<p>Naturally-occurring biological materials with stiff mineralized reinforcement embedded in a ductile matrix are commonly known to achieve excellent balance between stiffness, strength and ductility. Interestingly, nature offers a broad diversity of architectural motifs, exemplify the multitude of ways in which exceptional mechanical properties can be achieved. Such diversity is the source of bio-inspiration and its translation to synthetic material systems. In particular, the helicoid and the “brick and mortar” architectured materials are two key architectural motifs we are going to study and to synthesize new bio-inspired materials. </p> <p>Due to geometry mismatch(misorientation) and incompatibilities of mechanical properties between fiber and matrix materials, it is acknowledged that misoriented stiff fibers would rotate in compliant matrix beneath uniaxial deformation. However, the role of fiber reorientation inside the flexible matrix of helicoid composites on their mechanical behaviors have not yet been extensively investigated. In the present project, fiber reorientation values of single misoriented laminae, mono-balanced laminates and helicoid architectures under uniaxial tensile are calculated and compared. In the present work, we introduce a Discontinuous Fiber Helicoid (DFH) composite inspired by both the helicoid microstructure in the cuticle of mantis shrimp and the nacreous architecture of the red abalone shell. We employ 3D printed specimens, analytical models and finite element models to analyze and quantify in-plane fiber reorientation in helicoid architectures with different geometrical features. We also introduce additional architectures, i.e., single unidirectional lamina and mono-balanced architectures, for comparison purposes. Compared with associated mono-balanced architectures, helicoid architectures exhibit less fiber reorientation values and lower values of strain stiffening. The explanation for this difference is addressed in terms of the measured in-plane deformation, due to uniaxial tensile of the laminae, correlated to lamina misorientation with respect to the loading direction and lay-up sequence.</p> <p>In addition to fiber, rod-like, reinforced laminate, platelet reinforced composite materials, “brick and mortar” architectures, are going to be discussed as well, since it can provide in-plane isotropic behavior on elastic modulus that helicoid architecture can offer as well, but with different geometries of reinforcement. Previous “brick and mortar” models available in the literature have provided insightful information on how these structures promote certain mechanisms that lead to significant improvement in toughness without sacrificing strength. In this work, we present a detailed comparative analysis that looks at the three-dimensional geometries of the platelet-like and rod-like structures. However, most of these previous analyses have been focused on two-dimensional representations. We 3D print and test rod-like and tablet-like architectures and analyze the results employing a computational and analytical micromechanical model under a dimensional analysis framework. In particular, we focus on the stiffness, strength and toughness of the resulting structures. It is revealed that besides volume fraction and aspect ratio of reinforcement, the effective shear and tension area in the matrix governs the mechanical behavior as well. In turns, this leads to the conclusion that rod-like microstructures exhibit better performance than tablet-like microstructures when the architecture is subjected to uniaxial load. However, rod-like microstructures tend to be much weaker and brittle in the transverse direction. On the other hand, tablet-like architectures tend to be a much better choice for situations where biaxial load is expected.</p> <p>Through varying the geometry of reinforcement and changing the orientation of reinforcement, different architectural motifs can promote in-plane mechanical properties, such as strain stiffening under uniaxial tensile, strength and toughness under biaxial tensile loading. On the other hand, the various out-of-plane orientation of the reinforcement leads to functionally graded effective indentation stiffness. The external layer of nacre shell is composed of calcite prisms with graded orientation from surface to interior. This orientation gradient leads to functionally graded Young’s modulus, which is confirmed to have higher fracture resistance than homogenous materials under mode I fracture loading act.</p> <p>Similar as graded prism orientation in calcite layer of nacre, the helicoid architecture found in nature exhibits gradients on geometrical parameters as well. The pitch distance of helicoid architecture is found to be functionally graded through the thickness of biological materials, including the dactyl club of mantis shrimp and the fish scale of coelacanth. This can be partially explained by the long-term evolution and selection of living organisms to create high performance biological materials from limited physical, chemical and geometrical elements. This naturally “design” procedure can provide us a spectrum of design motifs on architectural materials. </p> <p>In the present work, linear gradient on pitch distance of helicoid architectures, denoted by functionally graded helicoid (FGH), is chose to be the initial pathway to understand the functionality of graded pitch distance, associated with changing pitch angle. Three-point bending on short beam and low-velocity impact tests are employed in FEA to analyze the mechanical properties of composite materials simultaneously. Both static(three-point bending) and dynamic(low-velocity impact) tests reveal that FGH with pitch angle increasing from surface to interior can provide multiple superior properties at the same time, such as peak load and toughness, while the helicoid architectures with constant pitch angle can only provide one competitive property at one time. Specifically, helicoid architectures with smaller pitch angle, such as 15-degree, show higher values on toughness, but less competitive peak load under static three-point bending loading condition, while helicoid architectures with middle pitch angle, larger than or equal to 22.5-degree and smaller than 45-degree, exhibit less value of toughness, but higher peak load. The explanation on this trend and the benefits of FGH is addressed by analyzing the transverse shear stresses distribution through the thickness in FEA, combined with analytical prediction. In low-velocity impact tests, the projected delamination area of helicoid architectures is observed to increase when the pitch angle is decreasing. Besides, laminates with specific pitch angles, such as 45-degree, classical quasi-isotropic laminate, 60-degree, specific angle ply, and 90-degree, cross-ply, are designed to compare with helicoid architectures and FGH.</p>

Natural composites, in particular nacre, often combine high strength and toughness thanks to highly ordered architectures and controlled geometries of the reinforcement components. However, combining strength, toughness and resorbability in synthetic materials remains a challenge in particular in the field of bone graft substitutes. In the present study, calcium phosphate-(CaP-)based materials with designed architectures inspired from natural composite materials were achieved. CaP platelets obtained by precipitation in organic medium were first aligned in chitosan matrices by solvent casting in ambient conditions. Efficient strengthening was obtained with 15 vol-% ceramic, reaching cortical bone strength (150 MPa) and preserving good ductility (5 % deformation). In a weak magnetic field, high spatial arrangement without percolation was maintained up to 20 vol-%. With directional freezing, good alignment of the platelets could be pushed up to 50 vol-%. In parallel, in situ recrystallization of CaP blocks in hydrothermal conditions led to hierarchical structures. The strength and the work-of-fracture were enhanced (300%) thanks to a change of failure mode.:Acknowledgements v Summary vii Background vii Thesis outline viii Part I: “Brick-and-mortar” structures with discrete reinforcement components ix Part II: “Textured” structures with continuous reinforcement components x Zusammenfassung xi Hintergrund xi Doktorarbeit Gliederung xii Teil I: “Ziegelmauer-Architektur” mit diskreten Verstärkungskomponenten xiii Teil II: “ Texturierte” Strukturen mit kontinuierlichen Verstärkungskomponenten xiv Chapter 1: General introduction 1 Bone grafting 1 CaP ceramics 1 How to improve toughness of CaP ceramics? 2 Importance of structure design: bio-inspiration 2 What mechanical properties should be reached? 5 Specific aims 5 Two general approaches to reach the goal 6 Nacre-inspired “brick-and mortar” structures (Part I) 6 Textured ceramic monoliths (Part II) 6 References 7 Chapter 2: Theoretical calculations 11 Introduction 12 Theoretical tensile strength of β-TCP platelets and critical size for flaw tolerance 13 Optimal aspect ratio 15 Composite strength and stiffness 17 Limitations 19 References 19 PART I: NACRE-INSPIRED “BRICK-AND-MORTAR” STRUCTURES Chapter 3: Synthesis of sub-micrometer calcium phosphate platelets 23 Introduction 24 ii Materials and Methods 25 Precipitation method 25 Reaction parameters 25 Characterization 26 Statistical analysis of results 28 Results 28 Reproducibility of standard experiments 28 Increase of the reagent volume to increase the productivity 30 Increase of the precursors concentration to increase the productivity and modify the particles 30 Increase of titration rate to simplify the process 32 Influence of temperature on the particles 35 Effect of the pH value on the particles 37 Effect of a longer reaction time on the particle stability 40 Study of the influence of variations of the Ca/P molar ratio 42 Discussion 43 Reproducibility 43 Productivity 44 CaP crystal shape 45 Crystal purity 47 Aspect ratio 48 Critical thickness 49 Uniformity of primary particles 50 Non agglomerated 51 General points 52 Conclusions 52 References 53 Chapter 4: Kinetics study of the calcium phosphate platelets growth 57 Introduction 58 Theory 58 Materials and methods 60 Materials and sample preparation 60 Characterization methods 61 Results 62 Visual observations during manipulations 62 SEM observations 62 XRD results 66 Size measurements 68 Kinetics calculations 70 Discussion 74 Nucleation and assembly mechanism 74 Reaction kinetics 76 Control of size and aspect ratio 76 Conclusions 77 References 78 Chapter 5: Structural design of bio-inspired composites by solvent casting 81 Foreword 82 Introduction 82 Experimental section 84 iii Synthesis of resorbable ceramic platelets 84 Solvent casting to prove the reinforcement efficiency of DCP platelets 84 Magnetization of the platelets 85 Maintaining the orientation during drying of an hydrogel matrix 86 Results 87 Synthesis of resorbable ceramic platelets 87 Solvent casting to prove the reinforcement efficiency of CaP platelets 87 Magnetization of the platelets 91 Maintaining the orientation during drying of an hydrogel matrix 93 Discussion 95 Detrimental effect of β-TCP platelets in chitosan 95 Efficient reinforcement with DCP platelets up to a given volume fraction 96 Threshold value for strength improvement 97 Fitting the experimental results with theoretical equations 98 Conclusions 101 References 101 Chapter 6: Biodegradable, strong and tough nacre-inspired structures obtained by freezecasting 105 Introduction 106 Experimental section 108 Synthesis of resorbable ceramic platelets 108 Preliminary freeze-casting tests with β-TCP-based slurries 108 Determination of adequate freeze-casting parameters for hydrogels-CaP slurries 108 Integration of CaP platelets and local planar alignment 109 Attempts to globally align porosity in two directions 109 Densification and consolidation 110 Tensile testing 110 Results 111 Preliminary freeze-casting tests with β-TCP-based slurries 111 Determination of adequate freeze-casting parameters for hydrogels-CaP slurries 112 Integration of CaP platelets and local planar alignment 113 Attempts to globally align porosity in two directions 119 Densification and consolidation 121 Tensile testing 121 Discussion 122 Conclusions 124 References 125 PART II: TEXTURED CERAMIC MONOLITHS Chapter 7: Micro-texturing by recrystallization of calcium phosphate blocks in hydrothermal conditions 127 Introduction 128 Materials and Methods 130 Samples characterization 132 Results 133 Macroscopic observations 133 Microstructural changes (SEM) 133 Crystalline phase conversion (XRD) 139 iv Mechanical properties 142 Fractured surfaces 142 Discussion 145 Conclusions 150 References 150 Chapter 8: Toughening of textured calcium phosphate blocks by polymer impregnation 155 Foreword 156 Introduction 156 Materials and Methods 157 Samples preparation 157 Characterization 158 Results 158 Porosity and microstructure 158 Composition 161 Mechanical properties 161 Discussion 162 Conclusions 164 References 164 Chapter 9: Synthesis and outlook 167 Curriculum Vitae 171

Les travaux présentés dans ce manuscrit de thèse s’articulent autour de la synthèse de nouvelles architectures moléculaires tridimensionnelles et de l’évaluation de ces architectures en tant que canaux ioniques synthétiques capables de promouvoir le transport transmembranaire d’ions. La première partie concerne la mise au point d’une voie d’accès à ces édifices ayant comme plateforme centrale une brique naphtothiophène, aromatique ou partiellement hydrogénée, ainsi que l’étude prospective de la conversion de ces architectures en plateforme hélicoïdale. Les propriétés de ces édifices sont étudiées à l’état solide et par voie de calculs théoriques, permettant de mettre en avant des informations quant à la topologie globale adoptée ainsi que la compréhension de certaines réactivités observées. Une seconde partie est dédiée à la fonctionnalisation de ces édifices en molécules présentant des propriétés amphiphiles puis à l’étude de la capacité de ces dernières à s’insérer dans une bicouche lipidiques modèle afin de promouvoir le transport d’ions à travers la membrane via la formation de canaux ioniques dits synthétiques. En outre, des études alliant des analyses de spectrométrie de masse et des calculs théoriques sont présentés afin de comprendre les interactions intervenant dans le processus de transport d’ions à travers la membrane lipidique. / The work presented in this manuscript is dealing with the synthesis of new three-dimensional molecular architectures and their evaluation as synthetic ion channels capable of promoting ion transmembrane transport. The first part aims at developing a straightforward approach to the synthesis of novel architectures based on a naphthothiophene platform, aromatic or partially hydrogenated, as well as the development of a strategy the convert 9-arylnaphthothiophene architectures into helical platforms. The properties of these molecules were studied in the solid state and were completed by theoretical calculations to highlight global topologies adopted. Theoretical calculations allowed us to understanding some reactivities observed. A second part is dedicated firstly to the functionalisation of these molecular architectures into amphiphilic molecules and secondly to study their abilities to insert themselves into a model bilayer lipid membrane by forming channels. Besides, in order to gain a better understanding of the interactions in play in the process, mass spectrometry analysis combined to theoretical calculations were set up.

Background: The world is facing environmental issues such as pollution, natural disasters, and climate change. A main cause of this is human activities such as urbanization and mining of materials. As the understanding of sustainability increases, new regulations from governments arise along with a surge in demand for sustainable solutions from customers. These factors will trigger a technological shift that companies need to tackle in order to stay competitive. Objectives: The aim of this research is to examine the barriers towards implementing bio-inspired methods for innovation. This will be done by studying innovators in relevant industries. Research question: What are the challenges with a large scale implementation of bio-inspired methods for innovation? Method: This study will be carried out by interviewing people working within the transportation and heavy construction industries. The candidates will, on a daily basis, work with innovation and thus contribute with their knowledge and reflections. The study will use semi-structured interviews followed by a thematic analysis to get results and draw conclusions. Results: The study shows that using methods for innovation is a common act. Furthermore, the candidates were asked how they integrate sustainability into their development. In general, the candidates had no unified answer to this question. However, several examples, such as lowering emissions, not buying from corrupt suppliers, and maintaining profitability, were mentioned. Moreover, the candidates states that the company works with identifying new methods for innovation. When asked about bio-inspired methods, most candidates were positive about an implementation. From another perspective, some candidates who work with biomimicry state the opposite. Conclusions: Using bio-inspired methods for innovation might be of interest, however, such an implementation takes long time due to organizational resistance. To understand this further, more industries and perspectives has to be studied.

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A plethora of multi-copter drones can be found in a variety of public and private sectors in society; crime detection, border guard, agricultural inspections, aerial photography, cinematography, television, and entertainment. Unlike commercial drones, ornithopters - flapping bird-like drones - have a very different materiality. The different aesthetics and flight dynamics of these machines require designers to rethink the design space of this kind of drone. This study aims to map out the preliminary design space of ornithopters and explore their interesting flight dynamics and material qualities. Participants were invited to a workshop to build and fly three different ornithopters and reflect on the ornithopters and their experiences while flying them. This thesis presents a series of insights into ornithopters, especially their unique materiality. The unique materials used in ornithopters, such as balsa wood, polystyrene, nylon and carbon fiber, allow them to fly more efficiently and withstand the forces of flight. Finally, I argue that designers can embrace the design space of ornithopters by creating features that amplify the unique and unpredictable movements of the machine, which could lead to new and innovative designs. This would work towards a celebration of non-uniformity of morphologies and movements in an ecosystem of biologically-inspired flying robots. / En mängd av multirotor drönare kan hittas i olika offentliga och privata sektorer i samhället; brottsbekämpning, gränskontroller, jordbruksinspektioner, flygfotografering, filmproduktion, television och underhållning. Till skillnad från kommersiella drönare har ornithoptorer - fågelliknande flaxande drönare - en helt annorlunda materialitet. De olika estetiska och flygdynamiska egenskaperna hos dessa maskiner kräver att designers omprövar designutrymmet för denna typ av drönare. Denna studie syftar till att kartlägga det preliminära designutrymmet för ornithoptorer och utforska deras intressanta flygdynamik och materialkvaliteter. Deltagare var inbjudna till en workshop för att bygga och flyga tre olika ornithoptar och för att observera deras upplevelse att flyga med dem. Detta arbete omfattar ett antal insikter om ornithoptar, speciellt deras unika materialitet. De unika material som används i ornithoptar, såsom balsaträ, polystyren, nylon och kolfiber, tillåter de att flyga mera effektivt och motstå krafterna i flygningen. Slutligen argumenterar jag att designers kan ta tillvara designutrymmet av ornithoptar genom att skapa egenskaper som amplifierar de unika och oförutsägbara rörelserna av maskinerna, vilket skulle leda till nya och innovativa designer. Detta skulle bidra till en hyllning av icke uniformitet av morfologier och rörelser i ett ekosystem av biologiskt inspirerade flygande robotar

<p dir="ltr">The vagus nerve (VN) is the tenth cranial nerve that mediates most of the parasympathetic functions of the autonomic nervous system. The axons of the human VN comprise a mix of unmyelinated and myelinated axons, where ~80% of the axons are unmyelinated C fibers (Havton et al., 2021). Understanding that most VN axons are unmyelinated, there is a need to map the pathways of these axons to and from organs to understand their function(s) and whether C fiber morphology or signaling characteristics yield insights into their functions. Developing a machine learning model that detects and predicts the morphology of VN single fiber action potentials based on select fiber characteristics, e.g., diameter, myelination, and position within the VN, allows us to more readily categorize the nerve fibers with respect to their function(s). Additionally, the features of this machine learning model could help inform peripheral neuromodulation devices that aim to restore, replace, or augment one or more specific functions of the VN that have been lost due to injury, disease, or developmental abnormalities.</p><p dir="ltr">We designed and trained four types of Multi-layer Perceptron Artificial Deep Neural Networks (MLP-ANN) with 10,000 rat abdominal vagal C-fibers simulated via the peripheral neural interface model ViNERS. We analyze the accuracy of each MLP-ANN’s SFAP predictions by conducting normalized cross-correlation and morphology analyses with the ViNERS C-fiber SFAP counterparts. Our results showed that our best MLP predicted over 94% of the C-fiber SFAPs with strong normalized cross-correlation coefficients of 0.7 through 1 with the ViNERS SFAPs. Overall, this novel tool can use a C-fiber’s biophysical characteristics (i.e., fiber diameter size, fiber position on the x/y axis, etc.) to predict C-fiber SFAP morphology.</p>

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Die Potentiale der gefrorenen Sandschalung für den Entwurf und die Herstellung funktional gradierter Betonbauteile (siehe Projekte Sobek et al. und Garrecht et al. des SPP 1542, S. 642 ff . und S. 250 ff .) wurden im Rahmen des Teilprojekts B04: Herstellung biomimetischer und biologisch inspirierter (modularer) Strukturen für die Bauindustrie des Sonderforschungsbereichs/Transregio 141 Biologischer Entwurf und integrative Strukturen – Analyse, Simulation und Umsetzung in der Architektur weiter untersucht. / Potentials of frozen sand formwork technology were further investigated in design and production of functionally graded concrete components (see also the projects Sobek et al. and Garrecht et al. of SPP 1542, pages 642 resp. 250 et seq.) in the subproject B04: Fabrication of biomimetic and biologically inspired (modular) structures for use in the construction industry in the framework of the Collaborative Research Centre/Transregio 141 Biological Design and Integrative Structures – Analysis, Simulation and Implementation in Architecture.