In a recent post, we discussed how some liquids containing bacteria swimmers can display negative viscosity. This can be a misleading since the apparent negative viscosity occurs due to swimmers pushing the surrounding fluid so that the overall system shows negative resistance to flow (i.e. it flows by itself!). One of the best examples of super fluidity is super cooled helium.
Using string theory, it was shown in 2004 that the lower limit for the viscosity to entropy ratio was h/4π, which will result in a perfect liquid with much lower viscosities than super cooled helium. In 2005, scientists from LHC at CERN showed that quark-gluon plasma exhibited a viscosity just above that theoretical limit. However more recently, they revisited the assumption of the plasma in a collision being isotropic (i.e. displayed same properties in all directions). If the anisotropy (i.e. properties are dependent on direction) of the plasma is included in their model, the viscosity in the direction of the collision is surprisingly lower than the theoretical prediction (Phys. Rev. Lett. 108, 021601).
Rheosense’s m-VROC® can only go as low as 0.2 cP but on the other hand, you will not need to worry about the earth being crushed into a black hole while you perform your measurements of viscosity!
Read more here: http://www.sciencedaily.com/releases/2012/01/120117143513.htm