What would you do when you see hair gathered in the drain while showering? When you place the hair in your palm and rub it with both hands, it tends to shrink like a small ball. The same goes for dog or cat fur. Everyday experiences have evolved into medical technologies that prevent heart attacks and strokes. It is a method of removing blood clots that block blood vessels by clumping them together like hair.
A research team led by Ruike Renee Zhao, a professor of mechanical engineering at Stanford University, and Jeremy Heit, a professor of radiology at the medical school, announced on Nov. 4 (local time) in the international journal Nature, that they developed a technology to remove blood clots by clumping and compressing the fibrous proteins that make up the clots.
◇Reduce blood clot volume to 5% like clumped hair
Blood clots are sticky masses formed when fibrin proteins, like threads, trap red blood cells. When a blood clot blocks oxygen to the brain, a stroke occurs. At this time, doctors race against the clock. The faster blood clots are removed, the more brain cells can be saved. However, the current technology has a success rate of only 50% for successfully removing blood clots on the first attempt.
The Stanford research team developed a method to remove blood clots by inserting a micro-rotational device into blood vessels. Professor Heit noted, "With current technology, we can remove only about 11% of a solid blood clot, but with the newly developed technology, we removed 90% on the first attempt." The research team expressed expectations that the same method could prevent strokes, myocardial infarction (heart attack), and pulmonary embolism caused by blood clots.
Currently, medical staff remove blood clots using machinery and equipment. They insert a thin tube into the blood vessels to suction out the clots like a vacuum cleaner, or they spread a metal mesh shaped like a stent (a small tube for expanding blood vessels) to allow the clots to stick together and then remove them. However, the initial success rate remains at only half, with 15% of cases failing even after multiple attempts. Blood clots may break apart while being deformed or crushed, resulting in small fragments wedged in hard-to-reach areas.
Professor Zhao, the corresponding author of the paper, stated, "The advantage of the newly developed milli-spinner is that it can significantly reduce the volume of blood clots by applying compression and shear force, allowing them to be easily removed without breaking apart." She added, "In experiments, we reduced the blood clot volume to 5% of its original size."
The principle is similar to what we experience in everyday life. When you compress and rub a puffy substance like hair or dog fur between your hands, shear forces act to make it slip and break into a small ball shape. Rotating the micro-rotational device in the blood vessels produces similar effects, applying compression and shear forces to group the fibrins together for easy suction. Red blood cells released from the fibrins flow into the blood vessels.
◇Application to stone removal, commercialization underway
Professor Zhao was initially developing a medical micro-robot that navigates through blood vessels. She confirmed that the rotational device creating the driving power for the robot also generates localized suction in blood vessels, which has been developed into a blood clot removal technology.
Professor Zhao noted, "When we tested the rotational device for the robot in blood vessels, we observed that the color of the blood clot changed from red to white, and its volume dramatically decreased. Honestly, it felt like magic at the time, and I did not fully understand the mechanism." The research team confirmed that it was based on the same principle of compressing hair clumps while modifying the design of the rotational device hundreds of times.
The research team stated they are currently studying a mobile micro-rotational device that can swim freely through blood vessels to remove blood clots. Professor Zhao mentioned, "We are currently focusing on blood clot treatment, but there are many potential applications." She added, "We are already researching capturing and removing kidney stone fragments using the localized suction capability of the micro-rotational device." The research team plans to establish a startup to commercialize the technology and is also planning clinical trials in the near future.
References
Nature (2025), DOI: https://doi.org/10.1038/s41586-025-09049-0