Soft Skin Patch To Monitor Blood Flow Continuously

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Engineers developed a thin, flexible and stretchable patch that can monitor the blood flowing through blood vessels deep inside a person’s body. 

Monitoring blood flow is critical in medical specialties. Knowing how fast and how much blood flows through the blood vessels is important as it can help doctors identify various cardiovascular conditions such as blood clots, heart valve problems; poor circulation in the limbs; or blockages in the arteries that could lead to strokes or heart attacks.

Engineers at the University of California San Diego have developed a soft skin patch to monitor the blood flow in major arteries and veins. It can continuously monitor the blood flow, as well as blood pressure and heart function — in real time. According to the engineers, wearing such a device makes it easier to identify cardiovascular conditions early on. The work is published in Nature Biomedical Engineering.

The patch can be worn on the neck or chest. One of the unique features is that this patch can monitor blood flow deep inside the person’s body, as deep as 14 centimeters.

“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.”

The Patch is made up of an array of millimeter-sized ultrasound transducers. The base is made up of an ultra-thin, flexible and stretchable polymer that adheres to the skin. Each ultrasound transducer is computer controlled. This type of technology is called ultrasound phased array. This allows monitoring deeper into the body.

The phased array works in two modes. In the first mode, all the transducers are synchronized and transmit the ultrasound waves together. This produces a high intensity ultrasound beam focused on one spot as-deep-as 14 centimeters into the body. In the second mode, the transducers are programmed to transmit out-of-sync. This produces a beam that can be steered to different angles. 

The phased array consists of a 12 x 12 grid of transducers. When electricity flows through the transducers, they vibrate and emit ultrasound waves that travel through the skin. These ultrasound waves encounter the movement of red blood cells flowing inside. The movement of the cells shifts the frequency of the ultrasound echo back to the patch. This phenomenon is called doppler frequency shift. With this shift, one can create a visual recording of the blood flow. Moreover, it can also be used to create moving images of the heart’s wall.

The researchers say that the patch still has a long way to go before it is ready for the clinic. Currently, it needs to be connected to a power source and benchtop machine in order to work. The researchers are working on integrating all the electronics on the patch to make it wireless.


 

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