The robot arena is made from a single strand of DNA (7200 nucleotides) origami folded into a 2-dimensional platform measuring 65 nm x 390 nm x 32 nm with the aid of staple strands. Each spider leg on contact with a substrate site (a oligonucleotide) at the platform , catalytically cleaves it at the ribose unit. As each leg has higher substrate affinity than product affinity it will favor spots on the platform not yet trampled upon and a walking movement ensues.
The staple strands are fitted with probes that stick out from the surface serving special purposes: they form START (complementary to the TRIGGER), TRACK (substrate) and STOP (uncleavable substrate analogs) sites. A TRIGGER oligonucleotide sets the spiders in motion with an average speed of 180 nanometer per hour. The article is accompanied by a set of very fuzzy AFM images revealing the spider movements that could just as easy be taken as evidence for the Loch Ness monster. Also included are position-time trajactories obtained from total internal reflection fluorescence microscopy which required fluorophore labeling of spiders and STOP sites.
There is always the possibility that a spider dissociates all three legs simultaneously and makes a jump to a new section of the platform. As no spiders were found at so-called CONTROL sites (a STOP site well off a track) we should be reassured this does not happen.