Engineering Silk and Silk-like Proteins into High-Performance Fiber Materials

Silk and silk-like proteins emerge as programmable building blocks for high-performance fiber materials because they can integrate mechanical robustness, biological compatibility, environmental responsiveness, and degradability within genetically defined polymers. Synthetic biology now enables precise control over protein sequence, repeat number, molecular weight, and modular architecture, creating opportunities to design fibers beyond naturally harvested silks. However, application-ready protein fibers require coordinated control across multiple length scales, from sequence-encoded motifs and molecular assembly to spinning-induced alignment, hierarchical network formation, and final property profiles. This review discusses recent advances in engineering silk and silk-like proteins into mechanically and functionally optimized fibers. We highlight how crystallite-forming motifs, amorphous domains, terminal domains, and folded or dynamic modules contribute to fiber strength, toughness, extensibility, damping, shape recovery, humidity stability, biodegradation, and recyclability. We further connect these sequence–structure–property relationships to applications in structural textiles, biomedical fibers, smart and protective systems, and sustainable materials. Finally, we discuss future opportunities in scalable recombinant production and data-driven sequence design. These advances are expected to accelerate the translation of engineered protein fibers into practical high-performance materials.