Wearable Devices for Biofluid Monitoring in a Body: from Lab to Commercialization

Wearable devices offer diverse continuous monitoring capabilities through advanced sensing methods and wearable devices. Recent advancements in flexible electronics, materials science, and chemistry or electrochemistry have led to the development of wearable sensors for non-invasively monitoring biofluidic markers, including sweat, interstitial fluid (ISF), and tears. These devices utilized integration of various devices such as microfluidic patches, microneedle (MN) arrays, and conformal eye-contact configurations, enabling continuous monitoring of analytes indicative of health status. The progression of wearable devices has evolved towards the use of biocompatible, soft materials that can be worn comfortably on the body for extended periods. This review provides a comprehensive overview of the fundamental essential processes and recent advancements in biomonitoring technologies under the emerging wearable devices and sensing methods that have facilitated the commercialization of wearable devices for healthcare. It covers the physiology of sweat, ISF, and tears, as well as the materials and biosensing mechanisms involved. Advances in sweat induction and sampling methods are also discussed, alongside the design considerations for system-level development of wearable sensing devices.