Koohee Han, Dr. Wyatt Shields, Prof. Orlin D. Velev, NC State University.
It might look like a clip from a retro computer game, but this is in fact real footage of a magnetic microbot capturing a live cell. Scientists at North Carolina State University, USA, designed these tiny cobalt-coated polymer cubes, which can assemble themselves into diverse patterns and configurations when exposed to magnetic fields, mimicking how particles accumulate in nature.
Controlled, unified clustering is desirable in developing biomedical applications that require fine, localised movement of autonomous robots, and could have applications in cell-level diagnosis, drug delivery, biological probing and microsurgery. The development of assemblies that can orient directionally by responding to other particles or the surrounding environment remains a major challenge.
Koohee Han and colleagues created ten-micrometre polymer cubes, each coated on one face with a thin magnetic film of cobalt. They demonstrated that the transparent cubes formed various configurations when submerged in solution and repeatedly subjected to uniform or superimposed magnetic fields.
In one orientation, the multi-cube structure acted as a ‘micro-tweezer’ and was able to capture and transport a live yeast cell. And because of magnetic energy storage in the cobalt layer, cube-to-cube interactions could occur remotely, even in the absence of a magnetic field, which prevented total disassembly.
The authors say their method can be applied to more complex particle shapes to address a range of applications, from robotics and micromanipulation to responsive materials.