Asger Risom
Researchers in Switzerland are testing a new way to deliver lifesaving stroke medication.
Researchers in Switzerland are testing a new way to deliver lifesaving stroke medication — by steering microscopic gel capsules through the bloodstream using magnetic fields.
If proven safe in humans, the technique could one day replace high-dose drug injections that carry serious risks for patients.
A New Approach to Stroke Treatment
Reporting from Science describes how ETH Zurich engineers have developed dissolvable microrobots designed to travel directly to blocked blood vessels. Unlike autonomous machines, these are tiny beads packed with clot-busting drugs, iron oxide nanoparticles for magnetic control and a small amount of tantalum so doctors can track them using X-ray.
Current stroke therapies rely on powerful injections to dissolve a thrombus, the vessel-blocking clot that cuts off oxygen to the brain. Because medication disperses throughout the circulatory system, doctors must use large doses — which raises the chance of dangerous side effects such as internal bleeding.
The ETH Zurich team believes that delivering medication directly to the blockage could dramatically cut the required dosage and reduce complications.
Building a Steerable Microrobot
The microrobot is a soft gel capsule engineered to be small enough to pass through the narrow vessels of the brain. “Because the vessels in the human brain are so small, there is a limit to how big the capsule can be. The technical challenge is to ensure that a capsule this small also has sufficient magnetic properties,” researcher Fabian Landers said in a statement.
To achieve that balance, the team packed the capsule with iron oxide particles for magnetization and added tantalum nanoparticles for visibility during imaging. After years of testing, they now report a device capable of navigating the body’s roughly 360 arteries and veins.
Coauthor Bradley Nelson explained why their steering method is promising: “Magnetic fields and gradients are ideal for minimally invasive procedures because they penetrate deep into the body and–at least at the strengths and frequencies we use–have no detrimental effect on the body.”
Navigating Complex Blood Flow
Before testing in animals, researchers released the microrobots into silicone models of human and animal vessels. A specially designed catheter, equipped with a polymer gripper and guidewire, injects the capsule into the bloodstream.
Nelson noted that navigation depends heavily on location: “The speed of blood flow in the human arterial system varies a lot depending on location. This makes navigating a microrobot very complex.”
To overcome that challenge, the team combined three magnetic steering strategies. One rotating magnetic field allowed smooth control at speeds up to 4 millimeters per second. A shifting magnetic gradient pulled the device along stronger fields, enabling the microrobot to move even against blood flow at speeds reaching 20 centimeters per second.
“It’s remarkable how much blood flows through our vessels and at such high speed,” Landers said. “Our navigation system must be able to withstand all of that.”
Promising Early Tests
After successful lab trials, the team progressed to animal studies. 95 percent of pig-model tests ended with the microrobot delivering its medication to the correct location. Additional experiments in a sheep’s cerebrospinal fluid suggested broader therapeutic uses beyond stroke care.
Landers described the potential impact on future procedures: “This complex anatomical environment has enormous potential for further therapeutic interventions, which is why we were so excited that the microrobot was able to find its way in this environment, too.”
What Comes Next
The microrobot remains in early-stage research, and human trials are still ahead. Scientists must assess long-term safety, how the capsule dissolves, how well magnetic fields perform in different patients and whether the approach reduces side effects in real clinical settings.
Still, the work points toward a future where targeted microrobotics could transform how doctors treat strokes — and potentially many other neurological or vascular conditions.
This article is made and published by Asger Risom, who may have used AI in the preparation
