KU Develops a Sweat Sensor Patch with a Display

- The novel sensor is expected to be applied by the healthcare industry as a reusable system enabling continuous monitoring.

△ Activation of the blue display of the attached device after an increase in exercise intensity and lactate levels.

The blue color on the display darkens as the intensity moves from Level 1 to Level 4.

Professor Koo Ja-hyun’s group from the School of Biomedical Engineering at KU (President Kim Dong-One) has developed a reusable digital colorimetric system enabling continuous monitoring via a wearable sensor.

The results of this study were published online on March 28 in Science Advances (Impact Factor=13.7), one of the top-tier journals in the field.

*Article title: Electrophoretic digital colorimetry integrated with electrochemical sweat sensor

*DOI: 10.1126/sciadv.adu2142

*URL: https://www.science.org/doi/10.1126/sciadv.adu2142

In the current biological industry, paper-based colorimetry is used as a diagnostic kit. However, since such kits may not be reused, their use has been limited in the bio-healthcare field, which often requires continuous monitoring.

*Paper-based colorimetry: A test method using color changes on paper that is mainly used for urine tests during health checkups.

To overcome the limitation of the existing colorimetric test method, the research group developed a digital colorimetric system that is reusable and capable of continuous monitoring. The research group synthesized titanium oxide (TiO2)-based color particles and placed them in a folded structure, with a copper electrode at the bottom and a transparent indium tin oxide (ITO) electrode at the top. When voltage is applied, the titanium particles align and a color appears. Using this electronic colorimetric principle, various biomarkers and hormones can be measured and then initialized.

*Transparent indium tin oxide (ITO) electrode: A transparent film formed by depositing a thin layer of indium oxide as an electrode on a plastic material.

*Biomarker: An indicator that can detect changes in the body, such as in proteins, DNA, RNA, or metabolites.

The researchers combined this digital colorimetry system with a wireless communication (Bluetooth low energy (BLE)) system, producing a device that can be attached to the skin and remotely monitor health conditions. Unlike existing wireless systems, this new system enables monitoring through color changes when the (e.g., lactate) concentration set by the user is exceeded. Moreover, the quantitative value is transmitted to a mobile phone in real time so that the monitoring can be performed continuously.

* Bluetooth low energy (BLE): A Bluetooth system capable of transmitting and receiving low-power, low-capacity data in the 2.4 GHz frequency band

For this study, the research group demonstrated the monitoring of lactate concentration through sweat. Testing done with seven adult users confirmed that such continuous monitoring could estimate muscle fatigue according to exercise time and intensity.

*Lactate: A biochemical substance produced in muscles as exercise intensity increases that is related to energy metabolism in the body.

The wearable sensor developed in this study can be operated at low power so that various biomarkers can be measured for a long period of time. In addition, the display turns on when the biomarker concentration reaches a certain level, and the user can than check the data through a device such as a mobile phone. Therefore, it has great potential for use as a medical and healthcare device.

This study was supported by the National Research Foundation of Korea (NRF).

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