New structures self-assemble in synchronized dance

November 21, 2012

CHAMPAIGN, Ill. -- With self-assembly guiding the steps and synchronization providing the rhythm, a new class of materials forms dynamic, moving structures in an intricate dance.

Researchers from the University of Illinois and Northwestern University have demonstrated tiny spheres that synchronize their movements as they self-assemble into a spinning microtube. Such in-motion structures, a blending of mathematics and materials science, could open a new class of technologies with applications in medicine, chemistry and engineering. The results will be published in the Nov. 22 edition of the journal Nature.

"The world's concept of self-assembly has been to think of static structures - something you would see in a still image," said Steve Granick, Founder Professor of Engineering at the U. of I. and a co-leader of the study. "We want shape-shifting structures. Structures where a photograph doesn't tell you what matters. It's like the difference between a photograph and a movie."

The researchers used tiny particles called Janus spheres, named after the Roman god with two faces, which Granick's group developed and previously demonstrated for self-assembly of static structures. In this study, one half of each sphere is coated with a magnetic metal. When dispersed in solution and exposed to a rotating magnetic field, each sphere spins in a gyroscopic motion. They spin at the same frequency but all face a different direction, like a group of dancers in a ballroom dancing to the same beat but performing their own steps.

As two particles approach one another, they synchronize their motions and begin spinning around a shared center, facing opposite directions, similar to the way a couple dancing together falls in step looking at one another.

"They are both magnetized, which causes them to attract each other, but because they're moving, they have to move in sync," said Erik Luijten, a professor of materials science and engineering and of applied mathematics at Northwestern University who co-led the research with Granick.

Soon, the pairs and clusters of dancing spheres assemble themselves into a microtube - a long, hollow structure. The entire tube spins, even as each individual sphere continues its motion as well, like dancers in a line dance completing their individual steps as the line moves.

See a video at www.youtube.com/watch?v=MpzPflueLwc

"It's spontaneous. We don't force it to form," said U. of I. graduate student Jing Yan, the first author of the paper. "We saw that during the self-assembly process, the synchronization also happens. If you look at the spheres, every one is doing a different thing. Only when they come in close contact will they do something cooperatively. The two concepts are intricately related in this system."

Now that the researchers have detailed the delicate choreography of synchronization and self-assembly, they hope to explore applications for this new class of moving structures. One potential application of a dynamic, self-assembled microtube is to transport and release cargo. A particle or collection of molecules could be encapsulated in the tube and transported to a different location. Then, the tube can be disintegrated, releasing the cargo at a target point.

"We're looking for the new applications that people haven't dreamt up yet because they didn't have the capability," said Granick, a professor of materials science and engineering.

Next, the researchers are working to further understand the properties governing synchronized self-assembly and ways to guide it for functionality, such as manipulating the structures with an electrical or magnetic field. They also plan to explore directing the Janus spheres to synchronized self-assembly of other shapes and structures, allowing even more applications.

"Traditionally in self-assembly, you make a specific building block that will organize into a specific structure," Luijten said. "If you want a different structure you have to make a different building block. Here now, with one building block, we can control the structure by exploiting the synchronization effect."
-end-
The U.S. Army Research Office, the Department of Energy and the National Science Foundation supported this work. U. of I. research scientist Sung Chul Bae and Northwestern University graduate student Moses Bloom were co-authors of the paper. Granick also is affiliated with the Frederick Seitz Materials Research Laboratory and with the departments of chemistry, physics, biophysics, and chemical and biomolecular engineering at Illinois. Luijten also is associated with the department of engineering sciences and applied mathematics at the McCormick School of Engineering at Northwestern University.

END EMBARGO FOR RELEASE UNTIL NOON CST NOV. 21 (WEDNESDAY)

Editor's notes: To reach Steve Granick, call 217-333-5720; email: sgranick@illinois.edu. To reach Erik Luijten, call 847-491-4097; email: luijten@northwestern.edu.

Additional press contact: Megan Fellman, Science and Engineering editor, Northwestern University, (847) 491-3115, fellman@northwestern.edu.

The paper, "Linking synchronization to self-assembly using magnetic Janus particles," is available from the News Bureau.

University of Illinois at Urbana-Champaign

Related Magnetic Field Articles from Brightsurf:

Investigating optical activity under an external magnetic field
A new study published in EPJ B by Chengping Yin, Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, South China, aims to derive an analytical model of optical activity in black phosphorous under an external magnetic field.

Magnetic field and hydrogels could be used to grow new cartilage
Instead of using synthetic materials, Penn Medicine study shows magnets could be used to arrange cells to grow new tissues

Magnetic field with the edge!
This study overturns a dominant six-decade old notion that the giant magnetic field in a high intensity laser produced plasma evolves from the nanometre scale.

Global magnetic field of the solar corona measured for the first time
An international team led by Professor Tian Hui from Peking University has recently measured the global magnetic field of the solar corona for the first time.

Magnetic field of a spiral galaxy
A new image from the VLA dramatically reveals the extended magnetic field of a spiral galaxy seen edge-on from Earth.

How does Earth sustain its magnetic field?
Life as we know it could not exist without Earth's magnetic field and its ability to deflect dangerous ionizing particles.

Scholes finds novel magnetic field effect in diamagnetic molecules
The Princeton University Department of Chemistry publishes research this week proving that an applied magnetic field will interact with the electronic structure of weakly magnetic, or diamagnetic, molecules to induce a magnetic-field effect that, to their knowledge, has never before been documented.

Origins of Earth's magnetic field remain a mystery
The existence of a magnetic field beyond 3.5 billion years ago is still up for debate.

New research provides evidence of strong early magnetic field around Earth
New research from the University of Rochester provides evidence that the magnetic field that first formed around Earth was even stronger than scientists previously believed.

Massive photons in an artificial magnetic field
An international research collaboration from Poland, the UK and Russia has created a two-dimensional system -- a thin optical cavity filled with liquid crystal -- in which they trapped photons.

Read More: Magnetic Field News and Magnetic Field Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.