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nanotimes News in Brief

Metamaterials // Switchable Nanomaterials

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esearchers at Northwestern University created a metamaterial that’s capable of steer electric

currents in whichever direction is desired at the time. The researchers show that electrical conduc- tance through films of gold nanoparticles coated with a monolayer of charged ligands can be controlled by dynamic, long-range gradients of both mobile coun- terions surrounding the nanoparticles and conduc- tion electrons on the nanoparticle cores.

The internal gradients and the electric fields they create are easily reconfigurable, and can be set up in such a way that electric currents through the nano- particles can be modulated, blocked or even de- flected so that they only pass through select regions of the material. The nanoion/counterion hybrids combine the properties of electronic conductors with those of ionic gels/polymers, are easy to process by solution-casting and, by controlling the internal gradi- ents, can be reconfigured into different electronic elements (current rectifiers, switches and diodes).

Hideyuki Nakanishi, David A. Walker, Kyle J. M. Bishop, Paul J. Wesson, Yong Yan, Siowling Soh, Sumanth Swami- nathan, Bartosz A. Grzybowski: Dynamic internal gradients control and direct electric currents within nanostructured materials, In: Nature Nanotechnology AOP, October 16, 2011, DOI:10.1038/nnano.2011.165: http://dx.doi.org/10.1038/nnano.2011.165 http://dysa.northwestern.edu

Image: By applying electrical pulses to the new nanoma- terial, a sea of small negatively charged ions (blue) can be pushed and pulled between larger, positively charged nanoparticles (red) which are “jammed” in place. © Northwestern University

11-10 :: October 2011