Description:

 

The lotus effect is named after the plant of the same name.  Two properties are characteristic of this effect: superhydrophobicity and self-cleaning. Superhydrophobicity is manifested by extreme water-repellence. Droplets of water on a slightly sloping superhydrophobic surface bead up and roll off without a trace. 

Structured surfaces displaying microroughness or nanoroughness are significantly more hydrophobic than smooth surfaces. Contact angles of up to 170 degrees are possible. The crux is to minimize the area of contact between the water and solid. In the lotus plant the actual contact area is only two to three percent of the droplet-covered surface. Minimization of contact area also reduces adhesion forces and the drops of water assume a spherical form. At the slightest slant, a breath of wind causes the droplets of water to roll off the surface, picking up particles of dirt (soot and dust) as they go.

BASF is working on the development of superhydrophobic materials and coatings by cleverly combining nanoparticles with hydrophobic polymers such as polypropylene, polyethylene and technical waxes. One outcome of these development efforts is a lotus-effect aerosol spray, which is very easy to apply. The nanostructure of the spray develops by a self-organization process during drying.

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