Computer graphic of a micro-vehicle with iron wheels (gold) and a polymer chassis (red). The vehicle measures just 0.25 millimeters long. (Image: Alcântara et al. Nature Communications 2020)

Researchers have been pursuing the development of robots so tiny that they can maneuver through blood vessels and deliver medications to certain points in the body. Now, scientists have succeeded in building such micromachines out of metal and plastic in which these two materials are interlocked as closely as links in a chain. This is possible thanks to a new manufacturing technique they have devised.

As a rule, micromachines are powered from outside the body using magnetic fields, which means they must have magnetic metal parts installed. Polymers, in contrast, have the advantage that they can be used to construct soft, flexible components as well as parts that dissolve inside the body. If medication is embedded in this kind of soluble polymer, it is possible to selectively supply active substances to certain points in the body.

Underpinning the new manufacturing method is a high-precision 3D printing technique that produces complex objects on the micrometer level — a technique known as 3D lithography. The scientists applied this method to produce a kind of mold or template for the micromachines. These templates have narrow grooves that serve as a “negative” and can be filled with the chosen materials. Using electrochemical deposition, the scientists filled some of the grooves with metal and others with polymers before ultimately dissolving the template away with solvents.

The scientists created various miniscule vehicles with plastic chassis and magnetic metal wheels powered by means of a rotating magnetic field. Some of the vehicles can be propelled across a glass surface while others — depending on the polymer used — can float in liquid or on a liquid surface.

The scientists are planning to refine the two-component micromachines and experiment with other materials. In addition, they will attempt to create more complex shapes and machines including some that can fold and unfold themselves. Besides serving as “ferries” that distribute active substances, future applications of micromachines include treating aneurysms (bulges in blood vessels) or performing other surgical procedures. Another research goal is to make stents (tube-shaped vessel supports) that unfold themselves and can be positioned at a specific place in the body using magnetic fields.

For more information, contact Dr. Fabio Bergamin at This email address is being protected from spambots. You need JavaScript enabled to view it.; +41 44-632-5780.