The ultra-thin sensor helps to measure different biomarkers to perform chemical analysis on the body

The researchers created a special ultra-thin sensor, spun from gold, that can be attached directly to the skin without irritation or discomfort. The sensor can measure different biomarkers or substances to perform chemical analysis on the body.

It works using a technique called Raman spectroscopy, where the laser light directed at the sensor is slightly modified depending on the chemicals present on the skin at the time. The sensor can be fine-tuned to be extremely sensitive and robust enough for practical use.

Wearable technology is nothing new. Maybe you or someone you know wears a smartwatch. Many of them can monitor certain health conditions such as heart rate, but currently cannot measure chemical signatures that could be useful for medical diagnosis.

Smartwatches or more specialized medical monitors are also relatively bulky and often quite expensive. Driven by such shortcomings, a team consisting of researchers from the Department of Chemistry at the University of Tokyo sought a new way to detect various health conditions and environmental problems in a non-invasive and cost-effective way.

A few years ago, I came across a fascinating method for producing rugged expandable electronic components from another research group at the University of Tokyo. These devices are made from ultra-thin wires coated in gold, so they can be attached to the skin without any problem because the gold does not react with the skin and does not irritate it in any way. As sensors, however, they were limited to detecting movement, and we were looking for something that could detect chemical signatures, biomarkers, and drugs. So we took that idea and created a non-invasive sensor that exceeded our expectations and inspired us to explore ways to improve its functionality even further..”

Limei Liu, Visiting Scholar and Lecturer, Yangzhou University

The main component of the sensor is the fine gold mesh, because gold is non-reactive, which means that when it comes into contact with a substance the team wants to measure – for example a potential biomarker for disease present in sweat – it does not chemically modify this substance.

But instead, because the gold mesh is so fine, it can provide a surprisingly large surface area for this biomarker to bind to, and that’s where the other sensor components come in. Like a laser of low power is pointed at the gold mesh, part of the laser light is absorbed and part is reflected. Most of the reflected light has the same energy as the incoming light.

However, some of the incoming light loses energy to the biomarker or another measurable substance, and the energy gap between the reflected light and the incident light is specific to the substance in question. A sensor called a spectrometer can use this unique energy fingerprint to identify the substance. This method of chemical identification is known as Raman spectroscopy.

“Currently, our sensors need to be fine-tuned to detect specific substances, and we want to push the sensitivity and specificity even further in the future,” said Assistant Professor Tinghui Xiao. “With this, we believe applications such as blood sugar monitoring, ideal for people with diabetes, or even virus detection, could be possible.”

“It is also possible that the sensor will work with other chemical analysis methods besides Raman spectroscopy, such as electrochemical analysis, but all of these ideas require much more investigation,” said Professor Keisuke Goda. “In any case, I hope this research can lead to a new generation of low-cost biosensors that can revolutionize health monitoring and reduce the financial burden of healthcare.”