Poisson's ratio changable of carbon nanotube sheet
Here is a recent work on the Poisson's ratio of carbon nanotube sheet . From the experimental results, the researchers found that the Poisson's ratio could change from 0.06 to -0.20 as the content of MWNTs increasing from 0~100%. The interesting zero Poisson's ratio and auxetic materials were thus found.
Ref.  Sign Change of Poisson's Ratio for Carbon Nanotube Sheets. Science 25 April 2008: 504-507
Department of Engineering Mechanics, Tsinghua University