Nanomaterial -enabled flexible sensors for continuous biomedical monitoring and closed-loop intervention.

With the increasing demand for biomedical monitoring transitioning from in vitro intermittent assays to continuous, in situ, and intelligent systems, flexible sensing technology has become a direct bridge between detection and intervention. This review systematically summarizes recent advances in nanomaterial-based flexible sensors for biomedical applications. It first introduces commonly used flexible substrates, including polymers, paper, textiles, and hydrogels, highlighting their mechanical compliance, electrical performance, and strategies for functional modification. Secondly, nanomaterials are classified by dimensionality, zero-dimensional, one-dimensional, and two-dimensional, to discuss their unique advantages in enhancing sensor sensitivity, selectivity, and stability. The review further explores the multi-tiered applications of flexible sensors, spanning surface-worn wearable devices, deep-tissue implantable devices, and intelligent closed-loop systems. At the same time, it addresses persistent challenges such as mechanical fatigue, biofouling, signal drift, and power limitations during long-term operation. Looking forward, the development of high-performance flexible sensors relies on the integration of advanced materials, edge artificial intelligence, and wireless technologies to enable high-fidelity, multimodal, and closed-loop diagnostic and therapeutic systems. This comprehensive overview provides a structured reference for the application of flexible nanomaterials in health monitoring, disease management, and clinical translation, underscoring the promising trajectory of flexible sensing toward intelligent, real-time medical intervention.