Improvements to a cryosystem to observe ice nucleating in a variable pressure scanning electron microscope.

The variable pressure scanning electron microscope (VPSEM) has expanded the scope of the SEM to allow the imaging of dynamic, electrically insulating systems. The use of water vapor as the imaging gas present in the chamber allows the successful imaging of hydrated samples. As awareness of the system capabilities becomes more well known, greater pressure has been put onto the microscopist to push the boundaries of both temperature and resolution for the study of diverse hydrated samples whose dynamics may not occur at the usual room temperatures in a VPSEM. In this article we discuss the stages in the development of a cryosystem that has led to the successful observation of the nucleation of ice from a solution in situ. This investigation also leads to further possibilities of imaging hydrated samples in the little explored temperature range of 188–238 K (from -85 to-35 °C). This study includes the exploration of how the temperature of various surfaces inside the microscope will change the system’s ability to keep a sample hydrated or in its native state. [ABSTRACT FROM AUTHOR]