Microswimmer Robots Developed For Breaking Through Blocked Arteries

Armies of magnetic, microscopic, robotic beads could be on call for vascular surgeons taking aim at blocked arteries.

Looking and moving like corkscrew-shaped bacteria, the microrobots are being developed by mechanical engineers at Drexel University as one component of a surgical toolkit being assembled by the Daegu Gyeongbuk Institute of Science and Technology (DGIST) in South Korea.

Drexel’s MinJun Kim, PhD, professor in the College of Engineering is putting his team’s research in bio-inspired microrobotics to work in an $18-million international research initiative from the Korea Evaluation Institute of Industrial Technologies (KEIT).

The initiative aims to create a minimally invasive, microrobot-assisted procedure for dealing with blocked arteries within five years.

“Microrobotics is still a rather nascent field of study, and very much in its infancy when it comes to medical applications,” Kim said. “A project like this, because it is supported by leading institutions and has such a challenging goal, is an opportunity to push both medicine and microrobotics into a new and exciting place.”

Kim’s microswimmers consist of chains of three or more iron oxide beads, linked together rigidly by chemical bonds and magnetic force.

The chains are small enough, on the order of nanometers, that they can travel in the bloodstream like a tiny submarine. The beads’ motion is driven by an external magnetic field that causes each of them to rotate.

“Our magnetically actuated microswimmer technology is the perfect fit for this project,” Kim said. “The microswimmers are composed of inorganic biodegradable beads so they will not trigger an immune response in the body. And we can adjust their size and surface properties to accurately deal with any type of arterial occlusion.”

Because they are linked together, their individual rotations cause the chain to twist like a corkscrew and this movement propels the microswimmer.

Kim can direct the speed and direction of the microswimmers by manipulating the magnetic field. The magnetism involve also allows the researchers to join strands of microswimmers together to make longer strings, which can then be propelled with greater force.

Using magnetic fields (visual representation at right) generated by an electromagnetic device (left) Drexel engineers are able to control the movement of their micro-swimmer robots.

Using magnetic fields (visual representation at right) generated by an electromagnetic device (left) Drexel engineers are able to control the movement of their micro-swimmer robots.

This procedure could replace the two most common methods for treating blocked arteries: stenting and angioplasty.

Stenting creates a bypass for blood to flow around the block by inserting a series of tubes into the artery, while angioplasty pushes out the blockage by expanding the artery with help from an inflatable probe.

“Current treatments for chronic total occlusion are only about 60 percent successful,” Kim said. “We believe that the method we are developing could be as high as 80-90 percent successful and possibly shorten recovery time.”

U. Kei Cheang, Min Jun Kim
Self-assembly of robotic micro- and nanoswimmers using magnetic nanoparticles
Journal of Nanoparticle Research March 2015, 17:145

Photo: Drexel’s microswimmer robots (bottom) are modeled, in form and motion, after the spiral-shaped bacteria, Borrelia burgdorferi (top), that cause Lyme Disease.