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TRANSCRIPT
Contact Angle Goniometer Quick User’s GuideUpdated 12/15/2016
Start up
1. Turn on the HG-DM light for the goniometer.
2. Put your solvent in the syringe.
3. Use a level to make the stage
level (knobs D).
4. Mark the edge of a glass slide
with a marking pen and place
it on the platform.
5. Move the syringe so it almost
touches the slide.
6. Align the mark on the edge of
the glass slide with the syringe
needle.
7. Locate the AmScope camera box in the bench drawer and take out the camera
with lens attached.
8. Remove the eyepiece of the telescope on the goniometer.
9. Insert the camera into the telescope tube in place of the eyepiece
10. Plug the AmScope camera into the computer with the USB cable.
11. Start the software by clicking on the icon “AmScope” on the desktop.
12. Under the Camera List on the sidebar menu choose MU300 (if the sidebar menu is
not open click “Camera Sidebar”. The camera should begin to stream videos.
13. The analysis program like a 8 bit gray scale image and you can either set the
camera to collect Gray scale image (in “Color/Gray”) with an 8 bits depth (in “Bit
Depth”) or you can convert you image in ImageJ when you analyze it. A real time
image from the camera should appear on the computer screen.
14. If you want to take a movie you can set the Frame rate.
15. Adjust the light level by turning the knob on the lamp control.
16. Focus the camera on the edge of the slide by turning Knob A. If the slide does not
appear horizontal rotate the camera so it is. (See picture).
17. Move the stage (knob B and C) to align camera on the syringe needle (this should
be right above the mark on the slide but the image may be upside down that can
be fixed by rotating the camera:
a) Move the needle left/right with knob B and up/down with ring C to locate the
needle in telescope view
b) Focus the telescope on needle with knob A (see figure below).
18. Find end of the needle by moving syringe up and down (knob E).
19. Remove the glass slide and put your sample on the stage under the syringe.
20. Make sure the camera is aligned on the end of the needle.
21. Expel one drop of water onto your sample.
22. Focus camera on the drop on the substrate.
23. You would like the main part of the drop to be black with a white hole in the
middle due to the refraction of the light. If there are other light spots in the drop
you might have reflections for the overhead light that you should try to get rid of.
To take pictures:
1. Click “Capture Image” in the “Capture” Menu at the top to take a picture.
2. You can click the video window title to make the video window live again.
3. Click “Save as”, to name and save your pictures.
4. Help for the camera is on the desktop.
5. You can also take a movie if you want to tilt the stage to see when the drop runs
off.
To Measure the drop Angle
1. Start ImageJ program
2. Load an image into ImageJ
3. Use the angle tool to determine the tilt angle of the surface with the horizontal
axis (the angle of the line with the horizontal axis is displayed below the toolbar)
then use Image > Transform>Rotate to correct it (note positive angle rotate
clockwise).
4. Launch the plugin Drop Analysis Software (Drop Snake or LB-ADSA) to measure
the contact angle of your droplet.
5. For DropSnake:
a) Open the preferences menu by clicking the red heart . Make sure the
default preferences are chosen (see image at right).
b) Choose Add/move knot mode, ,
to place “knots: on the drop contour
(7-10 knots). Define the drop contour
starting at the left interface point going
along the drop contour until the right
interface point. Place the last knot a
little before the interface point and
double click anywhere on the image to
close the spline. Once the spline is
finalized, the knots positions can be adjusted by drag and drop.
c) Make sure the two contact angles are both similar, if one is opposite the other
adjust some points to get them similar.
d) First run the Fast Snake on this initialization spline to refine it
e) Move the cursor onto the picture window to see the red points that are the
refined curve.
6. If the red points of the fitted spline are a better fit to the curve, accept the curve by
pressing on : The blue points will be replaced by the red ones.
7. If the fitted spline is not good, either start again or adjust the blue knots positions
and run the fast snake on this spline using:
8. When the fast snake gives better points and you have accepted them use the full
snake method to fit the blue curve by pressing the snake button:
9. Contact angles are displayed in the image and in the table. Further information
such as the surface of the meridional plane, the contour length of the meridional
plane, the contact radius or the interface tilt angle are also available. The fitting or
evolving of the curve can be done a number of times to make sure it is stable. In
the preferences you and set the optimization to high and other parameters to try
and improve the fit.
10. If you want to fit another picture you must press the Quit DropSnake button, ,
(second to last button on right of button bar, has a microscope and a red left
arrow) before you load another figure.
Another way of initialization is to enable ”Place knots automatically” in the setting
menu, and to create a new curve. In this mode, the user must click at the position of
the first knot (left contact point) and then smoothly follow the drop contour until
the last knot (right contact point). A double click defines the position of the last
knot. You must not have points that are far off the surface of the drop or it will not
work. This method is harder to use than the placing on individual points and it
takes some skill to make it work well.
Contact angle is still a tricky parameter to measure and several parameters such as
dimensional parameters may influence its measure. Care should be taken when
modifying parameters from the setting men.
On the example drop if you use the automatically place points vs the hand placed
points you find that the contact angle differs by about 10º!
After analyzing one picture if you want to load a new picture you must push the
Quit DropSnake button before loading the new picture.
For help see drop analysis users guide.
Preferences panel:
a) External energy: Define the ratio of region energy and gradient energy. Region energy may have better converging properties, but gradient energy should be used to provide accurate detection.
b) Max iterations: Maximum number of iterations when evolving the snake. If reached an error message is displayed
c) Step size: Step size in the evolving process. If curve is oscillating, this should be reduced. If knot displacement is too small, this should be increased.
d) Accuracy on CA: Contact angle convergence criterium. The evolving process is terminated when change in the contact angle is within this range. Recommended: 0.01
e) Smoothing radius : Smoothing preprocessing realized on the image before the evolving procedure.
f) Eint/Eimage: Ratio of internal energy and image energy. Internal energy is responsible for the elastic component of the snake. Image energy allows the snake to stick on the image. Typical value [0.2 ... 0.5], Recommended: 0.3
g) Region method: Specify the statistical region method used. Means is recommended
h) Knot spacing at interface: Define the ideal distance between two knots at the interface. Typical value [10 ... 40], Recommended: 20. This can significantly affect the results.
i) Knot spacing ratio: Define the inter-knot distance ratio between knots at the interface and knots at the apex of the curve. This parameter allows to place more knots at the interface than on the rest of the drop. Typical value [1.0 ... 3.0], Recommended: 1.0
j) Sampling period at interface: Define the sampling period for the minimum knot distance. Best results should be obtained with a distance of 1 pixel. Increasing this value will allow an increase in speed but a loss in accuracy.
k) Animate evolution: Display knots during evolution. Faster when not displayed.
l) Symmetric snake: If set, the drop is defined with a symmetry between the first and last knot. The first and last knot are then evolved correspondingly. If not set, the first and last knots will be evolved horizontally only.
m) Image interpolation: When set, cubic spline image interpolation will be used. Important for accuracy.
n) Internal energy: Enable or disable internal energy. Internal energy is responsible for the elastic property of the snake.
Finish up
1. Exit the software.
2. Remove solvent from the syringe.
3. Clean the stage.
4. Unplug EM-500M Camera and put it back to the white camera box with the USB
cable and put in the drawer.
5. Put the eyepiece back to telescope.
6. Log off the computer.