As my research group began to enter into the world of precision cleaning, we needed to come up to speed on contact angle measurement. In doing so, we met Anselm Kuhn who was a great help and mentor. Together, we produced an inexpensive way to standardize contact angle measurements using spherical ruby lenses. We also evaluated the many freely-available contact angle measurement programs that act as plugins for ImageJ. This work was published in the German metal finishing journal Galvanotechnik.
Measurement of contact angles often provides valuable information as to the cleanliness of a surface as well as the ease of wetting of a surface with a coating such as paint or other organic species. Previous methods based on use of a sessile drop were subject to considerable operator error. In order to minimise such errors, the computer-based analysis of drop shape has been developed. The use of such software which is Windows-compatible and easy to learn, is described, giving results where operator-error is minimized. The method has considerable potential for Quality Control in surface finishing.
After this work we went on to explore simple methods to implement contact angle on the production floor rather than in the quality assurance lab. This led to the exploration of measuring contact angle with cell phones.
Using the Bikerman equation, the contact angle of a sessile drop can be measured from above. For a known drop volume, the contact angle can be derived from a measurement of the drop diameter. It is shown how this method can be implemented with many currently-available cellphone models. Increased accuracy can be achieved using low-cost close-up lenses and the image can be transmitted to a laptop for subsequent processing. This rapid and straightforward method makes the measurement of contact angles on the shopfloor or in the field, a more attractive proposition.
These papers will get you started if you are new to contact angle measurement. And this next thesis will assist you if you are interested in producing practice objects or standard reference materials for calibrating your technique in measuring contact angles.
Cleanliness Verification on Large Surfaces – Instilling Confidence in Contact Angle Techniques
December 2013, DOI: 10.1016/B978-1-4377-7879-3.00005-4, In book: Developments in Surface Contamination and Cleaning – Chapter: 5 – Publisher: Elsevier / William Andrew Editors: R. Kohli, K. L. Mittal
Darren L. Williams and Trisha M. O’Bryon
The sessile drop contact angle measurement is a useful and reliable method for surface energy determination and cleanliness verification. A review of the available methods, commercial instruments, patents, and literature describing the state of the art in contact angle measurement is followed by a description of contact angle measurement techniques that have been modified for use on large surfaces. The negative effects of these changes on accuracy and precision are discussed, and remedies are proposed including the use of standard reference objects that mimic the size and shape of sessile drops. The combination of these validation tools and the modified contact angle measuring techniques fills a need for robust, production-line capable cleanliness verification methods.