The procedure of critical point drying is an efficient method for drying delicate samples for SEM applications. 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 the past critical point drying was a time-consuming process with low sample reproducibility due to manual operation.
Before drying, many biological samples are commonly prepared through fixation and dehydration and coated after drying with a metal such as gold, platinum or palladium to make their surfaces electrically conductive for the SEM analysis.