Somewhere along the line nanotechnologists have got it into their heads that nanoparticles ought to do self-assembly. Oh wait. They may have met a biologist. Living things do self assembly all the time, and much of it takes place at the molecular nanoscale. So why not nanotechnology? (Uh, life took millions of years to achieve self-assembly – and we still don’t know precisely how.) Do nanotechnologists expect to do this in a few decades (or less)? Yes, they do…

If the promise of nanotechnology is to be fulfilled, nanoparticles will have to be able to make something of themselves. An important advance towards this goal has been achieved by researchers with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) who have found a simple and yet powerfully robust way to induce nanoparticles to assemble themselves into complex arrays.
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“We’ve demonstrated a simple yet versatile approach to precisely controlling the spatial distribution of readily available nanoparticles over multiple length scales, ranging from the nano to the macro,” says Ting Xu, a polymer scientist who led this project and who holds joint appointments with Berkeley Lab’s Materials Sciences Division and the University of California, Berkeley’s Departments of Materials Sciences and Engineering, and Chemistry.
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Nano-sized particles – bits of matter a few billionths of a meter in size, or more than a hundred times smaller than the stuff of today’s microtechnologies – display highly coveted properties not found in macroscopic materials, including optical, electronic, magnetic, etc. The promise of nanotechnololgy is that exploiting these unique properties on a commercial scale could yield such “game-changers” as sustainable, clean and cheap energy, and the creation on demand of new materials with properties tailored to meet specific needs. Realizing this promise starts with nanoparticles being able to organize themselves into complex structures and hierarchical patterns, similar to what nature routinely accomplishes with proteins.
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For this study, Xu and her colleagues added [PDP or OPAP] small molecules to various blends of nanoparticles, such as cadmium selenide and lead sulfide, mixed in with a commercial block copolymer – polystyrene-block-poly (4-vinyl pyridine). While she and her group worked with light and heat, she says other stimuli, such as pH, could also be used to reposition small molecules and their nanoparticle partners along block copolymer formations. Strategic substitutions of different types of stimulus-responsive small molecules could serve as a mechanism for structural fine-tuning or for incorporating specific functional properties into nanocomposites.

“Bring together the right basic components – nanoparticles, polymers and small molecules – stimulate the mix with a combination of heat, light or some other factors, and these components will assemble into sophisticated structures or patterns,” says Xu. “It is not dissimilar from how nature does it.”

[Source: Berkeley Lab]

There are many other approaches to nano-manufacture – using nanoparticles to make nano-structures. In all cases, the difficult first step is exerting some control. Some researchers are using highly controlled environments (magnetism, light) and controlled nanoparticles compositions; others are looking to natural models. It’s really a continuum of approaches, and it’s not a horse race to see which approach ‘wins.’ In all likelihood, there will be successes of different kinds and with different methods.