Janus Hydrogel with Both Sticky Adhesion and Slippery Antifouling Properties for Strain Sensing

Conductive hydrogels with self-adhesive property have received increasing attention in the fields of human–computer interaction, smart wearable devices, and soft electronic materials; however, they are easily contaminated by oil due to their sticky property, which will degrade their appearance and performance in daily use and make it difficult to be used in the complex oily water environment. Herein, a type of Janus TA@PVA/PSBMA hydrogel with slippery oil repellency and sticky adhesion is prepared by partially compounding the PVA/PSBMA hydrogel with tannic acid (TA) molecules through a unilateral soaking method. The upper PVA/PSBMA hydrogel layer in the Janus hydrogel exhibits excellent antioil fouling capability in air, underwater, and even under oil environments, because of the strong water affinity of the zwitterionic PSBMA chains. Interestingly, the bottom TA@PVA/PSBMA hydrogel layer can adhere to various substrates with bonding strength through active interactions between the TA molecules and the substrates. Exploiting its conductive, antifouling, and self-adhesive properties, the obtained Janus TA@PVA/PSBMA hydrogel is demonstrated as a strain sensor that can stably monitor large and subtle body movements in air, underwater, and oily wastewater. This work is expected to present a material for reliable sensing in complex environments.