Abstract
Smart wearable biosensors are gaining attention because of their advancements and ability to detect health biomarkers by analysing physiological fluids, specifically sweat, saliva, tears, interstitial fluid, urine, wound exudate and respiratory breath, using a non‐invasive and microneedle‐based approach. This review critically examines recent advances in smart wearable biosensors using a physiological‐fluids‐based approach, focusing on functional materials such as carbon‐based, metallic, metal oxide, biorecognition elements, and natural and synthetic polymers, as well as on integration strategies that preserve sensing performance, structural integrity and mechanical compliance. Key biomarkers relevant to health and disease monitoring, including glucose, cortisol, uric acid, lactate, vitamin C, ammonium, pH, electrolytes, dopamine, urea, metal ions and miRNA, are discussed in relation to their target fluids and the detection mechanisms used. In vitro and in vivo validation strategies for biomarker detection and biocompatibility assessment are summarised to highlight translational considerations. Finally, current challenges and future perspectives are outlined, providing design insights to enhance the accuracy, reliability and clinical adoption of next‐generation smart wearable biosensors.