Interfacial tension and interfacial rheology measurements can inform on an enormous number of liquid and solid phenomena and processes, such as:
- Foam and emulsion formation
- Foam and emulsion stability
- Wettability and the dynamic wetting of surfaces
- Atomization and droplet formation
- Flow in microfluidic and lab-on-a-chip devices
- Drainage characteristics
- Penetration and absorption processes
Drop shape analysis takes two approaches:
Pendant drop analysis measures the shape of a liquid drop suspended from the end of a tube in air or a lower density liquid. The shape of the hanging drop of liquid is the result of the competing forces of gravity, trying to pull the drop into a pear shape, and surface tension, trying to maintain a sphere. By analysis of the resulting drop shape surface tension and interfacial tension can be calculated.
Dynamic contact angle measurement methods
Dynamic Wetting Measurement
Wetting is the result effect of the adhesive forces between a solid surface and a liquid drop, and the cohesive forces within the liquid drop. Strong liquid-solid surface cohesive forces minimise the contact angle, while stronger liquid-liquid adhesive forces lead to an increased contact angle. The dynamic wetting measurement can be recorded using high speed imaging to capture the contact angle at rapid intervals subsequent to the placing of a drop. This can inform on rapid adsorption of surface active entities or on situations where significant interaction, either chemical or physical, with a surface may occur. The main commercial applications of this technique are:
- Determining surface functionality.
- Development of self-cleansing films, fabrics and glass surfaces.
- Measuring the spreading rate of various liquids on a surface.