ARGONNE, Illinois — In the basement of a nondescript building here at Argonne National Laboratory, nickel particles in a beaker are building themselves into magnetic snakes that may one day give clues about how life originally organized itself.

These chains of metal particles look so much like real, living animals, it is hard not to think of them as alive. (See exclusive video below.) But they are actually bits of metal that came together under the influence of a specially tuned magnetic field.

“It behaves like some live object,” says physicist Alex Snezhko. “It moves. It crashes onto free-floating particles and absorbs them.”

Based on the huge reader reaction, Drs. Snezhko and Aronson put together a special supplementary letter for Wired readers with deeper explanations of the effects described in this article.

On the spectrum of scientific endeavor, this is very far upstream in the realm where people are just trying to figure how stuff works and why. There is some talk of applications, but at the heart of it, this is really just pure research. Snezhko and fellow physicist Igor Aronson — both tall, thin men who have matching Russian accents and familial rapport — have discovered something really cool, and they’re trying to simply figure out what’s behind it. Along the way, they could learn something fundamental about how the world works.

Looking at how their particles self-organize, the scientists see echoes of herds of sheep and schools of fish. It seems that there might be some common rules that underpin the behavior and movement of groups of things, but it’s not clear what those rules are. It took a couple of years of exhaustive research to figure out how the systems emerge, some of which will be published next week in Physical Review Letters.

Perhaps, by studying this simple system, they can understand what Aronson calls “the fundamentals of self assembly, how nature can organize itself into ordered states.” The idea is that if they can determine how magnetic fields and water tension can excite these particles into complex emergent behavior, they will get closer to understanding more complicated, messier systems — like the primordial soup from which life arose on Earth.

“We still don’t know what physics is appropriate for biology. This is a wonderful intermediate,” Iain Couzin, who heads Princeton’s Collective Animal Behaviour Laboratory told Wired.com in a phone interview. “There’s nothing biological about the interactions between the surface swimmers, but their collective dynamics can give us insight into how we can begin to study real biological systems.”

Back at Argonne, this is physics for the fun of physics. Though Snezhko tried hard to kill the snakes when they first started forming during an unrelated experiment, they soon became more interesting than the experiment they were ruining. Now he and

Aronson can’t stop smiling as they talk about discovering something so unexpected. The system exhibits new, dynamic behavior every time they turn it on. It’s mesmerizing.

The exciting science stands in stark contrast to the drab appearance of the Argonne campus. The low-slung, plain buildings look more like a middle school — complete with linoleum floors and fluorescent lighting — than a prestigious national lab doing world-class research.

But inside his basement lab, Snezhko shows us a captivating video of what looks almost like a line drawing of a small man — one larger “head” particle trailed by a “body” of skinny chains of particles — swimming around a beaker.

As it starts heading for other chains of particles in an unpredictable and eccentric way, it’s nearly impossible not to anthropomorphize the structure. It just acts too much like life. The damn thing practically has … personality.

“It also has a very bad temper,” Aronson jokes, noting that this creature, this figment of nature, appears to “hunt” the other particles. Indeed it does. As you can see in the video, the metallic monster, technically known as a “surface swimmer,” acts hungry. As it snatches more particles, it swims faster and faster.

The experimental setup is simple: just a liquid-filled beaker surrounded by a magnet. That magnet is hooked up to alternating current, which creates a magnetic field that can flip direction very quickly. Most of the time, when the scientists sprinkle particles into the liquid and turn on the current, nothing really interesting happens. Maybe the particles link together in static strings.

But when the magnetic field is tuned just right, something strange happens. The particles snap into chains that just start swimming around.

“We call this structure Snake,” Snezhko says, pointing to one of the simple structures, and indeed, it looks like that game you used to play on your pre-iPhone Nokia. (You can see a slew of other clips of the snakes at Wired Video.)

The snakes’ motion, Snezhko says, is a kind of “resonance.” As the magnetic field flips back and forth, the particles’ movement changes the surface of the water, which changes how the particles move, which changes the surface of the water, and so on.

The simulation they’ve developed, in the video below, helps show how the process starts.

By slightly changing the parameters — the frequency of the current, or the mixture of particle sizes — they can generate different types of systems. Besides the hunter, they’ve generated single- and multiple-snake systems, chains that stay still but pump water, and others that just shimmy in place.

“You have a deliberately nonbiological system, but it’s behaving a bit like a biological system,” says Iain Couzin, who heads Princeton’s Collective Animal Behaviour Laboratory. “I just like the way that it spans across biology and physics in quite a beautiful way.”

And the research may one day have practical applications. Some day, the swimmers may be used to help scrub the surfaces of materials — or maybe they’ll hook up one of the snakes to a cell and drag it around. Wai Kwok, the head of the superconductivity and magnetism group at Argonne, calls attaching magnetic particles to living cells “feasible.”

“If you can do that, you can control an actual living organism,” Kwok says.

At the very least, the work could help biologists understand how tiny microorganisms propel themselves. Aronson runs another Argonne lab that tries to apply some of the snake work to single-celled organism locomotion.

Going to an even small smaller scale, self-assembled, self-propelled nanoscale swimmers could clean surfaces or deliver medications, but the scientists agree that there would be serious engineering challenges at that scale.

And in any case, standing next to his self-assembling snakes in a beaker, Snezhko has a response for reporters asking typical questions about applications. He points to a sign that’s taped over his bench. It’s a famous quote from Richard Feynman: “Physics is like sex. Sure, it may give some practical results, but that’s not why we do it.”

10:12 AM: Updated to link Physical Review Letters and clarify Kwok’s position at Argonne.

See Also:

Image: Betsy Mason/Wired.com.

Videos: Alex Snezhko and Igor Aronson/Argonne National Laboratory.

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