A low-cost goniometer for contact angle measurements using drop image analysis: Development and validation

Contact angle measurements are a widely used method for evaluating surface wettability, but their accessibility is limited by the high cost of commercial goniometers. To address this issue, we developed a low-cost prototype goniometer using locally available materials and a smartphone-based image analysis system to measure contact angles. We validated our approach by comparing its results with those of a standard goniometer for both organic and inorganic materials. For organic samples, the accuracy is greater than 86%, and for inorganic samples, it is greater than 94%. The good agreement between the two methods demonstrates the feasibility of our proposed method for accurate contact angle measurements at a lower cost.