Sustainable Hydrogels from Okra Stem Waste for Biosignal Detection and Sensor Technologies

Abstract

Recent advancements in wearable technology have driven the need for flexible and biocompatible materials that can seamlessly interface with soft, water-rich biological tissues. Traditional petroleum-based polymers often lack compatibility with conductive materials, limiting their use in bioelectronics. In contrast, hydrogels, with their softness, flexibility, and mechanical similarity to biological tissues, offer a promising alternative due to their ecological benefits and adaptability. Here, we present the development of sustainable hydrogels derived from okra stem mucilage, a renewable agricultural waste, to address challenges in bioelectronics. By integrating gelatin for improved adhesion and succinic acid as a crosslinking agent, we achieved significant enhancements in the hydrogels’ mechanical, electrical, and antibacterial properties. The inclusion of 10% succinic acid increased tensile strength by 95% and Young’s modulus by 93%, while electrical conductivity rose from 0.6 S/m to 1.8 S/m. The hydrogels demonstrated robust adhesion to diverse substrates, including glass, pigskin, and paper, with the highest adhesion strength of 57.3 kPa recorded on paper. Capacitive sensors fabricated using these hydrogels exhibited a maximum relative capacitance change of 1.42 under mechanical strain, and their application as ECG electrodes provided signals comparable to commercial alternatives. These findings establish okra-gum-based hydrogels as a promising platform for sustainable, high-performance materials in wearable bioelectronics, including smart health monitoring and human-computer interaction systems.