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nanotimes News in Brief
one-dollar bill and the surrounding words approxi- mately 19,000 times at 855 million dots per square inch. Each image consists of 6,982 dots. (They reproduced a bitmap representation of the pyramid, including the “Eye of Providence.”) This exercise highlights the sub-50-nanometer resolution and the scalability of the method.
“Hard-tip, soft-spring lithography is to scanning- probe lithography what the disposable razor is to the razor industry,” said Chad A. Mirkin, the paper‘s senior author. “This is a major step forward in the realization of desktop fabrication that will allow researchers in academia and industry to create and study nanostructure prototypes on the fly.”
Wooyoung Shim, Adam B. Braunschweig, Xing Liao, Ji- nan Chai, Jong Kuk Lim, Gengfeng Zheng & Chad A. Mir- kin: Hard-tip, soft-spring lithography, In: Nature, Volume 469(2011), Number 7331, January 27, 2011, Pages 516- 520, DOI:10.1038/nature09697:
http://dx.doi.org/10.1038/nature09697
In a paper published online in the journal Nano Let- ters, Horacio Espinosa, the James N. and Nancy J. Farley Professor in Manufacturing and Entrepre- neurship at the McCormick School of Engineering and Applied Science at Northwestern University, and Ravi Agrawal, a graduate student in Espinosa’s lab, reported that piezoelectricity in GaN and ZnO nanowires is in fact enhanced by as much as two orders of magnitude as the diameter of the nano- wires decrease.
The researchers’ results show that the piezoelectric coefficient in 2.4 nanometer-diameter nanowires
11-01 :: December 2010 / January 2011
is about 20 times larger and about 100 times larger for ZnO and GaN nanowires, respectively, when compared to the coefficient of the materials at the macroscale. This confirms previous computational findings on ZnO nanostructures that showed a simi- lar increase in piezoelectric properties. However, calculations for piezoelectricity of GaN nanowires as a function of size were carried out in this work for the first time, and the results are clearly more promising as GaN shows a more prominent incre- ase.
“We used a computational method called Density Functional Theory (DFT) to model GaN and ZnO nanowires of diameters ranging from 0.6 nanome- ters to 2.4 nanometers,” Agrawal said. The com- putational method is able to predict the electronic distribution of the nanowires as they are deformed and, therefore, allows calculating their piezoelectric coefficients.
Ravi Agrawal and Horacio D. Espinosa: Giant Piezoelec- tric Size Effects in Zinc Oxide and Gallium Nitride Na- nowires. A First Principles Investigation, In: Nano Letters ASAP, January 11, 2011, DOI:10.1021/nl104004d:
http://dx.doi.org/10.1021/nl104004d
The group of PMs & Application of the Ningbo Institute of Material Technology and Engineering (NIMTE), CAS, China, have been presented at the 55th Annual Conference on Magnetism and Magne- tic Materials a new preparation technique of high- performance magnets. Generally, the high-perfor- mance permanent magnet means a magnet with a high energy product, high coercivity, and high work
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