Page 11 Operating Manual EM CPD300 12/18
For biological and most micro-electro-mechanical (MEM) samples, critical point
drying cannot be performed with water. Water’s critical point is at 374°C and
228.5bar. Every biological and MEM sample would be destroyed at this temperature
and pressure. Therefore, the use of CO
2
as transitional fluid is the first choice for
critical point drying. It is liquid at room temperature at a comparative low pressure of
60bar. Its critical point is at 31°C and 73.8bar. Technically these temperature and
pressure requirements of the CO
2
can be implemented relatively easily. Hence, the
water in the cell is replaced by an exchange medium like acetone or ethanol, which
unlike water, are very soluble with liquid CO
2
. After the replacement of the water by
an exchange fluid, this exchange medium is substituted with liquid CO
2
through serial
dilution steps. Thereafter by increasing the temperature, the pressure is increased
proportionally and will transfer the CO
2
through its critical point into a supercritical
state (B). At constant temperature the controlled and carful depressurization converts
the supercritical CO
2
into its gaseous phase without crossing the phase boundary
between liquid and gas (C). After coating, the dried sample can be analyzed in a
scanning electron microscope (SEM).
Comparison between air and critical point drying:
Critical point dried sample (Water flea)
Air dried sample (Water flea)
Summary of Contents for EM CPD300
Page 1: ...From Eye to Insight OPERATING MANUAL EM CPD300 167180032 Version 12 18 ...
Page 30: ...Page 27 Operating Manual EM CPD300 12 18 Press Start to activate program Test ...
Page 48: ...Page 45 Operating Manual EM CPD300 12 18 After software update press back ...
Page 52: ...Page 49 Operating Manual EM CPD300 12 18 Remove poral filter with spring from the nut ...
