Controlling surface wettability is important for many applications like microfluidics, self-cleaning surfaces, anti-biofouling and more. Still, there are still not many methods available to switch such properties via a selective and quickly responsive trigger. Furthermore, the methods that have been reported lack either the stable, covalent attachment of the surface modification or do not change the surface chemistry drastically enough to obtain a switch between a superhydrophobic and nearly superhydrophilic state.

Prof. Pavel Levkin and colleagues from the Karlsruhe Institute of Technology in Germany have reported a technique that can reversibly switch the wettability of a surface through silanization. The method is based on the widely used silanization of surfaces, where the modification is attached via a very stable silicon–oxygen bond. Instead of oxygen, Levkin’s team used fluoride anions as a selective cleavage agent for these silicon–oxygen bonds. The process is performed in less than two minutes at room temperature. Furthermore, this methods can be spatially controlled via liquid dispensers or simple pens to spread the desilanization solution. By this, they combine the facile and established silanization for stable surface modification with a highly selective and fast cleaving agent to obtain the non-modified surface again.

The next steps will be the fine-tuning of surface wettability by kinetically controlled desilanization as well as the use of spatial desilanization for the production of superhydrophilic–superhydrophobic droplet microarrays. Potential applications include oil–water separation, self-cleaning surfaces, corrosion inhibition, and anti-biofouling. Furthermore, spatial control of surface wettability also allows for discontinuous dewetting and microfluidic applications.

“All in all, the presented method extends the toolbox of all the many surface scientists who work with silanes”, concludes the authors.

Reference: M. Brehm, et al. ‘Reversible Surface Wettability by Silanization.’ Advanced Materials Interfaces (2020). DOI: 10.1002/admi.201902134