Wearable microlasers measure biomarkers in sweat

Scientists at Nanyang Technological University, Singapore (NTU Singapore) have developed a Band-Aid (or plaster)-like device that can indicate health or disease through sweat. Human sweat contains biomarkers such as glucose, lactate and urea that indicate various health conditions and can be collected in a non-invasive and painless manner, making it ideal for daily monitoring.

Diabetic patients typically use an invasive finger prick test to self-monitor blood glucose levels. Patients have to prick their fingers to collect a small drop of blood on a strip before inserting it into a portable glucose meter for a reading. An alternative is sensor-based monitoring devices, which are expensive, rigid and require attachment to the patient’s skin over prolonged periods.

By encapsulating a microlaser in liquid crystal droplets and embedding the liquid within a soft hydrogel film, the NTU team created a compact, flexible, light-based sensing device that can provide highly accurate biomarker readings within minutes. Their innovation has been reported in the journal Analytical Chemistry.

“Our innovation represents a non-invasive, quick and effective way for diabetic patients to monitor their health,” said NTU Assistant Professor Chen Yu-Cheng. “By combining a microlaser with a soft hydrogel film, we have demonstrated the feasibility of a wearable laser to provide a more pleasant health monitoring experience for patients.”

The NTU team created their plaster device by embedding microlasers in liquid crystal droplets. The microlasers are customised to pick up three different types of biomarkers: lactate, glucose and urea. A different coloured liquid crystal dot on the plaster distinguishes each biomarker.

When sweat interacts with the plaster, the amount of light emitted by the microlasers fluctuates based on the concentration of biomarkers present. To read the biomarker levels, users shine a light source on the plaster, and the light emitted from the microlaser sensors is analysed and translated using a mobile application. In real-life experiments, the plaster successfully picked up tiny fluctuations of glucose, lactate and urea levels in sweat down to 0.001 mm, which is 100 times better than current similar technology.

The NTU team believes their innovation to be the first reported wearable sensing device that is capable of measuring multiple biomarkers in sweat with ultrahigh sensitivity and dynamic range. The sensitivity enables tracking of a dynamic range (low to high) of biomarker levels, providing comprehensive information on patients’ health.

“This is particularly beneficial for diabetic patients as current similar health monitoring devices focus on tracking only high glucose levels, but not abnormal or low glucose levels, which may indicate other health complications,” said NTU PhD candidate Nie Ningyuan. “In comparison, our device will provide a clearer picture of the user’s health condition, with a variety of readings captured.”

Commenting as an independent expert, Dr Lin Chun-Hsien from National Taiwan University Hospital said he was hopeful that the wearable device can provide a more convenient and effective way to monitor blood glucose, with its ability to measure other biomarkers “an added bonus” that will offer more health data to the benefit of both patients and physicians. For their next steps, the research team plans to fine-tune the microlaser sensors to detect a wider variety of substances, including drugs and other chemicals found in sweat.

Image caption: The microlasers are customised to pick up three different types of biomarkers: lactate, glucose and urea. A different coloured liquid crystal dot on the plaster distinguishes each biomarker. Image credit: NTU Singapore.