Environmental Engineering Reference
In-Depth Information
assembled
with
an
impressive
precision,
from
the
nano
and
micro
to
the
macroscale.
Resource efficiency. In Nature, resources are limited and transportation is
expensive. For this reason, living organisms live in close balance with the sur-
rounding environment. The local environment is the source of elements, not only
for the organisms that live there, but also for their offspring. For this reason,
bioprocesses have been perfected by natural selection to maximize efficiency and
reduce vital losses along the metabolic routes. Moreover, Nature uses cyclic
processes, ensuring that each element is returned to its original form, ready to be
used again. Nature found a way to recycle every biomaterial, reduce the waste
generation and the impact of organisms on the environment, and constantly feed
the cycle of the elements.
3.3 Development of Biomimetic Materials
3.3.1 Mechanical Properties
Despite their attractive properties, the application of highly mineralized materials
such as ceramics and glasses in man-made products used in construction is often
limited by their characteristic brittleness. In nature, however, the incorporation of a
small percentage of biomolecules and a controlled nano-, micro- and meso-
hierarchical architecture of the building blocks originates materials that are both
flexible and robust, providing organisms with an ability to manage impact and
shock in the most varied circumstances (Mirkhalaf et al.
2014
). In these materials,
structural, elastomeric biomolecules such as proteins and polysaccharides con-
tribute to improve the robustness of mineral components which are characteristi-
cally harder, but more fragile. This combination yields natural composites that
present both strength and toughness several orders of magnitude above the ones
displayed by pure minerals (Barthelat
2007
). Examples of natural ceramic com-
posites that have been the subject of study range from nacre (Corni et al.
2012
) and
bone (Launey et al.
2010
), to bird eggshells (Freeman et al.
2010
), sponge spicules
(Meyers
2008
) and the armored skins of crocodiles, armadillo, turtles, and fish
(Zimmermann et al.
2013
; Chintapalli et al.
2014
). Natural biopolymers (e.g., silk)
and cellular matrices (e.g., wood, bamboo) also present properties, which result
from nano-, micro- and meso-structures that are worth replicating into materials
used to withstand mechanical loads. A few examples are briefly described next that
are especially relevant for the development of new construction materials (e.g.,
glasses, protective coatings, tiles, etc).
Nacre. In order to protect mollusks from predators and water-carried debris, the
shells of organisms like the abalone or oysters have evolved into a stiff and impact
resistant material named nacre or mother of pearl (Corni et al.
2012
). The struc-
turing of alternating aragonite (an orthorhombic crystal form of calcium carbonate)
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