Smartwatches, fitness trackers and other wearables have brought us a new era of health literacy and empowerment with their ability to continuously collect real-time data. However, there’s still room to improve what they can tell us, according to Sherwin Tan, a Research Engineer at the A*STAR Institute of Materials Research and Engineering (A*STAR IMRE).
“Current devices primarily measure biophysical parameters, such as heart rate and oxygen saturation level (SpO2),” said Tan. “Yet there’s also a strong need for them to capture biochemical data, like cholesterol levels, to provide a more holistic picture of one’s health and vital signs.”
Typically, those biomarkers are assessed through bodily fluids like sweat, urine or blood. This can be problematic, particularly for those who are less active or unable to draw frequent blood samples.
A team co-led by Le Yang, Head of the Printed Organic Flexible Electronics and Sensors (PROFESS) Group at A*STAR IMRE, and Yuxin Liu from the Institute for Health Innovation and Technology, National University of Singapore (NUS), pioneered a new generation of continuous wearable sensors capable of detecting solid-state epidermal biomarkers (SEBs). Found on the skin’s epidermal layer, SEBs—which include cholesterol, lactate and proteins—have shown potential to reveal various physiological states or diseases without the invasiveness of traditional methods.
In a recent innovative work, Tan, Yang, Liu and colleagues from A*STAR IMRE, the A*STAR Institute of High-Performance Computing (A*STAR IHPC) and A*STAR Institute of Molecular Cell and Biology (A*STAR IMCB); NUS and Nanyang Technological University, Singapore, proposed that a stretchable ionic–electronic bilayer hydrogel—one that adheres directly to the skin—could enhance SEB detection sensitivity and accuracy, while also reducing motion artifacts that often compromise the performance of current sensors.
Their sensor comprises two distinct layers: an ionic conductive hydrogel (ICH) and an electronically conductive hydrogel (ECH). “The ICH layer is in direct contact with the skin and dissolves SEBs, allowing them to diffuse rapidly toward the ECH layer, where enzymes trigger an electrochemical reaction,” explained Yang. “This process generates an electrical signal that correlates to the targeted biomarker’s concentration.”
In tests, the hydrogel sensor achieved low detection limits for lactate and cholesterol which outperformed certain mass spectrometry techniques. Its design also reduced motion-related errors threefold versus conventional sensors, boosting its reliability during physical activities. During clinical trials, its stability and strong correlation with blood biomarkers highlighted its suitability for long-term health monitoring.
“Whether for watches, armbands or headbands, our sensor is designed to be seamlessly incorporated into daily items, offering a non-invasive, continuous view of important biochemical markers,” said Yang.
With two patent applications underway for their hydrogel sensor technology, the team is also eager to advance their newly launched BLISS (Bettering Lives with In-situ Solid-state Sensorics) programme, which aims to improve SEB sensing, boost the durability of enzyme components and progress the development of flexible electronics.
The A*STAR-affiliated researchers contributing to this research are from the A*STAR Institute of Materials Research and Engineering (A*STAR IMRE), the A*STAR Institute of High-Performance Computing (A*STAR IHPC) and the A*STAR Institute of Molecular Cell and Biology (A*STAR IMCB).
