Pinwheel ‘living’ crystals and the origin of life

Date:

Share post:

Simply making nanoparticles spin coaxes them to arrange themselves into what University of Michigan researchers call ‘living rotating crystals’ that could serve as a nanopump. They may also, incidentally, shed light on the origin of life itself.

Pinwheel 'living' crystals and the origin of life
U-M researchers have found in a simulation that simply inducing nanoparticles to spin causes them to self assemble into ‘living rotating crystals.’ The size and direction of the arrows indicate the movements of the particles, while the yellow and blue colors represent clockwise and counterclockwise spinners, respectively. The arrows arranged in orderly grids are particles that have formed rotating crystals, while the large, aligned arrows at the boundaries show how particles are driven along the interfaces [Credit Sharon Glotzer]

The researchers refer to the crystals as ‘living’ because they, in a sense, take on a life of their own from very simple rules.

Sharon Glotzer, the Stuart W. Churchill Collegiate Professor of Chemical Engineering, and her team found that when they spun individual nanoparticles in a simulation — some clockwise and some counterclockwise — the particles self-assembled into an intricate architecture.

The team discovered the behavior while investigating methods to make particles self-assemble — one of the major challenges in nanotechnology — without complicated procedures. When the pieces are a thousand times smaller than a grain of sand, normal techniques for building structures are no longer effective.

For this reason, researchers like Glotzer are exploring ways to make order develop naturally from disorder, much like what may have occurred at the very beginnings of life.

“If we can understand that, not only can we begin to imagine new ways to make materials and devices, but also we may begin to understand how the first living structures emerged from a soup of chemicals,” said Glotzer, who is also a professor of materials science and engineering, macromolecular science and engineering, physics, and applied physics.

“One way biology approaches the challenge of assembly is by constantly feeding building blocks with energy. So, that’s what we did with nanoparticles.”

Recently, researchers in the field have found that if particles are given energy for some basic motion, such as moving in one direction, they can begin to influence one another, forming groups. Glotzer’s team looked at what would happen if the particles all were made to rotate.

“They organize themselves,” said Daphne Klotsa, a research fellow in Glotzer’s lab. “They developed collective dynamics that we couldn’t have foreseen.”

The team’s computer simulation can be imagined as two sets of pinwheels on an air hockey table. The air pushing up from the table drives some of the pinwheels clockwise, and others counterclockwise. When the pinwheels are tightly packed enough that their blades catch on one another, the team found that they begin to divide themselves into clockwise and counter-clockwise spinners — a self-organizing behavior known among researchers as phase separation.

“The important finding here is that we get phase separation without real attraction,” Klotsa said.

She calls the self-sorting counterintuitive because no direct forces push the same — spin pinwheels together or push opposite-spinners apart.

The separation occurs because of the way the pinwheel blades collide. While a pair of pinwheels may be spinning in the same direction, where their blades might meet, they’re actually moving in opposite directions. This means that the blades will push into one another and stick together, causing the pair of pinwheels to rotate as one, at least briefly.

In contrast, the blades of opposite spinners are moving in the same direction where they meet, so they don’t stick together. Since same-spinning pinwheels spend more time linked up, they gradually accumulate into groups.

When the pinwheels divide into clockwise and counterclockwise tribes, the boundary between the groups becomes a thoroughfare for particles in the mix that aren’t spinning. The blades at the boundary push these nonspinning particles along the border, making them less likely to dive back into the denser collections of pinwheels. The team said this phenomenon could potentially be harnessed as a sort of nanopump to transport objects in a device.

While the computer simulations were in two dimensions, as though on a flat surface, the team anticipates that rotating particles could also grow into ‘living,’ three-dimensional crystals. The particles would be free to turn their spin axes in any direction, so they could eventually form a 3D liquid crystal with aligned axes.

The results appeared online in this week’s issue of Physical Review Letters and will be presented at a March 6 meeting of the American Physical Society. This work was funded by the U.S. Department of Energy.

Source: University of Michigan [February 24, 2014]

ADVERTISEMENT

spot_img

Related articles

Multicellularity, a key event in the evolution of life

Multicellularity in cyanobacteria originated before 2.4 billion years ago and is associated with the accumulation of atmospheric oxygen,...

Buddha carving partially destroyed by militants restored in Pakistan

A Buddha carved on a rock in the Swat district of Pakistan's northwest has been restored after militants...

Measuring the shape of the Milky Way’s black hole

At the heart of our galaxy's center is SagA*, a supermassive black hole containing about four million solar-masses...

Hubble watching ancient orbs of globular cluster M 4

A sparkling picture taken by the NASA/ESA Hubble Space Telescope shows the center of globular cluster M 4....

Northern Song Dynasty mural tomb found in Shanxi

An ancient brick tomb painted with colored murals from Northern Song Dynasty (960-1127) was discovered in Shanxi when...

Complex life left oceans earlier than thought

A team of scientists from the University of Sheffield, the University of Oxford and Boston College, who are...

Galactic Archaeology group produce first age map of Milky Way halo

University of Notre Dame astronomer Timothy Beers and his Galactic Archaeology group, which includes Notre Dame astronomers Daniela...

Isle of Skye fossil makes three species one

The discovery of a tiny, 170-million-year-old fossil on the Isle of Skye, off the north-west coast of the...