Wood-fiber-based flexible wearable sensors: modification strategies, fabrication methods, and sustainable applications

Flexible sensors have garnered significant attention due to their inherent flexibility, abrasion resistance, and tunable mechanical properties, which enable real-time, non-invasive detection of diverse stimuli. The performance of these sensors largely depends on the properties of their sensing materials. With growing environmental concerns, natural fiber composites—especially wood fiber—have emerged as sustainable alternatives due to their renewability, mechanical strength, biocompatibility, and biodegradability. In contrast, conventional materials like metal films and conductive polymers suffer from fragility, limited conductivity, and complex fabrication, limiting their use in demanding environments. Wood fiber offers advantages such as low cost, biodegradability, and high flexibility, yet its poor electrical conductivity, moisture sensitivity, and limited long-term stability hinder performance. To address these limitations, various chemical, physical, and biological modification strategies have been employed. Concurrently, advanced fabrication techniques have been developed to enhance conductivity, flexibility, and scalability. Unlike previous reviews that focus mainly on flexible sensors or cellulose-based materials, this review emphasizes wood fiber as an integrated structural, functional, and sustainable platform for wearable sensing systems. It highlights recent progress in the modification and processing of wood fiber-based flexible sensing materials, explores their applications in health monitoring, human–machine interfaces, environmental detection, and industrial fields, and discusses future opportunities and ongoing challenges. Recent advances in wood-fiber-based flexible materials for sensor applications are systematically summarized. Chemical, physical, and biological modification strategies for wood-fiber-based flexible sensors are classified and compared. Preparation techniques for wood-fiber-based sensors are summarized, with emphasis on their respective advantages and limitations.