Liquids come in contact with solid surfaces in a variety of applications, including everyday situations like painting a wall or using medicine. In industry, wettability is important for example when manufacturing electronics or when planning how to extract oil from the oil reservoir. In all these applications, knowing the contact angle value gives a strong indication on the performance of the product or a successfulness of the process.
When a drop of water is placed on a solid, it will spread on the surface based on the intermolecular interactions between the solid and the liquid. Water contact angle will immediately give an indication of the wettability of the solid. If the measured contact angle is above 90 degrees, the solid is said to have poor wetting and is termed hydrophobic. If the contact angle is below 90 degrees, a term hydrophilic is used. As extreme cases, the water can either spread completely or form a sphere on top of the solid, in these cases terms complete wetting and superhydrophobic surfaces are used, respectively.
Coatings are used for both decorative and protective purposes. Whenever coating is applied on the solid, the spreading of the coating will have a big impact on the adhesion. Good wetting is generally related to good adhesion. Wettability of the surface can be improved by various surface treatments such as plasma or corona treatment. Different types of adhesion layers are also often utilized. To determine the good-enough level for the surface treatment, contact angle measurements are used.
To read more how contact angles are used in industries, download the overview below.
Fiber contact angles can be measured with several different methods
Characterization of superhydrophilic surfaces is commonly done with contact angle measurements.
Contact angle provides insights into the wettability and adhesion properties of cosmetic ingredients and formulations.
Contact angles on small areas can be easily measured.
Dispensing low surface tension liquids sets requirements for the tip material
One of the major factors limiting the analysis of contact angles is the accurate assignment of the baseline.
The earliest known reference to contact angle measurement was made by Thomas Young in 1805.
Chemical etching of fluoropolymers is a process used to selectively remove material from the surface using chemical solutions to improve wettability.
This difference in wettability is key in determining how each membrane is used.