Contact angle is a specialized skill that involves measuring the angle between the surface of a liquid and the surface it is in contact with. This can provide important information about the properties of the liquid and the surface, including their compatibility, adhesion, and wetting behavior. Understanding contact angle requires a background in materials science, surface chemistry, and physics, and the ability to use specialized equipment and techniques such as goniometry and image analysis. It is a valuable skill for researchers and engineers working in a variety of fields, including coatings, adhesives, biomaterials, and nanotechnology.