“You can think of nanocrystals as building blocks like the toy Lego, in which a larger structure can be assembled by locking in the pieces according to their shape and the way they prefer to join to each other,” O’Brien says. “Except all of this is on an incredibly small lengthscale — billionths of a meter.”

The Columbia/IBM team has borrowed ideas from the natural world, in which the right conditions can stimulate the slow growth of highly uniform structures out of miniature building blocks. Opals are an example of this phenomenon: opals consist of tiny spherical building blocks of silica packed into an ordered structure. In this new research, the materials used as building blocks are a variety of man-made nanocrystals with known useful magnetic or electronic properties.

“This work may lead to the development of an entirely new class of multifunctional materials in which there are cooperative interactions between the nanocrystal components,” says MRSEC director Irving P. Herman, also a professor of applied physics. “Moreover, the properties of these nanocrystals can be tailored during synthesis, and they can be deposited to form the desired ordered array by controlling particle charge and other properties. O’Brien’s study also demonstrates the value of vibrant collaborations between universities and industry.”