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Fritz Vollrath - One of the best experts on this subject based on the ideXlab platform.
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comparing the microstructure and mechanical properties of bombyx mori and antheraea pernyi cocoon composites
Acta Biomaterialia, 2017Co-Authors: Juan Guan, Wenshu Zhu, Binghe Liu, Kang Yang, Fritz VollrathAbstract:Abstract Silkworm cocoon material is a natural composite consisting of silk fibres and sericin glues. Both domestic and wild silkworms produce Cocoons but with different functionality – one selected by man for textile manufacture whereas the other selected by Nature to provide damage-tolerant housing. To understand the structure-–property relationship of Cocoons, we evaluated and compared the microstructure and mechanical properties of two representative cocoon walls. It appears that a “brittle and weak” composite is produced by domestic Bombyx mori (B. mori) while a “tough and strong” composite is made by wild Antheraea pernyi (A. pernyi). The superior mechanical performance of A. pernyi Cocoons can be attributed to both the material properties and the fibre network microstructures. Failure mechanisms and different failure modes for cocoon fibre composites were also proposed. A finite element model revealed qualitatively the effect of fibre properties and inter-fibre bonding strength on the mechanical properties of the fibre network. It emerged that both good mechanical properties of fibres and robust inter-fibre bonding were required for tough and strong fibre composites. The new insights could inspire new designs of synthetic fibre composites with enhanced mechanical properties. Statement of Significance Natural Cocoons are an important group of natural fibre composites with versatile functionalities. Previous studies have focused on the diversity of cocoon species and different morphological and mechanical features. It was suggested that the cocoon network structure determined the final mechanical properties of the cocoon composite. Nevertheless, the full structure–propertyfunction relationships for the cocoon composite are not understood. By studying two distinct cocoon species with specific functionalities, we prove that the mechanical properties of two Cocoons are determined by both network properties and fibre properties. A robust fibre network is the prerequisite, within which the good mechanical properties of the fibres can play a part. The finding will inspire new designs of synthetic composites with desirable and predictable mechanical properties.
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the silkmoth cocoon as humidity trap and waterproof barrier
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2013Co-Authors: Nicholas P C Horrocks, Fritz Vollrath, Cedric DickoAbstract:To better understand how silkmoth Cocoons maintain the correct internal moisture levels for successful pupation, we examined Cocoons from the long-domesticated mulberry silkmoth Bombyx mori as well as from two wild silkmoth species, Antheraea pernyi and Philosamia cynthia ricini. We determined fluid-independent values for the porosity, tortuosity and permeability of the inner and outer surfaces of Cocoons. Permeabilities were low and, with the exception of A. pernyi Cocoons, inner surfaces were less permeable than outer surfaces. B. mori Cocoons exhibited the highest permeability overall, but only at the outer surface, while A. pernyi Cocoons appeared to show different patterns from the other species tested. We discuss our findings in light of the ecophysiology of the various species and propose a 'tortuous path' model to help explain our results. The model describes how the structure of the inner and outer layers of the cocoon allows it to function as both a humidity trap and a waterproof barrier, providing optimum conditions for the successful development of the pupa.
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Structure and physical properties of silkworm Cocoons.
Journal of the Royal Society Interface, 2012Co-Authors: Fujia Chen, David Porter, Fritz VollrathAbstract:Silkworm Cocoons have evolved a wide range of different structures and combinations of physical and chemical properties in order to cope with different threats and environmental conditions. We present our observations and measurements on 25 diverse types of Cocoons in a first attempt to correlate physical properties with the structure and morphology of the Cocoons. These two architectural parameters appear to be far more important than the material properties of the silk fibres themselves. We consider tensile and compressive mechanical properties and gas permeation of the cocoon walls, and in each case identify mechanisms or models that relate these properties to cocoon structure, usually based upon non-woven fibre composites. These properties are of relevance also for synthetic non-woven composite materials and our studies will help formulate bio-inspired design principles for new materials.
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Morphology and structure of silkworm Cocoons
Materials Science and Engineering: C, 2012Co-Authors: Fujia Chen, David Porter, Fritz VollrathAbstract:Abstract Silkworm Cocoons are natural polymer fibre composites made from silk fibres and sericin binder. While silk is an interesting natural material per se , an understanding of the role of silk within one of its main functional applications in silkworm Cocoons will provide inspiration and tools for the design of new artificial silk composites. Here, we describe in some detail the structure and morphology of the Cocoons of 27 different species of silkworm. While cocoon morphology can be described very broadly as a nonwoven fibre composite, we demonstrate a diversity of structural features such as: the number and connectivity of layers through the cocoon wall thickness, the amount and distribution of sericin binder, the diameter and packing density of the silk fibres, the degree of orientation of the nonwoven structure, the distribution of larger holes within that structure, and the presence of calcium oxalate crystals.
Xungai Wang - One of the best experts on this subject based on the ideXlab platform.
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natural and highly protective composite structures wild silkworm Cocoons
Composites Communications, 2017Co-Authors: Jin Zhang, Jasjeet Kaur, Xing Jin, Xungai WangAbstract:Abstract Wild silkworm Cocoons are thin and lightweight composite structures that provide silkworms with excellent protection against extreme temperature and other harsh weather conditions (e.g. UV, wind, rain). Understanding such natural composite structures will provide bio-inspiration for developing highly protective and light-weight fibrous materials and structures. This paper highlights our recent research on the mechanical and thermal properties, moisture transfer behaviour, and UV resistance of wild silkworm Cocoons, in comparison with the domestic Bombyx mori silkworm cocoon. Wild silkworm Cocoons such as Antheraea pernyi exhibit exceptionally high toughness, excellent thermal buffer, directional moisture transfer and strong UV resistance, all of which contribute to the high-level protection of the silkworm pupa in harsh outdoor environments.
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Facts and myths of antibacterial properties of silk
Biopolymers, 2013Co-Authors: Jasjeet Kaur, Rangam Rajkhowa, Tarannum Afrin, Takuya Tsuzuki, Xungai WangAbstract:Silk Cocoons provide protection to silkworm from biotic and abiotic hazards during the immobile pupal phase of the lifecycle of silkworms. Protection is particularly important for the wild silk Cocoons reared in an open and harsh environment. To understand whether some of the cocoon components resist growth of microorganisms, in vitro studies were performed using gram negative bacteria Escherichia coli (E. coli) to investigate antibacterial properties of silk fiber, silk gum, and calcium oxalate crystals embedded inside some Cocoons. The results show that the previously reported antibacterial properties of silk Cocoons are actually due to residues of chemicals used to isolate/purify cocoon elements, and properly isolated silk fiber, gum, and embedded crystals free from such residues do not have inherent resistance to E. coli. This study removes the uncertainty created by previous studies over the presence of antibacterial properties of silk Cocoons, particularly the silk gum and sericin.
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silkworm cocoon as natural material and structure for thermal insulation
Materials & Design, 2013Co-Authors: Jin Zhang, Rangam Rajkhowa, X Y Liu, Xungai WangAbstract:Silkworm Cocoons are important biological materials that protect silkworms from environmental threat and predator attacks. Silkworm Cocoons are able to provide significant buffer against temperature changes outside of the cocoon structure. We present our investigation of the thermal insulation properties of both domestic and wild silkworm Cocoons under warm conditions. Wild Cocoons show stronger thermal buffer function over the domestic cocoon types. Both the cocoon walls and the volume of inner cocoon space contribute to the thermal damping behaviour of Cocoons. Wild silkworm Cocoons also have lower thermal diffusivity than domestic ones. Calcium oxalate crystals affects the thermal behaviour of wild silkworm Cocoons, by trapping still air inside the cocoon structure and enhancing the thermal stability of the cocoon assembly. The research findings are of relevance to the bio-inspired design of new thermo-regulating materials and structures.
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Mechanical properties and structure of silkworm Cocoons: A comparative study of Bombyx mori, Antheraea assamensis, Antheraea pernyi and Antheraea mylitta silkworm Cocoons
Materials science & engineering. C Materials for biological applications, 2013Co-Authors: Jin Zhang, Rangam Rajkhowa, X Y Liu, Jasjeet Kaur, Xungai WangAbstract:Abstract As a protective shell against environmental damage and attack by natural predators, the silkworm cocoon has outstanding mechanical properties. In particular, this multilayer non-woven composite structure can be exceptionally tough to enhance the chance of survival for silkworms while supporting their metabolic activity. Peel, out-of-plane compression and nano-indentation tests and micro-structure analysis were performed on four types of silkworm cocoon walls (domesticated Bombyx mori, semi-domesticated Antheraea assamensis and wild Antheraea pernyi and Antheraea mylitta silkworm Cocoons) to understand the structure and mechanical property relationships. The wild silkworm Cocoons were shown to be uniquely tough composite structures. The maximum work-of-fracture for the wild Cocoons (A. pernyi and A. mylitta) was approximately 1000 J/m2, which was almost 10 times the value for the domesticated cocoon (Bombyx mori) and 3 ~ 4 times the value for the semi-domesticated cocoon (A. assamensis). Calcium oxalate crystals were found to deposit on the outer surfaces of the semi-domesticated and wild Cocoons. They did not show influence in enhancing the interlaminar adhesion between cocoon layers but exhibited much higher hardness than the cocoon pelades.
Fangyin Dai - One of the best experts on this subject based on the ideXlab platform.
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Enhanced thermal and mechanical properties of natural silkworm cocoon composites constructed by multi-silkworm larvae simultaneously
Materials Letters, 2019Co-Authors: Lan Cheng, Xiaoling Tong, Zulan Liu, Sihao Chen, Yu Bao, Li-zhi Gao, Fangyin DaiAbstract:Abstract In this study, we developed a simple route to fabricate natural silkworm cocoon composites with dense fiber networks and low porosities. The thermal and mechanical properties of these modified Cocoons are significantly improved. Especially, the tensile strength, elongation, toughness and the average peeling force of the cocoon constructed by three silkworm larvae simultaneously are found to be 1.7, 1.5, 2.1 and 2.1 times higher than those of the normal cocoon, respectively. These special Cocoons with good mechanical properties could be applied to produce high-performance artificial cocoon composites, biomimetic and ballistic materials.
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Natural Silkworm Cocoon Composites with High Strength and Stiffness Constructed in Confined Cocooning Space.
Polymers, 2018Co-Authors: Lan Cheng, Xiaoling Tong, Hong-ping Zhao, Zulan Liu, Huiming Huang, Fangyin DaiAbstract:In this study, using round paper tubes (PTs) and rectangular cardboard boxes (CBs) as external constraints to control the size of the cocooning space, we fabricated a series of modified silkworm Cocoons (PT Cocoons and CB Cocoons). Their microstructures, morphologies, compositions, and mechanical properties were characterized and compared with normal silkworm Cocoons. These two kinds of modified silkworm Cocoons exhibit dense and homogeneous layer structures. Tensile test results indicate that above a size limit of cocooning space, their tensile strengths, Young's moduli, and strain energy densities increase with the decrease in cocooning space. Especially in comparison with the normal Cocoons, the tensile strength and Young's modulus of the PT-14 cocoon increase by 44% and 100%, respectively. Meanwhile, PT Cocoons and CB Cocoons, except PT-12, also possess better peeling resistance than normal Cocoons. Owing to the dense structure and low porosity, the modified Cocoons form robust fiber networks that result in high strength and toughness. This study provides a green and efficient method to fabricate mechanically enhanced silkworm Cocoons with special shapes and dense layer structures. The method can be easily subjected to further modification processes and has potential applications in the production of high-performance green cocoon composites and biomimetic materials.
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Evaluation of artificial skin made from silkworm Cocoons
Journal of Materials Science, 2017Co-Authors: Guangqian Lan, Jiawei Liu, Jinghao Chen, Fangyin DaiAbstract:The protective characteristics of silkworm Cocoons are the result of thousands of years of evolution. In this study, we attempted to combine the cocoon’s protective characteristics with the function of human skin to explore the possibility of using silkworm Cocoons in the field of artificial skin application. We retained the natural structure of the cocoon shells and softened it by a degumming process. This process was performed so that the mechanical and permeation properties of the cocoon material meet the criteria of artificial skin with respect to tension and suturing; the cocoon material was also found to have strong antibacterial activity and cell compatibility. These properties of the cocoon suggest that it has a high potential to be used as an artificial skin. Overall, we expect the silkworm cocoon to be a type of biological material with extensive possibilities of application as artificial skin.
Jin Zhang - One of the best experts on this subject based on the ideXlab platform.
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natural and highly protective composite structures wild silkworm Cocoons
Composites Communications, 2017Co-Authors: Jin Zhang, Jasjeet Kaur, Xing Jin, Xungai WangAbstract:Abstract Wild silkworm Cocoons are thin and lightweight composite structures that provide silkworms with excellent protection against extreme temperature and other harsh weather conditions (e.g. UV, wind, rain). Understanding such natural composite structures will provide bio-inspiration for developing highly protective and light-weight fibrous materials and structures. This paper highlights our recent research on the mechanical and thermal properties, moisture transfer behaviour, and UV resistance of wild silkworm Cocoons, in comparison with the domestic Bombyx mori silkworm cocoon. Wild silkworm Cocoons such as Antheraea pernyi exhibit exceptionally high toughness, excellent thermal buffer, directional moisture transfer and strong UV resistance, all of which contribute to the high-level protection of the silkworm pupa in harsh outdoor environments.
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silkworm cocoon as natural material and structure for thermal insulation
Materials & Design, 2013Co-Authors: Jin Zhang, Rangam Rajkhowa, X Y Liu, Xungai WangAbstract:Silkworm Cocoons are important biological materials that protect silkworms from environmental threat and predator attacks. Silkworm Cocoons are able to provide significant buffer against temperature changes outside of the cocoon structure. We present our investigation of the thermal insulation properties of both domestic and wild silkworm Cocoons under warm conditions. Wild Cocoons show stronger thermal buffer function over the domestic cocoon types. Both the cocoon walls and the volume of inner cocoon space contribute to the thermal damping behaviour of Cocoons. Wild silkworm Cocoons also have lower thermal diffusivity than domestic ones. Calcium oxalate crystals affects the thermal behaviour of wild silkworm Cocoons, by trapping still air inside the cocoon structure and enhancing the thermal stability of the cocoon assembly. The research findings are of relevance to the bio-inspired design of new thermo-regulating materials and structures.
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Mechanical properties and structure of silkworm Cocoons: A comparative study of Bombyx mori, Antheraea assamensis, Antheraea pernyi and Antheraea mylitta silkworm Cocoons
Materials science & engineering. C Materials for biological applications, 2013Co-Authors: Jin Zhang, Rangam Rajkhowa, X Y Liu, Jasjeet Kaur, Xungai WangAbstract:Abstract As a protective shell against environmental damage and attack by natural predators, the silkworm cocoon has outstanding mechanical properties. In particular, this multilayer non-woven composite structure can be exceptionally tough to enhance the chance of survival for silkworms while supporting their metabolic activity. Peel, out-of-plane compression and nano-indentation tests and micro-structure analysis were performed on four types of silkworm cocoon walls (domesticated Bombyx mori, semi-domesticated Antheraea assamensis and wild Antheraea pernyi and Antheraea mylitta silkworm Cocoons) to understand the structure and mechanical property relationships. The wild silkworm Cocoons were shown to be uniquely tough composite structures. The maximum work-of-fracture for the wild Cocoons (A. pernyi and A. mylitta) was approximately 1000 J/m2, which was almost 10 times the value for the domesticated cocoon (Bombyx mori) and 3 ~ 4 times the value for the semi-domesticated cocoon (A. assamensis). Calcium oxalate crystals were found to deposit on the outer surfaces of the semi-domesticated and wild Cocoons. They did not show influence in enhancing the interlaminar adhesion between cocoon layers but exhibited much higher hardness than the cocoon pelades.
Fujia Chen - One of the best experts on this subject based on the ideXlab platform.
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Structure and physical properties of silkworm Cocoons.
Journal of the Royal Society Interface, 2012Co-Authors: Fujia Chen, David Porter, Fritz VollrathAbstract:Silkworm Cocoons have evolved a wide range of different structures and combinations of physical and chemical properties in order to cope with different threats and environmental conditions. We present our observations and measurements on 25 diverse types of Cocoons in a first attempt to correlate physical properties with the structure and morphology of the Cocoons. These two architectural parameters appear to be far more important than the material properties of the silk fibres themselves. We consider tensile and compressive mechanical properties and gas permeation of the cocoon walls, and in each case identify mechanisms or models that relate these properties to cocoon structure, usually based upon non-woven fibre composites. These properties are of relevance also for synthetic non-woven composite materials and our studies will help formulate bio-inspired design principles for new materials.
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Morphology and structure of silkworm Cocoons
Materials Science and Engineering: C, 2012Co-Authors: Fujia Chen, David Porter, Fritz VollrathAbstract:Abstract Silkworm Cocoons are natural polymer fibre composites made from silk fibres and sericin binder. While silk is an interesting natural material per se , an understanding of the role of silk within one of its main functional applications in silkworm Cocoons will provide inspiration and tools for the design of new artificial silk composites. Here, we describe in some detail the structure and morphology of the Cocoons of 27 different species of silkworm. While cocoon morphology can be described very broadly as a nonwoven fibre composite, we demonstrate a diversity of structural features such as: the number and connectivity of layers through the cocoon wall thickness, the amount and distribution of sericin binder, the diameter and packing density of the silk fibres, the degree of orientation of the nonwoven structure, the distribution of larger holes within that structure, and the presence of calcium oxalate crystals.
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Silk Cocoons as composites
2011Co-Authors: Fujia ChenAbstract:This thesis looks at the engineering aspects of silkworm Cocoons as a structural biological composite system. A wide range of species of silk Cocoons were studied for their morphologies, physical properties and mechanical behaviour. A silk cocoon can be described very broadly as a nonwoven fibre composite made of silk fibres bonded by sericin binder, although the a variety of species can show a diversity of structural features of the layers, porosity, degree of orientation, binding density and presence of crystals etc. These structural differences lead to diverse cocoon mechanical behaviour. Tensile and compressive properties of Cocoons are tested and linked to their individual interfibre bonding, connectivity and density. Gas diffusion through the cocoon walls is controlled by the combination of thickness and density. In addition, a physically realistic quantitative model is developed, which links directly the structure and mechanical properties of silk Cocoons. The gradual loss of connectivity of the interfibre bonding is the key mechanism for the deformation of Cocoons. It can be quantified as a strain activated function of the bonding up to a failure criterion, where either a percolation threshold of 50% of these bonds or the failure stress of the binder arrives. For Bombyx mori cocoon, which has a graded-layer structure, the model was enhanced to include the contribution of interlayer and intralayer bonding in the system. This model can also be applied to other nonwoven fibre and particulate composites using a small number of physically realistic model parameters, and will be a valuable ‘bioinspired’ tool for the development of new composite systems. Based on the understanding of structure-mechanical property relationships in silkworm Cocoons, an engineering approach was used for examining cocoon as an impact resistant structural material that provides mechanical protection from environmental threats. In addition, silk Cocoons were used as a nonwoven reinforcement to develop an engineering composite by increasing the connectivity (more binder) in the cocoon. Using polyurethane or regenerated silk fibroin of medium concentration can increase the toughness of Cocoons, and epoxy or regenerated silk fibroin of high concentration binding leads to a brittle system.