Researchers develop a way to cause static self-assembly using magnets and ferrofluids

Jul 19, 2013 by Bob Yirka report

A team of researchers at Finland's Aalto University has discovered a way to cause droplets of ferrofluid (liquids with suspended magnetic nanoparticles in them) to self-assemble into complex shapes. In their paper published in the journal Science, the team describes how they discovered that placing and moving a magnet under a ferrofluid sitting on a hydrophobic (water resistant) surface caused the fluid to separate and self-assemble into complex patterns.

Scientists are eager to find ways to cause self-assembly of synthetic structures because it would allow for the creation of materials at a lower cost—by eliminating the manual steps required to construct them. Prior research has revealed that there are many instances of self-assembly in nature—self-warping proteins are one example—but thus far it's been difficult to find reproducible ways to cause self-assembly in the lab. In this new effort, the team in Finland set a single drop of ferrofluid onto a and then moved a magnet beneath it to cause changes in its shape.

The team first tested moving the magnet closer to the underside of the surface to see what impact it would have on the drop—it coalesced with portions of it rising up off the surface, creating a three dimensional, pointy drop. Moving the magnet closer caused the drop to spontaneously split apart into several smaller drops. Moving even closer caused the smaller drops to split, resulting in many small drops, all still pointing skyward. Next, the team tried moving the magnet back and forth. The oscillation caused some of the drops to merge and as they did so, to form into seemingly random shapes. Changing the rate caused the drops to form into different shapes. Removing the magnet caused each of the drops to return to a flattened state.

The researchers suggest their results might be useful going forward as a platform for discovering new ways to create self-assembled materials—by adding material to the drops that causes it to hold its shape after the magnet is removed. They also note that the their technique allows for separating a liquid very easily into several smaller drops—something that might prove very useful for such applications as running several tests on a single water sample at wastewater treatment plants.

Explore further: How the physics of champagne bubbles may help address the world's future energy needs

More information: Science, doi:10.1126/science.1233775

add to favorites email to friend print save as pdf

Related Stories

High speed camera study shows why boiling drops take off

Jul 26, 2012

(Phys.org) -- Everyone knows what happens if you drop water onto a hot pan, it separates into flat bottomed bubbles that appear to float above the bottom of the pan then move around of their own accord until ...

Why do dew drops do what they do on leaves?

Jan 11, 2012

Nobel laureate poet Rabindranath Tagore once wrote, "Let your life lightly dance on the edges of time like dew on the tip of a leaf." Now, a new study is finally offering an explanation for why small dew drops ...

Stirred, not shaken: Nanoscale magnetic stir bars

Jul 10, 2013

Anyone who has ever worked in a laboratory has seen them: magnetic stirrers that rotate magnetic stir bars in liquids to mix them. The stir bars come in many different forms—now including nanometer-sized. ...

Surfing on acoustic waves (w/ Video)

Jul 16, 2013

(Phys.org) —ETH researchers are able to make objects such as particles and liquid droplets fly in mid-air by letting them ride on acoustic waves. For the first time, they have been able to also control ...

Recommended for you

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.