MIT engineers are developing ultrasonic stickers that can see inside the body

MIT engineers developed an adhesive patch that produces ultrasound images of the body. The postage stamp-sized device sticks to the skin and can provide continuous ultrasound imaging of internal organs for 48 hours. Credit: Felice Frankel

New postage stamp-sized ultrasound adhesives provide clear images of the heart, lungs and other internal organs.

When doctors need live images of a patient’s internal organs, they often turn to ultrasound imaging for a safe and non-invasive look at how the body works. To capture these revealing images, trained technicians manipulate ultrasound wands and probes to direct sound waves into the body. These waves are reflected back out and used to create high-resolution images of a patient’s heart, lungs, and other deep organs.

Ultrasound imaging currently requires bulky and specialized equipment that is only available in hospitals and doctor’s offices. However, a new design was developed by

” data-gt-translate-attributes=”[{” attribute=””>MIT engineers might make the technology as wearable and accessible as buying Band-Aids at the drugstore.

The engineers presented the design for the new ultrasound sticker in a paper published on July 28 in the journal Science. The stamp-sized device sticks to skin and can provide continuous ultrasound imaging of internal organs for 48 hours.

To demonstrate the invention, the researchers applied the stickers to volunteers. They showed the devices produced live, high-resolution images of major blood vessels and deeper organs such as the heart, lungs, and stomach. As the volunteers performed various activities, including sitting, standing, jogging, and biking, the stickers maintained a strong adhesion and continued to capture changes in underlying organs.

In the current design, the stickers must be connected to instruments that translate the reflected sound waves into images. According to the researchers, the stickers could have immediate applications even in their current form. For example, the devices could be applied to patients in the hospital, similar to heart-monitoring EKG stickers, and could continuously image internal organs without requiring a technician to hold a probe in place for long periods of time.

Making the devices work wirelessly is a goal the team is currently working toward. If they are successful, the ultrasound stickers could be made into wearable imaging products that patients could take home from a doctor’s office or even buy at a pharmacy.

“We envision a few patches adhered to different locations on the body, and the patches would communicate with your cellphone, where AI algorithms would analyze the images on demand,” says the study’s senior author, Xuanhe Zhao, professor of mechanical engineering and civil and environmental engineering at MIT. “We believe we’ve opened a new era of wearable imaging: With a few patches on your body, you could see your internal organs.”

The study also includes lead authors Chonghe Wang and Xiaoyu Chen, and co-authors Liu Wang, Mitsutoshi Makihata, and Tao Zhao at MIT, along with Hsiao-Chuan Liu of the Mayo Clinic in Rochester, Minnesota.

A sticky subject

For ultrasound imaging, a technician first applies a liquid gel to a patient’s skin that acts to transmit ultrasound waves. A probe or transducer is then pressed against the gel and sends sound waves into the body, which bounce off internal structures and back to the probe, where the echo signals are translated into visual images.

For patients who need long imaging, some hospitals offer probes attached to robotic arms that can hold a transducer in place without fatigue, but the liquid ultrasound gel flows away and dries up over time, disrupting long-term imaging.

In recent years, scientists have been exploring designs for stretchable ultrasound probes that would allow for portable, flat imaging of internal organs. These designs resulted in a flexible array of tiny ultrasound transducers, the idea being that such a device would stretch and conform to a patient’s body.

However, these experimental designs have produced low-resolution images, in part because of their stretching: when moving with the body, the transducers shift their position relative to one another, distorting the resulting image.

“The handheld ultrasound imaging device would have tremendous potential for future clinical diagnostics. However, the resolution and imaging time of existing ultrasound patches is relatively low, and they cannot image deep organs,” says Chonghe Wang, an MIT graduate student.

A look inside

By pairing a stretchable adhesive layer with a rigid array of transducers, the MIT team’s new ultrasound sticker produces higher-resolution images over a longer period of time. “This combination allows the device to conform to the skin while maintaining the relative position of the transducers to produce clearer and more precise images,” says Wang.

The device’s adhesive layer consists of two thin layers of elastomer encapsulating a middle layer of solid hydrogel, a primarily water-based material that easily transmits sound waves. Unlike traditional ultrasound gels, the MIT team’s hydrogel is elastic and stretchable.

“The elastomer keeps the hydrogel from drying out,” says Chen, a postdoc at MIT. “Only when the hydrogel is highly hydrated can acoustic waves penetrate effectively and provide high-resolution images of internal organs.”

The bottom layer of elastomer is designed to stick to the skin, while the top layer sticks to a rigid array of transducers that the team also designed and manufactured. The entire ultrasonic sticker measures about 2 square centimeters in diameter and 3 millimeters thick – about the area of ​​a postage stamp.

The researchers ran the ultrasound sticker through a series of tests on healthy volunteers who wore the stickers on different parts of their bodies, including their necks, chests, abdomen and arms. The stickers stuck to their skin, producing clear images of underlying structures for up to 48 hours. During this time, the volunteers performed a variety of activities in the lab, from sitting and standing to jogging, cycling, and weight lifting.

Using the images of the stickers, the team was able to observe the changing diameter of the major blood vessels when sitting versus standing. The stickers also captured details from deeper organs, such as how the heart changes shape as it exerts itself during exercise. The researchers were also able to observe how the stomach expanded and then contracted as volunteers drank and later eliminated juice from their systems. And as some volunteers lifted weights, the team could see bright patterns in the underlying muscles that indicated temporary micro-damage.

“With imaging, we may be able to capture the moment in a workout before overuse and stop before the muscles hurt,” says Chen. “We don’t yet know when that moment might be, but now we can provide imagery that experts can interpret.”

The engineering team is working to make the stickers work wirelessly. They are also developing artificial intelligence-based software algorithms that can better interpret and diagnose the sticker images. Zhao then imagines that ultrasound stickers could be packaged and purchased by patients and consumers and used to monitor not only various internal organs but also the progression of tumors and the development of fetuses in the womb.

“We imagine we could have a box of stickers, each designed to represent a different part of the body,” says Zhao. “We believe this represents a breakthrough in wearable devices and medical imaging.”

Reference: “Bioadhesive Ultrasound for Long-Term Continuous Imaging of Various Organs” by Chonghe Wang, Xiaoyu Chen, Liu Wang, Mitsutoshi Makihata, Hsiao-Chuan Liu, Tao Zhou and Xuanhe Zhao, July 28, 2022, Science.
DOI: 10.1126/science.abo2542

This research was funded in part by MIT, the Defense Advanced Research Projects Agency, the National Science Foundation, the National Institutes of Health, and the US Army Research Office through the Institute for Soldier Nanotechnologies at MIT.