"E-Tattoo" to measure blood pressure

Measuring blood pressure is a routine part of many people's lives - both in terms of prevention and treatment of various diseases. Researchers in Texas have now developed a method of measuring blood pressure continuously and on the move: With the help of an electrical "tattoo," blood pressure is recorded using the principle of bioimpedance.

Until now, blood pressure has had to be measured at home using a cuff: Both wrist and upper arm devices are available for this purpose. Researchers at the University of Texas have now developed an advanced method: A kind of electronic tattoo, which is "worn" on the wrist for several hours, should be able to provide particularly accurate values - without the need for a cumbersome cuff. The principle of blood pressure measurement was presented in the scientific journal "Nature Nanotechnology".

Continuous measurement instead of instantaneous data

"Blood pressure is the most important vital sign you can measure, but the methods to measure it outside the clinic passively and without a cuff are very limited," said Deji Akinwande, a professor in UT Austin's Department of Electrical and Computer Engineering and one of the project's co-leaders. With conventional measurement, he said, only momentary data is recorded - but with the E-Tattoo, blood pressure is recorded continuously, allowing for better analysis.

For example, he said, it could conceivably be used to take measurements during high stress, sleep or exercise - without requiring sufferers to wear a cumbersome device that would hinder them in their daily lives and thus potentially falsify readings. "It can provide thousands of measurements, more than any other device to date," the team explains.

How does the e-tattoo work?

The central building block of the tattoo is the substance graphene: The material is very thin, yet stable. "It resembles graphite in pencils, but the atoms are precisely arranged in thin layers." Embedded in a sticky, stretchy material that encases the sensors, the "tattoo" can be applied and worn for an extended period of time without slipping or interfering. "The sensor for the tattoo is weightless and unobtrusive," explains Roozbeh Jafari, professor of biomedical engineering, computer science and electrical engineering. Once applied, he says, it is virtually invisible.

Measurements are made using electric current via the principle of bioimpedance: after small amounts of electricity are applied to the skin, the body's reactions are analyzed to evaluate blood pressure. The changes are based on changes in blood volume. The team created the correlation via a machine learning model to analyze the connections and obtain accurate blood pressure readings.

Easier to collect large amounts of data

In medicine, cuffless blood pressure measurement is the "Holy Grail," Jafari explained. However, he said, there is not yet a particularly viable solution on the market. "It's part of a larger push in medicine to use technology to untether patient:ing from machines while collecting more data wherever they are so they can go from room to room, clinic to clinic, and still get personalized care."

Meanwhile, smartwatches can also be used to collect various health data. These use metallic sensors that work with the help of LED light sources. "However, leading smartwatches are not yet ready for blood pressure measurement." That's because the watches slip on the wrist and may be too far away from the arteries, he said. In addition, the light-based measurements could show variations depending on skin type.