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The analysis of surface
tension relaxation contributes to the understanding of different
physical mechanisms in or around the surface. This type of study is conducted by making one or
more sudden changes (steps) to the drop volume of a pendant or sessile drop while
dynamically measuring the surface tension. The steps can be positive or
negative.
Researchers have used relaxation
studies to better define the viscoelastic properties of solutions and
surfactant monolayers. The relaxation of the surface after a sudden
change in volume can also measure the kinetics of absorption and
desorption.
Cicciarelli, Hatton, and Smith1
demonstrate dynamic surface tension behavior in a photoresponsive
surfactant system. In their referenced study, they measured dynamic
surface tension under different illumination scenarios. They found that
under UV lighting, the surface tension of their samples exhibited a
sharp drop in initial surface tension, followed by a plateau of constant
surface tension, and then finally ending with a second relaxation. They
concluded that the behavior can be explained by competitive absorption
between various isomers present in their test liquids.
1 Langmuir, 23 (9), 4753
-4764, 2007. 10.1021/la062814k S0743-7463(06)02814-9
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DROPimage Advanced v2.2 |
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This month we announce the release of v2.2
of DROPimage Advanced. Earlier in the year we released v2.1 which is now
compatible with Windows Vista operating system. DROPimage Advanced v2.2
now includes new tools for conducting relaxation studies. Note that a
ramé-hart Automated Dispensing System is required to use this feature.
The following changes have been made:
First, the methods editor has been enhanced to now include the number of
steps, or pulses, in a relaxation experiment. Other measurement types include "constant volume" and
"oscillation". Note that the existing event file editor can also be used
to define a relaxation study.
The key parameters to a relaxation
experiment are: step volume and number of steps. If a negative step
volume is specified, then volume is retracted from the drop. Typically
the step volume may be in the 2-4μL range. The number of steps should be
even; four is a good place to start. The time interval is also set (say
1 second).
Additionally, DROPimage Advanced v2.2
now includes a Relaxation Calculation tool as shown above. The
calculation and graphing tool requires the log file from a previously
run relaxation experiment. The data can be added and removed from the
graph easily one step at a time -- or all at once. The Calc
buttons are used to calculate the following values:
Please contact us if you are interested
in obtaining more information on the relaxation support in DROPimage
Advanced v2.2. Upgrades are available; however, this version will
require a digital camera. If you are currently running DROPimage v1.5 or
older, you may need our analog to digital upgrade kit (p/n 400-22-F1).
Note that all new Model 250-F1 and 500-F1 goniometer orders will begin
shipping this month with v2.2. DROPimage Standard has also been upgraded
to v2.2 and supports Windows Vista but does not include any support for
relaxation. |
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Regards,
Carl Clegg
Director of Sales
Phone 973-448-0305
www.ramehart.com
Contact us |
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