...read the wave
Guest Writer - Gastautor - Gast Schrijver
www.nanoTsunami.com

 

Advantages of Engineered Nanosystems

 

 

Today, biology implements by far the most advanced nanomachines on the
planet. It is tempting to think that biology must be efficient, and that
we can't hope to design nanomachines with higher performance. But we
already know some techniques that biology has never been able to try.
This essay discusses several of them and explains why biology could not
use them, but manufactured nanomachines will be able to.

Low Friction Via Superlubricity

Imagine you're pulling a toy wagon with square wheels. Each time a wheel
turns past a corner, the wagon lurches forward with a thump. This would
waste substantial amounts of energy. It's as though you're continually
pulling the wagon up tiny hills, which it then falls off of. There's no
way to avoid the waste of energy.

At the molecular scale, static friction is like that. Forces between the
molecules cause them to stretch out of position, then snap into a new
configuration. The snap, or clunk, requires energy--which is immediately
dissipated as heat.

In order for a sliding interface to have low friction, there must be an
extremely small difference in energy between all adjacent positions or
configurations. But between most surfaces, that is not the case. The
molecular fragments at the surface are springy and adhesive enough that
they grab hold, get pulled, and then snap back, wasting energy.

There are several ways in which a molecule can be pulled or pushed out
of position. If the interface is rough or dirty, the surfaces can be
torn apart as they move. This of course takes a lot of energy, producing
very high friction. Even apparently smooth surfaces can be sources of
friction. If the surface is coated with molecular bumps, the bumps may
push each other sideways as they go past, and then spring back, wasting
energy. Even if the bumps are too short and stiff to be pushed sideways
very far, they can still interlock, like stacking egg cartons or ice
cube trays. (Thanks to [Wikipedia] for this analogy.) If the bumps
interlock strongly, then it may take a lot of force to move them past
each other--and just as they pass the halfway point, they will snap into
the next interlocking position, again wasting energy.
http://en.wikipedia.org/wiki/Superlubricity

One way to reduce this kind of friction is to separate the surfaces. A
film of water or oil can make surfaces quite slippery. But another way
to reduce friction is to use stiff surfaces that don't line up with each
other. Think back to the egg-carton image. If you turn one of the
cartons so that the bumps don't line up, then they can't interlock; they
will simply skim past each other. In fact, friction too low to measure
has been observed with graphite sheets that were turned so as to be out
of alignment. Another way to prevent alignment is to make the bumps have
different spacing, by choosing different materials with different atoms
on their surfaces.

This low-friction trick, called superlubricity, is difficult to achieve
in practice. Remember that the surfaces must be very smooth, so they can
slip past each other; and very stiff, so the bumps don't push each other
sideways and spring back; and the bumps must not line up, or they will
interlock. Biological molecules are not stiff enough to use the
superlubricity trick. Superlubricity may be counterintuitive to people
who are accustomed to the high friction of most hard dry surfaces. But
[experiments have shown] that superlubricity works. A variety of
materials that have been proposed for molecular manufacturing should be
stiff enough to take advantage of superlubricity.

http://www.physics.leidenuniv.nl/sections/cm/ip/group/PDF/Phys.rev.lett/2004/92(2004)12601.pdf

Electric Currents

The kind of electricity that we channel in wires is made up of vast
quantities of electrons moving through the wire. Electrons can be made
to move by a magnetic field, as in a generator, or by a chemical
reaction, as in a battery. Either way, the moving electrons can be sent
for long distances, and can do useful work along the way. Electricity is
extremely convenient and powerful, a foundation of modern technology.

With only a few exceptions like electric eels, biological organisms do
not use this kind of electricity. You may know that our nerve cells use
electricity. But instead of moving electrons, biology uses ions--the
“charged” atoms that remain when one or more electrons are removed. Ions
can move from place to place, and can do work just like electrons.
Bacteria use ions to power their flagella “tails.” Ions moving suddenly
through a nerve cell membrane cause a change that allows more ions,
further along the cell, to be able to move, creating a domino effect
that ripples from one end of the cell to the other.

Ions are convenient for cells to handle. An ion is much larger than an
electron, and is therefore easier to contain. But ions have to move
slowly, bumping through the water they are dissolved in. Over long
distances, electrons in a wire can deliver energy far more rapidly than
ions in a liquid. But wires require insulation.

It is perhaps not surprising that biology hasn't used electron currents.
At cellular scales, ions diffuse fast enough to do the job. And the same
membranes that keep chemicals properly in (or out of) the cell can also
keep ions contained where they can do useful work. But if we actually
had “nerves of steel,” we could react far more quickly than we do.

To use electron currents, all that's needed is a good conductor and a
good insulator. Carbon nanotubes can be both conductors and insulators,
depending on how they are constructed. Many organic molecules are
insulating, and some are conductive. There is a lot of potential for
molecular manufacturing to build useful circuits, both for signaling and
for power transmission.

Deterministic Machines

Cells have to reconfigure themselves constantly in response to changing
conditions. They are built out of individual molecules, loosely
associated. And the only connection between many of the molecular
systems is other molecules diffusing randomly through the cell's
interior. This means that the processes of the cell will happen
unpredictably, from molecules bumping into each other after a random
length of time. Such processes are not deterministic: there's no way to
know exactly when a reaction or process will happen. This lack of tight
connection between events makes the cell's processes more adaptable to
change, but more difficult to engineer.

Engineered nanosystems can be designed, and then built and used, without
needing to be reconfigured. That makes it easier to specify mechanical
or signal linkages to connect them and make them work in step, while a
constantly changing configuration would be difficult to accommodate. Of
course, no linkage is absolutely precise, but it will be possible to
ensure that, for example, an intermediate stage in a manufacturing
process always has its input ready at the time it begins a cycle. This
will make design quite a bit easier, since complex feedback loops will
not be required to keep everything running at the right relative speed.
This also makes it possible to use standard digital logic circuits.

Digital Logic

Digital logic is general-purpose and easy to engineer, which makes it
great for controlling almost any process. But it requires symbolic codes
and rapid, reliable computation. There is no way that the diffuse
statistical chemical signaling of biology could implement a high-speed
microprocessor (CPU). But rapid, lock-stepped signals make it easy.
Biology, of course, doesn't need digital logic, because it has complex
control loops. But complex things are very difficult to engineer. Using
digital logic instead of complexity will allow products to be designed
much more quickly.

Rapid Transport and Motion

Everything in a cell is flooded with water. This means that everything
that moves experiences high drag. If a nanomachine can be run dry, its
parts can move more efficiently and/or at higher speeds.

Things that move by diffusion are not exempt from drag: it takes as much
energy to make objects diffuse from point A to point B in a certain time
as it does to drag it there. Although diffusion seems to happen “by
itself,” to work as a transportation system it requires maintaining a
higher concentration of particles (e.g. molecules) at the source than at
the destination. This requires an input of work.

In a machine without solvent, diffusion can't work, so particles would
have to be transported mechanically. (In theory, certain small molecules
could be released into vacuum and bounce around to their destination,
but this has practical difficulties that probably would make it not
useful.) Mechanical transportation sounds inefficient, but in fact it
can be more efficient than diffusion. Because the particle is never
released, energy is not required to find and recapture it. Because
nothing has to move through fluid, frictional forces can be lower for
the same speed, or speeds can be higher for the same energy consumption.
The use of machinery to move nanoparticles and molecules may seem
wasteful, but it replaces the need to maintain a pathway of solvent
molecules; it may actually require less mass and volume. The increased
design complexity of the transport machinery will be more or less
balanced by the reduced design complexity of the receiving stations for
particles.

It is not only transport that can benefit from running without solvent.
Any motion will be subject to drag, which will be much higher in liquid
than in gas or vacuum. For slow motions, this is not so important. But
to obtain high power density and processing throughput, machines will
have to move quickly. Drying out the machines will allow greater
efficiency than biology can attain. Biology has never developed the
ability to work without water. Engineered machines can do so.

 

Chris has studied nanotechnology and molecular manufacturing for more than a decade. After successful careers in software engineering and dyslexia correction, Chris co-founded the Center for Responsible Nanotechnology in 2002, where he is Director of Research. Chris holds an MS in Computer Science from Stanford University.

Copyright © 2004 Chris Phoenix


The Center for Responsible Nanotechnology(TM) (CRN) is an affiliate of World Care(R), an international, non-profit, 501(c)3 organization. All donations to CRN are handled through World Care. The opinions expressed by CRN do not necessarily reflect those of World Care

 


Patric Salomon

 

 

Worldwide Services and Infrastructure
for Nano- and Microproduction

by Patric Salomon




& Henne van Heeren (NL)

 

NanoTsunami readers know that a large number of applications and markets could be served by products based on the various micro nano technologies (MNT). However, the variety of MNT manufacturing technologies also poses a threat to the commercial breakthrough of MNT. With so many technologies available, most of them not yet standardised, and non-availability of standard equipment for several of them, how can MNT become commercially successful?

In certain high-volume markets, such as automotive, computer peripherals, and communications, the advantages of MNT were able to overcome the problems that follow technological diversification. The authors believe that only a good infrastructure of design houses, foundries, package/assembly providers and equipment suppliers is able to satisfy the demand in design, prototyping, and (mass-) production in all the MNT fields. This infrastructure is needed to provide an efficient route to commercialisation.


Fig.1: Services and infrastructure needed for the commercialisation of MNT

 

Foundries and Design Houses play a major role in the supply chain. Foundries, provide the infrastructure to prototype, fabricate and mass-produce the designs emanating from the design houses and other companies. The reason for the customers to rely on foundries can be diverse: ranging from pure financial reasons (investment, cost-price) to technical (availability of required technology). The desire to have a second source of supply can also be a reason for outsourcing. A ‘fabless’ design house can generally be described as the catalyst that enables ideas or concepts to migrate towards commercialisation. In this context, the fabless design organisation manages the process of technology transfer from R&D to a production line.

Packaging suppliers are another, often not very visible, part of the infrastructure. Although the diversity in packaging and assembly for MST/MEMS is notably high, they can be classified into the following four generic groups:


• Standard available packaging and assembly technologies. Techniques, which can only be used in a limited number of cases, often hindered by the (mechanical) sensitivity of the product, the small dimensions or the special demands in the field of interconnections with the outer world.

• Specialised assembly, often with special technologies ensuring ultra precise positioning and/or very careful handling.

• Adapted standard packaging, where use is made of the cost effective and high quality processing capabilities established for the high-volume electronics industry. The main trend here is to use a die protecting method during plastic moulding. Closure for sealing the package is achieved afterwards. The lid can be used to accommodate feed troughs for optical or fluidics access.

• Waferscale package. This method promises a, potentially, low cost solution which circumvents problems associated with handling sensitive products in an assembly line, by providing protection at an early stage of the processing.

Supporting the professional infrastructure are the equipment and material suppliers. The emerging markets for MST/MEMS (Micro Systems Technologies / Micro-Electro-Mechanical Systems) products have created a demand for specialised equipment. The first to fulfil that demand were suppliers of dedicated MST/MEMS tools including Deep Reactive Ion Etchers (DRIE), waferbonders and backside aligners. Those companies (STS, Aldixen, AML, EV Group and Suss Microtec) are still in the forefront of this market. Spin-offs from universities were started to fulfil (niche) demands, whilst established companies entered this arena at a later stage, offering adapted processing tools developed for other industries, such as, those specialising in thin film processing. More interestingly, even the (large) semiconductor equipment manufacturers have begun to show an interest. Within this context, there is now available a mixture of general equipment facilities, designed and developed for other applications such as semiconductors and also equipment adapted or specially tailored for Micro-Nano Technologies (MNT) production. It is noticeable that, although Europe (particularly Germany) is relatively strong in the area of MNT Back End equipment, the presence of European manufacturers is less impressive in Front End equipment production and almost non-existent in the area of nanotechnology.


Fig.2: Suppliers of MNT production equipment

 

When nanotechnologies are taken into account to be used with microproduction, the manufacturing technologies become even more diverse. To investigate the market and distinguish trends, the authors categorised the production processes for nanotechnology-based products into four areas (Fig. 3):

• Top down nanotechnology: Top down nanotechnology is mainly based on processes and equipment for high-end lithography and similar equipment. Technologies and equipment are aiming at producing large quantities of products, mostly on flat substrates.
• Bottom up technologies: Bottom up technology involves the building up of nanotechnology products from atom level, by either mechanical manipulation (using Scanning Probe Microscopes) or with molecules assembling other molecules (Molecular Self Assembly).
• Nanoparticle production: In nanoparticle production extended traditional physical and chemical methods are utilised to create particles with smaller sizes and special properties.
• Nanotube production processes. Nanotubes are seen as a very promising material due to its unique properties.


Fig.3: Nanoproduction technologies

 

 

It should be noted that the top down and bottom up approach (except Molecular Self Assembly) are mostly equipment oriented. Molecular Self Assembly, nanoparticle and nanotube production are much more process oriented. Top-down and bottom-up nanotechnology equipment benefit from the equipment infrastructure for semiconductor lithography and deposition and the ample availability of Scanning Probe Microscopes. Most of the development of processes for the production of nanoparticles is done in-house. The equipment market for nanoparticle production is not well developed, although it benefits from knowledge from the chemical/physical process equipment market.

Conclusion

The use of MNT based products is growing in a number of application and markets, ranging from life science to telecommunications. Besides a few notable exceptions, the MNT market is still a sum of niche markets. There is a general consensus that the overall market will grow, but that commercialisation will take longer than was anticipated a few years ago.

Packaging still remains a bottleneck introduced, belatedly, at the end of the design cycle, and often delaying or even preventing industrialisation and commercialisation. It is well known that selecting the appropriate packaging method may be the decisive factor that determines a product’s success or its premature failure. Choosing the right technology, therefore, is not a marginal concern, but pivotal to the product design. The existence of professional suppliers of packaging and assembly is an essential element in the supply chain and critical for the manufacturing and commercialisation of MNT-based products. In addition, the incorporation of packaging and assembly techniques at the front-end of the engineering cycle will pay back in terms of financial savings and shorter timescales to market. Methodologies for a ‘design for micro nano manufacturing’ approach are under development.

Many companies working in the field of nanotechnology aim at the extension of semiconductor equipment to suit the market needs (the so-called “top down” approach). Also several companies are offering equipment based on chemical and physical processes for the production of small particles and nanotubes. The “bottom up” approach, aiming to build nanotechnology products practically atom by atom, is less prevalent. There is an ample supply of Scanning Probe Microscopy based tools, but such instruments are not yet able to combine nanotechnology precision with industrial volume demand. Processes for molecular self-assembly, which are potentially more suitable for economical mass production, are still in development and far from industrialisation.

The industry as a whole could benefit from exchange of information and consensus over process and product specifications and related equipment specifications. It is however unlikely that industry wide roadmaps will play a role similar to the one played for the semiconductor industry. This is due to the fact that there is no MNT equivalent to the transistor and it is not to be expected there will be one. It is more likely, however, that application roadmaps will extend their influence into the MNT arena. In essence, the customers and the end users will determinate the roadmap and not the (equipment) suppliers. This will undoubtedly lead to a more diverse set of processes, equipment and standards in MNT as compared to semiconductors. A situation that is likely to create a much wider range of opportunities for smaller (equipment and material) suppliers, as long as they are able to combine flexibility with quality and staying power. However this lack of commonly shared technology platforms is a serious threat to the realisation of reliable and low cost products.

In addition to the availability of a services infrastructure, the availability of a wide ranging, industry-based intelligence information is of vital importance in order to optimally select from this array of enabling capabilities. This array of information is provided through the enablingMNT Industry Review series: Design and Engineering Companies, Foundries, Packaging and Assembly Suppliers, Equipment Suppliers (MEMS Front-End, Back-End, Nanofabrication), MNT Web Directories / On-line Communication Channels, and Materials for MST/MEMS Production. Reports on Test and Measurement Services & Equipment and Design Tools are underway. All reviews cover worldwide activities and sell at € 280 each.

Customised research and consulting services offered by enablingMNT range from market research, business development support and partner search for industrial customers to benchmarking and exploitation strategy development for public bodies.

Contact:
Patric Salomon, Germany
Henne van Heeren, The Netherlands
E-mail: info@enablingMNT.com

Link : enablingMNT

 

Copyright © 2004 Patric Salomon

Chris Phoenix

CRN Director of Research

 

 
 


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