Bidirectional Phase Transition of Silk Fibroin for Robust Ternary Information Processing

Ternary information processing offers higher data density and improved efficiency compared with binary systems. However, its practical implementation remains limited by the difficulty of defining stable, well-separated states and achieving scalable fabrication. Here, we report a high-density ternary storage platform by developing bidirectional patterning of silk fibroin-derived films using thermal scanning probe lithography (t-SPL). Unlike conventional subtractive t-SPL, the distinctive thermochemical response of silk fibroin enables bidirectional direct writing of both concave and convex nanostructures, forming a discrete three-state encoding medium with an areal storage density of up to 600 bit/μm². Reliable data storage and readout across diverse formats, including digital images, audio files and intrinsically ternary data sets, have been demonstrated on this bidirectional material platform. In addition to data storage, bidirectional patterns enable dual-channel encryption and phase-transition-based anticounterfeiting. Finally, the structural stability of our bidirectional platform has been evaluated under harsh environmental conditions, demonstrating long-term reliability for practical applications. Overall, this work establishes a versatile, robust, and biocompatible ternary storage platform with strong potential for efficient and large-scale ternary data applications.