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Liquid undergoes magnetic ‘splits’

The demonstration helps scientists begin how molecules in plants and animals naturally alter their shapes

4:42pm, July 29, 2013

On their own, proteins and other molecules in nature can warp and fold into new shapes. Scientists want to create synthetic structures that can alter their form much as the molecules in plants and animals do. A team in Europe has now tested a simple shape-shifting material.

A liquid mixed with nanomagnets can split and arrange itself into simple droplets (left) and complex, warping formations (right). All it takes to do this is the presence of a magnetic field. Credit: Courtesy of Mika Latikka and Jaakko Timonen/Aalto Univ.

Physicist Jaakko Timonen at Aalto University in Finland and his colleagues worked with liquids into which they suspended nanomagnets. Each only a few billionths of a meter in diameter, these particles can force the liquid to behave in strange ways when exposed to magnetic fields.

The researchers first placed a droplet of this “ferrofluid” atop a nonstick surface. Then they gradually moved a large magnet toward the surface from below. This increased the magnetic field exerted on the fluid. The droplet responded by splitting into one or more simple, evenly spaced daughter droplets. Timonen’s team reported its new findings July 19 in Science.

Timonen and his team also dragged the lower magnet back and forth below the surface, moving it increasingly faster and over longer distances. Videos show that under certain of these conditions, separate droplets suddenly joined together. This created elongated globs. And their shape changed as the magnet yanked them back and forth.

A dollop of a ferrofluid divides into daughter droplets (and several very small pellets). This shape-shifting occurs when the droplets are exposed to a magnetic field.
Credit: Courtesy of Science/AAAS

Timonen says the demonstration should help scientists better understand how natural shape shifters do their thing. It might also offer clues to the design of synthetic materials that will morph on demand.

Power Words

ferrofluid (also magnetic fluid) A liquid that responds to a magnetic field because magnetic particles have been mixed into it. The prefix, ferro, means iron and refers to the fact that magnetic materials contain iron.

field A region in space where certain physical effects operate, such as magnetism (created by a magnetic field), gravity (by a gravitational field) or mass (by a Higgs field).

magnet A material that either attracts objects that contain iron or lines up in a magnetic field.

nano A prefix indicating a billionth. It’s often used as an abbreviation to refer to objects that are a billionth of a meter long or in diameter.

physicist A scientist who studies the nature and properties of matter and energy.

proteins Compounds made from one or more long chains of amino acids. Proteins are an essential part of all living organisms. They do the work inside a cell.

synthetic (as in materials) Materials created by people. Many have been developed to stand in for natural materials, such as synthetic rubber, synthetic diamond or a synthetic hormone. Some may even have the same chemical structure as the original.

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