Small robots that have two flapping arms and can鈥檛 move around on their own can spontaneously link up and glide together instead. This self-organisation may be related to how complex structures arise from simple building blocks in nature.
at the Georgia Institute of Technology in Atlanta and his colleagues used small robots called smarticles 鈥� short for 鈥渟mart active particles鈥� 鈥� to observe self-organisation in the lab.
Each smarticle consisted of three 5-centimetre-long bars attached at right angles, resembling a large staple. The two end bars served as 鈥渨ings鈥�, flapping through a range of pre-programmed motions when turned on. When tipped on its side, a single smarticle can jiggle in place but not move horizontally.
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The researchers first arranged seven smarticles in a pile tight enough for some of them to touch on top of an aluminium plate. They wanted to see whether the smarticles would self-organise once they were turned on 鈥� similar to how groups of fire ants can arrange themselves into rafts 鈥� or simply push each other away.
Once turned on, the smarticles started to interlock and form chain-like structures called 鈥済liders鈥� that could move about the plate. Gliders stayed bound together for minutes at a time and moved a distance of around three times the length of a single smarticle.
Through repeated experiments and computer simulations of larger groups of smarticles, the researchers found that gliders continued to form even when they changed the angle through which smarticle wings moved. They also found that different glider shapes emerged. In one case, smarticles were oriented back-to-back while in another the arms of one smarticle poked out towards the arms of another.
Goldman says that smarticles can pair up because they essentially change their shape every time they move their arms. However, he says, while physicists may be good at predicting how two balls will bounce off each other in a collision, developing a precise mathematical model for two objects that 鈥渨ant to be doing something鈥� like jiggling or flapping on their own is very challenging.
Though studying smarticle glider formation is a theoretical challenge, similar phenomena abound in nature, says Goldman. Patterns like smarticle gliders also emerge in the computer simulation known as the Game of Life where a player inputs a pattern onto a grid then watches it become more complex by following a set of simple rules.
鈥淭hese emergent features, the kind of self-organising into structures, appear to be common across systems,鈥� he says. He and his colleagues want to use their tiny robots, which are relatively simple to observe, to learn more about these commonalities and possibly to design sets of robots that could form functional, useful shapes after being poured out on a surface.
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