Research and applications of superhydrophobicity and superamphiphobicity has increased ever since Wenzel and Cassie-Baxter wetting types were presented and especially since the water superrepellency of the lotus leaf was observed. Applications are exemplified (1) but also potential drawbacks in their usage (2). Basic understanding of the non-wetting mechanisms comes from theoretical work (3, 4) and from surface force measurements, using either droplets or particle probes (5,6). We report surface force (AFM colloidal probe microscopy) measurements combined with confocal laser microscopy imaging (CLSM) (7-9) allowing long-range capillary forces to be measured at the same time as the growing gaseous capillary is imaged. The different contributions to Gibbs free energy of capillary formation from the works of surface tension-area and pressure-volume were discerned, as well as a remaining term for the three-phase contact line (TPCL) contributions (pinning, depinning and line energy). We discuss a remaining challenge to more correctly determine the TPCL contributions, e.g. the line path (10). Superhydrophobicity and superamphiphobicity is most often described as a surface having a liquid contact angle of above 150° and a low roll-off contact angle. Studies suggest that there are several phenomena occurring with a transition from force curves of constant pressure or volume to those showing both non-constant pressure and volume of the gas capillary. This wetting transition can be used to define the super liquid-repellency from a surface forces point of view.

Acknowledgements to colleagues at Max Planck institute in Mainz, Omya Development AG, Tampere

University and RISE; to SSF Swedish Foundation for Strategic Research and Pro2BE academic environment at Karlstad University.

References

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