First-of-a-kind patch tracks multiple biochemicals and blood pressure
Advances in flexible electronics have opened up some exciting possibilities in health monitoring, with a breed of soft and stretchy patches emerging that can be worn on the skin to track things like glucose or antibiotic levels, or even change color when there is reason to worry. A new example out of the University of California (UC) San Diego takes this technology into new territory, with engineers building what they say is the first wearable capable of monitoring cardiovascular signals and multiple biochemicals in the body at the same time.
The new stamp-sized patch is the result of a collaboration between two different research ventures at UC San Diego, with scientists working on wearables that can monitor chemical, physical and electrophysiological signals in the body, teaming up with engineers working on advanced blood pressure monitors.
The result of this partnership is a thin sheet of stretchy polymers that can conform to the skin. Packed inside is a blood pressure sensor, a chemical sensor that measures lactate, caffeine and alcohol in sweat, and a sensor that tracks glucose levels in the interstitial fluid. The patch is hooked up to an external power source and gives its reading via a counter-top machine.
Located near the center of the patch, the blood pressure sensor works by sending ultrasound waves through the body that bounce off arteries and create echoes, which the sensor detects and converts into a blood pressure reading. The chemical sensor works by releasing drugs into the skin that induce sweat then measuring the chemicals within that fluid, while the glucose sensor emits a mild electrical current to stimulate the release of interstitial fluid for the same purpose.
The different sensors needed to be carefully arranged on the patch to eliminate interference with the signals, while these types of sensors and the biomarkers they track were chosen for good reason, as they can all impact blood pressure.
"Let's say you are monitoring your blood pressure, and you see spikes during the day and think that something is wrong,” says co-first author Juliane Sempionatto. “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.”
To put this thinking to the test, the researchers ran experiments where subjects were made to wear the patch on their neck while carrying out different tasks, such as a session on an exercise bike, consuming high-sugar meals or alcohol, or drinking a coffee. The team monitored the targeted biomarkers throughout this process using commercial monitoring devices, and compared the readings with those taken from its new patch, finding that they closely matched.
"The novelty here is that we take completely different sensors and merge them together on a single small platform as small as a stamp," says 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."
The team sees potential in using the patch to help people manage high blood pressure or diabetes, or even in settings like intensive care units where vital signs need to be constantly monitored. They are already working on a new version of the patch with even more sensors to detect a wider range of biomarkers, and hope to one day develop a completely wireless version.
"This type of wearable would be very helpful for people with underlying medical conditions to monitor their own health on a regular basis," says Lu Yin, a co-first author of the study. "It would also serve as a great tool for remote patient monitoring, especially during the COVID-19 pandemic when people are minimizing in-person visits to the clinic."
The research was published in the journal Nature Biomedical Engineering.