Carbon Nanotube Aerogel-Based Composite Hydrogel for Strain Sensing

Conductive hydrogels have been extensively studied as flexible sensing materials. However, conventional conductive hydrogels often exhibit low sensitivity due to the limited incorporation of electronic conductive fillers when directly mixed with polymer components before gelatinization. To address this issue, we developed a strategy to establish a carbon nanotube network within a hydrogel by freeze-drying a carbon nanotube dispersion to produce an aerogel and then encapsulating the aerogel with a conventional conductive hydrogel before gelatinization. By using an in situ formed, poly(vinyl alcohol) (PVA) reinforced and Al3+ cross-linked poly(acrylic acid) (PAA) hydrogel as the polymer matrix, the composite hydrogel achieved excellent sensing performance, including high sensitivity (gauge factor = 29.34), a broad working range of 0-1000%, and an ultralow detection limit of 0.1%. Additionally, the composite hydrogel demonstrated excellent mechanical properties, adhesion, self-healing, and bacteriostatic properties. Moreover, the composite hydrogel-based sensor is capable of monitoring human health and various human activities. The hydrogel also exhibits good water retention and adaptability to extreme temperatures by soaking in a 50% glycerol aqueous solution for 4 h. This work provides an approach to fabricating high-performance conductive hydrogels for wearable electronic devices.