How small is the smallest robot worth worrying about?

Set aside the massive drones and surveillance platforms, the autonomy-enable aerostats and mostly on autopilot aircraft. Think even smaller than the ground robots and quadcopters that fill shelves in stores. If we want to look at the future of miniature machines, we need to narrow our focus, down to a few centimeters.

Like these little mindless machines, vibrating bundles of legs and wires and batteries.

These roach-like robots self-separate into two populations: one on the edge of the corral, one on in the middle. Individuals move between the populations. Credit: A. Deblais et al., Phys. Rev. Lett. (2018)
These roach-like robots self-separate into two populations: one on the edge of the corral, one on in the middle. Individuals move between the populations. Credit: A. Deblais et al., Phys. Rev. Lett. (2018)


What’s happening here? From Phys.org:

The robots were tiny, battery-powered and rod-shaped bits of colored plastic, each approximately four centimeters in length. They were actually toys that look like beads with tiny legs on the bottom. Placed on a surface, they vibrate, which propels them forward at approximately 30 centimeters per second. Putting a bunch of them into a confined ring, the researchers found, resulted in what looked oddly similar to gas molecules in a confined space. The robots zig-zagged around the ring with random abandon. But when they added more of the robots to the ring, they found that the robots started to form two groups at the edges of the corral. They noted also that the membership of the groups constantly changed as the tiny robots careened about.

Robots moving to the edges of a container is neat but lacking in practical applications. So to see what this sorting effect could do, the researchers then put the robots in a flexible corral. Now, the robots, behaving just as they were before, could move the corral through obstacles, like this.

These roach-like robots manage to, through nothing more than vibrating against the edge of their corral, move through a narrow gap. Credit: A. Deblais et al., Phys. Rev. Lett. (2018)
These roach-like robots manage to, through nothing more than vibrating against the edge of their corral, move through a narrow gap. Credit: A. Deblais et al., Phys. Rev. Lett. (2018)


These robots give researchers a way to study how insects and microbes execute complex movements, and the principles studied may influence future design of even tinier robots designed to work inside biological systems (read: bodies). That’s interesting enough, but for our purposes, this is also a way to look at the kinds of emergent behavior in a swarm done without any communication or control.

Like so many fingers on a Ouija board, these robots navigate an obstacle course in a way that looks supernaturally directed, yet it as most the cumulative effort of many undirected nudges. As the Pentagon further explores autonomous technologies, and ways to maneuver in communications-denied environments, robots like this are collectively navigating one path forward. And doing it all without anything resembling so much as a sensor or a brain.