MIT engineers have developed robotic thread that can be steered magnetically and is small enough to work through narrow spaces such as the vasculature of the human brain. The researchers envision the technology may be used in the future to clear blockages in patients with stroke and aneurysms.
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.
So, the MIT researchers wanted to design a device to reverse blood vessel blockage within this ‘golden hour to avoid permanent brain damage.
To clear blood clots in the brain, doctors often perform an endovascular procedure, a minimally invasive surgery in which a surgeon inserts a thin wire through a patient’s main artery, usually in the leg or groin. Guided by a fluoroscope that simultaneously images the blood vessels using X-rays, the surgeon then manually rotates the wire up into the damaged brain vessel. A catheter can then be threaded up along the wire to deliver drugs or clot-retrieval devices to the affected region.
This procedure can be physically taxing, requiring skilled surgeons to endure repeated radiation exposure from fluoroscopy.
The medical guidewires used in such procedures are passive, meaning they must be manipulated manually, and are typically made from a core of metallic alloys, coated in polymer, a material that could potentially generate friction and damage vessel linings if the wire were to get temporarily stuck in a particularly tight space.
Over the past few years, the MIT research team has built up expertise in both hydrogels — biocompatible materials made mostly of water — and 3-D-printed magnetically-actuated materials that can be designed to crawl, jump, and even catch a ball, simply by following the direction of a magnet.
Now the researchers combined their work in hydrogels and in magnetic actuation, to produce a magnetically steerable, hydrogel-coated robotic thread, or guidewire, which they were able to make thin enough to magnetically guide through a life-size silicone replica of the brain’s blood vessels.
The core of the robotic thread is made from nickel-titanium alloy, or “nitinol,” a material that is both bendy and springy. Unlike a clothes hanger, which would retain its shape when bent, a nitinol wire would return to its original shape, giving it more flexibility in winding through tight, tortuous vessels.
Finally, they used a chemical process they developed previously, to coat and bond the magnetic covering with hydrogel — a material that does not affect the responsiveness of the underlying magnetic particles and yet provides the wire with a smooth, friction-free, biocompatible surface.
They demonstrated the robotic thread’s precision and activation by using a large magnet, to steer the thread through an obstacle course of small rings, reminiscent of a thread working its way through the eye of a needle.
The researchers also tested the thread in a life-size silicone replica of the brain’s major blood vessels, including clots and aneurysms, modeled after the CT scans of an actual patient’s brain. The team filled the silicone vessels with a liquid simulating the viscosity of blood, then manually manipulated a large magnet around the model to steer the robot through the vessels’ winding, narrow paths.
This robotic thread keeps the surgeons radiation-free by avoiding the need for the close proximity of
News Source: MIT
