Contact angle measurements: From existing methods to an open-source tool

Contact angle measurement is an effective way to investigate solid surface properties. The introduction of low-cost digital cameras, as well as software and libraries for image analysis, has made contact angle measurement potentially accessible to every laboratory. In this review, we provide a comparison of the main methods developed to evaluate contact angle from digital images, including the so-called Young-Laplace method, the circle and polynomial fittings, as well as the mask method. All methods have been implemented and compared analyzing virtual and real drop images in an open-source software, Dropen, developed as an app in MATLAB environment. The code enables single image analysis evaluation, for the robust automatic identification of the contact points and contact angle evaluation, with the goal of minimizing user inputs, automatizing the process and facilitating measurements for all users, from less experienced to advanced wetting experts. Dropen and its code are made available at BOA, the Bicocca Open Access public repository, for use and further development.

Automated summary

Contact angle measurement is an effective way to investigate solid surface properties, and the development of low-cost digital cameras and software has made this method potentially accessible to every laboratory. Various methods for evaluating contact angle from digital images have been compared and implemented in the open-source software Dropen, aiming to minimize user inputs and automate the process for all users. Dropen and its code are available for use and further development in the Bicocca Open Access public repository.