AsianScientist (Jul. 28, 2016) – Soft-matter particles, named Janus colloids after the two-faced Roman god, can be manipulated with electricity to form swarms, chains and clusters, a study shows.
The study, led by Dr. Steve Granick of the Institute of Basic Science in South Korea and published in Nature Materials, takes lessons from cooperation in Nature, including those observed in honey bee swarms and bacterial clusters.
The Janus colloids have attractive interactions on one side and negative charges on the other side. By subjecting the colloids to an electric field, some spheres experienced stronger repulsions between their forward-facing sides, while others went through the opposite. Alongside this electrically-stimulated spheres, another set was left completely neutral. This imbalance caused the self-propelled particles to swim and self-organize into one of the following patterns: 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.
Granick expects that such active particles could open a new class of technologies with applications in sensing, drug delivery, or even microrobotics. A drug could be placed within particles that cluster into the delivery spot, for instance. Such work could also advance scientists’ fundamental understanding of collective, dynamic behavior in systems, he says.
The article can be found at: Yan et al. (2016) Reconfiguring Active Particles by Electrostatic Imbalance.
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Source: Ulsan National Institute of Science and Technology.
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