To address the issue, the Purdue team developed a system of magnetic fields generated by an array of tiny planar coils in the robots' "workspace." The coils produce localized magnetic fields that can be used to guide the robots individually, as opposed to a global filed that would move the ‘bots as a group.
What's more, the magnetic fields actually power the robots as well. The radically miniaturized machines are too small for batteries, so onboard power isn't an option at this scale. The microbot models used in the study are magnetic disks about 2 mm in diameter - about twice the size of a pinhead. But the team says the technology will work with machines as small as 250 microns, or 0.25 mm in diameter.
Robot Assembles Itself, Crawls Away
The technology could have practical applications in manufacturing and medicine. For example, microbots equipped with probe-like "force sensors" could be used in biopsies, crawling around the bottom of a petri dish to detect cancer cells.
Findings are detailed in a research paper published this month in the journal Micromachines. Here's a video of the li'l fellers in action.