The term “bottom-up” was originally used to refer to molecule-by-molecule assembly of atomically-precise products. But more recently we’ve seen the term used to describe processes that produce products which are not atomically precise. The following Azonano item is an example of this usage. However, it seems likely that this kind of research — which does use an atomically-precise tool, DNA — will also contribute to the former goal as well, at some point. See the PDF or online paper:
Brown Researchers Use DNA to Direct Nanowire Assembly and Growth
A research team led by Brown University engineers has harnessed the coding power of DNA to create zinc oxide nanowires on top of carbon nanotube tips. The feat, detailed in the journal Nanotechnology, marks the first time that DNA has been used to direct the assembly and growth of complex nanowires.
The tiny new structures can create and detect light and, with mechanical pressure, generate electricity. The wires’ optical and electrical properties would allow for a range of applications, from medical diagnostics and security sensors to fiber optical networks and computer circuits…
The work is an example of “bottom up” nanoengineering. Instead of molding or etching materials into smaller components, such as computer circuits, engineers are experimenting with ways to get biological molecules to do their own assembly work. Under the right chemical conditions, molecular design and machinery – such as light-sensing proteins or viral motors – can be used to create miniscule devices and materials.
In this work, the team of engineers and scientists took the “bottom-up” approach one step further by successfully harnessing DNA to provide instructions for this self-assembly. The new structures created in the Xu lab are the first example of DNA-directed self-assembly and synthesis in nanomaterials…
“DNA provides an unparalleled instruction manual because it is so specific,” Lazareck said. “Strands of DNA only join together with their complements. So with this biological specificity, you get manufacturing precision. The functional materials that result have attractive properties that can be applied in many ways.”
“We’re seeing the beginning of the next generation of nanomaterials,” said Xu, senior author of the article. “Many labs are experimenting with self-assembly. And they are making beautiful, but simple, structures. What’s been missing is a way to convey information – the instruction code – to make complex materials.”