In this webinar we will demonstrate the superior nature of dynamic contact angle (CA) measurements for better understanding the wettability and related properties of a solid surface.
Static CA measurements, the most common method of CA measurements, are simple, practical, and provide values that are appropriate for calculations like the solid’s Surface Free Energy. However, it has been shown that the Static CA tends to be more difficult to reproduce, failing to a provide a reliable representation of the sample surface. This challenge can be overcome by instead measuring the ‘Advancing’ CA (ACA) on the surface.
Compared to a singular Static CA value, which represents one of many CAs near the so-called ‘Most Stable CA’ of a surface, the ACA represents the highest measurable CA across the sample surface and therefore tends to be more unique and reproducible for a given surface. The ACA is usually measured with the ‘Needle’ approach in which the CA of a droplet, that has already been placed on a surface, is monitored while the volume of the droplet is slowly increased via an inserted needle tip at the drop apex. In addition to the ACA measurement, the Needle method can also be used to measure the ‘Receding’ CA of the surface (by removing the droplet volume and monitoring the CA). The measurement of RCA can be used to understand the adhesion properties of the surface, its susceptibility to contamination, and the overall heterogeneity of the surface when subtracted from the ACA value (i.e., the ‘CA Hysteresis’ of the surface).
The combined ACA, RCA, and CA hysteresis results provide a powerful description of the solid surface that is more expansive and, in the case of ACA, more reproducible versus Static CA measurements.