A new PVA-κCA double-network hydrogel comprising conductive polyaniline nanofibers for strain sensing applications

Wearable and flexible materials are replacing the conventional solid-state sensors in diffident biomedical applications. Hydrogel-based sensing elements offer several appealing inherent properties such as tissue resembling elasticity, accessibility for modification and robust mechanical performance. Their widely available and affordable raw components in-addition to straightforward synthesis and modification approach make hydrogels appealing material for flexible and wearable sensors in biomedical applications. This work demonstrates the development of new and sensitive material for strain sensing using polyvinyl alcohol (PVA) and kappa-carrageenan (kappa CA) hydrogel comprising conductive polyaniline nanofibers (PANI NFs). The double-network hydrogel was produced via chemical crosslinking of PVA with Glutaraldehyde (GA) and physical crosslinking of kappa CA with potassium ions in a binary solvent system of deionized water and glycerol. The PANI NFs were then embedded in the hydrogel via the interfacial polymerization (IP) method of polyaniline nanofibers to significantly enhance the material properties and strain sensitivity of the pristine hydrogel. The obtained hydrogel has been involved in rigorous material characterization and sensing capability evaluation. The produced hydrogel demonstrated a high-water content (86.6%), high swelling percentage in acidic solutions, mechanical compressibility up to 60% at 400 kPa, high electrical conductivity of 2.11 S/m, and thermal stability ranging from - 26.9 to 120 degrees C. The hydrogel resulted in a linear response in its sensing performance of the applied stress (R-2 = 0.99). Also, the developed composite demonstrated a sensitivity of 1.5 mV/kPa in stress range from zero up to 170 kPa with response and recovery times of similar to 300 ms and 500 ms, respectively.