Superhydrophobicity

Superhydrophobic

=Super + hydro + phobic

water

dislike

Superhydrophilic

Most abundant atom in the Earth

#Ocean - O(85.8%) > H(10.8%) > Cl(1.9%) > Na(1.1%) > Mg(0.13%) 

#Crust - O(46%) > Si(28%) > Al (8.2%) > Fe (5.6%) > Ca(4.15%) > Na(2.36%) > Mg(2.33%) > K(2.09%) > Ti(0.565%) > H(0.14%)

Molecular number: O(60.3%) > Si(20.8%) > Al(6.4%) > H(2.92%) > Ca(2.16%) > Na(2.15%) > Fe(2.09%) > Mg(2.00%) > K(1.12%) > Ti(0.06%)

The Earth - 71% of surface covered by water.

Total 1,386M km³ on the earth.

Human body - composed of 60% of water

Surface tension

van Oss-Chaudhury-Good Theory

“Like likes like,” “Like dissolves like.”

in mJ/m

Roughness on the surface

What happens when the surface has the roughness?

Wenzel VS Cassie-Baxter

Cassie-Baxter

Wenzel

Superhydrophilic

R

0^o

180^o

180^o

0^o

Local contact equilibrium

Gibbs free energy from Wenzel to Cassie

Perfect surface pattern for superhydrophobic?

Capillary(wicking) vs superhydrophobic

-Particle is making roughness

-need adhesion layer

-can influence optic

Gore-tex

PTFE

polytetrafluoroethylene

Property

-Water-proof (non wet)

-Breathable (~5000g/m2/day)

-expanded PTFE

Expanded PTFE

Gore-tex medical

Artificial vascular grafts