It's not often I write a little article about a scientific paper without changing the title to something catchier, but I really think in this case the study's authors came up with the most awesome possible title. DNA origami robots!
The idea behind this work is that biological systems are really just collections of things moving around and bumping into each other in a fairly controlled fashion. Actually, in a very impressively controlled fashion when you think about how complex these systems can be. So far, scientists haven't really been in the same league as mother nature when it comes to making man-made systems that can mimic or interact with those that evolution has established, but that is beginning to change.
In this paper, the researchers report they were able to implement of series of basic logic gates that actually functioned inside a live cockroach. For example, an AND gate was a DNA robot that held a payload which could only be released if and only if two correct stimuli were present. They were also able to implement OR, XOR, NAND, NOT, half adder and CNOT logic gates. This is an actual line in the paper: "The basic concept we describe can be scaled plausibly to exceed the capacity of older 8-bit computers such as a Commodore 64 or Atari 800, which many of us had experience of as children" which is SO COOL. An 8-bit programmable biomachine that works inside a living creature!
The applications for this are many-fold. Drug delivery is obviously a primary objective, with the DNA origami logic allowing for precise control over the timing and location of delivery. Diagnostic applications are also envisioned where the robots could be programmed to release fluorescence tags in the presence of particular diagnostic biomolecules.
You can give the original paper a read in Nature Nanotechnology.