Esta pesquisa foi desenvolvida no laboratório do Centro Internacional de Referência em Reúso de Água (CIRRA), vinculado ao Departamento de Engenharia Hidráulica e Ambiental da Escola Politécnica da Universidade de São Paulo (USP). O projeto de pesquisa teve como objetivo principal a síntese de membranas planas compostas, utilizando o polímero fluoreto de polivinilideno (PVDF), nanopartículas inorgânicas de argila (montmorilonita hidrofílica) e óxido de polietileno (PEO). As membranas foram sintetizadas pelo processo de inversão de fases, utilizando 18% em massa de PVDF, n-metil-pirrolidona como solvente e água como o não solvente. Avaliou-se a influência da introdução de diferentes concentrações de nanopartículas de argila e PEO. As membranas sintetizadas foram submetidas a testes de avaliação de desempenho (permeabilidade, capacidade de separação, potencial de depósitos) e de caracterização (morfologia e características físicas). Os resultados obtidos indicam que a adição de nanopartículas inorgânicas de argila e o formador de poros PEO melhoraram o desempenho e as características físicas das membranas. As membranas Kynar 761 6% argila 0% PEO (K6-0), Kynar 761 0% argila 4% PEO (K0-4) e Kynar 761 6% argila 4% PEO (K6-4) apresentaram as melhores permeabilidades com um aumento, respectivamente, de 520%, 1.250% e 1.100%, em relação à membrana pura. Além disso, observa-se uma melhora de 55%, 60% e 41% na redução do potencial de depósito, respectivamente, para as membranas K6-0, K0-4 e K6-4, quando comparada a membrana de controle. A melhora da permeabilidade e do potencial de depósito das membranas compostas está relacionada à melhoria da hidrofilicidade e da carga superficiail. A morfologia interna das membranas sintetizadas com argila pode ser caracterizada com uma camada superficial com poros conectados verticalmente aos poros em formas de canais da camada intermediária. A camada inferior possui uma morfologia esponjosa com micro-poros. O aumento da quantidade e tamanho dos poros superficiais é proporcional ao aumento da concentração de argila, assim como a diminuição de bloqueios horizontais entre a camada superficial e os poros em formas de canais da camada intermediária. A morfologia interna das membranas sintetizadas com PEO pode ser caracterizada por uma camada superficial densa com poros e uma camada inferior com uma morfologia esponjosa densa com micro-poros. A camada intermediaria tem uma morfologia densa com poros em forma de canais com diâmetros maiores se comprado às membranas sem adição de PEO. A adição de PEO diminui o tamanho médio dos micro-poros, se comparado com as membranas onde apenas argila é adicionada. Foi constatado que a melhoria da permeabilidade está associada à alteração na morfologia interna das membranas compostas. O aumento dos poros superficiais conectados aos poros em forma de canais mais longos e uma camada inferior menor, proporciona uma redução da resistência interna da membrana, devido à formação de caminhos livres, facilitando a passagem da água. Pelas análises de espectrômetro de raios X por dispersão de energia (EDS), foram identificadas nanopartículas de argila dispersas na superfície e na matriz transversal da membrana. Os resultados indicam que a introdução de nanopartículas de argila na solução polimérica é uma técnica de modificação da membrana promissora no melhoramento do desempenho da membrana para o tratamento de água e efluentes. / This research was developed in the International Reference Center for Water Reuse (IRCWR) laboratory inside to the Departamento de Engenharia Hidráulica e Ambiental da Escola Politécnica da Universidade de São Paulo (USP). The main objective of this research is the synthesis of ultrafiltration flat sheet membrane, using polyvinylidene fluoride (PVDF) polymer, clay (montmorillonite hydrophilic) inorganic nanoparticles and polyethylene oxide (PEO). Membranes were synthesized by phase inversion process, using 18% PVDF, mass based, in n-methylpyrrolidone as solvent and water as the non-solvent in the coagulation bath. The influence of different concentrations of clay nanoparticles and PEO was evaluated. Permeability, separation capability, and foulling potential tests were conducted to evaluate membranes performance and morphology analysis and physical characteristics were used for membranes characterization. Results indicated that clay nanoaprticles and PEO addiction can improve membrane permeability and morphology. The Kynar 761 6% clay 0% PEO (K6-0), Kynar 761 0% clay 4% PEO (K0-4) and Kynar 761 6% clay 4% PEO (K6-4) membranes showed the best permeability results, with an increase, respectively of 520%, 1,250% and 1,100%, compared to pure membrane. Furthermore, there is an improvement of 55%, 60% and 41% in the foulling potential reduction, respectively, for K6-0, K0-4 and K6-4 membranes, compared to the control membrane. It was verified that membrane permeability improvement and fouling potential reduction with the addition of clay nanoparticles is related with the improvement of membranes hydrophilicity and surface charge. The internal morphology of the membranes synthesized with clay can be characterized by a surface layer with pores interconnected with finger-like pores in the intermediate layer. The bottom layer has a sponge-like morphology with micro-pores. The increasing number and size of surface pores and also the reduction of horizontal blocks between the surface layer and the finger-like pores in the intermediate layer, is observed with increasing dosage of clay. The internal morphology of the membranes synthesized with PEO can be characterized by a dense surface layer and a bottom layer with dense sponge morphology with micro-pores. The intermediate layer has a dense morphology with finger-like pores with larger diameters if compared to the membranes without addition of PEO. The PEO addition decreases the average size of micro-pores, compared with membranes only clay is added. It was observed that change in composite membranes internal morphology, resulted in the water permeability improvement. The increasing superficial pores connected to longer finger-like pores and a thin bottom layer resulted in an internal pore structure with a lower resistance due to free paths formation, facilitating the flow passage. Using Energy Dispersive X-ray Spectroscopy (EDS) analysis it was possible to observed clay nanoparticles dispersed on membrane surface and in its cross-section matrix. These preliminary results indicate that clay nanoclay addiction in polymeric solution is a promising membrane modification technique for improving membrane performance for water and wastewater treatment.

Foi estudada a enxertia de estireno induzida por radiação gama em filmes de poli(fluoreto de vinilideno) (PVDF) com espessura de 0,125 mm com doses entre 1 e 100 kGy em presença de soluções de estireno/N,Ndimetilformamida (DMF) (1:1, v/v) e estireno/tolueno (1:1, v/v) com taxa de dose de 5 kGy.h-1 por meio do método simultâneo de irradiação sob atmosfera de nitrogênio e em temperatura ambiente, usando raios gama de uma fonte de Co- 60. Depois de enxertados, os polímeros foram sulfonados em soluções de ácido clorossulfônico/1,2-dicloroetano (2 e 10 %). Os filmes foram caracterizados antes e depois de cada modificação com o cálculo do Grau de enxertia, (DOG), espectrometria no infravermelho (FT-IR), microscopia eletrônica de varredura (MEV), calorimetria exploratória diferencial (DSC) e termogravimetria (TG/DTG). Os resultados do grau de enxertia mostraram que a enxertia aumenta com o aumento da dose e varia enormemente de acordo com o solvente utilizado, com enxertias cerca de 20 vezes maiores quando do uso da DMF em relação ao do tolueno. Foi possível confirmar a enxertia do estireno por FT-IR graças ao aparecimento de novos picos característicos e por TG/DTG e DSC por meio das alterações do comportamento térmico dos materiais enxertados/sulfonados. Os materiais sulfonados ainda foram caracterizados por suas capacidades de troca iônica (IEC), que mostraram que tanto os aumentos do grau de enxertia quanto os da concentração do ácido clorossulfônico aumentam o IEC. Os resultados mostraram que é possível obter materiais com capacidades de troca iônica com possibilidade de aplicação como compósitos ionoméricos de metal-polímero. / Gamma-radiation-induced grafting of styrene into poly(vinylidene fluoride) (PVDF) films with 0.125 mm thickness at doses from 1 to 100 kGy in the presence of a styrene/N,N- dimethylformamide (DMF) solution (1:1, v/v) and styrene/toluene (1:1, v/v) at dose rate of 5 kGy h-1 was carried out by simultaneous method under nitrogen atmosphere at room temperature, using gamma rays from a Co-60. After grafting reactions, the polymer was then sulfonated in chlorosulfonic acid/1,2-dichloroethane (2 and 10%) for 3 hours. The films were characterized before and after modification by calculating the degree of grafting (DOG), infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetry (TG/DTG). DOG results show that grafting increases with dose, and varies enormously depending on the solvent used, with DOGs about 20 times greater in DMF than in toluene. It was possible to confirm the grafting of styrene by FT-IR due to the appearance of the new characteristic peaks and by the TG and DSC which exhibited changes in the thermal behavior of the grafted/sulfonated material. Sulfonated material was also characterized by ion exchange capacity (IEC) showed that both DOG and sulfonic acid concentration increase IEC values. Results showed that it is possible to obtain materials with ion exchange capacity of possible application as ionic polymer-metal composites.

Ce travail porte sur la modification de matrices polymères à base de fluorure de vinylidene pour permettre leur utilisation en tant que membrane séparatrice dans les supercapacités. Basé sur un procédé d'irradiation par rayonnement γ, l'objectif principal était la limitation du gonflement du polymère lorsqu'il est mis en contact d'un milieu liquide relatif à l'application tout en gardant d'excellentes affinités avec celui-ci. Le processus de base exploité étant la formation et la réaction des radicaux lors de l'irradiation du polymère, une partie de la thèse a été consacrée à leur étude par résonance paramagnétique électronique (RPE). Un modèle de simulation de spectre RPE a été mis en place pour identifier et quantifier chacune des espèces radicalaires. L'effet de la dose d'irradiation, de la durée d'un recuit et de la nature de la matrice polymère (homo, copolymère) sur la proportion de ces espèces et sur leur réactivité a été évalué. Un lien avec la formation d'un réseau a été proposé. Une attention particulière a ensuite été apportée à l'augmentation de la densité de réticulation avec le concours d'un agent réticulant, le TAIC. Pour terminer, une stratégie de modification des propriétés de surface du PVDF a été élaborée. Elle consiste dans un premier temps à radiogreffer un polymère à la surface du PVDF puis à modifier, dans un second temps, les greffons par une chimie douce et sélective. En conclusion, les approches complémentaires développées au cours de cette thèse ont permis de comprendre la radiolyse des polymères et de mettre à profit les processus élémentaires pour développer des stratégies robustes et prometteuses de modulation des propriétés.

Ce travail a eu pour objectif la création de matériaux composites à base de nanocharges de carbonate de calcium. L'étude des phénomènes interfaciaux qui régissent ces systèmes, ainsi que leurs impacts sur les propriétés fonctionnelles du matériau et plus particulièrement des propriétés de transport, ont été réalisées. Pour ce faire, nous avons considéré deux matrices polymères de nature chimique différente : le polylactide et le polyfluore de vinylidène. Les nanocomposites ont été élaborés par deux voies de mise en œuvre : la voie fondu et la voix solvant. Une analyse fine des relations structure/morphologie/propriétés des composites a été réalisée. Nous avons mis en évidence, quelle que soit la matrice polymère choisie, l'importance du traitement de surface des charges afin d'améliorer leurs états de dispersion dans le matériau et d'augmenter la qualité de l'interface charge/polymère. Ces paramètres ont été corrélés aux propriétés de transport de ces matériaux composites. / The aim of this PhD work is to elaborate composites based on calcium carbonate nanoparticles. Polylactide and polyvinylidene fluoride were used as polymer matrix and nanocomposite were elaborated either by melting process and either by casting method. The interfacial behaviour between polymer and calcium carbonate were studied and we especially focused on their impact on the composite gas barrier properties. The importance of filler surface treatment had been highlighted on the filler dispersion state improvment and filler/polymer interface reinforcement. Both parameters were important in the improvement of composite gas barrier properties.

No description available.

<p>    An all-additive manufacturing technique was developed to print piezoelectrically active polymeric materials, primarily poly(vinylidene fluoride) (PVdF), for use in pressure sensors in soft robotics. The research proceeded in three stages. The initial stage used Fused Deposition Modeling (FDM) and electric poling independently to create piezoelectric PVdF pressure sensors. The second stage merged FDM and electric poling processes. The third stage introduced electrospinning to create flexible, high-output piezoelectric PVdF materials, which were combined with three-dimensional (3D) printed soft structures for stretchable pressure sensors.</p> <p>    The main achievement of the research was the development of the Electric Poling-assisted Additive Manufacturing (EPAM) technique, combining electric poling and FDM 3D printing to print piezoelectric materials with custom structures at lower costs. β-phase in semicrystalline PVdF materials is mainly responsible for piezoelectricity. A higher β-phase content results in superior sensor performance. This technique was evaluated by measuring the piezoelectric output voltage of the printed PVdF films, and β-phase content was quantified using Fourier-transform Infrared spectroscopy (FTIR). The developed EPAM technique was combined with Direct Ink Writing (DIW), becoming a hybrid 3D printing technique. This is the first demonstration of applying a hybrid printing technique to print piezoelectric PVdF-based sensors directly. The sensor was constructed using FDM printed PVdF film as the dielectric sandwiched between two parallel DIW printed silver electrodes. The PVdF sensors have both piezoelectric pressure sensing and capacitive temperature sensing functionalities. The application of the capacitive temperature sensor was demonstrated by applying heating-and-cooling cycles while measuring the capacitance as a function of temperature at a constant frequency, showing improved sensitivities at higher frequencies (i.e., 105 Hz) after dielectric polarization.</p> <p>    The third stage of research was motivated by the need for soft piezoelectric pressure sensors for soft robotics. Challenges were twofold: requiring soft piezoelectric materials with high coefficients for excellent sensors and fabrication techniques to incorporate soft materials into designed structures. Inspired by the EPAM technique, a method combining electrospinning and DIW was used to create soft piezoelectric PVdF/thermal plastic polyurethane (TPU) blend microfiber-based pressure sensors. The soft sensor was integrated with an FDM printed soft structure for a stretchable pressure sensor with both piezoelectric sensing and capacitive sensing mechanisms.</p>

Tesis por compendio / [ES] El aumento de la esperanza de vida conlleva la aparición de problemas muscoloesqueléticos afectando a la calidad de vida de los pacientes. Las nuevas terapias regenerativas óseas se centran en el uso de las células madre mesenquimales, MSCs, encargadas de la regeneración del tejido in vivo. La inducción de un fenotipo osteogénico prediferenciado in vitro, previo a la implantación de las MSCs, resulta en una mejor capacidad de regeneración del tejido óseo. Habitualmente se han empleado medios de diferenciación osteogénica que contienen dexametasona. Estos métodos son poco eficientes, por lo que el uso de métodos físicos está adquiriendo relevancia. El hueso es un tejido con propiedades piezoeléctricas debido a las fibras de colágeno que forman parte de su matriz extracelular. Este estímulo ha sido relacionado con su capacidad de responder al estrés mecánico y autoregenerarse, donde juegan un papel importante las MSCs. Éstas se encuentran en un entorno electroactivo, y son precisamente estas señales físicas las que pueden influir en su proceso de diferenciación osteogénica pudiendo ser empleadas para su prediferenciación in vitro de forma efectiva. Para comprobar esta hipótesis, en la presente Tesis Doctoral se han diseñado soportes de cultivo piezoeléctricos en 2 y 3 dimensiones basados en el uso del polímero piezoeléctrico polifluoruro de vinilideno (PVDF) combinados con partículas magnetostrictivas de ferrita de cobalto (CFO). Esta combinación permite la estimulación de los soportes de cultivo aplicando un campo magnético con un biorreactor. Este campo magnético genera la deformación del componente magnetostrictivo, que es transmitida a la matriz polimérica, deformándola y generando un campo eléctrico. Ésta última es transmitida a las células cultivadas en estos soportes para estudiar su efecto sobre la diferenciación osteogénica. En el primer capítulo se desarrollaron y caracterizaron membranas electroactivas de PVDF fabricadas por el método de separación de fases inducida por no-solventes. Se empleó etanol como no-solvente, dando lugar a membranas homogéneas altamente porosas. Estas cristalizan en fase g. Se optimizó un recubrimiento basado en la técnica capa a capa (LbL), empleando recombinámeros similares a la elastina (ELRs) que contenían secuencias de adhesión celular RGD. Se estudió la respuesta celular inicial de las MSCs y se comparó con los mismos soportes recubiertos únicamente con fibronectina adsorbida. La presencia de los ELRs es necesaria para promover la adhesión inicial de las MSCs en este tipo de soportes. En el segundo capítulo se combinó el PVDF con CFO, usando agua como no-solvente. Las membranas eran no simétricas, con una superficie lisa, que fue empleada para cultivo celular, con una mayoría en fase b, la más electroactiva. Se recubrieron y caracterizaron las membranas mediante LbL con colágeno tipo I y heparina. Se estudió el comportamiento de las MSCs sobre el LbL, resultando esencial para la proliferación celular en el caso de las membranas PVDF-CFO. En el capítulo tres se desarrollaron films de PVDF y PVDF-CFO cristalizados en presencia del líquido iónico [Bmim][Cl]. La presencia de éste indujo la nucleación del PVDF en fase b. Las MSCs eran capaces de adherirse y proliferar. Se realizaron ensayos de estimulación piezoeléctrica empleando un biorreactor magnético. Las MSCs respondieron a la estimulación incrementado la longitud de sus adhesiones focales, así como reduciendo la vimentina en el citoplasma. Finalmente, se diseñaron soportes de cultivo piezoeléctricos en 3D. Para ello se desarrollaron microesferas de PVDF y PVDF-CFO mediante la técnica de electropulverizado. Las microesferas se encapsularon en hidrogeles de gelatina junto con las MSCs. Se estimularon y tras 7 días, se observó un incremento en la expresión del factor de transcripción RUNX2 en las muestras estimuladas demostrando que la estimulación piezoeléctrica es capaz de activar en mayor medida la diferenciación de las MSCs. / [CA] L'augment de l'esperança de vida comporta l'aparició de problemes muscoloesquelètics afectant la qualitat de vida dels pacients. Les noves teràpies regeneratives òssies es centren en l'ús de les cèl·lules mare mesenquimals, MSCs, encarregades de la regeneració del teixit in vivo. La inducció d'un fenotip osteogènic prediferenciat in vitro, previ a la implantació de les MSCs, resulta en una millor capacitat de regeneració del teixit ossi. Habitualment s'han fet servir mitjans de diferenciació osteogènica que contenen dexametasona. Aquests mètodes són poc eficients, per la qual cosa l'ús de mètodes físics està adquirint rellevància. L'os és un teixit amb propietats piezoelèctriques a causa de les fibres de col·lagen que formen part de la seva matriu extracel·lular. Aquest estímul ha estat relacionat amb la capacitat de respondre a l'estrès mecànic i autoregenerar-se, on juguen un paper important les MSCs. Aquestes es troben en un entorn electroactiu, i són precisament aquests senyals físics els que poden influir en el seu procés de diferenciació osteogènica podent ser emprats per a la seva prediferenciació in vitro de manera efectiva. Per comprovar aquesta hipòtesi, a la present tesi doctoral s'han dissenyat suports de cultiu piezoelèctrics en 2 i 3 dimensions basats en l'ús del polímer piezoelèctric polifluorur de vinilidè (PVDF) combinats amb partícules magnetostrictives de ferrita de cobalt (CFO). Aquesta combinació permet l'estimulació dels suports de cultiu aplicant un camp magnètic amb un bioreactor. Aquest camp magnètic genera la deformació del component magnetostrictiu, que és transmesa a la matriu polimèrica, deformant-la i generant un camp elèctric. Aquesta última és transmesa a les cèl·lules cultivades en aquests suports per estudiar-ne l'efecte sobre la diferenciació osteogènica. En el primer capítol es van desenvolupar i caracteritzar membranes electroactives de PVDF fabricades pel mètode de separació de fases induïda per no solvents. Es va emprar etanol com a no-solvent, donant lloc a membranes homogènies altament poroses. Aquestes cristal·litzen en fase g. S'optimitzà un recobriment basat en la tècnica capa a capa (LbL), emprant recombinàmers similars a l'elastina (ELRs) que contenien seqüències d'adhesió cel·lular RGD. Es va estudiar la resposta cel·lular inicial de les MSCs i es va comparar amb els mateixos suports recoberts únicament amb fibronectina adsorbida. La presència dels ELR és necessària per promoure l'adhesió inicial de les MSCs en aquest tipus de suports. En el segon capítol es va combinar el PVDF amb CFO, usant aigua com a no-solvent. Les membranes eren no simètriques, amb una superfície llisa, que va ser emprada per a cultiu cel·lular, amb una majoria en fase b, la més electroactiva. Es van recobrir i caracteritzar les membranes mitjançant LbL amb col·lagen tipus I i heparina. Es va estudiar el comportament de les MSCs sobre el LbL, resultant essencial per a la proliferació cel·lular en el cas de les membranes PVDF-CFO. Al capítol tres es van desenvolupar films de PVDF i PVDF-CFO cristal·litzats en presència del líquid iònic [Bmim][Cl]. La seva presència va induir la nucleació del PVDF en fase b. Les MSCs eren capaces d'adherir-se i proliferar. Es van realitzar assajos d'estimulació piezoelèctrica emprant un bioreactor magnètic. Les MSCs van respondre a l'estimulació incrementant la longitud de les seves adhesions focals, així com reduint la vimentina al citoplasma. Finalment, es van dissenyar suports de cultiu piezoelèctrics en 3D. Per això es van desenvolupar microesferes de PVDF i PVDF-CFO mitjançant la tècnica d'electropolveritzat. Les microesferes es van encapsular en hidrogels de gelatina juntament amb les MSCs. Es van estimular i després de 7 dies, es va observar un increment en l'expressió del factor de transcripció RUNX2 a les mostres estimulades demostrant que l'estimulació piezoelèctrica és capaç d'activar més la diferenciació de les MSCs. / [EN] Life expectancy increase entails the presence of musculoskeletal disorders producing a substantial impact on patient's quality of life. New bone regenerative therapies are focused on the use of mesenchymal stem cells (MSCs), the main effectors of bone regeneration in vivo. Over the years, it has been demonstrated that the induction of a pre-differentiated phenotype in vitro, before MSCs implantation, results in a better capacity for bone tissue regeneration. For this purpose, biochemical approaches based on the use of osteogenic differentiation medium containing dexamethasone have traditionally been used. These methods are not efficient, which has favoured the use of physical methods as an alternative. Bone is a piezoelectric tissue due to the collagen fibres that conform its extracellular matrix. This stimulus has been related to its ability to respond to mechanical stress and self-regenerate, a process in which MSCs play a key role. MSCs are subjected to an electroactive environment. It is hypothesised that these physical signals may influence their osteogenic differentiation process and be used to effectively pre-differentiate them in vitro. To test this hypothesis, along this Doctoral Thesis, piezoelectric cell culture supports have been designed in 2 and 3 dimensions based on the use of the piezoelectric polymer poly(vinylidene) fluoride (PVDF) combined with magnetostrictive cobalt ferrite oxide (CFO) nanoparticles. This combination allows the stimulation of culture supports by applying a magnetic field with a bioreactor. This magnetic field induces the deformation of the magnetostrictive component, which is transmitted to the polymeric matrix, generating a deformation and producing an electric field, which is transmitted to the MSCs to study its effect on their osteogenic differentiation. In the first chapter, electroactive PVDF membranes manufactured by the non-solvent induced phase separation technique were developed and characterised. Ethanol was used as a non-solvent, which gave rise to highly porous homogeneous membranes crystallised in the g phase. A coating protocol based on the layer-by-layer (LbL) technique, using elastin-like recombinamers (ELRs) containing RGD cell adhesion sequences, was optimised. MSCs' initial cellular response was studied and compared with the membranes coated with adsorbed fibronectin. The presence of the ELRs was necessary to promote MSCs' initial adhesion in this type of support. In the second chapter, PVDF was combined with CFO, using water as a non-solvent. The membranes were not symmetrical, with a smooth surface used for cell culture, with a majority in phase b, the most electroactive. Membranes were coated and characterised by LbL with type I collagen and heparin. The behaviour of MSCs on LbL was studied, essential for cell proliferation in the case of PVDF-CFO membranes. In chapter three, PVDF and PVDF-CFO films crystallised in the presence of the ionic liquid [Bmim][Cl] were developed. The presence of ionic liquid induced PVDF nucleation in the b phase. MSCs were able to adhere and proliferate. Piezoelectric stimulation tests were performed using a magnetic bioreactor. MSCs responded to stimulation by increasing the length of their focal adhesions and reducing vimentin in the cytoplasm. Finally, 3D piezoelectric culture supports were designed. For this, PVDF and PVDF-CFO microspheres were developed using the electrospray technique. The microspheres were encapsulated in gelatin hydrogels together with the MSCs. They were stimulated, and after 7 days, an increase in the expression of the transcription factor RUNX2 was observed in the stimulated samples, demonstrating that piezoelectric stimulation is capable of activating the differentiation of MSCs to a greater extent. / La presente tesis doctoral no podría haberse realizado sin la financiación del Ministerio de Economía y Competitividad a través de la beca para formación de personal investigador BES-2017-080398 y a la Agencia Estatal de Investigación a través de los proyectos PID2019-106000RB-C21 / AEI / 10.13039/501100011033, PID2019-106099RB- C41 y –C43 / AEI / 10.13039/501100011033. / Guillot Ferriols, MT. (2022). Electroactive Environments for Mesenchymal Stem Cells Osteogenic Differentiation [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/191003 / Compendio

Este trabalho descreve a seqüência de fabricação de uma microválvula piezoelétrica posicionada na saída de um microbocal sônico. A técnica usada para fabricar os microbocais foi o jateamento utilizando pó de alumina e o substrato usado foi de vidro. As microválvulas são atuadores fabricados com o polímero poli(fluoreto de vinilideno) (PVDF) que é um material piezoelétrico. Os microbocais têm um formato convergente-divergente com diâmetro na entrada de 1 mm e com diâmetro na garganta em cerca de 240 microns. O atuador foi fabricado no modo bimorfo (duas folhas do polímero coladas com polarização opostas) com dimensões de 3 mm de largura por 6 mm de comprimento. Ambas as folhas do polímero são recobertas por um filme condutor de 200 nm de espessura usados como eletrodos. Aplicando uma voltagem entre os eletrodos uma folha expande enquanto a outra contrai gerando um movimento vertical do atuador. O movimento vertical pode ser maior ou menor dependendo do valor da tensão aplicada. Os dispositivos foram testados usando uma linha de gás, aplicando tensões DC e AC nos eletrodos do atuador. Para controle, também foram realizadas medidas em bocais sem atuadores. No caso onde foram aplicadas tensões DC nos atuadores, a pressão de entrada foi constante de 266 Pa. Aplicando uma tensão de +300 V DC nos eletrodos, o atuador teve um movimento vertical na direção oposta ao do microbocal de 20 microns (movimento de abertura). Neste caso o fluxo de gás medido, quando a razão de pressão entre a entrada e a saída atingiu 0,5, foi de 150 cm3/min. Aplicando uma tensão de -300 V DC (o que significa um movimento vertical de fechamento de 13 microns), o fluxo de gás medido, quando a razão de pressão foi de 0,5, foi de 134 cm3/min. Assim, existe uma faixa de fluxo entre 134 cm3/min e 150 cm3/min que pode ser controlada através do atuador. Em uma das medidas onde se aplicou uma tensão AC (200 V com 5 Hz de freqüência), foi utilizada uma pressão de entrada 13300 Pa. Neste caso, para uma razão de pressão de 0,5, onde o bocal se encontrava blocado, foi observado um fluxo de 847 cm3/min. Considerando que o fluxo do bocal sem atuador, nas mesmas condições de medida foi de 614 cm3/min, concluímos que o dispositivo no modo AC funciona como uma microbomba. A relevância deste trabalho está a utilização do poli(fluoreto vinilideno) (PVDF) na fabricação de um atuador para uso como microválvula. Este material que ainda não havia sido testado para esta finalidade. A fabricação dos microbocais foi feita em um substrato de vidro usando a técnica de jateamento também é inédita. Esta técnica é bastante usada na fabricação de microestruturas na superfície do vidro. Mas nunca tinha sido usada para a fabricação de microbocais que são canais em formato cônico que atravessam o substrato. / This work describes the fabrication and test of a microvalve integrated in a micronozzle. The technique used to fabricate the micronozzles was powder blasting using aluminum oxide powder and glass as substrate. The microvalves are actuators made from PVDF (poli(vinylidene fluoride)), that is a piezoelectric polymer. The micronozzles have convergent-divergent shape with diameter of 1mm at the entrance and throat around 240µm. The actuators were fabricated as a bimorph structure (two piezoelectric sheets were clamped together with opposite polarization) with dimensions 3 mm width and 6 mm length. Both sheets are recovered with a conductive thin film with 200 nm of thickness used as electrodes. Applying voltage between the electrodes one sheet expands while the other contracts and this generate a vertical movement to the entire actuator. If the voltage is changed, this movement can be higher or lower. The devices were tested in a gas line applying DC and AC voltages between the actuator\'s electrodes. Measurements were also realized using a micronozzle without actuator, for control. In the case where DC voltage was applied between the actuators electrodes, the inlet pressure was kept constant in 266 Pa. Applying +300V DC voltage between the electrodes, the actuator moved 20µm vertically in the opposite direction of the micronozzle (it opened). In this case the volume flux rate, for a pressure ratio (outlet / inlet) of 0.5, was 150 cm3/min. Applying -300V DC between the electrodes (that means it closed 13 microns in the micronozzle direction), for a pressure ratio of 0.5, the volume flux rate was 134 cm3/min. With these results, we conclude that it is possible to control the flow through the device in the range between 134 and 150 cm3/min. Flow measurements were also performed applying AC voltage (200V AC with frequency of 5 Hz) between the actuator electrodes and with the inlet pressure kept constant in 13300 Pa. In this case, with a pressure ratio (outlet / inlet) of 0.5, blocking the micronozzle, the flow rate measured was 847 cm3/min. Considering that the flow rate measured for the micronozzle without actuator was 614 cm3/min, in the same measurement conditions, we concluded that the device, in AC mode, was working as a micropump. The relevance of this work was the use of the poly(vinylidene) (PVDF) in the fabrication of the actuators and use it as a microvalve. The micronozzles were fabricated in a glass substrate using the powder blasting technique that was also new.

This thesis reports the theoretical investigations aimed at understanding the structure, stability and properties of a few inorganic compounds. The first chapter presents an introductory overview of the theories used to solve the questions addressed in the thesis. A brief discussion of the work is also presented here. The second chapter deals with electron reservoirs which have been one of the basic motifs of single-electron device. Mononuclear vinylidene complexes of type Mn(C5H4R’)(R” 2 PCH2CH2PR "2)= C = C(R1)(H) were synthesized and reported [Venkatesan et al, Organometallics 25, 5190 (2006)] as potential electron reservoirs capable of storing and releasing electrons in a reversible fashion. These compounds have been of great interest because their red-ox chemistry (reversible oxidative coupling and reductive decoupling) is governed by the C - C bond. However slow oxidation of the mononuclear vinylidene complexes leads to undesired product. In our model compound Mn(C5H5)(PH3)2 = C = C(R1)(H), we substituted the cyclopentadienyl moiety by isolobal dianionic dicarbollyl ligand Dcab2- (C2B9H2-11 ). This simple substitution could reduce the production of undesired product. Calculations of vertical detachment energy, thermodynamic feasibility and molecular orbital analysis showed that this substitution was thermodynamically feasible and led to easy oxidation and dimerization of the parent compound accompanied with better reversibility of the reaction. The effect of substituents (R = H,Me,Ph) on Cβ atom of our model system was also analyzed. The substituent on β carbon had a great effect on the stability and reactivity of these complexes. Our comparative study between Mn(C5H5)(PH3)2 = C = C(R)(H) and Mn(Dcab)(PH3)2 = C = C(R)(H)−1 (where R = H,Me,Ph) predicted the latter to be a more potential electronic reservoir. Gas-phase observations on MAl 4- (M = Li, Na, Cu) and Li3Al-4 coupled with computations led to the conclusion that Al42− [Boldyrev and Wang et al, Science 291, 859 (2001)] is “aromatic” while Al44- is “antiaromatic” [Boldyrev and Wang et al, Science 300, 522 (2003)]. It has been reported by Pati et al [J. Am. Chem. Soc. 125, 3496 (2005)] that co-ordination with a transition metal can stabilize the “antiaromatic” Al4Li4. In the first section of chapter three, it has been reported that Al4Li4 can also be stabilized by capping it with main group element like C and its isoelectronic species BH. Calculations of binding energy, nuclear independent chemical shift (NICS), energy decomposition analysis and molecular orbital analysis supported the capping induced stability, reduction of bond length alternation and increase of aromaticity of these BH/C capped Al4Li4 systems. The interaction between px and py orbitals of BH/C and the HOMO and LUMO of Al4Li4 was responsible for such stabilization. Calculations suggested that capping might introduce fluxionality in the molecule at room temperature. Al has valence electronic configuration of s2p1 and Al42− has been shown to have multiple aromaticity [Boldyrev and Wang et al, Science 291, 859 (2001)]. Analogy between electronic configuration s2pof Al and d1sof Sc/Y prompted us to explore the aromaticity of M42− clusters (M = Sc, Y ) which have been described in the second section of chapter three. Different geometries of M42− clusters (M = Sc, Y ) were explored, and the planar butterfly-like D2h geometry (two fused triangles) was found to be the most stable isomer. This is unlike the case of Al42− where D4h isomer was the most stable one as reported in the literature. In D2h geometry of M42− clusters (M = Sc, Y ), significant electron delocalization in each wing of the butterfly indicated fused d aromaticity. Atomization energy and chemical hardness supported the preference of D2h geometry over the D4h geometry. Molecular orbital analysis showed that the d-electrons were delocalized in each triangle of D2h geometry. Our interest in the search of new kinds of binuclear sandwich compounds led us to consider sandwiched metal dimers CB5H6M - MCB5H6 (M = Si, Ge, Sn) which are at the minima in the potential energy hypersurface with a characteristic M - M single bond. This work has been described in the first section of chapter four. The NBO analysis and the M - M distances ( ˚A) (2.3, 2.44 and 2.81 for M= Si, Ge, Sn respectively) indicated substantial M - M bonding. Consecutive substitution of two boron atoms in B7H7−2 by M (Si, Ge, Sn) and carbon respectively led to neutral MCB5H7, where M - H bond bent towards the carbon side of the five membered ring. Dehydrogenation of two MCB5H7 might lead to our desired CB5H6M - MCB5H6 where similar bending of M -M bond has been observed. The bending of M - M bond in CB5H6M -MCB5H6 was more than the M - H bending in MCB5H7. Molecular orbital analysis has been done to understand the bending. Larger M - M bending observed in CB5H6M - MCB5H6 in comparison to M - H bending observed in MCB5H7 was suspected to be favored by stabilization of one of the M - M π bonding MO’s. Preference of M to occupy the apex of pentagonal skeleton of MCB5H7 over its icosahedral analogue MCB10H11 has been observed. Structures of sandwiched binuclear L- M – M - L where M = Ti, Zr and L = Cp, C3B3H6 were also investigated as described in second section of chapter four. We found that these compounds having bent geometry with short M - M distance (1.87˚A for M=Ti and 2.29˚A for M=Zr) lie at the minima in the potential energy hypersurface. Bending from the linear geometry led to the stabilization of M - L antibonding interaction in L - M – M - L. Molecular orbital analysis, NBO calculations, Wiberg bond index and charge analysis suggested M2+ unit to be embedded in between two L’s in L - M – M - L. Molecules that have the ability to perform interesting mechanical motions have always been of great interest. Umbrella inversion of ammonia is one of the most interesting and well studied phenomena. This study has led to the development of the MASER. The possibility of inversion of the molecule C9H9−Li+ by the movement of Li+ through the C9H9−ring was studied earlier [Das et al, Chem. Phys. Lett. 365, 320 (2002)]. In the fifth chapter theoretical investigation on a B12 cluster has been reported, which could exhibit a through ring umbrella inversion. Calculations showed that a part of the molecule, consisting of a three membered boron ring could invert through the rest, viz., a nine membered boron ring. Using a simple model, the double well potential for the motion was calculated. The barrier for inversion was found to be 4.31 kcal/mol. The vibrational levels and tunneling splitting were calculated using this potential. It was found that the vibrational excitation to the v = 17 level caused large amplitude “inversion oscillation” of the molecule. After considering the tunneling effect, inversion rate at 298K was calculated by using transition state theory and was found to be 1.17 x 1010/s. Finally, in the last chapter the main results of the thesis have been summarized.

Este trabalho descreve a seqüência de fabricação de uma microválvula piezoelétrica posicionada na saída de um microbocal sônico. A técnica usada para fabricar os microbocais foi o jateamento utilizando pó de alumina e o substrato usado foi de vidro. As microválvulas são atuadores fabricados com o polímero poli(fluoreto de vinilideno) (PVDF) que é um material piezoelétrico. Os microbocais têm um formato convergente-divergente com diâmetro na entrada de 1 mm e com diâmetro na garganta em cerca de 240 microns. O atuador foi fabricado no modo bimorfo (duas folhas do polímero coladas com polarização opostas) com dimensões de 3 mm de largura por 6 mm de comprimento. Ambas as folhas do polímero são recobertas por um filme condutor de 200 nm de espessura usados como eletrodos. Aplicando uma voltagem entre os eletrodos uma folha expande enquanto a outra contrai gerando um movimento vertical do atuador. O movimento vertical pode ser maior ou menor dependendo do valor da tensão aplicada. Os dispositivos foram testados usando uma linha de gás, aplicando tensões DC e AC nos eletrodos do atuador. Para controle, também foram realizadas medidas em bocais sem atuadores. No caso onde foram aplicadas tensões DC nos atuadores, a pressão de entrada foi constante de 266 Pa. Aplicando uma tensão de +300 V DC nos eletrodos, o atuador teve um movimento vertical na direção oposta ao do microbocal de 20 microns (movimento de abertura). Neste caso o fluxo de gás medido, quando a razão de pressão entre a entrada e a saída atingiu 0,5, foi de 150 cm3/min. Aplicando uma tensão de -300 V DC (o que significa um movimento vertical de fechamento de 13 microns), o fluxo de gás medido, quando a razão de pressão foi de 0,5, foi de 134 cm3/min. Assim, existe uma faixa de fluxo entre 134 cm3/min e 150 cm3/min que pode ser controlada através do atuador. Em uma das medidas onde se aplicou uma tensão AC (200 V com 5 Hz de freqüência), foi utilizada uma pressão de entrada 13300 Pa. Neste caso, para uma razão de pressão de 0,5, onde o bocal se encontrava blocado, foi observado um fluxo de 847 cm3/min. Considerando que o fluxo do bocal sem atuador, nas mesmas condições de medida foi de 614 cm3/min, concluímos que o dispositivo no modo AC funciona como uma microbomba. A relevância deste trabalho está a utilização do poli(fluoreto vinilideno) (PVDF) na fabricação de um atuador para uso como microválvula. Este material que ainda não havia sido testado para esta finalidade. A fabricação dos microbocais foi feita em um substrato de vidro usando a técnica de jateamento também é inédita. Esta técnica é bastante usada na fabricação de microestruturas na superfície do vidro. Mas nunca tinha sido usada para a fabricação de microbocais que são canais em formato cônico que atravessam o substrato. / This work describes the fabrication and test of a microvalve integrated in a micronozzle. The technique used to fabricate the micronozzles was powder blasting using aluminum oxide powder and glass as substrate. The microvalves are actuators made from PVDF (poli(vinylidene fluoride)), that is a piezoelectric polymer. The micronozzles have convergent-divergent shape with diameter of 1mm at the entrance and throat around 240µm. The actuators were fabricated as a bimorph structure (two piezoelectric sheets were clamped together with opposite polarization) with dimensions 3 mm width and 6 mm length. Both sheets are recovered with a conductive thin film with 200 nm of thickness used as electrodes. Applying voltage between the electrodes one sheet expands while the other contracts and this generate a vertical movement to the entire actuator. If the voltage is changed, this movement can be higher or lower. The devices were tested in a gas line applying DC and AC voltages between the actuator\'s electrodes. Measurements were also realized using a micronozzle without actuator, for control. In the case where DC voltage was applied between the actuators electrodes, the inlet pressure was kept constant in 266 Pa. Applying +300V DC voltage between the electrodes, the actuator moved 20µm vertically in the opposite direction of the micronozzle (it opened). In this case the volume flux rate, for a pressure ratio (outlet / inlet) of 0.5, was 150 cm3/min. Applying -300V DC between the electrodes (that means it closed 13 microns in the micronozzle direction), for a pressure ratio of 0.5, the volume flux rate was 134 cm3/min. With these results, we conclude that it is possible to control the flow through the device in the range between 134 and 150 cm3/min. Flow measurements were also performed applying AC voltage (200V AC with frequency of 5 Hz) between the actuator electrodes and with the inlet pressure kept constant in 13300 Pa. In this case, with a pressure ratio (outlet / inlet) of 0.5, blocking the micronozzle, the flow rate measured was 847 cm3/min. Considering that the flow rate measured for the micronozzle without actuator was 614 cm3/min, in the same measurement conditions, we concluded that the device, in AC mode, was working as a micropump. The relevance of this work was the use of the poly(vinylidene) (PVDF) in the fabrication of the actuators and use it as a microvalve. The micronozzles were fabricated in a glass substrate using the powder blasting technique that was also new.