Joninn - Contact angles

This App is used to measure contact angle from photos taken directly above a test droplet.

WORKING PRINCIPLE
This App uses a modified Bikerman method, to calculate the contact angle (CA) from the smartphone photo.
The Bikerman method is only suitable for hydrophilic and neutral surfaces.
- For CA less than 75° it works great.
- For CA between 75° and 85° it has limited accuracy.
- For CA above 85° it is unsuitable.

PHOTO TO BE ANALYZED
The Photo to be analyzed must be taken from directly above the droplet, and the photo must include a ruler with millimeter markings.
When taking the photo, you will get the highest accuracy of the calculated contact angle by ensuring that:
►The droplet should be at least 10% of the photo width.
►The contour of the droplet is in focus and has high contrast to the background.
►Adjust the light to avoid shadows and very bright spots in the photo.
►A single color background (such as a piece of paper) works best. Especially if the surface to be analyzed is transparent.
►If possible use a high contrast test liquid (such as our TL1).
►The ruler should be oriented horizontally or vertically in the photo. Get as close as possible to 0° or 90° orientation as possible.

CRITICAL REVIEW OF RESULTS
Due to the varying quality of the photos recorded, the measured contact angles shouldn’t be trusted blindly.
►You will get an indication of the accuracy of the measurement from the mean, minimum and maximum estimates of the CA on the results page. If these estimates differ significantly, then the accuracy will be poor.
►You will also get an indication of the accuracy of the measurement from the circles overlaid the photo. If these differ significantly from the actual droplet, then the accuracy will be poor.
If you often get poor results, then you must adjust the light conditions to give a higher quality photo.
►If either of the two circles are clearly off the droplet, you should only use the other result.
-The purple circle corresponds to MaxCA.
-The green circle corresponds to MinCA.

ABOUT
This App is made freely available by Joninn ApS, a company specialized in development, production and use of hydrophilic coatings. We have ready-to-ship hydrophilic coating products, and assist our customers on a consultancy basis to get their liquid handling device operational.
For detailed and updated information on this App please visit our web-site www.joninn.com