Animal muscle represents a mechanically advantageous natural material, composed of sequence-diverse yet largely unexplored protein domains that offer inspiration for novel biomaterial design. Of those, Immunoglobulin (Ig) domains display unique properties of high self recovery and energy absorption, presenting a superior alternative to conventional protein-based materials. In this study, we fabricated and characterized fibers using recombinant Ig domains derived from various structural proteins. Among them, filamin Ig fibers demonstrated the highest ultimate tensile strength and toughness, surpassing many natural and synthetic materials. Our findings indicate that hydrophobic interactions play a key role in enhancing mechanical performance, as evidenced by a strong correlation between Ig domain hydrophobicity and fiber strength. Furthermore, Ig fibers retained over 80% of their length and strength after prolonged exposure to high humidity, highlighting their exceptional moisture resistance. Cyclic loading/unloading experiments revealed high damping capacity and excellent shape recovery, driven by the unfolding-refolding mechanism of Ig domains. The ability to tailor Ig domain sequences through synthetic biology further enables fine-tuning of fiber properties to meet specific application requirements. With their superior mechanical performance, moisture resistance, and energy-damping capabilities, recombinant Ig domain-based fibers hold significant promise for diverse applications in biomedicine, textiles, and advanced materials.
