Such a device could 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. 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."
"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 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 Yin, who is also a Ph.D. student in Wang's lab.
The blood pressure sensor sits near the center of the patch. It consists of a set of small ultrasound transducers that are 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 detecting 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.
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," 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," Lin said.
MEDICA-tradefair.com; Source: University of California San Diego
