Because the researchers conducted their analysis using computer modeling, they cautioned that experimentally reproducing the results in a lab presents some difficult challenges. One early concern involved the uniformity of colloids in the suspension; models often assume colloids are all the same shape and size but this rarely occurs in natural systems. Anticipating this, the researchers tested their theory using a non-uniform solution.
"One of the things we did in our study was to look at realistic systems, that were realizable in the lab, and it appears that the phenomenon that we describe is robust," said Sanat Kumar, a professor and chair of chemical engineering at Columbia and a researcher on the project. "That tells us that there is no conceptual problem to realizing this in the lab."
Gravity could also pose a problem for experimenters, although Kumar pointed out that similar experiments have overcome this difficulty. Gravity causes crystals to filter to the bottom of a container and pack in mismatched layers. This can make it very difficult, and perhaps impractical, to try to produce the crystals by using a colloid mix in a tank.
But Mahynski said there are several techniques that could avoid problems. For example, to deal with gravity, researchers could create the crystals in a very thin film. That approach should avoid the disruption of gravity pulling the crystals to the bottom.
It also could be important to select the right size of colloid and type of polymer for a successful experimental result. Panagiotopoulos said that one possible path for these ideas to be experimentally verified will be to use polymer chains that are stiff, such as double-stranded DNA, together with micrometer-sized colloids.
|Contact: john sullivan|
Princeton University, Engineering School