Superhydrophobic Surfaces Produced by Supercritical Fluid Technology

Supercritical carbon dioxide (scCO2) is a non-toxic, easily recyclable fluid of low environmental impact. Superhydrophobic self-cleaning surfaces have been produced by dissolving hydrophobic compounds in scCO2, followed by spraying the solution through a pressure nozzle employing the rapid expansion of supercritical solution (RESS) technique [1-3]. Research has been conducted on the effect of different pre-expansion pressure and temperature as well as distance between the nozzle and the treated surface, with regard to particle morphology and size distribution. Laser diffraction measurements have been conducted directly perpendicularly to the spraying cone from the RESS system, providing information about the particle size distribution as a function of spraying distance. Larger particles/agglomerates (10 – 25 mm) were produced at larger spraying distance, whereas smaller particles (ca. 3 mm) more homogeneously covering the surface were formed at shorter distance. Finally, results regarding solubility determination of waxes and polymers in scCO2 will be described in the presentation, as well as some alternative supercritical fluid techniques for producing superhydrophobic surfaces.

1.     C. Quan, O. Werner, L. Wagberg and C. Turner, Generation of superhydrophobic paper surfaces by a rapidly expanding supercritical carbon dioxide-alkyl ketene dimer solution, J. Supercrit. Fluids, 2009 (49) 117-124.

2.     O. Werner, C. Quan, C. Turner, B. Pettersson, L. Wagberg, Properties of superhydrophobic paper treated with rapid expansion of supercritical CO2 containing a crystallizing wax, Cellulose, 2010 (17) 187-198.

3.     International patent application, WO 2009/0054465, O. Werner, C. Quan, C. Turner, L. Wagberg and J.-C. Eriksson, "Method to prepare superhydrophobic surfaces on solid bodies by rapid expansion solutions".