Research Highlights

doi:10.1038/nindia.2014.133 Published online 30 September 2014

Flocking behaviour of the non-living

The brass rods align spontaneously on a vibrating surface amidst a background of aluminium beads.

© Kumar, N. et al
Non-living things can also organise themselves and move in a group if rendered motile, just like formations of flying birds, according to new research on small metal beads and rods1. The insight might lead to possible new method for cellular matter transportation in the human body.

Researchers at the Indian Institute of Science (IISc), Bangalore and TIFR Center for Interdisciplinary Sciences, Hyderabad dispersed millimetre-sized tapered brass rods among spherical aluminium beads on a gently vibrating surface. They were interested in studying the collective behaviour of such moving rods. They found that the motile rods dragged the beads along, and neighbouring rods reoriented themselves to move in a circle.

The researchers call this phenomenon a ‘flocking transition’ where the rods go into a state of spontaneous alignment.“We were expecting the rods to show cooperative behaviour as seen in living objects”, says Ajay Sood, one of the authors.The study shows that particles far apart can influence self-organisation as opposed to the conventional thinking that they just follow their nearest neighbours. 

The researchers claim that their work demonstrates for the first time the ‘formation of a true flock in a collection of dry grains’. The discovery that a small concentration of motile particles can transport a large non-motile cargo might have wide applications in biological systems as well as industry, they say.


References

1. Kumar, N. et al. Flocking at a distance in active granular matter. Nat. Comm. (2014) doi: 10.1038/ncomms5688