A nanocomposite hydrogel loaded with Ag nanoparticles reduced by aloe vera polysaccharides as an antimicrobial multifunctional sensor.

Developing high-performance hydrogels with anti-freeze, and antimicrobial properties is crucial for the practical application of flexible sensors. In this study, we prepared silver nanoparticles (AgNPs) with aloe polysaccharide (AP) as a reducing agent. Then, the AP/AgNPs were added to a system of polyvinyl alcohol and borax crosslinked in water/glycerol to obtain a multifunctional conductive hydrogel. The incorporated AgNPs improved the conductivity (0.39 S/m) and mechanical properties (elongation at break: 732.9 %, fracture strength: 1267.6 kPa) of the hydrogel. In addition, resultant hydrogel exhibited potential for sensing strain, temperature, and humidity. When used as a strain sensor, the hydrogel system exhibited low detection limit (0.1 %), and fast response (0.08 s). The resistance of the hydrogel decreased with an increase in the absorbed moisture content, enabling humidity detection (25-95 %) to monitor breathing status. As a temperature sensor, the hydrogel supported a wide detection range (-50 to +90 °C) and sensitivity (-30-0 °C, temperature coefficient of resistance (TCR) = -5.64 %/°C) to detect changes in the ambient temperature. This study proposes a simple method for manufacturing multifunctional hydrogel sensors, which broadens their application prospects in wearable sensing and electronic products.