A Transparent and Robust Ionogel with Stress‐Induced Microphase Separation Property and Crack Insensitivity for Visual Force Sensor

Gel with ionic conductivity and stretchability is considered as an ideal alternative to conventional rigid metallic conductors in the flexible electronics. However, present gels suffer from poor mechanical properties and crack sensitivity due to their weak intermolecular (chain) interactions and homogeneous network structure. Herein, a transparent and tough polyacrylamide (PAM) ionogel is designed, which can form stress-induced microphase-separated domains with high hydrogen bonding density under stress to inhibit crack propagation. Benefiting from multiple hydrogen bonding interactions, the PAM ionogel exhibited maximum tensile stress of 5.19 ± 0.52 MPa, maximum tensile strain of 685.49 ± 22.15%, and fracture toughness of 10.11 ± 1.63 kJ m^-2. On the other hand, the visual force sensor is realized by utilizing the stress-induced changes in the grayscale and electrical resistance of the PAM ionogel, which allowed real-time and visual monitoring of the stress applied to an object as a whole or in part. This work may open new avenues for the development of stable and reliable flexible sensors.