While bees, birds, and ants swarm together to mate or protect against predators, these worms are able to braid together to accomplish tasks that unconnected individuals cannot handle. They live at the bottom of freshwater ponds, feeding on bacteria and other microorganisms. During periods of sustained drought, when pond water is low, spotting is a kind of collective decision-making that allows the worms to survive longer without drying out. The worm sphere is able to conserve water, as it exposes less surface area to the air than worms would if left alone. Some of these balls can reach 100,000 worms.
In fact, Bhamla says he first encountered the worms while walking near a dry pond on the Stanford University campus in 2017 as a graduate student. He was curious what kind of life could return to a drought-stricken lake. “It had just rained and I was excited because California had a lot of drought,” Bhamla recalls. “I was curious about this pond – when it’s been dry for so long, what happens when the water comes in? What kind of life could emerge? “
Bhamla returned to the pond with a bottle of water and an eyedropper to collect rejuvenated worms which were beginning to form small tangles of life. After earning a PhD in molecular engineering from Stanford, Bhamla joined Georgia Tech and has been conducting worm spot experiments ever since.
By studying these worms in the lab, the Georgia Tech team were also able to construct simple mechanical analogues of the worm drops. Using the behavior of the worm as a model, Ozkan-Aydin designed six 3D printed robots, each about 3 to 4 inches long. (Unlike actual worms, each device had two arms and two light sensors.) Then they could be programmed to perform various movements and observed as they became entangled with each other.
Hoping to better understand how to develop future robotic swarms with better energy efficiency, the experimenters measured the energy used by each individual robot. The team determined that the robots used less energy while wiggling than crawling. Georgia Tech researchers this month published the results of their experiments with worm blobs and their robotic counterparts in the journal Proceedings of the National Academy of Sciences.
That kind of work could one day lead to programmable active matter, says Daniel Goldman, professor of physics at Georgia Tech. The active material is a hypothetical material that changes shape just like worm drops – in which tiny particles of material organize themselves in response to a stimulus or program. Imagine that self-wrapping paper, for example, or a liquid metal tool that could reshape itself depending on the type of work you need to do. “These robot models can act as theoretical and computational models to test biological hypotheses,” Goldman explains. “Once you get the robot’s physical system up and running, it can inspire engineers to create better-designed devices.”