An international team of researchers has announced a new approach offering better accuracy and reliability of contact angle measurements on wetting surfaces.
The proposed, standardized approach is an outcome of a study conducted by scientists from Finland’s Aalto University and China’s Sun Yat-sen University.
According to the researchers, understanding how surface materials interact with liquids is crucial to everything from printing to recovering oil spills from water.
This calls for an accurate and detailed analysis pertaining to wetting which deals with how a liquid adheres to, or slides off a given surface material.
To their credit, the researchers have come up with a new way to obtain reliable data, allowing comparison between research groups to promote the development of new wetting materials.
According to experts, the most common way to study wetting is by measuring the shape of a droplet – an approach originally developed by Thomas Young in 1805.
It deals with measuring in particular the contact angle between a solid surface and a drop of liquid, as they come into contact.
A low contact angle means the liquid will spread and adhere to the surface; a high contact angle, in contrast, means that the surface will repel the liquid.
The Finnish-Chinese team contends that contact angle measurement seems deceivingly simple to carry out, but it is demanding for researchers to obtain meaningful and reliable data.
Accordingly, real surfaces cannot be properly described by a single value of a static contact angle, save perhaps cases where the solid is atomically smooth and free of chemical impurities.
The actual conditions for which materials are designed rarely meet such requirements, they assert.
‘What we need to do instead is to measure a pair of advancing and receding contact angles of a droplet that grows and shrinks on a surface. Many publications on wetting, however, still report only a single value of a static contact angle, and therefore lack accuracy and reliability when explaining how the liquid actually behaves on the surface,’ said Tommi Huhtamäki, a doctoral student and principal author of the work.
Image and content: Mika Latikka/Robin Ras/Aalto University