Multiple hydrogen bonds reinforced conductive hydrogels with robust elasticity and ultra-durability as multifunctional ionic skins

Ion-conductive (IC) hydrogels as ionic skins (I-skins) have shown vast potentials in wearable electronic devices, human-machine interfaces, and health monitoring. However, it is still challenging to fabricate IC hydrogels with high stretchability and robust elasticity to stably output electrical signals subjected to multiple mechanical cy-cles. In this work, profiting from the hydrophobicity-assisted multiple hydrogen bonds formation by N-acryloyl phenylalanine (APA), we develop an IC hydrogel sensor with comprehensive performances by one-pot radical polymerization of APA and acrylic acid (AA) in the presence of ferric chloride (FeCl3). The hydrogels show excellent mechanical properties with tensile strength of 210-400 kPa, fracture strain of 880-1100%, and elastic modulus of 71-94 kPa, and could withstand multiple mechanical cycles (1000 tensile cycles with 100% of strain and 1000 compressive cycles with 40% of strain) with robust elasticity. Moreover, the hydrogels feature high conductivity (0.55 S/m), excellent sensing performance (gauge factor (GF) = 7.95), and wide sensing range of strain (2.5-300%) and pressure (1-80 kPa), which can be utilized for the detection of large and tiny movements of human body and the monitoring of sleep quality with reliable signal outputs. Based on the adequate tissue adhesiveness, rapid self-recovery, excellent fatigue resistance and good biocompatibility, the IC hydrogels can serve as promising smart flexible electronics for the application in different fields.

Automated summary

Ion-conductive hydrogels have vast potentials in wearable electronic devices, human-machine interfaces, and health monitoring. In this work, an IC hydrogel sensor with high mechanical properties and excellent sensing performance was developed using N-acryloyl phenylalanine, which can be used for monitoring human body movements and sleep quality.