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| Roger Bagula... |
 Posted: Sat Oct 03, 2009 4:35 am |
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Fractals in Nano-Devices
Professor Richard Taylor, Department of Physics, University of Oregon
Corresponding author: rpt at (no spam) oregon.edu
Future nano-devices are expected to underpin many of the technologies
that society relies on, ranging from household electronics to medical
implants. One of the great challenges of bringing this promising
future into reality lies in developing practical methods for
constructing these highly intricate structures: How will we assemble
electronic circuits that feature many more components than today's
commercial circuits and where each component approaches the atomic
scale?
Fractal is a rough or fragmented geometric shape that can be
subdivided in parts, each of which is (at least approximately) a
reduced-size copy of the whole.
'Self-assembly' holds great promise as a technique for building
commercial nano-circuits. Adopting this approach, the nano-engineer
allows the circuit to build itself by exploiting natural growth
processes. Self-assembly offers two striking advantages. Not only is
it more efficient at assembling vast numbers of components compared to
traditional fabrication techniques, this fundamentally 'green'
technique constructs circuits by the addition of material rather than
the wasteful removal of material that lies at the heart of previous
'top-down' fabrication techniques.
One of the remarkable consequences of harnessing natural growth
processes is that the resulting circuits exhibit natural patterns
rather than the smooth, straight lines that form the framework of
today's commercial circuit designs. In particular, many self-assembly
processes generate fractal patterns. Fractals are shapes that repeat
at many magnifications and are prevalent throughout nature, appearing
in natural environments1, biological systems and human physiology2.
Computers modeled on the brain's fractal geometry could possess large
circuit connectivity and the associated computing power
Nature uses fractals frequently because they possess a number of
highly desirable properties. Topping this list is the fact that the
repeating shapes build objects with huge surface areas. Nature
exploits this property for example in trees, where the large surface
area of the tree canopy ensures an unprecedented ability to absorb
sunlight. The same approach could equally be employed to great effect
by designing novel solar cell structures based on fractal shapes.
Solar cells modeled on a tree's fractal geometry could capture vast
amounts of sunlight
Another consequence of large surface areas is that two merging
patterns connect together very efficiently. For example, the dendritic
structure of the neurons in the human brain exploits this fractal
connectivity to produce enhanced information processing. The same
connectivity could equally be exploited for future commercial
computers by using artificial fractal electrical circuits.
Simulation of the self-assembled fractal electronic circuits
This philosophy of learning from nature's successes may well
revolutionize many fields within nanotechnology. Although some
electronics applications already exploit fractal geometry (cell phone
antennae being a famous example), many fields lie at the start of this
exciting journey, with many discoveries and challenges lying ahead.
Prof. Taylor's investigations focuses on two families of electronic
device in which millions of metallic nano-particles (each
approximately 50 nanometers across) are self-assembled into fractal
circuits. In the first family of device, the particles merge together
to form 'nanoflowers'3 using a growth process called diffusion-limited
aggregation. In the second family, the nano-particles are attached to
DNA strands4 which assemble to form a fractal circuit. In both cases,
the self-assembly process generates a tree-like pattern similar to one
shown in the illustration.
These projects are driven by the potential to tune the growth
conditions so that the fractal characteristics of the circuits match
those found for example in the neural structure of the human brain.
Imagine a future where computers operate like our own minds and,
ultimately, where fractal circuits may act as implants to be inserted
into specific regions of the brain, restoring or enhancing a patient's
mental functionality. Such goals represent the exceptional promise of
nanotechnology - where researchers from a diverse range of disciplines
work together to improve the basic quality of human life.
Reference
1. B.B. Mandelbrot, The Fractal Geometry of Nature, Freeman, San
Francisco (1982).
2. J.B. Bassingthwaite et al, Fractal Physiology, Oxford University
Press (1994).
3. S.A. Scott and S.A. Brown, Journal of European Physics 39 433
(2006).
4. M.G. Warner, and J.E. Hutchison, Nature Materials 2, 272 (2003).
Copyright AZoNano.com, Professor Richard Taylor (University of Oregon)
Date Added: Oct 1, 2009 |
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| Roger Bagula... |
| Posted: Sun Oct 04, 2009 1:28 pm |
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| Mok-Kong Shen... |
| Posted: Mon Oct 05, 2009 11:35 am |
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Roger Bagula wrote:
[quote:c47746f6c9]Fractals in Nano-Devices
[snip][/quote:c47746f6c9]
[quote:c47746f6c9]These projects are driven by the potential to tune the growth
conditions so that the fractal characteristics of the circuits match
those found for example in the neural structure of the human brain.
Imagine a future where computers operate like our own minds and,
ultimately, where fractal circuits may act as implants to be inserted
into specific regions of the brain, restoring or enhancing a patient's
mental functionality. Such goals represent the exceptional promise of
nanotechnology - where researchers from a diverse range of disciplines
work together to improve the basic quality of human life.
[/quote:c47746f6c9]
Such implantations might involve serious ethical questions. On the
other hand, doing that to some animals may be quite ok. Recently
I mentioned in another group of a chat I had with some colleagues
in the late nineteen sixties while sitting together near a then
for us astonishingly fast yet extremely costly computer. We came
up with a question concerning the 'principal' feasibility of a
project which is devoid of (or anyway almost so) any ethical
problems: Electrically connect the brains of a large number of
pigs to do computations. (You see we were babbling about networking
and even cloud computing in ultra-modern terminology!) We envisaged
pigs, because they are comparatively intelligent among animals
having large-sized brains and are quite cheap.
Thanks,
M. K. Shen |
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