Wearable tracks biomarkers: Skin patch monitors blood pressure, heart rate and glucose levels

17 Feb 2021 --- US engineers have developed a skin patch that tracks blood pressure, heart rate and glucose levels, while measuring either the wearer’s lactate, alcohol or caffeine levels. 

The skin patch is worn on the neck and presents the first wearable device that monitors hemodynamic and metabolic biomarkers at the same time.

The researchers envision that the wearable could help predict abnormal physiological changes and allow wearers to regularly monitor their own health. 

Moreover, it could offer a convenient alternative for patients in intensive care units, including infants in the neonatal intensive care units, who need continuous monitoring of blood pressure and other vital signs. 

“The commercialization potential is huge, particularly for patients with diabetes and cardiovascular disease comorbidities,” co-author and nanoengineering professor Sheng Xu tells NutritionInsight.

“It can also have implications for remote monitoring of COVID-19 patients. We are now actively engaging clinicians to validate our technology on patients against gold standards.”

Wearable sensors can generate data without causing discomfort or interrupting daily activities, thus improving the quality of patient care (Credit: Wang lab/UC San Diago).How does it work?
Published in Nature Biomedical Engineering, the University of California San Diego researchers created a thin sheet of stretchy polymers that can conform to the skin. 

The patch 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 blood pressure sensor sits near the center of the patch, consisting of a set of small ultrasound transducers welded to the patch by a conductive ink. 

A voltage applied to the transducers causes them to send ultrasound waves into the body. When the ultrasound waves bounce off an artery, the sensor detects the echoes and translates the signals into a blood pressure reading.

The chemical sensors are two electrodes that are screen printed on the patch from conductive ink. 

The electrode that senses lactate, caffeine and alcohol is printed on the right side of the patch; it works by releasing a drug called pilocarpine into the skin to induce sweat and detect the chemical substances in the sweat. 

The other electrode, which senses glucose, is printed on the left side; it works by passing a mild electrical current through the skin to release interstitial fluid and measuring the glucose in that fluid.

“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,” Xu details.

The researchers use ultrasonic transducers to monitor hemodynamic markers and electrochemical sensors to measure biomarkers levels.When asked about tracking accuracy, he notes it is very high and within the bounds of regulations. 

“One exception is the blood pressure after having caffeine, which may change the vessel tone and induce relatively large discrepancy in the blood pressure measurements.”

Wireless on the horizon
Current monitoring procedures 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,” explains co-corresponding study author Joseph Wang, a professor of nanoengineering at UC San Diego. 

“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 has also begun developing the next generation of the patch to include more sensors that can monitor other biomarkers associated with various diseases.

Currently, the sensor needs to be connected to a power source and a benchtop machine to display its readings, but Xu affirms his research team is making progress to make the patch wireless, which is “critical for power and data transmission.”

By Anni Schleicher