Development and characterisation of conductive knitted fabrics as humidity sensors for automatic hemostasis detection

Conductive knitted fabrics can function as humidity sensors, detecting the presence of liquids on their surface through changes in electrical resistance. This property can be leveraged for automatic hemostasis systems, where the detection of blood at a wound site triggers real-time intervention. In this study, conductive yarns including Shieldex (Statex: 60- 440 W/m), AgSiS (Lib-40: 5 W/m), and stainless steel (60 W/m) were integrated into knitted fabrics using a Shima Seiki machine. The fabrics were characterised for mechanical strength, abrasion resistance (1,000 and 5,000 cycles), washing durability (1 and 5 cycles), and resistance to acidic and alkaline perspiration. Electrical resistance was measured under exposure to four aqueous media simulating physiological and wound conditions: deionised water (pH 6, 244 mS/cm), acidic perspiration (pH 5.5, 10.73 mS/cm), alkaline perspiration (pH 8, 11.35 mS/cm), and 20% saline solution (pH 5.0, 9.5 mS/cm). Morphological and compositional analyses were conducted using SEM, EDX, and FTIR spectroscopy. The results demonstrated that all fabrics exhibited measurable and repeatable resistance variations, with the strongest response observed for the 20% saline solution and Lib-40 conductive yarn, highlighting their potential as humidity sensors for real-time detection of bleeding events in automatic hemostasis systems.