Foam structures: organa-silica sol-gel foam

A droplet on top of a foam block
A droplet on top of a foam block

A common approach to creating super water-repellent surfaces is to make a rough structure and then coat it with a hydrophobic surface chemistry. If the surface is rubbed or abraded, the effect is worn away as the coating with the surface chemistry is removed. In the sol-gel technique, a foam is produced by a phase separation method and by varying the solution properties, the pore sizes can be controlled. If the foam is produced using MTEOS (methyltriethoxysilane) then all the pores have hydrophobic surfaces.

When this foam is abraded the surface is naturally superhydrophobic. If it becomes dirty, and loses its super water-repellency, abrading it renews the surface and recreates the superhydrophobicity. Read more about the process in the publication below.

Publication

  • Intrinsically super hydrophobic organo-silica sol-gel foams.
    N.J. Shirtcliffe, G. McHale, C.C. Perry and M.I. Newton.
    Langmuir 19 (14) (2003) 5626-5631.

Additional reading

  • Porous materials show superhydrophobic to superhydrophilic switching.
    N.J. Shirtcliffe, G. McHale, M.I. Newton, C.C. Perry and P/ Roach
    Chem. Comm. 25 (2005) 3135-3137.
  • Superhydrophobic to superhydrophilic transitions of sol-gel films for temperature, alcohol or surfactant measurement.
    N.J. Shirtcliffe, G. McHale, M.I. Newton, C.C. Perry and P/ Roach
    Maters. Chem. & Phys. 103 (1) (2007) 112-117.