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Coconuts are one of nature’s toughest lignocellulosic materials, possessing a fracture toughness on par with dentin and a compressive strength ten times that of bamboo. The coconut’s hierarchical structure has been characterized before, except prior studies left out one key aspect, the smallest length scales, approaching the molecular level. Here we exfoliate the hard shell of Cocos nucifera, revealing the true cellular organization and the dimensions of the crystalline cellulose nanofibrils found in the cell walls. After chemical pretreatments, we found entanglement between elongated sclereid cells that was not visible in the untreated coconut shell. This may contribute to the mechanical performance of the endocarp; it also utilizes elongated, high-aspect ratio structural elements at the cellular level, in addition to the nanofibrillar level previously known. Compared to other wood-like materials, the cellulose nanofibrils were shorter and represented a smaller weight fraction. This reduced length and the lower filler-to-matrix ratio could be the optimal lignocellulosic nanostructure for tough biomaterials. These newly discovered unique features explain how the endocarp of Cocos nucifera mechanically outperforms materials consisting of the same molecular components. 

Raw data of optical microscopy (OM), field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and data analysis. The data is organized by the figure numbers used in the manuscript, in the order of appearance. This organization is best seen if viewed in the "Tree" mode. File Formats * AFM raw data is provided in NT-MDT's proprietary format (MDT) as well as Gwyddion format (GWY), which can both be viewed using the Gwyddion AFM viewer, which has been released under the GNU public software license GPLv3 and can be downloaded for free at http://gwyddion.net/. * AFM line profile raw data is provided in plain text ASCII (TXT) format. * XRD raw data is provided in plain text ASCII (TXT) format. * FE-SEM raw data always has the SEM image data, provided in TIF format, along with a parameter file produced by the SEM instrument in plain text ASCII (TXT). * Optical microscopy raw data is provided in PNG format. * Data analysis results of nanofibril dimensions are provided in an Excel sheet (XLSX). Data (Folder Structure) Figure 1 * FE-SEM raw data and PNG file from optical microscopy of the coconut. Figure 2 * FE-SEM raw data of all images of the coconut. Figure 3 * MDT and GWY files of all AFM scans of the exfoliated coconut cellulose. Lengths of crystalline nanofibrils were determined manually by running a line profile longitudinally across each nanofibril and determining its end-to-end length, ignoring any bends or kinks. The results of this procedure are shown in an XLSX file (column A). Other columns of this spread sheet contain the number average (B), its standard deviation (C), the sum of lengths (D), and the length weights (E) used to calculate the length-weighted average (G). Figure 4 * MDT and GWY file of the exfoliated coconut cellulose AFM scans. TXT files from XRD and line profile of AFM image. 

Raw data of optical microscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), force spectroscopy, and data analysis. File Formats * AFM and force spectroscopy raw data, is provided in NT-MDT's proprietary format (MDT) as well as Gwyddion format (GWY), which can both be viewed using the Gwyddion AFM viewer, which has been released under the GNU public software license GPLv3 and can be downloaded for free at http://gwyddion.net/ * FE-SEM and TEM raw data is provided in TIF format * Optical microscopy is provided in PNG format * Data analysis is provided in an excel sheet (XLSX) Data (Folder Structure) Figure 1 * All TIF files (with accompanying TXT files) from FE-SEM and PNG files from optical microscopy of the cribellate silk structure from the K. hibernalis. Figure 2 * All TIF files from TEM, TIF files (with accompanying TXT files) from FE-SEM, MDT and GWY files from AFM of the cribellate silk nanofibrils. Figure 3 + S3 * MDT and GWY files from AFM and force spectroscopy of the cribellate silk nanofibrils as well as the hard substrate and holes within the substrate. XLSX file containing data analysis process with descriptive boxes of what each row does. Figure S4 * MDT and GWY files from AFM and force spectroscopy of the cribellate silk nanofibrils. 

Abstract Cribellate silks, produced by ancient spiders, are fascinating because they feature a highly sophisticated, 3D hierarchical structure consisting of filaments with different diameters and shapes. Here, the smallest and thinnest constituents of the cribellate silk are investigated: nanofibrils that form a dense mesh that is supported by larger fibers. Analysis of their structure via atomic force and transmission electron microscopies shows that they are flattened fibrils, only ≈5 nm thick — thinner than any other natural spider silk fibrils previously reported. In this work, the first mechanical tensile testing experiments on these fibrils are carried out, which reveals that the fibrils show an outstanding extensibility of at least 1100%, almost twice as much as the most stretchable spider silk previously reported. Based on these extraordinary findings, this work significantly expands the parameter space of materials properties attainable by spider silks and provides further insights into their nanomechanics. 

Spider silk is biocompatible, biodegradable, and rivals some of the best synthetic materials in terms of strength and toughness. Despite extensive research, comprehensive experimental evidence of the formation and morphology of its internal structure is still limited and controversially discussed. Here, we report the complete mechanical decomposition of natural silk fibers from the golden silk orb-weaver Trichonephila clavipes into ≈10 nm-diameter nanofibrils, the material's apparent fundamental building blocks. Furthermore, we produced nanofibrils of virtually identical morphology by triggering an intrinsic self-assembly mechanism of the silk proteins. Independent physico-chemical fibrillation triggers were revealed, enabling fiber assembly from stored precursors “at-will”. This knowledge furthers the understanding of this exceptional material's fundamentals, and ultimately, leads toward the realization of silk-based high-performance materials.