Water - Biomaterials: A Tantalus Experience - page 299

purpose of this chapter was to incite interest in the often forgotten partner, a material
we cannot manipulate but one which is inevitably interfering with all materials we
want to shape to our convenience.

14.3 Conclusion

90 ı C; compare it with HCl

Considering its molecular weight, water should boil at

65 ı C. But water does not behave so. Becoming less dense

which is boiling at

C4 ı C is another anomaly. Fortunately should we say, because without that
density maximum, life on earth would be heavily compromised. Ice would sink to
the bottom, making the survival of higher order life in seas and ponds very unlikely.
Clays and water are intimate compagnons de route involved in the emergence of
life on earth: catalyzing the formation of peptides and, by adsorbing them on the
surface, preserving the newly formed peptides from prompt hydrolysis, the 'deep
freeze' function as we called it. And everything is linked to everything. The catal-
ysis by clays is due to interaction of the exchangeable cations on their surface
with adsorbed water, turning the clay into a solid acid catalyst. The position of
the exchangeable cations, which are in general essential plant nutrient elements as
sodium, potassium, calcium and so on, protect these cations from being eluted by
the first heavy rain, as would be the case, when soils consisted of nothing but quartz
sand. Were clay and water compagnons de route during the emergence of life, their
ion exchange capacity makes them companions for sustaining life on earth. Is not
that beautiful!
The interaction of water with hydrophilic or hydrophobic surfaces is for a
substantial part undoubtedly responsible for their behavior as a biomaterial. Under-
standing these interactions remains difficult. However large-scale the research effort
has been, there is no means of systematically categorising or naming different sur-
faces based on measurable wetting properties as Vogler concludes its chapter on
wetting biomaterials surfaces [ 470 ]. A crushing statement, so a handbook version
on the theory of water and surfaces is clearly not yet for tomorrow.
Andbytheway...thischapterhasbeenwritten when the Olympic Winter Games
were going on in Vancouver. Skating is a nice present of water physics: a spe-
cial surface layer reduces the friction coefficient to such an extent that 75% of the
skater's energy spending is due to air resistance and only 25% to the contact of
skates with ice.

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