Blood flow monitored with stretchable ultrasound patch

Engineers have developed a stretchable polymer ultrasound patch that adheres to skin to monitor blood flow through major arteries and veins.  

ultrasound patch
This soft, stretchy skin patch uses ultrasound to monitor blood flow to organs like the heart and brain (Image: Nature Biomedical Engineering)

The new ultrasound patch developed at the University of California San Diego can continuously monitor blood flow, blood pressure and heart function in real time. Wearing such a device could make it easier to identify the onset of cardiovascular problems.

A team led by Sheng Xu, a professor of nanoengineering at the UC San Diego Jacobs School of Engineering, reported the patch in a paper published in Nature Biomedical Engineering.

The patch, which can be worn on the neck or chest, can accurately and non-invasively sense and measure cardiovascular signals as deep as 14cm inside the body.

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“This type of wearable device can give you a more comprehensive, more accurate picture of what’s going on in deep tissues and critical organs like the heart and the brain, all from the surface of the skin,” Xu said in a statement.

“Sensing signals at such depths is extremely challenging for wearable electronics. Yet, this is where the body’s most critical signals and the central organs are buried,” said Chonghe Wang, a former nanoengineering graduate student in Xu’s lab and co-first author of the study. “We engineered a wearable device that can penetrate such deep tissue depths and sense those vital signals far beneath the skin. This technology can provide new insights for the field of healthcare.”

According to UC San Diego, the patch is made up of a thin sheet of flexible, stretchable polymer that adheres to the skin. Embedded on the patch is an array of millimetre-sized ultrasound transducers that are individually controlled by a computer, which allows the patch to go deeper and wider.

The phased array is said to offer two main modes of operation. In one mode, all the transducers can be synchronised to transmit ultrasound waves together, which produces a high-intensity ultrasound beam that focuses on one spot as deep as 14cm. In the other mode, the transducers can be programmed to transmit out of sync, which produces ultrasound beams that can be steered to different angles.

“With the phased array technology, we can manipulate the ultrasound beam in the way that we want,” said Muyang Lin, a nanoengineering Ph.D. student at UC San Diego who is also a co-first author of the study. “This gives our device multiple capabilities: monitoring central organs as well as blood flow, with high resolution. This would not be possible using just one transducer.”

The phased array consists of a 12 x 12 grid of ultrasound transducers. When the ultrasound waves penetrate through a major blood vessel, they encounter movement from red blood cells flowing inside. This movement changes or shifts how the ultrasound waves echo back to the patch. This shift in the reflected signals gets picked up by the patch and is used to create a visual recording of the blood flow. This same mechanism can also be used to create moving images of the heart’s walls.

The researchers caution that the patch still has a long way to go before it can be commercialised; it needs to be connected to a power source and benchtop machine to work. Xu’s team is working on integrating the electronics on the patch to make it wireless.