Fabrication methods and applications of printed wearable sensors for real-time sweat analysis: a comprehensive review

Sweat analysis has emerged as a new approach for non-invasive and continuous health monitoring. One of the significant advances in non-invasive sweat analysis has been leveraged by the implementation of printing technologies in electrochemical (bio)sensors. This in-depth review analyzes the fast-changing landscape of these cutting-edge sensors, emphasizing their strong potential to deliver continuous, real-time health information conveniently and affordably. We thoroughly examined various printing methods, including screen printing, inkjet printing, 3D printing, laser printing, roll-to-roll printing, and electrohydrodynamic jet printing, for the fabrication of the sweat sensors. In addition, an extensive section examines electrode and substrate materials, ranging from conventional carbon-based and metallic materials to advanced nanomaterials and conductive polymers. We also evaluated the shift from traditional carbon and metallic electrodes to advanced nanomaterials. A detailed assessment is provided of recent progress in the detection of critical analytes such as glucose, lactate, electrolytes, cortisol, and other ions across fitness and sports tracking, disease management, workplace health and safety, and personalized medicine. The last portion of the paper is devoted to unraveling the challenges against practical and commercial adaptation: long-term stability, sensitivity, and selectivity in complex bio-environments, and integration with communication technologies.