MIT engineers develop ultrasonic stickers that can see inside the body

Adhesive patch that produces ultrasound images of the body

MIT engineers designed an adhesive patch that produces ultrasound images of the body. The 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 ultrasonic adhesives deliver clear images of the heart, lungs and other internal organs.

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

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

To image with ultrasound, a technician first applies a liquid gel to a patient’s skin, which emits ultrasound waves. A probe, or transducer, is then pressed against the gel, sending sound waves into the body that bounce off internal structures and back to the probe, where the echo signals are converted into visual images.

For patients who require long periods of imaging, some hospitals offer probes attached to robotic arms that can hold a transducer in place without fatigue, but the liquid ultrasound gel drains and dries out over time, making long-lasting results. imaging is interrupted.

In recent years, scientists have explored designs for stretchable ultrasound probes that would provide portable, unobtrusive imaging of internal organs. These designs provided a flexible array of small ultrasound transducers, with the idea that such a device would stretch and conform to a patient’s body.

But these experimental designs have produced low-resolution images, in part because of their stretch: When moving with the body, the transducers shift relative to each other, distorting the resulting image.

“A portable ultrasound tool would have enormous potential in the future of clinical diagnosis. However, the resolution and image duration of existing ultrasound patches is relatively low, and they cannot image deep organs,” said Chonghe Wang, an MIT graduate. student.

A look inside

By combining a stretchable adhesive layer with a rigid array of transducers, the MIT team’s new ultrasound sticker produces higher-resolution images over a longer duration. “This combination allows the device to conform to the skin while preserving the relative location of the transducers to generate clearer and more accurate images.” says Wang.

The device’s adhesive layer is made of two thin layers of elastomer that encapsulate a middle layer of solid hydrogel, a largely water-based material that readily transmits sound waves. Unlike traditional ultrasonic gels, the MIT team’s hydrogel is elastic and stretchable.

“The elastomer prevents hydrogel drying out,” said Chen, an MIT postdoc. “Only when hydrogel is highly hydrated can acoustic waves effectively penetrate and provide high-resolution imaging of internal organs.”

The bottom elastomeric layer is designed to adhere to the skin, while the top layer adheres to a rigid array of transducers that the team also designed and fabricated. The entire ultrasonic sticker is about 2 square centimeters wide and 3 millimeters thick – about the area of ​​a postage stamp.

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

The images of the stickers allowed the team to observe the changing diameter of major blood vessels when sitting versus standing. The stickers also captured details of deeper organs, such as how the heart changes shape during exercise. The researchers were also able to watch the stomach swell and then recoil as volunteers drank and later passed the juice out of their system. And while some volunteers lifted weights, the team was able to detect bright patterns in underlying muscles, indicating temporary micro-damage.

“With imaging, we may be able to capture the moment of a workout before we overuse, and stop before the muscles get sore,” Chen says. “We don’t know when that moment will be yet, but now we can provide image data for experts to interpret.”

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

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

Reference: “Bioadhesive Ultrasound for Long-Term Continuous Imaging of Diverse Organs” by Chonghe Wang, Xiaoyu Chen, Liu Wang, Mitsutoshi Makihata, Hsiao-Chuan Liu, Tao Zhou, and Xuanhe Zhao, Jul 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 MIT’s Institute for Soldier Nanotechnologies.

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