Contact Angle Meter : Kyowa Interface Science

The contact angle is an easy way to measure the wettability of a solid substrate by a liquid. The liquid will form a drop shape when deposited onto a solid substrate. The point where the solid, the liquid, and the vapor meet is called the three-phase point, and it determines the contact angle. The contact angle is also an indicator of wettability, which depends on the combination of the solid substrate, the liquid, and the environment.

The relationship between the contact angle, the solid surface free energy, the liquid surface tension, and the interfacial tension between solid and liquid is defined by Young's equation:

In general, the following rule applies: The larger the contact angle the worse the wettability, the lower the contact angle the better the wettability.