Wearable Sensor Could Monitor Dehydration and Fatigue

The prototype device, developed by researchers at the University of California Berkeley (USA), consists of a flexible circuit board containing 10 circuit chips connected to five sensors that measure sweat metabolites (glucose and lactate) and electrolytes (sodium and potassium ions), as well as the skin temperature. On contact with sweat, electrical signals from the sensors are read by the circuit chips and adjusted for skin temperature changes. The signals are subsequently transmitted wirelessly to a smartphone app which syncs the data.

The wearable system can be used to measure the detailed sweat profile of human subjects engaged in prolonged indoor and outdoor physical activities, allowing real-time assessment of their physiological state. Each of the four biochemicals measured can offer an insight on the user's health and well-being. Lactate, for example provides information on muscle fatigue; potassium can provide information on dehydration; sodium indicated blood fluid volumes, and glucose levels help determine fatigue. The study describing the technology was published on January 28, 2016, in Nature.

“Human sweat contains physiologically rich information, thus making it an attractive body fluid for noninvasive wearable sensors. However, sweat is complex and it is necessary to measure multiple targets to extract meaningful information about your state of health,” said senior author professor of electrical engineering and computer science Ali Javey, PhD. “In this regard, we have developed a fully integrated system that simultaneously and selectively measures multiple sweat analytes. Our work presents a technology platform for sweat-based health monitors.”

“The idea is to have this thumbs-up or thumbs-down device that will give real-time information; it could provide an alarm that you need to take some medication, or that you’re getting dehydrated and need to drink some water,” concluded Prof. Javey. “When studying the effects of exercise on human physiology, we typically take blood samples. With this noninvasive technology, someday it may be possible to know what's going on physiologically without needle sticks or attaching little, disposable cups on you.”

Perspiration is the production of fluids secreted by sweat glands in the skin of mammals. Two types of sweat glands can be found in humans: eccrine glands and apocrine glands. In humans, perspiration is primarily a means of thermoregulation, which is achieved by the water-rich secretion of the eccrine glands, found over much of the body. Although containing mainly water, sweat also has roughly 800 biomarkers, including minerals such as sodium, potassium, calcium, magnesium, and many other trace elements, such as zinc, copper, iron, chromium, and many more.

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