Secondary-Structure Engineering of Reprocessable Silk Fibroin Ionogels for Wearable Posture Monitoring

Soft strain sensors for continuous posture monitoring require compliant mechanics, stable ionic transport, and a credible strategy for managing material waste. Here, an imidazolium ionic liquid is used to reorganize the secondary structure of silk fibroin and produce a reprocessable ionogel through solution casting. Ionic-liquid incorporation decreases the β-sheet fraction from 44.9% to 23.8% and increases the random-coil fraction from 53.1% to 74.3%, establishing a tunable balance between load-bearing physical junctions and mobile chain segments. The optimized SF40/IL60 ionogel reaches an elongation at break of 330%, a tensile toughness of 22.88 MJ m–3, and an apparent notch fracture energy of 133.8 kJ m–2. As a resistive strain sensor, it provides a gauge factor of 7.62 over 0–50% strain, stable signals over more than 1000 cycles, and subsecond response and recovery. A three-channel wearable configuration resolves cervical, thoracic, and lumbar motion using spatially differentiated resistance responses. The ionogel can be dissolved and recast for ten cycles with limited loss of mechanical performance and undergoes complete mass loss within 7 weeks under the tested soil-burial conditions. These results connect silk secondary-structure regulation with mechanical compliance, sensing performance, and material reprocessing in a single protein-based platform.