In situ error analysis in contact angle goniometry

Contact angle goniometry is a valuable tool for characterising surface wetting properties in various application areas such as petrochemistry, coatings, and medicine. The accuracy of goniometer measurements is often unknown and underappreciated, yet the errors can be large enough to affect or invalidate the interpretation of measurement. In addition, goniometer measurement errors are typically estimated after the measurement by the variance of the measured data, without considering the instrumental uncertainties in the analysis or in the setup. Here, we present a method for estimating these intrinsic measurement errors for each frame in situ and validate it against a commercial contact angle goniometer. We evaluate the method using synthetic images of a droplet with set contact angles. Our results highlight the need for in situ error estimates in goniometer measurements, as the errors can be larger than generally estimated ones. The presented in situ error estimation method could be implemented using contact angle goniometer software to aid the user during the tuning of the instrument and analysis of the contact angle data.