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

Abstract

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.

Adaptive Ionogel Paint from Room‐Temperature Autonomous Polymerization of α‐Thioctic Acid for Stretchable and Healable Electronics

“…In addition, the intrinsic opacity of conductive fillers also limits their transparent applications. To challenge the paradigm, soft ionic conductors with small ions as charge carriers and polymer network as the matrix, mainly sorted into hydrogels, [ 12,13 ] organohydrogels, [ 14 ] and ionogels, [ 15,16 ] may partially circumvent the above compliance and transparency limitations. Nevertheless, challenging issues still persist for ionic conductors as a conducting paint.…”

Dense Hydrogen-Bonding Network Boosts Ionic Conductive Hydrogels with Extremely High Toughness, Rapid Self-Recovery, and Autonomous Adhesion for Human-Motion Detection

“…The real-time response of an ionic sensor is realized through the directional migration of ions in an ionic conductor under deformation, which can realize the integrated functions of high elasticity and skin comparable modulus that are difficult to realize in a traditional electronic conductor. Due to the frequent movement of the human body and its rough and complex surface, ion sensors would inevitably be damaged and fall off during long-term wearing, which puts forward high requirements for tailored adhesive performances of ionic sensors [ 5 , 6 ]. However, traditional adhesives are very difficult to meet the requirements of ionic sensors in long-term wearing or multiple-time adhering.…”

Ionogel-based flexible stress and strain sensors

“…(h) An resistance IFSS with 80 ms responsive time [59]. (i) High stability with 10,000 cycles of duration [60]. (j) Self-healable ionogel [56].…”