Biomedical Engineering Reference
In-Depth Information
Kendall and colleagues have described how
they made Macro Defect-Free cement (MDF-
cement)
[61]
. They mixed the cement with a plas-
ticizer (a water-soluble polymer) that allowed
them to use less water and to more easily remove
trapped air cavities. The properties were signifi-
cantly improved, e.g., the compressive strength
improved by a factor of between two and seven.
According to Luz and Mano
[62]
, nacre inte-
grates well into bone tissue, and nacre analogs
therefore are potentially interesting for orthope-
dic and dental applications. They have described
strategies, including the ice-templating tech-
nique, for creating similar brick-and-mortar
structures. However, these structures do not
have the self-healing property that would be
desirable to ensure a long lifetime for the pros-
thetic device.
on the other hand, have the advantages of very
low administrative costs and robustness, since
there are no centralized command structures
that can be disturbed. However, the intended
goals of the decentralized system need to be
built in as emergent properties within the single
units of the self-organized system.
The principles for decentralized control can be
applied in a very wide array of activities in our
daily life: production and maintenance of prod-
ucts, computer programs, organization of service
systems, and organization of social structures. It
is therefore very relevant and interesting to study
how nature self-organizes and self-heals in order
to understand the core principles and mimic
them when we're designing manmade artefacts.
Since design processes are carried out in col-
laboration between experts from different disci-
plines, the communication of the core biomimetic
principles is a vital element in the transfer of
knowledge. Many of the self-organizing and
self-healing processes are well understood
within the biological community, but the knowl-
edge is not accessible in a form that is under-
standable and useful for design practitioners.
The aims of this chapter have therefore been
to collect information about eight phenomena
within self-organization and self-healing, to out-
line existing and possible applications within
the manmade world, and to describe the
simplified core principles for each of the phe-
nomena. To facilitate description, simple draw-
ings of the principles were included for the
phenomena. This way of communication and
documentation is appreciated among design
practitioners
[19]
.
The eight phenomena were selected based on
their remarkable and effective characteristics.
Section
13.2
discussed how the coordinated
movement of large groups can be inspired from
the way birds fly in flocks and fish swim in
schools. The basic principles within the two
natural phenomena are similar, since the indi-
vidual animals follow simple and local rules.
Basically, they move in the same direction as
13.10 DISCUSSION AND
PERSPECTIVES
In contrast to the human way of controlling,
producing, and repairing objects in a top-down
controlled manner, extensive use of decentral-
ized self-organization and self-healing occurs in
nature. It is attractive to adopt the principles and
methods from nature for manmade products
and the way we control the activities around us.
It is particularly recommended for micro- and
nanoproduction of delicate structures, which are
difficult to produce in a top-down way.
Another significant area is of the computer
software systems that control many objects and
activities. Controlling procedures are often
designed in a top-down hierarchical manner to
make sure that things happen the way they are
intended to and on time. The benefit of the top-
down control principle is the predictability, but
the downside is the administrative cost of non-
productive control resources and the vulnerabil-
ity of the system. In hierarchical control systems,
the strength is not better than that of the weakest
element. Decentralized self-organized systems,
