Patch has potential to deliver medical revolution

A new skin patch that can create a system of wearable medical monitoring has been created by scientists in the United States, who believe it could revolutionise the ability to track people’s health.

It also has the capability for medical staff to remotely monitor patients if they are unable to attend hospital or clinics due to having to self-isolate in situation such as COVID-19.

Engineers at the University of California San Diego have developed a soft, stretchy skin patch that can be worn on the neck to continuously track blood pressure and heart rate while measuring the wearer’s levels of glucose as well as lactate, alcohol or caffeine. It is the first wearable device that monitors cardiovascular signals and multiple biochemical levels in the human body at the same time.

“This type of wearable would be very helpful for people with underlying medical conditions to monitor their own health on a regular basis,” said Lu Yin, a nanoengineering Ph.D. student at UC San Diego and co-first author of the study published in Nature Biomedical Engineering. “It would also serve as a great tool for remote patient monitoring, especially during the COVID-19 pandemic when people are minimising in-person visits to the clinic.”

The device has the potential to benefit individuals managing high blood pressure and diabetes—individuals who are also at high risk of becoming seriously ill with COVID-19. It could also be used to detect the onset of sepsis, which is characterized by a sudden drop in blood pressure accompanied by a rapid rise in lactate level.

“One soft skin patch that can do it all would also offer a convenient alternative for patients in intensive care units, including infants in the NICU, who need continuous monitoring of blood pressure and other vital signs,” said the researchers. “These procedures currently involve inserting catheters deep inside patients’ arteries and tethering patients to multiple hospital monitors.”

“The novelty here is that we take completely different sensors and merge them together on a single small platform as small as a stamp,” said Joseph Wang, a professor of nanoengineering at UC San Diego and co-corresponding author of the study. “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.”

Prof Wang’s lab has been developing wearables capable of monitoring multiple signals simultaneously—chemical, physical and electrophysiological—in the body. And in the lab of UC San Diego nanoengineering Professor Sheng Xu, researchers have been developing soft, stretchy electronic skin patches that can monitor blood pressure deep inside the body. By joining forces, the researchers created the first flexible, stretchable wearable device that combines chemical sensing (glucose, lactate, alcohol and caffeine) with blood pressure monitoring.

“Each sensor provides a separate picture of a physical or chemical change. Integrating them all in one wearable patch allows us to stitch those different pictures together to get a more comprehensive overview of what’s going on in our bodies,” said Prof Xu, who is also a co-corresponding author of the study.

The patch is a thin sheet of stretchy polymers that can conform to the skin. It is equipped with a blood pressure sensor and two chemical sensors—one that measures levels of lactate (a biomarker of physical exertion), caffeine and alcohol in sweat, and another that measures glucose levels in interstitial fluid.

The patch is capable of measuring three parameters at once, one from each sensor: blood pressure, glucose, and either lactate, alcohol or caffeine. “Theoretically, we can detect all of them at the same time, but that would require a different sensor design,” said Mr Yin, who is also a Ph.D. student in Wang’s lab.

“Let’s say you are monitoring your blood pressure, and you see spikes during the day and think that something is wrong. But a biomarker reading could tell you if those spikes were due to an intake of alcohol or caffeine. This combination of sensors can give you that type of information,” said co-first author Juliane Sempionatto, a nanoengineering Ph.D. student in Wang’s lab.

In tests, subjects wore the patch on the neck while performing various combinations of the following tasks: exercising on a stationary bicycle; eating a high-sugar meal; drinking an alcoholic beverage; and drinking a caffeinated beverage. Measurements from the patch closely matched those collected by commercial monitoring devices such as a blood pressure cuff, blood lactate meter, glucometer and breathalyser. Measurements of the wearers’ caffeine levels were verified with measurements of sweat samples in the lab spiked with caffeine.

One of the biggest challenges in making the patch was eliminating interference between the sensors’ signals. To do this, the researchers had to figure out the optimal spacing between the blood pressure sensor and the chemical sensors. They found that one centimetre of spacing did the trick while keeping the device as small as possible.

“Finding the right materials, optimizing the overall layout, integrating the different electronics together in a seamless fashion—these challenges took a lot of time to overcome,” said co-first author Muyang Lin, a nanoengineering Ph.D. student in Xu’s lab. “We are fortunate to have this great collaboration between our lab and Professor Wang’s lab. It has been so fun working together with them on this project.”

The team is already at work on a new version of the patch, one with even more sensors. “There are opportunities to monitor other biomarkers associated with various diseases. We are looking to add more clinical value to this device,” Ms Sempionatto said.

Ongoing work also includes shrinking the electronics for the blood pressure sensor. Right now, the sensor needs to be connected to a power source and a benchtop machine to display its readings. The ultimate goal is to put these all on the patch and make everything wireless.

“We want to make a complete system that is fully wearable,” Mr Lin said.

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