275 research outputs found

    Microfluidic systems based on electroactive polymers technology

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    Dielectric elastomer actuators (DEAs) have been widely investigated for more than 30 years. Lately, several fabrication methods have successfully allowed the creation of very thin elastomer and electrode layers. The development of attractive applications, in which DEAs offer advantages over conventional technologies, is thus necessary for the advance of the technology. In this work, new biocompatible microfluidic devices based on DEAs are developed. In the first part of this thesis, several prototypes of peristaltic pumps of single layer dielectric elastomer actuators are designed, manufactured and characterized. Although these prototypes were not able to produce fluid flow, novel insights into the capabilities of Electroactive Polymer technology were gained. In the second part of this work, a pumping micromixer as a novel application of dielectric elastomer stacked actuators is manufactured. The pumping micromixer is based on peristaltic movements, which gently act as a mixer and a pump for microfluidics. Experimental data show a maximal flow rate of 21.5 µL/min at 10 Hz. Image analysis at the outlet proves a 50/50 mixing when all actuators are functioning at the same pace and voltage. The performance of the pumping micromixer is further studied with the Finite Element Method, using the COMSOL Multiphysics® software. Simulations demonstrate the versatility of the pumping characteristics of such a microdevice, from very few µL/min to mL/min, and from a very low pressure in the range of Pa to hundreds of kPa, by only changing the duty cycle, phase shift and actuation frequency

    Applied Mathematics to Mechanisms and Machines

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    This book brings together all 16 articles published in the Special Issue "Applied Mathematics to Mechanisms and Machines" of the MDPI Mathematics journal, in the section “Engineering Mathematics”. The subject matter covered by these works is varied, but they all have mechanisms as the object of study and mathematics as the basis of the methodology used. In fact, the synthesis, design and optimization of mechanisms, robotics, automotives, maintenance 4.0, machine vibrations, control, biomechanics and medical devices are among the topics covered in this book. This volume may be of interest to all who work in the field of mechanism and machine science and we hope that it will contribute to the development of both mechanical engineering and applied mathematics

    Mars delivery service - development of the electro-mechanical systems of the Sample Fetch Rover for the Mars Sample Return Campaign

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    This thesis describes the development of the Sample Fetch Rover (SFR), studied for Mars Sample Return (MSR), an international campaign carried out in cooperation between the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA). The focus of this document is the design of the electro-mechanical systems of the rover. After placing this work into the general context of robotic planetary exploration and summarising the state of the art for what concerns Mars rovers, the architecture of the Mars Sample Return Campaign is presented. A complete overview of the current SFR architecture is provided, touching upon all the main subsystems of the spacecraft. For each area, it is discussed what are the design drivers, the chosen solutions and whether they use heritage technology (in particular from the ExoMars Rover) or new developments. This research focuses on two topics of particular interest, due to their relevance for the mission and the novelty of their design: locomotion and sample acquisition, which are discussed in depth. The early SFR locomotion concepts are summarised, covering the initial trade-offs and discarded designs for higher traverse performance. Once a consolidated architecture was reached, the locomotion subsystem was developed further, defining the details of the suspension, actuators, deployment mechanisms and wheels. This technology is presented here in detail, including some key analysis and test results that support the design and demonstrate how it responds to the mission requirements. Another major electro-mechanical system developed as part of this work is the one dedicated to sample tube acquisition. The concept of operations of this machinery was defined to be robust against the unknown conditions that characterise the mission. The design process led to a highly automated robotic system which is described here in its main components: vision system, robotic arm and tube storage

    Chapter 34 - Biocompatibility of nanocellulose: Emerging biomedical applications

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    Nanocellulose already proved to be a highly relevant material for biomedical applications, ensued by its outstanding mechanical properties and, more importantly, its biocompatibility. Nevertheless, despite their previous intensive research, a notable number of emerging applications are still being developed. Interestingly, this drive is not solely based on the nanocellulose features, but also heavily dependent on sustainability. The three core nanocelluloses encompass cellulose nanocrystals (CNCs), cellulose nanofibrils (CNFs), and bacterial nanocellulose (BNC). All these different types of nanocellulose display highly interesting biomedical properties per se, after modification and when used in composite formulations. Novel applications that use nanocellulose includewell-known areas, namely, wound dressings, implants, indwelling medical devices, scaffolds, and novel printed scaffolds. Their cytotoxicity and biocompatibility using recent methodologies are thoroughly analyzed to reinforce their near future applicability. By analyzing the pristine core nanocellulose, none display cytotoxicity. However, CNF has the highest potential to fail long-term biocompatibility since it tends to trigger inflammation. On the other hand, neverdried BNC displays a remarkable biocompatibility. Despite this, all nanocelluloses clearly represent a flag bearer of future superior biomaterials, being elite materials in the urgent replacement of our petrochemical dependence

    Applications of Finite Element Modeling for Mechanical and Mechatronic Systems

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    Modern engineering practice requires advanced numerical modeling because, among other things, it reduces the costs associated with prototyping or predicting the occurrence of potentially dangerous situations during operation in certain defined conditions. Thus far, different methods have been used to implement the real structure into the numerical version. The most popular uses have been variations of the finite element method (FEM). The aim of this Special Issue has been to familiarize the reader with the latest applications of the FEM for the modeling and analysis of diverse mechanical problems. Authors are encouraged to provide a concise description of the specific application or a potential application of the Special Issue

    Annals of Scientific Society for Assembly, Handling and Industrial Robotics 2021

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    This Open Access proceedings presents a good overview of the current research landscape of assembly, handling and industrial robotics. The objective of MHI Colloquium is the successful networking at both academic and management level. Thereby, the colloquium focuses an academic exchange at a high level in order to distribute the obtained research results, to determine synergy effects and trends, to connect the actors in person and in conclusion, to strengthen the research field as well as the MHI community. In addition, there is the possibility to become acquatined with the organizing institute. Primary audience is formed by members of the scientific society for assembly, handling and industrial robotics (WGMHI)

    TLC : une architecture photovoltaïque concentrée (CPV) au potentiel d’efficacité élevé à faible coût

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    Abstract: Human civilization has grown dependent on ready access to low-cost energy, but the fossil fuels that currently meet the bulk of humanity’s energy needs are causing environmental destruction, including potentially catastrophic global warming. Solar energy has to potential to halt global warming, and, if low enough in cost, to also bring the whole world’s population to a first world living standard. Silicon PV has dramatically reduced costs largely through decreasing the cost and increasing the efficiency of the silicon cells, but silicon is nearing its theoretical efficiency limits, and even if the cells were free, silicon PV would still be too expensive to meet these goals. Tandem CPV cells are roughly twice as efficient as silicon, but previous CPV designs have been unable to compete with silicon on cost in spite of the efficiency advantage. A new CPV architecture, called TLC for its trough, lens and cone concentration stages, proposed using initial concentration by a low-cost trough mirror to shrink the rest of an CPV module by 40X and thus reduce overall module costs. But before this PhD research project, TLC was only a paper study. This PhD research project was started to answer the question of whether TLC could work out as well as it appeared, or whether there were hidden flaws that precluded beating silicon PV on cost, or possibly even precluded TLC from working at all. Thesis chapter 3 details the main optical design aspects, and chapter 4 covers the design of the rest of the TLC module, including leading variations where there is more than one plausible way to achieve low cost and high reliability. The work included building a unified analytical model spreadsheet that linked known aspects of the TLC design together and estimated costs for a given design variation. Thesis chapter 5 covers the economics of the proposed design, with a focus on materials costs since these dominate PV overall costs, and a section on reliability since product lifetime strongly influences life-cycle cost. The work included building 3D-CAD models to refine the TLC design, and then the prototyping of individual parts and processes, and finally building a physical prototype of a TLC mini-module and putting it in sun. This physical confirmation was necessary because even after TLC has been “built” many times, in visualization, on paper, on spreadsheets, and then in COMSOL, until TLC was physically built, hidden flaws could arise at any time. Chapter 6 of this thesis covers the simulation and validation carried out to show that it is plausible that TLC can meet its cost targets. The conclusion of this thesis summarizes the overall project. The project was a success, producing a TLC design with high potential efficiency, very low materials cost, and low estimated process costs, with the potential to beat even the US Department of Energy’s goal for PV pricing in 2030. Ray-tracing a 3D model showed that the design could achieve high concentration with adequate acceptance angles, and tests showed that the prototyping cells were suitable for TLC’s massively parallel microcell-array receiver configuration. The project also successfully tested the proposed manufacturing process for molding semi-dense arrays of tertiary optical elements on the back of a lens tile and assembled a TLC mini module which was tested on sun at the focus of a trough mirror. Four papers have already been published, with a fifth paper accepted, as result of this work.La civilisation humaine est devenue de plus en plus dépendante d'un accès facile à une énergie à faible coût, mais les combustibles fossiles qui répondent actuellement à la majeure partie des besoins énergétiques de l'humanité causent la destruction de l'environnement, y compris un réchauffement climatique potentiellement catastrophique. L'énergie solaire a le potentiel d'arrêter le réchauffement climatique et, si son coût est suffisamment bas, d'amener également la population mondiale entière à un niveau de vie du premier monde. Les coûts de photovoltaïque (PV) à base de silicium ont été considérablement réduits en grande partie en diminuant le prix et en augmentant l'efficacité des cellules en silicium, cependant l’utilisation de silicium a ses limites d'efficacité théoriques, et même si les cellules étaient gratuites, la PV à base de silicium serait encore trop chère pour atteindre ces objectifs. Les cellules de photovoltaïque concentré (CPV) Tandem sont environ deux fois plus efficaces que celles à base de silicium, mais malgré l'avantage de leur efficacité, les architectures des années précédentes de CPV n'ont pas été en mesure de rivaliser avec le silicium en termes de coût. Une nouvelle architecture CPV, appelée TLC (Trough-Lens-Cone) utilise la concentration initiale par un miroir parabolique à faible coût combiné avec un module CPV de 40X et ainsi réduire les coûts globaux du module. Avant ce projet de recherche de doctorat, TLC n'était qu'une étude sur papier. Cette thèse a pour but de répondre à la question de savoir si l’approche TLC pouvait fonctionner aussi bien qu'elle était apparue, ou s'il y avait des défauts cachés qui empêchaient de battre le silicium PV sur le coût, ou pourrait même empêcher la TLC de fonctionner. Ce travail comprenait la construction d'un modèle de tableur unifié qui reliait les aspects connus de la conception TLC et les coûts estimés pour une variation de conception donnée. Nous présentons également la construction de modèles 3D-CAD pour raffiner la conception TLC, puis le prototypage de pièces individuelles et de processus, et enfin la construction d'un prototype physique d'un mini-module TLC qui est mis au soleil. Cette validation physique était nécessaire car même après que TLC ait été théoriquement et numériquement « construit » à plusieurs reprises soit, en visualisation, sur papier, sur des feuilles de calcul, puis dans COMSOL, avant que TLC soit physiquement construit, des défauts cachés pouvaient survenir à tout moment. La mise en œuvre de ce projet a réussi, produisant une conception TLC cohérente qui avait un rendement élevé avec un coût des matériaux très bas et des faibles coûts estimatifs de processus, avec un potentiel de battre même l’objectif du département américain de l'énergie pour la tarification du silicium photovoltaïque en 2030. Le suivi de raies (Ray-tracing) avec un modèle 3D a montré que la conception pouvait atteindre une concentration élevée avec des angles d'acceptation adéquats. Les tests ont également montré que les cellules de prototypage ont été bien adaptées à la nouvelle configuration de TLC de récepteur à matrice de microcellules massivement parallèle. Le projet a également testé avec succès le processus de fabrication proposé pour le moulage de réseaux semi-denses d'éléments optiques tertiaires à l'arrière d'un carreau de lentille. Le projet a également réussi à assembler un mini-module TLC et à tester sous le soleil avec le focus d'un miroir parabolique. Quatre articles ont déjà été publiés, avec un cinquième article accepté, à la suite de ce travail

    Latest Hydroforming Technology of Metallic Tubes and Sheets

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    This Special Issue and Book, ‘Latest Hydroforming Technology of Metallic Tubes and Sheets’, includes 16 papers, which cover the state of the art of forming technologies in the relevant topics in the field. The technologies and methodologies presented in these papers will be very helpful for scientists, engineers, and technicians in product development or forming technology innovation related to tube hydroforming processes

    Agricultural Structures and Mechanization

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    In our globalized world, the need to produce quality and safe food has increased exponentially in recent decades to meet the growing demands of the world population. This expectation is being met by acting at multiple levels, but mainly through the introduction of new technologies in the agricultural and agri-food sectors. In this context, agricultural, livestock, agro-industrial buildings, and agrarian infrastructure are being built on the basis of a sophisticated design that integrates environmental, landscape, and occupational safety, new construction materials, new facilities, and mechanization with state-of-the-art automatic systems, using calculation models and computer programs. It is necessary to promote research and dissemination of results in the field of mechanization and agricultural structures, specifically with regard to farm building and rural landscape, land and water use and environment, power and machinery, information systems and precision farming, processing and post-harvest technology and logistics, energy and non-food production technology, systems engineering and management, and fruit and vegetable cultivation systems. This Special Issue focuses on the role that mechanization and agricultural structures play in the production of high-quality food and continuously over time. For this reason, it publishes highly interdisciplinary quality studies from disparate research fields including agriculture, engineering design, calculation and modeling, landscaping, environmentalism, and even ergonomics and occupational risk prevention

    Haptics: Science, Technology, Applications

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    This open access book constitutes the proceedings of the 13th International Conference on Human Haptic Sensing and Touch Enabled Computer Applications, EuroHaptics 2022, held in Hamburg, Germany, in May 2022. The 36 regular papers included in this book were carefully reviewed and selected from 129 submissions. They were organized in topical sections as follows: haptic science; haptic technology; and haptic applications
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