kontaktangle

The contact angle is a fundamental property in surface science that quant erity characterizes the interaction between a liquid and a solid surface. It is defined as the angle formed by the tangent to the liquid-solid interface at the point of contact with the solid surface. This angle is measured within the liquid phase. The contact angle is a direct measure of the wettability of a solid surface by a given liquid.

A small contact angle, typically less than 90 degrees, indicates that the liquid spreads out on the surface, signifying good wettability. This is often observed when the adhesive forces between the liquid molecules and the solid surface are stronger than the cohesive forces within the liquid. Conversely, a large contact angle, greater than 90 degrees, suggests that the liquid beads up on the surface, indicating poor wettability. In this scenario, the cohesive forces within the liquid are dominant. A contact angle of exactly 90 degrees represents a balance between adhesive and cohesive forces.

The contact angle is influenced by several factors, including the surface energy of the solid, the surface tension of the liquid, the presence of contaminants on the surface, and the roughness of the solid. It is a crucial parameter in various applications, such as printing, painting, coating, adhesion, and microfluidics, where controlling the interaction between liquids and surfaces is essential for performance. Techniques like goniometry are commonly used to measure contact angles accurately.