Each individual Kilobot doesn't look like much: just a few centimetres in diameter, on three almost comical matchstick-like legs. Powered only by a pair of coin batteries, they move by vibrating, shuffling forward on those funny sticks.
The impressive part is what they can do together. In a swarm 1,024 robots strong, they can organise themselves into two-dimensional shapes, requiring only the initial information input -- the shape they are to form -- via infrared light.
The Kilobots -- the work of Harvard School of Engineering and Applied Sciences computer science professor Radhika Nagpal and her team -- are based on the behaviours of biological swarms, and are designed to demonstrate that simple robots are capable of enacting complex behaviours en masse.
"The beauty of biological systems is that they are elegantly simple -- and yet, in large numbers, accomplish the seemingly impossible," Nagpal said. "At some level, you no longer even see the individuals; you just see the collective as an entity to itself."
Licenced for manufacture by a partner in 2011, the robots have demonstrated themselves capable of forming two-dimensional shapes: a sea-star, the letter K (for Kilobots), a wrench -- much like marching bands or a flock of birds. Lead author Michael Rubinstein of Harvard SEAS and the Wyss Institute likened their behaviour to ants that link together to form bridges and rafts for difficult terrain, or social amoebas that link together that can form a single body that can escape an environment where food is scarce.
"Biological collectives involve enormous numbers of cooperating entities -- whether you think of cells or insects or animals -- that together accomplish a single task that is a magnitude beyond the scale of any individual," he said.
The way the Kilobots work is sheer genius in its simplicity. An initial set of instructions is beamed to the robots via infrared, after which they work autonomously, requiring no further human intervention. Four robots mark out the origin of a coordinate system; the remaining robots receive a 2D image.
They then assemble into that shape. Each Kilobot is fitted with infrared transmitters so that it can communicate with its neighbours, but they have no sense of their broader environment; they only know where their neighbours are and their point of origin, but are able to assemble into a shape by gauging the location of the other Kilobots.
"These robots are much simpler than many conventional robots, and as a result, their abilities are more variable and less reliable," Rubinstein explained. "For example, the Kilobots have trouble moving in a straight line, and the accuracy of distance sensing can vary from robot to robot." However, the strength of the swarm generally overcomes individual weaknesses.
This is the first robot swarm on this scale. Few swarms, in fact, exceed 100 individual robots, due to the cost and labour involved in creating the devices, and the algorithmic limitations on coordinating large numbers. The Kilobots will be invaluable as a test bed for such algorithms.
The potential of autonomous swarm robots is huge, particularly in fields such as construction, agriculture, medicine, and mining.
The robot hardware and software are available open-source for non-commercial use. You can find all relevant documentation available for free on the Kilobots website. You can also read the full study in the August 15 issue of the journal Science.