Tesis Doctorals - Departament - Electrònica

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Development of cellular microarrays for stem cell culture and early stage differentiation evaluation
(Universitat de Barcelona, 2010-01-15) Rodríguez Seguí, Santiago Andrés; Samitier i Martí, Josep; Martínez Fraiz, Elena; Universitat de Barcelona. Departament d'Electrònica
[spa] El desarrollo de microambientales artificiales ordenados en un formato de microarray (microarrays celulares, también conocidos en inglés como "cellular microarrays") se ha propuesto como una herramienta que permite el análisis a gran escala de combinaciones de factores que afectan la diferenciación de células madre. Este novedoso acercamiento puede implementarse para imitar superficies planas y de esta forma estudiar su diferenciación, este fin tiene directas implicaciones en el desarrollo de nuevos biomateriales y en ingeniería de tejidos. El objetivo general del presente trabajo de tesis consistió en el diseño y evaluación de microarrays celulares construidos con células madre con el objetivo de estudiar su diferenciación hacia osteoblastos (células óseas) en función de los factores impresos. A estos fines, se utilizó una trazadora de microarrays (microarray plotter) para realizar los microarrays donde diversos factores inmovilizados en micro islas impresas sobre substratos activados químicamente (vidrio y polimetilmetacrilato (PMMA), entre otros). Sobre estos substratos impresos se cultivaron células por períodos de 1 a 8 días y se evaluó su diferenciación al cabo de este tiempo de cultivo. En la presente tesis se hizo una comparación de substratos en función de la cantidad de proteína impresa que retienen inmovilizada en su superficie. Otro objetivo consistió en optimizar los parámetros para la formación del microarray celular (tales como tiempo y concentración de sembrado de células, medio de cultivo, etc..). Finalmente se evaluó la diferenciación de una línea celular hacia osteoblastos en función de la presencia o no de un factor de crecimiento inmovilizado en las islas de microarray.
Vibrational properties of ZnO, group III-nitrides and dilute nitride alloys
(Universitat de Barcelona, 2009-07-07) Alarcón Lladó, Esther; Garrido Fernández, Blas; Artús i Surroca, Lluís; Universitat de Barcelona. Departament d'Electrònica
[spa] Esta tesis consiste en el estudio de las propiedades vibracionales de materiales de interés para la fabricación de dispositivos optoelectrónicos, operando en distintos rangos espectrales, desde ultravioleta hasta el infrarrojo.
Development of a compact NDIR spectometer based on MOEMS components for fruit ripening monitoring
(Universitat de Barcelona, 2009-07-20) Fonollosa Magrinyà, Jordi; Marco Colás, Santiago; Moreno Sereno, Mauricio; Universitat de Barcelona. Departament d'Electrònica
[spa] Actualmente el control de la concentración de etileno en las cámaras de almacenamiento de fruta proporciona información de gran interés sobre su estado. Por un lado, la fruta produce pequeñas concentraciones de etileno que indican su estado de maduración, y por otro lado, se añade etileno para acelerar el proceso de maduración. En esta Tesis, se ha desarrollado un espectrómetro óptico multicanal para medir de forma contínua la concentración de etileno en las cámaras frigoríficas. Se ha diseñado y fabricado componentes ópticos y la correspondiente electrónica de amplificación y procesado de señal. El resultado es un espectrómetro de gases basado en una aqrquitectura NDIR. En la tendencia actual de integración y miniturización, se ha diseñado un novedoso detector IR como componente del sistyema NDIR. El detector consta de una matriz 2x2 de termopilas, filtros ópticos para seleccionar las bandas de absorción y una matriz 2x2 de lentes de Fresnel fabricadas en un mismo sustrato silíceo. La etapa electrónica está formada por una parte de pre-amplificación analógica y otra parte digital basada en un lock-in. El instrumento se ha testeado a nivel de laboratorio y simulando condiciones reales. El resultado es que el espectrómetro es capaz de detectar 30 ppm de etileno, que es una concentración de amoníaco, que puede ser útil para detectar una posible fuga del sistema de refrigeración.
Structural analysis for the improvement of SnO(2) based gas sensors
(Universitat de Barcelona, 1999-09-29) Diéguez Barrientos, Àngel; Morante i Lleonart, Joan Ramon; Romano Rodríguez, Albert; Universitat de Barcelona. Departament d'Electrònica
[spa] La investigación presentada está centrada en la mejora de sensores de gas conductométricos de Sn02. Se analizan sensores en capa gruesa y en capa delgada. En el primer caso, el polvo de Sn02 necesario para fabricar los sensores ha sido elaborado mediante la técnica de sol-gel. Tras la obtención de un precursor (Sn02 hidratado), se han realizado estudios de calcinación, introducción de aditivos metálicos (Pt, Pd) y, por primera vez, un molido del material. Gracias a la disponibilidad de nanopartículas con tamaño de grano entre 3 y 100 nm, se ha podido analizar por primera vez el espectro Raman completo de nanoparticulas de Sn02, a partir el cual se presentan tres metodos diferentes para determinar de forma no destructiva el tamaño de grano medio y la distribución de tamaños de partícula en un sensor. Del estudio del molido del material de deduce que a través de éste se puede controlar la microestructura de las nanopartículas, asi como el estado de su superficie, permitiendo un control de la resistencia de base de los sensores y una mejora de su selectividad. Los sensores en capa delgada se han fabricado mediante las técnicas IBAD i RGTO, en crecimiento mono y multicapa. Se presenta en el trabajo un estudio detallado del depósito de Sn y de su oxidacón termica, extrayéndose de la investigación de los parámetros de la difusión del O en el Sn, así como las diferentes fases intermedias en la conversión de Sn a Sn02. Mediante el método RGTO multicapa se consigue reducir el tiempo de oxidación, así como mejorar la sensitividad de los sensores.
Suspended Micro/nanogenerators for cell stimulation
(Universitat de Barcelona, 2019-01-17) Vargas Estevez, Carolina; Esteve, Jaume; Murillo, Gonzalo; Universitat de Barcelona. Departament d'Electrònica
[eng] Our bodies are complex machines whose functioning depends on multiple electrical signals controlled mainly by the nervous system. Afterwards, it is not illogical to think that one day artificial electrical impulses would replace those signals offering supports of medical treatments. Nowadays electrical stimulation is used in many therapeutic applications to modulate cellular activity, restore biological lost functions or even improve the performance of certain tissues. However, these systems still carry side effects link to the surgical interventions to place them or place their electrodes, their inherent bulkiness or lack in specificity to target only the cells involved in the condition to treat. The future to transcend these constrains would be possible in the extent that technology ease the path to improve precision, autonomy and miniaturization of the actual therapeutic tools. In this context, micro- and nanogenerators play a key role as self-powered devices with high spatial resolution and acute cell specificity. This thesis aims to provide micro/nanogenerators to stimulate single cells in its own liquid media. This work explored two technological branches based on photovoltaic and on magnetoelastic (piezoelectric/magnetostrictive) devices to harvest energy. Their fabrication was accomplished through semiconductors microfabrication technologies and their performance was characterized through several tests to ensure their correct power generation. As these devices were intended to interface biological media, direct cytotoxicity studies were conducted to guarantee their safety. Both branches were biologically validated with in vitro models of excitable cells (embryonic mouse neurons and human osteoblast- like cells) analyzing the electrostimulation effects through morphological changes and through instantaneous ionic responses as calcium signaling. The results gathered in this research demonstrated the feasibility of these micro- and nanogenerators as self-powered electrical stimulators. Furthermore, their reduce size and capability to be suspended in liquid media open the door to further developments towards injected or ingested minimally invasive medical tools.
New technologies and their characterisation for nanostructured SnO2 Gas sensor devices
(Universitat de Barcelona, 2000-09-29) Cirera Hernández, Albert; Cornet i Calveras, Albert; Universitat de Barcelona. Departament d'Electrònica
[spa] La presente tesis se ha centrado en el desarrollo de nuevas tecnologías para el desarrollo de sensores de gas semiconductores. Por tal motivo se han desarrollado dos técnicas para el desarrollo de nanopartículas de SnO2. Paralelamente se ha diseñado y realizado diversos tipos de substratos basados en alúmina y silicio micromecanizados. Con el objetivo de implementar las nanopartículas en estos substratos se han desarrollado dos nuevas técnicas para dicha implementación, llamadas micropinting y recubrimientos por pulverización. Finalmente, con los dispositivos obtenidos se ha concebido un algortimo para la cuantificación de CO y CH4 en mezclas binarias. Desde un punto de vista científico, se ha realizado una caracterización de SnO2 atendiendo a la temperatura de estabilización del material y hallando la evolución nanostructural de dicho óxido de estaño.
Modelling of the Chemical and Light Interactions in Individual Metal Oxide Nanowires for Sensing Applications
(Universitat de Barcelona, 2009-01-29) Prades García, Juan Daniel; Cirera Hernández, Albert; Universitat de Barcelona. Departament d'Electrònica
[spa]En la presente tesis se analizan desde el punto de vista de la modelización teórica los mecanismos de interacción de gases y luz con nanohilos individuales de óxidos metálicos. Desde este enfoque novedoso, se pretende alcanzar una mayor compresión de los mecanismos de transducción que dan lugar a la utilidad de dichos materiales en aplicaciones de sensado químico y de luz. Los resultados que aquí se presentan permiten comprender los detalles de las interacciones de gases, tanto oxidantes como reductores, sobre superficies de óxidos metálicos; siendo especialmente remarcable el descubrimiento del papel clave que juegan las vacantes de oxígeno en superficie en este proceso. Así mismo, se proponen técnicas experimentales tanto para la generación controlada de dichas vacantes como para su posterior detección. De este modo se das las herramientas necesarias para controlar a voluntad la respuesta a gases de estos materiales. Des de el punto de vista de la detección de luz, se demuestra que la gran relevancia de los efectos de superficie en los nanohilos permite obtener fotorespuestas muy por encima de las conseguidas con otras tecnologías pero, como contrapartida, la respuesta dinámica se ve severamente penalizada. Por ello se proponen y demuestran diversos métodos para modificar la influencia de la superficie en la respuesta total de los nanohilos. Finalmente, en base al conocimiento adquirido, se demuestra que es posible acoplar ambas interacciones (gas-óxido metálico y luz-óxido metálico) para ampliar las aplicaciones de estos materiales. En particular, no sólo se demuestra que es posible activar la respuesta a gases por medio de la iluminación, sino que también se presenta un modelo que describe cuantitativamente este fenómeno, abriendo las puertas a un gran número de aplicaciones de detección de gas a temperatura ambiente
Electron Energy Loss Spectroscopy Solutions for Nanoscale Materials Science Problems
(Universitat de Barcelona, 2009-02-21) Estradé Albiol, Sònia; Peiró Martínez, Francisca; Arbiol i Cobos, Jordi; Universitat de Barcelona. Departament d'Electrònica
[eng] In the Transmission Electron Microscope (TEM), an incident electron suffers both elastic and inelastic scattering by the solid state thin sample that is being characterised. In the event of inelastic scattering, the incident electron gives a part of its energy to the electrons in the sample. The amount of lost energy can then be measured by a magnetic filter at the end of the column, and a plot displaying how many electrons have lost what amount of energy will give us an Electron Energy Loss (EEL) Spectrum. Thus, in an EEL Spectrum the ordinate axis corresponds to the number of electrons, or counts, and the abscise corresponds to the Energy Loss. Notice that most electrons shall not suffer any inelastic scattering whatsoever. As a consequence, the greatest contribution to the spectrum is due to these electrons having lost zero energy, giving rise to the so-called zero loss peak (ZLP). As for those electrons having lost a certain amount of energy, they may lose it to ionization of specimen electrons, transitions from occupied core states to unoccupied core states or to conduction band states, to interband transitions or excitations of collective vibrations of conduction band electrons. Incident electrons carry a given momentum, and it is worth keeping in mind that in an inelastic scattering event not only energy, but also momentum, may be transferred. In fact, this is the reason why it is not straightforward to compare EELS results with those obtained by means of optic spectroscopies. EELS detectors can provide an energy resolution down to the order of the 0.1 eV. In addition, incident electrons can be tuned by TEM optics, making it possible to get spectroscopic information from an extremely constrained area, and to combine EEL Spectroscopy with TEM imaging.
Study of cell response over nanopatterned ligands on diblock copolymer surfaces
(Universitat de Barcelona, 2017-06-30) Hortigüela, Verónica; Martínez Fraiz, Elena; Universitat de Barcelona. Departament d'Electrònica
[eng] Cells in tissues are exposed to extracellular signals that integrate and appropriately translate into specific responses. Receptors at the cell membrane recognize a variety of soluble ligands, extracellular matrix proteins and molecules presented by the neighboring cells. Ligand-receptor recognition event triggers intracellular signal transduction pathways modulating the resulting cell function. Some receptors do not function individually as signaling units but require interactions and associations with other receptors in multimolecular complexes. This process is known as receptor clustering and is an evolutionarily preserved mechanism responsible for the integration of highly complex signals. Increasing evidences suggest that this exceptional integration is subjected to spatially controlled ligand distribution at the nanoscale. Recent developments in highly sophisticated nanofabrication approaches have allowed to experimentally address this detailed spatial regulation on cell signaling. However, it is still unclear how the nanoscale distribution of ligands can impact on the dynamics of receptor activation and signaling processes. Herein we present a nanostructured platform to create patterns of ligands in regular nanosized (< 30 nm) clusters. We based our platform in self-assembled diblock copolymers composed of poly(styrene) (PS) and poly(methyl methacrylate) (PMMA) that tend to segregate into nanodomains. The hexagonal arrangement of the PMMA domains acts as template to be replicated by the ligand distribution. Thanks to the versatile functionalization strategy developed, any amine-bearing molecule can be covalently immobilized. The spatial distribution of ligand was analyzed by Atomic force microscopy (AFM) and stochastic reconstruction microscopy (STORM), unveiling the high level of fidelity between the nanopatterned ligands and the underlying polymeric template. To validate these substrates as platforms for systematic study of receptor clustering processes, an adhesive peptide which promotes focal adhesion formation, was immobilized on the nanopatterned surfaces. While the overall ligand surface density was maintained constant, the spatial distribution of ligands showed a remarkable impact on focal adhesion formation. Cells on nanopatterns showed an increased number of focal contacts, which were, in turn, more matured than those found in cells cultured on randomly presenting ligands. These findings suggest that ligand presentation in a clustered format might promote multivalent ligand-receptor interactions which can help to shed light on receptor oligomerization processes. In addition, the nanopatterned substrates developed were used to investigate the dynamics of the process of Eph receptor assembly into oligomeric clusters upon stimulation with ephrin ligands. It is known that Eph receptor oligomer composition is crucial in the fine-tuning of receptor signaling, as it will trigger intracellular signals feedback which will modulate cell response. Oligomerization processes, which imply resolving the temporal evolution of nanometric size objects in diffusive environments such as cell membranes are beyond the reach of live-imaging tools. We in here resolve the oligomerization kinetics of the Eph receptor in live cells with the required spatial and temporal resolution by using an enhanced version of the Number and Brightness (eN&B) technique, which can discriminate with molecular sensitivity the oligomeric species. The results demonstrated that stimulation through surface-bound ligands with a random distribution was not sufficient to activate the receptor signaling. Conversely, when nanopatterned on our substrates, ligands effectively induced receptor oligomerization. In addition, surface-induced ligand clustering by our nanopatterning approach accelerated the dynamics of receptor oligomerization process when compared to antibody-induced ligand clustering. Such an efficiency was induced even when ligand surface coverage was 9-fold lower in the nanopatterned presentation. Therefore, our ligand presenting platform is thought to induce multivalent ligand-receptor interactions, and might be a useful strategy to precisely tune and potentiate receptor responses. It has promising applications in biotechnology and biomedicine, such as cell culture systems to provide insight into relevant receptor clustering processes and design of new bioactive materials and drug-delivery systems.
Integration of Si/Si-Ge nanostructures in micro-thermoelectric generators
(Universitat de Barcelona, 2017-09-22) Gadea, Gerard; Tarancón Rubio, Albert; Morata García, Alex; Universitat de Barcelona. Departament d'Electrònica
[eng] Silicon and silicon-germanium nanostructures were grown, integrated, optimized and characterized for their application in thermoelectric generation. Specifically two kinds of nanostructures were worked: silicon and silicon-germanium nanowire arrays (Si/Si-Ge NW) and polycrystalline silicon nanotube fabrics (pSi NT). The results are dived in four chapters. Chapters 3, 4 and 5 deal with Si/Si-Ge NWs, while chapter 6 presents the pSi NT fabrics. In Chapter 3 the growth and integration of Si/Si-Ge NWs was studied, in order to optimize their properties for thermoelectric application in micro-thermoelectric generators (µTEG). First, the methods for depositing gold nanoparticles prior to NW growth were studied. Second, the growth of NWs from the gold nanoparticles in a Chemical Vapour Deposition (CVD) process was comprehensively studied and optimized for subsequent integration of NWs in µTEGs, both of Si and Si-Ge. All important properties – NW length, diameter, density, doping and alignment – could be controlled by tuning the seeding gold nanoparticles and the process conditions, namely temperature, pressure, flows of reactants and growth time. Finally, integration was demonstrated in micro-structures for thermoelectric generation and characterization. The optimization process yielded to fully integrated thermoelectric Si/Si-Ge NW arrays with diameters and densities of ~100 nm and 5 NW/µm2 respectively. In Chapter 4 the Si NWs were thermoelectrically characterized. The Seebeck coefficient, electrical conductivity and thermal conductivity of arrays and single Si-NWs were measured in microstructures devoted to characterization comprising NWs integrated as in final µTEG application. Additionally a novel atomic force microscope based method for determination of thermal conductivity was explored. Then the results were discussed comparing them with existing literature. A ZT of 0.022 was found at room temperature, revealing an improvement of factor 2-3 with respect to bulk. In Chapter 5 The harvesting capabilities of µTEGs with integrated Si/Si-Ge NWs was assessed. The thermal gradient and the power of the µTEGs was assessed for two generation of devices and for two thermoelectric materials, namely Si and Si-Ge NWs, which were integrated for the first time in functional generators. Also a study on heat sinking and convection effects was conducted adding insight towards further device improvement. Finally, the results were discussed and compared with literature. The maximum power densities attained were 4.5 µW/cm2 for the Si NWs and 4.9 µW/cm2 for the Si-Ge NWs while harvesting over surfaces at 350 ºC. Chapter 6 deals with pSi NT fibers. First this new material concept and the growth route are presented, showing the fabrication steps and the control of the resulting properties by CVD method. Then the material is thermoelectrically characterized, by measuring its Seebeck coefficient and electrical and thermal conductivities up to 450 ºC. A ZT of 0.12 was found, doubling the optimally doped bulk at this temperature. Finally a proof of concept was demonstrated by assessing the thermal harvesting capabilities of the material on top of hot surfaces. A maximum of 3.5 mW/cm2 was attained at 650 ºC.
Development of an advanced 3D culture system for human cardiac tissue engineering
(Universitat de Barcelona, 2017-07-07) Valls Margarit, Maria; Martínez Fraiz, Elena; Raya Chamorro, Ángel; Universitat de Barcelona. Departament d'Electrònica
[eng] Ischemic heart disease is a major cause of human death worldwide owing to the heart minimal ability to repair following injury. Other than heart transplantation, there are currently no effective or long-lasting therapies for end-stage heart failure. Therefore, it is crucial to develop not only alternative therapies that potentiate heart regeneration or repair, but also new tools to study human cardiac physiology and pathophysiology in vitro. In this context, cardiac tissue engineering arises a promising strategy, as it is aimed at generating cardiac tissue analogues that would act as in vitro models of human cardiac tissue or as surrogates for heart repair. Thus, having 3D human cardiac tissue constructs resembling human myocardium could revolutionize drug discovery and toxicity testing, cardiac disease modelling and regenerative medicine. An strategy to obtain reliable cardiac tissue constructs is to mimic the native cardiac environment. The classical approach is based on seeding cardiomyocytes in biocompatible 3D scaffolds, and then culturing the construct in a biomimetic signaling system, usually a bioreactor. Although major advances have been made, the generation of thick and mature tissue constructs from human induced pluripotent stem cells-derived cardiomyocytes (hiPSC-CM) is still a challenge. Therefore, the hypothesis of our study is that the combination of hiPSC-CM with 3D scaffolds and appropriate regulatory signals may lead to the generation of mature human cardiac tissue constructs resembling human myocardium, both functionally and structurally. To address this, we have characterized a collagen-based 3D scaffold and established an efficient method for cell seeding into the scaffold. We have also developed a parallelized perfusion bioreactor system, which ensures an effective mass transport between cells and culture medium and allows culturing multiple replicas of tissue constructs. In addition, we have designed and fabricated a perfusion chamber including electrodes to electrically stimulate cells during culture, as well as to monitor tissue function. With this advanced 3D culture system, we have been able to generate thick 3D human cardiac constructs with tissue-like functionality. Our results indicate that perfusion of culture medium combined with electrical stimulation and collagen-based scaffold improve the structural and functional maturation of hiPSC-CM. In general terms, electrical stimulation has improved the structural organization, alignment and coupling of cardiomyocytes in our cardiac tissue constructs. Moreover, electrical stimulation has promoted the formation of synchronous contractile constructs at the macroscale with improved electrophysiological functions. Through the development of a new electrophysiological recording system, we report for the first time to our knowledge a technique that provides information about the electrical activity of intact cardiac tissue constructs in real time. Specifically, the combination of action potentials generated by hiPSC-CM composing cardiac constructs produces ECG-like signals, which could be monitored online. Finally, we have demonstrated the ability of stimulated human cardiac tissue constructs to detect drug-induced cardiotoxicity, as typical features of arrhythmias (e.g. prolongation of RR intervals and regular blockades) could be observed upon treatment with sotalol. Taken together, results indicate that macroscopic human cardiac tissue constructs with tissue-like functionality can be obtained through the use of our advanced 3D culture system. We have studied the effects of electrical stimulation on cardiomyocytes at multiple levels: molecular (presence, distribution and expression of cardiac proteins), ultrastructural (sarcomere width and presence of specialized cellular junctions), cellular (morphology and alignment), and functional (amplitude, directionality and strain of contractions, and electrophysiological recordings). Findings validate our in vitro approach as a valuable system to obtain 3D cardiac patches with an improved maturity and functionality. Importantly, the online monitoring system developed in this study can provide essential electrophysiological information of intact cardiac tissue constructs, which opens up myriad possibilities in the field of cardiovascular research.
Análisis dinámico de atmósferas con matrices de sensores mediante procesado de señal no-lineal
(Universitat de Barcelona, 2000-06-23) Pardo Martínez, Antonio; Marco Colás, Santiago; Morante i Lleonart, Joan Ramon; Universitat de Barcelona. Departament d'Electrònica
[spa] El presente trabajo se enmarca dentro de las tareas centradas en el campo de modelización y procesado de señal, desarrolladas en el Departament d’Electrònica de la Facultad de Física de la Universitat de Barcelona. En su concepción de nivel más amplio, el trabajo demuestra la posibilidad de trasladar y aplicar con eficiencia las técnicas de procesado y modelización dinámica no lineal al ámbito de los sistemas de medida de gases. Son relativamente abundantes en la literatura otras aproximaciones más simples a esta temática y en este ámbito. Así, es posible encontrar en la literatura trabajos enfocados hacia la modelización estática-lineal, estática-no lineal y dinámica-lineal. Sin embargo, no existían antes de este trabajo aportaciones bajo el enfoque dinámico y no lineal en la modelización de sistemas de medida gaseosos. Por otra parte, el trabajo aborda además el problema desde el punto de vista de la multidimensionalidad junto con la restricción del uso de un reducido número de datos; factores éstos que aportan dificultad adicional a la vez que valor añadido a la solución. En lo concreto, el trabajo se centra en el análisis y modelización del comportamiento de un sistema de medida de gases basado en sensores QMB frente a cambios rápidos de dos concentraciones en una mezcla binaria de gases (tolueno y octano) en aire sintético y bajo régimen de altas concentraciones (miles de ppm). Frente a este problema, la calibración estática es incapaz de aportar una solución con un error tolerable. Por primera vez se ha abordado, frente a la solución estática, la modelización dinámica y no lineal de sistemas analizadores de gases, ofreciendo esta aproximación resultados óptimos. Los experimentos diseñados, orientados hacia la confección de los modelos, fueron fundamentalmente dos: 1) Sistema sometido a concentraciones en forma de escalón 2) Sistema sometido a señales de concentración en forma de ruido blanco con densidad de probabilidad gausiana. Los modelos generados son también de dos tipos: 1) Modelos directos: desde la entrada hacia la salida 2) Modelos inversos: desde la salida hacia la entrada Para la resolución del problema se han probado diferentes estimaciones, como estimadores de correlación, estimaciones paramétricas, series de Volterra, series de Wiener, modelos de cajas y redes neuronales. De entre todos ellos, los modelos basados en series de Wiener y en redes neuronales han demostrado una mayor eficiencia. Se demuestra que estos modelos son capaces de explotar la información del sistema estudiado hasta el límite de la resolución experimental, tanto en la modelización directa como en la inversa. Aparte de la tarea estrictamente relacionada con la modelización, se ha iniciado con este trabajo la construcción de una estación de test de sensores de gas que en la actualidad y después de diversas aportaciones del grupo de trabajo, es un complejo sistema de medición y test capaz de realizar una gran variedad de pruebas relacionadas con gases, dotando al departamento de una línea de trabajo nueva, potente y bien equipada.
Preparation of high efficiency Cu2ZnSn(S,Se)4solar cells based on a single-step sulfo-selenization process
(Universitat de Barcelona, 2016-11-21) Xie, Haibing; Pérez Rodríguez, Alejandro; Universitat de Barcelona. Departament d'Electrònica
[eng] Cu2ZnSn(S,Se)4 (CZTSSe) kesterite semiconductors have been proposed as a potential medium to long term replacement of Cu(In,Ga)(S,Se)2 (CIGS) chalcopyrites for sustainable cost-efficient thin film technologies compatible with mass deployment at Terawatt level, being only constituted by elements abundant in the earth crust in contrast with the scarce Indium in CIGS. In this thesis, high efficiency CZTSSe solar cells were fabricated based on a single-step sulfo-selenization process. CZTSSe absorbers with optimal S/(S+Se) ratio, minimized Zn(S,Se) secondary phases in the interfaces, and good crystal quality were achieved through systematically fine tuning of various processing parameters during thermal treatments. The thermodynamic equilibrium of the single-step sulfo-selenization process was also analysed to elucidate the impact of different parameters on the thin films S/(S+Se) ratio. Besides, to address the big challenge of secondary phases in CZTSSe solar cells, an innovative (NH4)2S etching was developed for the selective and effective removal of Sn-(S,Se) secondary phases. This (NH4)2S etching can also passivate the absorber surface and a passivation mechanism was proposed to explain this behaviour. To further improve the efficiency of the CZTSSe solar cells, the CZTSSe/CdS interface was focused and engineered. Na spatial distribution in the CZTSSe/CdS interface region was optimized by a post low temperature treatment process (PLTT), leading to considerable enhancement of the performance of CZTSSe solar cells. An innovative Na dynamics model was established to illustrate the Na in-depth profiles. In addition, Cu doped CdS was investigated to reduce the thickness of CdS while keeping the comparable performance of the kesterite devices, which provides new possibilities to address the Cd concern. Finally, to suppress the CZTSSe/CdS interface recombination and reduce the Voc deficit of the CZTSSe solar cells, a facile wet chemical route based on AlCl3/GaCl3 + thioacetamide solutions were developed. The Voc and efficiency improvement after the chemical treatments can be mainly ascribed to the decrease of interface recombination and shunt paths. A champion CZTSSe solar cell with 9.1% efficiency and FF over 69% was achieved after all these processing optimizations (no ARC). This demonstrates that the single-step sulfo-selenization methodology is promising and feasible for obtaining high efficiency CZTSSe solar cells. selenization methodology is promising and feasible for obtaining high efficiency CZTSSe solar cells.
Development of Cu2ZnSnSe4 Based Thin Film Solar Cells by PVD and Chemical Based Processes
(Universitat de Barcelona, 2016-09-29) Neuschitzer, Markus; Pérez Rodríguez, Alejandro; Saucedo Silva, Edgardo; Universitat de Barcelona. Departament d'Electrònica
[eng] Nowadays mono- and multicrystalline silicon have the highest market share of all PV technologies but thin film solar cells based on CdTe or Cu(In,Ga)Se2 (CIGS) absorbers recently show promising high power conversion efficiency values and due to their short energy payback time, minimal use of high purity material and low cost, they attract more and more attention. However, one concern of thin film PV based on CdTe or CIGS is the use of scare elements like tellurium or indium and gallium which could become a bottleneck if the technology wants to scale up to the terawatt level. Therefore, there is a high interest to replace these scare elements by more abundant ones and find suitable earth abundant photovoltaic absorbers. Cu2ZnSnSe4 (CZTSe) or Cu2ZnSnS4 (CZTS) and its sulphur-selenide solid solution are promising candidates to replace CIGS as absorber material due to its composition of more earth abundant elements. In literature CZTSe and CZTS are referred to as kesterite due to its crystal structure. However, there is still a large gap between power conversion efficiencies of solar cells based on kesterite absorber material and more established thin film solar cells, thus intensive research is still necessary to close this gap. The main goal of this thesis was to develop and optimize heterostructure solar cells based on Cu2ZnSnSe4 absorbers, by cost effective physical vapour deposition (PVD) and chemical based processes. Special focus is put on an improved understanding of the influence of the surface properties of kesterite absorbers on device performance and furthermore to optimize the front interface, i.e. buffer layer as well as the kesterite absorber layer itself. A detailed study investigating the influence of the surface chemistry on device performance is presented. After a chemical etching to remove unwanted ZnSe secondary phases formed during CZTSe absorber synthesis a low temperature post deposition annealing at 200ºC of the full solar cell is necessary to improve device efficiencies from below 3% to over 8%. X-ray photoelectron spectroscopy (XPS) surface analysis showed that this post deposition annealing promotes the diffusion of Zn towards the surface and Cu towards the bulk resulting in a Zn enriched and Cu depleted surface region, which is crucial for high device performance. Additionally experimental surface treatments confirm the necessity of a Cu-poor and Zn-rich surface and the reason for this beneficial surface composition are discussed in detail. Furthermore, the CdS buffer layer which is typically used in kesterite based heterostructures solar cells was optimized and allowed improvements in device performance of 1% absolute. This optimization was further extended to Cd-free ZnS(O,OH) buffer layer. Efficiencies close to that of CdS reference solar cells could be achieved using optimized ZnS(O,OH) buffer layer. Additionally to the front interface optimization, a Ge assisted crystallization process for nanocrystalline CZTSe precursors was developed which largely increase grain growth and boost open circuit voltages (Voc) to promising high values due to the elimination of deep defects. Since the low Voc values is identified of one of the main bottlenecks of kesterite technology, the improvements achieved are highly promising and give important insight for further possible optimizations.
Compositional Engineering of Colloidal Nanoparticles for Energy Conversion
(Universitat de Barcelona, 2016-12-19) Luo, Zhishan; Cabot i Codina, Andreu; Ibáñez Sabaté, Maria; Universitat de Barcelona. Departament d'Electrònica
[eng] The main objective of this thesis focuses on compositional design and engineering colloidal NPs and their application in energy conversion. This principally included the synthesis and characterization of colloidal NPs, and in-depth exploration of their catalytic properties. Special focus is the synthesis and characterization of copper-based chalcogenides, bimetallic and multicompent metal oxide NPs. The results were shown in the series of articles which have been published or are under review in high impact peer-review journals. These works can be extracted to conclusions as following: (1) Copper-based chalcogenides NPs: Detailed synthetic routes to produce CZTS and CZTS-based HNPs i.e. CZTS-Au, CZTS-Pt and CZTS-Ag2S. The composition, size and shape control of CZTS NCs have been achieved by tuning the precursor concentration, surfactants, gas bubbling and heating ramp. This synthetic strategy method can be easy to scale up to grams at the same time keeping above 90% yield per batch by a simple vacuum free heating-up method. We used CZTS NCs as electrocatalysts with controlled crystal phases for the ORR measurements. First-principles calculations and experiments both indicated the kesterite CZTS NCs exhibit improving electrocatalytic activities toward ORR. In additional, monodisperse CZTS-Au and CZTS-Pt HNPs were obtained base on CZTS as seeds by seed-mediated growth method. Various characterizations confirm the structure of noble-semiconductors HNPs. Such HNPs were investigated on photocatalytic degradation of dye and hydrogen evolution reaction in water, exhibited high catalytic active. The research of CZTS-based HNPs is extended to a detailed synthesis of CZTS-Ag2S HNPs involving cation exchange reaction. The structure and composition of CZTS-Ag2S could be tuned by control the ration of Ag precursors and CZTS seeds. When employing CZTS-Ag2S as sensitizers apply photoelectrochemical cell for water splitting, showed improved photocurrent response under visible-light illumination. (2) Bimetallic NPs: The synthesized Pd2Sn NPs were successfully used solution-based strategy. A mechanism of morphology structure was discussed detail based different ratio of OLA, chlorine and TOP precursors. When evaluating catalytic properties of geometry of Pd2Sn NPs, reduction of nitrophenol, water denitration and EOR were measured resulting in Pd2Sn NRs had outperformance catalytic active over Pd2Sn spherical NPs, while Pd2Sn alloy NPs exhibited better catalytic performance compare to Pd NPs. The formation of novel Au-Pd2Sn heterostructured NRs was described in detail as well. Au-Pd2Sn heterostructured NRs were synthesized via a seed-mediated growth method, which Au domains were selected to grow on the Pd2Sn seeds. The result establishes a new strategy for the development of multifunctional nanomaterials. (3) Multicompent metal oxide NPs: Mn3O4@CoMn2O4 core-shell and Mn3O4@CoMn2O4-CoO HNPs were prepared via partial cation exchange reaction via Mn3O4 seeds NPs and different cobalt precursors, which playing a crucial role whether additional nucleation of a CoO phase depending on the coordination ability of cobalt precursors. The lower coordination ability of cobalt perchlorate had a higher reactivity to grow CoO phase on Mn3O4@CoMn2O4 to form Mn3O4@CoMn2O4-CoO HNPs. In particular, such HNPs showed a superior catalytic activity and stability over the core shell catalysts and state-of-the-art electrocatalysts for ORR and OER in alkaline solution. Based on this colloidal synthetic route, Fe3O4@NixFe3-xO4 core shell NPs was obtained involving nickel perchlorate precursors to Fe3O4 seeds solution. The fabrication of this core shell NPs and ITO glass to form thin film as water oxidation catalyst exhibited an improved catalytic activity. This colloidal synthetic route offers an easy scale-up, low temperature and ambient pressure protocol to design earth-abundant, cost-effective and high activity water oxidation catalysts.
Nanoscale electrical characterization of biological matter at microwave frequencies
(Universitat de Barcelona, 2016-06-20) Biagi, Maria Chiara; Gomila Lluch, Gabriel; Fumagalli, Laura, 1959-; Universitat de Barcelona. Departament d'Electrònica
[eng] The microwaves electromagnetic properties, i.e. the complex permittivity, of single cells determine how this radiation is transmitted, reflected or absorbed by biological tissues. This information is important for the development microwave medical applications in diagnostics and therapy. Moreover, it is also crucial to assess the potential dangerous effects of the exposure to microwave radiations. Dielectric spectroscopy performed allowed to quantify the complex permittivity of tissues and whole single cells. However, there is a lack of information at the sub-cellular and intracellular level, due to the inherent limitations of the techniques, to resolve the dielectric response at the nanoscale. In recent years, Near-Field Scanning Microwave Microscopy (NF-SMM) has appeared as promising alternative to obtain images related to the dielectric response of samples, with high spatial resolution. In SMM, the local reﬂection of microwaves from the sample is measured by means of a sharp probe scanned in close proximity to the sample, i.e. within the near-ﬁeld region. The reflection can be related to the electrical impedance of the samples, and from this, the local complex permittivity can be retrieved. The near-field region ensures the good lateral resolution of the technique, far below the wavelength of the radiation used. SMM has been only scarcely applied to biological samples, and the few studies are limited to qualitative findings. This is due, among other reasons, to the complexity of the interpretation of the data, especially in case of tall irregular samples like cells, where the topography crosstalk effect dominates the signal acquired, thus masking the dielectric response. The objective of my Thesis was precisely to use this technique to quantify the local nanoscale dielectric response of a single cell at microwave frequency. My research focused primarily in the elaboration and implementation of the analysis methodologies suitable to obtain quantitative information from SMM measurements. I elaborated a methodology to disentangle and remove the topography crosstalk effect in the capacitance images acquired by SMM, which allows to extract new capacitance images only related to the intrinsic dielectric response of the sample, and therefore suitable for the quantification. I extracted the permittivity of the sample from the intrinsic capacitance images, by means of data analysis procedures which I adapted from the one available for low frequency measurements within the research group. Among these, the procedures to determine tip and sample geometries and to obtain the permittivity. The procedures were validated on reference samples. I first analysed heterogeneous inorganic thin film, exhibiting large height variations comparable to the ones of bacterial cells. I obtained intrinsic capacitance images at around 19 GHz in contact mode and show these can be directly related to the permittivity of the samples, without the need of theoretical models or the knowledge of the system geometry, and therefore represent maps of the microwave permittivity. I also show that in case of images acquired in intermittent contact mode the interpretation of the capacitance images in terms of the electric permittivity is much more complex. Finally, I obtained intrinsic images, at ~19 GHz, of a single E.coli bacterium, in dry and humid conditions, and, with the help of theoretical models, I extracted the local permittivity. These findings represent the first quantification of the of a single cell ever done at microwaves at the nanoscale, and thus show that SMM is sensitive to the cell constituent and the environment humidity. The results obtained prove that, despite the complexity of the data analysis, the microwave permittivity of biological samples can be quantified with nanoscale resolution, from SMM capacitance images.
Development of electrochemical platforms for DNA sensing
(Universitat de Barcelona, 2016-02-08) Alfonso Pardo, Wilmer; Mir Llorente, Mònica; Samitier i Martí, Josep; Universitat de Barcelona. Departament d'Electrònica
[eng] The present doctoral thesis is framed in the research and development (R & D) project between a private biotechnology company of molecular diagnostics Genomica SAU, the Institute for Bioengineering of Catalonia (IBEC), the University of Barcelona, and the Microfluidics ChipShop Company. The main objective of the project is making, implementation and marketing of a diagnostic device for early detection of DNA sequences involved with cancer. The multi device, or lab-on-chip (LOC), consists of a central automation unit (CAU), a system in miniature of DNA amplification or chain reaction polymerase (mini-PCR), and a biosensing platform (DNA chip) that consisting of a matrix or electrochemical array. The three elements are integrated by a microfluidic system in sandwich format cartridge. For this purpose, the aim of this thesis was the creation, characterization and optimization of the biochemical recognition platform between two single strands of DNA of dissimilar lengths but with some complementary sequences for the subsequent electrochemical detection of a hybridization event between them. Then, the integration into the cartridge of above platform was done. For the creation of this platform, we chose to use a self-assembled monolayer (SAM) of thiols as biorecognition interface of the 14 DNA sequences that are part of the project. During optimization of the interface chips individual gold and various molecules were used being chosen the molecule with two arms disulfide of polyethylene glycol (PEG) and a malaimida group at the end of one of them. This linker (or MalPEG linker) reacts with the gold surface due to the dative interaction between the sulfur atoms of the disulfide and the gold atoms from the surface of the chips. At the same time, the malaimida group reacts with the thiol group of the capture probes, joining. The PEG groups function as anti-adhesion molecules. Surface plasmon resonance (SPR) and cyclic voltammetry (CV) were techniques used to characterize the substrate and the hybridization event. For the manufacture of the cartridge, this was divided into two main blocks, the biosensing or electrochemical block and PCR block. The electrochemical block is composed of 4 layers, one of 64 working electrodes and gold paths for contact with the potentiostat, another layer that defines the area of the sensors must be functionalized gold and isolating the gold surface of the tracks. The third layer is a double-sided adhesive that has a hexagonal hole working as hybridization chamber, and the last layer is a screen printing layer with the reference electrode (RE) and counter electrodes. The above layers form an electrochemical cell wherein the hybridization will occurs. Regarding the PCR block, this is a system of two layers with a type microfluidic channel kind loop and its function is to contain the solutions during the process of DNA amplification by the mini-PCR. During the integration of the optimized SAM into an electrochemical cartridge a manual and automated ways were used to immobilize the capture probes. Several tests were performed in order to obtain the best conditions and ratios between the molecules to maximize the hybridization signal during the electrochemical detection.
Detecció d'estats inadequats per la conducció d'un vehicle a partir de la degradació del control dinàmic
(Universitat de Barcelona, 2016-01-29) Bartra Cisa, Ariadna; Marco Colás, Santiago; Universitat de Barcelona. Departament d'Electrònica
[cat] Una de les principals causes d’accidents d’automòbil és l’estat inadequat del conductor. Diversos estudis situen entre el 16% i el 30% el nombre d'accidents de trànsit relacionats amb el cansament, fatiga, somnolència i estats similars. Per aquest motiu una de les prioritats actuals de grups de recerca i empreses automotrius és el desenvolupament de sistemes capaços de detectar somnolència i/o estats inadequats en conductors. Els diversos mètodes existents per detectar somnolència poden agrupar-se en quatre grans grups: subjectius, fisiològics, visuals i de conducció. Els primers, basats en avaluacions subjectives, presenten una baixa fiabilitat si el conductor és el seu propi avaluador i el seu ús en vehicle no és viable si l’avaluador és extern. Els sistemes basats en informació fisiològica tenen una major fiabilitat però requereixen l’ús de dispositius específics per part del conductor (casc amb elèctrodes, sensors d’activitat cardíaca, banda respiratòria, etc.). Aquest fet és molest pels usuaris i, mentre no es desenvolupi un sensor sense contacte fiable, limita la utilització d’aquests sistemes a conductors professionals d’alt risc (conductors de llargues distàncies, de mercaderies perilloses, etc.). El tercer grup, en canvi, és totalment transparent a l’usuari i analitza, a partir del processat d’imatges, l’atenció del conductor en funció del seu comportament ocular. En condicions de bona il·luminació presenten molts bons resultats, mentre que les il·luminacions irregulars els són problemàtiques, així com l’ús d’ulleres de sol. Finalment, el quart grup de detectors està format per aquells que es basen en l’anàlisi de la conducció del vehicle, els quals són també transparents per l’usuari. La majoria d’aquests detectors estan desenvolupats en simuladors, sense tenir en compte la complexitat d’un entorn real. En aquesta tesi és presentat un sistema per a vehicles reals que estima l’estat del conductor a partir d’una avaluació de la qualitat de la conducció i de la seva interacció amb el vehicle. Partim de la hipòtesi que aquesta qualitat es degrada amb la fatiga i la somnolència. El sistema estudia els senyals disponibles a la xarxa de comunicacions del vehicle (bus CAN) i, opcionalment, les dades proporcionades per una càmera frontal amb un programari específic per la detecció de línies de carril. Per validar la nostra hipòtesi inicial s’han realitzat assajos en simulador amb subjectes privats del son. Les dades obtingudes han estat analitzades i en elles s’han identificat les característiques de la conducció més significatives en somnolència. A continuació s’han dut a terme diferents assajos en vehicle real, en els que s’ha pogut observar un important increment de la complexitat de l’entorn. Per això, en el desenvolupament del detector hem hagut de centrar gran part dels esforços en evitar les falses alarmes. A part dels tres grans mòduls que generen penalitzacions (basats en la posició en el carril, els moviments de volant i les correccions brusques), es presenten a la tesi diversos mòduls centrats en identificar determinades situacions i condicions en la conducció a partir dels que es modula dinàmicament la sensibilitat del sistema. Els resultats obtinguts mostren la possibilitat de detectar estats no aptes mitjançant el control dinàmic del vehicle, sempre i quant aquests es vegin reflectits en la conducció. El sistema final pot treballar exclusivament amb les dades del CAN, tot i que l’adició d’una càmera frontal incrementa la qualitat de la informació d’entrada del sistema. Està optimitzat per treballar en microcontroladors de vehicle, complint amb restriccions temporals i computacionals així com satisfent les principals normatives automotrius.
Síntesis química de capas buffer para nuevas tecnologías de calcogenuros con aplicaciones fotovoltaicas
(Universitat de Barcelona, 2016-03-16) Sánchez González, Yudania; Saucedo Silva, Edgardo; Vigil Galán, Osvaldo; Pérez Rodríguez, Alejandro; Universitat de Barcelona. Departament d'Electrònica
[spa] En éste trabajo de Tesis se presentan los resultados más relevantes obtenidos en el desarrollo de capas buffer de CdS y de capas buffer libres de cadmio (sulfuro de indio y sulfuro de zinc) preparadas mediante la técnica de baño químico, más conocida por sus siglas en inglés CBD (Chemical Bath Deposition). La finalidad de estas capas buffer es el procesamiento de celdas solares de bajo coste basadas en calcogenuros de cobre, fundamentalmente CZTSSe. La producción de celdas solares de bajo coste, alta eficiencia mediante una tecnología respetuosa con el medioambiente, es uno de los mayores retos científicos en el campo de las energías renovables. La obtención de dispositivos que cumplan estas condiciones ha incentivado el desarrollo de nuevos materiales. Las celdas solares de CIGS ostentan el récord absoluto de eficiencia con valores cercanos al 22%. Sin embargo, este compuesto presenta diversas limitaciones que pueden detienen su desarrollo a gran escala, en particular la escasez de dos de sus elementos constituyentes: el In y el Ga. Estas circunstancias han motivado a la comunidad científica internacional a buscar propuestas de nuevos compuestos. En esta búsqueda se han destacado especialmente una familia de compuestos llamados genéricamente Kesterita al ser el nombre de su estructura cristalina. El material por excelencia utilizado como capa buffer en la kesterita y en general en toda la tecnología de celdas solares de segunda generación es el CdS depositado por baño químico (CBD). Pero el elemento Cd, se considera como un compuesto no adecuado para la producción masiva de módulos fotovoltaicos. Es por ello que usar capas buffer libres de Cd es un aspecto que está siendo investigado alrededor del mundo sin embargo, no se ha encontrado un substituto que permita obtener las altas eficiencias que se han logrado con el CdS. El uso de las capas buffer libres de Cd por lo general va acompañado de pasos de activación, tales como un recocido térmico con la combinación del llamado "light soaking", lo cual al final, incrementa el costo de producción. El objetivo fundamental de esta tesis se centra en el estudio sistemático de películas delgadas como capas buffer (CdS y materiales libres de Cd) para tecnologías fotovoltaicas basadas en kesteritas. Se hace especial hincapié en la optimización de los parámetros de crecimiento que influyen en las propiedades de las celdas solares procesadas mediante la realización de diversos estudios de las propiedades ópticas, estructurales, morfológicas y de composición química de las películas depositadas, cuyos resultados se encuentran publicados en diferentes revistas científicas arbitradas. Los aspectos más destacados e innovadores en este trabajo son: estudiar el dopado con Cu del CdS para reducir su espesor, estudiar la influencia del uso de diversas sales precursoras de Cd, el estudio de tratamientos térmicos al CdS para sus propiedades físicas y con ello mejorar las características de los dispositivos procesados y finalmente el estudio de multicapas (incluidas las capas buffer libres de Cd) para entender el comportamiento de estas capas con el material absorbedor.
Wideband pulse amplifiers for the integrated cameras of the Cherenkov Telescope Array
(Universitat de Barcelona, 2016-02-04) Sanuy Charles, Andreu; Gascón Fora, David; Miribel-Català, Pere Ll. (Pere Lluís); Universitat de Barcelona. Departament d'Electrònica
[eng] One type of photon detector is the photomultiplier tube (or PMT), most commonly used in Imaging Atmospheric Cherenkov Telescopes (IACTs). A PMT has a photoelectric cathode that absorbs light and emits an electron. A PMT also contains other electrodes in sequence called dynodes. Each dynode is kept at a higher voltage than the preceding one. Electrons are attracted to each successive dynode, and upon striking the dynode they knock off several additional electrons from the dynode. As the electron stream travels from dynode to dynode, more and more electrons are emitted as a cascade. The pulses generated by the photo sensors (typically PMTs), need to be sampled very fast in order to determine with high precision its arrival time. A typical 2.5 ns width pulse from a PMT needs to be sampled at 800 MHz according to Nyquist theorem, being 1 Gs/s a typical sampling frequency. Considering that an IACT camera can have around 1000 pixels and 8 quantization levels, a continuous recording of the signals from all the pixels in a camera would mean a data rate of 1 TB/s, which is unmanageable. Instead of that, IACTs only records continuously when an interesting event is detected. In order to do that, they uses a data acquisition system based on analogue memories with a complex trigger system. This analogue memories sample the input signals at high sample rate, but with small buffers mounted on a dedicated ring configuration. The NECTAr's (New Electronics for the Cherenkov Telescope Array) front end (FE) option for the camera of the CTA (which is this thesis focused) is a 16 bits and 1— 3 GS/s sampling chip based on analogue memories. The trigger system, analyzes each pulse, and decides if the signal corresponds to a valid Cherenkov event to be stored or not. According to the CTA consortium requirements, the camera specification needs dedicated electronic circuits out of the specifications of the commercial components in the market. Due to cost effective and state of the art innovation, some full custom ASICs have been developed. The aim of this thesis is to develop a full amplification channel path to inject the fast pulses coming from the camera sensors to the analogue memories of the digitizer circuitry. Based on the hard constrains of the amplification channel path for the CTA project, new technologies are applied to cover on one hand, the required wideband at the low noise level and, on the other hand decrease the power consumption required as much as possible. A first amplification stage is based on a wideband current mode preamplifier with 16 bits DR. We propose a novel current mode circuit to overcome the maximum signal limitation by creating multiple gain paths at the very front end of the input stage. The input current is split in the common base input stage into two output scaled currents. Finally, the current signal is converted to voltage by a closed loop transimpedance amplifier. A fully closed loop solution based on voltage feedback amplifiers (OTA or OpAmp) is not feasible because a Gain-bandwidth (GBW) product of more than 8 GHz is required, and the maximum GBW product that can be achieved in a 0.35 [tm CMOS technology is well below 1 GHz. An alternative approach based on linearized high frequency (HF) transconductors is explored for a second amplification stage, which includes dedicated circuitry to adjust the DC offset in order to be properly DC coupled to the NECTArO ADC, and is followed by a high swing current to voltage conversion, and finally a low output impedance closed loop buffer is used to drive a capacitive load.

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