Self-strengthening tape junctions inspired by recluse spider webs

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.