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June 27, 2007

Nanowires for imaging and more

New Scientist reports on nanowires suspended in an invisible "force field" of laser radiation could soon be peering into biological samples, taking
low-cost snapshots of viruses and proteins with unprecedented resolution.

The team's prototype can already scan objects with a resolution of 100 nanometres, allowing it to capture the features the size of those on a silicon chip. The researchers believe they should be able to refine the device so that it will ultimately have a resolution of tens of nanometres.


Here is the Peidong Yang's nanowire photonics page


In a demonstration of the nanowire light source's fluorescence mode, a nanowire in the grip of an infrared beam was touched to a fluorescent bead causing the bead to fluorescence orange at the contact point. Figure a shows the experimental set up with the pair of beads on the right as control; b is a bright-field optical image of the beads, with the nanowire in contact with the leftmost bead; c is a color CCD fluorescence image showing green light emission from the nanowire and the orange emission from the bead; d is a control image of the same beads with infrared radiation but no trapped nanowire; and e is digital subtraction of d from c. (Image: Peidong Yang, Jan Liphardt, et. al.)

Nanowire expert Peidong Yang received the National Science Foundation's (NSF) 2007 Alan T. Waterman Award Yang has created one of the nation's leading laboratories for the study of nanowires.


Yang led the development of a nanowire laser that fires ultraviolet light. He and his colleagues grew the wire as part of an array using novel, efficient techniques. (Image: Nicolle Rager Fuller, National Science Foundation)

"Nanowires represent a rich family of functional materials," said Yang. "It is now possible to design and synthesize nanowires with quite complex structures based on progress made in the past couple of years. This type of control in nanostructural engineering has generated a rich collection of fascinating properties and functionalities, including nanoscale lasers, nanowire-based transistors, sensors and solar cells. These nanowire materials will have a particularly significant impact in areas such as energy conversion and solid-state lighting."



Chemist Peidong Yang, the winner of the National Science Foundation's 2007 Alan T. Waterman award, and his colleagues have grown arrays of zinc oxide and gallium nitride nanowires. (Image: Peidong Yang, University of California, Berkeley)

MIT Technology Review discusses Peidong Yang's work to use nanowires to guide stem cell growth


Bed of nails: Embryonic stem cells cultured on an array of silicon nanowires (above) can grow and develop into muscle cells. The mouse cells in this scanning electron microscopy image are about 10 microns across.
Credit: University of California, Berkeley

Electrical stimulation by nanowires, says Griffith, may "go into a collection of different kinds of cues for controlling cell behavior."

Nicholas Kotov, a chemical engineer at the University of Michigan, is developing retinal implants that connect to neurons using carbon nanotubes.

Harvard's Lieber cautions that Yang's group has not yet demonstrated an active electrical interface between the cells and nanowires, as he did with neurons and as Kotov and others have done with carbon nanotubes.

Yang says that turning on the electricity is his group's next step. "This is the first preliminary data that these nanowire interfaces with cells are okay," he says. He hopes further research will demonstrate that the nanowires, acting as electrodes and chemical-delivery vehicles, can be used to direct stem-cell fates.


FURTHER READING:
Peidong Yang's research group website

News on Peidong Yang's research

Nanowerk also covers this nanowire work

Rob Eason, of the Optoelectronics Research Centre at the University of Southampton, UK, was impressed by the research. 'The combination of these separate topic areas - growth and characterisation of nonlinear nanowires, optical tweezing, parametric frequency conversion, scanning near field microscopy, and subwavelength measurement - represents some kind of hero experiment,' Eason told Chemistry World. 'Individually each of these topics is a subject in itself, and so in combination is a tour-de-force in my view.'


Nanowerk also had this article on the work

Virginia Tech College of Engineering researcher Yong Xu is trying to reach 1 nanometer resolution for optical imaging using metamaterials

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