472 Prakt. Met. Sonderband 38 (2006)
aerospace, energy (solar power, wind power and atomic power plants) industry. Also
everyday experiences such as dirt adhering to clothes, chalk adhering to the
blackboard, ice adhering to different surfaces (and many more examples) show the
importance and universal nature of adhesion phenomena. Each case of adhesion is
unique and has to be studied separate.
On the other hand, adhesion is desired and even a prerequisit in manufacturing of
novel composit materials or adhesive joints. In those cases the strength of the bond
between the materials is to a great degree determined by the adhesive properties of
the surfaces.
1. MANUFACTURING ANTIADHESIVE METAL SURFACES &
BIOMIMETIC TRANSFER
There is not “one” or “a set” of standard antiadhesive surfaces to choose from, which
have been optimised throughout the history of technology and can therefore be used
in industrial implementations without further considerations. Development of
functional surfaces for technology has not taken place in an evolutionary manner i.e.
through constant development in an ever-changing environment. In biology the
situation is somewhat different since nature had more time to develop surfaces which
show multifunctional properties which can adopt themselves to the environment. A
well-known example of an antiadhesive (and also self-cleaning) biological surface is
the leaf of Nelumbo nucifera or the sacred Lotos [1]. The surface is covered with
selfassembled waxes which form a nanostructure upon the underlying micro structure
(cell wall structures and cuticular folds) thus exhibits a hierarchial topography [2,3,4]
(Figure 1). The wax components are hydrophobic and therefore repel water
excellently as a result of both hierarchial surface structure and the chemical
properties of the waxes.
Fig. 1: Nelumbo nucifera the Lotos plant (left), an SEM micrograph of a Lotos
leaf showing the hierarchial topography of nanosized selfassembled
hydrophobic waxes on an underlying microstructure (right).
Since both particles (“dirt”) and water do not adhere to (or wet) the surface the former
is easily removed by water droplets (self-cleaning) as shown in figure 2. The self-
cleaning ability as a result of the hierarchial topography and surface chemistry of the
leaf is often refered to as the Lotus-effect® and has led to the development of new
products such as facade paints [5]