Surface Wettability

To alter surface wettability

When a solid surface comes in contact with a liquid, the complex effects of the surface morphology (roughness), its chemical composition and the short- and long-ranged intermolecular forces developing with the liquid (van der Waals’ forces, hydrogen polar bonding, electrostatic attractions with lone electrons pairs, etc…) determine an equilibrium condition in which the surface may or may not be wetted by the liquid, depending on how much favorable the interactions between the two are.

Different kinds of interactions between the two interfaces determine the shape of the liquid droplet and the resulting contact angle. (c)
Different kinds of interactions between the two interfaces determine the shape of the liquid droplet and the resulting contact angle.
Carbon sheet (hydrophilic) with fluorinated surface groups: the sheet becomes hydrophobic and the water droplets sit on it, ready to roll off the surface. (c)
Carbon sheet (hydrophilic) with fluorinated surface groups: the sheet becomes hydrophobic and the water droplets sit on it, ready to roll off the surface.

To alter surface wettability

Plasma treatment, both at atmospheric and low pressure, can be readily employed for such purposes: depending on the chosen gas feeding the plasma, it is in fact possible to selectively graft functional groups that can either increase or decrease the wettability of a wide choice of substrates, including commercially widespread polymers like plastics.

The ability to alter surface wettability finds countless applications, ranging from microfluidics and lab-on-chip devices, where it can be used to separate blood components, biomedical engineering, as it can promote or discourage the growth of living cells on a surface, and so on. Even extreme behaviors like superhydrophilicity and superhydrophobicity are finding increasingly wider application: the former can prevent haziness on a wet transparent surface (‘anti-fogging’), while the latter can be used for self-cleaning surfaces, on which water droplets roll off, taking dirt and dust particles away.

 

Mariagrazia Troia M. Sc.

Ph. D. Student, Plasma Technology

Matthias Walker
Dr.-Ing.

Matthias Walker

Head of Administration / Head of Plasma Technology

To the top of the page