5
Alter the depth of the dispenser (#10) so that when the dispenser (#9) is pushed down the syringe does
not hit the sample. Do this as when the syringe hits the sample it might damage the surface and alter the
contact angle data obtained.
Lower an appropriate drop from the syringe. Click Start from controls, press down and release on the
dispenser (#9) and wait for the images to be recorded.
Curve fitting for all the experiment types is explained in chapter 2.5.
2.4 Pendant drop experiments
A Pendant drop experiment is very similar to a Contact angle experiment in procedure. A note on terms:
a surface tension measurement involves a liquid drop and a gas whereas an interfacial tension
measurement involves two liquids.
Preliminaries
Clean the syringe, place the liquid into it and attach it to the syringe clamp (#11). With a standard surface
tension measurement, lower the sample stage (#13) so that it is out of the way.
With a standard interfacial tension measurement place the less dense liquid in the syringe, the denser
liquid in a cuvette and the cuvette on the sample stage (#13). Change the syringe needle to a hook
needle and attach the filled syringe to the syringe clamp (#11).
From the main Theta tab choose the Pendant drop experiment.
Image recording
Fill in the relevant data in the recipe sheet. It might be necessary to add users, liquids or solids to the
database manager found in the Setup tab.
With a surface tension measurement simply lower an appropriate drop. With an interfacial tension
measurement lift the sample stage (#13) until the cuvette is visible, lower the hook needle into it, lower
an appropriate drop and select Flip Y. Press Start from the controls and wait for the images to be
recorded.
2.5 Curve fitting and data analysis
After recording, choose the Analysis tab and double click your experiment. Accept either the default
fitting parameters or adjust them from the Drop analysis window. The software will then process all of the
chosen images. The red line represents the baseline, and it should connect the widest points of the
curve profile and its reflection to each other. Check this visually, and if unsatisfied unselect Use
automatic baseline and set it manually. In sessile drop contact angle experiments the baseline is set at
the solid surface, whereas in pendant drop experiments it is adjusted at the end of the needle.
By right clicking on the results you are able to perform further data analysis, for example by hiding
unnecessary data points, by drawing graphs or by creating statistics from the chosen data points. You
find also option to export data by right clicking on the results. By right clicking on the drop image you are
