This is DNA strand displacement logic, a particularly simple (yet surprisingly robust) style of DNA computing. They can chain together "logic gates" made from r

This is DNA strand displacement logic, a particularly simple (yet surprisingly robust) style of DNA computing. They can chain together "logic gates" made from reactions of partially complementary DNA oligonucleotides, computing arbitrary boolean logic functions, in an asynchronous logic style. The big potential here is that they can use this for drugs (and other biological purposes) that can do a bit of simple computation. Biology does this sort of thing all the time -- that's where it gets a lot of its power -- but this kind of simplified logic is easier for humans. Looking over the paper, it looks like they figured out how to combine their seesaw gates and thresholding gates into AND and OR gates, then from there, used dual-rail asynchronous logic to make a four-bit square root calculator. They can't make NOT gates (or NAND, or NOR), so each bit gets two "wires", holding opposite values; this lets them make arbitrary logic without NOT operations. There's a pretty slick simulator program you can play with here, along with more information, if anybody's interested: http://research.microsoft.com/en-us/projects/dna/ http://research.microsoft.com/en-us/projects/dna/