Hydrophobically Associated\nFunctionalized CNT-Reinforced\nDouble-Network Hydrogels as Advanced Flexible Strain Sensors

Abstract

Hydrogels have gained the attention of researchers worldwide\nand\ncan be widely applied for use in medical technologies in human health\nand in industrial applications such as robotics. However, producing\na hydrogel with proper mechanical properties, low hysteresis energy,\nquick shape recovery, and long-range strain sensitivity is still an\nongoing development. More development into hydrogel technology could\nalso lead to an increase in the effectiveness and lifespan of artificial\njoint replacements. Our hydrogels can be incorporated into the development\nof highly sensitive strain sensors for wearable electronic devices.\nTo work toward developing these technologies, multifunctional dual\ncrosslinked hydrogels were developed using lauryl methacrylate, acrylamide,\nand acid-functionalized multiwalled carbon nanotubes (A-MWCNTs). Due\nto the dual crosslinking, the synthesized hydrogels display outstanding\nmechanical performance (high fracture stress, strain, toughness, and\ntensile strength). In shape recovery, the materials recover their\noriginal shape after compression and maintain hydrostaticity. A low\nhysteresis energy of 11.57 kJ m^–3 makes it a suitable\ncandidate for strain sensing with high sensitivity (GF = 9.2 at 500%\nstrain) to monitor different human motions (wrist, neck movements,\nflexion of the fingers, swallowing, and during speaking). Additionally,\ndue to its good mechanical properties, the cyclic stability was monitored\nup to 300 cycles and the hydrogel still was mechanically stable and\nhad the fastest response–recovery time of less than 130 ms\nduring mechanical performance studies. Our hydrogels can be used to\ndevelop highly sensitive strain sensors for wearable electronic devices.