a maximum linearity error of 1.9%FS with the sensor baseline in the picofarad range.

In a smart city environment, the explosive growth in the volume, speed, and variety of data being produced every day requires a continuous increase in the processing speeds of servers and entire network infrastructures, platforms as well as new resource management models. This poses significant challenges for data-intensive and high-performance computing, i.e., how to turn enormous datasets into valuable information and meaningful knowledge efficiently. In this work, the authors propose an approach and describe a methodology and a modular and scalable multi-layered ICT platform called ENEA Smart City Platform (ENEA-SCP) to address the problem of cross-domain interoperability in the context of smart city applications and for offering services to the users (e.g. public administration, citizens, providers).

Wireless sensor networks (WSNs) in recent years have undergone a rapid development reaching great diffusion, due to the growing availability of smart sensors that are small, cheap, and low-power. These sensors are equipped with wireless interfaces to communicate with others, forming a network. The combination of WSNs with commercial sensors gives the opportunity to use these systems in many applications, such as monitoring indoor and outdoor air quality, detecting gas leaks in workplaces, evaluating plant health, and tracking wild animals. In this brief review we examine the most interesting recent contributions that apply WSNs in these new contexts, highlighting the sensing approaches and major trends in communication technologies.