MIT engineers have developed a small ultrasound sticker that can monitor the stiffness of organs deep inside the body. The sticker, about the size of a postage stamp, can be worn on the skin and is designed to pick up on signs of disease, such as liver and kidney failure and the progression of solid tumors.
How the sticker works
The sensor can send sound waves through the skin and into the body, where the waves reflect off internal organs and back out to the sticker. The pattern of the reflected waves can be read as a signature of organ rigidity, which the sticker can measure and track.
When some organs undergo disease, they can stiffen over time. With this wearable sticker, we can continuously monitor changes in rigidity over long periods of time, which is crucially important for early diagnosis of internal organ failure, says Xuanhe Zhao, professor of mechanical engineering at MIT and the senior author of the paper.
The sticker is made of a thin layer of piezoelectric material, which can generate electric signals when deformed by sound waves. The material is cut into small transducers that can emit and receive ultrasound waves. The transducers are arranged in a grid pattern on a flexible substrate and connected to a microcontroller that can process the signals and transmit them wirelessly to a smartphone or computer.
Potential applications and benefits
The team has demonstrated that the sticker can continuously monitor the stiffness of organs over 48 hours and detect subtle changes that could signal the progression of disease. In preliminary experiments, the researchers found that the sticky sensor can detect early signs of acute liver failure in rats.
The engineers are working to adapt the design for use in humans. They envision that the sticker could be used in intensive care units (ICUs), where the low-profile sensors could continuously monitor patients who are recovering from organ transplants.
We imagine that, just after a liver or kidney transplant, we could adhere this sticker to a patient and observe how the rigidity of the organ changes over days, says Hsiao-Chuan Liu, the lead author of the paper and a visiting scientist at MIT at the time of the study. He is currently an assistant professor at the University of Southern California.
The sticker could also help diagnose and monitor cancer, as solid tumors tend to be stiffer than healthy tissue. The sticker could provide a non-invasive and continuous way to track the growth and response of tumors to treatment.
Challenges and future directions
The team acknowledges that there are some challenges and limitations to the current design of the sticker. For instance, the sticker needs to be calibrated for each individual and each organ, as different organs have different baseline stiffness and acoustic properties. The sticker also needs to be attached to the skin with a strong adhesive, which could cause skin irritation or damage.
The team plans to address these issues by improving the materials and algorithms of the sticker. They also hope to test the sticker on larger animals and eventually on humans. They believe that the sticker could be a game-changer for health monitoring and disease management.
The study, titled “Wearable ultrasound stickers for continuous monitoring of organ stiffness,” was published in Science Advances on February 9, 2024. The study’s MIT co-authors include Xiaoyu Chen and Chonghe Wang, along with collaborators at USC.