Carbon\nNanotubes/Hydrophobically Associated Hydrogels as Ultrastretchable,\nHighly Sensitive, Stable Strain, and Pressure Sensors

Abstract

Conductive hydrogels\nhave become one of the most promising materials for skin-like sensors\nbecause of their excellent biocompatibility and mechanical flexibility.\nHowever, the limited stretchability, low toughness, and fatigue resistance\nlead to a narrow sensing region and insufficient durability of the\nhydrogel-based sensors. In this work, an extremely stretchable, highly\ntough, and anti-fatigue conductive nanocomposite hydrogel is prepared\nby integrating hydrophobic carbon nanotubes (CNTs) into hydrophobically\nassociated polyacrylamide (HAPAAm) hydrogel. In this conductive hydrogel,\namphiphilic sodium dodecyl sulfate was used to ensure uniform dispersion\nof CNTs in the hydrogel network, and hydrophobic interactions between\nthe hydrogel matrix and the CNT surface formed, greatly improving\nthe mechanical properties of the hydrogel. The obtained CNTs/HAPAAm\nhydrogel showed excellent stretchability (ca. 3000%), toughness (3.42\nMJ m^–3), and great anti-fatigue property. Moreover,\nit exhibits both high tensile strain sensitivity in the wide strain\nranges (gauge factor = 4.32, up to 1000%) and high linear sensitivity\n(0.127 kPa^–1) in a large-pressure region within\n0–50 kPa. The CNTs/HAPAAm hydrogel-based sensors can sensitively\nand stably detect full-range human activities (e.g., elbow rotation,\nfinger bending, swallowing motion, and pronouncing) and handwriting,\ndemonstrating the CNTs/HAPAAm hydrogel’s potential as the wearable\nstrain and pressure sensors for flexible devices.