5,070 research outputs found

    The Potential of Electrospinning to Enable the Realization of Energy-Autonomous Wearable Sensing Systems

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    The market for wearable electronic devices is experiencing significant growth and increasing potential for the future. Researchers worldwide are actively working to improve these devices, particularly in developing wearable electronics with balanced functionality and wearability for commercialization. Electrospinning, a technology that creates nano/microfiber-based membranes with high surface area, porosity, and favorable mechanical properties for human in vitro and in vivo applications using a broad range of materials, is proving to be a promising approach. Wearable electronic devices can use mechanical, thermal, evaporative and solar energy harvesting technologies to generate power for future energy needs, providing more options than traditional sources. This review offers a comprehensive analysis of how electrospinning technology can be used in energy-autonomous wearable wireless sensing systems. It provides an overview of the electrospinning technology, fundamental mechanisms, and applications in energy scavenging, human physiological signal sensing, energy storage, and antenna for data transmission. The review discusses combining wearable electronic technology and textile engineering to create superior wearable devices and increase future collaboration opportunities. Additionally, the challenges related to conducting appropriate testing for market-ready products using these devices are also discussed

    Microwave - Plasma based Thermal Treatment of Asphaltene - derived Carbon Fibres

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    Asphaltene-based carbon fibres have emerged as a significant and sustainable alternative to conventional Polyacrylonitrile (PAN)-based carbon fibres, owing to their abundant availability, aromatic nature, and high carbon content. This thesis investigates the utilization of asphaltenes, extracted from bitumen in Alberta oilsands, as a valuable precursor for the manufacturing of carbon fibres. The precursor employed in commercial carbon fibre manufacturing accounts for approximately 51% of the total production cost. The utilization of asphaltene as a precursor offers the potential for cost reduction in carbon fibre production. With this reduced cost, carbon fibres, renowned for their exceptional mechanical properties such as high stiffness, remarkable tensile strength, chemical resistance, and capacity to withstand higher temperatures, can find applications across wide range of industries. Moreover, this cost reduction also contributes to the economic viability of converting industrial waste into valuable products. Conventional post-treatment processes in carbon fibre manufacturing, such as furnace stabilization and carbonization, play a crucial role in the production process, demanding considerable time and energy resources. Post-treatment alone, comprising 38% of the overall cost of carbon fibre production, significantly impacts the economic aspects of the manufacturing process. In this thesis, asphaltenes derived from Alberta oilsands are pretreated with solvents such as pentane and toluene to remove coke residues. Later, these asphaltenes are transformed into fibres through the process of melt spinning using a twin-screw extruder. An innovative approach involving microwave plasma thermal treatment, replacing conventional post-treatment methods, specifically carbonization, is then applied to convert these fibres into carbon fibres. The study of microwave plasma behaviour and its corresponding temperatures is successfully conducted through the use of Multiphysics Finite Element Analysis (FEA). An experimental optimization study involving the thermal treatment of stabilized fibres under varying power levels and treatment durations using microwave plasma has been conducted. The study successfully implemented microwave plasma techniques to achieve carbonization of asphaltene fibres, resulting in an increase in carbon content and the development of a well-ordered crystalline structure. The Element analysis revealed the dynamic changes in elemental composition, showcasing the effectiveness of microwave plasma in achieving carbonization. X-ray diffraction patterns and Raman spectroscopy provided valuable insights into the structural evolution, highlighting the unique impact of microwave plasma treatment on the development of a layered graphite-like structure and higher graphitic content. However, it is essential to acknowledge limitations, such as the observed surface damage and reduced tensile strength in microwave-plasma treated fibres, emphasizing the need for further optimization of parameters to maximize the benefits of this innovative approach. Overall, this research contributes valuable insights to the field of carbon fibre manufacturing, paving the way for more sustainable and economically feasible production processes with the utilization of asphaltene-based precursors and microwave plasma techniques

    Blending of Alberta Oilsands Asphaltene (AOA) with Polymers for Manufacturing of Carbon Fibres

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    Carbon fibres (CFs), characterized by a carbon content of 90 wt.% or above, derived from polymeric precursors, have garnered considerable interest since their discovery by Shindo in 1961. Their unique properties have led to widespread applications in sectors such as energy, aerospace, medical, and sports, where lightweight structures with excellent mechanical attributes are essential. Anticipated growth in demand for CFs over the next five years underscores the need for a substantial reduction in manufacturing costs. Currently, the main precursors for carbon fibre (CF) production are poly(acrylonitrile) (PAN), pitch, and cellulose. However, the substantial costs associated with these raw materials and production methods present significant challenges. Alberta oilsands asphaltene (AOA), the heaviest fraction of Alberta Oilsands Bitumen, stands out as a promising alternative precursor. It is estimated to be one to two orders of magnitude less expensive than PAN, and it possesses favorable attributes such as high carbon content, high aromaticity, and abundant reserves. Despite these economic advantages, the brittleness of AOA limits its processing capabilities, impeding the widespread utilization of CFs derived from AOA. Polymer blending proves to be an effective method for enhancing the physical and chemical properties of polymer materials. This process enhances the melt spinnability of polymers, resulting in improved manufacturing efficiency and enhanced mechanical performance. The effects of polymer blending on the spinnability of AOA, subsequent post-treatment processes, and the ultimate properties of carbon fibres remain poorly. Investigating the behaviors of AOA with and without polymer additives is crucial, as it can provide meaningful insights for the manufacturing of carbon fibres derived from AOA. The manufacturing process for CFs involves melting precursors and processing them into spun fibres, followed by post-treatment processes like stabilization, carbonization, and graphitization. Stabilization process accounts for the most cost and determine the properties of the final carbon fibre products. Better and more efficient stabilization processes account for better performance of carbon fibres. The conditions to stabilize and carbonize AOA fibres, behaviors, and mechanism of the post-treatment remain unclear. This research focuses on the potential of AOA as a CF precursor, emphasizing (1) preprocessing AOA feedstocks, (2) modifying AOA using polymer additives, (3) designing a melt spinning process for AOA fibres, and (4) employing conventional thermal treatment for post-treatment including stabilization and carbonization processes. Solvent preprocessing and strategic additive use aim to enhance the viscosity and spinnability of AOA. Polystyrene and poly(styrene-butadiene-styrene) are employed and compared as polymer additives for blending with asphaltene, with the anticipation of enhancing the performance of AOA. Melt spinning is proposed for preparing fibres tailored for various applications. Melt spinning system, including extruder, melt pump, and godets, are designed for processing asphaltene sample. Thermal post-treatment, including stabilization and carbonization processes, were performed for stabilizing and carbonizing AOA fibres with or without polymer additives

    Functional Nanomaterials and Polymer Nanocomposites: Current Uses and Potential Applications

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    This book covers a broad range of subjects, from smart nanoparticles and polymer nanocomposite synthesis and the study of their fundamental properties to the fabrication and characterization of devices and emerging technologies with smart nanoparticles and polymer integration

    Chinese Knitwear Brands: The need for creative design to result in global business success

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    Chinese cashmere knitwear companies have become suppliers of international fashion brands because of their technological excellence, advantages of raw materials and competitive prices. However, their in-house brands are steadily declining. In the past 15 years, Chinese cashmere brands have progressively lost their market share to Chinese and Western fashion brands, with a few notable exceptions. Their brands lack differentiation from other Chinese competitors, causing low price competition, which contributes to sustainability issues such as unsold stock and material/manpower waste. The decline is likely to continue as the brands serve only an ageing market, rather than attracting younger generations to their products. Chinese cashmere companies invest little in design, which is a significant limitation for improving the brands’ opportunity to become successful and sustainable businesses. This study looks for solutions from the design perspective. The research aimed to investigate what design can do to help deal with the current problems of the Chinese knitwear brands to improve their prospects for future business success. The objectives of the study were to enquire into the challenges and opportunities facing the Chinese knitwear sector, to evaluate current design practice in knitwear brands, to understand how design and brand management can be integrated to generate a sustainable brand. Research questions were developed to explore the brand and design problems, the role of design and organisational structure, what the barriers and enablers for a thriving design culture were alongside possible solutions for design improvement. A pragmatic philosophy underpinned research design, guiding the adoption of methods in response to research questions. Interviews with stakeholders from both the knitwear industry and design education were undertaken. In addition, a case study using design action research with immersive field research was developed for investigating the knitwear brand issues; furthermore, a knitwear collection was created using western design approaches to demonstrate an exemplar design process for the sector and to illustrate the differences to current Chinese design methods. The study argues the obstacles to design culture enrichment in Chinese knitwear brands was caused by their design context, lack of brand positioning, limited understanding of their consumers and business models that are not fit for purpose. An absence of experienced leadership creates unclear design direction, instead of collections centred around a theme; Chinese brands sell unconnected designs. Brands lack the distinct brand characteristics that distinguish them from their competitors. The contribution to knowledge made by this study includes the identification of the reasons for the decline in Chinese cashmere brands, an understanding of their barriers to design culture to developing good designs and it also highlights the lack of awareness of sustainability issues in the sector. The study sheds new light on the rarely acknowledged issue of how to upgrade these brands as modern business for younger consumers, and how to enrich the design culture for brand business growth within sustainable contexts. The thesis analyses in depth the causes for the decline in these brands and makes recommendations for how design can make a contribution to reversing the brands’ decline and increasing their sustainability

    Innovative unidirectional recycled carbon fiber tape structure for high performance thermoplastic composites: technological developments, technology-structure-property relationship and modeling of composite tensile properties

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    The rapidly growing demand for carbon fiber reinforced plastics in high-tech industries, such as aerospace, defense, automotive, wind turbine engineering, building and sports, resulted in a high amount of waste in the form of dry waste (e.g., production off-cuts), wet waste (e.g., out-of-date prepreg) and end-of-life components waste (e.g., aircraft components). Furthermore, the production of carbon fibers is cost and energy-intensive. Therefore, technological developments for the gentle processing of recycled carbon fiber and its integration into high-performance composites with promising tensile properties have gained considerable attention. Consequently, injection molding, nonwovens and hybrid yarn technologies were developed in recent years to integrate recycled carbon fiber into the high-performance thermoplastic composite. It is unfortunate that these technologies develop composites with a lack of unidirectional fiber orientation; therefore, the potential of recycled carbon fiber in high-performance composites is not thoroughly exhausted. This thesis primarily addresses the development of an innovative structure with a unidirectional fiber orientation termed “unidirectional recycled carbon fiber tape structure” for high-performance thermoplastics composites. The technological concept of the unidirectional structure comprises fiber opening, carding, drawing and a novel tape-forming process. In this concept, fiber opening, carding, and drawing processes were utilized to develop homogeneous, uniform, and highly oriented hybrid slivers. In the next step, these hybrid slivers were converted into a unidirectional recycled carbon fiber tape structure through a novel tape-forming process. To implement this concept, technological developments (investigations, modifications, optimization and further developments), were carried out in fiber opening, carding and drawing processes to develop a hybrid sliver with improved uniformity, homogeneity and unidirectional orientation. In the second phase, conception, design, technological developments, construction and prototype development were implemented to develop a novel tape-forming process. The result confirms that tape development technology comprising fiber opening, carding, drawing and prototype tape forming processes is an innovative, eco-friendly and sustainable technology compared to existing technologies. Furthermore, the consolidation process transformed the unidirectional tape structure into high-performance thermoplastic composites. Subsequently, technology-structure-property relationships were established to develop composites with tailor-made properties. The analysis reveals that selecting optimum technological, consolidation and structural parameters develop tape and composite structures with unidirectional fiber orientation. As a result, experimental results of a high-performance composite developed from a unidirectional recycled carbon fiber tape structure show a very high tensile strength of 1350 ± 28 MPa and an E-module of 84.7 ± 2.3 GPa. This analysis confirms that unidirectional fibers configuration in composites brings a revolution toward developing cost-efficient, high-performance composites for load-bearing structural applications. Finally, theoretical and finite element modeling of tensile properties of high-performance composites reveals that modified models show good agreement with composite tensile properties

    Enhancing the forensic comparison process of common trace materials through the development of practical and systematic methods

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    An ongoing advancement in forensic trace evidence has driven the development of new and objective methods for comparing various materials. While many standard guides have been published for use in trace laboratories, different areas require a more comprehensive understanding of error rates and an urgent need for harmonizing methods of examination and interpretation. Two critical areas are the forensic examination of physical fits and the comparison of spectral data, which depend highly on the examiner’s judgment. The long-term goal of this study is to advance and modernize the comparative process of physical fit examinations and spectral interpretation. This goal is fulfilled through several avenues: 1) improvement of quantitative-based methods for various trace materials, 2) scrutiny of the methods through interlaboratory exercises, and 3) addressing fundamental aspects of the discipline using large experimental datasets, computational algorithms, and statistical analysis. A substantial new body of knowledge has been established by analyzing population sets of nearly 4,000 items representative of casework evidence. First, this research identifies material-specific relevant features for duct tapes and automotive polymers. Then, this study develops reporting templates to facilitate thorough and systematic documentation of an analyst’s decision-making process and minimize risks of bias. It also establishes criteria for utilizing a quantitative edge similarity score (ESS) for tapes and automotive polymers that yield relatively high accuracy (85% to 100%) and, notably, no false positives. Finally, the practicality and performance of the ESS method for duct tape physical fits are evaluated by forensic practitioners through two interlaboratory exercises. Across these studies, accuracy using the ESS method ranges between 95-99%, and again no false positives are reported. The practitioners’ feedback demonstrates the method’s potential to assist in training and improve peer verifications. This research also develops and trains computational algorithms to support analysts making decisions on sample comparisons. The automated algorithms in this research show the potential to provide objective and probabilistic support for determining a physical fit and demonstrate comparative accuracy to the analyst. Furthermore, additional models are developed to extract feature edge information from the systematic comparison templates of tapes and textiles to provide insight into the relative importance of each comparison feature. A decision tree model is developed to assist physical fit examinations of duct tapes and textiles and demonstrates comparative performance to the trained analysts. The computational tools also evaluate the suitability of partial sample comparisons that simulate situations where portions of the item are lost or damaged. Finally, an objective approach to interpreting complex spectral data is presented. A comparison metric consisting of spectral angle contrast ratios (SCAR) is used as a model to assess more than 94 different-source and 20 same-source electrical tape backings. The SCAR metric results in a discrimination power of 96% and demonstrates the capacity to capture information on the variability between different-source samples and the variability within same-source samples. Application of the random-forest model allows for the automatic detection of primary differences between samples. The developed threshold could assist analysts with making decisions on the spectral comparison of chemically similar samples. This research provides the forensic science community with novel approaches to comparing materials commonly seen in forensic laboratories. The outcomes of this study are anticipated to offer forensic practitioners new and accessible tools for incorporation into current workflows to facilitate systematic and objective analysis and interpretation of forensic materials and support analysts’ opinions

    High-performance shape memory composites with intrinsic heating capabilities

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    Shape morphing structures have played a significant role within the field of aerospace for more than a century. While the shape morphing aerostructures of the past and present have depended on hinges and motors to achieve morphing, their future is expected to rely on smart materials and structures that have intrinsic shape morphing capabilities. One such smart material, that has previously been developed at Imperial College London, is the carbon fibre reinforced epoxy polymer (CFRP) composite with thermoplastic (TP) interleaves. These interleaved composites exhibit controllable stiffness (CS) and shape memory (SM) capabilities under suitable thermal conditions. While these interleaved composites showed excellent shape morphing capabilities, they had several drawbacks. These composites showed poor flexural modulus and through-thickness shear strength compared to the epoxy-based non-interleaved CFRP. These composites also used an oven to achieve the high temperatures required to exhibit the CS and SM capabilities. This thesis describes studies conducted to mitigate these drawbacks. In the first study described in this thesis, the source of the premature through-thickness shear failure in TP interleaved CFRP composites was discovered to be the low shear strength of the polystyrene (PS) interleaves used in previous works. It was then demonstrated that replacing PS with Poly(styrene-co-acrylonitrile) (SAN) could improve the through-thickness shear strength of the interleaved composites to be almost as high as that of pristine CFRP. Furthermore, the SAN-interleaved CFRP laminates also exhibited excellent CS and SM capabilities. In the next study described in this thesis, it was demonstrated that the flexural modulus of TP interleaved CFRP composites can be substantially improved by two different methods- (i) reducing the thickness of the TP interleaves, and (ii) introducing reinforcements within the TP interleaves. The following study describes how intrinsic heating capability was achieved in TP interleaved CFRP composites, through resistive heating of heater elements such as stainless steel (SS) meshes and woven carbon fabric (WCF) embedded within the layup of the composite. This intrinsic heating strategy was used to supply the temperature necessary for the corresponding composites to exhibit CS and SM capabilities. As a result, these intrinsically heated TP interleaved CFRP composites exhibited successful out-of-oven morphing capabilities. In the final study described in this thesis, composite structures that were initially flat in their as-cured state, but were capable of deployment into planar and curved meshes were designed. Finite element numerical models were used to predict the deployment capabilities of these composite structures. Finally, the deployable composite mesh structures were manufactured and characterised.Open Acces

    Mechanical characterization, constitutive modeling and applications of ultra-soft magnetorheological elastomers

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    Mención Internacional en el título de doctorSmart materials are bringing sweeping changes in the way humans interact with engineering devices. A myriad of state-of-the-art applications are based on novel ways to actuate on structures that respond under different types of stimuli. Among them, materials that respond to magnetic fields allow to remotely modify their mechanical properties and macroscopic shape. Ultra-soft magnetorheological elastomers (MREs) are composed of a highly stretchable soft elastomeric matrix in the order of 1 kPa and magnetic particles embedded in it. This combination allows large deformations with small external actuations. The type of the magnetic particles plays a crucial role as it defines the reversibility or remanence of the material magnetization. According to the fillers used, MREs are referred to as soft-magnetic magnetorheological elastomers (sMREs) and hard-magnetic magnetorheological elastomers (hMREs). sMREs exhibit strong changes in their mechanical properties when an external magnetic field is applied, whereas hMREs allow sustained magnetic effects along time and complex shape-morphing capabilities. In this regard, end-of-pipe applications of MREs in the literature are based on two major characteristics: the modification of their mechanical properties and macrostructural shape changes. For instance, smart actuators, sensors and soft robots for bioengineering applications are remotely actuated to perform functional deformations and autonomous locomotion. In addition, hMREs have been used for industrial applications, such as damping systems and electrical machines. From the analysis of the current state of the art, we identified some impediments to advance in certain research fields that may be overcome with new solutions based on ultrasoft MREs. On the mechanobiology area, we found no available experimental methodologies to transmit complex and dynamic heterogeneous strain patterns to biological systems in a reversible manner. To remedy this shortcoming, this doctoral research proposes a new mechanobiology experimental setup based on responsive ultra-soft MRE biological substrates. Such an endeavor requires deeper insights into the magneto-viscoelastic and microstructural mechanisms of ultra-soft MREs. In addition, there is still a lack of guidance for the selection of the magnetic fillers to be used for MREs and the final properties provided to the structure. Eventually, the great advances on both sMREs and hMREs to date pose a timely question on whether the combination of both types of particles in a hybrid MRE may optimize the multifunctional response of these active structures. To overcome these roadblocks, this thesis provides an extensive and comprehensive experimental characterization of ultra-soft sMREs, hMREs and hybrid MREs. The experimental methodology uncovers magneto-mechanical rate dependences under numerous loading and manufacturing conditions. Then, a set of modeling frameworks allows to delve into such mechanisms and develop three ground-breaking applications. Therefore, the thesis has lead to three main contributions. First and motivated on mechanobiology research, a computational framework guides a sMRE substrate to transmit complex strain patterns in vitro to biological systems. Second, we demonstrate the ability of remanent magnetic fields in hMREs to arrest cracks propagations and improve fracture toughness. Finally, the combination of soft- and hard-magnetic particles is proved to enhance the magnetorheological and magnetostrictive effects, providing promising results for soft robotics.Los materiales inteligentes están generando cambios radicales en la forma que los humanos interactúan con dispositivos ingenieriles. Distintas aplicaciones punteras se basan en formas novedosas de actuar sobre materiales que responden a diferentes estímulos. Entre ellos, las estructuras que responden a campos magnéticos permiten la modificación de manera remota tanto de sus propiedades mecánicas como de su forma. Los elastómeros magnetorreológicos (MREs) ultra blandos están compuestos por una matriz elastomérica con gran ductilidad y una rigidez en torno a 1 kPa, reforzada con partículas magnéticas. Esta combinación permite inducir grandes deformaciones en el material mediante la aplicación de campos magnéticos pequeños. La naturaleza de las partículas magnéticas define la reversibilidad o remanencia de la magnetización del material compuesto. De esta manera, según el tipo de partículas que contengan, los MREs pueden presentar magnetización débil (sMRE) o magnetización fuerte (hMRE). Los sMREs experimentan grandes cambios en sus propiedades mecánicas al aplicar un campo magnético externo, mientras que los hMREs permiten efectos magneto-mecánicos sostenidos a lo largo del tiempo, así como programar cambios de forma complejos. En este sentido, las aplicaciones de los MREs se basan en dos características principales: la modificación de sus propiedades mecánicas y los cambios de forma macroestructurales. Por ejemplo, los campos magnéticos pueden emplearse para inducir deformaciones funcionales en actuadores y sensores inteligentes, o en robótica blanda para bioingeniería. Los hMREs también se han aplicado en el ámbito industrial en sistemas de amortiguación y máquinas eléctricas. A partir del análisis del estado del arte, se identifican algunas limitaciones que impiden el avance en ciertos campos de investigación y que podrían resolverse con nuevas soluciones basadas en MREs ultra blandos. En el área de la mecanobiología, no existen metodologías experimentales para transmitir patrones de deformación complejos y dinámicos a sistemas biológicos de manera reversible. En esta investigación doctoral se propone una configuración experimental novedosa basada en sustratos biológicos fabricados con MREs ultra blandos. Dicha solución requiere la identificación de los mecanismos magneto-viscoelásticos y microestructurales de estos materiales, según el tipo de partículas magnéticas, y las consiguientes propiedades macroscópicas del material. Además, investigaciones recientes en sMREs y hMREs plantean la pregunta sobre si la combinación de distintos tipos de partículas magnéticas en un MRE híbrido puede optimizar su respuesta multifuncional. Para superar estos obstáculos, la presente tesis proporciona una caracterización experimental completa de sMREs, hMREs y MREs híbridos ultra blandos. Estos resultados muestran las dependencias del comportamiento multifuncional del material con la velocidad de aplicación de cargas magneto-mecánicas. El desarrollo de un conjunto de modelos teórico-computacionales permite profundizar en dichos mecanismos y desarrollar aplicaciones innovadoras. De este modo, la tesis doctoral ha dado lugar a tres bloques de aportaciones principales. En primer lugar, este trabajo proporciona un marco computacional para guiar el diseño de sustratos basados en sMREs para transmitir patrones de deformación complejos in vitro a sistemas biológicos. En segundo lugar, se demuestra la capacidad de los campos magnéticos remanentes en los hMRE para detener la propagación de grietas y mejorar la tenacidad a la fractura. Finalmente, se establece que la combinación de partículas magnéticas de magnetización débil y fuerte mejora el efecto magnetorreológico y magnetoestrictivo, abriendo nuevas posibilidades para el diseño de robots blandos.I want to acknowledge the support from the Ministerio de Ciencia, Innovación y Universidades, Spain (FPU19/03874), and the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 947723, project: 4D-BIOMAP).Programa de Doctorado en Ingeniería Mecánica y de Organización Industrial por la Universidad Carlos III de MadridPresidente: Ramón Eulalio Zaera Polo.- Secretario: Abdón Pena Francesch.- Vocal: Laura de Lorenzi

    The effect of pattern recognition receptor RIG-I variant expression during mammalian- or avian-adapted influenza A infection and adaptation in the mouse.

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    Influenza A virus infections are common all over the world and cause substantial damage on health and economy by seasonal outbreaks. The infectious disease flu becomes even more life threatening when followed by a secondary bacterial infection, for which especially children and immune-suppressed people are susceptible. Today, the annually adapted influenza vaccination is an important tool to prevent outbreaks of flu. Medical treatments of acute infections are limited with the exceptions of therapeutically targeting the viral proteins neuraminidase and M2. A deeper understanding of the molecular mechanisms of the IAV pathogenicity and antiviral defense mechanisms, as well as their interaction, can help to refine vaccination strategies and direct therapeutic options to generate more target specific and effective antiviral drugs. The pattern recognition receptor RIG-I is one of the most important sensors of the innate immune system to detect foreign RNAs. Upon the binding of RNA ligands like the panhandle structures of influenza A virus, RIG-I amongst others mediates the expression of interferon type 1 and interleukin-1β in an ATPase dependent manner. Additionally, the binding of RIG-I to the viral panhandle structures is confirmed in vitro as another antiviral function by blocking the access for the viral polymerase, as firstly described by Friedemann Weber in the year 2015. The main aim of this thesis was to investigate the contribution of the different antiviral effects of RIG-I against the influenza A virus in a mouse infection model. Furthermore, additional insights about the RIG-I blocking function should be gained. Therefore, a mouse line deficient in RIG-I signaling and another one lacking RIG-I expression were established with the help of genetic engineering. Additionally, two recombinant influenza strains harboring an adaptation in the viral polymerase gene either to mammalian hosts or to avian hosts (polymerase subunit 2 codon 627K and 627E) were generated. Both virus strains were validated for different quality features. The recombinant virus strains were used to perform an infection study using RIG-I wild type, signaling-deficient and knockout mice. Investigating the effect of RIG-I variant expression on parameters like weight reduction, lung virus titer, loss of lung barrier integrity, interferon and cytokine concentration in response to the influenza A infection, new insights in the antiviral functions of RIG-I were gained. The established mouse lines expressing signaling-deficient or no RIG-I did not develop any detectable burden by their genotype. The RIG-I-mediated interferon-α induction was found to be abolished in bone marrow derived macrophages of mice with signaling deficiency in RIG-I as well as RIG-I knockout mice while it was intact in RIG-I wild type mouse derived cells, as expected. Hence, an unburdened mouse line with RIG-I signaling deficiency and one with a RIG-I knockout were generated. The RIG-I PM line is the first of its kind. While the generation of a mammalian-adapted recombinant influenza A strain was successful from the beginning, the generation of the avian-adapted strain was not successful in mammalian cells. A sufficient replication of both strains was achieved in the DF-1 chicken cell line. The received stock preparations showed similar abilities and the stability of their respective genotype was confirmed over several passages in different cell lines. While the infection of mice with the generated recombinant influenza A strains led to a significant change in observed infection parameters and cytokine signaling, only a weak effect of RIG-I variant expression on the infection parameters was detectable. Additionally, the results deliver hints for a RIG-I dependent induction of IFN-γ by RIG-I, which was not described in detail yet. The data also suggest that the antiviral functions of RIG-I may be potently inhibited by the viral nonstructural protein 1 and the mammalian-adapted polymerase variant. The validation of the genetic stability of the virus strain with the avian-adapted polymerase variant in vivo indicates a significant back mutation to the original mammalian-adapted genotype over the course of the infection. This was significantly affected by the time post infection and the type of RIG I variant expression. A lower rate of back mutation than in RIG-I wild type mice was detected in mice with RIG-I signaling deficiency and the lowest in mice with RIG-I knockout. These findings suggests that both the RIG-I signaling functions and the RIG-I blocking function mediate a selective pressure on the influenza A polymerase subunit 2 codon 627. This conclusion is supported by the results of an in vitro competitive infection assay with both virus variants together, showing a replication advantage of the mammalian-adapted polymerase variant over the avian-adapted variant that is affected by the type of RIG-I expression. Taken together, the results of this study deliver deep insights into the interaction between the innate pattern recognition receptor RIG-I and the influenza A virus. The findings suggest that the presence of RIG-I forces viral polymerase variants common in avian to adapt to a mammalian host. Further, the study delivers additional data confirming a RIG-I-mediated antiviral effect by blocking the access of the viral polymerase to the panhandle structures of viral RNAs. Additionally, the data suggests a high potency of the nonstructural protein 1 and the mammalian-adapted polymerase subunit 2 codon 627K to prevent the effects of RIG-I. The finding that RIG-I may contribute to interferon-γ release could be interesting and should be investigated in future studies, since this interaction is poorly described in the literature, but connects two important features of the innate immune system
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