Image: Wolfgang Lechner (Foto: IQOQI)

[2013-04-08] A team of Austrian physicists has suggested ordering nanoparticles with laser light. In the long-term, this method could be used for crystallizing biomolecules.

The research team of Wolfgang Lechner, Steven Habraken and Peter Zoller has had a lot of experience in optically manipulating matter such neutral atoms, ions or other bigger objects. They have now published a suggestion of how to utilize optomechanical methods for nanoengineering. The theoretical physicists in Innsbruck collaborate closely with  Markus Aspelmeyer's research team in Vienna, which performs experiments with macroscopic objects, exploring the border between quantum physics and classical physics.

Optical friction forces

The nanoparticles consist of two dielectric silicon dioxide particles (spheres) that are connected via a DNA molecule, which creates an object that looks like a miniscule dumbbell. This DNA technique is already used to produce complex nanostructures. However, the Austrian physicists go one step further: They trap the nanoparticles in an optical resonator in vacuum, where laser light ensures that the particles move on one level only. Laser light has the same effect as friction and induces orientational ordering of the nanoparticles.

Creating order

“Laser light causes the nanoparticles to orient themselves into a specific direction,” explains Wolfgang Lechner. “When the nanoparticles are electrically charged, they are also ordering in a regular pattern.” A crystal is formed in the resonator, which has the same properties as a liquid. “This structure behaves like a liquid crystal similar to the ones you find in LCD displays,” says Lechner. “The prerequisite is the energetically nonequilibrium state of the nanoparticles. Energy is steadily absorbed and dissipated. In combination with laser light, this forces the particles into ordering,” underlines  Lechner. The experimental physicists in Vienna are planning to realize this concept very soon.

Production of drugs

“This project is about using nanostructures and to manipulate their internal organization with laser light,” adds Peter Zoller. In the long term, similar concepts could be useful for producing drugs. Active ingredients are prepared in solutions and then crystallized so that they can be administered in the form of pills or powders.  The ordering of the crystal is crucial for the drug's effectiveness. New technologies may help to induce order. In addition, this proposal may allow to measure elastic properties of the DNA attached to the nano-spheres with high precision.

The work has been published in Physical Review Letters. The researchers are supported by the Austrian Science Fund, the European Union and the Federation of Austrian Industries Tyrol.

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