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The bottom image shows particles being sucked into the donut shaped microfluidic vortex, resulting by the hologram-laser approach. The nanoparticles concentrate into a tight clump, ideal for nanoassembly.  (Source: Purdue University)
Laser and hologram method could also be useful for positioning molecules in labs-on-a-chip

When it comes to nanodevices, scientists have no problem cooking up interesting designs.  However, when it comes to actually assembling such machines on a nanoscale, it can be a daunting task.

A breakthrough from Purdue University offers up a new technique that may be extremely useful in such nanoassembly.  The new method uses lasers and holograms to position multiple nanoparticles within seconds, much faster than previously possible.  The method could also be very helpful to labs on the chip, which need to direct tiny molecules to tiny test locations.

The name for the new process -- rapid electrokinetic patterning -- is a bit overwhelming, but it’s an incredibly promising technology according to researcher Stuart J. Williams.  Mr. Williams, who is working with doctoral student Aloke Kumar and Steven T. Wereley, an associate professor of mechanical engineering, states, "It's potentially a very versatile tool."

His method uses two parallel electrodes made of indium tin oxide.  Indium tin oxide is a transparent conductive material.  A tiny gap of 50 micrometers, or approximately the diameter of a human hair, separates the parallel plates.  By simultaneously apply a current to the plates and shining a laser through them, holograms can be created that position molecules travelling between the plates.

In a test, the team position fluorescent beads.  Mr. Kumar describes, "We send holograms of various patterns through this and, because they are holograms, we can create different shapes, such as straight lines or L patterns."

By creating desirable patterns, molecules, which are drawn to the hologram's pattern between the plates, could be assembled into features for nanomachines.  This could enable a miniature assembly line which produces nanomachines piece-wise. 

The system is very flexible.  Says Mr. Kumar, "It's a very dynamic system, so we can change this pattern quickly."

The process works due to heating.  The lasers heat the fluid between the plates slightly.  By applying a current, the heated fluid begins to swirl, much like convective currents, except on a microscopic basis.  The resulting "microfluidic vortex" sucks molecules in.  By altering the laser and the current, different vortex shapes can be attained.

Mr. Williams describes, "You could take one particle, a hundred particles or a thousand particles and move them anywhere you want in any shape that you want.  If you have particles of two different types, you can sort one group out and keep the other behind. It's a versatile tool."

The method could result in both assembly and lab-on-a-chip designs far better than the current methods at moving and congregating molecules.  Currently one popular method is optical trapping, which uses a beam of light to move particles.  This method, however, is too slow compared to the new method, as it moves too few particles.  The other alternative -- dielectrophoresis -- is comparably fast, but its patterns cannot be changed after the current is switched on.

The device could help further the lab-on-a-chip revolution in the medical industry, which promises better detection of cancer and many other diseases.  Describes Mr. Williams, "If you want to pattern individual particles on a massive scale using electrokinetic methods as precisely as we are doing it, it could take hours to days, where we are doing it in seconds.  For example, a single drop of blood contains millions of red blood cells and countless molecules.  You always want to have the smallest sample possible so you don't generate waste and you don't have to use as many chemicals for processing the sample. You want to have a very efficient high throughput type of device."

A video of the technique in action is available here.

The research won the first place award in April at the Birck Nanotechnology Center award.  It is funded by the grants from the National Science Foundation.

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RE: Yay for Star Trek!
By Chipper Smoltz DT on 12/4/2008 7:06:49 AM , Rating: 2
Nope we don't have a transporter.

Assuming that we could have nanoparticles the size of photons, that would be enough. By using these photon sized nano-particles and (if they behave as photons as well) what we could have is something that could be used to assemble these stuff once it has reached its destination. Let's say, these nano-particles are similar in size and behavior to a photon - we could just make use of light or RF waves to direct these particles to a certain destination. Once it's there we could assemble these particles easily (like the article claims) into something that would be so special like a tool or even parts of a habitat. What we would be needing then is something to collect those particles that we transmitted - much like a solar panel collects the photons from the sun and stores it as energy.

Once this is done - we could just easily rebuild anything from these "nano-photonlike particles" with this technology thus saving us:

1. time to go to that certain destination
2. resources to go to that certain destination

Although, a reassembler device has to be built first in the destination where it's supposed to be located. Anyway, they will soon discover that "particle - collector" if ever and / or they would soon make nano-particles that are similar to photons.

Am just imagining lots of these "nano-particle like photons" being beamed directly even though they are so small but very huge quantities could somehow help us in building something big and nice. Mostly for space applications but it could also be here for us in Earth.

Somewhat similar to a matter transporter but I don't believe it could be used for something organic like us humans, nor flora and fauna. But maybe in the not so distant future, something could be invented that would be similar to the matter transporter of Star Trek. We could all dream can't we? Even though some dreams are not and will never be reality. Hahaha

"I'd be pissed too, but you didn't have to go all Minority Report on his ass!" -- Jon Stewart on police raiding Gizmodo editor Jason Chen's home

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