Hydro-Torsional Compaction for Scalable Production of Aramid Nanofiber Threads with Densely Assembled Double-Helical...

Synthetic replication of biological materials like spider silk, cellulose, and collagen remains challenging owing to the entropic cost of aligning high-aspect-ratio chains into compact, load-bearing structures. These barriers cause misalignment, voids, and poor inter-fiber cohesion in macroscale materials. We report a scalable strategy for producing high-strength thread from poly(2,2'-disulfonyl-4,4'-benzidine terephthalamide) (PBDT), a rigid-chain aramid that forms double-helical supramolecular units, which further organize into nanofiber networks. Continuous PBDT threads are fabricated while retaining the solution-phase double-helix structure, enabling production over hundreds of meters. These nanofibers are processed into macroscale threads through wet-spinning and hydro-torsional compaction, which promotes densification and enhances inter-fiber contact. This hierarchical processing sequence yields compact, aligned fibers with improved structural coherence, supporting efficient interfacial load transfer and resulting in a tensile strength of 1.2 GPa and a Young's modulus of 103 GPa, corresponding to 5.8-fold and 6.3-fold improvements over bulk PBDT films, respectively. Among synthetic nanofibrous materials assembled in aqueous media, these threads demonstrate superior mechanical properties, with tensile strengths approaching those of spider silk. This study establishes a scalable framework for constructing high-strength, hierarchically organized aramid threads for aligned, robust architectures, ion-mediated transport pathways, and charged bioinspired systems.