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This page gives instructions on how to use your cell phone to take contact angle measurements.

Experimental Instructions[edit | edit source]

  1. Put your sample on a flat substrate
  2. Use a micropipette to deposit a small droplet of fluid on the sample
  3. Take a picture of the droplet from the side of the substrate as shown in Figure below. Make sure the image is in focus and not blurry.

Software analysis[edit | edit source]

  1. Install the open source imageJ plugin for contact angle measurements: https://imagej.nih.gov/ij/plugins/contact-angle.html
  2. Open imageJ and check to see if "Contant Angle" is available under the "Plugins" tab and select it.
  3. Open the image.
  4. Select the two end points of the droplet where it meets the substrate using the "drop points" button (shown in red).
  5. Select 5 points along the droplet surface and allow imageJ to run the fitting algorithm (shown in blue).
  6. Click on the Menu button in the Contact Angle plugin toolbar.
  7. Click Manual Points Procedure.
  8. Open the results window to see the contact angle for a spherical approximation and also for elliptical approximation.

CellphoneCA.PNG

Drawbacks[edit | edit source]

  1. This will not work if the substrate is not absolutely flat. The program needs to be able to draw a straight line that follows the surface of the substrate exactly after the user selects the two end points of the droplet.
  2. Uses either a spherical or an elliptical approximation for the droplet. The user needs to be able to pick manually which approximation works better for their case.
  3. The drop has to be very very small (ideally <3ul). The program neglects gravity.

For more information[edit | edit source]

1. ResearchGate example

2. Youtube tutorial