By attaching short sequences of single-stranded DNA to nanoscale building blocks, researchers can design structures that can effectively build themselves. The building blocks that are meant to connect have complementary DNA sequences on their surfaces, ensuring only the correct pieces bind together as they jostle into one another while suspended in a test tube.
Earlier work assumed that the liquid medium in which these DNA-coated pieces float could be treated as a placid vacuum, but a Penn team has now shown that fluid dynamics play a crucial role in the kind and quality of the structures that can be made in this way.
As the DNA-coated pieces rearrange themselves and bind, they create slipstreams into which other pieces can flow. This phenomenon makes some patterns within the structures more likely to form than others.