Self-organizing smart materials that mimic swarm behavior

July 22, 2016, Ulsan National Institute of Science and Technology
Janus colloids with equal-and-opposite charges attract one another into connected, dynamic chains. Copyright : UNIST

A new study by an international team of researchers, affiliated with Ulsan National Institute of Science and Technology (UNIST), Korea, has announced that they have succeeded in demonstarting control over the interactions occurring among microscopic spheres, which cause them to self-propel into swarms, chains, and clusters.

The research published in the current online edition of Nature Materials takes lessons from cooperation in nature, including that observed in honey bee swarms and bacterial clusters. In the study, the team has successfully demonstrated the self-organizing pattern formation in active materials at microscale by modifying only one parameter.

This breakthrough comes from a research, conducted by Dr. Steve Granick (School of Natural Science, UNIST) of IBS Center for Soft and Living Matter in collaboration with Dr. Erik Luijten from Northwestern University. Ming Han, a PhD student in Luijten's laboratory, and Jing Yan, a former graduate student at the University of Illinois, served as co-first authors of the paper.

Researchers expect that such active could open a new class of technologies with applications in medicine, chemistry, and engineering as well as advance scientists' fundamental understanding of collective, in systems.

According to the research team, the significance of team work was stressed by both Dr. Luijten and Dr. Granick as this current breakthrough is part of a longtime partnership using a new class of soft-matter particles known as Janus colloids, which Dr. Granick had earlier created in his laboratory. The theoretical computer simulations were completed by the team, led by Dr. Luijten and Dr. Granick used these colloids to experimentally test the collective, dynamic behavior in the laboratory.

The micron-sized spheres, typically suspended in solution, were named after the Roman god with two faces as they have attractive interactions on one side and negative charges on the other side.

The electrostatic interactions between the two sides of the self-propelled spheres could be manipulated by subjecting the colloids to an electric field. Some experienced stronger repulsions between their forward-facing sides, while others went through the opposite. Along with them, another set remained completely neutral. This imbalance caused the self-propelled particles to swim and self-organize into one of the following patterns, which are swarms, chains, clusters and isotropic gases.

To avoid head-to-head collisions, head-repulsive particles swam side-by-side, forming into swarms. Depending on the electric-field frequency, tail-repulsive particles positioned their tails apart, thus encouraging them to face each other to form jammed clusters of high local density. Also, swimmers with equal-and-opposite charges attracted one another into connected chains.

Dr. Granick states, "This truly is a joint work of the technological know-how by the Korean IBS and the University of Illinois, as well as the computer simulations technology by Northwestern University." He expects that this breakthrough has probable application in sensing, drug delivery, or even microrobotics.

With this discovery, a drug could be placed within particles, for instance, that cluster into the delivery spot. Moreover, alterations in the environment could be perceived if the system unexpectedly switches from swarming to forming chains.

Explore further: Reconfiguring active particles into dynamic patterns

More information: Jing Yan, Ming Han, Jie Zhang, Cong Xu, Erik Luijten and Steve Granick, "Reconfiguring active particles by electrostatic imbalance", Nature Materials, 2016.

Related Stories

Reconfiguring active particles into dynamic patterns

July 11, 2016

From swarming bees to clustering bacteria colonies, nature stuns with its ability to self organize and perform collective, dynamic behaviors. Now researchers have found a way to mimic these behaviors in active materials on ...

Asymmetrical magnetic microbeads turned into micro-robots

July 20, 2016

Janus was a Roman god with two distinct faces. Thousands of years later, he inspired material scientists working on asymmetrical microscopic spheres—with both a magnetic and a non-magnetic half—called Janus particles. ...

Recommended for you

How heavy elements come about in the universe

March 19, 2019

Heavy elements are produced during stellar explosion or on the surfaces of neutron stars through the capture of hydrogen nuclei (protons). This occurs at extremely high temperatures, but at relatively low energies. An international ...

Trembling aspen leaves could save future Mars rovers

March 18, 2019

Researchers at the University of Warwick have been inspired by the unique movement of trembling aspen leaves, to devise an energy harvesting mechanism that could power weather sensors in hostile environments and could even ...

Quantum sensing method measures minuscule magnetic fields

March 15, 2019

A new way of measuring atomic-scale magnetic fields with great precision, not only up and down but sideways as well, has been developed by researchers at MIT. The new tool could be useful in applications as diverse as mapping ...

0 comments

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.