Dissolving blood clots with flow-generating microbots

A blood clot can restrict the blood flow in a blood vessel to such an extent that the medications intended to dissolve it can barely reach their target. Microbots driven by magnetic fields could now provide an unusual solution to this problem.

09.11.2026 by Fabio Bergamin, Corporate Communications
(Image edited with AI: Piyset / Adobe Stock, Montage: ETH Zurich)

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In brief

• Researchers at ETH Zurich have developed microbots from a biocompatible gel containing magnetic nanoparticles that they can insert into blood vessels. 

• Driven by a magnetic field, the bots move around and help to dissolve blood clots by transporting medications directly to them.

• Initial experiments have demonstrated the new method’s efficacy. A patent application has already been filed. 

When a blood clot blocks a blood vessel, it is a very dangerous situation, as it can mean that parts of the brain, the heart muscle or the lungs no longer receive an adequate blood supply. This can result in a stroke, a heart attack or a lung embolism. There are medications that can dissolve a blood clot – also known as a thrombus. However, depending on the clot’s size, getting them to where they are needed can be difficult. 

Physicians often use a catheter to bring the medications close to the thrombus via the bloodstream. The blood then helps to flush them to the clot. However, if the blood flow is not intact because the thrombus itself is blocking it, the medication will struggle to reach its target. In such cases, they can only move forwards very slowly via the physical process of diffusion. This costs time – and in some cases, human lives. 

Researchers from the group led by Simone Schürle, Professor of Medical Microsystems, have now developed a solution: magnetically guided microbots that significantly improve the transportation of medication to the site of the clot. 

Shaped like a tiny cocoon or oblong grain, they are made of a biocompatible gel into which magnetic iron oxide nanoparticles are embedded. The microbots are around eight micrometres long, i.e. less than one hundredth of a millimetre. “They are about as large as red blood cells, so their size is ideal”, Schürle says. 

Microbots generate flow like a gymnast 

The idea is to get the magnetic gel bots, along with the thrombus-dissolving medication, close to the blood clot with the help of a catheter. Driven by a magnetic field, the bots begin to rotate. The magnetic field is generated by a special magnetic control system outside the body. 

The rotation is used to guide the microbots towards the thrombus along the blood vessel wall. Their movement is comparable to that of a gymnast doing one handspring after another along the floor. The microbots propel themselves forwards through a series of “somersaults”. In the process, they also pull and push the surrounding blood. The small flows this creates help to transport the active substances to the clot. As a result, the medicines reach their target and are able to dissolve it faster and more effectively.

Thrombus dissolves six times faster 

The microbots have not yet been used in human patients. Among other things, the researchers have tested them in the laboratory on a silicon model containing channels based on blood vessels. In this model, created specifically for the experiments, the researchers used clots made from pig’s blood. Aided by the moving microbots, the medication dissolved the clot six times faster than without the bots. 

Together with scientists from the Charité University Hospital in Berlin, the ETH researchers also investigated the new method’s safety and efficacy in live pigs. Having blocked the animals’ arteries with a clot, the scientists tested how strongly the rotating microbots increased the medication’s efficiency in terms of dissolving the blood clot. After 30 minutes, the area of blood vessel to which the blood flow had been restored was twice as large as it was with the medication alone. “To our knowledge, we are the first to show in a clinically relevant large-animal model that the use of microrobots in this way does indeed enhance thrombolysis, i.e. the process of dissolving blood clots”, Schürle says. 

ETH Zurich has applied for a patent on the bots. It has also nominated the invention for the Spark Award, a prize with which the university honours the most promising patent application of the year. The researchers have recorded their results in a scientific paper, which is undergoing peer review prior to publication. 

Driven by magnetic backbone 

The microbots are made from a gel consisting of biocompatible sugar polymer into which iron oxide nanoparticles are embedded. To ensure that the oblong “cocoons” react to a magnetic field like a compass needle, the iron oxide nanoparticles are not distributed evenly within them, but rather clustered along the longitudinal axis. The researchers achieve this by producing the microbots in a rotating magnetic field.

Further tests are needed before the new invention can be used in patients with acute vascular obstruction. Next, the team wants to investigate the microbots’ safety in animals over longer periods of time. Further tests would also have to be carried out in specific models, such as heart-attack models, before the invention can be approved.