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Adhesive tapes are versatile and widely used yet lack adhesion strength due to their tendency to fail via peeling, a weak failure mode. A tape with surprising adhesive properties is the recluse spider's 50 nm-thin silk ribbon with a 1 : 150 aspect ratio. Junctions of these microscopic sticky tapes can withstand the material's tensile failure stress of ≈1 GPa. We modeled these natural tape–tape junctions and revealed a bi-modal failure behavior, critically dependent on the two tapes’ intersection angle. One mode leads to regular, low-strength peeling failure, while the other causes the junction to self-strengthen, eliminating the inherent weakness in peeling. This self-strengthening mechanism locks the two tapes together, increasing the junction strength by 550% and allowing some junctions to remain intact after tensile failure. This impressive adhesive strength of tapes has never before been observed or predicted. We found that recluse spiders make tape junctions with pre-stress to force the locked, high-strength failure mode. We used this approach to make junctions with synthetic adhesive tapes that overcame the weak peeling failure. 

The raw data for the associated manuscript is organized here into three categories: 1) relating to the measurement and analysis of the native recluse spiders loop junctions, 2) raw images found in the figures throughout the manuscript, and 3) relating to the experiments testing the effect that junction angle has on the strength of two intersecting tapes. It is recommended to browse the data files in Tree mode, which will make the files appear in folders reflecting this organization. 1) Loxosceles Loop Junction Images and Analysis The folder titled, SEM Raw Images, has all of the scanning electron microscopy (SEM) images taken of the native recluse loop junctions. Some images are close-ups of individual junctions and others take a broader perspective (macro) of many loop junctions in series. Where possible several close-up images of the individual junctions are accompanied with a macro image. These images were imported into ImageJ where the junction angle was measured. The measurements for all 41 loop junctions observed are in the folder titled, Raw Data Files in the file titled, Loxosceles Loop Junction Angle Measurements.txt. The folder titled, Raw Data Files contains, in addition to the angle measurements, the raw data for analyzing the strength of individual loop junctions. The data is in native MATLAB data format. These datasets include the complete tensile data and the cross-sectional area data for each spiders silk. The MATLAB code titled, Figure_2A_2B_code, processes the raw tensile data from the natural recluse spiders loop junctions. This data is plotted as two representative curves in Figure 2A and as a complete set as a histogram in Figure 2B. The MATLAB code titled, Figure_7_code, processes and plots the loop junction data found in, Loxosceles Loop Junction Angle Measurements.txt and executed the model of a random set of recluse loops. This code can be executed to generate Figure 7. The folder titled, Raw Data Files, must be open in MATLAB to run this code! This code uses the MATLAB function, areacalculation, to calculate the junction area for a given junction angle. 2) Raw Images This folder is organized by the respective figure in the manuscript where each image can be found. Additional metadata for each image can be found accompanying each image. 3) Tensile Data and Analysis This folder contains all of the raw tensile data for all tape-tape junction experiments conducted. All of the tensile data is in the folder titled, Raw Data Test Files. Within this folder is a .txt file for each sample tested. The file names are critical to the figure codes working properly because they contain the information for the junction angle and iterations. The file names are in the format year-month-day_trialnumber_junctionangle.txt. Also in the Raw Data Test Files folder are two functions used within some of the figure codes: fbfill and areacalculation. These functions will be used in the figure codes to properly analyze the data. To generate any figure using the MATLAB code in this folder, first open the code in MATLAB. Then within MATLAB, open the folder Raw Data Test Files. Only with this folder open in MATLAB will the code be able to find the correct raw data .txt files. The rest of the contents of this folder are MATLAB codes for specific figures in the manuscript. The only exception to this is the code titled, surfaceenergy_code, which is executed to calculate the phenomenological surface energy for the tapes used in these experiments.