Imagine a future where cancer treatment affects only the tumour. Where eye injections are no longer necessary. Where brain surgery doesn't require a large incision, a long recovery, or the removal of healthy tissue. That future is the explicit goal of researchers at Michigan State University — and a new breakthrough has just moved it considerably closer.
The system is called **TriMag**. It is a microrobot smaller than a human hair. And it may be one of the most versatile medical devices ever engineered at microscopic scale.
**Three Capabilities, One Device**
The word 'microrobot' has been used in medicine for years, but previous designs suffered from a fundamental limitation: they could navigate, or they could image, or they could treat — rarely all three simultaneously, and rarely with the precision needed to be clinically useful in dense, complex tissue like the brain or eye.
TriMag changes that. The device integrates three distinct magnetic capabilities in a single structure smaller than a grain of fine sand:
**1. Magnetic actuation** — Using external magnetic fields, TriMag can be wirelessly steered through the body with precision. The microrobots swim through fluid environments and navigate dense tissue, guided from outside the patient's body without any physical contact. They don't require surgery to deliver. They can be injected, swallowed, or applied to the skin, depending on the procedure.
**2. Magnetic particle imaging (MPI)** — This is the breakthrough within the breakthrough. Current imaging techniques struggle to track tiny objects through dense tissue in real time without radiation. TriMag's embedded iron oxide and cobalt ferrite nanoparticles allow it to be tracked in real-time 3D — through organs, through bone, through dense porcine brain tissue in laboratory tests — producing high-resolution images with no radiation and no interference from surrounding structures. Surgeons will be able to watch the microrobot move, in real time, from outside the body.
**3. Magnetic hyperthermia** — Once at the target site — a tumour, for example — TriMag can be activated to generate localised heat using its magnetic nanoparticles. This targeted heating destroys cancer cells through a process called hyperthermia, without damaging the surrounding healthy tissue. Only the tumour is heated. Only the tumour is destroyed.
**Inspired by Sperm**
The mechanical design of TriMag is, appropriately, borrowed from nature. 'The structure of the microrobots is inspired by nature and mimics sperm cells in both their shape and movement,' said lead researcher Professor Jinxing Li of MSU's College of Engineering. The sperm cell is one of evolution's most efficient small-scale propulsion systems — agile, directionally responsive, capable of navigating complex biological environments. TriMag's shape draws on that same blueprint.
The fabrication technique is equally refined: **two-photon lithography**, a form of ultra-high-precision 3D printing that operates at the nanometre scale, producing biocompatible hydrogel structures with features invisible to the naked eye.
**And Then They Disappear**
Perhaps the most elegant aspect of TriMag is what happens after its work is done.
The microrobots are fully biodegradable. Once their task is complete — tumour destroyed, drug delivered, imaging done — the microrobot's components break down naturally through the body's own biological processes. The breakdown products are cleared through the blood and kidneys, leaving no residue, no implant, no retrieval surgery required.
A device that navigates deep inside the body, kills cancer cells, and then simply stops existing.
**Where Things Stand**
TriMag has been demonstrated in early preclinical studies, including controlled navigation in porcine brain phantom tissue and in vivo gastric navigation in mice. The research findings were published in *Advanced Materials*, one of the leading materials science journals.
Professor Li's team collaborated with researchers from Henry Ford Health and Arizona State University. He emphasises that the versatility of the TriMag design — its ability to be adapted for different therapeutic applications — is the core of its promise: 'Because the TriMag design is so versatile, it opens the door to treatments that were not possible before.'
Specific targets being explored include: targeted drug delivery to tumours; improved treatment of eye diseases currently requiring injections; and less invasive approaches to brain surgery that reduce the need for large incisions and their associated recovery times.
**Access as a Goal**
Li also notes an equity dimension to the work. Technologies like TriMag, which reduce the need for highly specialised surgical infrastructure and expert operators, could make precision treatment accessible in contexts where specialist surgeons are scarce. The same microrobot that guides a treatment in a major university hospital could, in principle, do the same work in a district hospital on the other side of the world.
Medical technology has a history of starting in elite research centres and gradually becoming universal. The question with microrobots has always been whether the science was robust enough to survive that journey. TriMag, its creators believe, is. 🔬
*Sources: Michigan State University (March 2026) · Advanced Materials (Wiley Online Library) · Henry Ford Health · Arizona State University*
