Mechanically Robust, Elastic, and Healable Ionogels for Highly Sensitive Ultra‐Durable Ionic Skins

• Published in: Advanced materials (Weinheim) Vol. 32; no. 32; pp. e2002706 - n/a
• Main Authors: Li, Tianqi, Wang, Yuting, Li, Siheng, Liu, Xiaokong, Sun, Junqi
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.08.2020
• Subjects: Bonding strength; Crystallization; Durability; Fatigue failure; Hydrogen bonds; Impregnation; Ionic liquids; ionic skins; ionogels; Ions; Materials science; Mechanical properties; Modulus of elasticity; Polyethylene glycol; Robustness; self‐healing materials; Sensitivity; Sensors; supramolecular materials; tough materials; Urea; Volatility
• ISSN: 0935-9648; 1521-4095; 1521-4095
• DOI: 10.1002/adma.202002706

The fabrication of highly durable skin‐mimicking sensors remains challenging because of the unavoidable fatigue and physical damage that sensors are subjected to in practical applications. In this study, ultra‐durable ionic skins (I‐skins) with excellent healability and high sensitivity are fabricated by impregnating ionic liquids (ILs) into a mechanically robust poly(urea‐urethane) (PU) network. The PU network is composed of crystallized poly(ε‐caprolactone) and flexible poly(ethylene glycol) that are dynamically cross‐linked with hindered urea bonds and hydrogen bonds. Such a design endows the resultant ionogels with high mechanical strength, good elasticity, Young's modulus similar to that of natural skin, and excellent healability. The ionogel‐based I‐skins exhibit a high sensitivity to a wide range of strains (0.1–300%) and pressures (0.1–20 kPa). Importantly, the I‐skins show a highly reproducible electrical response over 10 000 uninterrupted strain cycles. The sensing performance of the I‐skins stored in open air for 200 days is almost the same as that of the freshly prepared I‐skin. The fractured I‐skins can be easily healed by heating at 65 °C that restores their original ultra‐durable sensing performance. The long‐term durability of the I‐skins is attributed to the combination of non‐volatility of the ILs, excellent healability, and well‐designed mechanical properties. Highly sensitive ultra‐durable ionic skins (I‐skins) are fabricated by impregnating ionic liquids into a mechanically robust poly(urea‐urethane) network. Even after being stored in open air for 200 days, the I‐skins exhibit a highly reproducible electrical response over 10 000 uninterrupted strain cycles. The fractured I‐skins can be easily healed to regain their original sensing performance.