Researchers around the world are advancing a new class of microrobots engineered to deliver therapeutic drugs directly to blood clots, promising a profound shift in how strokes, vascular blockages and tumour-related vascular conditions may be treated. In one standout prototype study, the microrobot achieved more than a 95 percent success rate in laboratory models, signalling a major leap forward for targeted therapies.
These microrobots are typically the size of a grain of sand and use advanced magnetic or acoustic propulsion systems to navigate inside narrow blood vessels and reach their targets. Once in position, they release drug payloads precisely at the clot or lesion site, reducing damage to healthy tissues. In one Swiss-led study, a spherical capsule made of a soluble gel shell containing iron-oxide nanoparticles was steered via magnetic gradients through realistic vascular models. The researchers noted that the microrobot achieved over 95 percent success in reaching and treating the target region.
Another team from the University of Twente and Radboud University demonstrated that wireless magnetic microrobots removed clot material from a sheep’s iliac artery, restoring circulation through hybrid mechanical fragmentation and chemical lysis. Meanwhile, a study published in Small Science numerically simulated navigation of microrobots through patient-specific neurovascular networks, showing how constant magnetic gradients could steer the devices through complex anatomies.
Every year, strokes and thrombotic events caused by blood clots account for millions of deaths and major disabilities worldwide. Traditional therapies rely on systemic clot-busting drugs or large catheter-based interventions, each with significant risk and limited access to deep or small vessels. Microrobotic systems promise to deliver therapy at the clot itself, increasing localisation, reducing side-effects and potentially widening the treatment window. In tumour therapy, this approach could mean delivering chemotherapy directly into tumour-feeding vasculature without exposing the whole body to toxic drugs.
One recent platform integrated an electromagnetic navigation system, a custom release catheter and a dissolvable capsule holding magnetic and radiopaque nanoparticles plus therapeutic agents. This system proved viable in vitro and in vivo under fluoroscopy tracking, marking a major step toward human-ready microrobot drug delivery. Researchers at ETH Zurich developed modular magnetic microrobots capable of navigating against high blood flow velocities and sharp vessel junctions, using gradient-based pulling, rolling motion and in-flow navigation strategies. They successfully dissolved clots in more than 95 percent of tests.
“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,” said ETH Professor Bradley Nelson, a veteran in microrobotics research.
Material innovations are equally important. Teams from Nanyang Technological University and other institutions created microrobots built from soft hydrogels, magnetic microparticles and smart polymers, able to deform, travel safely inside vessels and release medications when triggered by external stimulus such as heat or magnetic field. Furthermore, microrobots have been used to enable 3D vascular imaging: swarms of magnetic robots mapped vessels in real time, highlighting blockages and anomalies traditional contrast agents miss.
While the initial focus is thrombotic clots and stroke, the potential reach is far broader. Studies propose using microrobots for cardiovascular disease treatments, guiding surgical micro-instruments, targeting neurological lesions, and treating localized infections.
Biohybrid microrobots, for example sperm-bots and Janus-particle based swimmers, are being developed for deep-tissue drug delivery, tumour penetration and other minimally-invasive therapies.
Despite the excitement, multiple challenges remain. First is regulatory approval and long-term safety: the body’s immune system, vascular complexity and possible toxicity from magnetic nanoparticles must all be addressed. Manufacturing at scale remains difficult and expensive; producing reproducible microrobots with clinical-grade materials is not yet routine.
Navigating real human vasculature, with variable flow, bifurcations, live blood cells and unpredictable anatomy, is far harder than lab models. Studies note that hemodynamic complexity, branching vessels and dense red-blood-cell flows pose genuine obstacles to safe navigation.
Human trials may begin in the coming years, initially in high-need areas like acute ischemic stroke or inaccessible tumour vasculature. Research efforts are now focused on improving robot autonomy, real-time imaging guidance, tool-integration (such as delivering clot-dissolving agents plus sensors) and combining microrobots with gene therapy, immunotherapy or other advanced treatments.
The broader aim is a future where micro-robots navigate inside us, locate disease, deliver treatment and disappear, all with minimal invasiveness. Th study was published in Science on November 13.