Sharp Divide over a Smooth Change – recent work led by JC Tsai and WT Juan, published in Physical Review Letters
Suppose you heat a rod at one end, creating a smooth change of temperature from high on one side to low on the other, you anticipate that ants on the rod would all want to walk against the heat. But could you imagine that things might react differently and even have a split of their directions? This does happen, if a transition of behaviors occurs at some point along the gradient of temperature!
With a simple setup of a plate, a bearing, a few springs and an electromagnetic coil, researchers led by JC Tsai and WT Juan at the Institute of Physics, Academia Sinica, Taipei, Taiwan create a smooth gradient of vibration, like the temperature, and demonstrate that an object as unintelligent as just the key chain in our everyday life can show a sharp divide on its “decision” of the migration, as a consequence of a transition on its reaction mode. Furthermore, they prove that such a dramatic divide reflects a dialogue between the size of the object and the gradient. Such an interesting dialogue has never been reported in the long tradition of studies on gradient-induced migrations of either passive molecules (such as thermophoresis) or active organisms (thermotaxis/chemotaxis). Their demonstration suggests new territories yet to be explored and that “scientific discovery might require certain instrumentation, but not much”.
See http://dx.doi.org/10.1103/PhysRevLett.112.058001 (5-page paper on PRL) and demo movies at http://www.phys.sinica.edu.tw/jctsai/gradient/movies.htm for the dramatic spatial divide.
Journal Links: http://www.phys.sinica.edu.tw/index_detail.php?id=research&newsid=351