A snaking, magnetically controlled robot capable of maneuvering through some of the body’s narrowest arteries could one day help prevent deaths associated with strokes and aneurysms.
With a magnetic interior and a “growing” friction-reducing hydrogel, the thread-like robot can seamlessly glide through “complex and constrained" environments like vascular structures in the body and brain, describe engineers at Massachusetts Institute of Technology (MIT) in the journal Science Robotics. When paired with currently used endovascular technologies, it may allow doctors to quickly treat hard-to-reach blockages and lesions in the brain that occur in aneurysms and strokes.
“Stroke is the number five cause of death and a leading cause of disability in the United States. If acute stroke can be treated within the first 90 minutes or so, patients’ survival rates could increase significantly,” said Xuanhe Zhao, associate professor at MIT, in a statement. “If we could design a device to reverse blood vessel blockage within this ‘golden hour,’ we could potentially avoid permanent brain damage. That’s our hope.”
Current treatments are minimally invasive yet arduous. To clear blood clots in the brain, surgeons navigate a thin wire through a main artery in the body, often through the leg or groin, while a radiation-emitting fluoroscope takes photos and X-rays to help guide the wire to the brain. A catheter then either delivers clot-reducing drugs or a device retrieves the clot. But this process is taxing and requires specially trained doctors who endure radiation exposure over time.
“One of the challenges in surgery has been to be able to navigate through complicated blood vessels in the brain, which has a very small diameter, where commercial catheters can’t reach,” said Kyujin Cho, professor of mechanical engineering at Seoul National University. “This research has shown potential to overcome this challenge and enable surgical procedures in the brain without open surgery.”
That’s where the robotic thread comes in, building on years of research surrounding water-retaining hydrogels and 3D-printed materials that use magnets to crawl and jump. The hydrogel coat keeps the thread smooth and reduces friction by more than 10 times, while magnetics in the second layer allow for a surgeon outside of the room to operate and maneuver the threading throughout the human body, reducing exposure to radiation from the fluoroscopes. Its core is made of nickel-titanium alloy, or nitinol, that is bendy yet able to return to its natural shape, allowing for flexible winding through tight vessels. Together, the threading is below a few hundreds of micrometers in diameter.
“Given their compact, self-contained actuation and intuitive manipulation, our ferromagnetic soft continuum robots may open avenues to minimally invasive robotic surgery for previously inaccessible lesions, thereby addressing challenges and unmet needs in healthcare,” write the authors.
Researchers tested the technology on a life-size silicone replica of the brain’s blood vessels, complete with realistic clots and aneurysms and a blood-like liquid. Though promising, the trials were operated under the eyes of an operator and not under conditions as difficult as when entering the human body. Additionally, the magnetic steering was done by adjusting the position of a single permanent magnet, not in ways that might mimic those used in the operating room.
Regardless, the authors say their work may lend to a more effective and simplistic treatment in the near future.