This Idea Is Golden
Using a mesh of gold threads, an ultra-thin, non-irritating wearable sensor has been developed that can measure chemicals in biofluids.
Recent years have seen an explosion in the availability of wearable sensor technologies. Whether the sensor is directly adhered to the skin, or incorporated into another wearable device like a smartwatch, these sensors can collect all manner of information about the wearer’s health and their surroundings. Earlier devices focused mainly on vital signs, like blood pressure and heart rate, or the wearer’s motions in the form of a step counter. More recent wearable sensors that can perform a chemical analysis of the wearer’s biofluids (e.g. sweat, saliva) have started to appear, which offers many opportunities for gaining a better understanding of complex physiological and pathological conditions.
As it turns out, however, these newer sensors are only capable of detecting one specific type of chemical at a time. This prevents wearables from analyzing the important interplay between chemicals that can reveal much richer insights. This situation may change soon as a result of some recent research conducted by a team at the University of Tokyo. They have created an ultra-thin sensor that attaches directly to the skin and is capable of measuring multiple biomarkers or other substances simultaneously.
The new sensors are spun from very fine threads of gold arranged in a mesh. Using gold brings multiple benefits to the table — it is unreactive, which means it will not change the measured chemicals in any way, and also gold is non-irritating, so it will not cause any discomfort when applied to the skin, even for long durations. The pattern of each sensor mesh is specifically designed to tune it to the chemicals it is intended to detect. The detection process uses a technique called Raman spectroscopy, which is extremely sensitive.
In order to capture a reading from the sensor, a low-power laser light is shined at the sensor. Some of this laser light will reflect off of the sensor’s surface. Some wavelengths of that reflected light will remain unchanged, while others will be reflected at a lower power level. Because of the specific tuning of the sensor, it is known that any reflected light that has lost power is due to interactions with the chemical it is designed to detect. This energy fingerprint of the light can be detected and decoded with the help of a spectrometer.
If you followed that explanation closely, you will have surely recognized that there is one massive elephant in the room. Sure, the sensor is comfortable, non-irritating, and extremely lightweight, so it would be no problem to wear such a device around the clock to continuously monitor body chemistry — but wait a minute, what about that laser and spectrometer? Without them, the wearable is nothing more than a mesh of gold. But with them, the device is neither mobile nor unobtrusive. The researchers are well aware of this limitation and have hypothesized that they may be able to integrate a semiconductor nanolaser and a nanospectrometer into the patch to build a truly independent device in the future, but at this point it is still speculation.
In the future, the team plans to explore glucose monitoring for those suffering from diabetes. They believe that it may even be possible for the technique to detect viruses. These are some excellent ideas, and the technology may prove to be very valuable one day. But it remains to be seen if the technology can be made portable and practical for real-world use.