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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. 

Raw data of optical microscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and diameter measurements of the exfoliated and self-assembled nanofibrils for our manuscript. File Formats AFM raw data is provided in Gwyddion format, which can be viewed using the Gwyddion AFM viewer, which has been released under the GNU public software licence GPLv3 and can be downloaded free of charge at http://gwyddion.net/ Optical microscopy data is provided in JPEG format SEM raw data is provided in TIFF format Data analysis codes were written in MATLAB (https://www.mathworks.com/products/matlab) and stored as *.m files Data analysis results were stored as MATLAB multidimensional arrays (MATLAB “struct” data format, *.mat files) Data (Folder Structure) The data in the dataverse is best viewed in Tree mode. ReadMe.md This description in Markdown format. Figure 2 - Microscopy Raw Data Figure 2 - panel a.jpg (7.2 MB) Optical micrograph (JPEG format) Figure 2 - panel b.jpg (6.1 MB) Optical micrograph (JPEG format) Figure 2 - panel c f.tif (1.2 MB) SEM raw data (TIFF format) Figure 2 - panel d.tif (1.2 MB) SEM raw data (TIFF format) Figure 2 - panel e - Exfoliated Fibrils.gwy (32.0 MB) AFM raw data (Gwyddion format) Figure 3 - AFM Raw Data Figure 3 - Panel a - Exfoliated fibrils.gwy (81.5 MB) AFM raw data (Gwyddion format) Figure 3 - Panel c - Self-assembled fibrils.gwy (24.0 MB) AFM raw data (Gwyddion format) Figure 3 - Diameter Measurements Figure 3a and Figure 3c show the AFM images of exfoliated and self-assembled nanofibrils, respectively. However, due to the AFM tip-induced broadening of lateral dimensions of small features (such as nanofibrils), the diameters of nanofibrils are generally overestimated in AFM images. Hence, the diameters of the nanofibrils were estimated as the full width at half maximum (FWHM) value of line scans taken over nanofibrils perpendicular to their axial direction. Line profiles were taken at multiple locations using Gwyddion, and the raw data were stored in MATLAB struct files (lineProfileData_Exfoliated.mat and lineProfileData_Self-Assembled.mat). These data files can be directly imported into MATLAB and will appear as “DataExf” and “DataSA” in MATLAB workspace. For instance, “DataExf.x{i}” contains the x-axis data of i-th line profile, and “DataExf.y{i}” contains the y-axis data of i-th line profile. The MATLAB codes MainCode_Exf.m and MainCode_SA.m are used to fit Gaussian curves for each line profile and calculate the FWHM. The *.m files for functions gaussian.m and createFit.m must be in the same folder as the file for the main code. The main code generates figures for each line profile containing raw line profile, related Gaussian fit, and FWHM. These FWHM values are considered as the diameters of the fibrils and stored in variables called “Exf_Dia” and “SA_Dia”. Finally, these values are plotted in a histogram and calculate the statistics such as the mean and the standard deviation. Exfoliated createFit.m (1.1 KB) MATLAB code file (see above) gaussian.m (134 B) MATLAB code file (see above) lineProfileData_Exfoliated.mat (11.7 KB) Line profiles for exfoliated nanofibrils (MATLAB struct format) MainCode_Exf.m (1.8 KB) MATLAB code file (see above) Line profile raw data - Exfoliated Folder with all corresponding cross section raw data in ASCII format Self Assembled createFit.m (1.1 KB) MATLAB code file (see above) gaussian.m (134 B) MATLAB code file (see above) lineProfileData_Self-Assembled.mat (9.9 KB) Line profiles for self-assembled nanofibrils (MATLAB struct format) MainCode_SA.m (1.8 KB) MATLAB code file (see above) Line profile raw data - SelfAssembled Folder with all corresponding cross section raw data in ASCII format Figure 4 - AFM Raw Data Figure 4 - Panal a.gwy (73.4 MB) AFM raw data (Gwyddion format) Figure 4 - Panel e.gwy (42.0 MB) AFM raw data (Gwyddion format)