A starfish embryo resembles a tiny bead, spinning through the water in its earliest stages.
According to MIT scientists, when multiple starfish embryos spin up to the water's surface, they gravitate to each other and form a crystal-like structure.
In this case, the spinning of individual units can cause ripples across the whole structure.
As individual embryos mature, the rippling crystal configuration can be dissolved.
The embryos look like glass beads, and they come to the surface to form a crystal structure. "Like a flock of birds that can avoid predators, or fly more smoothly because they can organize in these large structures, maybe this crystal structure could have some advantages we're not aware of yet."
She says that this self-assembling, rippling crystal assemblage could be used as a design principle in building robot that move and function together.
Fakhri says that it's possible to build a swarm of soft, spinning robot that can interact with each other. They could be designed to move through the sea in order to do useful work. The interactions allow for a new range of physics to be explored.
The results of the study have been published.
They're spinning together.
The team's observations of starfish crystals was a "serendipitous discovery" according to Fakhri. Her group is studying how starfish embryos develop and how embryonic cells divide.
One of the oldest model systems for studying developmental biology is the starfish.
The researchers were looking at how the embryo swims as it matures. After fertilization, the embryos grow and divide, forming a shell that propels an embryo through the water. Cilia coordinate to spin an embryo in a specific direction. Tzer Han Tan noticed that as the embryos swam towards each other, they continued to spin.
A group of people would come together and dance. There are other marine organisms that do that as well. This is intriguing to us. If you put a bunch of them together, what will happen?
She and her colleagues fertilized thousands of starfish embryos and watched them swim to the surface of shallow dishes.
Thousands of embryos in a dish form a crystal structure that can grow very large. It's called a crystal because each embryo is surrounded by six neighboring embryos in a hexagonal pattern that is very similar to the crystal structure in Graphene.
There areggling crystals.
The team first looked at a single embryo's flow field, or the way in which water flows around the embryo. They placed a single starfish embryo in the water and took pictures of the beads as they flowed around the embryo at the water's surface.
The researchers were able to see the flow of the beads around the embryo. They found that the cilia on the embryo's surface beat in such a way that they spun the embryo in a certain direction and created whirlpools on either side of the embryo.
The flow field from a single embryo to a simulation of many embryos was worked on by Mietke, a PhD student in Dunkel's applied mathematics group at MIT. The crystal structures produced by the model were the same as those observed in the experiments.
The team observed that once a crystal structure had formed, it persisted for days, and during this time there were ripples across the crystal.
She says that they could see the crystal rotating and moving. You would expect these ripples to die out quickly because of the water's effect. The system has some strange behavior.
The ripples may be the result of interactions between the individual embryos which spin against each other. Many individual spins could set off a larger, collective motion across the entire structure.
The researchers are trying to figure out if other organisms have the same behavior. They are interested in replicating this structure in robotic systems.
She says that you can build something like a robotic swarm that can work on the environment.
More information: Nikta Fakhri, Odd dynamics of living chiral crystals, Nature (2022). DOI: 10.1038/s41586-022-04889-6. www.nature.com/articles/s41586-022-04889-6 Journal information: NatureMIT News ( web.mit.edu/newsoffice/) is a popular site that covers news about MIT.
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