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.