Superior, Environmentally Tolerant, Flexible, and Adhesive Poly(ionic liquid) Gel as a Multifaceted Underwater Sensor

In recent years, gel-based sensors have been widely considered and fully developed. However, it is of vital importance, yet rather challenging to achieve a multifaceted gel, which can unify the advantages of favorable conductivity, high adhesion, excellent environmental resistance, and so forth and be applied in various harsh conditions. Herein, an ideal, extremely stable, adhesive, conductive poly(ionic liquid) gel (PILG) was designed via a one-step photoinitiated radical polymerization based on 1-vinyl-3-butylimidazolium bis(trifluoromethylsulfonyl)imide (VBIm-NTf2) cross-linked with ethylene glycol dimethacrylate (EGDMA) in methyltributylammonium bis(trifluoromethanesulfonyl)imide (N1444-NTf2) medium. There are abundant hydrophobic butyl chains and fluorinated groups in VBIm-NTf2 and N1444-NTf2, which can impart the PILG with stable conductivity, excellent environmental tolerance, and adhesion even in water due to the ion–dipole and ion–ion interactions. The resulting PILG can be assembled as a soft and smart sensor that can be applied in specific conditions such as underwater or undersea and even in dynamic water, achieving a stable signal transmission. Meanwhile, the PILG can be utilized as a flexible electrode to convey ECG signals in air or water whether it is in the static or dynamic state. Therefore, it is envisioned that this novel PILG will serve as a hopeful electrical device for signal detection and healthy management in specific environments.