Wearable chemical sensor made from gold measures several biomarkers

Researchers have developed a wearable chemical sensor using gold that attaches to the skin without any discomfort to the wearer and is able to measure a number of different biomarkers or substances to perform on-body chemical analysis.

The sensor works using a technique called Raman spectroscopy, where laser light aimed at the sensor is changed slightly depending on whatever chemicals are present on the skin at that point. The sensor can be finely tuned to be extremely sensitive, and is robust enough for practical use.

Wearable technology is nothing new. Perhaps you or someone you know wears a smartwatch. Many of these can monitor certain health matters such as heart rate, but at present they cannot measure chemical signatures which could be useful for medical diagnosis. Smartwatches or more specialized medical monitors are also relatively bulky and often quite costly. Prompted by such shortfalls, a team comprising researchers from the Department of Chemistry at the University of Tokyo sought a new way to sense various health conditions and environmental matters in a noninvasive and cost-effective manner.

The main component of the sensor is the fine gold mesh, as gold is unreactive, meaning that when it comes into contact with a substance the team wishes to measure — for example a potential disease biomarker present in sweat — it does not chemically alter that substance. But instead, as the gold mesh is so fine, it can provide a surprisingly large surface for that biomarker to bind to, and this is where the other components of the sensor come in. As a low-power laser is pointed at the gold mesh, some of the laser light is absorbed and some is reflected. Of the light reflected, most has the same energy as the incoming light. However, some incoming light loses energy to the biomarker or other measurable substance, and the discrepancy in energy between reflected and incident light is unique 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.

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