Next-Generation Wearable Optical Sensors for Personalized Health and Point-of-Care Diagnostics-A Systematic Review

Wearable optical sensors (WOS) represent a rapidly evolving class of technologies that integrate photonic detection with flexible, skin-compatible platforms for real-time monitoring of physiological and environmental parameters. This review presents a comprehensive and interdisciplinary analysis of the WOS landscape, spanning from fundamental materials to translational applications. We systematically examine traditional optical materials, advanced nanomaterials, including metallic nanoparticles, quantum dots, 2D materials, and metal-organic frameworks, and functional polymers used in sensor fabrication. The discussion extends to key optical sensing mechanisms such as colorimetry, luminescence, Surface-enhanced Raman spectroscopy (SERS), photoacoustic and multispectral sensing, and optical fiber-based methods. In addition to materials and mechanisms, we explore emerging trends in device integration, including smartphone-based platforms, microfluidics, and machine learning algorithms for signal processing and pattern recognition. Particular attention is given to the application domains of WOS, including non-invasive health diagnostics, fitness monitoring, environmental sensing, and food safety. Drawing on advances in materials science, photonics, bioengineering, and data science, this review offers a structured framework that highlights design principles, performance metrics, and translational challenges, ultimately guiding the development of next-generation wearable photonic technologies.