HEALTH TECH INNOVATION
This stamp-sized skin patch acts as an all-in-one wearable health monitor
The thin sheet of a stretchy polymer can monitor chemical, physical and electrophysiological signals in the body
Faisal Khan

Faisal Khan

8 hours ago·4 min read

When it comes to a breakthrough in Healthtech, wearable sensors are the next big thing. And I have talked about some of the recent innovations in the field. A similar device was developed by researchers at Penn State University that could be safely printed onto the skin. Before that, I wrote about a separate team of researchers that made a breakthrough in the field with the development of multifunctional sensors and circuits on the skin by utilizing a new form of electronics dubbed as “drawn-on-skin electronics” (DoS).

Taking these innovations one step further, scientists at the University of California San Diego have developed a soft, stretchy skin patch that can be worn on the neck to monitor chemical, physical and electrophysiological signals in the body. The team collaborated with the engineers working on advanced blood pressure monitors. The team believes it is a great invention in monitoring the vital signs of patients in ICUs at hospitals — also useful for people with pre-existing conditions who need constant monitoring.

The wearable sensor is designed such that the blood pressure sensor sits near the center of the patch, which consists of a set of small ultrasound transducers that are welded to the patch by a conductive ink. When a voltage is applied to these transducers, it sends ultrasound waves through the body that bounce off arteries and create echoes, detected by sensors and converting them into a blood pressure reading.

“The novelty here is that we take completely different sensors and merge them together on a single small platform as small as a stamp. We can collect so much information with this one wearable and do so in a non-invasive way, without causing discomfort or interruptions to daily activity.”

~ Joseph Wang, Co-corresponding Author of the Study

Similarly, the chemical sensors are designed by screen printing two electrodes on the patch from conductive ink. The electrode on the right senses lactate, caffeine, and alcohol, while the one on the left measures glucose. The one on the right works by releasing a sweat-inducing drug called pilocarpine into the skin and then detecting the chemical composition of substances in it. The left electrode works by passing a mild electrical current through the skin to release interstitial fluid and measuring the glucose in that fluid.

For the trials, people were made to wear the patch on the neck while performing various tasks — including exercising on a stationary bicycle, eating a high-sugar meal, drinking an alcoholic beverage, and drinking a caffeinated beverage. The results from the patch closely matched the readings collected by generic monitoring devices such as a blood pressure cuff, blood lactate meter, glucometer & breathalyzer.
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Image Credit: UC San Diego

The biggest challenge for the team came in the form of eliminating interference between the blood pressure & chemical sensors. They had to find the optimal spacing to keep their signals from interfering with each other, which turned out to be one centimeter. This also served the purpose of keeping the device as small as possible.

Physically shielding the two sensors from each other was another conundrum that they had to solve. Both sensors came equipped with their own hydrogels to produce clear readings, but these liquid gels needed to be kept separate so that both the liquid gels don’t mix in case of leakage and produce interference between the sensors. To avoid this situation, researchers used solid hydrogel for the blood pressure sensor — works as well as the liquid counterpart without the leakage.

Researchers will continue to improve their prototype by introducing a newer version of the patch with even more sensors to detect a wider range of biomarkers. Currently, the wearable patch needs a power source and to be connected to an external machine to display the results. Eventually, they intend to make a device that is completely wireless.

Complete Research was published in the Journal of Nature Biomedical Engineering.