of nanoscale components and which
are able to perform simple tasks at the
nano-level. Going one step ahead, we
propose the interconnection of nano-machines in a network or nanonetwork
as the way to overcome the limitations
of individual nano-devices.
1, 2 The potential applications of the resulting
nanonetworks are almost unlimited
and can be classified in four main
areas: Biomedical Applications (for example, intrabody health monitoring
and drug delivery systems, immune
system support mechanisms, and artificial bio-hybrid implants);
Industrial and Consumer Goods Applications
(for example, development of intelligent functionalized materials and
fabrics, new manufacturing processes
and distributed quality control procedures, food and water quality control
systems); Environmental Applications
(biological and chemical nanosensor
networks for pollution control, bio-degradation assistance, and animal
and biodiversity control); and Military
Applications (nuclear, biological and
chemical defenses and nano-func-tionalized equipment).
Several communication paradigms
can be used in nanonetworks depend-
ing on the technology used to manu-
facture the nanomachines and the tar-
geted application. In this article, we
provide an overview of the two main
alternatives for nanocommunication,
that is, Electromagnetic Communica-
tions in the Terahertz Band and Mo-
lecular Communications. Our aim
is to provide a better understanding
of the current research issues in this
truly interdisciplinary and emerging
field, and to pave the way of future re-
search in nanonetworks. We also re-
view the state of the art in the design
and manufacturing of nanomachines,
discuss the different alternatives for
communication in the nanoscale, and
describe the research challenges in
the design of protocols for nanonet-
works. While there is still a long way
to go before a fully functional nano-
machine is realized, we believe hard-
ware-oriented research and commu-
nication-focused investigations will
benefit from being conducted in par-
allel from an early stage.
manufacturing Nanomachines
Nanonetworks start at the interconnection of several nanomachines.
The capabilities and the application range of these nanomachines
strongly depend on the way in which
they are manufactured. As shown in
the accompanying figure, different
approaches can be used for their development, ranging from the use of
man-made components to the reuse
of biological entities found in nature.
These approaches are classified into
three main branches, namely, top-down, bottom up and bio-hybrid.
1
In the top-down approach, nanomachines are developed by means of
downscaling current microelectronic
and micro-electro-mechanical technologies without atomic level control. In the bottom-up approach, the
design of nano-machines is realized
from the (self) assembly of molecular components and synthesized
approaches for the development of nanomachines.
nature
Insects
Cells bacteria
Top-down
microelectronics
molecules atoms
man-made
microsensors
mems
nems
nanomaterials. Alternatively, in a
bio-hybrid approach, existing biological
components, such as Deoxyribonucleic Acid or DNA strands, antibodies or
molecular motors, are combined with
man-made nano-structures to develop
new nanomachines.
Man-made machines. Despite
several technological and physical
limitations, the evolution of classical lithography techniques and other
non-standard manufacturing procedures have been used to fabricate
components with at least one of their
dimensions in a scale below 100nm.
16
A special emphasis should be given to
the study of nanomaterials and new
manufacturing processes, which are
enabling a new direction for the development of nano-components. As
an example, field-effect transistors
can be obtained through the use of
graphene nanoribbons and carbon
nanotubes, and these can be used as
the building block for new computing machines.
14 Other well-studied
nano-components are nanomaterials-based biological, chemical, and physical nanosensors and nanoactuators.
The integration of several of these
nano-components into a single functional unit will result in a device with
a total size in between 10− 100 square
micrometers,
2 which is comparable
to the size of an average human cell.
However, the integration of these
components into a single device is
still one of the major challenges in the
manufacturing of nanomachines.
Adopting components coming
from nature. The nanoscale is the
natural domain of molecules, proteins, DNA, organelles and the major
components of cells. Some of these
nano-components can be used as
building blocks for integrated nano-devices. As an example, Adenosine
TriPhosphate or ATP batteries emulating the behavior of mitochondria,
often described as “cellular power
plants,” can be an alternative energy
source for bio-nano-devices. In addition, information encoded in DNA
can be used for molecular computing
machines and molecular memories.
Alternatively, DNA strands can also be
used to build miniature circuit boards
and to stimulate the self-assembly of
components such as carbon nanotubes, nanowires, nanoribbons and
