Rozprawy doktorskie na temat „Development of Sensors”

This dissertation focuses on the development, characterization, and analysis of luminescent materials and coatings for sensing applications, including CO2, heavy metals, and silver. Chapter 2 involves the use of a gold(I) pyrazolate trimer that is able to detect silver ions with an AgNP medium. Detection of silver is vital, because there is an influx of silver into our environment caused by the increased use of AgNP. Therefore, having a sensor that is able to differentiate between and detect only Ag ions is an important first step to solving the toxicity mystery of AgNPs. Chapter 3 focuses on the development of sensor coatings containing a Eu(III) based luminescent system for sensing dissolved CO2 without the aid of an absorption-based dye. It is well-known that monitoring CO2 levels in our environment is important since even at low concentrations it can cause adverse health effects to the human body. This work demonstrates a pH-sensitive Eu complex being used directly as a CO2 sensor without the aid of any other absorption-based dye. Chapter 4 explores the idea of developing a heavy metal sensor for lead and its ability to detect lead in wide concentration range upon changing the pH of the medium and the polymer matrix. Different heavy metals have toxicity at different concentrations, therefore, being able to change the dynamic range of the sensor is advantageous. This research is the first step towards developing a luminescent Pb sensor with a tunable dynamic range.

Lanthanide based probes and sensors have been widely utilised over the past few decades, particularly in the study of biological processes. The favourable photoluminescent properties of the lanthanide ions and the use of functionalised macrocyclic ligands that permit tuneable excitation means there is now a plethora of examples, across the scientific literature. An azaxanthone-based chromophore has been incorporated into a cyclen ligand, and the ability of this complex to bind to proteins has been studied further, examining the possibility of personalised medicine. The complex competes with selectively chosen pharmaceutical compound in binding to the acute phase serum protein α1-AGP. This complex is one of the first examples which uses CPL to monitor a binding event. The same chromophore, as well as the azathioxanthone analogue, have been utilised further in cyclen based complexes, with the aim of binding the controversial herbicide, glyphosate. Selectivity for glyphosate against other potential competitors has been studied, testing the ability of a series of structurally related complexes to operate in a variety of media. The final chapter looks at a new family of compounds, which bear an extended chromophore and a tripicolylamine based arm. Again, these were tested for their ability to bind glyphosate selectively, in a range of media. Time-gated methodology was used to allow any unwanted organic auto-fluorescence to be removed, particularly in samples which may contain a lot of biological compounds. Following these studies, one complex was selected, testing whether the complex can be used to calculate the concentration of glyphosate in extract from spiked wheat and oat grains. This complex was able to be used over the range 0.5 to 60 micromolar of glyphosate with a limit of around 4 micromolar.

The purpose of this research is to develop MEMS based acoustic emission sensors for structural health monitoring. Acoustic emission (AE) is a well-established nondestructive testing technique that is typically used to monitor for fatigue cracks in structures, leaks in pressurized systems, damages in composite materials or impacts. This technology can offer a precise evaluation of structural conditions and allow identification of imminent failures or minor failures that can be addressed by planned maintenances routines. AE causes a burst of ultrasonic energy that is measured as high frequency surface vibrations (30 kHz to 1 MHz) generated by transient elastic waves that are typically emitted from growing cracks at the interior of the structure. The AE sensor marketplace is currently dominated by bulky and expensive piezoelectric transducers that are wired to massive multichannel data acquisition systems. These systems are complex to operate with the need of signal conditioning units and near proximity pre-amplifiers for each sensor that demands a fairly complicated wiring requirements. Furthermore, due to the high prices of conventional AE sensors and associated instrumentation, and the current requirements in sensor volumes for smart transportation infrastructure, it is undeniable that new AE technology is required for affordable structural health monitoring. The new AE technology must deliver comparable performance at one or two orders of magnitude lower cost, size and weight. MEMS acoustic emission (AE) sensors technology has the potential to resolve several of these traditional sensor’s shortcomings with the advantage of possible integration of on-chip preamplifier while allowing substantially cost reduction due to the batch processing nature of MEMS technology. This study will focus on filling some of the major existing gaps between current developments in MEMS acoustic emission sensors and commercial piezoelectric sensors, such as sensor size, signal-to-noise ratio (SNR), cost and the possibility to conform to sharply curved surfaces. Basically, it is proposed to develop a new class of micro-machined AE sensors or sensor arrays through strategic design of capacitive and piezoelectric MEMS sensors, which will focus on optimizing the following performance aspects: Creating geometric designs to manipulate the sensor resonant frequency and to optimize Q factor under atmospheric pressure and ambient environment. Developing a strategic selection of materials according to its acoustic impedance as insulator, structure and backing material. Developing strategies to improve the signal to noise ratio SNR with and without integrated amplification/signal processing. Performing a comparison between MEMS and commercial piezoelectric sensors.

La rapida diffusione e la grande popolaritá di laptops, smartphones,PDAs, dispositivi GPS e altri apparecchi elettronici nell'era post-PC, hanno alimentato la tendenza di produrre apparecchi elettronici sempre piú portatili, versatili e a buon mercato, con capacitá di calcolo sempre piú elevate. I continui progressi tecnologici hanno condotto ad un'abbondante disponibilitá di microprocessori e microcontrollori sempre piú piccoli ed economici, equipaggiati con sensori sempre piú avanzati, storage e dotati di connessione wireless. In quest' ottica si colloca l'emergere di una nuova tipologia di reti di telecomunicazioni: le Wireless Sensor Networks (WSNs), le quali rappresentano pienamente l'ultima tendenza della famosa legge di Moore nei confronti della miniaturizzazione e dell'ubiquitá dei dispositivi elettronici. L'integrazione di capacitá di calcolo, memorizzazione e comunicazione in dispositivi di dimensioni ridotte e a basso costo ha portato alla de finizione delle WSNs. Le reti di sensori sono state pensate come possibili strumenti per l'activity recognition in campo biomedico, i risultati di tale applicazione mostrano come questa essa sia molto e fficace nel monitoraggio della azioni di pazienti. Viene inoltre presentata un applicazione realizzata attraverso una WSN. Si tratta di un un applicazione per HRV (Heart Rate Variability). L'HRV é basata sull'analisi tempo-frequenza degli intervalli R-peak raccolti da un segnale ECG. Tale studio propone un toolkit realizzato attraverso una rete di sensori wireless per l'analisi temporale dell'HRV, chiamata SPINE-HRV (Signal Processing In Node Environment SPINE). SPINE-HRV é composto da un sistema indossabile per il monitoring dell'attivitá cardiaca in grado di raccogliere continuamente gli R-peak e un applicazione in grado di processare cosí i dati raccolti. L'analisi fatta attaverso lo SPINEHRV toolkit fornisce sette parametri ben noti in letteratura medica in grado di aiutare i cardiologi nella diagnosi relativa a diverse problematiche. Inoltre tale toolkit fornisce uno strumento automatico per rilevazione di stati di stress acuti rilevabili durante tutte le attivitá svolte quotidianamente. Nella seconda parte verrá presentata una panoramica sui media gateway in particolare sui transcoder video per gli standard di codi ca video H.263+ e H.264. L'eterogeneitá sempre piú diffusa dei dispositivi presenti all'interno della rete Internet, rende necessaria lo sviluppo di dispositivi hardware o software in grado da permettere una a dabile intercomunicazione tra tali diversi dispositivi. In particolare si mostrerá come é possibile riutilizzare i modi Intra estratti durante il processo di decodi fica per aumentare l'efficienza della codifi ca in altro standard di codi ca video. Sono stati sviluppati due algoritmi in grado di selezionare attraverso una decisore a soglia, utilizzato sia per i modi 4x4 che 16x16. Verranno presentati le prestazioni in termini di PSNR e tempi di elaborazione confrontati con quelle relative l'approccio full transcoding. Tali risultati mostrano come siano stati ottenuti signi ficativi riduzioni dei tempi computazionali pur mantenendo un livello di PSNR confrontabile con quello relativo al processo di full transcoding.
With the wide diffusion and popularity of laptops, cell-phones, Personal Digital Assistants (PDAs), GPS devices and other intelligent electronic in the post-PC era, computing devices have become more portable, mobile and cheap. Nowadays the electronic in uences the daily life of each man and many tasks hard to do in the past now have become reality and easy to perform thanks to the signi cant advances in technology. From this viewpoint the emergence of wireless sensor networks (WSNs) is essentially the latest trend of Moore's Law toward the miniaturization and ubiquity of computing devices. Wireless sensor networks are used in order to perform activity recognition in heath care eld, the results of this application show how that it is effective in patient's actions monitoring. Moreover an application regarding Heart Rate Variability (HRV)will be presented. This work is based on the analysis of the Rpeak to R-peak intervals (RR-intervals) of the ECG signal in the time and/or frequency domains. Doctors and psychologists are increasingly recognizing the importance of HRV; in fact, a number of studies have demonstrated that patients with anxiety, phobias and posttraumatic stress disorder consistently show lower HRV,even when not exposed to a trauma related prompt. Importantly,this relationship existed independently of age, gender, trait anxiety, cardio-respiratory tness, heart rate, blood pressure and respiration rate. The SPINE-HRV is composed of a wearable heart activity monitoring system to continuously acquire the RR-intervals, and a processing application developed using the SPINE framework. The RR-intervals are processed using the SPINE framework at the base station side through a time-domain analysis of HRV. The analysis provides seven common parameters known in medical literature to help cardiologists in the diagnosis related to several heart diseases. In particular, SPINE-HRV is applied for stress detection of people during activities in their everyday life. Experimentations carried out by monitoring subjects in speci c activities have shown the effectiveness of SPINE-HRV in detecting stress. Currently few research prototypes based on BSNs exist that allow for HRV analysis. However SPINE-HRV represents the fi rst prototype using a wireless chest belt so making the system more comfortable than systems using wired electrodes or handheld devices. Furthermore, because the chest belt is a commercial product for sport and tness activities, it has been designed to be robust against body movements. SPINE-HRV is currently applied to stress detection that is computed through an effective threshold based algorithm. The experimentation of such an application has been carried out on different subjects performing different activities of the everyday life: walking, working at the PC, watching TV, sleeping, and driving. The obtained result are interesting as they show that SPINE-HRV is able to detect stress by performing only a time-domain analysis of HRV with respect to more complex computational methods based on the frequency-domain analysis. Thus, SPINE-HRV can be actually used to detect stress of human beings in real-time. Currently, we are focusing our research efforts in improving the stress analysis algorithm by introducing frequency domain features as well as comparing the obtained results to the clinical blood test for the stress hormone, which has been identi ed by the medical community as the quantitative measurement of the emotional stress level. In the second part of this thesis will be described two smart video transcoder processes in order to develop a media gateway. The aim of this network device is to bring about a conversion of the input bitstream into another one characterized by a different video codec. The codecs involved in the transcoding algorithm are the H.263+ (Annex I) and the H.264 baseline pro le. The scope of this study focuses on the possibility of reusing the Intra modes extracted from the input bitstream. Regarding H.263+ to H.264 transcoding, two different thresholds are evaluated for 4x4 blocks and 16x16 macroblocks: all the incoming modes that lead to costs over threshold are rejected and a re-estimation is performed. Otherwise, the incoming Intra mode is directly passed to the H.264 encoder. On the other hand, all the H.264 Intra modes are mapped into the H.263+ Intra modes and passed to the H.263+ encoder skipping the Intra prediction stage. Performance in terms of PSNR and elaboration time of our algorithms are compared to that of the full transcoding approach. A high correlation with PSNR scores is obtained and a significant reduction of computational burden for both transcoding processes is also achieved. The two video transcoder architectures are proposed in order to perform the H.263+ to H.264 conversion and vice versa. Referring to the rst transcoder, two adaptive thresholds are implemented. Both thresholds, used for 4x4 Intra block mode decision and 16x16 Intra block mode decision, vary according to the overall macroblock cost in order to consider the level of detail of the under-study macroblock. This solution is an innovation relating to the approaches proposed in literature based on the usage of a single xed threshold. We can assert that these algorithms represent a basis for the implementation of a low complexity fast transcoder for real-time applications thanks to the low complexity of the modi cation introduced, and also for the reduced computational burden of the entire trancoding process. In fact, we demonstrate a decrease of about 32% in the overall elaboration procedure using an arbitrary QP. The proposed platform also shows high reliability in terms of perceived quality. This is confi rmed by PSNR evaluations for fast transcoding output. PSNR differences are limited to 0.1 dB for all sequences used in the tests. So, the quality of the full transcoding output is very close to the one obtained by the fast transcoding technique. In addition, the overall increase in the bitrate is less than 12%. The H.264 to H.263+ transcoder uses a mapping between the incoming H.264 modes that is rather different to the one proposed in literature. The obtained results, using several standard sequences and QP, show that the overall quality is the same for the output bitstream obtained by the full transcoder and the proposed smart transcoder algorithm, and the bitrate increase is limited to 9% in the worst case. With this mapping it is possible to cancel the computational burden of the Intra mode prediction process. All these considerations allow us to assert that the proposed algorithm can be used in real-time transcoding architectures. Similar analysis concerning Inter frame pictures are actually under study by the authors in order to reduce the complexity of motion estimation procedure in transcoding architectures.

Els sensors nanomecànics han estat reportats històricament com una eina atractiva per a la biodetecció degut a la seva alta sensibilitat, alt rendiment i alta integració. La majoria dels sensors nanomecànics s’han fabricat amb tecnologia basada en silici, podent integrar milers de sensors en un sol xip. No obstant això, el desenvolupament d’aquest tipus de sistemes implica no només la fabricació de matrius de transductors mecànics, que actualment és un procés molt establert i de baix cost, sinó també l’implementació d’un sistema de lectura per llegir independentment la resposta de cada transductor. Aquesta tesi doctoral es va centrar en el desenvolupament d’un nou enfocament per a la detecció de la resposta mecànica d’una matriu de sensors mecànics mitjançant l’ús d’instrumentació senzilla. Aquest enfocament consisteix en el desenvolupament de sensors mecànics (microcantilevers i micromembranes) amb resposta mecanocròmica, és a dir, sensors mecànics que canvien el seu color intrínsecament davant l’estimulació mecànica. El desenvolupament de sensors basats en MEMS amb resposta mecanocrómica és el resultat d’una combinació efectiva de la coloració estructural produïda per xarxes de difracció o cristalls fotònics, amb el rendiment dels transductors mecànics. Els sensors mecànics amb una nanoestructura periòdica disposada en una cara del sensor, es van fabricar i caracteritzar. El color mostrat pels sensors canvia intrínsecament per l’acció d’un estímul mecànic extern (càrrega de pressió o tensió superficial) quan el transductor es deforma, i el canvi de color es recollit per un LED i una càmera RGB de baix cost. Per dur a terme aquest desenvolupament, es realitza un estudi teòric de la física de coloració estructural i de models matemàtics que descriuen el principi de funcionament del dispositiu mecanocròmic. Amb aquests elements bàsics, els materials mecanocròmics basats en dos tipus d’estructures fotòniques, xarxes de difracció 1D i acoblaments col·loïdals, són fabricats i caracteritzats per espectrometria UV-Visible, identificant els principals contribuents del canvi de color (variacions en el període de la nanoestructura i canvis en l’angle d’il·luminació de punt de vista). Aquests materials a continuació són integrats a matrius de sensors mecànics colorimètrics per ser caracteritzats per mitjà de tensió biaxial. Es fabrica, caracteritza i avalua una matriu de sensors de pressió colorimètrics basats en membranes flexibles nanoestructurades i suspeses, lliures de marcatges i d’alimentació d’energia orientat a les aplicacions optofluídiques multiplexades. La plataforma mostra una sensibilitat de 0.17 kPa-1 en la detecció de pressions pneumàtiques baixes o de fluids (en un rang entre -1 i 1 kPa) i es demostra l’idoneïtat del mètode de detecció colorimètric mesurant el canvi de color de les membranes que mostren una sensibilitat de 117 nm \/ kPa. Finalment, es realitza un estudi teòric d’un sensor nanomecrònic colorimètric de tensió superficial basat en cantilevers i es demostra la seva utilitat a la detecció de canvis conformacionals moleculars fotoinduïts. D’aquesta manera, el mètode de detecció és capaç de detectar canvis de 1° en l’escala de to (HSV), o 0.75 nm de longitud d’ona en el rang visible (400 nm a 650 nm). El desenvolupament de sensors basats en MEMS amb resposta mecanocròmica es presenta com una eina útil que compleix amb els requisits per al desenvolupament d’un dispositiu de punt d’atenció.
Los sensores nanomecánicos han sido reportados históricamente como una herramienta atractiva para la biodetección debido a su alta sensibilidad, alto rendimiento y alta integración. La mayoría de los sensores nanomecánicos se han fabricado con tecnología basada en silicio, pudiendo integrar miles de sensores en un solo chip. Sin embargo, el desarrollo de este tipo de sistemas implica no solo la fabricación de matrices de transductores mecánicos, que actualmente es un proceso muy establecido y de bajo costo, sino también la implementación de un sistema de lectura para leer independientemente la respuesta de cada transductor. Esta tesis doctoral se centró en el desarrollo de un nuevo enfoque para la detección de la respuesta mecánica de una matriz de sensores mecánicos mediante el uso de instrumentación sencilla. Este enfoque consiste en el desarrollo de sensores mecánicos (microcantilevers y micromembranas) con respuesta mecanocrómica, es decir, sensores mecánicos que cambian su color intrínsecamente ante estimulación mecánica. El desarrollo de sensores basados en MEMS con respuesta mecanocrómica es el resultado de una combinación efectiva de la coloración estructural producida por redes de difracción o cristales fotónicos, con el rendimiento de los transductores mecánicos. Los sensores mecánicos con una nanoestructura periódica dispuesta en una cara del sensor, son fabricados y caracterizados. El color mostrado por los sensores cambia intrínsecamente por la acción de un estímulo mecánico externo (carga de presión o tensión superficial) cuando el transductor se deforma, siendo el cambio de color recogido por el uso de un LED y una cámara RGB de bajo costo. Para llevar a cabo este desarrollo, se realiza un estudio teórico de la física de coloración estructural y de modelos matemáticos que describen el principio de funcionamiento del dispositivo mecanocrómico. Con estos elementos básicos, los materiales mecanocrómicos basados en dos tipos de estructuras fotónicas, redes de difracción 1D y ensamblajes coloidales, son fabricados y caracterizados por espectrometría UV-Visible, identificando los principales contribuyentes del cambio de color (variaciones en el período de la nanoestructura y cambios en el ángulo de iluminación de punto de vista). Estos materiales a continuación son integrados a matrices de sensores mecánicos colorimétricos para ser caracterizados por medio de tensión biaxial. Se fabrica, caracteriza y evalúa una matriz de sensores de presión colorimétricos basados en membranas flexibles nanoestructuradas y suspendidas, libres de marcajes y de alimentación de energía orientado a las aplicaciones optofluídicas multiplexadas. La plataforma muestra una sensibilidad de 0.17 kPa-1 en la detección de presiones neumáticas bajas o de fluidos (en un rango entre -1 y 1 kPa) y se demuestra la idoneidad del método de detección colorimétrico midiendo el cambio de color de las membranas que muestran una sensibilidad de 117 nmkPa-1. Finalmente, se realiza un estudio teórico de un sensor nanomecánico colorimétrico de tensión superficial basado en cantilevers y se demuestra su desempeño en la detección de cambios conformacionales moleculares fotoinducidos. De esta manera, el método de detección es capaz de detectar cambios de 1o en la escala de tono (HSV), o 0.75 nm de longitud de onda en el rango visible (400 nm a 650 nm). El desarrollo de sensores basados en MEMS con respuesta mecanocrómica se presenta como una herramienta útil que cumple con los requisitos para el desarrollo de un dispositivo de punto de atención.
Nanomechanical sensors have been historically reported as an attractive tool for biodetecction due to its high sensitivity, high throughput, and high integration. Most of nanomechanical sensors have been fabricated using silicon based technology being able to integrate thousands of sensors in a single chip. However, the development of this kind of systems involves not only the fabrication of arrays of mechanical transducers, which is currently a well-established and low-cost process, but also the implementation of a read-out system to independently read each transducer response. This Doctoral Thesis focused on the development of a new approach for the detection of the mechanical response of an array of mechanical sensors by using simple instrumentation. This approach consists in the development of mechanical sensors (microcantilevers and micromembranes) with mechanochromic response, i.e. mechanical sensors with an intrinsic tunable colour under mechanical stimulation. The development of sensors based in MEMS with mechanochromic response is a result of an effective combination of the structural coloration produce by diffraction gratings or photonic crystals, with the performance of mechanical transducers. Mechanical sensors with a periodical nanostructuration disposed on one face of the sensor, are fabricated and characterized. The colour displayed by the sensors change intrinsically by the action of an external mechanical stimulus (pressure load or surface stress) when the transducer deflects, being the colour change collected by the use of a LED and a low cost RGB camera. In order to carry out this development, a theoretical study of the physics of structural coloration and the mathematical models that describe the working principle of the mechanochromic device is performed. With these basics, the mechanochromic materials based on two types of photonic structures, linear 1D gratings and colloidal assemblies, are fabricated and characterized by UV-Visible spectrometry, finding the main contributors of colour change (variations in the nanostructure period and changes in the illumination and point of view angle). These materials are then integrated into arrays of coloured mechanical sensors and characterised under bi-axial strain. A label-free and power-free array of colour tunable pressure sensors based on flexible nanostructured suspended membranes is fabricated, characterized and evaluated for multiplexed optofluidics applications. The platform shows a sensitivity of 0.17 kPa^(-1) for the detection of low pneumatic or fluid pressures (in a range between -1 and 1 kPa) and the suitability of colorimetric detection method is demonstrated by measuring the membrane colour change with a sensitivity of 117 nm\/kPa. Finally, a theoretical study of a surface stress colorimetric nanomechanical sensor based in cantilevers is performed and demonstrated its performance for the detection of photo-induced molecular conformational changes. In this case, the detection method is able to detect changes of 1^o in the hue scale (HSV) or 0.75 nm for the visible band in wavelengths (400 nm to 650 nm). The development of sensors based in MEMS with mechanochromic response is presented as a useful tool that fulfils the requirements for the development of a point-of-care device, such as: high sensitivity, low-cost, high throughput, label-free, out of the shelf, disposable, multidetection, and also that does not require a sophisticated detection system.

Due to the biological importance of heme and its implication in various disease states, uncovering how it is transported throughout the cell is of vital importance. Some of the strongest in vivo tools present in the literature are FRET-based sensors using a number of chromophores that are optimized and expanded from GFP. In order to elucidate the movement of heme throughout the cell, GFP FRET -based heme sensors were designed, expressed, and purified to be further characterized in vitro. This series of heme sensors were expressed in Saccharomyces cerevisiae to monitor the in vivo movement of heme. Different growth conditions were explored to monitor the effect of these changes to cytosolic heme availability. These heme sensors are now poised to address the movement of heme from the mitochondria to other targets in the cell under a variety of conditions. This will provide insight into heme trafficking pathways, as well as the role heme plays in neurodegenerative diseases and aging

This thesis describes an investigation into the suitability of complementary metal oxide semiconductor (CMOS) active pixel sensor (APS) devices for scientific imaging applications. CMOS APS offer a number of advantages over the established charge-coupled device (CCD) technology, primarily in the areas of low power consumption, high-speed parallel readout and random (X-Y) addressing, increased system integration and improved radiation hardness. The investigation used a range of newly designed Test Structures in conjunction with a range of custom developed test equipment to characterise device performance. Initial experimental work highlighted the significant non-linearity in the charge conversion gain (responsivity) and found the read noise to be limited by the kTC component due to resetting of the pixel capacitance. The major experimental study investigated the contribution to dark signal due to hot-carrier injection effects from the in-pixel transistors during read-out and highlighted the importance of the contribution at low signal levels. The quantum efficiency (QE) and cross-talk were also investigated and found to be limited by the pixel fill factor and shallow depletion depth of the photodiode. The work has highlighted the need to design devices to explore the effects of individual components rather than stand-alone imaging devices and indicated further developments are required for APS technology to compete with the CCD for high-end scientific imaging applications. The main areas requiring development are in achieving backside illuminated, deep depletion devices with low dark signal and low noise sampling techniques.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: During this research the possibility of using carbon nanostructures in sensors were investigated. Graphene and carbon nanotubes (CNTs) are the nano- structures that were used in the developed sensors. Graphene is a single atomic layer of carbon and a carbon nanotube (CNT) is a rolled up sheet of graphene that forms a tube. The unique structure and incredible properties of both these materials make them ideal to be used in sensory applications. A graphene sensor was developed and experiments were performed to determine whether graphene is a viable candidate to be used in a wide range of sensory applications. The graphene sensor operated successfully as a humidity sensor and this led to the discovery that humidity can be used to control the bandgap in graphene. The absorption of CO2 in graphene was successfully measured using surface acoustic waves. As a result, any gas that graphene absorbs can be detected using this method. The use of graphene in three liquid applications was tested. The graphene showed no potential to be used as a pH sensor or as a ow sensor. An experiment was undertaken to determine whether graphene can increase the e ciency of a water electrolysis process, but it was established that the graphene does not make a signi cant di erence. A CNT gas sensor that identi es a gas based on its ionization characteristics was studied and designed. Due to the insu cient height of the grown CNTs, it was decided to focus on the creation of a model of the sensor that can be used to design it optimally. The results of the experiments con rmed that carbon nanostructures such as graphene and CNTs have potential to be used in future sensing applications.
AFRIKAANSE OPSOMMING: Hierdie navorsing ondersoek die moontlikheid om koolstof-nanostrukture in sensor-apparate te gebruik. Grafeen en koolstof-nanobuisies (KNB) is die nanostrukture wat in die ontwikkelde sensors gebruik is. Grafeen is 'n enkel atomiese koolsto agie en KNBs is 'n opgerolde grafeenlagie wat 'n buisie vorm. Die unieke struktuur en ongeloo ike eienskappe van beide hierdie materiale, maak hulle uiters geskik om in sensor-toepassings gebruik te word. 'n Grafeensensor is ontwikkel en eksperimente is uitgevoer om te bepaal of grafeen 'n goeie kanidaat is om in 'n wye verskeidenheid van toepassings gebruik te word. Die grafeensensor is suksesvol aangewend as 'n humiditeitsensor en dit het gelei tot die uitvindsel dat humiditeit gebruik kan word om die energiegaping in grafeen te varieer. Die absorpsie van CO2 in grafeen is suksesvol gemeet deur oppervlak akoestiese golwe te gebruik. Gevolglik kan enige gas wat grafeen absorbeer op hierdie manier gemeet word. Die gebruik van grafeen is in drie vloeistof-toepassings getoets. Die grafeen het geen potensiaal getoon om as 'n pH-sensor of as 'n vloei-sensor aangewend te word nie. 'n Eksperiment is ook uitgevoer om te toets of grafeen die e ektiwiteit van 'n water-elektroliese proses kan verhoog, maar die resultate het gewys dat dit nie 'n wesenlike verskil maak nie. 'n KNB-gassensor, wat 'n gas identi seer uit die ioniseerings eienskappe van die gas, is bestudeer en ontwikkel. Die lengte van die KNBs wat gegroei is, was onvoldoende en daar is gefokus op die ontwerp van 'n model van die sensor wat gebruik kan word om dit optimaal te ontwerp. Die resultate van die eksperimente het bevestig dat koolstof-nanostrukture soos grafeen en KNB baie potentiaal het om in toekomstige sensor-toepassings gebruik te word.

A novel glucose oxidase based needle-type glucose microsensor has been developed for subcutaneous glucose monitoring. The new configuration greatly facilitates the deposition of uniform enzyme and polymer films so that sensors with satisfactory in vitro characteristics (upper limit of linear range (>15 mM) and response time (<5 min) can be prepared in high yield (>60%). The sensor is equivalent in size to a 26 gauge needle (0.45 mm o.d.) and can be implanted with ease without any incision. The insertion of the sensor causes minimal trauma to the tissue and to the sensor itself. The multilayer structure of the sensor ensures satisfactory performance in subcutaneous tissue over extended periods of time (up to 20 days). The sensor response is largely independent of oxygen tension in the normal physiological range. It also exhibits the desired sensitivity and selectivity. A two-point in vivo calibration procedure is adapted for in vivo evaluation of the sensors. Both short-term and long-term implantation experiments are described. The methods of cell culture toxicity testing are modified and applied to locate the source of toxicity in a multi-component glucose sensor. It is shown that a non-toxic sensor can be readily obtained by removing the leachable toxic substances through extraction in phosphate buffer. A nonenzymatic glucose sensor that utilizes permselective membranes to achieve the selectivity required for screening glucose in biological fluids has been described. Interference from endogenous oxidizable substances such as amino acids, urea, ascorbic acid, and uric acid, as well as the effect of chloride and proteins on glucose response, is studied by using flow injection analysis. A set of membranes made of Nafion perfluorinated membrane and collagen, when arranged in front of the working electrode (gold), result in significant improvement in the system selectivity and sensitivity.

La motivació principal darrera d’aquesta tesi és el desenvolupament de nous sensors (bio)químics de baix cost que puguin assentar les bases pel disseny de plataformes de detecció robustes, econòmicament assequibles, escalables i fàcils d’utilitzar. La primera estratègia es basa en la incorporació de polímers conductors per aconseguir un rendiment analític millorat i al mateix temps, unes característiques finals del dispositiu d’assequibilitat i senzillesa en el seu ús. La segona part aborda l’exploració i el desenvolupament de sensors per al diagnòstic no invasiu, amb l’objectiu de millorar la qualitat de vida dels usuaris finals. El treball comença introduint la importància de la detecció de peròxid d’hidrogen, incloent algunes de les seves moltes aplicacions en diferents camps, i una breu descripció de l’estructura de la tesi i els objectius. A continuació es presenten alguns dels treballs més recents en la detecció de peròxid d’hidrogen utilitzant polímers conductors. La comparació del rendiment analític així com els reptes a afrontar en un futur també són descrits en la tesi. Fruit d’aquests reptes, la primera part de la tesi es basa en el desenvolupament de noves estratègies per la determinació de peròxid d’hidrogen en forma de treball experimental. La segona part enfoca el desenvolupament de sensors electroquímics basats en l’ús enzims oxidasa per la detecció de peròxid d’hidrogen com a producte de la reacció principal. A més a més, s’expliquen també els fonaments científics de les tècniques utilitzades i els principis de detecció en que es basa la tesi.
La motivación principal detrás de esta tesis es el desarrollo de nuevos sensores (bio)químicos de bajo coste que puedan sentar las bases para el diseño de plataformas de detección robustas, económicamente asequibles, escalables y fáciles de usar. La primera estrategia se basa en la incorporación de polímeros conductores para conseguir un rendimiento analítico mejorado y al mismo tiempo, unas características finales del dispositivo de asequibilidad y sencillez en su uso. La segunda parte abarca la exploración y el desarrollo de sensores para el diagnóstico no invasivo, con el objetivo de mejorar la calidad de vida de los usuarios finales. El trabajo empieza introduciendo la importancia de la detección del peróxido de hidrógeno, incluyendo algunas de sus muchas aplicaciones en distintos campos, i una breve descripción de la estructura de la tesis y sus objetivos. A continuación se presentan algunos de los trabajos más recientes en la detección de peróxido de hidrógeno utilizando polímeros conductores. La comparación del rendimiento analítico así como los retos a afrontar en un futuro también se describen en la tesis. Fruto de estos retos, la primera parte de la tesis se basa en el desarrollo de nuevas estrategias para la determinación de peróxido de hidrógeno en forma de trabajo experimental. La segunda parte enfoca el desarrollo de sensores electroquímicos basados en el uso de enzimas oxidasa para la detección de peróxido de hidrógeno como producto de la reacción principal. Además, se explican también los fundamentos científicos de las técnicas usadas y los principios de detección en los que se basa la tesis.
The main motivation behind this doctoral thesis is the development of novel and low-cost (bio)chemical sensors that can set the basis to design robust, affordable, scalable and user-friendly sensing platforms. The first approach is based on the incorporation of conducting polymers to achieve enhanced analytical performance as well as desirable final device features, such as affordability and simple operation. The second part of the thesis is addressed on the exploration and development of biosensors for non-invasive diagnostics, with the aim of improving the quality of life of potential end-users. The work begins by introducing the importance of the determination of hydrogen peroxide, including some of its several applications in different fields and a brief description of the thesis structure and objectives. It continues by presenting some of the most recent works on hydrogen peroxide detection using conducting polymers. A critical comparison of the analytical performance and some of the future challenges are described. Fruit of these challenges, the first part of the thesis is based on the development of new approaches for such detection in the form of experimental work. The frame of the second part of the thesis points out the development of electrochemical sensors based on enzymes in order to determine hydrogen peroxide as a byproduct of the main oxidase reaction. In addition, some background of scientific foundation, technological methods and principles on which the work stands is also provided.

There has been an enormous growth in the usage of smartphones in recent times. Smartphones are not limited to communication purposes. It has various applications designed as per the daily requirements of humans such as web-searching, online shopping, bank transactions, games, etc. With the increase in the usage of the smartphone, the more useful information is captured and stored by it, which raises the question of security. The goal of this research is to develop two android applications. One is a sensor detector application and the second is a screen lock application. The first application will help the user to identify all the hidden sensors and working sensors on the mobile phone. This application even describes the features and usage of every sensor in detail. Using a graphical description of each sensor which depicts the behaviour of each sensor as per environment/movement. The second application is designed using a combination of two sensors. Screen lock applications contain two main factors. One is to work properly in all cases and efficiently do the functions that are required to do. The second is to maintain a smooth inner system interaction because in addition to locking the screen this application should make sure to hide the display of all the other applications without closing the process of these applications. With the increase in the usage of the smartphone, it becomes difficult for older generations to memorize the security pattern techniques and use them. This thesis develops a simple technique in the mobile authentication android application. The thesis is developed on the Android studio platform. The background functionality of the app is coded in java using android SDK tool and frontend of the application is designed using XML files. The GENYMOTION emulator and a mobile phone are used to test the output.

Micro- and nano- electromechanical devices such as microcantilevers have paved the way for a large variety of new possibilities, such as the rapid diagnosis of diseases and a high throughput platform for drug discovery. Conventional cell assay methods rely on the addition of reagents, disrupting the measurement, therefore providing only the endpoint data of the cell growth experiment. In addition, these methods are typically slow to provide results and time and cost consuming. Therefore, microcantilever sensors are a great platform to conduct cell culturing experiments for cell culture, viability, proliferation, and cytotoxicity monitoring, providing advantages such as being able to monitor cell kinetics in real time without requiring external reagents, in addition to being low cost and fast, which conventional cell assay methods are unable to provide. This work aims to develop and test different types of microcantilever biosensors for the detection and monitoring of cell proliferation. This approach will overcome many of the current challenges facing microcantilever biosensors, including but not limited to achieving characteristics such as being low cost, rapid, easy to use, highly sensitive, label-free, multiplexed arrays, etc. Microcantilever sensor platforms utilizing both a single and scanning optical beam detection methods were developed and incorporated aspects such as temperature control, calibration, and readout schemes. Arrays of up to 16 or 32 microcantilever sensors can be simultaneously measured with integrated microfluidic channels. The effectiveness of these cantilever platforms are demonstrated through multiple studies, including examples of growth induced bending of polyimide cantilevers for simple real-time yeast cell measurements and a microcantilever array for rapid, sensitive, and real-time measurement of nanomaterial toxicity on the C3A human liver cell line. In addition, other techniques for microcantilever arrays and microfluidics will be presented along with demonstrations for the ability for stem cell growth monitoring and pathogen detection.

Historically, electrochemical gas sensors had suffered from several drawbacks such as poor temperature coefficient, leakage, susceptibility to shock and vibration and orientation sensitivity, which led to poor field reliability. In the present work these problems have largely been overcome by superior design, drawing on field experience in fuel cell and battery technology. The culmination of a sensor design embodying a number of unique concepts has revolutionised electrochemical gas sensor analysis and has pioneered the way for many new and hitherto difficult applications. The main features are: (a) A capillary diffusion-limiting barrier, based on gas-through-gas diffusion, with a theoretical temperature coefficient of 0.17% of signal per °C (at 20°C). (b) Very active fuel cell-type Pt black electrodes with large activity reserves giving rise to low span temperature coefficients, wide dynamic measurement ranges and enhanced long-term stability. (c) A close-wick sandwich arrangement of the electrodes conferring very good stability, to the extent that the sensors are substantially immune to shock and orientation problems. The sandwich design also enables the sensors to be very compact. (d) Use of strong sulphuric acid electrolyte in balance with ambient relative humidity (RH) - about 65% on average in temperate climates - in conjunction with a wick dipping into an expansion reservoir, giving maintenance-free, continuous dynamic range of operation between 20% and 90% RH and very long residence times outside these limits -several weeks in zero RH and several months in 100% RH at 20°C. (e) Extensive use of porous polytetrafluoroethylene (PTFE) membrane sealing techniques, which have dramatically improved cell integrity to the extent that leakage is virtually eliminated.(f) Matched sensing and reference electrodes in conjunction with zero bias cell operation, which allows the sensing and reference electrodes to be shorted out when the instrument is switched off; this gives almost instant warm-up when the instrument is switched on and the cell has excellent (NULL) stability under all conditions. (g) Since the sensor does not need to be powered-up when the instrument is switched off, there is a considerable saving on battery power in portable, hand-held instruments. (h) Inclusion of a second sensing (auxiliary) electrode, which enables the cancellation of partially reacting cross-interfering gases such as hydrogen. The auxiliary electrode can also substantially offset baselines; this is especially beneficial in biased sensors which generate large baselines. (i) Use of inboard chemical filters, which can remove cross interfering gases such as NO, N02, SO2, C12, NH3 and C2H4 by chemical reaction/adsorption.

This work focuses on the development of a hyperthermal, neutral atomic oxygen (AO) sensor that can be used on a wide variety of spacecraft platforms and in ground-based atomic oxygen environment simulators. Carbon has been identified as the sensitive medium for sensing the AO and one of the most important aspects of this work was selecting the most appropriate type of carbon for a particular AO dose. This work fabricates carbon films by physical vapour deposition (PVD) and screen-printing techniques to provide different thicknesses and erosion rates, which affect the sensitivity and life of the sensor. Screen-printed films provided a useful means of detecting large AO doses (fluences), whilst the thinner PVD films provide a more sensitive film for smaller AO fluences. Attempts are also made at interpreting the data to measure the rate of AO (flux). A combination of characterisation techniques confirm that the carbon films react by chemical removal of the carbon, which is also detected by measuring changes in electrical resistance. This work also postulates that the disorder of the carbon films (measured by Raman spectroscopy) can have an effect on the erosion rate of the material. Results from this work will eventually be compared with two low Earth orbiting spacecraft experiments: STORM on the International Space Station and CANX-2. These experiments are described and engineering details relevant to the sensors are also included.

The cochlea is known to exhibit a nonlinear, mechanical amplification which allows the ear to detect faint sounds, improves frequency discrimination, and broadens the range of sound pressure levels that can be detected. In this work, active artificial hair cells (AHC) are proposed and developed which mimic the nonlinear cochlear amplifier. Active AHCs can be used to transduce sound pressures, fluid flow, accelerations, or another form of dynamic input. These nonlinear sensors consist of piezoelectric cantilever beams which utilize various feedback control laws inspired by the living cochlea. A phenomenological control law is first examined which exhibits similar behavior as the living cochlea. Two sets of physiological models are also examined: one set based on outer hair cell somatic motility and the other set inspired by active hair bundle motility. Compared to passive AHCs, simulation and experimental results for active AHCs show an amplified response due to small stimuli, a sharpened resonance peak, and a compressive nonlinearity between response amplitude and input level. These bio-inspired devices could lead to new sensors with lower thresholds of sound or vibration detection, improved frequency sensitivities, and the ability to detect a wider range of input levels. These bio-inspired, active sensors lay the foundation for a new generation of sensors for acoustic, fluid flow, or vibration sensing.
Ph. D.

The gravitational wave observatory and many other large ground-based instruments need to be decoupled from the Earth’s ever-present motion to improve their performance. In such scenarios, inertial sensors which measure the ground motion are necessary, especially those with a high resolution and a large dynamic range. This thesis aims to develop high performance inertial sensors which outperform the commercially available ones in terms of resolution and dynamic range in low frequency down to 0.01 Hz.Inertial sensors essentially consist of two parts: a single-degree-of-freedom mechanism and a transducer which converts mechanical quantities into electrical quantities. In this work, a novel interferometric readout based on homodyne quadrature interferometer is proposed and examined. Experimental results show that its resolution is 1e-11, 1e-12 and 2e-13 m/rtHz at 0.01, 0.1 and 1 Hz respectively. For the mechanical parts, the leaf spring pendulum and Lehman pendulum are used respectively as the restoring springs for the vertical and horizontal inertial sensors. With these, the resonance frequencies are made to 0.26 and 0.11 Hz, respectively. Combined with the interferometric readout, a Vertical Interferometric Inertial Sensor (VINS) and a Horizontal Interferometric Inertial Sensor (HINS) are developed. They are placed together in a vacuum chamber as an inertial unit to measure vertical and horizontal motion.A critical investigation of the developed HINS and VINS is performed. The passive VINS and HINS are compared, firstly, with a commercial seismometer (Guralp 6T) the results showed that they provide equivalent seismograms in frequencies from tides to 10 Hz. Secondly, both simulations and measurements have been conducted in this study, a noise budget of the interferometric readout itself was constructed, which corresponds to the case when the proof-mass of the inertial sensors is blocked. At present, the resolution of the interferometric readout is found to be limited by the photodetector noise from 0.01 to 1 Hz. Moreover, huddle tests were conducted for the inertial units to examine their overall performance. However, extra experiments and simulations are performed and it is found that the resolution identified from the experimental means is worse than that from the simulation. Nevertheless, the mismatch can be reduced by reducing the magnitude of input ground vibration, by reducing undesired inputs and improving the stability of the interferometric readout output signal.
Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished

IoT- technology, Internet of Things, is a fast-growing business, it means that more and more products, clothes, even people are provided with sensors that can communicate and perceive the surroundings to create a smarter community. For companies to keep up to date, it is essential to continuously provide products with better components and reduced size. To stand out further, companies should provide revolutionary products, with totally new feature. One of these ideas, of a new kind of product with special features, have been investigated and developed in this thesis. The thesis has been conducted with the company CombiQ, located in Jönköping, Sweden. The product that was going to be developed was an industrial sensor, that uses the technology of IIoT, Industrial Internet of Things, that the company develops. At the time when this project took place, CombiQ did not sell any own product, only the technology that was placed inside the products. To develop the industrial sensor for CombiQ, not only the functions of the product had to be investigated, further the brand had to be analyzed to create a design expression reflecting the company. Through implement several tools and methods, from among other things the product development process and design thinking, a concept of an industrial sensor is presented that fulfill the specific requirements and functions. Where the main-feature is that the sensor should be a modular solution to be adjusted for the specific need of the clients. Furthermore, during the project a visual brand language with design guidelines have been developed to reflect the design aspects of the company CombiQ. Design guidelines can be used for further product for the company in the same manners, which also has been displayed by developing design concept of the rest of the industrial sensor that counts to the same product family as the modular sensor.
IoT-teknologi, Internet of Things, är en snabbt växande marknad, det innebär att mer och mer produkter, kläder, även människor förses med sensorer som i sin tur kan förstå omgivningen och kommunicera, detta för att skapa ett smartare samhälle. För att företag ska kunna vidhålla positionen på marknaden är det viktigt att hela tiden erbjuda produkter med bättre komponenter och mindre till storleken. För skapa en starkare position, företaget borde erbjuda revolutionerande produkter med unika egenskaper. Det är en av de här idéerna som har undersökts i det här examensarbetet. Arbetet har skett under ett samarbete med företaget CombiQ, belägen i Jönköping. Produkten som skulle tas fram var en industriell sensor, som skulle använda sig av IIoT-teknologin, Industrial Internet of Things, som företaget utvecklar. Tidpunkten när det här arbete utfördes, CombiQ hade inga egna produkter men all teknologi som sitter i sensorerna. För att ta fram en industriell sensor för CombiQ behövde inte bara möjligheterna att tillverka en produkt utefter funktionerna undersökas. Varumärket behövde även analyseras för att utveckla en produkt som uttrycker företaget och dess varumärke på rätt sätt. Genom att tillämpa metoder och verktyg från både produktutvecklingsprocesser och designprocesser, kunde ett koncept tas fram som uppfyllde de uppställda kraven och funktionerna. Den huvudsakliga funktionen i sensorn var att produkten skulle bestå av moduler och på det viset kunna justeras utefter vad kunden behöver. Vidare, under projektet har även CombiQ som varumärke undersökts och riktlinjer för designen har tagits fram som reflekterar företaget och dess varumärke. Design riktlinjerna kan användas för att ta fram ytterligare produkter med samma maner, vilket har visats i detta arbete genom att ta fram designkoncept på ytterligare produkter som räknas till samma produktfamilj som sensorn med moduler.

Today, additive manufacturing (AM) technology is well-known to everybody: each of us has, at least once, heard about that and many have already seen a 3D printer at work. In last years, the cost reduction of 3D printers has meant that AM was no longer used just for rapid prototyping but, also, for the manufacturing of many end-use products. Moreover, its benefits (the material efficiency, the possibility to produce complex shapes in very fast time and at low-cost,...), attracted also the scientists, leading them to use this technology in their research. Recently, 3D-printing made its appearance in the microwave field, and the number of papers presenting devices fabricated with this technology grows every year more. It is within this scenario that my PhD thesis is contributing, being entirely dedicated to 3D-printing technology and its applications in the development of microwave devices. In particular, my work is focused on the realization of microfluidic devices based on resonant cavities. The devices were designed, fabricated, and experimentally verified to demonstrate the potential of merging the microwave field with 3D printed sensing devices. The thesis is organized in six chapters. In the first part, an introductory frame outlines the panorama in which the PhD thesis is situated, together with the state of the art of AM and microfluidics as applied to the microwave field and, eventually, the adopted technologies. The second part, the core of the thesis, deals with the fabricated microfluidic sensors, that is, devices that allow to extract liquids' dielectric properties. The retrieval of liquids properties, i.e., dielectric permittivity and loss tangent, has very important applications in chemical and biological fields. In this work, microfluidic sensors are realized through 3D-printed resonant cavities with a (3D-printed) pipe inside, where liquids under test (LUT) can be injected and their properties extracted. Sensors with two different geometries have been analyzed. The first one consists in a square Substrate Integrated Waveguide (SIW) cavity with a multi-folded pipe inside. In the second structure, instead, the high quality factor of spherical-like shapes is exploited. A pumpkin-shape cavity resonator is fabricated, with a pipe passing, straight, between the two poles. One of the main advantages of AM fabrication is the possibility of emptying both structures, so to minimize as much as possible the dielectric losses due to the substrate. Moreover, the pumpkin structure, realized with a 2 mm-thick dielectric shell, was metallized in the inner part, thanks to electroplating. This guaranteed an increase in quality factor, especially if compared with the square structure. Both these structures were tested with nine different liquids, consisting of mixtures of water and isopropanol. To extract dielectric permittivity and loss tangent of the LUTs, the shift in the resonant frequency on one hand and the change of the quality factor on the other hand, have been considered. In particular, the procedure for the extraction of the dielectric permittivity has been improved, with respect to what can be read in literature, and also a novel method for the extraction of the loss tangent is proposed. The intention to create a self-sustained device for the retrieval of LUTs properties, is then pointed out. Such an investigation has culminated in the realization of an oscillator based on the aforementioned 3D-printed resonator. The design of the oscillator was performed in such a way to obtain an output signal with a working frequency similar to the resonator one and dependent on the LUT injected in the cavity. With a spectrum analyzer, the oscillation frequency was measured in different cases, and the permittivity of the different LUTs was obtained with good accuracy.
Today, additive manufacturing (AM) technology is well-known to everybody: each of us has, at least once, heard about that and many have already seen a 3D printer at work. In last years, the cost reduction of 3D printers has meant that AM was no longer used just for rapid prototyping but, also, for the manufacturing of many end-use products. Moreover, its benefits (the material efficiency, the possibility to produce complex shapes in very fast time and at low-cost,...), attracted also the scientists, leading them to use this technology in their research. Recently, 3D-printing made its appearance in the microwave field, and the number of papers presenting devices fabricated with this technology grows every year more. It is within this scenario that my PhD thesis is contributing, being entirely dedicated to 3D-printing technology and its applications in the development of microwave devices. In particular, my work is focused on the realization of microfluidic devices based on resonant cavities. The devices were designed, fabricated, and experimentally verified to demonstrate the potential of merging the microwave field with 3D printed sensing devices. The thesis is organized in six chapters. In the first part, an introductory frame outlines the panorama in which the PhD thesis is situated, together with the state of the art of AM and microfluidics as applied to the microwave field and, eventually, the adopted technologies. The second part, the core of the thesis, deals with the fabricated microfluidic sensors, that is, devices that allow to extract liquids' dielectric properties. The retrieval of liquids properties, i.e., dielectric permittivity and loss tangent, has very important applications in chemical and biological fields. In this work, microfluidic sensors are realized through 3D-printed resonant cavities with a (3D-printed) pipe inside, where liquids under test (LUT) can be injected and their properties extracted. Sensors with two different geometries have been analyzed. The first one consists in a square Substrate Integrated Waveguide (SIW) cavity with a multi-folded pipe inside. In the second structure, instead, the high quality factor of spherical-like shapes is exploited. A pumpkin-shape cavity resonator is fabricated, with a pipe passing, straight, between the two poles. One of the main advantages of AM fabrication is the possibility of emptying both structures, so to minimize as much as possible the dielectric losses due to the substrate. Moreover, the pumpkin structure, realized with a 2 mm-thick dielectric shell, was metallized in the inner part, thanks to electroplating. This guaranteed an increase in quality factor, especially if compared with the square structure. Both these structures were tested with nine different liquids, consisting of mixtures of water and isopropanol. To extract dielectric permittivity and loss tangent of the LUTs, the shift in the resonant frequency on one hand and the change of the quality factor on the other hand, have been considered. In particular, the procedure for the extraction of the dielectric permittivity has been improved, with respect to what can be read in literature, and also a novel method for the extraction of the loss tangent is proposed. The intention to create a self-sustained device for the retrieval of LUTs properties, is then pointed out. Such an investigation has culminated in the realization of an oscillator based on the aforementioned 3D-printed resonator. The design of the oscillator was performed in such a way to obtain an output signal with a working frequency similar to the resonator one and dependent on the LUT injected in the cavity. With a spectrum analyzer, the oscillation frequency was measured in different cases, and the permittivity of the different LUTs was obtained with good accuracy.

Stratospheric ozone is known to be the most important atmospheric factor determining clear sky UV radiation reaching the Earth's surface. There are, however, other effects that influence the UV radiant energy transfer: cloud cover, aerosols, tropospheric ozone, and other gaseous pollutants. The relationships between various phenomena taking place in the atmosphere are complex and not well known. Therefore, ground based UV measurements are necessary to explore atmospheric changes and resultant effects on the biosphere and on the life. Moreover in this century the human will travel in space and in such environments the UV effects on health and on materials are not yet completely understood. An instrument that can measure one or several effective irradiation from ultraviolet solar emission must have an increasing sensitivity with decreasing wavelength and should be temperature stabilized and long term reproducible, moreover the response of the sensor should be in agreement with the cosine law. These are only some important condition for the design of a good sensor, but how to obtain a particular spectral response that can reconstruct a biological effectiveness? This work regards the development of innovative sensors for biological effective UV measurements and their possible applications in research field on earth and in space environments.

A sensor is a technological device or biological organ that detects, or senses, a signal or physical condition and chemical compounds. Technological developments in the recent decades have brought along with it several environmental problems and human safety issues to the fore. In today's world, therefore, sensors, which detect toxic and inflammable chemicals quickly, are necessary. Gas sensors which form a subclass of chemical sensors have found extensive applications in process control industries and environmental monitoring. The present thesis reports the attempt made in development of Zinc oxide thin film based gas sensors. ZnO is sensitive to many gases of interest like hydrocarbons, hydrogen, volatile organic compounds etc. They exhibit high sensitivity, satisfactory stability and rapid response. In the present work the developed sensors have been tested for their sensitivity for a typical volatile organic compound, acetone. An objective analysis of the various substrates namely borosilicate glass, sintered alumina and hard anodized alumina, has been performed as a part of this work. The substrates were evaluated for their electrical insulation and thermal diffusivity. The microstructure of the gas sensitive film on the above mentioned substrates was studied by SEM technique. The gas sensitive Zinc oxide film is deposited by D.C reactive magnetron sputtering technique with substrate bias arrangement. The characterization of the as-deposited film was performed by XRD, SEM and EDAX techniques to determine the variation of microstructure, crystallite size, orientation and chemical composition with substrate bias voltage. The thesis also describes the development of the gas sensor test setup, which has been used to measure the sensing characteristics of the sensor. It was observed that the ZnO sensors developed with higher bias voltages exhibited improved sensitivity to test gas of interest. Gas sensors essentially measure the concentration of gas in its vicinity. In order to determine the distribution of gas concentration in a region, it is necessary to network sensors at remote locations to a host. The host acts as a gateway to the end user to determine the distribution of gas concentration in a region. However, wireless gas sensor networks have not found widespread use because of two inherent limitations: Metal oxide gas sensors suffer from output drift over time; frequent recalibration of a number of sensors is a laborious task. The gas sensors have to be maintained at a high temperature to perform the task of gas sensing. This is power intensive operation and is not well suited for wireless sensor network. This thesis reports an exploratory study carried out on the applicability of gas sensors in wireless gas sensor network. A simple prototype sensing node has been developed using discrete electronic components. A methodology to overcome the problem of frequent calibration of the sensing nodes, to tackle the sensor drift with ageing, is presented. Finally, a preliminary attempt to develop a strategy for using gas sensor network to localize the point of gas leak is given.

A sensor is a technological device or biological organ that detects, or senses, a signal or physical condition and chemical compounds. Technological developments in the recent decades have brought along with it several environmental problems and human safety issues to the fore. In today's world, therefore, sensors, which detect toxic and inflammable chemicals quickly, are necessary. Gas sensors which form a subclass of chemical sensors have found extensive applications in process control industries and environmental monitoring. The present thesis reports the attempt made in development of Zinc oxide thin film based gas sensors. ZnO is sensitive to many gases of interest like hydrocarbons, hydrogen, volatile organic compounds etc. They exhibit high sensitivity, satisfactory stability and rapid response. In the present work the developed sensors have been tested for their sensitivity for a typical volatile organic compound, acetone. An objective analysis of the various substrates namely borosilicate glass, sintered alumina and hard anodized alumina, has been performed as a part of this work. The substrates were evaluated for their electrical insulation and thermal diffusivity. The microstructure of the gas sensitive film on the above mentioned substrates was studied by SEM technique. The gas sensitive Zinc oxide film is deposited by D.C reactive magnetron sputtering technique with substrate bias arrangement. The characterization of the as-deposited film was performed by XRD, SEM and EDAX techniques to determine the variation of microstructure, crystallite size, orientation and chemical composition with substrate bias voltage. The thesis also describes the development of the gas sensor test setup, which has been used to measure the sensing characteristics of the sensor. It was observed that the ZnO sensors developed with higher bias voltages exhibited improved sensitivity to test gas of interest. Gas sensors essentially measure the concentration of gas in its vicinity. In order to determine the distribution of gas concentration in a region, it is necessary to network sensors at remote locations to a host. The host acts as a gateway to the end user to determine the distribution of gas concentration in a region. However, wireless gas sensor networks have not found widespread use because of two inherent limitations: Metal oxide gas sensors suffer from output drift over time; frequent recalibration of a number of sensors is a laborious task. The gas sensors have to be maintained at a high temperature to perform the task of gas sensing. This is power intensive operation and is not well suited for wireless sensor network. This thesis reports an exploratory study carried out on the applicability of gas sensors in wireless gas sensor network. A simple prototype sensing node has been developed using discrete electronic components. A methodology to overcome the problem of frequent calibration of the sensing nodes, to tackle the sensor drift with ageing, is presented. Finally, a preliminary attempt to develop a strategy for using gas sensor network to localize the point of gas leak is given.

El monitoreig ambiental basat en sistemes de biosensors té molta rellevància, no només en el camp de la investigació sinó també en aplicacions reals a nivell industrial. Això és degut als avantatges d’aquestes plataformes analítiques com, especialment, la seva simplicitat i alta rendibilitat pel seu cost. A més, els avenços recents en nanociència i nanotecnologia incrementen donen lloc a nous nanomaterials que tenen propietats elèctriques interessants com ara la seva capacitat de millorar la conductivitat dels elèctrodes. Aixó té un interès particular de cara al desenvolupament de sistemes de biosensors electroquímics. La combinació de nanomaterials amb biosensors electroquímics permeten construir eines d’anàlisi poderoses per al monitoreig mediambiental. Aquest és l’objectiu principal d’aquesta tesi, que descriu el desenvolupament i l’aplicació de tres nous biosensors pel monitoreig mediambiental mitjançant l’ús de nanomaterials. El primer capítol de la tesi proporciona una introducció general sobre el monitoreig mediambiental de contaminants i dona una breu descripció i classificació d’aquests components nocius. També dona una visió de la rellevància de l’ús de nanomaterials en sistemes de biosensors pel monitoreig mediambiental amb una detallada revisió dels últims treballs publicats que descriuen aspectes innovadors així com possibles inconvenients. Al capítol 3 es descriu una plataforma de monitoreig mediambiental basada en la inhibició de l’enzim acetilcolinesterasa. El sistema desenvolupat utilitza partícules magnètiques i l’enzim acetilcolinesterasa sobre elèctrodes de diamant dopats amb Bor. Gràcies a l’ús de partícules magnètiques i a les característiques de la superfície de l’elèctrode, aquesta plataforma és utilitzada com a sistema multi ús amb una alta reproducibilitat que és capaç de mesurar el pesticida chlorpyrifos en mostres reals d’aigua de riu (riu Yokoama, Japó). Al capítol 4 s’explica el desenvolupament de d’un sistema de detecció simultània de contaminants, el catecol (un derivat fenòlic) i el chlorpyrifos (un pesticida del grup dels organofosfats). Aquesta detecció s’aconsegueix utilitzant elèctrodes serigrafiats de carboni (screen printed carbon electrodes, SPCE) modificats amb nanopartícules d’òxid d’Iridi i amb tirosinasa. El biosensor proposat millora la sensibilitat en la detecció del catecol si es compara amb altres biosensors ja descrits en la bibliografia. Aquest biosensor mostra també una elevada sensibilitat en la detecció de chlorpyrifos quan s’utilitza el mode d’operació d’inhibició de la tirosinasa. Finalment, s’ha explorat l’eficiència del biosensor per aplicacions reals en aigua de riu i aigua de l’aixeta mostrant grans possibilitats per futures aplicacions com a plataforma de baix cost. El tercer biosensor desenvolupat s’explica al capítol 5. En aquest capítol es proposa un sistema de biosensors sense enzims basat en nanopartícules d’òxid de coure (CuO) per la detecció de components fenòlics i d’un herbicida altament tòxic, el Diuron. La detecció es fa mitjançant SPCE on les nanopartícules de CuO formen un complex estable amb els components fenòlics que es mesuren a partir de la reacció electroquímica que té lloc a la superfície de l’elèctrode. Val a dir que és una de les primeres aplicacions que s’utilitzen pel monitoreig mediambiental mitjançant l’ús de nanopartícules de CuO. Aquestes nanopartícules mimetitzen el centre actiu de la tirosinasa obtenint resultats comparables a altres plataformes enzimàtiques. Aquesta plataforma analítica pot ser utilitzada en aplicacions amb mostres reals donat que el límit de detecció obtingut es troba en els nivells que demana el monitoreig establerts per la legislació vigent.
Environmental monitoring based on biosensing systems has increased its relevance not only in the research field but also in the real industrial application. This is due to the advantages of such analytical platforms especially their simplicity and their cost/efficiency. Moreover, the recent advances in nanoscience and nanotechnology increase the emerging of new nanomaterials which have interesting electrical properties such as their capacity to improve the electrode conductivity. This has a particular interest in the development of electrochemical biosensing systems. The combination of nanomaterials with electrochemical biosensing platforms can build up powerful analytical tools for the environmental monitoring. This represents the main objective of this PhD Thesis, that divided in six chapters describes the development and application of three new biosensing platforms for environmental monitoring using nanomaterials. The first chapter of the thesis gives a general introduction on environmental monitoring of pollutants and offers a brief description and classification of these compounds. This chapter also gives an overview of the relevance of the use of nanomaterials in biosensing systems for environmental monitoring with a detailed review of the last published works describing also their innovation aspects and also the possible drawbacks. In Chapter 3 the biosensing platform for environmental monitoring based on the inhibition of acetylcholinesterase is described. The developed system uses magnetic beads and acetylcholinesterase enzyme over Boron Doped Diamond Electrode. Moreover, through the use of magnetic beads and the surface characteristics of the electrode, this platform is used as multi use system with high reproducibility able also to measure the pesticide chlorpyrifos in real sample (Yokoama river, Japan). In Chapter 4 a simultaneous detection system of pollutants for catechol (a phenol derivative) and chlorpyrifos (an organophosphate pesticide), is developed. Such sensing is achieved through a SPCE modified with IrOx NPs and tyrosinase. The proposed biosensor reports improvement in the sensitivity for catechol compared to previously reported biosensors. This biosensor shows also a high sensitivity for chlorpyrifos while being used in a tyrosinase inhibition mode operation. Finally the efficiency of this biosensor is explored for real applications in river and tap water showing great possibilities for future application as a low cost platform. In Chapter 5 a free enzymatic bio-sensing system based on CuO nanoparticles for detection of phenols compounds and for a high toxic herbicide (Diuron) is proposed. Such sensing is achieved through a SPCE where CuO NPs create a stable complex with phenolic compounds that are measured through electrochemical reaction at electrode surface. Moreover it is one of the first applications using CuO NPs for environmental monitoring. CuO NPs have the function to mimic the active centre of tyrosinase obtaining results comparable with other enzymatic platforms. This analytical platform can be used for real sample applications due to the fact that the detection limit is within the requested levels of monitoring established by the legislation. Annex A shows a very interesting review over the biosensing systems inenvironmental monitoring using nanomaterials. This review was published in a very high impact factor journal (Chemical Review Impact factor of 46.658).

Nowadays, small autonomous underwater robots are strongly preferred for remote exploration of unknown and unstructured environments. Such robots allow the exploration and monitoring of underwater environments where a long term underwater presence is required to cover a large area. Furthermore, reducing the robot size, embedding electrical board inside and reducing cost are some of the challenges designers of autonomous underwater robots are facing. As a key device for reliable operation-decision process of autonomous underwater robots, a relatively fast and cost effective controller based on Fuzzy logic and proportional-integral-derivative method is proposed in this thesis. It efficiently models nonlinear system behaviors largely present in robot operation and for which mathematical models are difficult to obtain. To evaluate its response, the fault finding test approach was applied and the response of each task of the robot depicted under different operating conditions. The robot performance while combining all control programs and including sensors was also investigated while the number of program codes and inputs were increased.

Ionomeric polymer transducers (IPTs) are an exciting new class of smart materials that can serve a dual purpose in engineering or biomedical applications as sensors or actuators. Most commonly they are used for mechanical actuation, as they have the ability to generate large bending strains and moderate stress under low applied voltages. Although the actuation capabilities of IPTs have been extensively studied, the sensing capabilities of these transducers have yet to be fully explored. The work presented herein aims to investigate the fundamental sensing characteristics of these transducers and apply the acquired knowledge toward the development of an electronic stethoscope for digital auscultation. The sensors were characterized both geometrically and electrically to determine their effectiveness in resolving a signal from sub 1 Hz to 2 kHz. Impedance spectroscopy was used to interrogate the sensing mechanism. Following the characterization of the transducer, a bioâ acoustic sensor was designed and fabricated. The bioâ acoustic sensor was placed over the carotid artery to resolve the arterial pressure waveform in situ and on the thorax to measure the S1 and S2 sounds generated by the heart. The temporal response and spectral content was compared with previously known data and a commercially available electronic stethoscope to prove the acquisition of cardiovascular sounds.
Master of Science

Cette thèse propose une approche rationnelle pour le design de polymères à empreintes moléculaires (MIPs) pour la détection de nitro-explosifs. Les polymères à empreintes moléculaires qui miment la reconnaissance moléculaire biologique, ont l’avantage d’être stables dans des environnements sévères et peuvent adopter différentes formes physiques pour le couplage avec des transducteurs. Leur synthèse est basée sur la co-polymérisation de monomères fonctionnels et réticulants en présence de la molécule cible, ou comme dans cette thèse, d’un analogue ayant une structure proche de celle de la molécule cible. Cela conduit à la formation d’un réseau polymérique tridimensionnel rigide avec des sites de liaison complémentaires en taille, forme et position des groupes fonctionnels de la molécule cible ou de l’analogue. Pour identifier le meilleur monomère fonctionnel pour notre molécule cible, une approche rationnelle basée sur la modélisation moléculaire, la résonance magnétique nucléaire (RMN) et le titrage par calorimétrie isotherme (ITC) a été utilisée. Elle permet d’optimiser le mélange de pré-polymérisation pour identifier le monomère fonctionnel interagissant le plus fortement avec la molécule cible. Les résultats obtenus ont été confrontés à des études de liaison à partir de polymères synthétisés. La formulation polymérique ainsi conçue est intégrée aux surfaces du transducteur sous forme de nanoparticules, de films et de nanoparticules incorporés dans des films de polydopamine électropolymérisés. En plus des polymères traditionnels obtenus par polymérisation radicalaire classique sous forme de particules, des films de MIP à base de polydopamine électropolymérisés ont été étudiés en tant qu'approche alternative pour la détection électrochimique de nitro-explosifs
This thesis proposes a rational design approach towards molecularly imprinted polymers (MIPs) for sensing nitro-explosives. Molecularly imprinted polymers are mimicking biological molecular recognition. They have the advantage to be stable in harsh environments and can be tailored into different physical forms for interfacing with transducers. Their synthesis is based on the co-polymerization of functional and cross-linking monomers in the presence of the target analyte or, as in this thesis, with a structural analogue leading to a rigid three-dimensional polymer network with binding sites complementary to the template in size, shape and position of the functional groups. The choice of the functional monomer was carried out with a rational design approach combining molecular modelling, nuclear magnetic resonance (NMR) and isothermal calorimetry (ITC) studies. This allows to optimize the pre-polymerization mixture in order to get strong complexation between the functional monomer and the template. The obtained results were confronted with binding studies performed on synthesized polymers. The thus designed polymer formulation was interfaced with transducer surfaces in form of nanoparticles, films and nanoparticles embedded into electro-polymerized polydopamine films. In addition to the traditional MIPs by free radical polymerization, molecularly imprinted in-situ electro-polymerized polydopamine films were investigated as an alternative approach for sensing nitro-explosives electrochemically

Carbon nano-materials, both in sp2 (graphene like) and sp3 (diamond) con- figurations are renowned for their unmatched novel properties. In particular, its extremely high electrical conductivity, radiation hardness and electron amplification are widely coveted. This investigation aims to capitalise on the above by developing blood pressure sensors, radiation detectors and signal amplifiers from the said carbon nano-materials. Namely, carbon nanotubes (sp2 carbon) were integrated into a polymer host to form a composite. Where it has been found that by altering the surface functionalisations of carbon nanotubes (non-functionalised, -OH and -COOH) the electrical resistance of the composite could vary drastically as much as 1012Ω to 107Ω. This brings potential benefits in reduced production costs, reduced environmental damage and wider technological adoption of carbon composite based devices. Carbon nanotubes were then encased in a soft and biocompatible host, polydimethylsiloxane (PDMS), in order to fabricate an in vivo blood pressure sensor, exploiting its piezo-resistivity. Results have shown a successful and adequate degree of piezo-resistivity (109Ω to 106Ω for 2D and 4kΩ to 750kΩ for 3D compression) at the desired size-scale of 200μm and 4mm respectively. This is a size equivalent to that of the diameter of blood vessels in question. However, further investigation into re-miniaturisation is recommended for future works. Diamond (sp3 carbon), on the other hand, was used as a longlasting solution to neutron detection for a Trident nuclear submarine, HMS Artful. The investigation entailed a three-phase process of: α-particle detection, LiF conversion layer addition and neutron detection. Results has shown clear signs of α-particle and neutron detection with a device efficiency of 32.3% and 48.3% respectively, as well as γ-ray transparency and sufficient Q-factor between the signal peak and detection peak. Diamond was also used as a signal amplifier that has application as an image intensifier for night-vision goggles where it was found thatby altering the surface functionalisation of nano-diamonds (H, O and LiO) one could enhance or suppress the secondary electron emission effect. Additionally, it was found that the electrical gain from the said secondary electron emission has a strong dependence on the crystal structure of the diamond layer and in turn its growth conditions. Most notably, LiO functional group was found to be more resilient towards higher temperatures (800oC) and electron bombardments but fell short in the amount of electrical gain it generated in comparison to conventional functionalisations such as H. However, the X-ray photoelectron spectroscopy (XPS) results suggest that this may be due to the lack of LiO coverage and upon further investigation, LiO may potentially bode better if not surpass the gain performance of H.

This work describes the development, validation and application of sensor systems to monitor phase transition events of cryoprotectant mixtures in samples and cryopreservation profiles and post-thaw recovery of Lactobacillus delbrueckii subsp. bulgaricus CFL1. Ice nucleation and glass transition (Tg) temperatures influence cell viability during cryopreservation. Knowledge of these phase changes for cryoprotectant mixtures is an essential step in optimising cryopreservation protocols for cell survival. Differential scanning calorimetry (DSC) is used to determine Tg, but the expensive nature of such instrumentation limits its widespread use. Cost-effective sensor systems have been designed to monitor ice-initiation and Tg events in small volume samples of cryoprotectants solutions. Tg values were measured for glycerol, sucrose and Me2SO (with and without NaCl supplement and ice-nucleators) in cryotubes and cryostraws, using temperature and screen-printed impedance sensors. The effect of changes to ice-initiation temperature on Tg was also investigated at different cooling and warming rates by using a Grant Asymptote (EF600) controlled rate freezer. The resulting Tg values obtained by single-channel transition monitoring system (TMS 1) were not significantly different from the values obtained by DSC reported in the literature. However multiple channelled transition monitoring system (TMS 2) requires further circuit modification and multiple screen-printed temperature probes to study the phase-change temperatures and to determine transition events in more than one sample at a time. The lactic acid bacterium (LAB) Lactobacillus delbrueckii was investigated as a model system to monitor the effect of different cryopreservation protocols on post-thaw cell metabolic activity. An important parameter for monitoring the post-thaw quality of LAB for starter culture preparation is the change in pH of the culture medium during incubation at 40 oC. Glass pH combination electrodes are the most common and widely used sensors. However, they are fragile, must be conditioned before use and are not disposable. An alternative to conventional glass electrodes are screen-printed carbon-metal electrodes. Different percentage mixtures of ruthenium and antimony pastes were tested and 54.5% carbon-antimony electrodes gave the best sensitivity and consistency in potentials at fixed pH with a screen-printed salt-bridged Ag/AgCl reference. LAB cultures were cryo-preserved at very rapid, moderate and very slow cooling rates and their post-thaw metabolic activity after overnight incubation in MRS broth was determined using screen-printed pH electrodes. Back to back testing with conventional glass pH sensors was performed to compare responses. Results indicated that early ice-initiation (by means of nucleators) prevents the cells from extensive dehydration (during cooling) and enables maximum post-thaw recovery after incubation (due to equilibrium ice formation and ice melting). In future, screen-printed pH sensors require development with integrated salt-bridged Ag/AgCl reference to make it robust in signalling response. The availability of low cost, disposable, non-fragile sensors and sensor systems to monitor transition events allows the determination of Tg of cryopreservation media during both cooling and warming cycles. A combined screen-printed (impedance + temperature) sensor is proposed for this purpose. A combined screen-printed (pH + reference) sensor would allow the monitoring of metabolic activity in post-thaw and fresh starter cultures of LAB. At present the salt-bridged pH reference is manually attached to the screen-printed pH working electrode but it requires further modifications to the method of attachment. The two sensor systems would enable optimisation of cryopreservation protocols for LAB and could enable such measurements to become routine at commercial scale.