A Flexible Nylon-Spandex Fabric-Supported PVA/PANI Hydrogel Sensor with High Strength and Conductivity

The excellent conductivity of flexible hydrogel sensors endows them with a wide application range. However, traditional flexible hydrogel sensors lack mechanical strength, which greatly limits their usage. In this study, fabrics were used to improve mechanical properties. Particularly knitted ones, characterized by good mechanical stability, breathability and a soft texture. This combination can fit well on the skin and provide an ideal platform for flexible sensing. We utilize brocade nylon-spandex knitted fabrics to reinforce poly(vinyl alcohol) (PVA) hydrogels. The results show that the elongation at break of the conductive hydrogels increases by 1.57 times compared to the original, while their tensile stress is enhanced 7.2-fold. The hydrogels can lift a bucket with 19 L of water with no obvious damage. We employ polyaniline (PANI) and calcium chloride (CaCl2) as conductive materials, which give the hydrogels high conductivity. Ethylene glycol and water serve as solvents for preparing the PVA/PANI conductive hydrogels. Due to the presence of ethylene glycol, the hydrogels are resistant to frost and can maintain their conductivity even at −18 °C. These are subsequently coated on nylon-spandex fabrics. The direct coating can be mass produced using a simple and cost-effective method. The PVA/PANI hydrogel fabric sensor demonstrates high sensitivity, excellent linearity, fast response and recovery times, remarkable durability and the ability to detect various levels of human motion. These findings indicate significant potential for flexible sensor applications.