In the past few years, several interesting developments in microstructured solid-state thermal neutron detectors have been pursued. These devices feature high aspect-ratio cavities, filled with neutron converter materials, so as to improve the neutron detection efficiency with respect to coated planar sensors. In the framework of the INFN HYDE (HYbrid Detectors for neutrons) project, we have designed new microstructured sensors aimed at thermal and fast neutron detection. Owing to the different cross section, neutron imaging is complementary to X-ray imaging allowing for a high contrast in soft materials. To this purpose, the possibility to have pixelated neutron detectors compatible with existing read-out chips (e.g., those from the Medipix/Timepix family) is an important goal that was achieved in this thesis. In this thesis the entire workflow will be described in detail, covering the design, simulations, fabrication and characterization of 3D neutron detectors for imaging produced at FBK. As a related topic, new 3D sensors for the "Phase-2" upgrades at High Luminosity LHC have been developed, and some aspects relevant to the device simulation and characterization are also reported in this thesis.

Geiger-Mode avalanche photodiodes (GM-APDs) are diodes designed to operate at a reverse voltage that exceeds the breakdown voltage. Their ability to detect single photons combined with their excellent timing resolution make them ideal for applications in which low amplitude signals need to be detected with sub-ns timing resolution. In the research activity reported in this dissertation two different applications of Geiger-Mode Avalanche Photo Diode arrays have been analysed: a two-tier GM-APD array with in-pixel coincidence for particle tracking and a direct Time-of-Flight range meter with a SiPM-based receiver. The increasing complexity of particle tracking systems at collider experiments demands for high performance detectors with high granularity and position accuracy, low material budget and power consumption. Both Hybrid and monolithic detectors have been proposed as particle trackers. Hybrid detectors have the advantage of allowing an independent customization of sensors and readout electronics, but they exhibit a higher input capacitance that increases readout noise, thus limiting their minimum thickness (100 μm). Monolithic detectors have lower input capacitance, thus a better minimum detectable charge, with a charge time collection of few tens of ns. Thanks to their high gain, particle detectors based on GM-APDs have the potential for combining low material budget, low power consumption and an excellent timing resolution in the range of 100 ps. However, their use as particle tracking detectors has been prevented by their Dark Count Rate, since it is not possible to discriminate a particle-generated event from a dark event. To overcome this issue, the use of GM-APDs in coincidence has been proposed. The activity reported in this dissertation has been conducted in the framework of APiX2 and ASAP projects funded by Istituto Nazionale di Fisica Nucleare (INFN). A two-tier sensor based on avalanche detectors in coincidence has been designed and fabricated in standard 150 nm CMOS technology. A charged particle crossing both GM-APDs integrated in a pixel triggers an avalanche in both devices. The output signal from each detector reaches the coincidence electronics, that allows the device to discriminate the particle detection from dark events. The performance of the proposed detector has been evaluated in a complete electrical and functional characterization campaign. The feasibility to reduce the substrate thickness has been studied in some devices thinned down to 50 μm and 25 μm. The electronics for coincidence detection was also used to directly measure optical crosstalk, a phenomenon that is getting greater importance as stacked optical and image sensors are becoming common. The functional characterization of the APiX prototype was performed with a beta-source and an evaluation of the radiation hardness of the devices was carried out in an irradiation campaign with neutrons at the INFN Laboratori Nazionali di Legnaro (LNL). SiPMs take advantage of the characteristics of GM-APDs such as high sensitivity, high efficiency and very low time jitter, and overcome the problem related to the dead time connecting several sensitive elements in parallel, making them suitable for the simultaneous detection of more than one photon. The evaluation of a SiPM-based direct Time-of-Flight range meter has been performed at two different wavelengths: 405 nm and 810 nm. The set of measurement at 405 nm has been performed using a TCSPC module as acquisition system, while in the 810 nm measurements a low-cost FPGA-based TDC was used. The replacement of the TCSPC module with an FPGA-based TDC represents an important step towards the integration of a low-cost prototype thanks also to the low power consumption of the device. In order to evaluate the feasibility of a SiPM-based range meter in the NIR region, a collaboration with the Circuits and Systems Research Unit of the ITEE Faculty of the University of Oulu was established to set up a system with a GaAs/AlGaAs multiple quantum well laser diode with a spectral emission of 0.808 μm as transmitter and a NIR-HD SiPM with an enhanced efficiency for NIR photons recently developed at FBK as receiver. The evaluation was performed at high repetition rate (MHz range), for the perspective purpose to upgrade the system including a 2-axis scanning mirror to perform real-time 3D imaging.

A novel set up for Positronium Time Of Flight is proposed, using Silicon Photomultipliers (SiPMs) instead of Photomultiplier Tubes. The solution allows us to dramatically increase the compactness of the set up, thus improving the efficiency of 240%. Different configurations of SiPM+scintillators are characterized in order to find the best solution. Also, simulations are provided, together with preliminary tests in the particular application. A compact read-out board for the processing of up to 44 channels has been designed and tested.Further tests, expected in the near future, are needed in order to confirm the simulations and to build the final set up.

The introduction of the Brake By Wire is replacing the traditional mechanical control systems with ECUs and it is raising the need to reproduce feelings of eliminated static mechanical components (i.e. hydraulic fluids, pumps and cylinders). Thanks to electromechanical actuators and human-machine interfaces (i.e. active pedal) it is possible to reproduce such feelings and, therefore, arbitrarily change their features. In this way it will be possible to customize the pedal feelings and the vehicle deceleration needed depending on several factors (i.e. surrounding braking scenario, driver characteristics, race vs day-by-day driving condition). Since braking maneuvers are typically critical and involve the driver, the design and development of brake by wire system must start from the consideration of human factors in order to increase acceptance and braking effectiveness. The objective of this research was to redesign the pedal feelings, making them adaptable to the surrounding. Driver acceptance and braking effectiveness could be highly improved by means of adaptive pedal feelings. The starting points of this research were humans factors in the braking domain. Literature and relevant studies have been taken into consideration to put into evidence human mechanisms and behaviors during braking phases. On such basis, two main results have been found out: braking use cases and pedal feeling curves. With regard to the pedal feelings curves, 4 different pedal curves which describe both force on brake pedal travel and acceleration on brake pedal travel are designed. The pedal feeling depends on several factors like the pedal travel, the pedal idle travel, the effort, responsiveness, deceleration perceived, ease of balance (i.e. ease of modulation), gradual braking and so on. Regarding braking use cases, they are described by vehicle data as speed, acceleration, angles and relevant rates, engine rpm, gas and brake pedal position/speed and so on. These use cases have been clustered in order to meet the 4 pedal curves. The research continued on the implementation of a Matlab/Simulink/Stateflow model for the use case recognition. Basing on the vehicle data, the model is able to find out in which use case the vehicle is (parking, low speed maneuvers, emergency, downhill, and so on). Once it finds out the scenario, the model applies the most appropriate pedal feeling curve (both force feedback and deceleration needed). In the end, the model commands an EC brushless motor which is responsible of the changing of static springs force feedback of the pedal. The scenario recognition model has been validated through vehicle data on real road whereas the pedal feeling and relevant motor behaviors have been validate on bench tests.

Sustainable energy and energy harvesting has become a hot research area due to the shortage of fossil energy resources and burning fossil fuels release greenhouse gases in our environment, which is partaking in gradually increasing of surrounding temperature of our environment. Therefore, the penetration of various types of renewable/ distributed sources, onsite storage devices and DC powered appliances has recently focused attention towards DC power distribution in consumer grids to achieve the target of zero/positive energy buildings and communities. As compared to AC micro grid, many recent studies revealed that DC distribution has many advantages over the convectional AC distribution in term of high efficiency, integration of renewable/ distributed sources and storage locally. The objective of this dissertation is to propose reliable, cost-effective, sustainable, scalable DC consumer grid architecture which can integrate not only renewable/ distributed sources and storage, but also fully compatible with the convectional AC distribution network without any significant change or upgrade. In order to achieve this goal, we proposed the DC Transformer (DCT) enabled consumer grid model. The DC Transformer has been regarded as one of the most emerging technologies and it has many advantages over the convectional low frequency AC transformers such as high power density in small area, voltage regulation, reactive power compensation, fault detection and isolation etc. Apart from advantages, DCT required intelligent control algorithm and additional supervisory circuit makes it complicated and expensive. Therefore, in our proposed model we discussed the pros and cons of typical Solid-State transformer topologies already proposed and explained the topology used in the DCT transformer. Furthermore, in state of the art models, authors used three stages of grid operational modes, which is usually based on different factors such as the status of grid connections, State of charge of Battery storage and output power from locally available sources. However, we introduced four stages excluding buffering stage. All stages are depended upon the practical situations consumer grid may face during normal grid operations such as, DCT Isolation mode, if main grid and local generators are not available then how our proposed model would manage the locally available storage. Main grid interactive mode, we discussed the existing or convectional grid operational condition. In case of no local generator available and the AC main is the only source of power. Self-reliance grid operation, when the renewable energy sources are generating enough energy to fulfil demand side power requirements. Moreover, we explain the safest transition technique from grid connected mode to self-reliance mode without effecting overall grid stability and reliability, called buffer state. Power sharing mode, in this mode we discussed how the locally consumer grid would share surplus energy with adjacent consumer grids without effecting or compromising its own stability. The purpose of proposing critical operational modes and defining the rigid criteria between transitions of each mode is to operate whole grid flawlessly in any real time condition. Moreover, we introduced “Buffer stage†in between the grid connected and self-reliance mode to take into account that renewable sources are stochastic in nature and to avoid any grid stability issue. The operational modes are among key techniques of our proposed architecture and the detail contribution of our proposed model is mentioned in section $1.7.3$. Some practical issues related to the DC micro grid are also examined in detail, such as overall grid control algorithm, power management strategy, demand side management, fault isolation and rectification are highlighted and the solution of these issues also presented with detail simulation results. Furthermore, the state of art DC grid models are proposed for specific type of renewable source(s) such as PV, wind or combination of both. In our proposed architecture, we are not depending on any specific type of renewable and distributed source or storage. We proposed the standard interfaces for possible type of renewable /distributed sources, storage and grid connection. Therefore, by using the standard interface any type of the source and storage can be plug-n-play in PCmRC model. However, the main objectives are to maximize the exploitation of renewable-sources, to decrease reliance on fossil-fuel, to boost the overall efficiency of the grid by reducing the power-conversion losses and full management of end user demand in all possible forms. The simulation platform is designed in MATLAB/Simulink. Several types of case studies and simulation results show the effectiveness of the proposed power distribution and management model.

Terahertz gap corresponding to the frequency band of 0.3-3.0 THz is historically the last unexplored region of the electromagnetic spectrum left to be fully investigated. The major difficulty that has hampered the maturation of technologies operating in this region lies in the fact that much unlike its bordering millimeter and infrared regions, generation and detection of THz radiation is not trivial. Yet, such is the intriguing nature and properties of the terahertz radiations that the interest in this region has not faded. Infact, potential applications of THz based systems have emerged in various fields including biomedical imaging, safety and security, quality control and communication. Over the past decade, a lot of research work has been published with an aim to bridge this gap by both electronics and photonics based systems. While these attempts have succeeded to a certain extent, the available solutions either lack in terms of performance or are mostly bulky and difficult to integrate for portable and commercial purpose. This PhD dissertation focuses on the design and investigation of direct terahertz detectors which could be operated at room temperature and fabricated in standard silicon technologies, thereby making use of several advantages like high level of integration, low cost and small device size that these technologies have to offer. In particular, the emphasis is on developing and characterizing terahertz systems for imaging application by using field effect transistor devices as detectors. This objective is pursued in three parts. The first part (chapter 3) of the dissertation deals with the measurement and characterization challenges of terahertz systems. Unlike guided mode solutions, measurements of terahertz detectors and their systems require free space which presents several challenges due to atmospheric attenuation, spurious reflections and diffractions, beam shaping, and so on. Moreover, background noise is also significant considering that the detected signal is typically in the order of a few microvolts. In this regard, an overview of the most common techniques is given and a measurement methodology involving the use of a reference pyroelectric detector to measure the impinging input power and techniques for the evaluation of the detector under-test effective area is presented. The second part (chapter 4) is related to the investigation of variants of antenna-coupled field effect transistor and schottky barrier diode in standard 180 nm CMOS process as examples of direct detectors. During laboratory characterization, detection of terahertz radiation from schottky diode could not be achieved due to matching issues. Moreover, optimization of schottky diode by modifying its standard cell proved to be challenging as compared to field effect transistor, which can be optimized easily to enhance performance parameters and was therefore finally chosen as the preferred choice. The final part of the thesis (chapters 5 and 6) concerns with the implementation of analog readout interface to perform signal processing of detected terahertz signal. First, a single pixel consisting of on-chip antenna-coupled detector and a switched capacitor based filtering operation is designed and fabricated in 0.15Î1⁄4m process. The pixel is tested by performing both electrical and terahertz characterization, achieving high voltage responsivity value of 470 kV/W and a minimum NEP of 480 pW/sqrt (Hz). The interface architecture is highly repeatable and it can be used with any commercially terahertz source, even if its operation is limited by low modulation frequency. On the basis of the successful measurement results, an 8 x 6 terahertz array for real-time imaging application is fabricated in the same technology by modifying the interface architecture to make it power and area efficient.

This doctorate thesis focuses on the analysis, design and characterization of Radio-Frequency (RF) Micro-Electro-Mechanical System (MEMS) switches for space applications. The work was inspired and supported by the European Space Agency (ESA) Contract No. ITT AO/1-5288/06/NL/GLC ?High Reliability Redundancy Switch?. The main purpose of the project is the design and realization of high-reliability RF MEMS switches for satellite payload redundancy networks. Up to now, the common satellite architecture implements redundancy networks by means of bulky devices. RF MEMS switches allow for extremely miniaturized networks along with outstanding performances in terms of losses, power consumption and linearity, not really achievable with solid state devices. As requirements for such an application, RF MEMS switches have to survive under extremely harsh environmental and operating conditions. In particular the device should handle continuous bias voltage (at least for 10 years), 5 W of RF input power and around 1000 actuation cycles without meaningful electrical and mechanical failure. The thesis proposes novel mechanical solutions to accomplish this task, exploiting active restoring mechanisms able to restore the previous status of switch in case of reversible failure. This work also provides a deep insight on the main reliability aspects of a RF MEMS device such as dielectric charging, contact degradation and power handling.

A methodology for designing Wireless Camera Network nodes featuring long lifetime is presented. Wireless Camera Networks may nd widespread application in the elds of security, animal monitoring, elder care and many others. Unfortunately, their development is currently thwarted by the lack of nodes capable of operating autonomously for a long period of time when powered with a couple of AA batteries. In the proposed approach, the logic elements of a Wireless Camera Network node are clearly identied along with their requirements in terms of processing capabilities and power consumption. For each element, strategies leading to significant energy savings are proposed. In this context, the employment of a custom vision sensor and an ecient architecture are crucial. In order to validate the methodology, a prototype node is presented, mounting a smart sensor and a ash-based FPGA. The node implements a custom algorithm for counting people, a non trivial task requiring a considerable amount of on-board processing. The overall power consumption is limited to less than 5 mW, thus achieving a two orders of magnitude improvement with respect to the state of the art. By powering the system with two batteries providing 2200 mAh at 3.3 V, the expected lifetime of the system exceeds two months even in the worst-case scenario.

In several application fields there is an increasing need for a diffused on-field control of parameters able to diagnosis potential risks or problems in advance or in early stages in order to reduce their impact. The timely recognition of specific parameters is often the key for a tighter control on production processes, for instance in food industry, or in the development of dangerous events such as pollution or the onset of diseases in humans. Diffused monitoring can be hardly performed with traditional instrumentation in specialised laboratories, due to the time required for sample collection and analysis. In all applications, one of the key-points for a successful solution of the problem is the availability of detectors with high-sensitivity and selectivity to the chemical or biochemical parameters of interest. Moreover, an increased diffused on-field control of parameters can be only achieved by replacing the traditional costly laboratory instrumentations with a larger number of low cost devices. In order to compete with well-known and established solution, one of main feature of new systems is the capability to perform specific tests on the field with fast response times; in this perspective, a fast measurement of reduced number of parameters is to be preferred to a straightforward “clone†of laboratory instrumentation. Moreover, the detector must also provide robustness and reliability for real-world applications, with low costs and easiness of use. In this paradigm, MEMS technologies are emerging as realisation of miniaturised and portable instrumentation for agro-food, biomedical and material science applications with high sensitivity and low cost. In fact, MEMS technologies can allow a reduction of the manufacturing cost of detectors, by taking advantage of the parallel manufacturing of large number of devices at the same time; furthermore, MEMS devices can be potentially expanded to systems with high level of measurement parallelism. Device costs are also a key issues when devices must be for “single use†, which is a must in application where cross-contamination between different measurement is a major cause of system failure and may cause severe consequences, such as in biomedical application. Among different options, cantilever micro-mechanical structures are one of the most promising technical solution for the realisation of MEMS detectors with high sensitivity. This thesis deals with the development of cantilever-based sensor arrays for chemical and biological sensing and material characterisation. In addiction to favourable sensing properties of single devices, an array configuration can be easily implemented with MEMS technologies, allowing the detection of multiple species at the same time, as well as the implementation of reference sensors to reject both physical and chemical interfering signals. In order to provide the capability to operate in the field, solution providing simple system integration and high robustness of readout have been preferred, even at the price of a lower sensitivity with respect to other possibilities requiring more complex setups. In particular, piezoresistive readout has been considered as the best trade-off between sensitivity and system complexity, due to the easy implementation of readout systems for resistive sensors and to their high potential for integration with standard CMOS technologies. The choice has been performed after an analysis of mechanical and sensing properties of microcantilever, also depending of technological options for their realisation. As case-studies for the development of cantilever devices, different approaches have been selected for gas sensing applications, DNA hybridisation sensing and material characterisation, based on two different technologies developed at the BioMEMS research unit of FBK (Fondazione Bruno Kessler - Center for Materials and Microsystems, Trento). The first process, based on wet-etching bulk micromachining techniques, has provided 10 µm-thick silicon microcantilevers while the second technology, based on Silicon-On-Insulator (SOI) wafer, has provided a reduction of device thickness, thus resulting in an increase of sensitivity. Performances of devices has been investigated by analytical and numerical modelling of both structures and readout elements, in order to optimise both fabrication technology and design. In particular, optimal implant parameters for the realisation of piezoresistors have been evaluated with process simulation with Athena Silvaco simulation software, while ANSYS has been used to analyse the best design for devices and the effect of some technology-related issues, such as the effect of underetch during the release of the beams or residual stresses. Static and modal analysis of cantilever bending in different conditions have been performed, in order to evaluate the mechanical performances of the device, and later results have been compared with the experimental characterisation. With regard to gas sensing applications, the development has been oriented to resonant sensors, where the adsorption of analytes on a adsorbent layer deposited on the cantilever leads to shift of resonance frequency of the structure, thus providing a gravimetric detection of analytes. The detection of amines, as markers of fish spoilage during transport, has been selected as a case-study for the analysis of these sensors. The sensitivity of devices has been measured, with results compatible with the models. Cantilever structures are also suitable for bioaffinity-based applications or genomic tests, such as the detection of specific Single Nucleotide Polymorphisms (SNPs) that can be used to analyse the predisposition of individuals to genetic-based diseases. In this case, measurements are usually performed in liquid phase, where viscous damping of structures results in a severe reduction of resonance quality factor, which is a key-parameter for the device detection limit. Then, cantilever working in “bending mode†are usually preferred for these applications. In this thesis, the design and technologies have been optimised for this approach, which has different requirements with respect to resonant detectors. In fact, the interaction of target analytes with properly functionalised surfaces results in a bending of the cantilever device, which is usually explained by a number of mechanism ranging from electrostatic and steric interaction of molecules to energy-based considerations. In the case of DNA hybridisation detection, the complexity of the molecule interactions and solid-liquid interfaces leads to a number of different phenomena concurring in the overall response. Main parameters involved in the cantilever bending during DNA hybridisation has been studied on the basis of physical explanations available in the literature, in order to identify the key issues for an efficient detection. Microcantilever devices can play a role also in thin film technologies, where residual stresses and material properties in general need to be accurately measured. Since cantilever sensors are highly sensitive to stress, their use is straightforward for this application. Moreover, apart from their sensitivity, they also have other advantages on other methods for stress measurements, such as the possibility to perform on-line measurements during the film deposition in an array configuration, which can be useful for combinatorial approaches for the development of thin film materials libraries. In collaboration with the Plasma Advanced Materials (PAM) group of the Bruno Kessler Foundation, the properties of TiO2 films deposited by sputtering has been measured as a case study for these applications. In addiction to residual stress, a method for measuring the Young’s modulus of the deposited films has been developed, based on the measurement by means of a stylus profilometer of beam stiffness increase due to TiO2 film. The optimal data analysis procedure has been evaluated in order to increase the efficiency of the measurement. In conclusion, this work has provided the development of MEMS-based microcantilever devices for a range of different applications by evaluating the technological solutions for their realisation, the optimisation of design and testing of realised devices. The results validate the use of this class of devices in applications where high sensitivity detectors are required for portable analysis systems.

Time synchronization is of primary importance for the operation of wireless sensor networks (WSN): time measurements, coordinated actions and event ordering require common time on WSN nodes. Due to intrinsic energy limitations of wireless networks there is a need for new energy-efficient time synchronization solutions, different from the ones that have been developed for wired networks. In this work we investigated the trade-offs between time synchronization accuracy and energy saving in WSN. On the basis of that study we developed a power-efficient adaptive time synchronization strategy, that achieves a target synchronization accuracy at the expense of a negligible overhead. Also, we studied the energy benefits of periodic time synchronization in WSN employing synchronous wakeup schemes, and developed an algorithm that finds the optimal synchronization period to save energy. The proposed research improves state-of-the-art by exploring new ways to save energy while assuring high flexibility and reliable operation of WSN.