Wearable sensors for health monitoring: Current applications, trends, and future directions

Wearable sensors are redefining health, wellness, and performance monitoring by enabling continuous, non-invasive measurement of biochemical and biophysical signals directly on the body. In this review, we focus on two major classes of wearable technologies: wearable biochemical biosensors, including sweat, tear, saliva, and epidermal-based biochemical sensing, and wearable physical sensors, which monitor pressure, strain, temperature, motion, and other non-biological signals. We summarize recent advances in materials, microfluidics, and electronics that are enabling more practical and versatile wearable sensing platforms. Particular attention is given to multimodal systems that combine chemical and physical measurements on a single device, on-body fluid handling and sampling strategies, and data processing with embedded algorithms. Commercial examples such as continuous glucose monitors, smart patches, and consumer wearables are also highlighted. Key challenges include getting enough biofluid in a reliable way, reducing signal drift and biofouling, dealing with user-to-user variability, keeping data secure, making sensors comfortable to wear, and setting clear on-body or clinical validation protocols. We also highlight recent efforts that aim to address these issues through better surface coatings, more stable sensor designs, new power and energy-harvesting options, and improvements in data management and manufacturing. This review mainly covers studies published between 2018 and 2025, with a particular focus on work from the last 4–5 years.