Professor Kyeong-Ha Kwon of KAIST EE and Ph. D student Jong-Wook Kim (Advised by Tae-Il Kim) of School of Chemical Engineering (Sungkyunkwan University) have developed a wireless electronic patch that measures the volumetric flow rate and total loss of sweat in real-time.
Sweat is a biological fluid that can be collected non-invasively and offers the obvious advantage of being easier to collect compared to invasive blood collection. Accordingly, there is an increasing demand for wearable technology that can provide real-time sweat collection and component analysis in daily life.
It is possible to collect various biomarkers using the discoloration reaction of sweat and chemical reagents. Still, it is essential to measure the flow rate and total loss of sweat in real-time for accurate measurement (color development). Accordingly, the research team developed a wearable wireless electronic patch capable of quantitatively measuring the speed and volume of sweat and integrated it with a microfluidic system capable of analyzing sweat components using a discoloration reaction. As a result, the research team succeeded for the first time in simultaneously measuring chloride, glucose, and creatine concentrations, hydrogen ion index (pH), and volumetric flow rate in sweat. The measured index can be used to diagnose cystic fibrosis, diabetes, kidney dysfunction, and metabolic alkalosis.
The research team placed a low-power heat source on the outer wall of a short, sophisticated microfluidic channel where sweat was collected to induce sweat and heat exchange through the channel. Focusing on the increase in the temperature difference between the downstream and the upstream of the heat source as the sweat flow rate increases, the precise relationship between the difference between the upstream and downstream temperatures and the sweat discharge rate was investigated. As a result, it succeeded in accurately measuring the perspiration rate in the range of 0 to 5 microliters/minute (μl/min), which is considered to be physiologically meaningful. Data measured with the wearable patch can be checked in real-time through a smartphone app capable of Bluetooth communication.
The developed patch can be used extensively for individual post-exercise hydration, detection of dehydration symptoms, and other health care. In addition, it is used in places where flow rate measurement is important in the body, such as measuring the blood flow rate in blood vessels located near the skin. It is also expected to develop into various applications, such as a systematic drug delivery system that can check the release rate of drugs in real-time and calculate the correct dosage.
This research, in which Professor Kyeong-Ha Kwon participated as the first author, was published in the international journal 'Nature Electronics' on March 29th. (Paper name: An on-skin platform for wireless monitoring of flow rate, cumulative loss, and temperature of sweat in real-time).
Professor Kyeong-Ha Kwon, Department of Electrical and Electronic Engineering, KAIST
Researcher Jong-Wook Kim, Department of Chemical Engineering, Sungkyunkwan University