But as small as the components get, installing new features and functions on the diminutive devices is not getting any easier. "Conventional micro-robots have lots of stuff on them," which often adds to their size, Pelrine says. That's why SRI researchers opted for a different design approach, one that off-loads most complexity and size from the mobile-robot equation.
The tiny robotic elements are electromagnetically levitated above the workspace and controlled with digital precision. "What we have is a simple set of magnets to which various tools and end-effectors can be attached," Pelrine explains. The bots, which feature multiple degrees of freedom, are manipulated using magnetic fields that are generated by electric circuits that lie beneath the workspace.
"All the complexity of the typical micro-robot system—the power, the sensors and most of the actuation—is off-board," he says. "That keeps things small, simple and low cost."
The fact that the floating bots suffer "zero wear" as they travel could be a key consideration if engineers were to build large systems with thousands of robotic elements, Pelrine adds.
Magnetic microbots could be downsized to operate in even smaller realms, Pelrine continues. Perhaps by using micro-fabricated magnet technology to build the bots themselves, researchers could at some point move manufacturing operations toward the micron size scale. He stresses, however, that such an advance "would no doubt require successive generations" of the downscaled microbots and control systems.
Such proposed activity would traverse the macro/micro-scale interface, wherein the bots could perform microscale functions and yet be able to move long distances—centimeters or even meters—to directly interact with the macro world as well. At that size level, for instance, a microbot could work on minute objects using a probe tip like those used in atomic force microscopes and then travel macroscopic distances to carry out other chores such as washing or calibrating the tip.
On the broader scale, the implications of automated systems with potentially millions of tiny, individually controlled agents could be profound. One might imagine swarms of microbots constructing novel, high-performance materials with microstructures that are engineered down to the grain-size scale, Pelrine says.
Even the self-replication of parts by microbots could be feasible, a concept that evokes concepts introduced by K. Eric Drexler in his 1986 book Engines of Creation: The Coming Era of Nanotechnology (Anchor). The SRI team has demonstrated, for example, that the microbots can build end-effectors for other microbots and assemble small robot bodies from magnets to form larger robot bodies.
"It's really a new class of machine," Pelrine concludes, "something that is perhaps hard to recognize at present."