A "bare" (no silicon wafers) uncoated C-cage and a bare parylene-coated C-cage were subjected to the test described above. Figure 6a, showing the average percent change in width, indicates that at low humidity, both the coated and uncoated cages reached equilibrium in ~ 40-60 hours. At high humidity, the uncoated cage reached its maximum change and equilibrium after 100 hours, while the coated cage had not yet reached its maximum change and equilibrium after 240 hours.
Figure 6a also shows that the coated and uncoated cages change
=+0.65% with a relative humidity change of ~ +60% . From
this data we infer that a relative humidity change of -30%
(30% to 0% ) will result in a -0.3% change in cage width. This
scenario is not likely to occur because of the experiment location.
The most dramatic result in figure 6a can be observed when looking
at the 40 hour time span between 260 and 300 hours. The bare uncoated
cage changed by =0.5% while the coated cage changed by
=0.2%, approximately a factor of two difference. This indicates
that the Parylene is increasing the time constant, or the amount of time it
takes the Rohacell to absorb moisture.
Figure 6b, shows the average change in radial distances for both the
coated and uncoated cages. The changes agree within errors at both low
and high humidities. The radial distances changed by about
=0.85% and did not exceed the =+/-1.7% physics
constraint. This dimension stabilized after a similar amount of time as
the widths.
Figure 6c, showing the change in length, indicates that the uncoated and coated cages again behave similarly at equilibrium. At high humidity, it takes longer for the parylene coated C-cage to equalize. In addition, there is a factor of two difference between the changes in the coated and uncoated cages when examining the 40 hour time span when the cages are first exposed to high humidities.