I am currently reading this paper: Auto-adhesion model for MEMS surfaces taking into account the effect of surface roughness
In their numeric example, they find a critical distance for capillary condensation to occur as being -3.5nm. Why negative ?
Here is the extract from the paper:
I know that log(0.5) is −log(2), hence negative, but I am rather interested in the physical meaning of this ? There is no negative distance between two plates ! So... what does this mean ? Is it maybe measured in a inverted reference ??