MIT researchers have created a super-thin robotic thread capable of carefully winding its way through a tangle of tubes. In the future, it could move through blood vessels in the brain to help clear blockages, according to a new the study in Science Robotics.
Currently, when a person is diagnosed with a blockage or aneurysm in the brain, surgeons insert a thin wire into an artery near the leg or groin, according to an MIT press release. Then, guided by X-ray images from a fluoroscope, a surgeon manually threads the wire through the body, up into the brain and maneuvers it to remove the blockage. It’s a highly specialized skill and surgeons are often exposed to excess radiation due to the imaging. In general, there are not enough trained surgeons to meet the need.
“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,” says Xuanhe Zhao, an MIT engineer and study co-author. “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.”
The new robot is essentially an upgraded version of the guidewires currently used by surgeons. Those wires are typically metal alloys coated in polymers. If they get stuck in a tight spot, they could cause friction and damage blood vessels.
For the new robot, the team combined their expertise in magnetically actuated materials, or those that can be moved via magnets and hydrogels, a biocompatible material made primarily of water.
The new brain worm is coated with hydrogel to produce a smooth, frictionless movement. The guidewire is made of a bendy nickel-titanium alloy called nitinol covered in an ink studded with magnetic particles and is only 0.6 millimeters in diameter.
The result is the robo-worm, which the team was able to steer through a series of plastic hoops just using the push and pull of a magnet. They also guided the little thread through silicon replica of brain vasculature, finding that the slippery hydrogel kept the wire from getting stuck better than conventional guidewires.
The hope is that a specialized magnetic machine could be built to guide the thread through the body. That type of platform would allow surgeons to control the process using a joystick in a spot away from the fluoroscope radiation—or even from a different city.
The team also says it would be possible to delivery clot-reducing drugs using the robot or even clot-busting laser pulses. In another experiment, they replaced the nitinol core with an optical fiber and found they could still steer the robot and activate a laser.
Co-author Yoonho Kim, a graduate student in MIT's Department of Mechanical Engineering, acknowledges that the idea is not particularly groundbreaking. Other teams have experimented with other soft robots to clear blockages in the heart. The brain, however, was a tougher organ to crack.
“The reason why robotics couldn’t go into this domain before is the existing robots that can navigate through a blood vessel were too large in diameter,” Kim tells Chris Stokel-Walker at New Scientist.
While the system is in its very early stages, it appears viable. “I think it’s really interesting – and the clinical implications are there, if at a very early stage,” Eloise Matheson who studies robotics at Imperial College London tells Stokel-Walker. “The system, how they tested it and what it shows, is really promising.”
The next step is to try the robo-worm out on animals, and the team is currently in negotiations to set up those experiments.