Actually, more like a wall for bacteria. Scientists have brought 3D printing down to the nanoscale with a new technique that uses electrospun polymer fibers as building blocks for printed structures.
For those of us who have worked with nanoscale objects, this represents a major potential development. Moving things around when they are too small even to be seen by a microscope is not a trivial task. It is time-consuming, complicated, usually pretty expensive and with a lot of potential for failure (or maybe that last one just applies to me). So the notion of building things at the nanoscale just using a computer design program is hugely appealing.
The authors of this new study in Langmuir used electrospinning, a technique in which a very high electric field is applied to a drop of polymer solution. Because the field is so large, the liquid becomes charged and electrostatic forces outweight surface tension. As a result, the drop gets all stretched out until it hits a sort of breaking point and a tiny jet of solution shoots out at the substrate.
The problem with this technique is you tend to just get a big tangled mass of polymer strands, not well-ordered structures. The authors solved this by using an insulating substrated patterned with a thin conductive strip to attract the electrospun fibers. If this idea seems pretty simple, that's because it is. And that's what makes it so cool. Many labs could afford to set up nanoscale 3D printers in this manner.
Their proposed uses include fabricating nanoelectrodes and transistors, bioscaffolds, nanofilters and (and I think they just threw this one in there for kicks) nanorobots!
Sometimes the simple stuff is the hardest to think up.
Check out the original study, Toward Nanoscale Three-Dimensional Printing: Nanowalls Built of Electrospun Nanofibers, here.
Figures reprinted with permission from Langmuir, 2014, 30 (5), pp 1210–1214. Copyright 2014 American Chemical Society.