Characterization of optical transduction-based molecular systems and nanoparticles for the development of chemical sensors

With the increasing importance that nanotechnologies have in everyday life, it is not difficult to realize that also a single molecule, if properly designed, can be a device able to perform useful functions: such a chemical species is called chemosensor, that is a molecule of abiotic origin that signals the presence of matter or energy. Signal transduction is the mechanism by which an interaction of a sensor with an analyte yields a measurable form of energy. When dealing with the design of a chemosensor, we need to take into account a “communication requirement” between its three component: the receptor unit, responsible for the selective analyte binding, the spacer, which controls the geometry of the system and modulates the electronic interaction between the receptor and the signalling unit, whose physico-chemical properties change upon complexation. A luminescent chemosensor communicates a variation of the physico-chemical properties of the receptor unit with a luminescence output signal. This thesis work consists in the characterization of new molecular and nanoparticle-based system which can be used as sensitive materials for the construction of new optical transduction devices able to provide information about the concentration of analytes in solution. In particular two direction were taken. The first is to continue in the development of new chemosensors, that is the first step for the construction of reliable and efficient devices, and in particular the work will be focused on chemosensors for metal ions for biomedical and environmental applications. The second is to study more efficient and complex organized systems, such as derivatized silica nanoparticles. These system can potentially have higher sensitivity than molecular systems, and present many advantages, like the possibility to be ratiometric, higher Stokes shifts and lower signal-to-noise ratio.

Design and experimental characterization of antennas and wireless systems for innovative wearable and implantable ultra low–power applications

The present PhD thesis exploits the design skills I have been improving since my master thesis’ research. A brief description of the chapters’ content follows. Chapter 1: the simulation of a complete front–end is a very complex problem and, in particular, is the basis upon which the prediction of the overall performance of the system is possible. By means of a commercial EM simulation tool and a rigorous nonlinear/EM circuit co–simulation based on the Reciprocity Theorem, the above–mentioned prediction can be achieved and exploited for wireless links characterization. This will represent the theoretical basics of the entire present thesis and will be supported by two RF applications. Chapter 2: an extensive dissertation about Magneto–Dielectric (MD) materials will be presented, together with their peculiar characteristics as substrates for antenna miniaturization purposes. A designed and tested device for RF on–body applications will be described in detail. Finally, future research will be discussed. Chapter 3: this chapter will deal with the issue regarding the exploitation of renewable energy sources for low–energy consumption devices. Hence the problem related to the so–called energy harvesting will be tackled and a first attempt to deploy THz solar energy in an innovative way will be presented and discussed. Future research will be proposed as well. Chapter 4: graphene is a very promising material for devices to be exploited in the RF and THz frequency range for a wide range of engineering applications, including those ones marked as the main research goal of the present thesis. This chapter will present the results obtained during my research period at the National Institute for Research and Development in Microtechnologies (IMT) in Bucharest, Romania. It will concern the design and manufacturing of antennas and diodes made in graphene–based technology for detection/rectification purposes.

Scene Reconstruction And Understanding By RGB-D Sensors

This thesis investigates interactive scene reconstruction and understanding using RGB-D data only. Indeed, we believe that depth cameras will still be in the near future a cheap and low-power 3D sensing alternative suitable for mobile devices too. Therefore, our contributions build on top of state-of-the-art approaches to achieve advances in three main challenging scenarios, namely mobile mapping, large scale surface reconstruction and semantic modeling. First, we will describe an effective approach dealing with Simultaneous Localization And Mapping (SLAM) on platforms with limited resources, such as a tablet device. Unlike previous methods, dense reconstruction is achieved by reprojection of RGB-D frames, while local consistency is maintained by deploying relative bundle adjustment principles. We will show quantitative results comparing our technique to the state-of-the-art as well as detailed reconstruction of various environments ranging from rooms to small apartments. Then, we will address large scale surface modeling from depth maps exploiting parallel GPU computing. We will develop a real-time camera tracking method based on the popular KinectFusion system and an online surface alignment technique capable of counteracting drift errors and closing small loops. We will show very high quality meshes outperforming existing methods on publicly available datasets as well as on data recorded with our RGB-D camera even in complete darkness. Finally, we will move to our Semantic Bundle Adjustment framework to effectively combine object detection and SLAM in a unified system. Though the mathematical framework we will describe does not restrict to a particular sensing technology, in the experimental section we will refer, again, only to RGB-D sensing. We will discuss successful implementations of our algorithm showing the benefit of a joint object detection, camera tracking and environment mapping.

Biomedical engineering for healthy ageing. Predictive tools for falls

Falls are common and burdensome accidents among the elderly. About one third of the population aged 65 years or more experience at least one fall each year. Fall risk assessment is believed to be beneficial for fall prevention. This thesis is about prognostic tools for falls for community-dwelling older adults. We provide an overview of the state of the art. We then take different approaches: we propose a theoretical probabilistic model to investigate some properties of prognostic tools for falls; we present a tool whose parameters were derived from data of the literature; we train and test a data-driven prognostic tool. Finally, we present some preliminary results on prediction of falls through features extracted from wearable inertial sensors. Heterogeneity in validation results are expected from theoretical considerations and are observed from empirical data. Differences in studies design hinder comparability and collaborative research. According to the multifactorial etiology of falls, assessment on multiple risk factors is needed in order to achieve good predictive accuracy.

Rod-shaped plasmonic sensors

Plasmonic nanoparticles exhibit strong light scattering efficiency due to the oscillations of their conductive electrons (plasmon), which are excited by light. For rod-shaped nanoparticles, the resonance position is highly tunable by the aspect ratio (length/width) and the sensitivity to changes in the refractive index in the local environment depends on their diameter, hence, their volume. Therefore, rod-shaped nanoparticles are highly suitable as plasmonic sensors.rnWithin this thesis, I study the formation of gold nanorods and nanorods from a gold-copper alloy using a combination of small-angle X-ray scattering and optical extinction spectroscopy. The latter represents one of the first metal alloy nanoparticle synthesis protocols for producing rod-shaped single crystalline gold-copper (AuxCu(1-x)) alloyed nanoparticles. I find that both length and width independently follow an exponential growth behavior with different time-constants, which intrinsically leads to a switch between positive and negative aspect ratio growth during the course of the synthesis. In a parameter study, I find linear relations for the rate constants as a function of [HAuCl4]/[CTAB] ratio and [HAuCl4]/[seed] ratio. Furthermore, I find a correlation of final aspect ratio and ratio of rate constants for length and width growth rate for different [AgNO3]/[HAuCl4] ratios. I identify ascorbic acid as the yield limiting species in the reaction by the use of spectroscopic monitoring and TEM. Finally, I present the use of plasmonic nanorods that absorb light at 1064nm as contrast agents for photoacoustic imaging (BMBF project Polysound). rnIn the physics part, I present my automated dark-field microscope that is capable of collecting spectra in the range of 450nm to 1750 nm. I show the characteristics of that setup for the spectra acquisition in the UV-VIS range and how I use this information to simulate measurements. I show the major noise sources of the measurements and ways to reduce the noise and how the combination of setup charactersitics and simulations of sensitivity and sensing volume can be used to select appropriate gold rods for single unlabeled protein detection. Using my setup, I show how to estimate the size of gold nano-rods directly from the plasmon linewidth measured from optical single particle spectra. Then, I use this information to reduce the distribution (between particles) of the measured plasmonic sensitivity S by 30% by correcting for the systematic error introduced from the variation in particle size. I investigate the single particle scattering of bowtie structures — structures consisting of two (mostly) equilateral triangles pointing one tip at each other. I simulate the spectra of the structures considering the oblique illumination angle in my setup, which leads to additional plasmon modes in the spectra. The simulations agree well with the measurements form a qualitative point of view.rn

Implementation of a VLSI amplifier interfaced with biomedical sensors for ultra wide band data transmission

This thesis presents a CMOS Amplifier with High Common Mode rejection designed in UMC 130nm technology. The goal is to achieve a high amplification factor for a wide range of biological signals (with frequencies in the range of 10Hz-1KHz) and to reject the common-mode noise signal. It is here presented a Data Acquisition System, composed of a Delta-Sigma-like Modulator and an antenna, that is the core of a portable low-complexity radio system; the amplifier is designed in order to interface the data acquisition system with a sensor that acquires the electrical signal. The Modulator asynchronously acquires and samples human muscle activity, by sending a Quasi-Digital pattern that encodes the acquired signal. There is only a minor loss of information translating the muscle activity using this pattern, compared to an encoding technique which uses astandard digital signal via Impulse-Radio Ultra-Wide Band (IR-UWB). The biological signals, needed for Electromyographic analysis, have an amplitude of 10-100μV and need to be highly amplified and separated from the overwhelming 50mV common mode noise signal. Various tests of the firmness of the concept are presented, as well the proof that the design works even with different sensors, such as Radiation measurement for Dosimetry studies.

Sistemi Informatici Mobili e Realtà Aumentata a supporto del lavoro cooperativo in scenari d'emergenza: studio e realizzazione di un caso applicativo

Scopo primario della tesi è studiare e progettare un sistema informatico che proponga un buon livello di innovazione tecnologica in relazione al contesto applicativo di riferimento, ovvero relativamente al supporto al lavoro cooperativo di operatori in scenari d'emergenza. In particolare, la tesi si concentra sul'ecosistema software che ruota attorno al singolo operatore con l'obiettivo di dotarlo di uno strumento informatico che gli consenta di avvalersi di un efficace ed efficiente supporto per l'esecuzione delle proprie azioni sul campo (in generale, per la prima assistenza ai pazienti, triage e monitoraggio di parametri vitali). A tal proposito, l'ambito tecnologico di riferimento è quello del Pervasive Mobile Computing, con specifico riferimento ai sistemi context-aware e a quelli con comportamenti fortemente autonomi. Inoltre, al fine di dotare l'operatore di un supporto per l'interazione con il sistema stesso in modalità hands-free, sono stati analizzati i dispositivi wearable di tipo "see-through"; in particolare, i recenti glasses per realtà aumentata. La progettazione del sistema e il conseguente sviluppo del prototipo (che implementa le caratteristiche più significative ed innovative), è stata guidata da un'ispirazione basata sul modello ad agenti (integrato a quello ad oggetti), rivisitando opportunamente l'utilizzo dei componenti offerti dalla tecnologia Android, al fine di ottenere un prodotto software robusto e modulare facilmente manutenibile ed estendibile. Infine, per garantire a ciascun operatore rapida fruibilità del sistema sono state sfruttate le potenzialità offerte dall'uso di smartcard NFC ed inoltre è stato progettato un protocollo di comunicazione ad hoc, basato su stack Bluetooth, per l'integrazione degli AR-Glasses all'intero sistema.

Discovery di dispositivi embedded e raccolta di dati con bluetooth e bluetooth smart

L'obbiettivo di questa tesi è la produzione del prototipo di un sistema che sia in grado di ottenere dati da un insieme di sensori per poterli poi trasmettere all’utente, in modo che esso sia maggiormente cosciente del mondo che lo circonda. Affronteremo la sfida in uno scenario medico / di soccorso, dove un operatore si avvicinerà ad un gruppo di pazienti con l’intenzione di ottenere i parametri vitali di uno di essi. All'interno del documento saranno descritte le tecnologie sfruttate per la realizzazione del prototipo: Bluetooth e Bluetooth Smart, il sistema operativo Linux in esecuzione su un Raspberry Pi dotato di sensori, il sistema operativo Android in esecuzione su smartphone o tablet e iBeacon. Verranno poi analizzati i requisiti del sistema da realizzare. Infine verrà descritta l'implementazione utilizzata nel prototipo e analizzato il suo comportamento.

Novel metallo-porphyrin based colourimetric amine sensors and their processing via plasma enhanced chemical vapour deposition at atmospheric pressure : synthesis, characterisation and mechanistic studies

Volatile amines are prominent indicators of food freshness, as they are produced during many microbiological food degradation processes. Monitoring and indicating the volatile amine concentration within the food package by intelligent packaging solutions might therefore be a simple yet powerful way to control food safety throughout the distribution chain.rnrnIn this context, this work aims to the formation of colourimetric amine sensing surfaces on different substrates, especially transparent PET packaging foil. The colour change of the deposited layers should ideally be discernible by the human eye to facilitate the determination by the end-user. rnrnDifferent tailored zinc(II) and chromium(III) metalloporphyrins have been used as chromophores for the colourimetric detection of volatile amines. A new concept to increase the porphyrins absorbance change upon exposure to amines is introduced. Moreover, the novel porphyrins’ processability during the deposition process is increased by their enhanced solubility in non-polar solvents.rnrnThe porphyrin chromophores have successfully been incorporated into polysiloxane matrices on different substrates via a dielectric barrier discharge enhanced chemical vapour deposition. This process allows the use of nitrogen as a cheap and abundant plasma gas, produces minor amounts of waste and by-products and can be easily introduced into (existing) roll-to-roll production lines. The formed hybrid sensing layers tightly incorporate the porphyrins and moreover form a porous structure to facilitate the amines diffusion to and interaction with the chromophores.rnrnThe work is completed with the thorough analysis of the porphyrins’ amine sensing performance in solution as well as in the hybrid coatings . To reveal the underlying interaction mechanisms, the experimental results are supported by DFT calculations. The deposited layers could be used for the detection of NEt3 concentrations below 10 ppm in the gas phase. Moreover, the coated foils have been tested in preliminary food storage experiments. rnrnThe mechanistic investigations on the interaction of amines with chromium(III) porphyrins revealed a novel pathway to the formation of chromium(IV) oxido porphyrins. This has been used for electrochemical epoxidation reactions with dioxygen as the formal terminal oxidant.rn

Plasmonic nanoparticles as sensors : a novel approach to quantify adsorption and diffusion kinetics

Biosensors find wide application in clinical diagnostics, bioprocess control and environmental monitoring. They should not only show high specificity and reproducibility but also a high sensitivity and stability of the signal. Therefore, I introduce a novel sensor technology based on plasmonic nanoparticles which overcomes both of these limitations. Plasmonic nanoparticles exhibit strong absorption and scattering in the visible and near-infrared spectral range. The plasmon resonance, the collective coherent oscillation mode of the conduction band electrons against the positively charged ionic lattice, is sensitive to the local environment of the particle. I monitor these changes in the resonance wavelength by a new dark-field spectroscopy technique. Due to a strong light source and a highly sensitive detector a temporal resolution in the microsecond regime is possible in combination with a high spectral stability. This opens a window to investigate dynamics on the molecular level and to gain knowledge about fundamental biological processes.rnFirst, I investigate adsorption at the non-equilibrium as well as at the equilibrium state. I show the temporal evolution of single adsorption events of fibrinogen on the surface of the sensor on a millisecond timescale. Fibrinogen is a blood plasma protein with a unique shape that plays a central role in blood coagulation and is always involved in cell-biomaterial interactions. Further, I monitor equilibrium coverage fluctuations of sodium dodecyl sulfate and demonstrate a new approach to quantify the characteristic rate constants which is independent of mass transfer interference and long term drifts of the measured signal. This method has been investigated theoretically by Monte-Carlo simulations but so far there has been no sensor technology with a sufficient signal-to-noise ratio.rnSecond, I apply plasmonic nanoparticles as sensors for the determination of diffusion coefficients. Thereby, the sensing volume of a single, immobilized nanorod is used as detection volume. When a diffusing particle enters the detection volume a shift in the resonance wavelength is introduced. As no labeling of the analyte is necessary the hydrodynamic radius and thus the diffusion properties are not altered and can be studied in their natural form. In comparison to the conventional Fluorescence Correlation Spectroscopy technique a volume reduction by a factor of 5000-10000 is reached.

Libreria per comunicazioni ad-hoc per android basate su bluetooth

La tesi sviluppa, attraverso un processo definito e gestito, una libreria Android che permette di far comunicare diversi dispositivi mobili tramite Bluetooth. Inoltre gestisce: • le richieste di connessione sia che esse provengano dall’esterno, sia che partano dal dispositivo stesso; • la dinamicità del sistema utilizzando dispositivi mobili, cioè capaci di muoversi in diverse direzioni costantemente. In tal senso, la lista dei dispositivi vicini è costantemente aggiornata. • la comunicazione in stile Peer-to-Peer(P2P). In questo caso si viene a formare un gap in quanto la libreria Android di Bluetooth usa lo stile Master-Slave per i suoi dispositivi. Per colmare questo gap, la libreria sviluppata crea un layer soprastante la libreria Bluetooth di Android e maschera lo stile di comunicazione di quest’ultima a favo- re di una comunicazione paritaria, nella quale un dispositivo può sia accettare le richieste di connessione, sia connettersi ad altri dispositivi.

Progettazione di un applicativo di supporto al monitoraggio di team situati

Lo scopo della tesi e quello di giungere alla realizzazione di un prototipo, che si basi su tecnologie specifiche quali GPS, Android e Bluetooth, per l'infrastruttura di un sistema che può essere visto come l'unione di tre macro parti distinte, centrale di controllo, dispositivo mobile e pulsossimetro. Concentrandosi in particolare sugli ultimi due componenti citati e realizzando un sistema di comunicazione che si basa su un Web Service ispirato al modello REST, si giungerà, attraverso un attento processo logico dettato dai canoni dell'ingegneria del software, al prototipo finale. Il prototipo che sarà realizzato rappresenterà oltre che un primo sistema funzionante e operativo, un punto di partenza per estensioni future, con lo scopo di perfezionare le funzionalità già esistenti o di fornirne di aggiuntive.

Prototipo di schermo adattativo basato su Android e Bluetooth Low Energy

La tesi nasce da un'attività di ricerca approfondita su alcune tecnologie innovative e all'avanguardia nell'ambito del mobile computing e dell'Internet of Things. Tra queste il focus principale è orientato allo studio del Bluetooth Low Energy, nuova specifica di Bluetooth caratterizzata principalmente da un consumo di energia assai ridotto. In particolare, si è approfondito il suo funzionamento nel caso dei beacon, piccoli dispositivi che permettono una localizzazione mediante l'invio di un segnale BLE. Inoltre è stata analizzata la possibilità di interazione con Android, poiché oggigiorno non si può evitare di pensare a come queste tecnologie possano interfacciarsi con il mondo degli smartphone e dei tablet. Come conseguenza di tale attività di ricerca è stato analizzato un caso di studio che permettesse di applicare le tecnologie studiate e la loro interazione. Si è pensato quindi a un piccolo sistema distribuito per schermi adattativi (capaci di modificare i contenuti visualizzati in relazione ad eventi esterni) affinché ogni schermo mostrasse dinamicamente l'orario delle lezioni di ciascuno studente all'avvicinarsi di quest'ultimo, e solo per il tempo di permanenza nei pressi dello schermo. Si è quindi progettato e sviluppato un prototipo, e infine durante il testing si sono potute verificare le attuali potenzialità di queste tecnologie e trarre conclusioni sulla possibilità della loro futura diffusione e di impiego in contesti differenti.

Applicazioni di tecnologie IoT e wearable alla domotica: un caso di studio

Oggigiorno milioni di persone fanno uso di Internet per gli utilizzi più disparati: dalla ricerca di informazioni sul Web al gioco online; dall'invio e ricezione di email all'uso di applicazioni social e tante altre attività. Mentre milioni di dispositivi ci offrono queste possibilità, un grande passo in avanti sta avvenendo in relazione all'uso di Internet come una piattaforma globale che permetta a oggetti di tutti i giorni di coordinarsi e comunicare tra di loro. È in quest'ottica che nasce Internet of Things, l'Internet delle cose, dove un piccolo oggetto come un braccialetto può avere un grande impatto nel campo medico per il monitoraggio da remoto di parametri vitali o per la localizzazione di pazienti e personale e l'effettuazione di diagnosi da remoto; dove un semplice sensore ad infrarosso può allertarci a distanza di una presenza non autorizzata all'interno della nostra abitazione; dove un'autovettura è in grado di leggere i dati dai sensori distribuiti sulla strada. Questa tesi vuole ripercorrere gli aspetti fondamentali di Internet of Things, dai sistemi embedded fino alla loro applicazione nella vita odierna, illustrando infine un progetto che mostra come alcune tecnologie IoT e wearable possano integrarsi nella domotica, come per esempio l'utilizzo di uno smartwatch, come Apple Watch, per il controllo dell'abitazione.

Realizzazione di un'interfaccia universale in tecnologia Bluetooth Low Energy per sensori integrati

Lo scopo dell’elaborato di tesi è la progettazione e lo sviluppo di un’applicazione per il modulo Bluetooth Low Energy (BLE) Texas Instrument CC2650 in grado di leggere le informazioni da un sensore analogico, tramite un Analog-Digital- Converter (ADC), e di scambiare i dati con uno smartphone Android in tempo reale. L’interfaccia realizzata deve essere universale, ovvero dovrà essere compatibile con sensori di diverso tipo, facilmente estensibile per l’aggiunta di un numero maggiore di periferiche di lettura e utilizzabile con un ampio numero di dispositivi.