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« Reader's-Eye View of Nanotechnology Economics | Main | Code of Conduct »

July 26, 2007

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Brian Wang

They still seem to be using DC current for the computer. But the current is controlled by a nanomechanical nanoscale pillar.

http://advancednano.blogspot.com/2007/07/nanomechanical-computer-project.html

The 9 page paper is here
http://www.iop.org/EJ/article/-search=25210907.1/1367-2630/9/7/241/njp7_7_241.pdf

It has to be clearly stated that current operating speeds of nano-electromechanical single electron transistors (NEMSETs) are of the order of 1 GHz [3], which is not competitive with standard complimentary metal oxide semiconductors (CMOS

As we have found in recent measurements [4] self-excitation can be exploited to generate
mechanical oscillations without any ac excitation. Hence, dc voltages are sufficient to operate the NMC. Basically, a dc voltage creates an electric field to support mechanical oscillations of the nanopillars. A classical example is straightforward to construct [5]. It has to be noted that onset of the mechanical oscillations is induced by a thermal fluctuation, which is found to be
enhanced, if the electrical field is inhomogeneous.


Ray Phoenix

From the paper:

"The scaling of the power of the nanomechanical circuits we find by applying the standard relation for CMOS dynamic power consumption P = CV2f . Assuming an operating frequency of f = 1 GHz, a typical operating voltage of V = 1 V and a NEMSET total capacitance of C = 10 aF, we find a total dynamic power of P = 10nW. This value can be further reduced by lowering the gating voltage to some 100mV and the overall capacitance to below 10 aF. Under the assumption that the gate is switched at a speed of 1 GHz the total power corresponds to an energy of E = 10 aJ per switching event for nanomechanical transistors. At this stage this is only two orders of magnitude above the thermal energy limit Eth = kBT for 300 K. A computing architecture made from nanomechanical transistors thus is competitive with 45 nm CMOS technology, while taking a step towards enabling reversible computing.

In summary, we have shown how to construct a computational device purely based on nanomechanical elements—the NMC. Single nanomechanical switches are operational and simulation shows that the concept is feasible for circuit integration."

10 attojoules, if I read correctly. That's good, I think. The authors point out that high temperature operation is a strong point. The technology has relatively low clock speed, which the authors acknowledge.

Clearly nothing slides, and the transistors should suffer absolutely no wear, so properly shielded from radiation, the device should last indefinitely.

Note the comment on reversible computing, as well.

Chris Phoenix, CRN

Yes, Drexler's and Merkle's computers were also designed for reversibility.

I wouldn't call this computer totally mechanical, since it transports electrons. The design is really not much at all like the mechanical nanocomputers proposed by MM researchers. In which case it's interesting that the news stories make it sound so similar in some respects.

Chris

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