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The biosensing field has grown in importance and research efforts over the last few years for many reasons including point of care sensing devices and possible early detection of diseases in the body. Dopamine sensing is discussed in this paper and the development of a dopamine sensing platform would lead to early detection of diseases linked to its abundance or lack thereof in the brain such as Parkinson's disease. This work focuses on the electrochemical methods of biosensing, specifically dopamine sensing, and this method involves the use of electrodes as its sensing component. Multimaterial electrode-embedded fibers are used as the sensing electrode and the electrode material presented is platinum (Pt). Platinum is employed because of its biocompatibility property. The electrodes are placed in the fiber by the method of convergence fiber drawing and the fiber ends are stripped to expose the electrode for application. To make the proposed sensing platform more cost-effective, the platinum is electrodeposited onto the multimaterial fiber's embedded electrode. We discuss the use of a W/Pt modified electrode and a pure platinum wire in dopamine sensing and demonstrate that Pt is indeed a good candidate for dopamine sensing. The results show that the sensitivity of the W/Pt modified electrode to dopamine is higher than that of a pure Pt wire. This work has shown the promising application of electrodeposition in developing a cheaper flexible biosensing platform and opens up the possibility of the development of wearable flexible smart textile sensors because of the use of flexible multimaterial fibers. / Master of Science / The idea of sensing is important to our world and various scientific developments in this area have improved our way of life as humans. Biological sensing, which is what this thesis focuses on, detects the presence of various substances in the body, and developments in the area of biosensing have led to the creation of devices that can detect diseases or gather general information about a person's anatomical state. There has been increased interest in the detection of dopamine as more studies show that some diseases such as Parkinson's disease are related to the amounts of dopamine present in the brain. In this work, we present a potential platform for sensing dopamine in vitro using electrochemistry. Multimaterial fibers with embedded electrodes capable of measuring dopamine were fabricated using a thermal drawing technique. The electrode material in this fiber is the most important part of the sensing platform as it is what determines how sensitive the fiber is to an analyte. The two main topics discussed in this work are the modification of the electrode material using an electrodeposition technique and the sensing of dopamine with the modified electrode using the electrochemical methods of cyclic voltammetry and differential pulse voltammetry. The material involved in the electrodeposition process is Platinum (Pt) and the results show that platinum is a suitable material for dopamine sensing.

Recent progress in combing multiple materials with distinct optical, electronic, and thermomechanical properties monolithically in a kilometer-long fiber drawn from a preform offers unique multifunctionality at a low cost. A wide range of unique in-fiber devices have been developed in fiber form-factor using this strategy. Here, I summary my recent results in this nascent field of 'multimaterial fibers'. I will focus on my achievements in producing robust infrared optical fibers and in appropriating optical fiber production technology for applications in nanofabrication. The development of optical components suitable for the infrared (IR) is crucial for applications in this spectral range to reach the maturity level of their counterparts in the visible and near-infrared spectral regimes. A critical class of optical components that has yet to be fully developed is that of IR optical fibers. Here I will present several unique approaches that may result in low-cost, robust IR fibers that transmit light from 1.5 microns to 15 microns drawn from multimaterial preforms. These preforms are prepared exploiting the newly developed procedure of multimaterial coextrusion, which provides unprecedented flexibility in material choices and structure engineering in the extruded preform. I will present several different 'generations' of multimaterial extrusion that enable access to a variety of IR fibers. Examples of the IR fibers realized using this methodology include single mode IR fibers, large index-contrast IR fibers, IR imaging fiber bundles, IR photonic crystal and potentially photonic band-gap fibers. The complex structures produced in multimaterial fibers may also be used in the fabrication of micro- and nano-scale spherical particles by exploiting a recently discovered in-fiber Plateau-Rayleigh capillary instability. Such multimaterial structured particles have promising application in drug delivery, optical sensors, and nanobiotechnology. The benefits accrued from the multimaterial fiber methodology allow for the scalable fabrication of micro- and nano-scale particles having complex internal architectures, such as multi-shell particles, Janus-particles, and particles with combined control over the radial and azimuthal structure. Finally, I will summarize my views on the compatibility of a wide range of amorphous and crystalline materials with the traditional thermal fiber drawing process and with the more recent multimaterial fiber strategy.

An understanding of the mechanical properties of viral capsids (protein assemblies forming shell containers) has become necessary as their perceived use as nano-materials for targeted drug delivery. In this thesis, a heterogeneous, spatially detailed model of the viral capsid is considered. This model takes into account the increased degrees of freedom between the capsomers (capsid sub-structures) and the interactions between them to better reflect their deformation properties. A spatially realistic finite element multi-domain decomposition of viral capsid shells is also generated from atomistic PDB (Protein Data Bank) information, and non-linear continuum elastic simulations are performed. These results are compared to homogeneous shell simulation re- sults to bring out the importance of non-homogenous material properties in determining the deformation of the capsid. Finally, multiscale methods in structural analysis are reviewed to study their potential application to the study of nanoindentation of viral capsids. / text

Une méthode est proposée pour la modélisation d’unassemblage multimatériaux innovant visant des applicationsdans l’allègement structurel des véhicules. Dans cetassemblage une partie composite thermoplastique, est fixée àune plaque acier texturée par la technologie CMT pins.L’interface est particulièrement complexe et non linéaire : unereprésentation fine du comportement local serait extrêmementpénalisante en temps de calcul. Dans cette optique il a étéchoisi d’orienter la méthodologie vers une modélisation la plussimple possible tout en conservant de bons résultats globaux.Pour ce faire, en s’inspirant de l’état de l’art existant sur lesmultimatériaux, une campagne expérimentale a été menée surdes éprouvettes longitudinales à double recouvrement afin decaractériser cette interface. Une fois les mécanismes locauxinvestigués, deux modèles sont proposés. Le premiernumérique basé sur la méthode des éléments finis etl’introduction d’éléments cohésifs nous permet de valider leshypothèses de modélisation tout en quantifiant la répartitiondes efforts entre les picots. Le deuxième se base sur le calcullocal d’un Volume Élémentaire Représentatif pour établiranalytiquement la loi de comportement de l’interface. Cette loiest ensuite introduite sous la forme d’un ressort non linéaire ausein d’un modèle numérique simplifié de l’éprouvette. Pourfinir ces approches sont appliquées au cas d’étude industriel etles résultats sont validés par une deuxième campagneexpérimentale. / A method is proposed to simulate an innovative multimaterialassembly which has applications in structural lightweight forvehicles. In this assembly, a thermoplastic composite part isfixed on a steel plate, textured by the CMT pins technology.This is an especially complex and nonlinear interface: a finerepresentation of local behaviour would be extremely costlyfor calculation. So, it has been chosen to investigate a model assimple as possible which still demonstrates accurate globalresults.An experimental campaign on double lap shear specimen,inspired by existing state of the art on multimaterial has beenset up to characterize this interface. Once local mechanismshave been understood, two models are proposed and compared.The first is numerical and based on finite elements method andcohesive elements. It allows us to validate the modelhypotheses while describing the effort repartition between thepins. The second one is based on a Representative VolumeElement. It establishes analytically the behaviour law of theinterface. This law is then inserted inside a simplifiednumerical model of the specimen by means of a nonlinearspring. To conclude, these approaches are applied to theindustrial case of study and the result have been validated by asecond experimental campaign.

The main objective of this Master Thesis project is the development of a new methodology to perform Computational Fluid Dynamics (CFD) conjugate heat transfer simulations for internal combustion engines, at the Fluid and Combustion Simulations Department (NMGD) at Scania CV AB, Södertalje, Sweden. This new method allows to overcome the drawbacks identified in the former methodology, providing the ability to use the more advanced polyhedral mesh type to generate good quality grids in complex geometries like water cooling jackets, and integrating all the different components of the engine cylinder in one unique multi-material mesh. In the method developed, these advantages can be used while optimizing the process to perform the simulations, and obtaining improved accuracy in the temperature field of engine components surrounding the water cooling jacket when compared to the experimental data from Scania CV AB tests rigs. The present work exposes the limitations encountered within the former methodology and presents a theoretical background to explain the physics involved, describing the computational tools and procedures to solve these complex fluid and thermal problems in a practical and cost-effective way, by the use of CFD.A mesh sensitivity analysis performed during this study reveals that a mesh with low y+ values, close to 1 in the water cooling jacket, is needed to obtain an accurate temperature distribution along the cylinder head, as well as to accurately identify boiling regions in the coolant domain. Another advantage of the proposed methodology is that it provides new capabilities like the implementation of thermal contact resistance in periodical contact regions of the engine components, improving the accuracy of the results in terms of temperature profiles of parts like valves, seats and guides. The results from this project are satisfactory, providing a reliable new methodology for multi-material thermal simulations, improving the efficiency of the work to be performed in the NMGD department, with a better use of the available engineering and computational resources, simplifying all the stages of multi-material projects, from the geometry preparation and meshing, to the post-processing tasks.

This thesis deals with research and optimization of process parameters and methodology of production of multimaterial parts manufactured by SLM. This work investigates iron-based and copper-based materials. The aim of the work is to create a good-quality horizontal and vertical multimaterial interface. In the case of the horizontal interface, the optimal process parameters for the processing of selected materials, their subsequent optimization for a goodquality horizontal interface and verification of mechanical properties were experimentally determined. For the vertical interface, it was necessary to design a production methodology and further optimize the process parameters. Finally, some mechanical properties of the interface were determined. However, research of the vertical interface has been a scientific task with some degree of uncertainty, and as this area has not yet been fully explored, it has proved to be a more complex problem than previously thought. It was therefore not possible to completely clarify it in the given time and with the available means. This work provides a detailed description of the mechanisms of creating both types of interfaces and their properties and can serve as a basis for further study of multimaterial 3D printing of metals based on iron and copper.

De nos jours, les politiques environnementales sont devenues plus strictes envers l’industrie automobile pour réduire les émissions de CO2, donc les structures légères utilisant des matériaux de haute résistance sont d’un grand intérêt. Deux modèles différents EF, à savoir "Solid Refine Model" (SRM) et "Shell Coarse Model " (SCM) ont été développés et sont utilisés comme modèles standard par Faurecia Automotive Seating (Caligny). Le SRM est capable de prédire avec précision le comportement de soudage local, mais malheureusement, en raison de son coût de calcul élevé, le SRM n’est pas adapté à une modélisation de si`ge de voiture complète. D’autre part, le SCM est efficace sur le plan numérique, mais il ne peut pas prédire le comportement de la ligne de soudure. L’objectif de la présente thèse est de développer un modèle EF multi-matèriel dans le logiciel commercial Ls-dyna, qui améliorera le SCM pour permettre une prédiction précise du comportement de la ligne de soudure jusqu’à l’échec avec un coût de calcul raisonnable. Le modèle FE quadrilatère standard est développé et enrichie à l’aide d’une méthode récemment développée appelée "Interpolation Covers Method" (ICM) pour capturer les gradients de la solution avec précision sans raffinement de maillage. Un modèle de matériau élasto-plastique est développé dans le logiciel commercial Ls-dyna qui prend en compte deux matériaux différents à savoir BM et HAZ dans un seul élément de coque. Le modèle généralisé d’endommagement dépendant de l’état de contrainte a été implémenté comme UMAT dans le logiciel commercial Ls-dyna pour prédire l’échec de la ligne de soudure dans SCM. Les différents développements ont permis au SCM de prédire avec précision le comportement complexe de la ligne soudée jusqu’à l’échec, à faible coût de calcul compatible avec les besoins industriels. / Nowadays environmental policies have become more strict towards the automotive industry to reduce the CO2 emission, therefore lightweight structures using high strength materials have become of great interest. Two different FE models namely “Solid Refine Model” (SRM) and “Shell Coarse Model” (SCM) have been developed and are being used as standard models by Faurecia Automotive Seating (Caligny). The SRM is capable to predict accurately the local welding behavior but unfortunately, due to its high computational cost, the SRM is not suitable for a full car seat modeling. On the other hand, the SCM is computationally efficient but it cannot predict the weld line behaviour. The aim of the present thesis is to develop a multimaterial FE model within the Ls-dyna commercial software, which will enhance the SCM to allow the accurate prediction of weld line behavior until failure with a reasonable computational cost. The standard quadrilateral shell FE is developed and enriched using a recently developed method called the “Interpolation Covers Method” (ICM) to capture the solution gradients accurately without mesh refinement. An elasto-plastic material model is developed within Ls-dyna commercial software which takes into account two different materials namely BM and HAZ inside a single shell element. The Generalized Incremental Stress State dependent damage Model has been implemented as a UMAT within Ls-dyna commercial software to predict the weld line failure in SCM. The different developments have allowed the SCM to become able to predict the complex behavior of the welded line accurately until failure, at low computational cost compatible with the industrial needs.

The thesis deals with the design, construction and testing of two different metal powder coating equipment, which is able to work with SLM 280HL metal 3D printer. Since the field of multimaterial metal printing by selective laser melting (SLM) has not been significantly investigated yet, an overview of existing patents and possible approaches to the solution has been developed. The device has been successfully designed and a series of tests was carried out defining the issue of applying an improved head that uses a nozzle and an eccentric vibration motor. Based on the experiments performed, the coating parameters of the multimaterial layer of FeAm and 316L materials were defined. A control system for the partial process automation was created for the proposed device. The device was implemented in a printer that demonstrated both the ability to apply a single multimaterial layer of at least 50 m thickness, and the ability to produce a 3D multimaterial component comprised of up to 200 layers and containing material change across all axes.

3D printing technology, which has its origins in rapid prototyping, is increasingly used to build functional devices. Although 3D printing technology has been well developed for thermoplastic polymers and metals, it is still in the research phase for soft polymeric materials such as silicones. Silicones are an industrially vital polymer characterized by a broad spectrum of chemical and physical properties for several smart applications, including on skin printing, smart sensors, multigradient material, and soft actuators. Extrusion-based multimaterial printing is one of the 3D printing techniques that have been adapted due to its compatibility to process silicone-based materials for constructing various functional devices. However, there are several challenges such as achieving on the fly mixing at low Reynolds numbers regime, achieving fast switching while using Newtonian/non-Newtonian inks, and achieving multimaterial printing on nonplanar surfaces. The development of suitable and robust printheads that are able to tackle those challenges can expand the application of this technology to a wide range of fields. In this thesis, several deposition-controlled printhead designs have been created for 3D printing multifunctional devices using an understanding of microfluidics. The established printhead can be controlled to formulate different multigradient structures through on the fly mixing during the material printing. Moreover, the developed printhead can be adapted to print multi viscous inks with high switching rates up to 50 Hz. Through the developed system, the printhead was able to track topologies in real-time, allowing objects to be printed over complex substrates. These new capabilities were applied to fabricate functional structures in order to demonstrate the potential of the developed printhead approaches that can be used in various applications, including smart sensors, soft robotics and multigradient objects. / Thesis / Doctor of Philosophy (PhD) / 3D printing techniques, such as extrusion-based multimaterial printing, have recently been utilized to process silicones due to their versatility in different smart applications, including multigradient material and soft actuators. Although it represents significant progress, there are still several challenges, including the proper mixing during printing with a laminar flow regime, the fast switching between different inks, and the printing over complex topographies. Therefore, various printhead designs have been developed in this thesis to tackle these challenges. In particular, a mixer printhead has been designed to allow mixing during printing for building multigradient objects. Also, a scalable printhead has been developed to allow fast switching for creating pixelated structures. Finally, a simple mechanical system has achieved multimaterial printing over various nonplanar surfaces. To the best of the author's knowledge, the developed printheads can be used in many fields, such as soft robotics and smart devices.