Wilhelmy balance—A simple and reliable method for determining immersion angles and surface energies even on non-planar and complex geometries?

Abstract

The growing significance of surface properties in modern materials, particularly in medical technology, drives the need for accurate characterization techniques. Traditional contact angle measurements face challenges when applied to intricate surfaces like dental implants. Here, tensiometry applying the Wilhelmy plate method has been described in the last decade to offer one solution for the evaluation of complex surface geometries by quantifying apparent contact angles based on wetting forces. This study evaluates a simple setup employing the Wilhelmy balance concept for immersion angle determination. Instead of using a force sensor as in tensiometers, the wetting force is determined via changes in mass signal by means of an analytical balance available in standard laboratories. The force is thus recorded inverse to conventional tensiometry. The approach was validated on diverse geometries and extended to intricate structures, including plasma-treated dental implants. Results were compared to conventional contact angle analysis systems underlining the reliability of the method in characterizing non-planar and complex surfaces. Additionally, the method was successfully extended to the evaluation of surface energies on planar and non-planar surfaces using various solvent sets. However, results evidenced that specimen geometry can influence the measurements to such an extent that immersion contact angles can no longer be calculated due to capillary effects. An outlook suggests further exploration with a wider range of test liquids to enhance accuracy in surface energy determination.