The procedure of critical point drying is an efficient method for drying delicate samples. It preserves the surface structure of a specimen which could otherwise be damaged due to surface tension when changing from the liquid to gaseous state. In this way it is used to avoid stiction and surface tension problems when drying fragile samples.
Its working principle is based on the critical point where the liquid CO2 transforms in gaseous CO2 and above critical point isotherm it is always a gas. Below this point it can exist as a liquid gas or both.