Globally, one in every four deaths each year is attributed to conditions caused by blood clots, which block blood vessels and prevent oxygen delivery to various body parts. While surgeons can use flexible instruments to eliminate these clots and restore blood flow, accessing certain body regions remains a challenge. Now, millirobots can overcome these limitations and offer a solution for removing blood clots from hard-to-reach vessels.

For the first time, researchers from the University of Twente (Enschede, Netherlands) and Radboudumc (Nijmegen, Netherlands) have been successful in making wireless millirobots navigate through a narrow blood vessel both along and against the arterial flow. These screw-shaped robots were inserted into a detached aorta with kidneys and controlled remotely using a robotically operated rotating magnet. Key requirements for millirobots to traverse blood vessels include the need for power, the ability to travel upstream and downstream, precise control and localization, biocompatibility, and ensuring no additional damage to the blood vessel's interior.

In their research setup comprising a real aorta and kidneys, the team utilized a robotic system to wirelessly control the millirobots using a rotating magnetic field. They employed an X-ray machine for real-time localization and navigation of the millirobot inside the aorta. During their experiments, they maintained an arterial flow of 120 ml per minute within the aorta, hypothesizing that a stronger magnetic field could enable the robots to counteract even higher blood flows. The millirobots demonstrated stable navigation in both directions of the flow and could operate simultaneously with multiple units.

These robots are manufactured through 3D printing, featuring a screw-like design with an embedded one-millimeter-long and one-millimeter-diameter permanent magnet. This magnet allows the millirobot to rotate in both directions, facilitating movement against the flow and then back again. Their small size permits the simultaneous use of several robots. The screw design is particularly effective for drilling through blood clots. The team aims to further refine the millirobots for wireless clot removal. In addition to clearing blood clots to restore arterial blood flow, this technology holds potential for other targeted medical interventions.

“These millirobots have huge potential in vascular surgery,” said Michiel Warle, a vascular surgeon at Radboudumc. “Currently, we use blood thinners and flexible tools, but a millirobot can travel to hard-to-reach arteries while they only need minimal incisions to be inserted.”

“The robots can deliver drugs to very specific places in the body where the drug is needed the most,” added researcher Islam Khalil. “That way we have minimal side effects in the rest of the body.” 

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