Recent research has made progress in developing devices to monitor blood sugar levels without drawing blood, but finding one with accuracy, long-term stability, and multi-function ability is still a challenge. A research team led by Professor Sei Kwang Hahn (MSE, GSCST), Dr. Tae Yeon Kim, and Sunah Cheong (MSE), together with the InHandPlus (CEO: Hwiwon Lee) research team, has recently developed a technology that enables monitoring of blood sugar level in sweat with long-term stability, while also checking oxygen concentration and heart rate. This research has been published in the international biosensor journal, Biosensors and Bioelectronics online.

The research team, unlike in existing technologies, focused on sweat. They developed a Tesla valve-based microfluidic system, which enables the control of sweat flow to a certain direction. Combining this with an optical hydrogel that reacts to blood sugar and an optical module with micro LED and photodetector, the team has successfully developed a smartwatch with a glucose monitoring system.

When the sweat flows through the Tesla valve and reaches the sensor, the sensor produces a fluorescence signal according to the blood sugar level. Then, the signal is converted to an electric signal by an LED and a photosensor, and the user is able to check their glucose level in real-time. This system succeeded in measuring the blood sugar level of 0.01-1mM concentration in sweat with accuracy. It has also proved to maintain its sensitivity in the long term and to have substantial correlation with the actual blood sugar level.

By utilizing lights with different wavelengths, the technology can be used as a multi-functional health care system, which can also measure the oxygen concentration level and heart rate. Prof. Hahn also explained that the system has the potential to be utilized and applied in monitoring other chronic diseases.