Category Archives: Nano

MIT’s progress in making synthetic spider silk

From this report [via slashdot]:

“If you look closely at the structure of spider silk, it is filled with a lot of very small crystals,” said Gareth McKinley, a professor of mechanical engineering and part of the group that devised the new method of producing the material.

“It’s highly reinforced.”

The secret of spider silk’s combined strength and flexibility, according to scientists, has to do with the arrangement of the nano-crystalline reinforcement of the silk as it is being produced—in other words, the way these tiny crystals are oriented towards (and adhere to) the stretchy protein.

Emulating this process in a synthetic polymer, the MIT team focused on reinforcing solutions of commercial rubbery substance known as polyurethane elastomer with nano-sized clay platelets instead of simply heating the mixing the molten plastics with reinforcing agents.

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Nano-knives and superplastic nanotubes

First, the nano-knife (via slashdot):

A prototype microtome knife for cutting ~100 nm thick slices of frozen-hydrated biological samples has been constructed using multiwalled carbon nanotubes (MWCNT). A piezoelectric-based 3-D manipulator was used inside a Scanning Electron Microscope (SEM) to select and position individual MWCNTs, which were subsequently welded in place using electron beam-induced deposition (EBID).

The device employs a pair of tungsten needles with provision to adjust the distance between the needle tips, accommodating various lengths of MWCNTs. We have performed experiments to test the breaking strength of the MWCNT in the completed device using an atomic force microscope (AFM) tip. An increasing force was applied at the midpoint of the nanotube till the point of failure, which was observed in-situ in the SEM.

Next, the superplastic nanotubes of carbon:

The theoretical maximum tensile strain — that is, elongation — of a single-walled carbon nanotube is almost 20%, but in practice only 6% is achieved. Here we show that, at high temperatures, individual single-walled carbon nanotubes can undergo superplastic deformation, becoming nearly 280% longer and 15 times narrower before breaking. This superplastic deformation is the result of the nucleation and motion of kinks in the structure, and could prove useful in helping to strengthen and toughen ceramics and other nanocomposites at high temperatures.

Nanotech research in India

[Even] with the NSTI [the Nano Science and Technology Initiative] in place, the level of funding has been sub-critical as compared to China with which India inevitably tends to be compared. In 2002, for example, compared to China’s $200 million, India spent a mere Rs.15 crores. Over the four and a half years of the NSTI, a total of about Rs.120 crores has been spent, much of which has gone towards basic research projects and related infrastructure, the implementation of which is overseen by a National Expert Committee headed by C.N.R. Rao. …

Besides funding about 100 basic science projects to date (worth about Rs.60 crores), part of the money (about Rs.20 crores) has gone towards establishing six centres for nanoscience at institutions such as the Indian Institute of Science (IISc), Bangalore, and the different IITs, six centres for nanotechnology each aimed at producing a product or a device within a reasonable time-frame and two national instrumentation/characterisation facilities. In all, 14 national institutions, including seven IITs, and 10 universities have been supported under the NSTI.

Pay no attention to the howler in that last sentence, and do read this Frontline article [Update: the link is broken; try this link] by R. Ramachandran on the state of nanoscience and nanotechnology research in India. [Thanks to Pradeepkumar for the e-mail alert.]

Nanosilver

Apparently, silver (particularly in the form of silver nitrate) was used as a disinfectant before the advent of antibiotics. Today’s NYTimes has an article about the return of silver — this time, in the nanometric, elemental form — to its well known medical use. It adds that this link between silver and its disinfectant properties is not fully understood.

Hype in science?

Let me give start with an example: I saw in nanotech wire this report. The headline screams:

Princeton’s Group Nanotechnology discovery by could have radical implications

Let’s look at the underlying paper that has led to this screaming headline: It is this paper (pdf),that was recently published in the journal Physical Review Letters (22, 228301, November 25, 2005). It actually has a much more sober title:

Optimized Interactions for Targeted Self-Assembly: Application to a Honeycomb Lattice

Read both the ‘nanotech wire’ report and the broad features in PRL paper, and compare the tone and tenor in them! Let me give you the last paragraph of the PRL paper:

The optimization scheme proposed here is only one approach to the inverse problem, and we expect that others will be needed to search for interactions (isotropic or not, additive or not) that stabilize general systems. Apart from any particular algorithm, however, a central point of this Letter is to propose the use of powerful inverse statistical mechanical techniques to exquisitely control self-assembly from the nanoscopic to microscopic scales.

And this is what ‘nanotech wire’ says:

Now Salvatore Torquato, a Princeton University scientist, is proposing turning a central concept of nanotechnology on its head. If the theory bears out � and it is in its infancy — it could have radical implications not just for industries like telecommunications and computers but also for our understanding of the nature of life.

In concluding that this work is terribly hyped up in ‘nanotech wire’, am I being clueless?

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