The work focused on addressing four main objectives. The first objective was to quantify protein and amino acid substitution reactions. Michael addition reactions were used to modify the amino acids and protein. Amino acids alanine, cysteine, and lysine, and protein ovalbumin (OA) were substituted with different concentrations of ethyl vinyl sulfone (EVS). The substituted products were analyzed using Raman spectroscopy and UV-spectroscopy based ninhydrin assay. In case of alanine, Raman and UV results correlated with each other. With cysteine at lower EVS substitutions amine on the main chain was the preferred site while the substitution shifted to thiols at higher substitutions. This could only be discerned using Raman spectroscopy. Lysine has amines on the main chain and side chain while main chain amine was the most reactive site at lower concentrations of EVS while at higher concentrations side chain amines were also substituted. This information could be discerned using Raman spectroscopy only and not UV spectroscopy. In case of protein as observed by Raman and UV spectroscopy the reaction continued at higher concentrations of EVS indicating the participation of glutamine and asparagines at higher substitutions. However, the reaction considerably slowed down at higher EVS substitutions. The second objective of the study was to decrease the glass transition temperature (Tg) of OA through internal plasticization and also study the effects of the substituents on the thermal stability of OA. The hypothesis was by covalently attaching substituents to OA, number of hydrogen bonds can be reduced while increasing the free volume and this would reduce Tg. EVS, acrylic acid (AA), butadiene sulfone (BS) and maleimide (MA) were the four groups used. EVS was the most efficient plasticizer of all the four substituents. The Tg decreased with the increasing concentration of EVS until all of the reactive of groups on OA were used up. Tg decreased slightly with AA and BS while no change was observed with MA. However, the substituents showed exact opposite trend in thermal stability as measured using thermogravimetric analysis (TGA). The thermal stability of MA substituted OA was the highest and that of EVS substituted OA was least. FT-IR spectroscopy results indicated that all four substituents caused structural changes in OA. This implied that there were intermolecular interactions between substituted protein chains in case of AA, BS, and MA. This caused an increase in the thermal stability. EVS on the other hand is a linear chain monomer with a hydrophobic end group and hence could not participate in the intermolecular interactions and hence caused a decrease in Tg. As mentioned above the limitation to this technique is the number of available reactive groups on the protein. However, we successfully demonstrated the feasibility of this method in decreasing Tg of protein. The third objective was to create hydrogels by crosslinking OA with divinyl sulfone (DVS). Protein hydrogels due to their biocompatible nature find applications in drug delivery and tissue engineering. For tissue engineering applications the hydrogels need to be mechanically stable. In this study the protein was substituted with EVS or AA and then crosslinked with DVS. The swelling ratio was measured as a function of pH. All the hydrogels showed the same trend and swelled the least at pH 4.5 which is the isoelectric point of the protein. At basic pH conditions EVS substituted hydrogels swelled the most while AA substituted hydrogels showed least swelling. The static and dynamic moduli of the hydrogels were determined using tensile tester and rheometer respectively. The static modulus values were three times the dynamic modulus. The modulus of the control which is crosslinked OA was least and that of AA substituted OA was highest. The stress relaxation test also showed similar results in which AA substituted OA relaxed the most and the control relaxed the least. FT-IR of the dry hydrogels showed that the amount of hydrogen bonding increased with AA substitution. The hydrophilic AA end groups interacted with each other forming hydrogen bonds. These hydrogen bonds served as additional crosslinks there by increasing the modulus of the hydrogels. EVS on the other hand was incapable of interactions due to the lack of hydrophilic end groups. We were successfully able to create protein hydrogels and control the swelling and mechanical properties by varying the amount of substituted group. The final objective of the study was to create and characterize microstructures from substituted alanine and lysine. Alanine and lysine were substituted with different concentrations of EVS. Bars and fibers were observed for alanine at moderate substitutions while at higher concentrations random structures were observed using scanning electron microscopy (SEM). Lysine formed tubes at moderate EVS substitutions and rosettes at high concentrations of EVS as evidenced by SEM. FT-IR results suggested that instead of carbonyl one of sulfonyl bonded to the available amine in modified amino acids. And only in this case fibers, tubes and rosettes were observed. X-ray diffraction (XRD) results supported this observation. Using these results we hypothesized that the self assembled structures very much depended on the amount of EVS present in the substituted product and sulfonyl forming β-sheet analogs with amine. / Ph. D.

Dispositivos de reação miniaturizados tendem a ganhar espaço na indústria de processos químicos por elevarem o transporte de massa e de calor e a segurança dos processos. Para compreender o papel de cada elemento constituinte de um microrreator sobre seu campo de velocidades e fenômenos de mistura, foram simulados um conjunto de dois canais, uma junção em T, 30 canais em formato de serpentina e um microchip completo através da fluidodinâmica computacional. A seção transversal destes microdispositivos têm dimensões entre 100 e 300 µm, enquanto o comprimento dos canais varia de 3000 a 25190 µm. Os modelos computacionais foram discretizados por malhas hexaédricas e os campos de velocidade em estado estacionário foram calculados para vazões de alimentação entre 12,5 e 2000 µL min-1, considerando regime laminar. A mistura foi avaliada pela injeção de traçadores não-reativos e distribuição das respectivas frações mássicas. As simulações foram validadas usando microvelocimetria por imagens de partículas. Os campos de velocidade possuem magnitudes significativas apesar das dimensões reduzidas e baixas vazões de operação dos sistemas. As imagens experimentais do escoamento evidenciaram o formato parabólico do campo de velocidades e o deslocamento de seu ponto máximo nas regiões curvas causado pela força centrífuga, como estimado pelo modelo computacional. Tal força, em conjunto com as forças viscosas na parede, gera fluxos secundários no escoamento. A distribuição de traçadores não-reativos evidenciou a importância dos fluxos secundários para promover mistura na direção ortogonal ao escoamento principal, ocorrendo sob o regime estacionário nas vazões analisadas. O estudo aqui realizado evidencia o emprego da fluidodinâmica computacional como ferramenta para melhor compreensão da fluidodinâmica e como apoio ao projeto de microdispositivos. / Miniaturized reaction vessels are drawing attention of chemical industries because they promote better mass and heat transfer and also enhance process safety. To understand the relevance of each element of a microreactor on the velocity field of the equipment and the corresponding mixing processes, several microdevices were simulated using computational fluid dynamics: an assembly of two channels, a T-junction, 30 channels in a serpentine assembly and a full microreactor. The cross section of the devices is 100 - 300 µm wide and the length of the channels varies between 3000 and 25190 µm. Computational domains were discretized using hexahedral meshes and steady-state velocity fields were computed considering laminar flow for flow rates between 12,5 and 2000 µL min-1. Mixing was evaluated by injecting inert tracers and monitoring their distribution. Simulations were validated against experimental micro particle image velocimetry data. Velocities throughout the devices are relatively high despite the small dimensions of the cross sections and small flow rates. Experimental images of the flow elucidated the parabolic shape of the velocity profile and its distortion on curved segments caused by centrifugal forces, matching predictions of the computational model. Tracer maps indicated secondary flows play an important role in mixing stream perpendicular to the main flow direction. This study emphasizes the use of computational fluid dynamics as a tool for understating flow throughout microdevices and supporting their design.

A thin polymer bilayer film was transformed into micro- and nano-tubes using strain driven self-rolling phenomena of polystyrene (PS)/poly (4-vinyl pyridine) (P4VP) film. Polymer bilayer was produced by consecutive deposition of PS and P4VP, from toluene and chloroform solutions, respectively, by dip-coating technique. The object formation proceeds from a opening in the film made by photolithography or by mechanical scratching followed by immersion of patterned sample in dodecylbenzene sulfonic acid (DBSA) solution. DBSA forms supramolecular complexes with pyridine rings of P4VP and increases the specific volume of the polymer. Since the solution is neutral to PS layer, bilayer film develops strain due to unequal swelling of polymers in solution of DBSA and hence the film bends and scrolls in order to minimize its free energy and form tubes. The length of the tubes and the direction of rolling are determined by mechanical patterning of the film. UV-photolithography is used to fabricate patterns of polymer bilayer in order to create tube in a precise manner. The kinetics of the tube formation was studied with respect to acidity of the solution and UV dose. Rate of rolling increased with the acidity of the solution. Tube diameter and rate of rolling decreased with the increase of the UV exposure time. Films with 2-dimensional gradients of layer thicknesses were prepared to study a broad range of parameters in a single experiment. Furthermore, polymer micro-toroids and triangles were also fabricated using self-rolling approach of PS/P4VP layer. Moreover, the kinetics of toroid formation is also studied in the present work. The equilibrium dimensions of toroid are determined by the balance of the bending and the stretching energies of the film. The width of the rolled-up bilayer is larger for the films with higher values of the bending modulus and smaller values of the effective stretching modulus. Moreover, self-rolling phenomena of polymer layer was also explored as a template to fabricate metal, ceramic and metal/ceramic hybrid tube. In order to fabricate metallic and V bimetallic tube, the cross-linked polymer film is capped by metallic layer. After rolling, polymer template is removed by pyrolysis resulting in pure metal microtubes. The fabrication of silica and silica/gold hybrid tubes of high aspect ratio is also demonstrated. Polydimethylsiloxane (PDMS) is used as a precursor of the silica and it is converted into silica by pyrolysis at high temperature. Entire polymer moiety is also removed at this temperature. In order to fabricate hybrid tube of silica with gold, a thin gold layer is deposited on the polymer layer by physical vapour deposition. Self-rolling of polymer bilayers is a very convenient approach for interfacing the interior of microtubes with external electrical circuits and it can be used in particular for creating devices as micro-bubble generators exploiting electrolytic decomposition of fluids. A demonstration of microbubble generation inside the polymer tube is shown in this work. Possibility to functionalize the hidden walls of the tubes is one of the major advantages of the self-rolling approach. One can modify the surface of the film prior to rolling by magnetron sputtering of metal and upon rolling, tube and toroids with metallized inner surface could be obtained. The tube and toroids with metallic inner surface are promising for the future research as IR-frequency range resonators. Polymer and metallic microtubes fabricated by self-rolling approach may find applications in such fields as IR-waveguiding, microfluidics, enzyme bi-reaction, chemical and biochemical sensing. The silica and silica/gold hybrid tubes have potential use in optoelectronic devices and in catalytic applications.

This thesis describes a highly interdisciplinary approach to discern the differing impact of scaffold dimensionality and physical space restrictions on the behavior of single cells. Rolled-up nanotechnology is employed to fabricate three-dimensional (3D) SiO/SiO2 microtube geometries of varied diameter, that after a biofunctionalization step are shown to support the growth of U2OS and six different types of stem cells. Cell confinement quantifiable through the given microtube diameter is tolerated by U2OS cells through a remarkable elongation of the cell body and nucleus down to a certain threshold, while the integrity of the DNA is maintained. This confinement for NSPCs also leads to the approaching of the in vivo morphology, underlining the space-restrictive property of live tissue. The dimensionality of the cell culture scaffold however is identified as the major determiner of NSPC migration characteristics and leads to a morphologically distinct mesenchymal to amoeboid migration mode transition. The 3D microtube migration is characterized by exclusively filopodia protrusion formation, a higher dependence on actin polymerization and adopts aspects of in vivo-reported saltatory movement. The reported findings contribute to the determination of biomaterial scaffold design principles and advance our current understanding of how physical properties of the extracellular environment affect cell migration characteristics.

Dispositivos de reação miniaturizados tendem a ganhar espaço na indústria de processos químicos por elevarem o transporte de massa e de calor e a segurança dos processos. Para compreender o papel de cada elemento constituinte de um microrreator sobre seu campo de velocidades e fenômenos de mistura, foram simulados um conjunto de dois canais, uma junção em T, 30 canais em formato de serpentina e um microchip completo através da fluidodinâmica computacional. A seção transversal destes microdispositivos têm dimensões entre 100 e 300 µm, enquanto o comprimento dos canais varia de 3000 a 25190 µm. Os modelos computacionais foram discretizados por malhas hexaédricas e os campos de velocidade em estado estacionário foram calculados para vazões de alimentação entre 12,5 e 2000 µL min-1, considerando regime laminar. A mistura foi avaliada pela injeção de traçadores não-reativos e distribuição das respectivas frações mássicas. As simulações foram validadas usando microvelocimetria por imagens de partículas. Os campos de velocidade possuem magnitudes significativas apesar das dimensões reduzidas e baixas vazões de operação dos sistemas. As imagens experimentais do escoamento evidenciaram o formato parabólico do campo de velocidades e o deslocamento de seu ponto máximo nas regiões curvas causado pela força centrífuga, como estimado pelo modelo computacional. Tal força, em conjunto com as forças viscosas na parede, gera fluxos secundários no escoamento. A distribuição de traçadores não-reativos evidenciou a importância dos fluxos secundários para promover mistura na direção ortogonal ao escoamento principal, ocorrendo sob o regime estacionário nas vazões analisadas. O estudo aqui realizado evidencia o emprego da fluidodinâmica computacional como ferramenta para melhor compreensão da fluidodinâmica e como apoio ao projeto de microdispositivos. / Miniaturized reaction vessels are drawing attention of chemical industries because they promote better mass and heat transfer and also enhance process safety. To understand the relevance of each element of a microreactor on the velocity field of the equipment and the corresponding mixing processes, several microdevices were simulated using computational fluid dynamics: an assembly of two channels, a T-junction, 30 channels in a serpentine assembly and a full microreactor. The cross section of the devices is 100 - 300 µm wide and the length of the channels varies between 3000 and 25190 µm. Computational domains were discretized using hexahedral meshes and steady-state velocity fields were computed considering laminar flow for flow rates between 12,5 and 2000 µL min-1. Mixing was evaluated by injecting inert tracers and monitoring their distribution. Simulations were validated against experimental micro particle image velocimetry data. Velocities throughout the devices are relatively high despite the small dimensions of the cross sections and small flow rates. Experimental images of the flow elucidated the parabolic shape of the velocity profile and its distortion on curved segments caused by centrifugal forces, matching predictions of the computational model. Tracer maps indicated secondary flows play an important role in mixing stream perpendicular to the main flow direction. This study emphasizes the use of computational fluid dynamics as a tool for understating flow throughout microdevices and supporting their design.

The combination of strain engineering, lithography, thin film deposition and etching techniques is an elegant approach to create single microtubes and well-defined arrays of magnetic microtubes. In this work we have successfully shown that strain engineering techniques developed for rolled-up nanomembranes can be applied to magnetic materials and material combinations. To obtain sufficiently strained nanomembranes, different substrates and sacrificial layers in combination with the magnetic layers were used. Careful tuning of the etching parameters ensured a controlled roll-up process without damage or oxidation of the magnetic layer. Additionally, rolled-up nanomembranes were further integrated in a highly parallel fashion on chip, by development and application of multi-step fabrication procedures. Based on the prepared rolled-up magnetic structures and their planar counterparts we have performed a comprehensive study of their magnetic properties, mainly under the influence of magnetic field, strain and temperature. The role of the special cylindrical or curved geometry and their impact on the magnetic properties was outlined and explained based on our understanding. Moreover, the magnetic properties were also discussed in relationship to other influencing material parameters, e.g. composition, crystallographic structure, and surface effects. The first experimental magnetization study on rolled-up InGaAs/Fe3Si heterostructures was presented. It was demonstrated for tube arrays that the change in the geometry from a planar film to the cylindrical shape has a significant effect on the magnetization behavior. A deeper study provided insight into the magnetic switching behavior of single tubes and arrays. Rolled-up Au/Co/Au tubes and showed that in addition to shape anisotropy, magnetostrictive anisotropy due to the anisotropic stress release can inverse the magnetization direction. Exchange coupling at ferromagnetic/antiferromagnetic interfaces due to partial oxidation of Co was observed at low temperatures. The results suggest possibilities to tune magnetic properties by controlling the tube dimensions and careful control of thin film growth parameters. The cylindrical shape, the layer thickness the number of rotations and the type of magnetic material are proven to have a strong influence on the magnetic domain patterns and magnetization behavior. Therefore, Ni/Fe tubes have been studied by means of magneto optical Kerr effect. It was found that the magnetization reversal in rolled-up tubes with 1.2 and 2.5 windings occurs via nucleation and propagation of magnetic domain walls. On the other hand, we have demonstrated for rolled-up Au/Co tubes that a certain magnetic layer thickness is required to observe magnetic stripe domains. In another experiment performed with magnetic force microscopy, rolled-up Co/Pt nanomembranes with magnetic domains radially aligned due to perpendicular anisotropy, which behaves as radially polarized cylindrical magnets, were achieved. Moreover, we have demonstrated an elegant approach to create compact MR devices based on rolled-up Co/Cu-ML nanomembranes. We have shown the magnetization behavior and the MR magnitude in comparison to the corresponding planar structures. The influence of number of Co/Cu bilayers, non-magnetic spacer layer, interface roughness and multiple windings on MR was discussed. Our fabrication method can be applied to the most common magnetic materials. Certainly, further optimization of MR towards application as magnetic sensor or magneto-fluidic sensors can be achieved by change of Co/Cu-layer thickness, increase of rolling length and reduced spacer layer thickness. Finally, we have shown a fabrication route to realize freestanding tubes based on Ni-Mn-Ga alloys grown by molecular beam epitaxy on GaAs substrates. The evolution of structural and magnetic properties induced by roll-up was investigated in detail and showed a pronounced influence of crystallographic orientation and strain state of the Ni-Mn-Ga alloys. These insights are fundamental in order to realize thin nanomembranes and freestanding three-dimensional FSMA structures with defined composition for smart applications as compact actuators and microsensors. Consequently, rolled-up magnetic nanomembranes offer a great chance in reducing the size of electronic components and can bring several functionalities to the device. These facts make rolled-up tubes highly attractive for the detection, stimulation and manipulation of small objects, such as ions, molecules, cells and particles. It is expected in the future, that magnetic lab-in-a-tube systems will further account in analysis of microfluidic systems. On the other hand, rolled-up structures significantly contribute to the field of shapeable magnetoelectronics.

A thin polymer bilayer film was transformed into micro- and nano-tubes using strain driven self-rolling phenomena of polystyrene (PS)/poly (4-vinyl pyridine) (P4VP) film. Polymer bilayer was produced by consecutive deposition of PS and P4VP, from toluene and chloroform solutions, respectively, by dip-coating technique. The object formation proceeds from a opening in the film made by photolithography or by mechanical scratching followed by immersion of patterned sample in dodecylbenzene sulfonic acid (DBSA) solution. DBSA forms supramolecular complexes with pyridine rings of P4VP and increases the specific volume of the polymer. Since the solution is neutral to PS layer, bilayer film develops strain due to unequal swelling of polymers in solution of DBSA and hence the film bends and scrolls in order to minimize its free energy and form tubes. The length of the tubes and the direction of rolling are determined by mechanical patterning of the film. UV-photolithography is used to fabricate patterns of polymer bilayer in order to create tube in a precise manner. The kinetics of the tube formation was studied with respect to acidity of the solution and UV dose. Rate of rolling increased with the acidity of the solution. Tube diameter and rate of rolling decreased with the increase of the UV exposure time. Films with 2-dimensional gradients of layer thicknesses were prepared to study a broad range of parameters in a single experiment. Furthermore, polymer micro-toroids and triangles were also fabricated using self-rolling approach of PS/P4VP layer. Moreover, the kinetics of toroid formation is also studied in the present work. The equilibrium dimensions of toroid are determined by the balance of the bending and the stretching energies of the film. The width of the rolled-up bilayer is larger for the films with higher values of the bending modulus and smaller values of the effective stretching modulus. Moreover, self-rolling phenomena of polymer layer was also explored as a template to fabricate metal, ceramic and metal/ceramic hybrid tube. In order to fabricate metallic and V bimetallic tube, the cross-linked polymer film is capped by metallic layer. After rolling, polymer template is removed by pyrolysis resulting in pure metal microtubes. The fabrication of silica and silica/gold hybrid tubes of high aspect ratio is also demonstrated. Polydimethylsiloxane (PDMS) is used as a precursor of the silica and it is converted into silica by pyrolysis at high temperature. Entire polymer moiety is also removed at this temperature. In order to fabricate hybrid tube of silica with gold, a thin gold layer is deposited on the polymer layer by physical vapour deposition. Self-rolling of polymer bilayers is a very convenient approach for interfacing the interior of microtubes with external electrical circuits and it can be used in particular for creating devices as micro-bubble generators exploiting electrolytic decomposition of fluids. A demonstration of microbubble generation inside the polymer tube is shown in this work. Possibility to functionalize the hidden walls of the tubes is one of the major advantages of the self-rolling approach. One can modify the surface of the film prior to rolling by magnetron sputtering of metal and upon rolling, tube and toroids with metallized inner surface could be obtained. The tube and toroids with metallic inner surface are promising for the future research as IR-frequency range resonators. Polymer and metallic microtubes fabricated by self-rolling approach may find applications in such fields as IR-waveguiding, microfluidics, enzyme bi-reaction, chemical and biochemical sensing. The silica and silica/gold hybrid tubes have potential use in optoelectronic devices and in catalytic applications.

L'étude ici développée traite de deux aspects de la microfluidique : l'hydrodynamique d'écoulements liquides en microtubes et l'ébullition convective en minicanaux. Le dispositif et la méthode de traitement développés dans la première partie du mémoire permettent d'obtenir le nombre de Poiseuille d'écoulements laminaires liquides avec une précision inférieure à 4%. L'étude met en évidence une croissance du nombre de Poiseuille pour les écoulements d'eau distillée, d'eau de ville et des solutions de KCl au sein de microtubes en silice de diamètres allant de 540 à 52 µm. L'origine des écarts à la théorie classique en macroconduites a été recherchée. Une des hypothèses vraisemblable est l'effet de la Double Couche Electrique due aux ions contenus dans le fluide et à la surface interne du microtube chargée électrostatiquement. Dans la seconde partie du manuscrit, nous mettons en évidence l'influence du confinement pariétal sur un écoulement avec changement de phase liquide-vapeur au sein d'un minicanal vertical. Deux régimes d'ébullition sont observés : stationnaire avec des structures d'écoulements classiques et instationnaires dues à une production importante de vapeur. Dans ce dernier cas, nous distinguons les fluctuations de couplage et les fluctuations intrinsèques à l'écoulement confiné. Un critère de déclenchement des instationarités permet d'accéder à une grandeur adimensionnelle. Une loi d'échelle est alors proposée pour les écoulements diphasiques dans les minicanaux. Il en est de même pour les transferts thermiques.

Orientador: Prof. Dr. José Antonio Souza / Tese (doutorado) - Universidade Federal do ABC, Programa de Pós-Graduação em Nanociências e Materiais Avançados, Santo André, 2018. / O objetivo deste trabalho e sintetizar materiais magneticos e semicondutores ocos micro/nanoestruturados hierarquicamente, para obter um melhor entendimento das propriedades fisicas e explorar aplicacoes tecnologicas. Inicialmente, microtubos de hematita e magnetita foram sintetizados por oxidacao termica juntamente com uma corrente eletrica aplicada e utilizando-se o microfio de ferro metalico como precursor. A fraccao volumetrica de Fe2O3(hematite) e Fe3O4(magnetite) nos microtubos e a formacao das nanoestruturas de hematite na superficie pode ser controlada por alteracoes sistematicas dos parametros de sintese tais como temperatura, rampa de aquecimento, tempo de aquecimento e valor da corrente electrica. A reacao quimica de oxidacao envolve um processo onde uma fina camada de oxido e formada primeiro na superficie do metal, seguida por difusao simultanea de ions metalicos atraves da camada oxida e difusao de oxigenio da atmosfera para o interior. A difusao para fora e mais rapida, levando a criacao de vacancias que coalescem em poros formando os microtubos. Medidas de resistividade eletrica in situ foram realizadas durante o processo de oxidacao mostrando todo o processo de formacao do microtubo. Imagens de microscopia eletronica de varredura mostram a morfologia do microtubo com diametro variando de 40 ¿Êm a 100 ¿Êm e comprimento de 5 mm. Medidas de difracao de raios-X em po evidenciam a presenca de fases cristalinas de hematita (Fe2O3) e magnetita (Fe3O4) nos microtubos. Nanoestruturas de hematita aparecem em forma de bastoes e fios dispersos homogeneamente ao redor da superficie do microtubo com diametros de 80-300 nm e comprimento de 1-5 ¿Êm. Experimentos in vitro envolvendo aderencia, migracao e proliferacao de culturas de celulas de fibroblastos na superficie dos microtubos indicaram a ausencia de citotoxicidade para este material. Tambem o calculo do torque e da forca magnetica desses microtubos com nanofios em funcao do gradiente de campo magnetico externo, mostrou que ele e robusto, abrindo a possibilidade para fabricacao de bio-microrobos magneticos para aplicacao em biotecnologia. Por outro lado, microarquiteturas ocas de SnS e ZnS decoradas com nanoestruturas foram sintetizadas por evaporacao termica livre de catalisadores utilizando microfios de metal e po de enxofre como materiais de partida. Para o SnS, observamos formacao de uma estrutura oca composta por uma camada metalica de Sn na superficie interna, e uma camada de SnS de estrutura ortorrombica com nanoestruturas de SnS na superficie. Para o ZnS, descobrimos a formacao de uma esfera oca com uma camada metalica na parte interna, uma camada de ZnS com fase cubica, e sobre ela nanoestruturas de ZnS com fase cristalina hexagonal cresceram homogeneamente. O diametro da microsfera e de 415 ¿Êm e os nanofios tem um diametro e comprimento medio de 70 nm e 7 ¿Êm, respectivamente. As microestruturas ocas semicondutoras de ZnS e SnS exibiram atividade eficiente para degradar azul de metileno sob irradiao com luz solar simulada. Os resultados revelam que essas nano/microestruturas possuem alta fotoatividade para degradacao organica. / The aim of this work is to synthesize hierarchically micro/nanostructured hollow magnetic and semiconductor materials, to obtain a better understanding on the physical properties, and find technological applications. Initially, hematite and magnetite microtubes were synthesized by thermal oxidation process along with the presence of an applied electrical current and using metallic iron microwire as a precursor. The volume fraction of both Fe2O3 (hematite) and Fe3O4 (magnetite) phase on microtubes can be controlled as well as surface nanostructures formation of hematite by systematic change of the synthesis parameters such as temperature, heating rate, annealing time and electrical current value. The oxidation chemical reaction involves a process where a thin oxide layer is formed first on the metal surface, followed by simultaneous outward diffusion of metal ions through the oxide scale and inward diffusion of oxygen from the atmosphere into the core. In our case, the outward diffusion is faster leading to the creation of vacancies which coalesce into voids forming the microtubes. In situ electrical resistivity measurements were carried out during the oxidation process showing the whole process of the microtube formation. Scanning electron microscopy images show microtube morphology with diameter ranging from 40 ìm to 100 ìm and length of 5 mm. X-ray powder diffraction measurements evidence the presence of hematite (Fe2O3) and magnetite (Fe3O4) crystal phases comprising microtubes. Nanostructures of hematite appear in form of sticks and wires homogeneously dispersed on the microtube surface with diameters ranking from 80 nm to 300 nm and length of 1 to 5 ìm. In vitro experiments involving adherence, migration, and proliferation of fibroblasts cell culture on the surface of the microtubes indicated the absence of immediate cytotoxicity for this material. We have also calculated both torque and driving magnetic force for these microtubes with nanowires as a function of external magnetic field gradient which were found to be robust opening the possibility for magnetic bio micro-robot device fabrication and application in biotechnology. On the other hand, SnS and ZnS hollow microarchitectures decorated with nanostructures were synthesized by catalysis free thermal evaporation technique using metal microwires and sulfur powder as starting materials. For SnS, we observed a hollow formation comprised of a thin metallic Sn layer in the inner surface, SnS orthorhombic structure thick layer with SnS nanostructures on the top. For ZnS, we found out the formation of hollow sphere with a thin metallic layer in the inner part, a thick cubic phase layer of ZnS, and on this second phase, nanostructures of ZnS hexagonal crystal phase grew up homogeneously. The microsphere diameter is about 415 ìm and the nanowires on the surface have average diameter of 70 nm and length 7 ìm. ZnS and SnS hollow semiconducting microstructures have exhibited efficient activity to degrade the methylene blue under simulated sunlight irradiation. The results reveal that these nano/microstructures have high photoactivity to organic degradation.

This thesis describes a highly interdisciplinary approach to discern the differing impact of scaffold dimensionality and physical space restrictions on the behavior of single cells. Rolled-up nanotechnology is employed to fabricate three-dimensional (3D) SiO/SiO2 microtube geometries of varied diameter, that after a biofunctionalization step are shown to support the growth of U2OS and six different types of stem cells. Cell confinement quantifiable through the given microtube diameter is tolerated by U2OS cells through a remarkable elongation of the cell body and nucleus down to a certain threshold, while the integrity of the DNA is maintained. This confinement for NSPCs also leads to the approaching of the in vivo morphology, underlining the space-restrictive property of live tissue. The dimensionality of the cell culture scaffold however is identified as the major determiner of NSPC migration characteristics and leads to a morphologically distinct mesenchymal to amoeboid migration mode transition. The 3D microtube migration is characterized by exclusively filopodia protrusion formation, a higher dependence on actin polymerization and adopts aspects of in vivo-reported saltatory movement. The reported findings contribute to the determination of biomaterial scaffold design principles and advance our current understanding of how physical properties of the extracellular environment affect cell migration characteristics.