Engineers at the University of California San Diego have developed a soft, stretchy piece of skin that can be worn around the neck to continuously monitor blood pressure and heart rate while measuring the wearer’s glucose levels. as well as lactate, alcohol or caffeine. It is the first digestive device that monitors cardiovascular and multi-level biochemical signals in the human body simultaneously.
“This type of smoking would be very helpful for people with underlying health conditions to monitor their own health on a regular basis,” said Lu Yin, Ph.D., nanoengineering. student at UC San Diego and co – author of the study published Feb. 15 in Nature Biomedical Engineering. “It would also be a good tool for the study of isolated patients, especially during COVID-19 pandemic disease when people reduce personal visits to the clinic.”
A device like this could be beneficial for people who manage high blood pressure and diabetes-; individuals who are also at risk of becoming seriously ill with COVID-19. It can also be used to detect sepsis, which is characterized by a sudden drop in blood pressure accompanied by a rapid rise in lactate level.
One soft skin pack that can be made whole would also offer a convenient alternative for patients in intensive care units, including babies in the NICU, who need constant monitoring of blood pressure and vital signs. other. These methods currently involve inserting catheters deep inside a patient’s arteries and connecting patients to several hospital examiners.
The new thing here is that we take completely different sensors and combine them on one small platform as small as a stamp. We can collect as much information with this wearable one and do so in a non-aggressive manner, without causing discomfort or disruption to daily activities. “
Joseph Wang, Professor of Nanoengineering, UC San Diego and Corresponding Author of the Study
The new patch is the result of two innovative efforts at the UC San Diego Center for Wearable Sensors, for which Wang serves as director. Wang’s lab has been developing wearables that are capable of monitoring multiple signals simultaneously-; chemical, physical and electrophysiolog-; in the body. And in the laboratory of UC San Diego Sheng Xu nanoengineering professor, researchers have been developing soft, stretchy electronic skin pieces that can monitor blood pressure deep inside the body. Taken together, the researchers created the first affordable flexible device that combines chemical sensitivity (glucose, lactate, alcohol and caffeine) with blood pressure monitoring.
“Each sensor provides a unique picture of physical or chemical change. Integrating them all in one wearable patch allows us to strip these different images together to get a more complete view of what’s going on in our bodies, “said Xu, who is also a corresponding author of the study.
Patch of all trades
The patch is a thin layer of stretched polymers that can adhere to the skin. It is equipped with a blood pressure sensor and two chemical-sensors; one that measures levels of lactate (biomarker of exercise), caffeine and alcohol in sweat, and another that measures glucose levels in interstitial fluid.
The child is able to measure three parameters simultaneously, one from each sensor: blood pressure, glucose, and either lactate, alcohol or caffeine. “Theoretically, we can detect all of them at once, but that would require a different sensor design,” said Yin, who is also a Ph.D. student in Wang’s laboratory.
The blood pressure sensor sits near the center of the baby. It consists of a set of small ultrasound transducers that are welded to the patch with directional ink. Voltage applied to the transducers causes ultrasound waves to enter 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 printed on the array from directional ink are two electrodes. The lactate, caffeine and alcohol sensitive sensors are printed on the right side of the baby; it works by releasing a drug called pilocarpine into the skin to stimulate sweating and detect the chemical substances in sleep. The other electricity, which senses glucose, is printed on the left; it works by passing a gentle electric current through the skin to release interstitial fluid and measure the glucose in that stream.
The researchers were interested in measuring these specific biomarkers because they affect blood pressure. “We chose parameters that would allow us to measure blood pressure more accurately, more reliably,” said co-author Juliane Sempionatto, Ph.D. nanoengineering. student in Wang’s laboratory.
“We say you monitor your blood pressure, and you see spikes during the day and think something is wrong. But a biomarker reading could tell you if those spikes were the result of alcohol or caffeine. This combination of sensitizers can give you that kind of information, “she said.
In experiments, subjects would wear the baby around the neck while performing a combination of the following activities: exercising on a stationary bike; eating foods high in sugar; drinking alcohol; and drinking a caffeinated beverage. Measurements from the patch closely matched those collected by commercial monitoring devices such as a blood pressure bucket, blood lactate meter, glucometer and breathalyzer. Measurements of the caffeine levels of the consumers were determined by the measurement of caffeine-induced sweat samples in the laboratory.
Engineering challenges
One of the biggest challenges in making the patch was to eliminate transitions between the sensory signals. To do this, the researchers needed to find the optimal distance between the blood pressure sensor and the chemical sensors. They found that one centimeter of space did the trick while keeping the machine as small as possible.
The researchers also had to find out how to physically protect the chemical sensors from the blood pressure device. The latter usually come with a melting ultrasound gel to make clear readings. But the chemical sensors are also equipped with their own filters, and the problem is, if any liquid gel from the blood pressure sensor leaks out and communicates with the other gels , that it blocks it between the sensors. So instead, the researchers used a hard ultrasound gel, which they found worked in addition to the melt form but without the leak.
“Finding the right materials, making the most of the overall format, weaving the various electronics together in an unobtrusive way; these challenges took a long time to overcome,” the co-author of Muyang Lin, nanoengineering Ph.D. student in Xu laboratory. “We are fortunate to have this great collaboration between our laboratory and Professor Wang’s laboratory. It has been so much fun working with them on this project. “
The next steps
The team is already working 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 tool,” Sempionatto said.
Continuous work also involves deactivating the electronics for the blood pressure sensor. Currently, the sensor needs to be connected to a power source and a benchtop device to display its readings. The ultimate goal is to put all of these on the patch and do everything wirelessly.
“We want to make a complete system that is full of consumption,” Lin said.
Source:
University of California San Diego
Magazine Reference:
Sempionatto, JR, et al. (2021) Epidermal package for simultaneous study of hemodynamic and metabolic biomarkers. Nature Biomedical Engineering. doi.org/10.1038/s41551-021-00685-1.