Bionic Diffractive Meta-Silk Patch for Visually Flexible Wearables

Rapid humidity response contributes tremendously to visually flexible wearables. However, sluggish response, infrequent reproducibility, and biotoxicity restrict the development of wearable humidity response devices. Here, inspired by the changes in the color of Dynastes hercules, a flexible wearable, rapid response, stretchable, rewritable meta-silk fibroin diffractive film (mSFD) is presented. The film is generated by spin-coating silk protein and polyurethane (PU) cross-linking, followed by hot pressing of meta-structures. Owing to the diffraction and stable combination of the SF β-structure and PU hydrogen bond, mSFDs exhibit excellent coloration, rapid response, and erasability. Notably, the microcolumns and microporous structures on the meta-membrane endow the membrane with unparalleled rapid response features. Fast color disappearance and reappearance are observed under high humidity conditions (response time <2 ms, cycle in 1 s). In particular, the rapid humidity responsiveness of mSFP induces a change in the color of the membrane, which enables its application in real-time biomonitoring (wound management, mask regulation) and anticounterfeiting (medicine storage, fingerprint recognition). These properties endow bioinspired mSFD P with high potential in the field of robotic skin.