Advances in materials for wearable biosensors.

Wearable biosensors have emerged as transformative instruments for continuous, non-invasive health monitoring, providing real-time analysis of biomarkers in biofluids such as sweat, interstitial fluid, and saliva. This chapter offers a comprehensive overview of the pivotal role of biomaterials in the design and functionality of wearable biosensors. It examines the selection criteria for biocompatible materials, emphasizing properties such as flexibility, stretchability, conductivity, and long-term stability. The discussion categorizes advanced materials, including hydrogels, polyurethanes, carbon-based nanomaterials, metallic nanoparticles, and microneedles, and evaluates their applications in biosensing platforms for glucose, pH, and metal ion detection. Through case studies and figure-integrated explanations, the chapter highlights innovations such as smart hydrogel contact lenses, self-powered alcohol biosensors, and closed-loop microneedle patches for autonomous insulin delivery. It further explores key challenges, including biofluid variability, sensor biocompatibility, and the correlation of biofluid biomarkers with blood concentrations. Finally, the chapter underscores future directions involving AI integration, federated learning, and next-generation biomaterials like biodegradable polymers and stretchable composites. By bridging materials science with digital health technologies, wearable biosensors are poised to revolutionize personalized medicine, enabling early diagnosis, disease prevention, and optimized therapeutic interventions.