Mechanically Robust, Antifatigue, and Temperature-Tolerant Nanocomposite Ionogels Enabled by Hydrogen Bonding as Wearable Sensors

Abstract

Flexible wearable sensors originating from ionogels have found extensive and significant applications in electronic skins, body-health monitoring, and personal healthcare diagnosis. Developing an ionogel-based sensor with robust mechanics and durable sensing in a wide service temperature range remains challenging. Herein, a high-performance wearable sensor with temperature-tolerant mechanics and durable sensing was constructed by virtue of hydrogen bonding between a poly(vinyl alcohol) (PVA)-incorporated nanocomposite interpenetrating network and an ionic liquid, i.e., 1-butyl-3-methylimidazolium iodide ([C 4 mim][I]). Through modulation of hydrogen bonding and thus good compatibility between [C 4 mim][I] and the network, the ionogels exhibited superior mechanics, excellent antifatigue, and durable sensing in a wide working temperature range. The ionogel-based wearable sensor exhibited stable and repeatable sensitivity toward various human motions including finger bending, elbow joint bending, and swallowing. More importantly, the pressure sensing can be completely preserved in a service temperature range of −20 to 80 °C. This work provided a feasible method to construct a mechanically strong, temperature-durable ionogel-based multimode sensor, which would find versatile applications as electronic skins, human-motion detection, and intelligent devices.

Highly Stretchable, Self-Repairable, and Super-Adhesive Multifunctional Ionogel for a Flexible Wearable Sensor

“…After mixing AM with [BMIM]Cl, the chemical shifts of hydrogen on π bonds on the imidazole ring in [BMIM]Cl moved toward the high field, indicating that the hydrogen atom on π bonds on the imidazole ring acts as a hydrogen bond acceptor, while the electronegative N atom on the amide group in PAM can be considered as a donor. 37 The presence of a large amount of hydrogen bonding in the ionogel enabled good mechanical and self-healing properties of the ionogels. The interactions were further confirmed by FT-IR, as shown in Figure S3.…”

“…As shown in Figure S2, the chemical shifts of hydrogen in the amide group on acrylamide drifted toward the low field after mixing AM with [BMIM]­Cl, where the peak of hydrogen in the amide group at 7.50 ppm drifted to 7.77 ppm. After mixing AM with [BMIM]­Cl, the chemical shifts of hydrogen on π bonds on the imidazole ring in [BMIM]Cl moved toward the high field, indicating that the hydrogen atom on π bonds on the imidazole ring acts as a hydrogen bond acceptor, while the electronegative N atom on the amide group in PAM can be considered as a donor . The presence of a large amount of hydrogen bonding in the ionogel enabled good mechanical and self-healing properties of the ionogels.…”

Tardigrade-inspired extremotolerant glycerogels

“…For example, double-hydrophobic-coated hydrogels have long-term air stabilities 12 . Ionic liquid-based ionogels exhibit wide temperature tolerance levels 14,15 . However, ionic liquids are generally expensive, and many of them are harmful to the environment 16 , making them less suitable for mass applications.…”

“…However, ionic liquids are generally expensive, and many of them are harmful to the environment 16 , making them less suitable for mass applications. The mechanical properties of ionogels depend strongly on polymer-solvent interactions; therefore, despite the wide temperature stabilities of ionic liquids, the mechanical properties of ionogels vary significantly with changes in temperature due to variations in the polymer-solvent interactions 14,15 . In recent years, biofriendly and inexpensive polyol solvents, such as glycerol, propylene glycol, and ethylene glycol, that exhibit wide-temperature stability have attracted significant attention for the development of extremotolerant gels 11,13,14,[17][18][19][20][21][22][23][24][25][26][27] .…”

Tuning Compressive Young’s Moduli and Antibacterial Activities of Alginate/Poly(N-isopropylacrylamide) Hydrogels with Laponite Layers and Cerium Ions

“…Hydrogels having superior mechanical properties, optical transparency, ionic conductivity, stimulus responsiveness, and biocompatibility are used as soft robots, and actuators, sensors, communicators, and power sources can be prepared using these hydrogel-based soft robots. − Biopolymers such as cellulose, alginate (Alg), and gelatin have also been used to produce biodegradable materials for soft robotics …”