Switchable Thin Film Wettability

The aim of this project is to switch the wettability of a surface from hydrophobic to hydrophilic with light.

It is well-known that the wettability of a thin film is determined by the surface structure as well as the inherent material wettability. Increased surface roughness tends to enhance both hydrophilicity and hydrophobicity, with contact angles diverging away from 90° in either case [1,2]. The aim of this project is to combine substrate surfaces of controlled, nanoscale roughness with a monolayer coating of photoswitchable wettability [3] to enhance the change in contact angle between the two states.

Ultimately, a surface whose wettability can be tuned locally, reversibly and in situ between hydrophilic and superhydrophobic states could form the basis of open-substrate microfluidics, without the need for pre-formed microchannels to direct flow.

Techniques employed in this project include electropolymerisation, electrodeposition, evaporation deposition, scanning electron microscopy, monolayer self-assembly and contact angle goniometry.


[1] Cassie and Baxter, ‘Wettability of Porous Surfaces’, Trans Faraday Soc, 40 546 (1944)

[2] Wenzel, ‘Resistance of Solid Surfaces to Wetting by Water’, Ind Eng Chem, 28 988 (1936)

[3] Tian et al., ‘Orthogonal switching of a single supramolecular complex’, Nature Communications, 3 1207 (2012)

Involved people

Adolphe Merkle Institute - Chemin des Verdiers 4 - CH-1700 Fribourg - Phone +41 26 300 9254