Researchers from Northwestern University and Washington University School of Medicine in St. Louis have developed a groundbreaking sticker that allows clinicians to monitor patients’ organs and deep tissues using a simple ultrasound device. This first-of-its-kind sticker can detect health changes in real-time, potentially revolutionizing post-surgery care.

When attached to an organ, the soft, tiny sticker changes shape in response to the body’s fluctuating pH levels, serving as an early warning system for complications such as anastomotic leaks. These leaks occur when gastrointestinal fluids escape the digestive system, posing a life-threatening risk. Currently, no reliable non-invasive methods exist to detect these leaks.

The innovative sticker is designed to reveal fluid leakage with high sensitivity and specificity, enabling earlier interventions. When the patient has fully recovered, the biocompatible and bioresorbable sticker dissolves naturally, eliminating the need for surgical removal.

Published in the journal Science, the study details evaluations across small and large animal models. The researchers validated three different types of stickers made from hydrogel materials, each tailored to detect leaks from the stomach, small intestine, and pancreas.

“These leaks can arise from subtle perforations in the tissue, often as imperceptible gaps between two sides of a surgical incision,” said John A. Rogers from Northwestern University, who led the device development alongside postdoctoral fellow Jiaqi Liu. “Such defects are undetectable with current ultrasound, CT, and MRI scans. We developed an engineering approach and advanced materials to address this unmet need in patient monitoring. This technology has the potential to eliminate risks, reduce costs, and expand accessibility to rapid, non-invasive assessments for improved patient outcomes.”

Rogers’ team designed the sensor devices to be readable by ultrasound imaging. They created small, tissue-adhesive stickers from flexible, chemically responsive hydrogels and embedded tiny, paper-thin metal disks. When the sticker encounters acidic fluids, such as stomach acid, it swells. In the presence of caustic fluids, like pancreatic fluids, it contracts. These changes cause the metal disks to move, which can be detected by ultrasound.

The stickers vary in size, with the largest being 12 mm in diameter and the smallest just 4 mm. Considering the metal disks are 1 mm or smaller, the team developed software to automatically analyze the images and accurately detect disk movements.

“There is currently no reliable way to detect these kinds of leaks,” said Dr. Chet Hammill, a gastrointestinal surgeon who led the clinical evaluation and animal studies with collaborator Dr. Matthew MacEwan, an Assistant Professor of Neurosurgery. “Most abdominal operations carry a risk of leaking. While we can’t fully prevent these complications, early detection can minimize harm. This technology could change how we monitor patients after surgery, potentially catching leaks 24-48 hours earlier.”

Rogers and Hammill envision that the device could be implanted at the end of surgery or injected into the body via a syringe due to its small, flexible nature.

“This prototype could transform post-surgical monitoring,” Hammill said. “It does its job and then disappears, significantly impacting patient recovery time and quality of life.”

Next, the team plans to explore similar tags that could detect internal bleeding or temperature changes. “Detecting pH changes is a good starting point,” Rogers said. “But this platform can extend to other applications by using hydrogels that respond to different chemical changes or temperature, or other clinically relevant properties.”

By Impact Lab